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Introduction: Yam is an important crop for food security in East and West Africa due to its high market value and customer demand. High tuber quality with yield and disease resistance are the main traits for acceptability of yam cultivars across the tropical zone. There has been limited progress in enhancing the production and quality traits of yams, despite the significant socio-economic significance of this crop. Method: To expedite the development of high-quality yam cultivars in Uganda, traits association study was conducted to identify genomic regions associated with key traits such as disease resistance, high yields, and dry matter content. The association mapping was conducted with multi-random mixed linear model (mrMLM) to compute the associations using five genetic models. Results: A total of 16 significant single nucleotide polymorphisms (SNPs) markers were identified to be associated with the traits studied. Gene identification analysis revealed the presence of key putative genes such as Vicilin-like seed storage protein At2g28490 (ARATH)and Growth-regulating factor 1 involved in a variety of functions ranging from storage and gene regulation for disease resistance. Discussion: The results obtained from this work have significant implications for the in-depth analysis of the genetic structure underlying key traits in yam. Additionally, this study emphasizes the identification of SNP variants and genes that may be utilized for genomic-informed selection in order to enhance yield and disease resistance in yams. [ABSTRACT FROM AUTHOR]

Introduction: Yam is an important crop for food security in East and West Africa due to its high market value and customer demand. High tuber quality with yield and disease resistance are the main traits for acceptability of yam cultivars across the tropical zone. There has been limited progress in enhancing the production and quality traits of yams, despite the significant socio-economic significance of this crop. Method: To expedite the development of high-quality yam cultivars in Uganda, traits association study was conducted to identify genomic regions associated with key traits such as disease resistance, high yields, and dry matter content. The association mapping was conducted with multi-random mixed linear model (mrMLM) to compute the associations using five genetic models. Results: A total of 16 significant single nucleotide polymorphisms (SNPs) markers were identified to be associated with the traits studied. Gene identification analysis revealed the presence of key putative genes such as Vicilin-like seed storage protein At2g28490 (ARATH)and Growth-regulating factor 1 involved in a variety of functions ranging from storage and gene regulation for disease resistance. Discussion: The results obtained from this work have significant implications for the in-depth analysis of the genetic structure underlying key traits in yam. Additionally, this study emphasizes the identification of SNP variants and genes that may be utilized for genomic-informed selection in order to enhance yield and disease resistance in yams. [ABSTRACT FROM AUTHOR]

The traditional crop calendar for yam (Dioscorea spp.) in South-Kivu, eastern Democratic Republic of Congo (DRC), is becoming increasingly inadequate given the significant climatic variability observed over the last three decades. This study aimed at: (i) assessing trends in weather data across time and space to ascertain climate change, and (ii) optimizing the yam crop calendar for various South-Kivu agro-ecological zones (AEZs) to adapt to the changing climate. The 1990–2022 weather data series were downloaded from the NASA-MERRA platform, bias correction was carried out using local weather stations' records, and analyses were performed using RClimDex 1.9. Local knowledge and CROPWAT 8.0 were used to define planting dates for yam in different AEZs. Results showed the existence of four AEZs in the South-Kivu province, with contrasting altitudes, temperatures, and rainfall patterns. Climate change is real in all these South-Kivu's AEZs, resulting either in rainfall deficits in some areas, or extreme rainfall events in others, with significant temperature increases across all AEZs. Suitable yam planting dates varied with AEZs, September 15th and 20th were recommended for the AEZ 2 while October 15th was optimal for AEZ 1, AEZ 3, and AEZ 4. However, none of the planting date scenarios could meet the yam water requirements in AEZ1, AEZ3, and AEZ4, since the effective rainfall (Pmm) was always inferior to the plant water demand (ETc), meaning that soil water conservation practices are needed for optimum plant growth and yield in these AEZs. This study does not recommend planting yam during the short rainy season owing to prolonged droughts coinciding with critical growth phases of yam, unless supplemental irrigation is envisaged. This study provided insights on the nature of climate change across the past three decades and suggested a yam crop calendar that suits the changing climate of eastern DRC. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) is a main staple tuber crop in Nigeria and the West African region. Its performance is determined by genotypes and also the environment of growth. This study assessed the agronomic performance and yield stability of elite white yam (Dioscorea rotundata) genotypes across diverse Nigerian environments. A total of 25 genotypes were evaluated at three locations in two consecutive growing seasons, 2022 and 2023, for fresh tuber yield, disease resistance, and tuber quality traits. The genotype's performance and stability for the measured traits were assessed using various analytical tools such as additive main effects and multiplicative interaction (AMMI) and multi-trait stability index (MTSI). The AMMI analysis revealed significant differences among the genotypes and across the environments for all traits (p < 0.001, p < 0.01). The PCA revealed that the first two principal components (PC1 and PC2) explained a substantial portion of the total variation (49.84%). The MTSI identified four clones: G18, G19, G24, and G16 as promising candidates for improved yam production in Nigeria with high and stable performance for the multiple traits. [ABSTRACT FROM AUTHOR]

Monitoring genetic gain is crucial to ensure breeding programs' effectiveness and identify potential challenges and areas for their improvement. Our study provides a first overview of the trends in genetic gain for tuber yield and disease resistance traits in the IITA's (International Institute of Tropical Agriculture) yam breeding program. We used historical data (2010–2022) from multiple generations of past breeding cycles evaluated at 31 sites in the white Guinea yam (Dioscorea rotundata Poir) breeding pipeline and 28 sites in the water yam (Dioscorea alata L.) breeding pipeline of IITA and its national partners in West Africa. Our result shows positive genetic trends in fresh tuber yield while recording a gain of 1.38% or 99.17 kg ha−1 per year in the white Guinea yam and 2.18% or 252.41 kg ha−1 per year in the water yam breeding pipelines. Genetic trends for virus and anthracnose resistance were in the desired direction but negligible in white Guinea yam, while significant for virus and nonsignificant for anthracnose resistance in water yam. Our findings indicate that while the breeding program has succeeded in enhancing tuber yield, post‐harvest tuber dry matter content and disease resistance (yam mosaic virus and anthracnose) did not follow a similar trend in the material being developed. This implies that the yam breeding program needs to strike a balance between various traits, ensuring that increased yield does not come at a cost to food quality or disease resistance. Our results highlight the importance of continually monitoring and assessing the performance of a breeding program and making informed decisions about which traits to focus on for future improvement. Core Ideas: Periodic monitoring of genetic gain is crucial to making informed decisions about which traits to focus on.Yam breeding program needs to strike a balance between various traits for ensuring sustained genetic gain.High‐quality historical trial data crucial for assessing genetic gain trends in breeding programs. [ABSTRACT FROM AUTHOR]

BACKGROUND: Assessment of the key preferred quality traits in pounded yam, a popularly consumed yam food product in West Africa, is often done through sensory evaluation. Such assessment is time‐consuming and results may be biased. Therefore, there is a need to develop objective, high‐throughput methods to predict the quality of consumer‐preferred traits in pounded yam. This study focused on how key quality traits in pounded yam proposed to yam breeders were determined, measured by biophysical and biochemical methods, in order to shorten the breeding selection cycle through adoption of these methods by breeders. RESULTS: Consumer tests and sensory quantitative descriptive analysis (QDA) validated that preferred priority quality traits in pounded yam were related to textural quality (smooth, stretchable, moldable, slightly sticky and moderately hard) and color (white, cream or light yellow). There were significant correlations between sensory textural quality attributes cohesiveness/moldability, hardness, and adhesiveness/stickiness, with textural quality measurements from instrumental texture profile analysis (TPA). Color measurement parameters (L*, a*, and b*) with chromameter agreed with that of sensory evaluation and can replace the sensory panel approach. The smoothness (R2 = 1.00), stickiness (R2 = 1.00), stretchability (R2 = 1.00), hardness (R2 = 0.99), and moldability (R2 = 0.53) of pounded yam samples can be predicted by the starch, amylose, and protein contents of yam tubers estimated by near‐infrared spectroscopy. CONCLUSION: TPA and Hunter colorimeter can be used as medium‐high throughput methods to evaluate the textural quality and color of pounded yam in place of the sensory panelists. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Food quality traits related to the genetics of yam influence the acceptability for its consumption. This study aimed at identifying genetic factors underlying sensory and textural quality attributes of boiled and pounded yam, the two dominant food products from white Guinea yam. RESULTS: A genome‐wide association study (GWAS) of a panel of 184 genotypes derived from five multi‐parent crosses population was conducted. The panel was phenotyped for the qualities of boiled and pounded yam using sensory quality and instrument‐based textural profile assays. The genotypes displayed significant variation for most of the attributes. Population differentiation and structure analysis using principal component analysis (PCA) and population structure‐based Bayesian information criteria revealed the presence of four well‐defined clusters. The GWAS results from a multi‐random mixed linear model with kinship and PCA used as covariate identified 13 single‐nucleotide polymorphic (SNP) markers significantly associated with the boiled and pounded yam food qualities. The associated SNP markers explained 7.51–13.04% of the total phenotypic variance with a limit of detection exceeding 4. CONCLUSION: Regions on chromosomes 7 and 15 were found to be associated with boiled and pounded yam quality attributes from sensory and instrument‐based assays. Gene annotation analysis for the regions of associated SNPs revealed co‐localization of several known putative genes involved in glucose export, hydrolysis and glycerol metabolism. Our study is one of the first reports of genetic factors underlying the boiled and pounded yam food quality to pave the way for marker‐assisted selection in white Guinea yam. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The 5‐year project 'Breeding roots, tubers and banana products for end user preferences' (RTBfoods) focused on collecting consumers' preferences on 12 food products to guide breeding programmes. It involved multidisciplinary teams from Africa, Latin America, and Europe. Diverse data types were generated on preferred qualities of users (farmers, family and entrepreneurial processors, traders or retailers, and consumers). Country‐based target product profiles were produced with a comprehensive market analysis, disaggregating gender's role and preferences, providing prioritised lists of traits for the development of new plant varieties. We describe the approach taken to create, in the roots, tubers, and banana breeding databases, a centralised and meaningful open access to sensory information on food products and genotypes. Biochemical, instrumental textural, and sensory analysis data are then directly connected to the specific plant record while user survey data, bearing personal information, were analysed, anonymised, and uploaded in a repository. Names and descriptions of food quality traits were added into the Crop Ontology for labelling data in the databases, along with the various methods of measurement used by the project. The development and application of standard operating procedures, data templates, and adapted trait ontologies improved the data quality and its format, enabling the linking of these to the plant material studied when uploaded in the breeding databases or in repositories. Some modifications to the database model were necessary to accommodate the food sensory traits and sensory panel trials. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

In Ethiopia, improved hive technology dissemination was started before five-decades. However, the adoption of improved beekeeping technology is still very low. This study was conducted with the main objectives to evaluating improved beekeeping adoption level and honey yields of different hives and identification of major honey bee plants and flora calendar in the Gedeo zone, South Ethiopia. Three districts were selected purposively based on beekeeping potential and the number of improved hives own by beekeepers. The data was collected from 180 respondents using cross-sectional survey. The data was analyzed by using descriptive statistics such as mean, frequency and percentage and ANOVA. The result shown that the compositions of disseminated hives in the entire sampled respondents were 286, 476, 121 and 1494 Zander hive, Kenyan top bar hive (KTBH), Mud/Ethio-Ribrab hive (ERH) and Traditional hives respectively. Traditional beekeeping was the dominant system with 63% and intermediate followed by 25%, while modern beekeeping was only 12%. Based on overall mean honey yield, there was no significant difference (P = 0.244) between Zander and KTBH. However, the average honey yield of these improved hives were significantly (P<0.05) higher than Mud/ERH and Traditional hives. Gedeo zone had rich floral resource and diverse floral calendar. Hygenia abyssinica, Bidens ghedoensis, Erythrinia abyssinica, Eucalyptus species, Cordia africana, Coffee arabica, Vernonia species, Susbania susban and Persea americana were major honey bee flora in Gedeo zone. February-March was major honey harvesting season while May-July and October-December respectively were minor honey harvesting periods. Nevertheless, the majority of beekeepers have been practicing honey harvesting once a year from all hives due to lack of awareness and practical skills. Therefore, we recommend that the local government should focus on educating beekeepers to enable them utilizing exhaustively the opportunities of multi-floral season and improved hive technology to maximize honey yield in the area. [ABSTRACT FROM AUTHOR]

An in-depth understanding of the extent and pattern of genetic diversity and population structure in crop populations is of paramount importance for any crop improvement program to efficiently promote the translation of genetic diversity into genetic gain. A reference collection of 150 common bean genotypes selected from the International Center for Tropical Agriculture's global core collection was evaluated using single-nucleotide polymorphism (SNP) markers to quantify the amount of genetic diversity, linkage disequilibrium, and population structure. The cultivars and landraces of the collection were diverse and originated from 14 countries, and wild accessions were used as controls for each gene pool. The collection was genotyped using an SNP array, generating a total of 5398 locus calls distributed across the entire bean genome. The SNP data quality was checked, and two datasets were generated. The first dataset (Dataset_1) comprised a set of 5108 SNPs and 150 genotypes after filtering for 10% missing alleles and an MAF < 0.05. The second dataset (Dataset_2) comprised a set of 2300 SNPs that remained after removing any null-allele SNPs and LD pruning for a criterion of r2 < 0.2. Dataset_1 was used for a principal coordinate analysis (PCoA), phylogenetic relationship determination, an analysis of molecular variance (AMOVA), and a discriminant analysis of principal components. Dataset_2 was used for a population structure analysis using STRUCTURE software and is proposed for a genome-wide association study (GWAS). The population structure analysis split the reference collection into two subpopulations according to an Andean or Mesoamerican gene pool. The Mesoamerican populations displayed higher genetic differentiation and tended to split into more groups that were somewhat aligned with common bean races. Andean beans were characterized by a larger average LD but lower LD percentage, a small average genetic distance between members of the population, and a higher major allele frequency, which suggested narrower genetic diversity compared to the Mesoamerican gene pool. In conclusion, the results indicated the presence of high genetic diversity, which is useful for a GWAS. However, the presence of significant linkage disequilibrium requires that genetic distance be considered as a co-factor for any further genetic studies. Overall, the molecular variation observed in the genotypes shows that this reference collection is valuable as a genebank-derived diversity panel which is useful for marker trait association studies. [ABSTRACT FROM AUTHOR]

Water yam (Dioscorea alata), also known as winged yam, is one of the most economically significant yam species, serving as a staple food crop in tropical and subtropical regions. Its widespread cultivation is due to its favorable agronomic characteristics, including high yield, improved tuber storability, and significant nutritional and health benefits. Despite these advantages, water yam often remains underutilized due to consumer biases towards its traditional food product quality, particularly for pounded yam preparations. In this study, we evaluated fifty-eight improved genotypes of water yams grown across three locations to assess their potential to produce superior food qualities comparable to the widely consumed white yams (D. rotundata). Seven white yams, including popular landraces, were used to set thresholds for desirable food quality. Through standardized analysis, yam samples were assessed for their biochemical composition and culinary and sensory texture attributes. The results revealed varying ranges of dry matter (DM), starch, sugar, protein, crude fiber (CF), fat, and amylose, spanning from 20.35 to 35.95 g/100 g, 42.81 to 83.31 g/100 g, 4.76 to 6.95 g/100 g, 4.33 to 6.62 g/100 g, 1.55 to 3.89 g/100 g, 0.32 to 0.53 g/100 g, and 29.27 to 38.52 g/100 g, respectively. The mean values (±SD) were found to be 29.85 ± 4.0 g/100 g (DM), 67.90 ± 44g/100 g (starch), 5.82 ± 0.64 g/100 g (sugar), 6.31 ± 1.31 g/100 g (protein), 2.14 ± 0.57 g/100 g (crude fiber), 0.44 ± 0.08 (fat), and 33 ± 16.43 g/100 g (amylose). Significant effects (p < 0.001) of the planting environments and genotypes on the biochemical composition of the yam samples were observed, except for the sugar content. Furthermore, specific water yam genotypes, such as TDa 0900354, TDa 9801174, TDa 1401619, TDa 1400301, TDa 140091, TDa 0100029, TDa 1100793, TDa 1401249, TDa 1100242, and TDa 1401276, exhibited biochemical properties and culinary and sensory textural attributes akin to the improved white yam genotypes and their landrace counterparts. These findings underscore the potential for promoting selected water yam genotypes to diversify food options and reduce reliance on a limited array of crops, particularly in traditional food-insecure regions of tropical Africa. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) is a key tuber crop in sub-Saharan Africa (SSA) with huge potential for poverty alleviation, food sovereignty, and nutrition security. Exploiting its full potential requires that factors holding it down are understood and mitigated. This study, conducted between May and July 2022 and 2023, assessed yam farming practices, varietal preferences, and land suitability in the Eastern Democratic Republic of Congo (DRC). We interviewed 765 smallholder farmers within four agro-ecological zones (AEZ) to assess the sociocultural, agronomic, varietal, and biophysical factors affecting yam production. Land suitability analyses were conducted using the Analytic Hierarchy Process (AHP) to identify areas suitable to extensive yam production and to cluster environments that could optimize yam varietal selection and testing. Results showed that yam is mainly cultivated by women in eastern DRC (70%). The seed delivery system is informal, relying primarily on farmer-saved seeds and farmer-seed exchanges (74.9%). Soil depletion (68.3%), limited access to high-quality seeds (54.5%), youth disengagement in yam value chain (50.3%), insect pests (17.9%), and short tuber shelf-life (65.8%) were, respectively, the main ecological, agronomic, sociocultural, biological, and tuber quality factors hindering yam production in eastern DRC. However, the perceived importance of most factors significantly varied with farmer gender and age categories. A multitude of varietal traits was used to assess yam varieties in eastern DRC, of which the tuber taste (59%) was the most valued trait regardless of gender and age categories, though it had highest scores among middle-aged adult women. Land suitability analyses discriminated five clusters; the most significant part of the region falling under suitable (27%), highly suitable (24%), and very highly suitable classes (37%). We further discussed how breeding initiatives for delivering yam varieties, suiting local producers' and end-users' needs, could unlock the crop's potential for enhancing food security and wealth creation in eastern DRC. The land suitability map from this study is a valuable decision-making tool in defining priority areas for extensive yam production and varietal selection and testing. This study provided valuable insights on factors affecting yam production and suggested yam breeding as a backbone of a holistic approach seeking to address challenges faced in unlocking the potential for yam production in eastern DRC. [ABSTRACT FROM AUTHOR]

This study assessed mineral fertilisation impact on tuber yield and food quality in yam genotypes—Dioscorea alata and Dioscorea rotundata. Four genotypes, each from D. alata and D. rotundata, were used in field experiments conducted in Ibadan, Nigeria, during the 2017 and 2018 cropping seasons. Experiments were conducted under low soil NPK fertility conditions with and without Fertiliser treatments. Plots subjected to fertiliser treatment received recommended NPK rate for the area. Tuber yield, functional and pasting properties of yam flour, and sensory attributes of pounded yams were collected. The results revealed varying responses of the genotypes to tuber yield and food quality following fertiliser application. Fertiliser application has generally increased fresh tuber yield. However, it had an impact on the flour quality and textural attributes of pounded yams for some genotypes. In genotypes Danacha and TDa0200012, Fertiliser application increased fresh tuber weight by 29.6% and 28.3%, and dry tuber weight by 19.7% and 24.9%, respectively, without compromising tuber quality. This implies that both genotypes exhibited a greater capacity for nutrient uptake and nutrient use efficiency. However, for genotype Ojuiyawo, Fertiliser application effectively increased tuber yield but negatively affected tuber quality. Our results emphasize the importance of assessing the impact of fertilization on tuber yield and quality for each genotype and selecting the appropriate genotype to improve productivity through mineral fertilization. The outcomes of this study have broader applicability in improving yam productivity across sub-Saharan Africa and are useful for sustainable agriculture in yam-growing regions. [ABSTRACT FROM AUTHOR]

Developing novel white Guinea yam (Dioscorea rotundata) varieties is constrained by the sparse, erratic, and irregular flowering behavior of most genotypes. We tested the effectiveness of nine agronomic and hormonal treatments to enhance flowering on D. rotundata under field conditions. Genotypes responded differently to flower-inducing treatments (p<0.001). Of the test treatments, pruning and silver thiosulfate (STS) were effective in increasing the number of spikes per plant and the flowering intensity on both sparse flowering and monoecious cultivars. STS and tuber removal treatments promoted female flowers on the monoecious variety while pruning and most treatments involving pruning favored male flowers. None of the treatments induced flowering on Danacha, a non-flowering yam landrace. Flowerenhancing treatments had no significant effect on flower fertility translated by the fruit set, since most treatments recorded fruit sets above the species' average crossability rate. Flower-enhancing techniques significantly influenced number of tubers per plant (p = 0.024) and tuber dry matter content (DMC, p = 0.0018) but did not significantly affect plant tuber yield. Nevertheless, treatments that could enhance substantially flowering intensity, such as pruning and STS, reduced tuber yield. DMC had negative associations with all flowering-related traits. This study provided insights into white yam flower induction and suggests promising treatments that can be optimized and used routinely to increase flowering in yam crop, without significantly affecting flower fertility and tuber yield. [ABSTRACT FROM AUTHOR]

Genetic variation in wild relatives, GenBank accessions, landraces, and cultivars can unlock key alleles for the traits of interest for breeding programs. Breeding programs often utilize different strategies to quantify the source of heritable variation for target traits. One neglected area of study is the root traits of diverse genotypes, and this is especially the case for aluminum toxicity effects on legumes such as the common bean, which is the most used pulse for direct human consumption. This study evaluated 267 genotypes of common bean that were part of the global Andean Diversity Panel (ADP), consisting mainly of genotypes assembled from public and private breeding programs in Africa and North America, as well as elite lines and land races from the USDA. The ADP was evaluated for root traits at the seedling stage in the Tennessee State University (TSU) greenhouse using a hydroponic system with a standard nutrient solution with and without aluminum (Al). The recorded data on the roots per trial were fit to a linear mixed model for the analysis of variance in order to test for the genotype differences. Adjusted means considered replication and blocks within replication as random effects and genotypes as fixed effects. These were then used for Pearson correlation tests and for principal component analysis (PCA), where the first two vectors accounted for 94.5% and 93% of the explained variation under the control and Al-treatment conditions, respectively. Genotypes were clustered based on the morphology of roots in response to Al-toxicity treatment using the Euclidean distance and Ward's hierarchical agglomerative clustering method, identifying four distinctive groups significant at p < 0.01. The intra-cluster distance was lower than the inter-cluster distances, which indicated a heterogeneous and homogeneous nature between and within clusters, respectively. The results suggest that crossing between accessions from two of the clusters would result in the maximum genetic segregation. One cluster was found to have a higher Al-toxicity tolerance than the others. [ABSTRACT FROM AUTHOR]

Introduction: Landraces represent a significant gene pool of African cultivated white Guinea yam diversity. They could, therefore, serve as a potential donor of important traits such as resilience to stresses as well as food quality attributes that may be useful in modern yam breeding. This study assessed the pattern of genetic variability, quantitative trait loci (QTLs), alleles, and genetic merits of landraces, which could be exploited in breeding for more sustainable yam production in Africa. Methods: A total of 86 white Guinea yam landraces representing the popular landraces in Nigeria alongside 16 elite clones were used for this study. The yam landraces were genotyped using 4,819 DArTseq SNP markers and profiled using key productivity and food quality traits. Results and discussion: Genetic population structure through admixture and hierarchical clustering methods revealed the presence of three major genetic groups. Genome-wide association scan identified thirteen SNP markers associated with five key traits, suggesting that landraces constitute a source of valuable genes for productivity and food quality traits. Further dissection of their genetic merits in yam breeding using the Genomic Prediction of Cross Performance (GPCP) allowed identifying several landraces with high crossing merit for multiple traits. Thirteen landraces were identified as potential genitors to develop segregating progenies to improve multiple traits simultaneously for desired gains in yam breeding. Results of this study provide valuable insights into the patterns and the merits of local genetic diversity which can be utilized for identifying desirable genes and alleles of interest in yam breeding for Africa. [ABSTRACT FROM AUTHOR]

Choosing superior parents with complementary trait values for hybridization and selecting variants with desired product profiles to release as a new cultivar are important breeding activities to progress genetic improvement in crops. This study assessed the genetic potential of 36 parental lines of white Guinea yam (Dioscorea rotundata) genotypes using multi-trait index-based factor analysis and ideotype design (FAI-BLUP). The experiment utilized 36 white yam genotypes laid out in a 6 × 6 triple lattice design with three replications and phenotyped for 18 agronomic and food quality traits. Findings showed significant differences among genotypes for all assessed traits. Fifteen traits had desired genetic gains, whereas stem diameter (−1.34%), and two starch property traits ((holding strength (−26.31%) and final paste viscosity (−3.33%)) had undesired selection gain. The FAI-BLUP index provided total genetic gains of 148.91% for traits desired for increase and –29.26% for those desired for decrease. Genotypes TDr08-21-2, TDr9518544, TDr9501932, TDr8902665 and Pampars were identified as top best candidate for simultaneous improvement of the measured traits in white yam breeding. The findings indicate the effectiveness of the FAI-BLUP index in identifying and selecting genotypes. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) is of great importance to food security, especially in West Africa. However, the loss of soil fertility due to dwindling fallow lands with indigenous nutrient supply poses a challenge for yam cultivation. This study aimed to determine shoot and tuber biomass and nutrient use efficiency of white Guinea yam (Dioscorea rotundata) grown under low- and high-NPK conditions. Six white Guinea yam genotypes were used in field experiments conducted at Ibadan, Nigeria. Experiments were conducted with low soil NPK conditions with zero fertilizer input and high soil NPK conditions with mineral fertilizer input. Differences in response to soil NPK conditions, nutrient uptake, and nutrient use efficiency (apparent nutrient recovery efficiency) were observed among the tested genotypes. The genotypes TDr1499 and TDr1649, with high soil fertility susceptibility index (SFSI>1) and an increase in shoot and tuber biomass with fertilizer input, were recognized as susceptible to soil NPK conditions. There was a marked difference in apparent nutrient recovery efficiency; however, there was no varietal difference in physiological efficiency. Differences in apparent nutrient recovery efficiency among genotypes affected the fertilizer response (or susceptibility to soil NPK conditions) and the nutrient uptake. In contrast, the genotype TDr2029, with SFSI<1 and low reduction in shoot and tuber production between non-F and +F conditions, was recognized as a less susceptible genotype to soil NPK status. It was revealed that NPK fertilization did not reduce tuber dry matter content, regardless of genotype differences in susceptibility to soil NPK conditions. Hence, this could be helpful to farmers because it implies that yield can be increased without reducing tuber quality through a balanced application of soil nutrients. Our results highlight genotypic variation in sensitivity to the soil NPK availability, nutrient uptake, and nutrient use efficiency white Guinea yam. Differences in susceptibility to soil NPK conditions could be due to the genotypic variations in nutrient recovery efficiency white Guinea yam. Our findings could contribute to breeding programs for the development of improved white Guinea yam varieties that enhance productivity in low soil fertility conditions with low and high-input farming systems. [ABSTRACT FROM AUTHOR]

Hand pollination success rate is low in yam (Dioscorea spp.), due partly to suboptimal weather conditions. Thus, determining the most suitable time for pollination could improve the pollination success in yam breeding programs. We performed continuous hand pollination within flowering windows of D. rotundata and D. alata for two consecutive years to determine the most appropriate month, week, and hours of the day allowing maximum pollination success. In D. alata crossing block, we observed significant differences among crossing hours for pollination success (p = 0.003); morning hours (8–12 a.m.) being more conducive than afternoons (12–5 p.m.). No significant differences existed between crossing hours in D. rotundata, though the mid-day seemed optimal. For both species, the time interval 11–12 a.m. was more appropriate for crossing while 4–5 p.m. was the poorest. However, in vitro pollen germination tests showed that mid-day pollen collection (12 noon–2 p.m.) had better results than both extremes, though there were strong genotypic effects on outcomes. Pollination success rates differed significantly among months for D. alata (p < 0.001) but not for D. rotundata (p > 0.05). Differences in pollination success existed across weeks within flowering windows of both D. alata (p < 0.001) and D. rotundata (p = 0.004). The seed production efficiency (SPE) had a similar trend as the pollination success rate. No clear pattern existed between the pollination time and the seed setting rate (SSR) or seed viability (SV), though their dynamics varied with weeks and months. This study provided an insight on the dynamics of pollination outcomes under the influence of pollination times and allows detecting months, weeks, and hours of the day when hybridization activities should be focused for better results. [ABSTRACT FROM AUTHOR]

Background: White Guinea yam (Dioscorea rotundata) is primarily a dioecious species with distinct male and female plants. Its breeding is constrained by sexual reproduction abnormalities, resulting in low success rates in cross-pollination. An accurate method for early detection of this plant's sex and compatible fertile parents at the seedling stage would improve levels of cross-pollination success in breeding. We used the genome-wide association studies (GWAS) to dissect the molecular basis of plant sex and cross-compatibility-related traits in a panel of 112 parental clones used in D. rotundata crossing blocks from 2010 to 2020. Results: Population structure and phylogeny analyses using 8326 single nucleotide polymorphism (SNP) markers grouped the 112 white yam clones into three subpopulations. Using Multi-locus random-SNP-effect Mixed Linear Model, we identified three, one, and three SNP markers that were significantly associated with the average crossability rate (ACR), the percentage of high crossability (PHC), and the plant sex, respectively. In addition, five genes considered to be directly linked to sexual reproduction or regulating the balance of sex hormones were annotated from chromosomal regions controlling the assessed traits. This study confirmed the female heterogametic sex determination (ZZ/ZW) system proposed for D. rotundata. Conclusions: This study provides valuable insights on the genomic control of sex identity and cross-pollination success in D. rotundata. It, therefore, opens an avenue for developing molecular markers for predicting plant sex and cross-pollination success at the early growth stage before field sex expression in this crop. [ABSTRACT FROM AUTHOR]

White Guinea yam (Dioscorea rotundata) is mainly a dioecious tuberous crop that produces flowers of varying sex phenotypes. Agronomic traits in Guinea yam differ according to the sex phenotype, but the precise interaction between the traits and sex phenotype is not clearly understood. This might be due to the high heterozygosity of yam where cultivars with different flowering sex have different genetic backgrounds, which mask the sole effect of sex phenotype on the agronomic traits. This study used F1-derived clonal progenies from a bi-parental cross to minimize the impact of different genetic backgrounds among the plants with different sex phenotypes. The impact of plant sex on agronomic traits, specifically tuber yield, was evaluated through field trials conducted for four years. The results showed that only plants with a female genotype exhibited varying sex phenotypes even within the clones of same accession grown in the same experimental field. The significant effects of sex genotype and phenotype on agronomic traits were detected. Our results revealed that the flowering date was delayed in the plants with female genotypes compared to male genotypes, even when compared only among the plants with male phenotypes. The flowering date is the most important reason for the sexual differences in tuber yield. A high tuber yield was obtained when plants with the female phenotype flowered before tuber enlargement. This result can be attributed to the fact that the low flowering intensity in female plants increases the availability of carbon resources for leaf development. Female plants also showed a large negative effect of late flowering on tuber yield owing to resource competition between flowering and tuber enlargement. These findings demonstrate the feasibility of yield improvement by controlling the flowering time, with a higher effectiveness achieved in female than in male plants. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) is a staple crop for millions of people in the tropics and subtropics. Its genetic improvement through breeding is being challenged by pre-zygotic and post-zygotic cross-compatibility barriers within and among species. Studies dissecting hybridization barriers on yam for improving the crossability rates are limited. This study aimed to assess the cross-compatibility, which yielded fruit set, viable seeds and progeny plants in an extensive intraspecific and interspecific crossing combinations in a yam genetic improvement effort to understand the internal and exogenous factors influencing pollination success. Cross-compatability was analyzed at the individual genotype or family level using historical data from crossing blocks and seedling nurseries from 2010 to 2020 at the International Institute of Tropical Agriculture (IITA). The average crossability rate (ACR) was lower in interspecific crossing combinations (6.1%) than intraspecific ones (27.6%). The seed production efficiency (SPE) values were 1.1 and 9.3% for interspecific and intraspecific crosses, respectively. Weather conditions and pollinator's skills are the main contributors to the low success rate in the intraspecific cross combinations in yam breeding. At the same time, genetic distance and heterozygosity played little role. Interspecific cross barriers were both pre-zygotic and post-zygotic, resulting from the evolutionary divergence among the yam species. Dioscorea rotundata had higher interspecific cross-compatibility indices than D. alata. Distant parents produced intraspecific crossbred seeds with higher germination rates compared to closest parents (r = 0.21, p = 0.033). This work provided important insights into interspecific and intraspecific cross-compatibility in yam and suggested actions for improving hybridization practices in yam breeding programs. [ABSTRACT FROM AUTHOR]

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Yam is an important food and cash crop in Nigeria. The seed system is mostly farmer-based and its challenges and opportunities are not well documented. This study reports results of surveys, interviews, focus group discussions and participant observations that describe local practices characterizing yam cultivation and the farmer-based seed system in five states in Nigeria. Our findings show that ware and seed yam are dynamic and highly commercialized goods in Nigeria. There is a high demand for, and a high turn-over of, seed yam. The reasons for the high demand are the low multiplication rate and degeneration of seed yam which lead farmers to frequently acquire fresh seeds and replace varieties, investing significantly in the seed of ware yam. The study found some farmers specializing in seed yam production but less than expected for such a highly commercial crop. The market is the major source for off-farm sourced seed yam, and although completely informal, the seed yam sector is vibrant and well organized. The identification of strategically positioned farmers and traders can offer opportunities and entry points for introduction of new varieties and improved seed production techniques. Building on the existing farmer-based system is a more logical strategy than replacing it with formal structures and legislative regulation. [ABSTRACT FROM AUTHOR]

Background: Improvement of tuber yield and tolerance to viruses are priority objectives in white Guinea yam breeding programs. However, phenotypic selection for these traits is quite challenging due to phenotypic plasticity and cumbersome screening of phenotypic-induced variations. This study assessed quantitative trait nucleotides (QTNs) and the underlying candidate genes related to tuber yield per plant (TYP) and yam mosaic virus (YMV) tolerance in a panel of 406 white Guinea yam (Dioscorea rotundata) breeding lines using a genome-wide association study (GWAS). Results: Population structure analysis using 5,581 SNPs differentiated the 406 genotypes into seven distinct sub-groups based delta K. Marker-trait association (MTA) analysis using the multi-locus linear model (mrMLM) identified seventeen QTN regions significant for TYP and five for YMV with various effects. The seveteen QTNs were detected on nine chromosomes, while the five QTNs were identified on five chromosomes. We identified variants responsible for predicting higher yield and low virus severity scores in the breeding panel through the marker-effect prediction. Gene annotation for the significant SNP loci identified several essential putative genes associated with the growth and development of tuber yield and those that code for tolerance to mosaic virus. Conclusion: Application of different multi-locus models of GWAS identified 22 QTNs. Our results provide valuable insight for marker validation and deployment for tuber yield and mosaic virus tolerance in white yam breeding. The information on SNP variants and genes from the present study would fast-track the application of genomics-informed selection decisions in breeding white Guinea yam for rapid introgression of the targeted traits through markers validation. [ABSTRACT FROM AUTHOR]

White Guinea yam (Dioscorea rotundata Poir.) is an important tuber crop grown extensively in tropical regions of West African yam belt. Tuber yield, dry matter content, and tolerance to yam mosaic virus are key traits used for identification and selection of superior varieties for commercial deployment. In this study, we estimated genetic parameters for fresh tuber yield, tuber dry matter content, and quantitative field tolerance to yam mosaic virus in 49 clones grown in multi-environment trials (METs). We conducted genomic prediction involving 6337 single nucleotide polymorphisms (SNPs) and phenotypic field evaluation of data collected on the three traits from four sites. Additive genetic and non-genetic factors contributed significantly to phenotypic variation of studied yam traits in METs but to varying degrees. The non-genetic effects were relatively high for most of the measured traits. Narrow-sense heritability values were low (<0.30) for all studied traits. Further analysis of the performance of the clones at test sites with additive main effects and multiplicative interaction (AMMI) analysis exhibited significant genotype by environment interactions (GEI) for the three traits. The AMMI identified TDr10/00412, TDr11/00055, and TDr09/00135 clones with lowest mean trait stability index and outstanding performance for fresh tuber yield (t ha−1), tuber dry matter, and mosaic virus resistance across sites. The elite clones identified could serve as useful source of alleles for the genetic improvement of the crop and possibly considered for release to farmers. [ABSTRACT FROM AUTHOR]

White Guinea yam (Dioscorea rotundata Poir.) is indigenous to West Africa, a region that harbours the crop's tremendous landrace diversity. The knowledge and understanding of local cultivars' genetic diversity are essential for properly managing genetic resources, conservation, sustainable use and their improvement through breeding. This study aimed to dissect phenotypic and molecular diversity of white yam cultivars from Benin using agro-morphological and single nucleotide polymorphism (SNP) markers. Eighty-eight Beninese white Guinea yam cultivars collected through a countrywide ethnobotanical survey were phenotyped with 53 traits and genotyped with 9725 DArT-SNP. Multivariate analysis using phenotypic traits revealed 30 traits as most discriminative and explained up to 80.78% of cultivars' phenotypic variation. Assessment of diversity indices such as Shannon–Wiener (H′), inverse Shannon (H.B.), Simpson's (λ) index and Pilou evenness (J) based molecular and phenotypic data depicted a moderate genetic diversity in Beninese white Guinea yam cultivars. Genetic differentiation of cultivars among country production zones was low due to the high exchange of planting materials among farmers of different regions. However, there was high genetic diversity within regions. Hierarchical clusters (HCs) on phenotypic data revealed the presence of two groups while HCs based on the SNP markers and the combined analysis identified three genetic groups. Our result provided valuable insights into the Beninese white Guinea yam diversity for its proper conservation and improvement through breeding. [ABSTRACT FROM AUTHOR]

Better understanding of the genetic control of traits in breeding populations is crucial for the selection of superior varieties and parents. This study aimed to assess genetic parameters and breeding values for six essential traits in a white Guinea yam (Dioscorea rotundata Poir.) breeding population. For this, pedigree‐based best linear unbiased prediction (P‐BLUP) was used. The results revealed significant nonadditive genetic variances and medium to high (.45–.79) broad‐sense heritability estimates for the traits studied. The pattern of associations among the genetic values of the traits suggests that selection based on a multiple‐trait selection index has potential for identifying superior breeding lines. Parental breeding values predicted using progeny performance identified 13 clones with high genetic potential for simultaneous improvement of the measured traits in the yam breeding program. Subsets of progeny were identified for intermating or further variety testing based on additive genetic and total genetic values. Selection of the top 5% progenies based on the multi‐trait index revealed positive genetic gains for fresh tuber yield (t ha−1), tuber yield (kg plant−1), and average tuber weight (kg). However, genetic gain was negative for tuber dry matter content and Yam mosaic virus resistance in comparison with standard varieties. Our results show the relevance of P‐BLUP for the selection of superior parental clones and progenies with higher breeding values for interbreeding and higher genotypic value for variety development in yam. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) is a major food security crop for millions of resource-poor farmers, particularly in West Africa. Soil mineral deficiency is the main challenge in yam production, especially with the dwindling of fallow lands for the indigenous nutrient supply. Cultivars tolerant to available low soil nutrients and responsive to added nutrient supply are viable components of an integrated soil fertility management strategy for sustainable and productive yam farming systems in West Africa. This study's objective was to identify white Guinea yam (D. rotundata) genotypes adapted to available low soil nutrients and responsive to externally added nutrient supply. Twenty advanced breeding lines and a local variety (Amula) were evaluated under contrasting soil fertility, low to expose the crop to available low soil nutrient supply and high to assess the crop response to added mineral fertilizer (NPK) input at Ibadan, Nigeria. The genotypes expressed differential yield response to low soil fertility (LF) stress and added fertilizer input. Soil fertility susceptibility index (SFSI) ranged from 0.64 to 1.34 for tuber yield and 0.60 to 1.30 for shoot dry weight. The genotypes R034, R041, R050, R052, R060, R100, and R125 combined lower SFSI with a low rate of reduction in tuber yield were identified as tolerant to LF stress related to the soil mineral deficiency. Likewise, the genotypes R109, R119, and R131 showed high susceptibility to soil fertility level and/or fertilizer response. Genotypes R025 and R034 had the tuber yielding potential twice of that the local variety under low soil nutrient conditions. Shoot dry weight and tuber yield showed a positive correlation both under low and high soil fertility conditions (r = 0.69 and 0.75, respectively), indicating the vigor biomass may be a morphological marker for selecting genotypes of white Guinea yam for higher tuber yield. Our results highlight genotypic variation in the tolerance to low soil nutrients and mineral fertilizer response in white Guinea yam to exploit through breeding and genetic studies to develop improved genotypes for low and high input production systems in West Africa. [ABSTRACT FROM AUTHOR]

Featured application: The acceptability and consumption of yam varieties depend on the quality components. Rapid measurement of these components is crucial in yam breeding program and calls for the rapid techniques for yam quality determination. The NIRS application will be beneficial for detecting tuber quality attributes in the yam crop due to its rapid, cost-effective, and non-destructive features. Sample preparation is a prerequisite for the prediction of quality traits by NIRS and sometimes is a big challenge when large populations of breeding materials are to be evaluated. Thus, this study evaluated the effects of different sampling methods on the prediction performances of NIRS in determining selected quality characteristics of different fresh yam species. High throughput techniques for phenotyping quality traits in root and tuber crops are useful in breeding programs where thousands of genotypes are screened at the early stages. This study assessed the effects of sample preparation on the prediction accuracies of dry matter, protein, and starch content in fresh yam using Near-Infrared Reflectance Spectroscopy (NIRS). Fresh tubers of Dioscorearotundata (D. rotundata) and Dioscoreaalata (D. alata) were prepared using different sampling techniques—blending, chopping, and grating. Spectra of each sample and reference data were used to develop calibration models using Modified Partial Least Square (MPLS). The performance of the model developed from the blended yam samples was tested using a new set of yam samples (N = 50) by comparing their wet laboratory results with the predicted values from NIRS. Blended samples had the highest coefficient of prediction (R2pre) for dry matter (0.95) and starch (0.83), though very low for protein (0.26), while grated samples had the lowest R2pre of 0.87 for dry matter and 0.50 for starch. Results showed that blended samples gave a better prediction compared with other methods. The feasibility of NIRS for the prediction of dry matter and starch content in fresh yam was highlighted. [ABSTRACT FROM AUTHOR]

Understanding the diversity and genetic relationships among and within crop germplasm is invaluable for genetic improvement. This study assessed genetic diversity in a panel of 173 D. rotundata accessions using joint analysis for 23 morphological traits and 136,429 SNP markers from the whole-genome resequencing platform. Various diversity matrices and clustering methods were evaluated for a comprehensive characterization of genetic diversity in white Guinea yam from West Africa at phenotypic and molecular levels. The translation of the different diversity matrices from the phenotypic and genomic information into distinct groups varied with the hierarchal clustering methods used. Gower distance matrix based on phenotypic data and identity by state (IBS) distance matrix based on SNP data with the UPGMA clustering method found the best fit to dissect the genetic relationship in current set materials. However, the grouping pattern was inconsistent (r = − 0.05) between the morphological and molecular distance matrices due to the non-overlapping information between the two data types. Joint analysis for the phenotypic and molecular information maximized a comprehensive estimate of the actual diversity in the evaluated materials. The results from our study provide valuable insights for measuring quantitative genetic variability for breeding and genetic studies in yam and other root and tuber crops. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) is an important tuber crop with tremendous potential as a functional food in the tropics and subtropics. However, the crop has not shown progressive productivity gain over decades due to various production constraints. This paper reviews the progress achieved in empirical breeding endeavours and the development, status and application of emerging breeding tools and technologies to translate genetic gains in yam improvement. Significant progress has been made in yam genetic improvement over the years which has led to the identification and development of several improved clones and sources of variability for various economically important traits. Substantial efforts have also been made to develop diverse molecular markers, transcriptome and metabolome profiles of crucial traits, trait mapping and generate reference genome sequences of the key species. However, there seems to be a slow translation of research improvements into widespread applications. These advances and the integration of empirical and emerging methods and technologies into the breeding process will enhance yam breeding efforts and ensure the quick delivery of improved varieties that possess superior agronomic and quality traits. [ABSTRACT FROM AUTHOR]

Though breeding for drought resistance is complicated due to the many processes involved and their interaction with the environment, availability of precise, cheap and easy to apply selection tool is critical. The present study quantified the response of potato genotypes to drought and identified potential morpho-physiological traits that are useful for selection of drought tolerant genotypes. The study assessed sixty genotypes under two irrigation regimes: fully watered non-stress and terminal drought, where the irrigation water supply to the crop was withheld after 50 % flowering to induce post-flowering stress. Measurements for various morpho-physiological, yield and quality related traits were taken following the potato crop trait ontology. The post-flowering stress induced in this study caused a tuber yield reduction of 33.13% compared with the non-stressed treatment. The genotypes responded differently in tuber yielding potential to the drought. This differential tuber yield response to drought was associated with up and downward regulation of multiple traits related to drought adaptation in potatoes. Drought caused downward regulation on trait responses such as harvest index, leaf area and specific leaf area. Plant height, aboveground biomass and relative water content of leaf contributed negatively for tuber yield under stressed condition. Therefore, the selection attributes identified from this study could help the potato breeding program in the country to develop climate resilient potato varieties. [ABSTRACT FROM AUTHOR]

Micronutrient deficiencies in diets, including iron (Fe) and zinc (Zn), are an important public health problem across population in Ethiopia. Potato is a modest source of dietary nutrients. The purpose of this study was to assess the mineral (Fe & Zn) composition of potato germplasm in Ethiopia and grower's willingness to try new potato types. The Fe and Zn contents were assessed in peeled tubers of popular farmer varieties, and newly introduced Andean diploid group Phureja accessions and improved tetraploid clones grown in multi-location trials. Grower's preferences for the new potato types was assessed using a participatory approach. Significant variations in mineral and tuber yield traits exist among the germplasm assessed and broad-sense heritability appears to be high for most traits measured, suggesting that progress through breeding can be made among these materials. However, the slightly negative correlation of tuber yield with Fe and Zn content and user appreciation traits found in this study suggests that progress in improving crops for yield and enhanced Fe and Zn concentrations with end-user acceptable quality will be challenging. The results from this study provide baseline information on Fe and Zn composition of many popular farmer varieties in Ethiopia and end-user preference criteria for evaluating new potato varieties that would help to orient the biofortification breeding to the conditions and preference of farmers. [ABSTRACT FROM AUTHOR]

Recurrent drought and late blight disease are the major factors limiting potato productivity in the northwest Ethiopian highlands. Incorporating drought tolerance and late blight resistance in the same genotypes will enable the development of cultivars with high and stable yield potential under erratic rainfall conditions. The objectives of this study were to assess combining ability effects and gene action for tuber yield and traits related to drought tolerance in the International Potato Centre’s (CIP’s) advanced clones from the late blight resistant breeding population B group ‘B3C2’ and to identify promising parents and families for cultivar development. Sixteen advanced clones from the late blight resistant breeding population were crossed in two sets using the North Carolina Design II. The resulting 32 families were evaluated together with five checks and 12 parental clones in a 7 x 7 lattice design with two water regimes and two replications. The experiment was carried out at Adet, in northwest Ethiopia under well-watered and water stressed conditions with terminal drought imposed from the tuber bulking stage. The results showed highly significant differences between families, checks, and parents for growth, physiological, and tuber yield related traits. Traits including marketable tuber yield, marketable tuber number, average tuber weight and groundcover were positively correlated with total tuber yield under both drought stressed and well-watered conditions. Plant height was correlated with yield only under drought stressed condition. GCA was more important than SCA for total tuber yield, marketable tuber yield, average tuber weight, plant height, groundcover, and chlorophyll content under stress. This study identified the parents with best GCA and the combinations with best SCA effects, for both tuber yield and drought tolerance related traits. The new population is shown to be a valuable genetic resource for variety selection and improvement of potato’s adaptation to the drought prone areas in northwest Ethiopia and similar environments. [ABSTRACT FROM AUTHOR]

Common beans are a warm-season, food legume cultivated in areas prone to water limitation throughout their growing season. This study assessed the magnitude and pattern of trait associations for a total of 202 common bean genotypes divided into panels of 81 Andean and 121 Mesoamerican gene pool accessions grown under contrasting treatments of well-watered, non-stress, and water-limited, terminal drought-stress conditions. Linear correlation, complex path coefficient, and genetic divergence analyses were used to dissect the relationship dynamics between traits and the relative contribution of adaptive traits to differentiation among gene pools and genotypes based on drought stress. Drought severity level for the trial was high and created the ideal condition to reveal genotypic differences, as seen by the differential response of the genotypes for the various traits measured. The value for phenotypic coefficients of variation for all traits was higher than the corresponding genotypic values. Seed yield had positive and strong genotypic and phenotypic correlation with pods per plant across gene pools and stress levels. The overall amount of genetic correlation was greater than the corresponding phenotypic correlation matrix for all the traits within the gene pool and across stress levels. Moreover, the results depicted the phenotypic correlation as equal or better than its genotypic counterpart in estimating drought tolerance in common bean plants. Clustering analysis with Mahanalobis's coefficient of generalized distance grouped genotypes with a differential level of drought adaptation into different classes within each panel. This indicates drought tolerance involves different mechanisms of plant response and is present separately in each gene pool panel. Pods per plant, seed weight, pod partitioning index, and harvest index are useful selection objectives to improve drought adaptation in common bean, but must be differentially weighted in each gene pool. The analysis of genetic variation and association between adaptive traits on the two panels provided useful insights on which traits could be used to improve common bean adaptation to low water availability during the growth season. [ABSTRACT FROM AUTHOR]

Drought is the major abiotic constraint contributing to yield reduction in common bean ( Phaseolus vulgaris L.) worldwide. An increasing scarcity of water in the future will make improving adaptation to drought stress a major objective of most crop breeding efforts. Drought avoidance by increased extraction of soil moisture from greater depth under drought conditions is an adaptive mechanism of common bean. A recombinant inbred line population of DOR364 × BAT477 was evaluated for rooting pattern traits in soil cylinder tubes under soil drying (progressive water stress) and non-stress (well-watered with 80% of field capacity) treatments in a greenhouse. One of the parents, BAT 477, is a deep-rooting genotype while the other parent, DOR 364, is a commercial cultivar in Central America. The recombinant inbred line population expressed quantitative variation and transgressive segregation for ten rooting pattern traits as well as five shoot traits of 48-day-old plants. A mixed model quantitative trait locus (QTL) mapping analysis was carried out using a genetic map constructed with 165 genetic markers that covered 11 linkage groups of the common bean genome. Genotype estimates were calculated from best design and spatial effects model for each trait. A total of 15 putative QTL were identified for seven rooting pattern traits and four shoot traits. The QTL detected were scattered over five of the 11 linkage groups. The QTL detected for all the root traits except total root length and fine root length were main effect QTL and did not interact with the level of water supply. The total root length and fine root length QTL with significant QTL × environment interaction only differed in magnitude of effect, and interaction was of a non-crossover type. Other QTL for total root length, fine roots, thick roots, root volume and root biomass were co-localized and also explained relatively more genetic variance. This suggests that the QTL affecting root traits in common beans are based on constitutive expression of genes and that drought avoidance based on deep rooting, longer root length, thicker roots, increasing root length distribution with depth, root volume and root biomass can be used in molecular breeding. The positive alleles for most of the QTL detected in this study were derived from the paternal parent BAT477. The results from the present analyses highlighted the feasibility of marker-aided selection as an alternative to conventional labor-intensive, phenotypic screening of drought avoidance root traits. [ABSTRACT FROM AUTHOR]

With 3 figures and 4 tables Abstract This study employed and compared different methods for capturing farmers' preference for common bean varieties in southern Ethiopia and tested their expressed preference using active selection of drought-tolerant genotypes. The results showed considerable variation in farmers' variety preferences, but the most important variation consistently focused on a fairly consistent set of variety traits. Different methods indicated that farmers considered earliness as the most important trait. Culinary qualities and marketability showed to be at least as important as drought tolerance. Comparing different methods in identifying farmers' preference indicated that recording farmers rating or ranking for traits in breeding may not be effective or predictive of adoption for new variety and resulting variation among farmers. Real-time participatory selection was quick, efficient and accurately revealed farmer preference. The relatively high level of coincidence of farmer selections and selections made by breeders and extensionists, combined with the relative consistent set of important traits to consider, suggest that diversity of farmers demand is not the first concern. The challenge of the common bean breeding for southern Ethiopia therefore lies in combining different mechanisms of drought tolerance with culinary attractiveness and marketability. Market in the study region shows to be fairly dynamic and as a consequence farmer preferences for grain types and colour are not static. Breeding that focuses on traditionally grown colours, shapes and sizes may therefore restrict farmers' access to novel attractive and adapted germplasm. [ABSTRACT FROM AUTHOR]

The East African highlands are a region of important common bean production and high varietal diversity for the crop. The objective of this study was to uncover the diversity and population structure of 192 landraces from Ethiopia and Kenya together with four genepool control genotypes using morphological phenotyping and microsatellite marker genotyping. The germplasm represented different common bean production ecologies and seed types common in these countries. The landraces showed considerable diversity that corresponded well to the two recognized genepools (Andean and Mesoamerican) with little introgression between these groups. Mesoamerican genotypes were predominant in Ethiopia while Andean genotypes were predominant in Kenya. Within each country, landraces from different collection sites were clustered together indicating potential gene flow between regions within Kenya or within Ethiopia. Across countries, landraces from the same country of origin tended to cluster together indicating distinct germplasm at the national level and limited gene flow between the two countries highlighting divided social networks within the regions and a weak trans-national bean seed exchange especially for landrace varieties. One exception to this may be the case of small red-seeded beans where informal cross-border grain trade occurs. We also observed that genetic divergence was slightly higher for the Ethiopian landraces compared to Kenyan landraces and that Mesoamerican genotypes were more diverse than the Andean genotypes. Common beans in eastern Africa are often cultivated in marginal, risk-prone farming systems and the observed landrace diversity should provide valuable alleles for adaptation to stressful environments in future breeding programs in the region. [ABSTRACT FROM AUTHOR]

Anthracnose disease caused by a fungus Colletotrichum gloeosporioides is the primary cause of yield loss in water yam (Dioscorea alata), the widely cultivated species of yam. Resistance to yam anthracnose disease (YAD) is a prime target in breeding initiatives to develop durable-resistant cultivars for sustainable management of the disease in water yam cultivation. This study aimed at tagging quantitative trait loci (QTL) for anthracnose disease resistance in a bi-parental mapping population of D. alata. Parent genotypes and their recombinant progenies were genotyped using the Genotyping by Sequencing (GBS) platform and phenotyped in two crop cycles for two years. A high-density genetic linkage map was built with 3184 polymorphic Single Nucleotide Polymorphism (NSP) markers well distributed across the genome, covering 1460.94 cM total length. On average, 163 SNP markers were mapped per chromosome with 0.58 genetic distances between SNPs. Four QTL regions related to yam anthracnose disease resistance were identified on three chromosomes. The proportion of phenotypic variance explained by these QTLs ranged from 29.54 to 39.40%. The QTL regions identified showed genes that code for known plant defense responses such as GDSL-like Lipase/Acylhydrolase, Protein kinase domain, and F-box protein. The results from the present study provide valuable insight into the genetic architecture of anthracnose resistance in water yam. The candidate markers identified herewith form a relevant resource to apply marker-assisted selection as an alternative to a conventional labor-intensive screening for anthracnose resistance in water yam. [ABSTRACT FROM AUTHOR]

Dioscorea alata (L.), also referred to as water, winged, or greater yam, is one of the most economically important staple food crops in tropical and subtropical areas. In Côte d'Ivoire, it represents, along with other yam species, the largest food crop and significantly contributes to food security. However, studies focusing on better understanding the structure and extent of genetic diversity among D. alata accessions, using molecular and phenotypic traits, are limited. This study was, therefore, conducted to assess the pattern of genetic variability in a set of 188 D. alata accessions from the National Agronomic Research Centre (CNRA) genebank using 11,722 SNP markers (generated by the Diversity Arrays Technology) and nine agronomic traits. Phylogenetic analyses using hierarchical clustering, admixture, kinship, and Discriminant analysis of principal component (DAPC) all assigned the accessions into four main clusters. Genetic diversity assessment using molecular-based SNP markers showed a high proportion of polymorphic SNPs (87.81%). The analysis of molecular variance (AMOVA) showed low molecular variability within genetic groups. In addition, the agronomic traits evaluated for two years in field conditions showed a high heritability and high variability among D. alata accessions. This study provides insights into the genetic diversity among accessions in the CNRA genebank and opens an avenue for sustainable resource management and the identification of promising parental clones for water yam breeding programs in Côte d'Ivoire. [ABSTRACT FROM AUTHOR]

The primary objective of this study was to assess the effects of genotype (G), location (L), and G × L interaction on tuber quality traits (dry matter content and starch pasting parameters) in white Guinea yam (Dioscorea rotundata Poir.). Variability in tuber dry matter and starch pasting properties was examined using 18 advanced breeding lines and two dominant landrace cultivars of white Guinea yam grown in three different agroecological zones (forest‒savanna transition, southern Guinea savanna, and rainforest) in Nigeria. The starch pasting properties were evaluated using a Rapid Visco Analyser. Our results show that the G × L interaction effect was low compared to the genotype and growing location effects on the variability of key starch properties. In addition, the repeatability of trait performance across locations was high and relatively uniform for key traits, suggesting that any of the three locations used in this study can be employed for their evaluation. Furthermore, TDr1100873 had a higher dry matter content than the dominant landrace cultivars (Amula and Meccakusa) but was similar to them in starch pasting properties. Hence, TDr1100873 is considered a suitable variety for future breeding activities. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) is a monocotyledonous herbaceous vine plant grown in the tropics and subtropics. It is a multi-species plant with varied intra- and interspecific ploidy levels. Of the 600 species, 11 are cultivated supporting the livelihood of over 300 million people. The paucity of information on ploidy and the genomic constitution is a significant challenge to the crop's genetic improvement through crossbreeding. The objective of this study was to investigate the ploidy levels of 236 accessions across six cultivated and two wild species using chromosome counting, flow cytometry and genotyping-based ploidy determination methods. Results obtained from chromosome counting and genotyping-based ploidy determination were in agreement. In majority of the accessions, chromosome counting and flow cytometry were congruent, allowing future rapid screening of ploidy levels using flow cytometry. Among cultivated accessions, 168 (71%) were diploid, 50 (21%) were triploid, and 12 (5%) were tetraploid. Two wild species included in the study were diploids. Resolution of ploidy level in yams offers opportunities for implementing successful breeding programmes through intra- and interspecific hybridization. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) species are predominantly dioecious, with male and female flowers borne on separate individuals. Cross-pollination is, therefore, essential for gene flow among and within yam species to achieve breeding objectives. Understanding genetic mechanisms underlying sex determination and cross-compatibility is crucial for planning a successful hybridization program. This study used the genome-wide association study (GWAS) approach for identifying genomic regions linked to sex and cross-compatibility in water yam (Dioscorea alata L.). We identified 54 markers linked to flower sex determination, among which 53 markers were on chromosome 6 and one on chromosome 11. Our result ascertained that D. alata is characterized by the male heterogametic sex determination system (XX/XY). The cross-compatibility indices, average crossability rate (ACR) and percentage high crossability (PHC), were controlled by loci on chromosomes 1, 6 and 17. Of the significant loci, SNPs located on chromosomes 1 and 17 were the most promising for ACR and PHC, respectively, and should be validated for use in D. alata hybridization activities to predict cross-compatibility success. A total of 61 putative gene/protein families with direct or indirect influence on plant reproduction were annotated in chromosomic regions controlling the target traits. This study provides valuable insights into the genetic control of D. alata sexual reproduction. It opens an avenue for developing genomic tools for predicting hybridization success in water yam breeding programs. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) plants are mostly dioecious and sometimes monoecious. Low, irregular, and asynchronous flowering of the genotypes are critical problems in yam breeding. Selecting suitable pollen parents and preserving yam pollen for future use are potential means of controlling these constraints and optimizing hybridization practice in yam breeding programs. However, implementing such procedures requires a robust protocol for pollen collection and viability testing to monitor pollen quality in the field and in storage. This study, therefore, aimed at optimizing the pollen germination assessment protocol for yam. The standard medium composition was stepwisely modified, the optimal growth condition was tested, and in vivo predictions were made. This study showed that the differences in yam pollen germination percentage are primarily linked to the genotype and growing conditions (i.e., medium viscosity, incubation temperature, and time to use) rather than the medium composition. The inclusion of polyethylene glycol (PEG) in the culture medium caused 67–75% inhibition of germination in D. alata. Although the in vivo fertilization was dependent on female parents, the in vitro germination test predicted the percentage fruit set at 25.2–79.7% and 26.4–59.7% accuracy for D. rotundata and D. alata genotypes, respectively. This study provides a reliable in vitro yam pollen germination protocol to support pollen management and preservation efforts in yam breeding. [ABSTRACT FROM AUTHOR]

The yam is an economic tuber crop utilized for food, feed, and various industrial applications. Botanical seed viability, seedling growth, and development are among factors that influence plant population dynamics, development, structure, and sustainability. However, little is known about seed viability, growth, and yield potential of seed-progenies developed using different mating designs. This study assessed seed germination, seedling growth, and yield traits in seed-progenies developed using North Carolina I (NC-1) and polycross mating designs. For this, seed germination and seedling nursery trials established using seed-progenies from different yam crosses were used. Results revealed that days to first seed germination (DAYFG), days to 50% germination (DAYSG), coefficient of velocity of germination, seed emergence speed (SES), germination index, final germination percent, and seedling vigor index significantly (p < 0.05) varied within and among NC-1 and PC-derived families. The mean days to first seed germination (DFSG) and DAYSG seed-progenies of NC-1 were significantly lower than the polycross progenies. Moreover, the seedling-progenies from the polycross produced a higher number of stems and more elongate tubers than those originated from the NC-1 mating. Progenies of family TDr1687 from a polycross mating were among the families that had the highest stem number (2.2), longest tuber (7.5 cm), and widest tuber (2.8 cm). The inter-family means of both NC-1 and polycross had a non-significant variation for mean tuber weight per plant. Our results suggest the relevance of seed germination and seedling attributes for selection of superior progenies at the early generation stage trials in yam breeding. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) is a monocotyledonous herbaceous vine cultivated for its starchy underground or aerial tubers in the tropics and subtropics. It is an allogamous and polyploid species that reproduces by both sexual and asexual mechanisms. However, many of the landrace cultivars, including most of the popular varieties, reproduce exclusively by vegetative propagation (planting the tubers). These varieties are either sterile or produce sparse and irregular flowering with high flower abortion rate, low fruit and seed set. Production of crossbreed seeds for genetic improvement and for maintaining genetic diversity in yams is, therefore, mainly achieved through natural or managed pollination. Flowering in yam is mostly dioecious and, in some instances, monoecious. Flowering asynchrony, sticky nature of the pollen grains, and cross incompatibility are among the challenges in making genetic progress in yam breeding. There are many limitations in basic and applied knowledge of yam flower biology and pollination. This paper, therefore, reviews the flowering biology, pollination, and methods of improving pollination efficiency in yam breeding programs. [ABSTRACT FROM AUTHOR]

White yam (Dioscorearotundata Poir.) is one of the most important tuber crops in West Africa, where it is indigenous and represents the largest repository of biodiversity through several years of domestication, production, consumption, and trade. In this study, the genotyping-by-sequencing (GBS) approach was used to sequence 814 genotypes consisting of genebank landraces, breeding lines, and market varieties to understand the level of genetic diversity and pattern of the population structure among them. The genetic diversity among different genotypes was assessed using three complementary clustering methods, the model-based admixture, discriminant analysis of principal components (DAPC), and phylogenetic tree. ADMIXTURE analysis revealed an optimum number of four groups that matched with the number of clusters obtained through phylogenetic tree. Clustering results obtained from ADMIXTURE analysis were further validated using DAPC-based clustering. Analysis of molecular variance (AMOVA) revealed high genetic diversity (96%) within each genetic group. A network analysis was further carried out to depict the genetic relationships among the three genetic groups (breeding lines, genebank landraces, and market varieties) used in the study. This study showed that the use of advanced sequencing techniques such as GBS coupled with statistical analysis is a robust method for assessing genetic diversity and population structure in a complex crop such as white yam. [ABSTRACT FROM AUTHOR]

Yam (Dioscorea spp.) is a nutritional and medicinal staple tuber crop grown in the tropics and sub-tropics. Among the food yam species, water yam (Dioscorea alata L.) is the most widely distributed and cultivated species worldwide. Tuber dry matter content (DMC) and oxidative browning (OxB) are important quality attributes that determine cultivar acceptability in water yam. This study used a single nucleotide polymorphism (SNP) assay from a diversity arrays technology (DArT) platform for a genome-wide association study (GWAS) of the two quality traits in a panel of 100 water yam clones grown in three environments. The marker–trait association analysis identified significant SNPs associated with tuber DMC on chromosomes 6 and 19 and with OxB on chromosome 5. The significant SNPs cumulatively explained 45.87 and 12.74% of the total phenotypic variation for the tuber DMC and OxB, respectively. Gene annotation for the significant SNP loci identified important genes associated in the process of the proteolytic modification of carbohydrates in the dry matter accumulation pathway as well as fatty acid β-oxidation in peroxisome for enzymatic oxidation. Additional putative genes were also identified in the peak SNP sites for both tuber dry matter and enzymatic oxidation with unknown functions. The results of this study provide valuable insight for further dissection of the genetic architecture of tuber dry matter and enzymatic oxidation in water yam. They also highlight SNP variants and genes useful for genomics-informed selection decisions in the breeding process for improving food quality traits in water yam. [ABSTRACT FROM AUTHOR]