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Grain weight is an important factor contributing to grain yield in wheat. Markers closely linked to grain weight could be used in marker-assisted selection (MAS) to accelerate the wheat breeding process. In this paper, a second backcross recombinant inbred line (BCF) population, a recombinant inbred line (RIL) population, and one natural population were used to study the relationship between allelic variants of the grain weight gene TaGW2- 6A and grain weight, width, and length with the goal of verifying the feasibility using the functional marker Hap-6A-P1/P2 in MAS. The differences in average grain weight, width, and length between haplotypes Hap-6A-G and Hap-6A-A were 8.09 g, 0.22 mm, and 0.38 mm, respectively, in the BCF population; 4.01 g, 0.11 mm, and 0.10 mm in the RIL population; and 3.95 g, 0.10 mm, and 0.20 mm in the natural population. All the differences were significant. Sequencing results of the products of second round PCR indicated that a 167 bp TaqI restriction fragment had been generated from small-grain-size materials because of three TaqI restriction sites (TCGA). However, the large-grain-size variant generated a 218 bp fragment due to a single-nucleotide mutation (SNP) (TCGA → TCGG) at the third site. TaGW2- 6A expression levels were negative with respect to grain width, length, and weight. For this reason, Hap-6A-G was considered a superior allele. These results contradict those of a previous study, which showed Hap-6A-A to be significantly associated with wider grain and higher grain weight. [ABSTRACT FROM AUTHOR]

This paper offers projections of potential effects of climate change on rusts of wheat and how we should factor in a changing climate when planning for the future management of these diseases. Even though the rusts of wheat have been extensively studied internationally, there is a paucity of information on the likely effects of a changing climate on the rusts and their influence on wheat production. Due to the lack of published empirical research we relied on the few published studies of other plant diseases, our own unpublished work and relevant information from the vast literature on rusts of wheat to prepare this overview. Three broad areas of potential risks from a changing climate were described: increased loss from wheat rusts, new rust pathotypes evolving faster and the reduced effectiveness of rust resistances. Increased biomass of wheat crops grown in the presence of elevated CO concentrations and higher temperatures will increase the leaf area available for attack by the pathogen leading to increased inoculum production. If changed weather conditions were to accelerate the life cycle of a pathogen, the increased inoculum can lead to severe rust epidemics in many environments. Likewise should the effects of climate change result in more conducive conditions for rust development there will also be a corresponding increase in the rate of evolution of new pathotypes which could increase the rate of appearance of new virulences. The effectiveness of some rust resistance genes is influenced by temperature and crop development stage. Climate change may directly or indirectly influence the effectiveness of some resistance genes but this can not be ascertained due to a complete lack of knowledge. Since disease resistance breeding is a long term strategy it is important to determine if any of the important genes may become less effective due to climate change. Studies must be made to acquire new information on the rust disease triangle to increase the adaptive capacity of wheat under climate change. Leadership within the Borlaug Global Rust Initiative (BGRI) is needed to broker research on rust evolution and the durability of resistance under climate change. [ABSTRACT FROM AUTHOR]

Farmer participation is increasingly seen as a key to develop technologies which are more relevant to farmers' communities. In plant breeding, farmer participation is seen as key to increase the probability of adoption of new varieties. This paper addresses the issue of selection efficiency in participatory plant breeding by testing the effect of selection environment and of who did the selection in one cropping season (1997) on the performance of the selected lines in the following cropping season (1998). Selection environment had a larger effect on response to selection than who did the selection, confirming the importance of decentralized selection. Selections made by the breeder and the farmers in 1997, differed in 1998 for a number of traits, but seldom for grain yield. When the difference for grain yield was significant, breeder's selection was more effective on station, while farmers' selection was more effective in farmers' fields. The results of this study indicate that it is possible to organize a plant breeding program with the objective of adapting crops to a multitude of both physical and socio-economic environments: such a breeding program will, at the same time, increase productivity and stability, enhance biodiversity and produce environmentally friendly cultivars. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is one of the macronutrients essential for plant growth and development. Rice (Oryza sativa L.) is sensitive to P starvation and its deficiency influences many key plant functions, resulting in crop yield penalties. Although the hybrid rice segment is well-known for its yield heterosis, P deficiency and bacterial leaf blight diseases are evident limitations. APMS6B, the female parent of DRRH-3 is susceptible to low P and bacterial blight disease. In the present study, the improvement of APMS6B to P starvation and resistance to bacterial leaf blight (BB) was carried out using the marker-assisted backcross breeding approach. Kasalath (+Pup1 QTL) was used as a donor, and a promising IL (ATR 594-1) at BC1F4 generation was identified with 81.15% of recurrent parent genome recovery. Concurrently, this IL was intercrossed with GU-2 (+Xa21 and Xa38). Intercross F1s (ICF1) hybridity was confirmed through foreground selection having maximum RPGR (88.29%) and was selfed to produce ICF2. The resultant progenies were phenotyped for BB using Xoo inoculum (IX-020), simultaneously genotyped with gene-specific functional SSR markers forXa21 and Xa38. The identified BB-resistant plants were subjected to foreground selection for Pup1. Four promising ICF3 plants (BP-10-1, BP-10-3, BP-10-5, and BP-10-15 with Xa21, Xa38, and Pup1) along with parents and checks were screened both in low P plot (< 2 kg P2O5 ha−1) as well as in normal plot (> 25 kg P2O5 ha−1) during dry and wet seasons 2018. The field evaluation identified four promising intercrossed lines with better root growth in the primary root length of extracted zone and root volume. In addition, fewer reductions in grain yield (39.10%) under P starvation and less susceptibility indices values (< 1) for BB were observed. These lines may be exploited in the CMS conversion and development of climate-resilient, biotic and abiotic stress-tolerant rice hybrids. [ABSTRACT FROM AUTHOR]

The Leguminosae constitutes the second largest family of plants in the world. In the face of global climate change and reduction of cultivated land area, legumes have been attached more importance to feed the future in light of their nutritional values and environmental benefits. However, the yields of legume crops have thus far been far below their theoretical potentials. Despite that hybrid breeding and gene editing technologies have hold great promises to the improvement of crops, they are generally difficult to apply in legumes because of the anatomical constraints for making hybrids in these species and the low transformation efficiency impeding gene modifications. Mutation technologies, as an alternative, can speed up breeding and facilitate functional genomic studies in legume species, yet mutant screening technique remains a major challenge in this field. In this review, we detail the currently available mutant library resources in major legume crops following a brief introduction of the methods of mutation induction. We then revisit the current mainstream technologies for mutant screening, with focus on the new emerging next-generation sequencing-based approaches. Overall, this review provides a collection of information that dedicates to assisting legume researchers and breeders to more easily find and better utilize mutant resources for the improvement of these crops. [ABSTRACT FROM AUTHOR]

During the last decades extensive progress has been achieved in winter barley breeding with respect to both, yield and resistance to fungal and viral diseases. This progress is mainly due to the efficient use of the genetic diversity present within high yielding adapted cultivars and – with respect to resistance – to the extensive evaluation of genetic resources followed by genetic analyses and introgression of respective genes by sexual recombination. Detailed knowledge on genetic diversity present on the molecular level regarding specific traits as well as on the whole genome level may enhance barley breeding today by facilitating efficient selection of parental lines and marker assisted selection procedures. In the present paper the state of the art with respect to virus diseases, i.e. Barley mild mosaic virus, Barley yellow mosaic virus, and Barley yellow dwarf virus is briefly reviewed and first results on a project aiming on a genome wide estimation of genetic diversity which in combination with data on yield and additional agronomic traits may facilitate the detection of marker trait associations and a more efficient selection of parental genotypes are presented. By field tests of 49 two-rowed and 64 six-rowed winter barley cultivars the genetic gain in yield for the period 1970–2003 was estimated at 54.6 kg ha−1 year−1 ( r 2 = 0.567) for the six-rowed cultivars and at 37.5 kg ha−1 year−1 ( r 2 = 0.621) for the two-rowed cultivars. Analysis of 30 SSRs revealed a non-homogenous allele distribution between two and six-rowed cultivars and changes of allele frequencies in relation to the time of release. By PCoA a separation between two and six-rowed cultivars was observed but no clear cut differentiation in relation to the time of release. In the two-rowed cultivars an increase in genetic diversity (DI) from older to newly released cultivars was detected. [ABSTRACT FROM AUTHOR]

Problem soils impose various stresses on plants and significantly reduce crop yield. As a sizable area sown in food legume crops falls under the designation of problem soils, the development of tolerant varieties and appropriate agronomic practices to ameliorate problem soils is required to increase food legume production. With respect to food legume cultivation, research efforts focusing on the development of cultivars tolerant to problem soils and on integrated management practices for soil amelioration have been limited to date. Here we review the various types of problematic soils and recent efforts in the development of appropriate technologies, including high-throughput plant phenotyping, breeding of tolerant varieties, and innovations in agronomy, that are contributing to or potentially will contribute to the adaptation of food legume crops to problem soils. The significant points are: (1) recent advances in plant phenotyping platforms offer new suites of technologies that facilitate the rapid identification of new genes related to tolerance mechanisms and the rapid development of improved cultivars better adapted to adverse soil conditions; (2) advances in plant genomics and recent developments in plant phenomics contribute towards more precise measurements of plant traits of interest; and (3) improved agronomic practices with appropriate amelioration measures would help to bring about changes in the soil conditions, improving them for cultivation and also providing a practical solution for problem soils. Integrated approaches, including tolerant varieties, amelioration measures, and improved agronomic practices suitable for the region, have the potential to be a sustainable approach by which food legumes could be adapted to problem soils. [ABSTRACT FROM AUTHOR]

Increased modern farming of superior types of the oil palm, Elaeis guineensis Jacq., which has naturally efficient oil biosynthesis, has made it the world's foremost edible oil crop. Breeding improvement is, however, circumscribed by time and costs associated with the tree's long reproductive cycle, large size and 10-15 years of field testing. Marker-assisted breeding has considerable potential for improving this crop. Towards this, quantitative trait loci (QTL) linked to oil yield component traits were mapped in a high-yield population. In total, 164 QTLs associated with 21 oil yield component traits were discovered, with cumulative QTL effects increasing in tandem with the number of QTL markers and matching the QT+ alleles for each trait. The QTLs confirmed all traits to be polygenic, with many genes of individual small effects on independent loci, but epistatic interactions are not ruled out. Furthermore, several QTLs maybe pleiotropic as suggested by QTL clustering of inter-related traits on almost all linkage groups. Certain regions of the chromosomes seem richer in the genes affecting a particular yield component trait and likely encompass pleiotropic, epistatic and heterotic effects. A large proportion of the identified additive effects from QTLs may actually arise from genic interactions between loci. Comparisons with previous mapping studies show that most of the QTLs were for similar traits and shared similar marker intervals on the same linkage groups. Practical applications for such QTLs in marker-assisted breeding will require seeking them out in different genetic backgrounds and environments. [ABSTRACT FROM AUTHOR]

Process-based grassland models (PBMs) simulate growth and development of vegetation over time. The models tend to have a large number of parameters that represent properties of the plants. To simulate different cultivars of the same species, different parameter values are required. Parameter differences may be interpreted as genetic variation for plant traits. Despite this natural connection between PBMs and plant genetics, there are only few examples of successful use of PBMs in plant breeding. Here we present a new procedure by which PBMs can help design ideotypes, i.e. virtual cultivars that optimally combine properties of existing cultivars. Ideotypes constitute selection targets for breeding. The procedure consists of four steps: (1) Bayesian calibration of model parameters using data from cultivar trials, (2) Estimating genetic variation for parameters from the combination of cultivar-specific calibrated parameter distributions, (3) Identifying parameter combinations that meet breeding objectives, (4) Translating model results to practice, i.e. interpreting parameters in terms of practical selection criteria. We show an application of the procedure to timothy ( Phleum pratense L.) as grown in different regions of Norway. [ABSTRACT FROM AUTHOR]

Sweetpotato is a good source of energy, easy-to-grow and hardy and thus useful in contributing to food security. The current study aimed at identification of the best sweetpotato varieties for multiple desirable traits such as good yield, adaptability (including vine vigor) and tastiness (high dry mass content; taste). Ten South African sweetpotato varieties were evaluated during the period 2002/3-2007/8 at six locations each over two seasons. The sites regression model (SREG) of the genotype plus genotype by environment interaction (GGE) biplot analysis was performed with GenStat to determine stability and adaptability of the varieties. Subsequently, multiple trait selection was performed by using the ranking from Elston index selection. To enable inclusion of varietal stability in multiple trait selection, a stability value was calculated. High yielding varieties included Blesbok, Monate, Ndou and Letlhabula, of which Monate and Letlhabula had stable performance. The advantage, particularly for resource-poor farmers, of a specifically adapted, responsive variety such as Ndou, is the ability to respond to changes in the environment. Based on multiple trait selection varieties Ndou and Monate were recommended for production. The results present an innovative use of Elston index selection, including a stability value, in combination with GGE SREG for recommending varieties with multiple desirable traits. The recommended varieties are of significance for future use to improve food security. [ABSTRACT FROM AUTHOR]

The relationship between crop height and yield is complex with genes and genetic markers for greater height associated with both increases and decreases in yield. As a result of this the optimum height for maximum potential yield is not well understood and has been estimated at between 70 and 100 cm. This study investigated the effect of plant breeding on the height of UK winter wheat varieties by analysing data on straw shortness scores and absolute height collected from UK national variety testing trials between 1977 and 2013. The analysis showed that varietal introductions between the early 1970s and 1980 shortened plant height by approximately 15 cm (110-95 cm) followed by a gradual reduction to about 88 cm by the 1990s. There was no significant trend in height between 1990 and 2013. It was estimated that the reduction in plant height between 1970 and 2000 would have been sufficient to counteract the increase in lodging risk caused by the increase in yield potential of new varieties over this period of approximately 3 t/ha. It is predicted that the lodging risk of varieties introduced since 2000 are likely to have increased due to further increases in yield potential and the absence of further shortening. Possible reasons why UK plant breeders have not continued to shorten wheat are considered. [ABSTRACT FROM AUTHOR]

Abiotic and biotic stress factors are the major constrains for the realization of crop yield potential. As climate change progresses, the spread and intensity of abiotic as well as biotic stressors is expected to increase, with increased probability of crops being exposed to both types of stress. Shielding crops from combinatorial stress requires a better understanding of the plant's response and its genetic architecture. In this study, we evaluated resistance to salt stress, powdery mildew and to both stresses combined in tomato, using the Solanum habrochaites LYC4 introgression line (IL) population. The IL population segregated for both salt stress tolerance and powdery mildew resistance. Using SNP array marker data, QTLs were identified for salt tolerance as well as Na and Cl accumulation. Salt stress increased the susceptibility of the population to powdery mildew in an additive manner. Phenotypic variation for disease resistance was reduced under combined stress as indicated by the coefficient of variation. No correlation was found between disease resistance and Na and Cl accumulation under combined stress Most genetic loci were specific for either salt stress tolerance or powdery mildew resistance. These findings increase our understanding of the genetic regulation of responses to abiotic and biotic stress combinations and can provide leads to more efficiently breeding tomatoes and other crops with a high level of disease resistance while maintaining their performance in combination with abiotic stress. [ABSTRACT FROM AUTHOR]

Soil waterlogging is a primary constraint to crop yield both globally and in the United States, yet little is known about the genetic control of waterlogging tolerance in wheat. The objective of this study was to characterize genetic variation for key adaptive traits influencing waterlogging tolerance at the vegetative stage and to identify associated quantitative trait loci (QTL). Traits measured included shoot and root biomass, root length, tiller number, seedling height, stem elongation, and chlorophyll content. Waterlogging reduced traits means by 8-58 % in the greenhouse and by 22-32 % in the field, with the largest reduction observed for root length. Both root biomass and root length showed significant genotype by treatment interaction indicating an adaptive growth response in waterlogged versus non-waterlogged soils and a possible mechanism of tolerance. A positive correlation was observed between chlorophyll content and shoot biomass, and between root and shoot biomass under waterlogging, which may make indirect selection possible. QTL analysis identified 48 individual QTL that clustered into 10 genomic regions consistently detected in both the greenhouse and field experiments. While most clusters were constitutively expressed, regions on chromosomes 1B and 6D were found to be adaptive to conditions of soil waterlogging, with no QTL detected in the non-waterlogged controls. A QTL region on chromosome 1D specific for chlorophyll content was significant across environments and repeated measurements, explaining up to 24 % of the phenotypic variation. This study provides the first reported QTL for waterlogging tolerance in wheat identified under both field and greenhouse conditions. The QTL can be targeted by breeders for future genetic improvement. [ABSTRACT FROM AUTHOR]

Potassium (K) deficiency is a major factor limiting crop development and yield. In this study, 20 traits were investigated at the seedling stage using a doubled-haploid population subjected to normal K and K deprivation treatments. Evaluation of phenotypes expressed under the two K supply conditions revealed that K deprivation was able to decrease values of ten measured traits, whereas values of the other ten traits increased. A total of 65 QTLs were detected across all 21 chromosomes, except for chromosomes 2B, 5A, and 7B. Individual QTLs in the two K supply treatments explained between 5.35 and 39.64 % of the phenotypic variation. Nine QTL clusters (C1-C9) involving 34 QTLs under the different K supply treatments were mapped to chromosomes 1A, 1B, 1D, 3B, 4A, 5B, 6A, and 7B. Our results are helpful for understanding the genetic basis of K deficiency in wheat, and provide useful information for genetic improvement of K deficiency in wheat by marker-assisted selection. [ABSTRACT FROM AUTHOR]

Heterosis (or hybrid vigor) is a natural phenomenon whereby hybrid offspring of genetically diverse individuals display improved physical and functional characteristics relative to their parents. Heterosis has been increasingly applied in crop production for nearly a century, with the aim of developing more vigorous, higher yielding and better performing cultivars. In this review we present and compare three categories of crop heterosis utilization: intraspecific heterosis, intersubspecific heterosis and wide-hybridization heterosis, with particular focus on polyploid species. Different pollination-control systems used to breed for heterosis are also comparatively analyzed. Finally, we highlight problems involved in heterosis research and crop improvement. We aim to provide insight into best practices for amplifying heterosis potential. [ABSTRACT FROM AUTHOR]

Multi-environment trials represent a highly valuable tool for the identification of the genetic bases of crop yield potential and stress adaptation. A Diversity Array Technology-based barley map has been developed in the 'Nure' × 'Tremois' biparental Doubled Haploid population, harbouring the genomic position of a gene set with a putative role in the regulation of flowering time and abiotic stress response in barley. The population has been evaluated in eighteen location-by-year combinations across the Mediterranean basin. QTL mapping identified several genomic regions responsible for barley adaptation to Mediterranean conditions in terms of phenology, grain yield and yield component traits. The most frequently detected yield QTL had the early flowering HvCEN_EPS2 locus (chromosome 2H) as peak marker, showing a positive effect from the early winter parent 'Nure' in eight field trials, and explaining up to 45.8 % of the observed variance for grain yield. The HvBM5A_VRN- H1 locus on chromosome 5H and the genomic region possibly corresponding to PPD- H2 on chromosome 1H were significantly associated to grain yield in five and three locations, respectively. Environment-specific QTLs for grain yield, and clusters of yield component QTLs not related to phenology and or developmental genes (e.g. on chromosome 4H, BIN_09) were observed as well. The results of this work provide a valuable source of knowledge and tools for both explaining the genetic bases of barley yield adaptation across the Mediterranean basin, and using QTL-associated markers for MAS pre-breeding and breeding programmes. [ABSTRACT FROM AUTHOR]

A deep and thick root system has a positive effect on wheat yield, particularly in drought environments. A doubled haploid (DH) population of 150 lines derived from the cross Hanxuan 10 × Lumai 14 was used to map QTLs for seedling root characteristics. The DH lines were cultivated in an agarose gel-chamber under well-watered (WW) and water-stressed (WS) regimes. Water stress was simulated by adding mannitol to the agarose gel. The seminal root traits, including maximum root length (MRL), seminal root number, total root length, project root area, root surface area, and seminal root angle were measured after 6 days of seedling development. Grain yields (GY) were measured in a field experiment. A total of 29 QTLs were identified for seedlings cultured under WW regimes, and 23 QTLs under WS regimes. Individual QTL accounted for phenotypic variations ranging from 4.98 to 24.31 %. The QTLs were distributed on 17 chromosomes, except 1D, 4D, 6B and 6D. Seven consistently expressed QTLs were detected for all the traits tested except MRL under both water regimes. The QTLs for root traits were unevenly distributed among chromosomes, and clustered in eight loci on seven chromosomes, showing pleiotropic effects on target traits. One region in the interval Xgwm644.2- P6901.2 on chromosome 3B contained 9 QTLs affecting most root traits. The present data provide an insight into the genetic basis of seedling root development under different water regimes and may benefit breeding programs using marker-assisted selection (MAS) for root traits. [ABSTRACT FROM AUTHOR]

Numerous bacterial, fungal, and viral diseases cause severe damage on roots, foliage, stem, pods, and seeds, resulting in yield and quality losses in common bean ( Phaseolus vulgaris L.) worldwide. Cultivars with resistance to multiple diseases are needed to reduce these losses and dependence on pesticides for disease control. Our objective was to determine the effectiveness of simultaneous selection in the F and F for resistance to five diseases, namely angular leaf spot (ALS), anthracnose (ANT), bean common mosaic (BCM), common bacterial blight (CBB), and common bean rust (CBR) in three Andean x Middle American inter-gene pool double-cross populations, namely ST = 'Chocho'/'Catrachita'//G 5686/VAX 3, CN = 'DIACOL Calima'/VAX 6//A 193/G 5686, and CB = A 483/'Talash'//Wilkinson 2/G 5686. One hundred seventy-five F plants of ST, 177 of CN, and 195 of CB and their parents were evaluated in the greenhouse using sequential inoculations with pathogens causing BCM, CBR, ALS, CBB, and ANT, in that order. Progenies of surviving F plants were again evaluated in the F, using similar sequential inoculations. The F-derived F breeding lines were developed using single-seed descent method. No selection was practiced for any trait in the F and F. In the F, five breeding lines from ST, two from CN, and one from CB exhibited intermediate to high levels of resistance to the five diseases when compared with the parents. Thus, selection in the F and F was effective for simultaneous introgression of resistance to the five diseases in all three Andean × Middle American inter-gene pool common bean populations. [ABSTRACT FROM AUTHOR]

Four bacterial blight (BB) resistance genes, Xa7, Xa21, Xa22 and Xa23, were introgressed into an elite hybrid rice restorer line Huahui 1035, by marker-assisted selection (MAS). Ten promising BB resistant lines identified by MAS approach in Huahui 1035 restorer background and their respective F hybrids with a cytoplasmic male sterile line i.e. Jinke 1A, three BB resistant gene donors and their recurrent parent were evaluated for BB resistance by inoculating them with eleven representative races of Xanthomonas oryzae pv . oryzae ( Xoo) in China. Further, the ten marker assisted selection of BB (MAS-BB) resistant restorer lines and their F hybrids were also characterized for agro-morphological traits and grain yield. Results revealed that restorer lines with Xa23 introgression i.e. HBQ809 and HBQ810 were found to be resistant to all eleven Chinese representative Xoo races, showing broad spectrum resistance to BB. However, the lines possessing Xa7 or Xa7+ Xa21 were resistant to ten out of eleven Xoo races. While restorer lines with Xa21 were resistant to nine out of eleven Xoo races. Interestingly, the F hybrids with Xa23, Xa7 or Xa7+ Xa21 were resistant to two severe epidemic Xoo races of China. Restorer lines i.e. HBQ807 and HBQ808 possessing Xa22 were only resistant to six or five out of inoculated eleven Xoo races. Lesion length comparisons between restorer lines and their F hybrids for the above four BB resistance genes showed them to be dominant in heterozygote genotype. Three promising high yielding F hybrids with BB resistance were identified for immediate exploitation for hybrid rice production in China. [ABSTRACT FROM AUTHOR]

Fusarium wilt is the main pigeonpea production constraint in Malawi. The purpose of the study was to understand the nature and mechanism of inheritance of F. wilt resistance, yield and secondary traits in pigeonpea. 48 crosses were generated in a 12 lines × 4 testers mating scheme. Some F plants were selfed for segregation analysis for inheritance pattern of resistance, while others were evaluated for resistance, yield and secondary traits. There were significant variations among F plants for F. wilt, days to 50 % flowering, seed/pod, and number of secondary branches. Specific combining ability (SCA) effects were predominant for F. wilt, days to 50 % flowering and number of secondary branches. The general combining ability (GCA) effects, mainly due to maternal genotypes, were preponderant for yield and other secondary traits. The significance of GCA and SCA effects suggested that variations were due to additive gene action in both the testers and parental lines arising from their interactions, and the dominance effects due to interactions of the parental lines. The χ analysis suggested dominant patterns of inheritance for wilt in most of the F populations. The segregation ratios of 3:1, 15:1, and 9:7 suggested the involvement of single or two independent/complementary dominant genes in the test donors. Involvement of a few genes governing wilt resistance suggested the ease of breeding for this trait. Pedigree breeding method would be recommended for incorporating various traits in pigeonpea. [ABSTRACT FROM AUTHOR]

Popcorn breeding programs in Brazil have emerged but despite some advances there is still a lack of material performance studies specially regard to seed quality, in different agricultural seasons. This research was carried out to estimate the popcorn combining ability from biparental crosses between eight tropical and one temperate lines in two agricultural seasons (2008 and 2009) with regard to eight traits related to seed quality, in addition to three agronomic traits related to popping expansion. Method 4, proposed by Griffing (Model 1), was used to verifying the importance of the dominance effect in the genetic control of the seed quality traits, favouring the identification of superior hybrids through seed tests in the laboratory with low cost. The lines from Zélia and CMS42 were promising in obtaining hybrids with superior seed quality and greater popping expansion. The hybrids Zélia × IAC-112, CMS42 × UEM M2-1, CMS43-1 × IAC-112 and UEM M2-2 × Zaeli expressed superior SCA for grain yield, popping expansion and at least two seed quality traits. These hybrids are materials of interest for cultivation in different planting seasons. [ABSTRACT FROM AUTHOR]

Oil content and grain yield in maize are negatively correlated, and so far the development of high-oil high-yielding hybrids has not been accomplished. Then a fully understand of the inheritance of the kernel oil content is necessary to implement a breeding program to improve both traits simultaneously. Conventional and molecular marker analyses of the design III were carried out from a reference population developed from two tropical inbred lines divergent for kernel oil content. The results showed that additive variance was quite larger than the dominance variance, and the heritability coefficient was very high. Sixteen QTL were mapped, they were not evenly distributed along the chromosomes, and accounted for 30.91% of the genetic variance. The average level of dominance computed from both conventional and QTL analysis was partial dominance. The overall results indicated that the additive effects were more important than the dominance effects, the latter were not unidirectional and then heterosis could not be exploited in crosses. Most of the favorable alleles of the QTL were in the high-oil parental inbred, which could be transferred to other inbreds via marker-assisted backcross selection. Our results coupled with reported information indicated that the development of high-oil hybrids with acceptable yields could be accomplished by using marker-assisted selection involving oil content, grain yield and its components. Finally, to exploit the xenia effect to increase even more the oil content, these hybrids should be used in the Top Cross procedure. [ABSTRACT FROM AUTHOR]

Single crosses (SC) of elite inbreds and open-pollinated populations (OP) are suitable source germplasm for doubled haploid (DH) line development in hybrid maize breeding, given that they combine a high population mean ( $$ \overline{x} $$) for testcross performance with adequate response to selection ( $$ \Updelta G $$). This is the first study reporting testcross grain yield (TCGY) and dry matter content (TCDMC) evaluations of 131 DH lines developed from ten tropical source germplasm comprising five OP (OP1-OP5) and five SC (SC1-SC5). Gene diversity ( d) and the average number of alleles ( a) per locus was estimated for DH lines based on 24 simple sequence repeat markers. Analysis across three environments revealed no significant differences between $$ \overline{x} $$ of OP- and SC-derived DH lines for TCGY and TCDMC. Significant genetic variance for both traits was only detected among OP-derived DH lines which may be explained by a larger number of segregating quantitative trait loci (QTL) as suggested by higher d and a values than in SC-derived DH lines. The usefulness criterion ( $$ U = \overline{x} + \Updelta G $$) was higher for OP-derived DH lines for TCDMC, but higher for SC-derived DH lines for TCGY. DH lines from OP1, OP2, and OP3 showed high TCGY, suggesting that they may be useful in tropical hybrid breeding. We conclude that tropical OP represent a valuable source of untapped genetic variation that can efficiently be exploited with DH technology for hybrid maize breeding. [ABSTRACT FROM AUTHOR]

Grain yield is more likely to be compromised by poor seed germination and vigour in low phytic acid (LPA) and quality protein maize (QPM) than normal maize (Nm), especially when grown under stressful tropical environmental conditions. The objectives of this study were to determine the effect of stress conditions on seed germination and vigour traits (percentage germination, seedling dry weight, average root and shoot length and vigour index) and to determine the GCA effects of the parental lines and SCA effects of the crosses. A ten parent half diallel (LPA, Nm, QPM lines) was subjected to the standard germination (non-stress) and accelerated aging (AA) (stress) tests. All seed lots were at the same physiological age and produced under the same season and conditions. Genotypic and group differences were investigated. General combining ability (GCA) and specific combining ability (SCA) effects were significant ( P ≤ 0.001) for all traits under both stress and non-stress conditions indicating that both additive and non-additive gene effects were significant. Generally SCA effects were superior for all traits. The LPA lines displayed 61 % reduction in germination and 23-52 % reduction in vigour under stress conditions thereby underscoring challenges that are expected in deploying LPA maize in stress conditions. However, LPA line CM 31 exhibited large positive and mostly significant GCA effects, while two LPA × LPA crosses showed significant positive SCA effects. Results indicate breeding is required to improve both germination and vigour of the LPA lines to adapt them to tropical conditions that are generally stress-prone. [ABSTRACT FROM AUTHOR]

Quantitative trait loci for yield, yield components and seed protein content were investigated on the basis of experiments performed with two populations of pea ( Pisum sativum L.) lines derived from linked crosses between lines Wt11238, Wt3557 and Wt10245 with contrasting characteristics. The yield-related traits were defined as components giving the grain yield in a multiplicative way. The aim was to clarify the genetic architecture of the relation between seed yield, its components and protein content, with a possible inclusion of the role of epistasis in this explanation. To take full advantage of the availability of the two populations, additive QTL effects and both types of epistasis were analysed: the QTL by genetic background interaction and the first-order QTL-QTL interaction. The two hybrid populations differed with respect to the prevailing gene action, which in the Wt11238 × Wt3557 progeny was mainly additive, while in the Wt10245 × Wt11238 progeny mainly epistatic. Some loci with previously reported, large, repeatable, but contradictory effects on yield and protein content were confirmed. New loci with alleles coming from the protein-rich Wt11238 line, positive for yield components, were identified. It was found that the first order QTL-QTL interaction events were more frequent for the loci showing the QTL by genetic background interaction. [ABSTRACT FROM AUTHOR]

Asian soybean rust is a major threat to worldwide soybean production at present. Host plant resistance offers the most sustainable control strategy to resource poor farmers in sub-Saharan Africa and worldwide. Using 13 soybean lines bred for resistance to soybean rust, and 2 checks, yield trials were conducted at four regions of Uganda for four consecutive seasons to determine yield stability and reaction to soybean rust disease. An additive main effects and multiplicative interaction (AMMI) model was used to assess the yield stability of the soybean lines. Stable lines identified included MNG 7.13, MNG 8.10, and MNG 1.63, which showed the lowest environmental interaction. These lines also out-yielded the local checks by over 300 kg ha, indicating that they have potential to boost soybean yields in the tropics. Line MNG 8.10 showed adaptability to most of the locations and had the highest yield among the three most stable lines, making it the most promising line; it is therefore recommended for release to improve soybean production and productivity in the region. [ABSTRACT FROM AUTHOR]

Drought stress is one of the most important environmental factors that limit plant growth and development, thus reducing yield. The objective of the present research was to correlate the genetic structure of different Fragaria genotypes, as assessed by Expressed Sequence Tag (EST) and Amplified Fragment Length Polymorphism (AFLP) markers, and plant responses to drought stress. Firstly, physiological parameters related to the plant response to drought stress such as leaf relative water content (RWC) and water losing rate (WLR) were measured. WLR and RWC were compared for 20 cultivars of the octaploid Fragaria × ananassa, two ecotypes of the diploid species F. vesca and one octaploid species F. chiloensis. These parameters could discriminate genotypes showing a contrasting response to water stress. Secondly, AFLP and ESTs were compared in terms of their information content and efficiency in the study of genetic diversity and relationships among these 23 Fragaria genotypes. To evaluate the genetic basis for the observed variation in the measured physiological parameter, the effect of specific AFLP/EST loci on WLR and RWC for the different Fragaria genotypes was quantified by Kruskal-Wallis analysis. By Mantel testing, the hierarchical clustering of the Fragaria genotypes based on associated EST or AFLP markers was compared to the observed eco-physiological relevant grouping. A better discriminating capacity for associated markers was noted, enabling a functional marker selection approach to screen the strawberry gene pool for drought tolerance. Correlation of EST markers to leaf RWC and WLR enforces them as potential candidate genes in control of plant responses to drought stress in Fragaria sp. [ABSTRACT FROM AUTHOR]

elerated climate change affects components of complex biological interactions differentially, often causing changes that are difficult to predict. Crop yield and quality are affected by climate change directly, and indirectly, through diseases that themselves will change but remain important. These effects are difficult to dissect and model as their mechanistic bases are generally poorly understood. A combination of integrated modelling from different disciplines and multi-factorial experimentation is needed to advance our understanding and prioritisation of the challenges. This will help prioritise breeding objectives. Food security brings in additional socio-economic, geographical and political factors. Enhancing resilience to the effects of climate change is important for all these systems and functional diversity, particularly in tolerance traits for abiotic and biotic stress, is one of the most effective targets for improved sustainability. [ABSTRACT FROM AUTHOR]

Exploiting genetic variation through inter-specific breeding has improved cotton yield, fibre properties and adaptability. The objectives of this study were to examine heritability and predicted selection response of yield components and fibre properties in a recombinant inbred line (RIL) population from an inter-specific cross between Gossypium hirsutum (Gh) variety Guazuncho 2, and G. barbadense (Gb) line VH8-4602. A population of 93 and 82 RILs was tested in two seasons, with two parents and local controls, Sicot 75 (Gh) and Sipima 280 (Gb) in field experiments. Seed cotton samples hand harvested before and after defoliation were used to measure lint percent, boll weight, 100 seed weight and the lint to measure fibre length, uniformity, short fibre index (SFI), elongation, strength, micronaire, maturity ratio (MR), percent of maturity (PM) and fineness. There was large phenotypic variation for individual traits and transgressive segregation occurred in lint percent, lint weight/seed, fibre no./seed, uniformity, SFI, elongation, MR and PM. Narrow sense heritabilities were moderate for yield components (34.3-41.2%) and for key fibre properties, length, strength, micronaire and fineness (38.3-42.1%), which led to a predicted selection response of 6.7-24.0% for yield components and 3.9-10.9% for key fibre properties under a selection intensity of 10%. Favourable associations were found between key fibre properties, but an adverse association between lint percent and each of these fibre properties. Only five RILs were identified with desirable combinations. The results demonstrated the value of exploiting inter-specific variation to develop cotton germplasm and how breeding strategies can be improved. [ABSTRACT FROM AUTHOR]

Seed dormancy (SD) is controlled by its own complicated genetic factors and environmental factors. SD is an important trait affecting grain yield and quality in cereal crops. A population comprising 240 recombinant inbred lines (RIL) was used for detecting quantitative trait locus (QTL) for SD in rice. To minimize the effect of environment, data for lines for which the optimum temperature during the late ripening stage is either below 20°C or above 30°C were excluded from the analysis, which left 185 lines. In a dynamic germination test of the parents of the population, Minghui 63 showed clear SD and Zhenshan 97 showed none. The seeds of each RIL, harvested 32 days after heading, were divided into two lots: seeds in one lot were sown immediately, without any treatment to break their dormancy, whereas seeds in the other lot were sown after they had been exposed to dry heat (50°C) for 72 h. Composite interval mapping showed the presence of qDGE1, qDGR5a, qDGR5b, and qDGR7 in the first lot whereas only qDGR7 was detected in the second lot--which had been treated to break SD--indicating the strong influence of qDGR7 in controlling SD. A recently cloned Sdr4 is also located in the qDGR7 region. Coincidently, three rice homologues of Arabidopsis SD gene DOG1 were found in qDGE1 and qDGR5b regions where no SD QTL had been reported so far. These results indicate that the QTL found in this study are reliable, and that it would be worthwhile to clone qDGE1 and qDGR5b. [ABSTRACT FROM AUTHOR]

Soils with higher concentrations of salt are becoming more and more a constraint for many crops to obtain high yields. Wild tomato species, adapted to adverse environments, are a potential reservoir for genes underlying quantitative trait loci (QTL) related to salt tolerance in tomato. In this study two introgression line (IL) libraries derived from two different wild species, Solanum pennellii LA716 and Solanum lycopersicoides LA2951, were used to identify QTLs for salt tolerance in the seedling stage. In the S. pennellii IL library, four major QTLs were identified on chromosomes 6, 7 and 11. In the S. lycopersicoides IL library, six major QTLs were discovered which are located on chromosomes 4, 6, 9 and 12. Co-localization of QTLs on chromosome 6 in the two IL libraries and previously reports hinted that this locus might be conserved in the tomato crop. Three S. pennellii ILs (IL6-2, IL7-1 and IL7-5) harboring QTLs on chromosome 6 and 7 were crossed. Semi-dominance and dominance were shown for these three QTLs, and non-additive and epistatic interactions between them were observed. [ABSTRACT FROM AUTHOR]

The ratio of monounsaturated oleic fatty acid to polyunsaturated linoleic fatty acid (O/L) and the associated agronomic traits were profiled for local peanut ( Arachis hypogaea L.) cultivars and accessions in Botswana. The research was tested on 16 entries planted in four localities across the country. The average total oil yield of the genotypes studied was about 42.1% and there was no significant difference in total oil yield ( P < 0.05) across the four research sites and among all entries (accessions). The average mean O/L ratio for all entries was about 1.47. The highest was that of the locally improved variety, Peolwane (2.58), which was significantly different ( P < 0.05) from all other accessions, and the lowest is that of the local accession GO 63 (1.23). This study also profiled the agronomic yield traits to identify genotypes that have both high oil quality and high yielding potential. No correlation was detected between pod yield and O/L ratio among the tested genotypes. The station with little rainfall but adequate repartition showed a very high O/L ratio for some genotypes, and future work is recommended to test this interesting observation on the correlation between moisture stress and oil quality. [ABSTRACT FROM AUTHOR]

The collection of Cola nitida in Côte d’Ivoire was previously classified, based on isozyme markers, into three groups named A, B and C, based on isozymic differences. In this study, morphological traits and several yield components as well as genotypic and phenotypic variabilities for vigour were investigated in groups A and B. We found that group A was characterized by a low vigour and high yield components. In contrast, group B expressed high vigour and low yield components. Intergroup hybrids were more vigorous and high yielder than intragroup hybrids. The vigour of intergroup hybrids was comparable to that of half sib commercial hybrids. Value of heterosis obtained for the yield of intergroup hybrids was 350%. It was concluded, based on our findings, that reciprocal recurrent selection in Cola nitida using plant materials of groups A and B should lead to significant improvement. [ABSTRACT FROM AUTHOR]

Genotype-by-environment interactions (GEIs) can affect breeding progress because they often complicate the evaluation and selection of superior genotypes. This drawback can be reduced by gaining insights into GEI processes and genotype adaptation. Here, we have studied the GEIs over a set of 24 barley genotypes that were grown across six environments (location-by-year combinations) in Sardinia, Italy. Three groups of genotypes were analysed: barley landraces (LANs), recombinant inbred lines (RILs), and commercial varieties (VARs). The additive main effects and multiplicative interaction (AMMI) model was used for data analysis, and results evidenced no significant differences in grain yield averages for the 24 genotypes. However, there was a relevant GEI for yield mainly between two of the six environments (one characterised by warm pre-anthesis period and high spring rainfalls, and the other characterised by opposite features) and two groups of genotypes (VAR and LAN). Moreover, a negative trade-off between yield levels of genotypes was seen when the barley genotypes were grown in the contrasting environments. Overall, intermediate GEI levels were seen for RILs in comparison to LANs and VARs, and some of the RILs provided valuable yield levels (e.g. RILs 23 and 52). The results thus show the potential usefulness of LANs as a genetic resource for breeding, e.g. to obtain genotypes adapted to Mediterranean environments, such as the RILs analysed in this study. [ABSTRACT FROM AUTHOR]

Crop simulation models of plant processes capture the biological interactions between the sensing of signals at an organ level (e.g. drought affecting roots), the response of the plant at a biochemical level (e.g. change in development rate) and the result at the organ (or crop) level (e.g. reduced growth). In dissecting the complex control of phenotypes like yield, simulation models have several roles. Models have been used to generate an index of the climatic environment (e.g. of drought stress) for breeding programme trials. In wheat and sorghum grown in northern Australia, this has shown that mid-season drought generates large genotype by environment interaction. By defining gene action to calculate the value of input trait parameters to crop models, simulated multi-environment trials estimate the yield of ‘synthetic’ sorghum cultivars grown in historical or artificial climates with current or potential management regimes. In this way, the biological interactions among traits constrain the crop yields to only those that are biologically possible in the given set of environments. This allows the construction of datasets that are more ‘realistic’ representations of gene by trait by environment interaction than is possible using only the statistical attributes (e.g. means, variances and correlations) of real-world trait datasets. This approach has an additional advantage in that ‘biological and experimental noise’ can be manipulated separately. These ‘testbeds’ for statistical techniques can be extended to the interpretation of a crossing and selection programme where the processes of chromosomal recombination are simulated using a quantitative genetics model and applied to the trait parameters. Statisticians are challenged to develop improved methods for the resulting simulated phenotype datasets, with the objective of revealing the (known) underlying genetic and environment structure that was input to the simulations. These improved methods can then be applied to existing plant breeding programmes. [ABSTRACT FROM AUTHOR]

Samba Mahsuri (BPT5204) is a medium slender grain indica rice variety that is very popular with farmers and consumers across India because of its high yield and excellent cooking quality. However, the variety is susceptible to several diseases and pests, including bacterial blight (BB). We have used PCR based molecular markers in a backcross-breeding program to introgress three major BB resistance genes ( Xa21, xa13 and xa5) into Samba Mahsuri from a donor line (SS1113) in which all the three genes are present in a homozygous condition. At each backcross generation, markers closely linked to the three genes were used to select plants possessing these resistance genes (foreground selection) and microsatellite markers polymorphic between donor and recurrent parent were used to select plants that have maximum contribution from the recurrent parent genome (background selection). A selected BC4F1 plant was selfed to generate homozygous BC4F2 plants with different combinations of BB resistance genes. The three-gene pyramid and two-gene pyramid lines exhibited high levels of resistance against the BB pathogen. Under conditions of BB infection, the three-gene pyramid lines exhibited a significant yield advantage over Samba Mahsuri. Most importantly, these lines retain the excellent grain and cooking qualities of Samba Mahsuri without compromising the yield as determined in multi-location trials. This work demonstrates the successful application of marker-assisted selection for targeted introgression of multiple resistance genes into a premium quality rice variety. [ABSTRACT FROM AUTHOR]

The role of pollen–stigma interaction and pollen tube growth as a measure of genetic compatibility was studied in eleven clones of cashew under a tropical rainforest ecology in Southwestern Nigeria between 1999 and 2002. Diallel cross of the clones showed that 55.00% of the cross-pollinated crosses showed high pollen cross-compatibility (CC) indicating moderate genetic distance in the population. About 54.55% of the clones showed evidence of self-compatibility, therefore confirming that cashew is self-fertile. Cytological examination however suggests possible postzygotic self-incompatibility in the crop as no evidence of tube growth inhibition was recorded in both cross- and self-pollinated styles. Correlation between maternal compatibility (pollen recipients) and fruit set shows that more attention need to be focused in this direction during selection. Based on the data from this study, the use of combinations of floral quality characteristics like high pollen fertility, prolific flowering, and high flower sex ratio plus high cross-compatibility as reliable selection criteria for cashew yield improvement is therefore suggested. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare nonparametric stability procedures and apply different nonparametric tests for genotype × environment (G × E) interactions on grain yields of 15 durum wheat genotypes selected from Iran/ICARDA joint project grown in 12 environments during 2004–2006 in Iran. Results of nonparametric tests of G × E interaction and a combined ANOVA across environments indicated the presence of both crossover and noncrossover interactions, and genotypes varied significantly for grain yield. In this study, high values of TOP (proportion of environments in which a genotype ranked in the top third) and low values of sum of ranks of mean grain yield and Shukla’s stability variance (rank-sum) were associated with high mean yield. The other nonparametric stability methods were not positively correlated with mean yield but they characterized a static concept of stability. The results of correlation analysis indicated that only TOP and rank-sum methods would be useful for simultaneous selection for high yield and stability. These two methods identified lines Mrb3/Mna-1, Syrian-4 and Mna-1/Rfm-7 as genotypes with dynamic stability and wide adaptation. According to static stability parameters, the genotypes 12A-Mar8081 and 19A-Mar8081 with lowest grain yield were selected as genotypes with the highest stability. [ABSTRACT FROM AUTHOR]

Compared to grain sorghums, sweet sorghums typically have lower grain yield and thick, tall stalks which accumulate high levels of sugar (sucrose, fructose and glucose). Unlike commercial grain sorghum ( S. bicolor ssp. bicolor) cultivars, which are usually F1 hybrids, commercial sweet sorghums were selected as wild accessions or have undergone limited plant breeding. Although all sweet sorghums are classified within S. bicolor ssp. bicolor, their genetic relationship with grain sorghums is yet to be investigated. Ninety-five genotypes, including 31 sweet sorghums and 64 grain sorghums, representing all five races within the subspecies bicolor, were screened with 277 polymorphic amplified fragment length polymorphism (AFLP) markers. Cluster analysis separated older sweet sorghum accessions (collected in mid 1800s) from those developed and released during the early to mid 1900s. These groups were emphasised in a principle component analysis of the results such that sweet sorghum lines were largely distinguished from the others, particularly by a group of markers located on sorghum chromosomes SBI-08 and SBI-10. Other studies have shown that QTL and ESTs for sugar-related traits, as well as for height and anthesis, map to SBI-10. Although the clusters obtained did not group clearly on the basis of racial classification, the sweet sorghum lines often cluster with grain sorghums of similar racial origin thus suggesting that sweet sorghum is of polyphyletic origin within S. bicolor ssp. bicolor [ABSTRACT FROM AUTHOR]

Low soil phosphorus (P) has been singled out as a major constraint leading to perpetually low bean ( Phaseolus vulgaris L.) grain yield far below the expected yield potential. In developing countries beans are mainly produced by small-scale farmers who have little capacity to use inorganic fertilizers to replenish their soils. Yet bean production contributes significantly to their income and provides a cheap source of protein to rural and urban populations. The genetics of inheritance of the traits conferring low soil P tolerance is not well understood. The identification and understanding of the mode of inheritance of the traits for P-efficiency in bean will go along way in boosting bean yields through development of varieties adapted to low soil P. The objective of this study was to determine the inheritance of the traits conferring adaptation to low soil P, for the important large seeded red mottled bean market class. Three parents with known tolerance to low soil P were crossed with five adapted but non-tolerant genotypes in an 8 × 8 half diallel mating scheme. The resulting F1 seeds were evaluated under medium and low soil P conditions at two locations. Both general combining ability (GCA) and specific combining ability (SCA) variances were highly significant ( P ≤ 0.01) for all five characters studied except SCA variance for root dry weight at one location. The magnitude of GCA variance was up to twelve times higher than the SCA variance. The GCA:SCA ratio varied from 0.62 to 0.96 for the characters studied. The additive genetic variance was more important than the dominance variance for tolerance to low soil P. [ABSTRACT FROM AUTHOR]

Twelve field experiments comparing 24 durum wheat varieties from three periods—old (<1945), intermediate (1950–1985) and modern (1988–2000)—were carried out in order to ascertain the advances made in durum wheat yield components and related traits in Italian and Spanish germplasm. Grain yield improvements were based on linear increases in the number of grains per m2 and harvest index, while grain weight and biomass remained unchanged. Yield per plant increased at a rate of 0.36 and 0.44% y−1 and the number of grains per m2 improved by 39% and 55% in Italian and Spanish varieties, respectively. The mean rate of increase in the number of grains per m2 was 0.55% y−1. Plants per m2, spikes per plant and grains per spike contributed 20%, 29% and 51%, respectively, to the increase in the number of grains per m2. The enhance of the number of grains per m2 was due to the greater grain set in the modern varieties, since the number of spikelets per spike remained unchanged. Harvest index increased overall by 0.48% y−1 (0.40 and 0.53% y−1 in Italian and Spanish varieties, respectively). Plant height was the trait that suffered the most dramatic changes (it decreased at a rate of −0.81% y−1, with little difference between the varieties of the two countries), as consequence of the presence of the Rht-B1 dwarfing gene. Harvest index and plant height, which were the traits that most contributed to discriminating between periods, remained unchanged from 1980 to 2000. The higher rates of improvement in Spain are discussed in the context of the contrasting strategies followed to improve durum wheat yield in the two countries. [ABSTRACT FROM AUTHOR]

The plant characteristics required to make wheat lodging-proof for the least investment of biomass are calculated using a validated model of the lodging process and information about the dry matter costs of altering lodging-associated characters. The plant characteristics required to give a crop yielding 8 t ha−1 with 500 shoots m−2 and 200 plants m−2, a lodging return period of 25 years include a height of 0.7 m, a root plate spread of 57 mm, and for the bottom internode a wall width of 0.65 mm with a diameter/material strength combination ranging from a diameter of 5.86 mm with a material strength of 20 MPa to a diameter of 4.00 mm with a material strength of 50 MPa. It is estimated that this ideotype would require 7.9 t ha−1 of stem biomass and would have a harvest index of 0.42. Observations of a wide range of varieties grown using crop management to maximise lodging resistance without reducing yield potential showed that the root plate of the best variety was 7 mm less than the ideotype target, the stem character targets were achieved but not all in one variety, and the height target was achievable with the use of plant growth regulators. Plant breeders must therefore focus on selecting for a wider root plate and combining the appropriate stem strength characteristics. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) cultivars for the warm regions of South Asia must produce high yields and possess resistance to spot blotch (Cochliobolus sativus), early maturity and high kernel weight. A study was conducted to determine the effectiveness of selecting for high grain yield based on a selection index for spot blotch resistance, maturity and kernel weight in four wheat crosses involving a susceptible cultivar and resistant genotypes. Initial selection of 40 progeny lines in each cross had been made using a selection index based on disease severity, days to heading and kernel weight as reported by Sharma and Duveiller [Crop Sci 43 (2003) 2031]. The five highest grainyielding progeny lines from among the 40 lines in each cross, their parents and five popular commercial cultivars were evaluated in field trials at two sites in Nepal in the 2002 and 2003 wheat seasons. Multiple spot blotch assessments were made to determine the area under disease progress curve (AUDPC). Grain yield, thousand kernel weight (TKW), days to heading and plant height were examined. The wheat genotypes in the farmer's field were also ranked on the basis of cultivar preference criteria by the local farmers. The 20 progeny lines always showed a higher (+11 to+125%) grain yield and heavier (+10 to+44%) kernels than their parents and a lower (-83 to-89%) AUDPC than the susceptible parent. The progeny lines showed 98-100% grain yield, 97-100% TKW and 66-78% AUDPC compared to the highest grain-yielding commercial cultivar. Based on the farmers' preference criteria for a desirable wheat genotype, the best progeny lines ranked from 3rd to 5th, whereas the two commercial cultivars ranked 1st (Gautam) and 2nd (BL 1473). Results indicated that selection was effective in combining adaptation genes present in a local cultivar with some level of tolerance to spot blotch and resistance genes from exotic genotypes, which translated into improved agronomic performance and disease resistance. The selection index and farmer participatory approach used in this study could serve as a guideline in breeding efforts targeted for high yielding genotypes for wheat-growing conditions in South Asia where spot blotch is a serious biotic constraint to yield. [ABSTRACT FROM AUTHOR]

The objectives of this research were to study the association in bread wheat between spectral reflectance indices (SRIs) and grain yield, estimate their heritability, and correlated response to selection ( CR) for grain yield estimated from SRIs under reduced irrigation conditions. Reflectance was measured at three different growth stages (booting, heading and grainfilling) and five SRIs were calculated, namely normalized difference vegetation index (NDVI), simple ratio (SR), water index (WI), normalized water index-1 (NWI-1), and normalized water index-2 (NWI-2). Three field experiments were conducted (each with 30 advanced lines) in three different years. Two reduced irrigation environments were created: (1) one-irrigation level (pre-planting), and (2) two-irrigation level (pre-planting and at booting stage), both representing levels of reduced moisture. Maximum yield levels in the experimental zone were generally obtained with 4–6 irrigations. Genotypic variations for all SRIs were significant. Three NIR (near infrared radiation) based indices (WI, NWI-1, and NWI-2) gave the highest level of association (both phenotypic and genotypic) with grain yield under both reduced irrigation environments. Use of the mean SRI values averaged over growth stages and the progressive integration of SRIs from booting to grainfilling increased the capacity to explain variation among genotypes for yield under these reduced irrigation conditions. A higher level of broad-sense heritability was found with the two-irrigation environment (0.80) than with the one-irrigation environment (0.63). Overall, 50% to 75% of the 12.5% highest yielding genotypes, and 50% to 87% of the 25% highest yielding genotypes were selected when the NWI-2 index was applied as an indirect selection tool. Strong genetic correlations, moderate to high heritability, a correlated response for grain yield close to direct selection for grain yield, and a very high efficiency of selecting superior genotypes indicate the potential of using these three SRIs in breeding programs for selecting increased genetic gains in grain yield under reduced irrigation conditions. [ABSTRACT FROM AUTHOR]

Total reliance on herbicides for weed control is unsustainable with the spread of herbicide resistance and the environmental need to reduce pesticide use. Strongly competitive wheat crops that have high tolerance to weed pressure and therefore maintain high yields in the presence of weeds are a low-cost option for reducing dependence on herbicides. We examined the feasibility of selecting for wheat tolerance to weeds by crossing varieties differing for traits associated with competitiveness. Competitive ability and yield potential must be treated as separate traits for selection. Current measures of crop tolerance to weed competition do not separate the two traits so that selection based on these measures is often synonymous with selection for yield potential rather than pure tolerance. We propose a new measure, termed Incremental Crop Tolerance (ICT) that reflects the incremental yield difference between genotypes associated with tolerance, over and above differences in underlying yield potential. [ABSTRACT FROM AUTHOR]

The effects of inbreeding were studied in three oil palm ( Elaeis guineensis Jacq.) trials in the Democratic Republic of Congo (Congo). In selfings, marked inbreeding depression was observed for yield of fruit bunches, mean bunch weight and bunch number, but there was little effect on bunch composition. Most vegetative measurements were significantly affected by selfing, but leaf production rate and leaf area ratio were unaffected. Sib-crossing had less depressive effect than selfing, and in some families sib-crosses were superior to outcrosses. Where selection needs to be done within inbred families, our study suggests that leaf area ratio and bunch composition would be useful criteria. [ABSTRACT FROM AUTHOR]

Heterosis in hybrid wheat varieties produced using a chemical hybridising agent was assessed in field experiments. Hyno Esta and its parents were compared in factorial combinations of four-seed rates (25-300 seeds m-2) and two nitrogen fertilizer rates (0 and 200 kg N ha-1) in 2001/02 and again in 2002/03. Hyno Rista and Hyno Renta and their parents were compared at two-seed rates in 2001/02. Hyno Rista and its parents were added factorially to the Hyno Esta experiment in 2002/03, while Hyno Renta and Hybred and their parents were compared at two seed rates in 2002/03. Mid parent heterosis for grain yield was found in three hybrids and two of these showed high parent heterosis. High parent heterosis in Hyno Esta over a range of sowing densities was mostly exhibited in total biomass but also, in one of two years, in harvest index. High parent heterosis in Hyno Renta was associated more with harvest index than with biomass. The heterosis for biomass in Hyno Esta resulted from greater interception of photosynthetically active radiation (PAR) than the male parent, with better radiation use efficiency than the female parent. In both seasons Hyno Esta achieved grain numbers per ear at least as high as the high parent for this trait (Audace), and combined this with mean grain weights at least as heavy as the high parent for mean grain weight (Estica). Much of the increased biomass and grain yield in the hybrid came late in the season as high parent heterosis was expressed for both maximum grain filling rate and grain filling duration. Heterosis was higher when nitrogen was applied than when withheld; only greater at lower seed rates when expressed in proportionate terms (e.g. as a percentage of the parents), rather than in absolute terms (e.g. t ha-1); and greater in the year with the cooler and wetter summer. [ABSTRACT FROM AUTHOR]

Vernonia galamensisis a wild plant from the familyAsteraceaewhich is endemic to East Africa and has the potential to become a new oil crop for industrial uses. Its seed oil is rich in vernolic acid, a fatty acid of high interest for oleochemical applications. However, a breeding program forVernonia galamensiscultivars with high seed and oil yields requires knowledge about the genetic variability of traits that influence seed and oil production. This study was undertaken to examine phenotypic and genotypic variability, broad-sense heritability, genetic advance under selection and interrelationships of agronomic and seed quality traits. A total of 122Vernoniaaccessions, 115 collected from different regions of Ethiopia and seven introduced, were grown at two locations in Ethiopia (Alemaya and Babile), in 2001/2002 and were analyzed for 20 traits including phenology, yield, yield components, and seed quality with special emphasis on fatty acid composition. The collections exhibited significant variation for all traits except for days to emergence. Genotypes and locations interacted significantly (P= 0.01) for all traits. Broad-sense heritability estimates ranged from 11% (for days to emergence) up to 79% (for days to maturity). Expected genetic advance was between 1.3% (for days to emergence) and 44.8% (for seed oil yield). Genetic correlation analysis revealed that seed yield per plant is highly and positively correlated with seed weight and head number; highly significant and negative correlations (r= -0.59, -0.82, -0.85, and -0.89) were found between vernolic acid and palmitic, stearic, oleic, and linoleic acid, respectively. Highly significant positive correlations (r= 0.55, 0.44, and 0.36) were observed between vernolic acid and oil content, meal protein content and seed oil yield, respectively. Path-coefficient analysis indicated seed weight and secondary head number to be the most important components of seed yield per plant. Vernolic acid, oleic acid and linoleic acid had positive direct effects and stearic acid had a negative direct effect on oil content. The direct positive effect of oleic acid on oil content was, however, compensated by the negative indirect effects of stearic and vernolic acid resulting in a negative correlation (r= -0.60) between oleic acid and oil content. These observations will support the selection of accessions with high seed and oil yield, high meal protein contents, and high vernolic acid content. [ABSTRACT FROM AUTHOR]

Traditionally, barley in Argentina has been cultivated in low-yielding environments. A study was conducted to test whether breeding for improved performance under these conditions would have also improved the responsiveness to nitrogen availability. Four cultivars of two-rowed malting barley (released in 1944, 1960, 1982 and 1998) were grown under 4 rates of nitrogen fertilizer at sowing (20, 50, 110 and 160 kgN ha-1). All cultivars increased their yield with the increase in soil nitrogen. But yield of modern cultivars responded more strongly than yield of old ones. For modern cultivars, increase in grain yield was of 12 ± 0.6 kg ha-1 for each 10 kg ha-1 of increase in the mean yield (environmental index). Absolute values of genetic gain were related to nitrogen availability: 1.59, 2.58, 4.52 and 4.29 g m-2 year-1 for the N20, N50, N110 and N160 treatments, respectively. Grain yield was associated with grain number m-2, which was dependent on spikes m-2 and grains spike-1. Total biomass at maturity also explained the changes in yield. It is concluded that selection under stress conditions was, in this case, beneficial to identify cultivars with high yields under a wide range of nitrogen availabilities. [ABSTRACT FROM AUTHOR]

Two generations of recurrent phenotypic selection for seed yield per plant under controlled pollination were carried out to combine improved seed yield with improved forage grass performance in perennial ryegrass (Lolium perenne L.). Selected and unselected varieties (AberDart and AberElan respectively) and control varieties were grown for seed in pots in a glasshouse experiment and in two field plot experiments over 5 harvest years. Seed yield components and seed yield were measured. Significant improvements in seed yield of the selected AberDart over the unselected AberElan were observed both in individual plants grown in the glasshouse and in field plots. Detailed observations of the individual components of seed yield showed that the increased seed yield of AberDart can be attributed to a higher proportion of ovules forming seeds (% seedset), greater seed number per tiller and more reproductive tillers per plant. This improvement in seed yield of AberDart was also observed when it was grown in field plots with AberElan, experimental selection lines and commercial varieties. AberDart produced more seeds per tiller than the other commercial varieties and selection lines studied. The implication of this approach for the breeding of perennial ryegrass varieties that combine good agronomic performance and acceptable seed yields is discussed. [ABSTRACT FROM AUTHOR]