Search

Key message Analysis of the genetic architecture of MCMV and MLN resistance in maize doubled-haploid populations revealed QTLs with major effects on chromosomes 3 and 6 that were consistent across genetic backgrounds and environments. Two major-effect QTLs, qMCMV3-108/qMLN3-108 and qMCMV6-17/qMLN6-17, were identified as conferring resistance to both MCMV and MLN. Abstract Maize lethal necrosis (MLN) is a serious threat to the food security of maize-growing smallholders in sub-Saharan Africa. The ability of the maize chlorotic mottle virus (MCMV) to interact with other members of the Potyviridae causes severe yield losses in the form of MLN. The objective of the present study was to gain insights and validate the genetic architecture of resistance to MCMV and MLN in maize. We applied linkage mapping to three doubled-haploid populations and a genome-wide association study (GWAS) on 380 diverse maize lines. For all the populations, phenotypic variation for MCMV and MLN was significant, and heritability was moderate to high. Linkage mapping revealed 13 quantitative trait loci (QTLs) for MCMV resistance and 12 QTLs conferring MLN resistance. One major-effect QTL, qMCMV3-108/qMLN3-108, was consistent across populations for both MCMV and MLN resistance. Joint linkage association mapping (JLAM) revealed 18 and 21 main-effect QTLs for MCMV and MLN resistance, respectively. Another major-effect QTL, qMCMV6-17/qMLN6-17, was detected for both MCMV and MLN resistance. The GWAS revealed a total of 54 SNPs (MCMV-13 and MLN-41) significantly associated (P ≤ 5.60 × 10−05) with MCMV and MLN resistance. Most of the GWAS-identified SNPs were within or adjacent to the QTLs detected through linkage mapping. The prediction accuracy for within populations as well as the combined populations is promising; however, the accuracy was low across populations. Overall, MCMV resistance is controlled by a few major and many minor-effect loci and seems more complex than the genetic architecture for MLN resistance. Electronic supplementary material The online version of this article (10.1007/s00122-019-03360-x) contains supplementary material, which is available to authorized users.

Wheat (Triticum aestivum L) is the second largest contributor to food security in Kenya. However, water deficiency retards plant growth and productivity significantly. With few drought-tolerant varieties available, there is a need to develop more drought-tolerant wheat varieties. The objective of this study was to screen for drought tolerance in the mutant wheat lines at the seedling stage. Seeds of two wheat varieties were subjected to gamma radiation at an irradiation dose of 300 gy (gray). The mutants and two local varieties – Chozi and Duma (controls) were sown in polythene bags in a complete randomized design and screened for various seedling traits. Data were analyzed using ANOVA and Pearson correlation. Results indicated that Mutant 1 and Mutant 2 had high emergence percentage, emergence index, energy emergence, and percent seedling recovery compared to local varieties Chozi and Duma. Emergency percentage showed a positive correlation with the following parameters; emergence index (r = 0.965); Energy of emergency (r = 0.990) and Percentage seedling recovery (r = 0.941). It was recommended that the mutant wheat be screened for other biotic and abiotic stresses that affect wheat production in Kenya

Background: Sweetpotato, being a vegetatively propagated crop is prone to seed degeneration, and a continuous source for high quality sweetpotato seed is critical for an efficient seed system. In most Sub-Saharan African countries, the National Agricultural Research Systems use tissue culture to produce limited quantity of pre-basic sweetpotato seed which is then used as starting material to maintain and produce basic seed in mini-screen houses, net tunnels or open field multiplication in low-virus pressure areas by either the private seed companies or vine multipliers. Soil is the predominant media for pre-basic seed multiplication. Multiplying pre-basic sweetpotato seed in sand with fertigation, also known as ‘sandponics’ is a possible opportunity towards sustainable production of pre-basic sweetpotato seed. It would be beneficial to examine the feasibility and the potential to replace soil system with ‘sandponics’ for growing pre-basic sweetpotato seed. Methods: Pot experiments were conducted to study how sweetpotato vine propagation is affected by sequentially omitting nitrogen, phosphorus, calcium, sulfur and boron from fertilizer applications on cv. Kabode. The experiment was laid in a randomized complete block design with five levels of the factor fertilizer, replicated four times with two blocks. The effect of fertilization of nitrogen at (0, 100, 150, 200 & 250), phosphorus at (0, 30, 60, 90 & 120), calcium at (0, 100, 200, 300 & 400), sulfur at (0, 30, 60, 90 & 120) and boron at (0, 0.1, 0.2, 0.3 & 0.4) ppm on sweetpotato vegetative growth parameters was measured 45 days after planting. Results: The obtained results showed that application of 200, 60, 200, 120 and 0.3 ppm of N, P, Ca, S and B respectively recorded the highest values in sweetpotato vegetative growth parameters. Conclusions: These results imply that pre-basic sweetpotato vine yields in sandponics could be increased by using this optimized media.

Aims: Cassava (Manihot esculentaCrantz)is a crop with largely unexplored and unexplained potentially valuable genetic variability. The knowledge and understanding of the extent of genetic variation ofcassava germplasm is important for conservation and improvement. Objective:The current study was to investigate the genetic divergenceof cassava mutants, hybrids and landraces using simple sequence repeat (SSR) markers. Methodology: Genetic diversity o f ten cassava genotypeswas determined using 14 SSR markers. Results:Findings from this study showed that the dendrogram based on UPGMA cluster analysis revealedthat SSR data indicated the existence of high divergence among the accessions . The cophenetic matrices obtained showed that SSR data marker type wasr = 0.91. Conclusion: The wider genetic diversity observed using SSR markers would be valuable for efficient management of germplasm and for effective utilization of materials in breeding programmes to produce hybrids of desirable characteristics. The extensive genetic diversity is Original ResearchArticle

Artemisia annua is the source of artemisinin, an antimalarial drug which is effective against multidrug-resistant strains of plasmodium, the malarial parasite. Malaria has serious effects on morbidity and mortality thus negatively impacting on agricultural...