Morphological Diversity and Cytological Studies in Some Accessions of Vigna vexillata (L.) A. Richard

Aim: The objectives of this study were to characterize and evaluate intraspecific relationship among twenty-six accessions of Vigna vexillata (L.) and work out interrelationship among the morphological traits which could be used for genetic improvement of cowpea, V. unguiculata (L.) Walp. Study Design: Field experiment was laid out in blocks of five buckets per accession in a row giving a total of 260 plants. Place and Duration of Study: At the experimental field of the Department of Biological Sciences, Covenant University, Ota, Ogun state, Nigeria, during the dry planting season (September – December, 2012). Methodology: A total of 26 traits comprising 18 quantitative and 8 qualitative traits of the vegetative, floral, pod and seed were evaluated using descriptive statistics, Pearson Correlation Coefficient (PCC), Principal Component Analysis (PCA) and Cluster Analysis (CA). Mitotic chromosome counts and meiotic behaviour were studied using root tip cells and pollen mother cells from young flower buds. Results: The analysis of variance showed that all quantitative morphological characters were significantly different among the accessions (P = 0.01) except stipule length and width. There were significant correlations among characters such as calyx lobe length, standard petal length and width, peduncle length, days to 50% flowering, days to 50% pod maturity, pod length and width, number of locules per pod, number of seeds per pod, and 100-seed weight which could be used for breeding and conservation purposes. The first six principal components accounted for 89.84% of the total variance. The cluster analysis segregated the 26 accessions into three main clusters; cluster I (15 accessions), cluster II (10 accessions) and cluster III (1 accession). Mitotic chromosome counts of 2n = 22 were recorded for all the accessions and meiosis was observed to be normal with the formation of eleven bivalents (n = 11). Conclusion: The intraspecific variabilities indicates plasticity in the genomes of the studied accessions, with high correlations among the morphological characters which are common to all accessions, thus justifying their grouping as a species. The morphological and reproductive attributes displayed by accessions TVnu93 and TVnu97 in terms of plant vigour, early flowering and pod maturity, longer pods and relatively high 100-seed weight made them good potential candidates in breeding for host plant resistance in cowpea

Selection for resistance to cassava mosaic disease in African cassava germplasm using single nucleotide polymorphism markers

Cassava mosaic disease (CMD) is one of the main constraints that hamper cassava production. Breeding for varieties that are CMD resistant is a major aim in cassava breeding programmes. However, the use of the conventional approach has its limitations, including a lengthy growth cycle and a low multiplication rate of planting materials. To increase breeding efficiency as well as genetic gain of traits, SNP markers can be used to screen and identify resistant genotypes. The objective of this study was to predict the performance of 145 cassava genotypes from open-pollinated crosses for CMD resistance using molecular markers. Two SNP markers (S12_7926132 and S14_4626854), previously converted into Kompetitive allele-specific PCR (KASP) assays, as well as CMD incidence and severity scores, were used for selection. About 76% of the genotypes were revealed to be resistant to CMD based on phenotypic scores, while over 24% of the total population were found to be susceptible. Significant effects were observed for alleles associated with marker S12_7926132 while the other marker had nonsignificant effects. The predictive accuracy (true positives and true negatives) of the major CMD2 locus on chromosome 12 was 77% in the population used in this study. Our study provides insight into the potential use of marker-assisted selection for CMD resistance in cassava breeding programmes. Significance:• With an aim towards reducing the food insecurity rate in Africa, we report on the use of genetic tools for a fast and efficient release of new cassava varieties to benefit breeders, farmers and consumers, given the food and industrial importance of this staple crop.• This study adds tremendous knowledge to phenotypic and molecular screening for CMD resistance. The outcome will encourage breeders in various cassava breeding programmes to accelerate genetic gains as well as increase breeding accuracy and efficiency for CMD resistance

Molecular and phenotypic profiling of white Guinea yam (Dioscorea rotundata) breeding lines

Phenotypic and genotypic profiling helps identify genotypes with suitable and complementary traits for genetic improvement in crops. A total of 32 traits were assessed in 36 genotypes of white Guinea yam established in a 6 × 6 triple lattice design. The objective was to evaluate an array of plant traits that define the genetic merits of breeding lines for yam improvement. Different analytical tools were used to identify and prioritize relevant traits defining the genetic merits of breeding lines in the yam improvement program. Out of the 32 traits measured, the linear combination of 14 traits that minimize within-group variance and maximize between-group variance for discriminating the genetic values of yam breeding lines were identified. When best linear unbiased prediction with genomic relationship matrix (GBLUP) was used, the accuracies of genomic breeding values were higher (r=0.87 to 0.97) for the seven traits (dry matter content, intensity of flesh oxidization of shredded tuber, pasting temperature, pasting time, tuber flesh colour, yam mosaic virus and fresh tuber yield) with high broad-sense heritability values (H2m>0.6). While, for the remaining seven traits with low (H2m<0.3) to medium (H2m=0.3 to 0.54) broad-sense heritability values, the accuracies of genomic estimated breeding values (GEBV) were low (r<0.4) to medium (r=0.4-0.8). The genotype–trait (GT) biplot display revealed superior clones with desirable genetic values for the key traits. These results are relevant for parental selection aimed at improving key agronomic traits in white Guinea yam

Genome analyses reveal the hybrid origin of the staple crop white Guinea yam (Dioscorea rotundata)

西アフリカの主食作物ギニアヤムの起源を解明 --ギニアヤムはサバンナと熱帯雨林に生育する野生種の雑種起源--. 京都大学プレスリリース. 2020-12-11.White Guinea yam (Dioscorea rotundata) is an important staple tuber crop in West Africa. However, its origin remains unclear. In this study, we resequenced 336 accessions of white Guinea yam and compared them with the sequences of wild Dioscorea species using an improved reference genome sequence of D. rotundata. In contrast to a previous study suggesting that D. rotundata originated from a subgroup of Dioscorea praehensilis, our results suggest a hybrid origin of white Guinea yam from crosses between the wild rainforest species D. praehensilis and the savannah-adapted species Dioscorea abyssinica. We identified a greater genomic contribution from D. abyssinica in the sex chromosome of Guinea yam and extensive introgression around the SWEETIE gene. Our findings point to a complex domestication scenario for Guinea yam and highlight the importance of wild species as gene donors for improving this crop through molecular breeding

Farming practices, varietal preferences, and land suitability analyses for yam production in Eastern D.R. Congo: implications for breeding initiatives and food sovereignty

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

List of SNP markers for Genomic prediction

We described the methodology used to select highly informative SNP markers to be used for genomic selection and prediction for yam </p

Hapmap genotypic data

THIS IS HAPMAP FILE </p

Phenotypic and genotypic data data

Phenotypic and genotypic data</p