Variability is an important factor to consider in crop improvement programmes. This study was conducted in two years to assess genetic variability and determine relationship between seed yield, its components and tuber production characters among twelve accessions of African yam bean. Data collected were subjected to combined analysis of variance (ANOVA), Principal Component Analysis (PCA), hierarchical and K-means clustering analyses. Results obtained revealed that genotype by year (G × Y) interaction had significant effects on some of variables measured (days to first flowering, days to 50 % flowering, number of pod per plant, pod length, seed yield and tuber yield per plant) in this study.The first five principal components (PC) with Eigen values greater than 1.0 accounted for about 66.70 % of the total variation, where PC1 and PC 2 accounted for 39.48 % of variation and were associated with seed and tuber yield variables. Three heterotic groups were clearly delineated among genotypes with accessions AY03 and AY10 identified for high seed yield and tuber yield respectively. Nonsignificant relationship that existed between tuber and seed yield per plant of these accessions was recommended for further test in various agro-ecologies for their suitability, adaptability and possible exploitation of heterosis to further improve the accessions. Variabilnost je zelo pomemben dejavnik v žlahtnenjenju poljščin. Dvoletna raziskava je bila opravljena s ciljem ovrednotenja genetske variabilnosti in analize odnosov med komponentami pridelka semena ter tvorbe in značilnosti gomoljev med 12 akcesijami afriškega gomoljastega fižola. Zbrani podatki so bili obdelani z analizo variance (ANOVA), analizo glavnih komponent (PCA), hierarhično in klastersko analizo. Izsledki so pokazali, da so imele interakcije med genotipi in leti (G × Y) statistično značilen vpliv na nekatere analizirane spremenljivke kot so dnevi do prvega cvetenja, dnevi do 50 % cvetenja, število strokov na rastlino, dolžina stroka ter pridelek semen in gomoljev na rastlino. Prvih pet glavnih component (PC) z lastnimi vrednostmi več kot 1.0 je prispevalo 66.70 % celokupne variabilnosti, PC1 in PC 2 pa sta pridali še 39.48 % variabilnosti v povezavi s pridelkom semena in gomoljev. Med genotipi so se jasno oblikovale tri heterotične skupine in akcesija AY03 je bila prepoznana po velikem pridelku semen, AY10 pa po velikem pridelku gomoljev. Neznačilno povezavo med pridelkom semen in gomoljev pri teh akcesijah bi bilo priporočljivo dodatno testirati glede prilagodljivosti na različne agroekološke razmere, možnosti njihovega izboljšanja in potencialne uporabe heterotičnega učinka.

Q11Effect of seed size on in vitro seed germination, seedling growth, embryogenic callus induction and plantlet regeneration from embryo of maize (Zea mays L.) seed Q8 Abstract Immature embryo-derived callus is more efficient for plant regeneration in maize but it is difficult to obtain all seasons of the year while mature embryos from dry seeds are available throughout the year. This study attempts to investigate the effect of seed size on in vitro seed germination, seedling growth, callus induction and plantlet regeneration, as well as the relationships between these parameters in five maize varieties. Seeds were designated as large or small for each variety based on their 100 seed weights and seed germination were achieved in petridishes between two sheets of pre-wetted filter paper. Seeds were disinfected and mature embryos were excised from the maize endosperm and inoculated on the Murashige and Skoog salt (MS medium) supplemented with 30 g/l sucrose, 8 g/l agar, 0.1 g/l myo-inositol and 3 mg/l 2,4-D for callus induction, while embryogenic calli were transferred to medium containing 0.5 mg/l Benzylaminopurine (BAP) and 0.5 mg/l Kinetin for plant regeneration. The study showed that large seeds had significant effect on almost all the traits studied and positive correlation was observed between in vitro germination, seedling growth, callus induction and plantlet regeneration. It can be concluded that callus fresh weight can be used as a marker for improving regeneration efficiency in maize. These results can be used to enhance research into the genetic control of in vitro regeneration from maize mature embryo in the future breeding programs to determine inherent genetic potentials of maize varieties with good tissue culture traits.

The genetic diversity of 40 African yam bean (AYB) accessions was assessed using amplified fragment length polymorphism (AFLP) markers. Seeds of 40 accessions of AYB obtained from the International Institute of Tropical Agriculture (IITA) and Institute of Agricultural Research and Training (IAR&T) Ibadan, Nigeria, were grown in a greenhouse and young leaves from two weeks old plants collected for DNA extraction. The four primer combinations used generated a total of 1730 amplification fragments across the AYB accessions used in this study of which 1647 were polymorphic (95.20%). The number of amplified polymorphic AFLP bands per primer pair varied from 360 to 520 with an average percentage polymorphism of 95.6%. E-AGC/M-CAG produced the highest number of polymorphic bands (520). Polymorphic information content (PIC) values ranged from 0.9447 to 0.9626. The highest level of polymorphism (100%) was recorded for two primer combinations (E-AAC/M-CAG and E-ACT/M-CAG). The results of cluster analysis using UPGMA tree, grouped the 40 accessions of AYB into two major clusters with an overall similarity of 67.5%. The level of similarity between the accessions spanned 0.66 to 0.91. TSs 138 and TSs 139 were the most closely related accessions with high level of similarity index (0.91). Comparable results were obtained using Factorial Coordinate Analysis (FCO). The results from the present study confirm the robustness and the suitability of the AFLP as a molecular tool for the assessment of genetic diversity in AYB accessions.

Genetic linkage maps provide a genomic framework for quantitative trait loci identification applied in marker assisted selection breeding in crops with limited resources. It serves as a powerful tool to breeders for analysing the mode of inheritance of genes of interest and monitoring of the transmission of target genes from parents to progeny. Single nucleotide polymorphism (SNP) markers have a great influence on mapping research studies: for faster development of new varieties of crops due to its abundance and high number of polymorphism. Thus, this research work aimed at constructing genetic linkage map of cowpea using SNP markers. This will facilitate development of new varieties of cowpea. Single seed descent method of breeding was used to generate mapping population between IT-95K-193-12 and Ife-Brown. Fresh leaves from both parental lines and F1 hybrids were genotyped with 135 SNP markers. Data from125 polymorphic SNP markers were used to construct linkage map. Results revealed 12 linkage maps with an average of 10 markers to a chromosome and average marker distance of 3.02 cM between the markers. Constructed map provides basic information that could assist in genetic improvement of cowpea, most especially in developing brown blotch resistant cowpea varieties through detection of quantitative trait loci (QTL) responsible for brown blotch resistance in cowpea when utilizing marker assisted selection method.

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