The identification of suitable parental genotypes potentially generating superior lines with traits contributing to the overall yield of cowpea is an important step in the development of improved varieties. Eight parents and their 28 hybrids obtained through diallel crossing design were evaluated in a randomized complete block design with three replications. Highly significant differences among the parents and their hybrids for different traits were observed. General combining ability (GCA) mean squares were larger than the specific combining ability mean squares for all the traits analysed. The ratio h²/H₂ revealed different number of genes controlling the traits, pointing out their polygenic inherited control. The estimated low narrow sense heritability recorded in this study indicated that recurrent selection procedure could be effective to improve the analysed traits in the genotypes included in this study. Kananado with large, positive and significant GCA effects was identified as the parent with desirable genes for the genetic improvement of the considered yield component in cowpea. In addition, IT03K-316-1 x Cowpea-2 and IT99K-316-2 x Kananado seemed to be the best hybrids for number of pods/plant and 100-seed weight, respectively

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Identification of genes associated with Striga resistance is invaluable for accelerating genetic gains in breeding for Striga resistance in maize. We conducted a genome-wide association study (GWAS) to identify genomic regions associated with grain yield and other agronomic traits under artificial Striga field infestation. One hundred and forty-one extra-early quality protein maize (QPM) inbred lines were phenotyped for key agronomic traits. The inbred lines were also genotyped using 49,185 DArTseq markers from which 8,143 were retained for population structure analysis and Genome Wide-Association Study (GWAS). Cluster analysis and population structure revealed the presence three well defined genetic groups. Using the mixed linear model, twenty-two SNP markers were identified to be significantly associated with grain yield, Striga damage at 10 weeks after planting (WAP), number of emerged Striga plants at 8 and 10 WAP and ear aspect. The identified SNP markers would be useful for breeders for marker-assisted selection (MAS) to accelerate genetic enhancement of maize for Striga resistance in sub-Saharan Africa after validation.

Recurrent drought and Striga hermonthica (Del.) Benth parasitism constrains maize production in sub-Saharan Africa (SSA). Transfer of resistance genes from wild relatives can improve resistance to drought and Striga in tropical maize. The objectives of this study were to (i) determine the combining ability of 12 extra-early yellow maize inbreds derived from Zea diploperennis and tropical maize germplasm; (ii) classify the inbreds into heterotic groups using heterotic grouping based on the general combining ability (GCA) of multiple traits (HGCAMT) method; (iii) examine hybrid performance under contrasting environments; and (iv) examine the stability of hybrid combinations involving the inbreds. Sixty-six diallel crosses involving the inbreds plus four checks were evaluated for two years under drought, Striga-infested and rainfed environments in Nigeria. Significant differences (p < 0.05) were observed for the effects of genotype, environment, genotype × environment, GCA and specific combining ability (SCA) on grain yield and other measured traits. Inbred lines such as TZdEEI 7 × TZEEI 63 derived from Z. diploperennis and tropical germplasm exceeded the checks by a range of 28 to 41%. Across environments, the hybrid TZdEEI 1 × TZdEEI 7, which was derived from Z. diploperennis, was the highest-yielding with a grain yield of 4302 kg ha−1. The results revealed the predominance of GCA over SCA effects for most measured traits, suggesting that additive gene action governed the inheritance of Striga resistance and drought tolerance related traits in the inbreds. The 12 inbreds were classified into three heterotic groups, while TZEEI 79 and TZdEEI 7 were identified as inbred testers and TZdEEI 7 × TZEEI 12 as a single-cross tester across environments. Hybrid TZdEEI 9 × TZEEI 79 was the highest-yielding and most stable. Other promising hybrids were TZdEEI 7 × TZEEI 79, TZdEEI 1 × TZdEEI 7 and TZdEEI 12 × TZEEI 95. These hybrids should be extensively tested on-farm for potential commercialization in SSA. Overall, our results highlighted the importance of harnessing beneficial alleles from wild relatives of maize for improvement of resistance to Striga and tolerance to drought in adapted maize germplasm.

Two experiments were conducted to evaluate ageing-induced genetic changes and to establish physiological thresholds for loss of genetic integrity during ageing or storage of rice seeds. In the first experiment, seeds of 10 varieties of rice were subjected to artificial ageing in chambers conditioned to 55°C and 72±2% RH for 72 hours. In the second experiment, seeds of 4 varieties of rice stored in the NACGRAB gene bank, Nigeria in 2011 at 5± 4°C were compared with seeds of the same accessions freshly harvested in 2013. Data were collected on seed germination and seedling length to estimate the seed vigour index. Genetic changes during the ageing were evaluated by SSR markers using a Direct™ PCR kit. Genetic distance indices were computed using PAST™ software and percentage genetic integrity was estimated from the genetic distance matrices. At 72 hours of artificial ageing, seed germination percentage declined to 54.2% and vigour index 0.8 coinciding with the lowest estimate of genetic integrity of 99.5%. The decline in percentage genetic integrity during the artificial ageing indicated a systematic ageing-induced genetic alteration. SSR primer RM178 revealed variations that suggest losses of alleles in the course of ageing for 2 accessions at between 24 hours in WITA4 and 48 to 51 hours in CG14. In the gene bank storage trial, germination of seeds after one and two years of storage was above 80% and there were no significant differences among the accessions. SSR profiles for all the accessions were also similar. The result partly corroborates the artificial ageing data. This implies that seed viability benchmark of 54% is recommended for regeneration of stored rice seeds in order to maintain optimum genetic integrity during storage.

Genetic similarities, which can be detected with phenotypic and molecular markers, are important for effective use of available germplasm. It provides information on genetic diversity for reliable gene recombination. Thirty accessions of amaranth were assessed for variation with 15 phenotypic characters and 10 random amplified polymorphic DNA (RAPD) primers. Significant (p < 0.05) phenotypic variation was observed among the accession at the vegetative phase and most of the accessions had leaves with green pigmentation. Sink factor such as leaf, stem and root weights, and dry matter, were homogenous traits which contributed significantly to diversity among the accessions. The RAPD primers produced 115 bands with 88 (77%) polymorphic loci. The DNA classification between some of the accessions was similar to the phenotypic diversity. Information on phenotypic diversity and traits contributing to the diversity can be used deductively with genetic diversity to guide effective hybrid program.

Direct selection based on pod yield is often a problem in West African okra (Abelmoschus caillei (A. Chev.) Stevels) breeding programs. Information on inter-relationships among traits to implement indirect selection for pod yield is needed. Objectives of this study were to evaluate the performance of West African okra varieties in two cropping seasons prevailing in Nigeria, and to determine the associations among main agronomic characters and their influence on pod yield. Twenty-five genotypes were grown in two planting seasons at the Research Farm of the Federal University of Agriculture, Abeokuta in 2008-2009 using a randomized complete-block design with three replications. Sixteen plant characters were measured. The data were subjected to variance, correlation and path analyses. Four genotypes, viz., CEN 010, CEN 012, NGAE-96-04 and AGA 97/066-5780 demonstrated potential for high pod yield. CEN 012 and AGA 97/066-5780 in addition, demonstrated early flowering higher number of pods. Character associations varied between planting seasons. The dependence of pod yield on final plant height, number of branches per plant, number of pods per branch, number of pods per plant, number of ridges per pod, weight of 250 seeds, pod length and seed weight per plant was noted in both planting seasons. In both seasons, number of pods per plant exhibited a high positive direct effect on pod yield. In conclusion, the trait of most interest for improving pod yield under early and late-season conditions was number of pods per plant