BackgroundCowpea is a highly inbred crop. It is part of a crop-weed complex, whose origin and dynamics is unknown, which is distributed across the African continent. This study examined outcrossing rates and genetic structures in 35 wild cowpea (Vigna unguiculata ssp. unguiculata var. spontanea) populations from West Africa, using 21 isozyme loci, 9 of them showing polymorphism.ResultsOutcrossing rates ranged from 1% to 9.5% (mean 3.4%), which classifies the wild cowpea breeding system as primarily selfing, though rare outcrossing events were detected in each population studied. Furthermore, the analyses of both the genetic structure of populations and the relationships between the wild and domesticated groups suggest possibilities of gene flow that are corroborated by field observations.ConclusionsAs expected in a predominantly inbred breeding system, wild cowpea shows high levels of genetic differentiation and low levels of genetic diversity within populations. Gene flow from domesticated to wild cowpea does occur, although the lack of strong genetic swamping and modified seed morphology in the wild populations suggest that these introgressions should be rare.

Genetic variation of quantitative traits is a prevalent characteristic among cultivated tomato varieties. Twenty tomato genotypes comprising indigenous varieties and commercial cultivars, cultured in the Western Region of Cameroon were evaluated using fourteen quantitative traits for disease resistance, phenotypic divergence and heritability estimates. The experiment was carried out using a randomized completed blocks design with three replications. Data collections were disease characteristics, plant development features and yield attributes. The analysis of variance revealed significant variation among genotypes for all the experimental quantitative traits. Hybrid varieties had significantly more fruit yield (1066.00 g/plant), single fruit weight (57.28 g), fruit diameter (4.47 cm) and pericarp thickness (0.54 cm) compared to standard and indigenous varieties. These indigenous varieties were significantly more resistant to late blight, alternaria leaf spot and viral diseases. They also had significantly higher collar diameter (16.30 mm), number of primary branches per plant (8.45), number of fruit per plant (31.58) and plant height (88.33 cm) compared to standard and hybrid plants. The genotype local 2 was the third most productive (1576.39 g / plant) after Rio Semagri (1984.80 g/plant) and Sakato F1 (1691.69 g/plant). Heritability and genetic advance estimates were high for twelve of the fourteen studied quantitative traits. Fruit yield showed significant positive correlations with single fruit weight and number of fruit per plant. However, significant negative correlation was found between fruit yield and time to 50 % flowering, 50 % fruiting, 50 % maturity and viral disease. The first three and the first four components in the principal component analysis explained, respectively, 77.85 % and 88.38 % of the total variation observed among genotypes. The first component determined 41.42 % of the total variation, dominated by the collar diameter, the number of primary branches per plant and plant height. This study clearly indicated that indigenous varieties are the most disease resistant genotypes and are having substantial fruit yield (945.30 g/plant) similar to standard varieties and at a touching distance to hybrid cultivars.

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KEYWORDS Phaseolus vulgarisEnzyme Allozyme Genetic diversity Genetic structure ABSTRACTIn order to provide essential information for plant breeding and crop improvement programs, genetic diversity assessment is a prerequisite. In this study, starch gel electrophoresis of 9 enzyme systems encoding 19 putative loci was used to assess allozyme diversity of 13 cultivated common bean (Phaseolus vulgaris) accessions from Cameroon and 21 from Kenya. Results of genetic variation among the studied accessions revealed 26.32% as proportion of polymorphic loci (P), 1.263 as average number of alleles per locus (A), 0.007 as observed heterozygosity (HO) and 0.079 as the total expected heterozygosity (HT). The level of genetic diversity within and among the various accessions were HS= 0.014 ± 0.003 and DST = 0.065 ± 0.013 respectively. G-statistics estimation indicated a high level of genetic heterogeneity between accessions (GST=0.825 ± 0.021), suggesting that cultivated P.vulgaris maintains about 82.5 % of its genetic variation among accessions. This distribution was more pronounced in Kenyan accessions (89.2 %) compared to Cameroonian accessions (69.9%). Important deviation from Hardy-Weinberg expectations was reported in this study (FIT = 0.903 ± 0.018). This genetic disequilibrium is likely due to either high genetic differentiation between accessions (FST=0.861 ± 0.023) or significant nonrandom mating within accessions (FIS = 0.233 ± 0.096). There was no significant gene flow among cultivated P.vulgaris accessions in Cameroon (Nm = 0.058 ± 0.029) and in Kenya (Nm = 0.045 ± 0.041).

Aerial yam (Dioscorea bulbifera L.) is a crop of great economic importance and an excellent candidate for improving food security in developing countries. Understanding the genetic variability of any crop species is a decisive step for its improvement and requires characterization and evaluation of available germplasm. The objectives of this study were to determine the extent of genetic variability, estimate the association between agromorphological traits and clustering among 57 genotypes of aerial yam from three distinct agro-ecological zones in Cameroon using multivariate analysis. Thirty nine characters (23 qualitative and 16 quantitative) were used for the study. Significant differences in genetic diversity indices were found. Accessions from the bimodal humid forest zone (Na = 2.08, He = 0.27) showed significantly lower diversity compared to both western highland (Na = 2.30, He = 0.34) and humid monomodal forest zones (Na = 2.57, He = 0.32). Means values of most quantitative traits also showed significant differences between agro-ecological zones. Batingla-3 and Bawouwoua-1 had important bulbil yield, reaching 3500 g / plant. Significant associations were found between many traits. The use of the Unweighted Pair Group Method with Arithmetic Mean allowed the distribution of the 57 genotypes into six distinct clusters with the clustering pattern not showing any parallelism with location sites or agro-ecological zones. Mahalanobis D2 statistics revealed the highest inter-cluster distance between cluster II and VI. Accessions of these clusters are potential parents for future breeding programs. This study showed that aerial yam from Cameroon has an enormous wealth of traits variation, indicating huge potential for its genetic improvement through selection and hybridization.

Cowpea (Vigna unguiculata) is an important tropical legume crop contributing significantly to food security in tropical regions. The present study was carried out to determine the extent of genetic variation, to estimate character associations, heritability and genetic advance of 25 quantitative traits in 30 genotypes of cultivated Vigna unguiculata from the western highland region of Cameroon. These quantitative traits were selected among cowpea descriptor lists. For all these traits, the analysis of variance showed significant difference among genotypes, highlighting the existence of important genetic divergence among the studied accessions. The highest phenotypic and genotypic coefficient of variation was observed in grain yield, pod yield and 100 seed weight. Genetic advance of these three characters was also the highest. Broad sense heritability was high in general, with 20 traits out of 25 having heritability values greater than 70%. This high heritability indicates little influence of the environment on these characters in cowpea. The highest heritability was recorded for 100 seed weight (98.15%) and the lowest for shoot weight (41.38%). At 0.05 probability level, grain yield correlated significantly with 21 out of the 24 other quantitative traits. Among others, grain yield correlated positively and significantly with 100 seed weight, number of pods per plant, number of branches per plant, number of nodes per plant, plant height, plant width, pod length, pod width, seed length, seed width and number of seeds per pod. These positive correlations between grain yield and many other traits indicate that a selection program based on any of these traits will result in increasing yield. Cluster analysis using UPGMA method revealed five distinct clusters. Genotypes named KEBCP025, KEB-CP006, KEB-CP098, KEB-CP070, and more importantly KEB-CP054 and KEB-CP004, were grouped in a single cluster and were characterized by a significantly higher grain yield, pod yield, number of pods per plant, number of seed per pod, plant height, pod length and pod width compared to other clusters. Accessions KEB-CP036 and KEB-CP031 produced significantly more important fresh biomass. These genotypes could be used as parents in genetic improvement programs aiming to increase yield and fresh biomass in cowpea.

Genetic variation of quantitative traits is a prevalent characteristic among cultivated tomato varieties. Twenty tomato genotypes comprising indigenous varieties and commercial cultivars, cultured in the Western Region of Cameroon were evaluated using fourteen quantitative traits for disease resistance, phenotypic divergence and heritability estimates. The experiment was carried out using a randomized completed blocks design with three replications. Data collections were disease characteristics, plant development features and yield attributes. The analysis of variance revealed significant variation among genotypes for all the experimental quantitative traits. Hybrid varieties had significantly more fruit yield (1066.00 g/plant), single fruit weight (57.28 g), fruit diameter (4.47 cm) and pericarp thickness (0.54 cm) compared to standard and indigenous varieties. These indigenous varieties were significantly more resistant to late blight, alternaria leaf spot and viral diseases. They also had significantly higher collar diameter (16.30 mm), number of primary branches per plant (8.45), number of fruit per plant (31.58) and plant height (88.33 cm) compared to standard and hybrid plants. The genotype local 2 was the third most productive (1576.39 g / plant) after Rio Semagri (1984.80 g/plant) and Sakato F1 (1691.69 g/plant). Heritability and genetic advance estimates were high for twelve of the fourteen studied quantitative traits. Fruit yield showed significant positive correlations with single fruit weight and number of fruit per plant. However, significant negative correlation was found between fruit yield and time to 50 % flowering, 50 % fruiting, 50 % maturity and viral disease. The first three and the first four components in the principal component analysis explained, respectively, 77.85 % and 88.38 % of the total variation observed among genotypes. The first component determined 41.42 % of the total variation, dominated by the collar diameter, the number of primary branches per plant and plant height. This study clearly indicated that indigenous varieties are the most disease resistant genotypes and are having substantial fruit yield (945.30 g/plant) similar to standard varieties and at a touching distance to hybrid cultivars.

Characterization of the genetic diversity and analysis of the genetic relationship between accessions of a crop species is a key step in breeding superior cultivars. The main objective of the hereby study was to determine the genetic variation between 30 cowpea accessions collected throughout the eight divisions of the Western Region of Cameroon using qualitative traits. Phenotypic variation of these accessions was evaluated using diversity indices and cluster analyses. A total of twenty qualitative traits were used for the study. Fifteen of them (75%) were polymorphic, displaying each at least two phenotypic classes. The monomorphic characters were growth pattern, leaf color, leaf hairiness, plant hairiness and pod hairiness, each with only one phenotypic class. Results showed a relatively significant level of genetic diversity among the studied cowpea accessions. Overall, the average of the observed and effective number of phenotypic classes per qualitative trait were Na = 2.350 and Ne = 1.828 respectively. The Nei's genetic diversity and the Shannon weaver diversity index were He = 0.369, ranging from zero (monomorphic trait) to 0.655 (growth habit) and H' = 0.609, ranging from zero (monomorphic trait) to 0.996 (seed crowding), respectively. The dendrogram constructed from the twenty qualitative traits revealed 05 accessions clusters with the number of accessions in each cluster varying from one to eleven. Information obtained from this study is likely be useful for future cowpea breeding program.