Taro is an ancient nutritional and medicinal crop woven into the fabric of the socio-economic life of those living in the tropics and sub-tropics. However, West Africa (WA), which has been a major producer of the crop for several decades, is experiencing a significant decline in production as a result of taro leaf blight (TLB), a disease caused by Phytophthora colocasiae Raciborski. A lack of research on taro in WA means that available innovative technologies have not been fully utilized to provide solutions to inherent challenges and enhance the status of the crop. Improvement through plant breeding remains the most economically and environmentally sustainable means of increasing the productivity of taro in WA. With this review, we provide insights into the importance of the taro crop in WA, evaluate taro research to date, and suggest how to address research gaps in order to promote taro sustainability in the region.

Crop genetic diversity is a sine qua non for continuous progress in the development of improved varieties, hence the need for germplasm collection, conservation and characterization. Over the years, cowpea has contributed immensely to the nutrition and economic life of the people in Togo. However, the bulk of varieties grown by farmers are landraces due to the absence of any serious genetic improvement activity on cowpea in the country. In this study, the genetic diversity and population structure of 255 cowpea accessions collected from five administrative regions and the agricultural research institute of Togo were assessed using 4600 informative diversity array technology (DArT) markers. Among the regions, the polymorphic information content (PIC) ranged from 0.19 to 0.27 with a mean value of 0.25. The expected heterozygosity (He) varied from 0.22 to 0.34 with a mean value of 0.31, while the observed heterozygosity (Ho) varied from 0.03 to 0.07 with an average of 0.05. The average inbreeding coefficient (F_IS) varied from 0.78 to 0.89 with a mean value of 0.83, suggesting that most of the accessions are inbred. Cluster analysis and population structure identified four groups with each comprising accessions from the six different sources. Weak to moderate differentiation was observed among the populations with a genetic differentiation index varying from 0.014 to 0.117. Variation was highest (78%) among accessions within populations and lowest between populations (7%). These results revealed a moderate level of diversity among the Togo cowpea germplasm. The findings of this study constitute a foundation for genetic improvement of cowpea in Togo.

Increasing frequency of drought spells occasioned by changing climatic conditions, coupled with rise in demand for bread wheat, calls for the development of high yielding drought resilient genotypes to enhance bread wheat production in areas with moisture deficit. This study was designed to identify and select drought-tolerant bread wheat genotypes using morpho-physiological traits. One hundred and ninety-six bread wheat genotypes were evaluated in greenhouse and field experiments, under well-watered (80% of field capacity) and drought-stressed (35% of field capacity) conditions, for two years. Data were collected on five morphological traits (flag leaf size, flag leaf angle, flag leaf rolling, leaf waxiness and resistance to diseases) and 14 physiological traits. Relative water content (RWC), Excised leaf water retention (ELWR), Relative water loss (RWL), Leaf membrane stability index (LMSI), as well as Canopy temperature depression (CTD) at heading (CTDH), anthesis (CTDA), milking (CTDM), dough stage (CTDD) and ripening (CTDR) were estimated. Similarly, leaf chlorophyll content (SPAD reading) was recorded at heading (SPADH), anthesis (SPADA), milking (SPADM), dough stage (SPADD), and ripening (SPADR). Significant (p<0.01) genotypic differences were found for the traits under both well-watered and drought-stressed conditions. Associations of RWL with SPADH, SPADA, SPADM, SPADD and SPADR were significant (p<0.01) and negative under both watering regimes. The first three principal components accounted for 92.0% and 88.4% of the total variation under well-watered and drought-stressed conditions, respectively and comprised all the traits. The traits CTDD, CTDM, CTDR, SPADH, SPADA, SPADM, SPADD and SPADR with genotypes Alidoro, ET-13A2, Kingbird, Tsehay, ETBW 8816, ETBW 9027, ETBW9402, ETBW 8394 and ETBW 8725 were associated under both conditions. Genotypes with narrow flag leaves, erect flag leaf angles, fully rolled flag leaves, heavily waxed leaves, and resistant to disease manifested tolerance to drought stress. The identified traits and genotypes could be exploited in future breeding programmes for the development of bread wheat genotypes with tolerance to drought.

Drought is one of the most important yield-limiting abiotic stresses threatening wheat production and productivity. Development of wheat genotypes with enhanced grain yield under drought-stressed conditions depend on the extent of genetic variation present for drought tolerance-related traits. This study was carried out to determine the level of genetic variation and associations of yield and yield attributing traits among 196 bread wheat genotypes under drought-stressed and well-watered conditions. The genotypes were evaluated under greenhouse and field conditions and phenotyped for yield and yield-related traits. The genotypes varied significantly for the traits under both conditions. Grain yield ranged from 2.13 to 3.74 t ha ⁻¹ and from 2.52 to 5.06 t ha ⁻¹ under drought-stressed and well-watered conditions, respectively. Under both conditions, variances due to genotype were higher than environment and genotype × environment interaction variances for all the traits. Estimates of phenotypic coefficient of variation (PCV) were higher than genotypic coefficient of variation (GCV) for all the traits under both conditions, with both PCV and GCV being highest for kernel weight spike ⁻¹ and lowest for spike fertility. Under both conditions, broad-sense heritability estimates ranged from moderately high to very high, accompanied with high genetic advance as a percentage of the mean. Fertile spikelets spike ⁻¹ , one thousand kernel weight, kernel weight spike ⁻¹ , biomass yield and harvest index manifested high positive genotypic and phenotypic correlations and positive direct effects on grain yield under both conditions. The first five principal components accounted for 78.4% (well-watered) and 76.0% (drought-stressed) of the variation among the genotypes. The 196 genotypes were delineated into six major clusters under both water conditions, with clusters 3 (well-watered) and cluster 5 (drought-stressed) containing genotypes with the highest ability to tolerate drought stress. Genotypes Alidoro, Bolo, Dinknesh, ETBW8491 and ETBW172938 had high stable yields under both conditions. The identified traits and genotypes were drought tolerant and could be exploited to develop novel genotypes for drought stress tolerance.

Inbred line development requires information on the nature and magnitude of genetic variability and transmissibility of desired trait in source populations. In this study, the level of genetic variability, heritability and genetic advance of thirteen agronomic and fresh yield traits among twelve shrunken-2 super-sweet corn populations were evaluated. Field experiments were conducted for two years in Ibadan, Nigeria using a randomised complete block design with three replicates. Estimates of genetic variability components, broad-sense heritability and genetic advance were computed for each trait. All the traits exhibited significant genotypic differences. Genotypic variance was significant for number of marketable cobs, yield of cobs, number of cobs, number of kernel rows, husk cover, ear height and days to anthesis, while environmental variance was significant for all the traits. Phenotypic coefficients of variation were higher than the corresponding genotypic coefficients of variation for all traits. Broad-sense heritability ranged from 22.2% for anthesis-silking interval to 85.1% for husk cover. The genetic advance was high (32.7%) for husk cover, medium (12.0%) for yield of cobs and low for other traits. Genetic variability was present among the shrunken-2 super-sweet corn populations. Opportunities abound for further improvement of the populations and extraction of lines for hybrid seed production. Key words: Broad-sense heritability, genotypic coefficient of variation, husk cover score, sweet corn, yield of marketable cobs.

Seed size is an important yield and quality-determining trait in higher plants and is also crucial to their evolutionary fitness. In African yam bean (AYB), seed size varies widely among different accessions. However, the genetic basis of such variation has not been adequately documented. A genome-wide marker-trait association study was conducted to identify genomic regions associated with four seed size traits (seed length, seed width, seed thickness, and 100-seed weight) in a panel of 195 AYB accessions. A total of 5416 SNP markers were generated from the diversity array technology sequence (DArTseq) genotype-by-sequencing (GBS)- approach, in which 2491 SNPs were retained after SNP quality control and used for marker-trait association analysis. Significant phenotypic variation was observed for the traits. Broad-sense heritability ranged from 50.0% (seed width) to 66.4% (seed length). The relationships among the traits were positive and significant. Genome-wide association study (GWAS) using the general linear model (GLM) and the mixed linear model (MLM) approaches identified 12 SNP markers significantly associated with seed size traits across the six test environments. The 12 makers explained 6.5–10.8% of the phenotypic variation. Two markers (29420334|F|0-52:C>G-52:C>G and 29420736|F|0-57:G>T-57:G>T) with pleiotropic effects associated with seed width and seed thickness were found. A candidate gene search identified five significant markers (100026424|F|0-37:C>T-37:C>T, 100041049|F|0-42:G>C-42:G>C, 100034480|F|0-31:C>A-31:C>A, 29420365|F|0-55:C>G-55:C>G, and 29420736|F|0-57:G>T-57:G>T) located close to 43 putative genes whose encoding protein products are known to regulate seed size traits. This study revealed significant makers not previously reported for seed size in AYB and could provide useful information for genomic-assisted breeding in AYB.