Quantitative trait loci and genomic prediction for grain sugar and mineral concentrations of cowpea [Vigna unguiculata (L.) Walp.].

Development of high yielding cowpea varieties coupled with good taste and rich in essential minerals can promote consumption and thus nutrition and profitability. The sweet taste of cowpea grain is determined by its sugar content, which comprises mainly sucrose and galacto-oligosaccharides (GOS) including raffinose and stachyose. However, GOS are indigestible and their fermentation in the colon can produce excess intestinal gas, causing undesirable bloating and flatulence. In this study, we aimed to examine variation in grain sugar and mineral concentrations, then map quantitative trait loci (QTLs) and estimate genomic-prediction (GP) accuracies for possible application in breeding. Grain samples were collected from a multi-parent advanced generation intercross (MAGIC) population grown in California during 2016-2017. Grain sugars were assayed using high-performance liquid chromatography. Grain minerals were determined by inductively coupled plasma-optical emission spectrometry and combustion. Considerable variation was observed for sucrose (0.6-6.9%) and stachyose (2.3-8.4%). Major QTLs for sucrose (QSuc.vu-1.1), stachyose (QSta.vu-7.1), copper (QCu.vu-1.1) and manganese (QMn.vu-5.1) were identified. Allelic effects of major sugar QTLs were validated using the MAGIC grain samples grown in West Africa in 2017. GP accuracies for minerals were moderate (0.4-0.58). These findings help guide future breeding efforts to develop mineral-rich cowpea varieties with desirable sugar content.

Molecular and phenotypic diversity of groundnut (Arachis hypogaea L.) cultivars in Togo.

Diversity assessment of 94 groundnut accessions from Togo and Senegal, using agro-morphological and SNP markers, revealed high variability for many quantitative traits such as late leaf spot (LLS) incidence, number of pods per plant and yield per plant. For qualitative traits, the Simpson Index showed high diversity for primary seed colour (0.75), stem pigmentation (0.60), and Growth habit (0.59). Principal component analysis underscored quantitative traits such as hundred seed weight, days to maturity, and LLS incidence, as the main traits contributing to the divergence. Correlation and path coefficient analysis showed that the number of pods per plant was the main yield-related trait positively affecting yield (r = 0.95, PC = 0.84; p = 0.01). Overall, 990 SNP markers revealed moderate genetic variability in the genotypes and the percentage of heterozygous genotypes varied from 0 to 50% for all loci. Analysis of molecular variance revealed that only 1.1% of the total molecular variance accounted for geographical contribution to the diversity. Co-analysis of phenotypic and SNP data delineated three clusters harbouring useful alleles and interesting phenotypic features such as LLS resistance, large number of pods per plant and early maturity indicating that differences observed at the phenotypic level are underlined by genotypic differences. The phenotypic and genotypic diversity observed could be exploited for the identification of parents with preferred traits for use in the breeding program. However, the low population structure highlights the necessity to improve groundnut diversity in Togo through introduction from various sources.