Analysis of Seedling Root Architecture of Vigna unguiculata (Sampea 1-20) Using Cigar-Roll Method under Controlled Condition

Cowpea (Vigna unguiculata) varieties, including the improved SAMPEA series in Nigeria, remain crucial for food security, particularly in sub-Saharan Africa. However, their yields are constrained by edaphic stresses such as low phosphorus (P) and drought. Phenotyping cowpea seedling root architecture using the cigar-roll method is crucial for identifying root phenes needed for breeding phosphorus-efficient and drought-tolerant varieties. This study evaluated the Root System Architecture (RSA) of 20 elite cowpea genotypes (SAMPEA 1 to 20) obtained from the Institute for Agricultural Research (IAR), Ahmadu Bello University, Zaria, using the cigar-roll method. Significant (p<0.05) phenotypic variation was detected for all phones evaluated. Significant variation was observed in architectural traits, including primary root length and lateral root density in the first 5cm of the root. Root hair length and density were positively associated with lateral root density in both the first 5cm from the base of the hypocotyl and the lateral roots between 5 and 10 cm from the base of the hypocotyl. Genotypes with longer root hairs (SAMPEA 14, 20, 12 and 13) and a longer taproot (SAMPEA 10) were identified as potential parents for breeding. The identified phenes could guide in breeding efforts for cowpea varieties suited to low phosphorus and water-limiting soils. Our results suggest that the root phenotype plays an important role in cowpea growth in suboptimal environments and can serve as a marker to facilitate the development of improved varieties with enhanced yield, particularly in sub-Saharan Africa, where soils with low phosphorus and drought are predominant.