Inheritance of Resistance to Rust in Cowpea Vigna unguiculata (L.) Walp

Cowpea rust Uromyces vignae is a major disease in South India that causes substantial loss of the cowpea crop especially in growth and yield. The mode of gene action conferring resistance to the fungus is not well understood. The objective of the study wastodetermine the inheritance of rust resistance in cowpea crosses. Three cowpea varieties that are commonly grown by farmers were crossed with five indigenous resistant cowpea landraces. Inheritance pattern and dominance reaction of cowpea rust Uromyces vignae were examined using eight parental lines, 10 F₁s and F₂ generation of one cross C-152 x IC 68786. The result of this study provided an indication that rust resistance was conditioned by more than one gene with dominance of susceptibility. Rare occurrence of extreme phenotypes, continuous frequency distribution with normal distribution properties and platykurtic nature, transgressive segregants and geometric cumulative effect were observed in F₂ generation which supports polygenic inheritance. Observation of continuous distribution of progenies for severity data in the F₂ population also confirmed significance of quantitative inheritance for cowpea rust resistance.