Inheritance and Allelic Relationships of Alectra vogelii Benth. Resistance Genes in Cowpea Genotypes B301 and KVx414-22-2

Alectra vogelii Benth. is the second most important parasitic weed in cowpea [Vigna unguiculata (L.) Walp.] production in Burkina Faso. Several resistant varieties to this weed have been identified in the country among which are B301 and KVx414-22-2. The inheritance and allelic relationships of the resistance genes in the two varieties have not been studied with A. vogelii strains in Burkina Faso. The objective of this study was to determine the inheritance and allelic relationship of the resistance genes in B301 and KVx414-22-2. To determine the inheritance of the genes for resistance, the resistant varieties (B301 and KVx414-22-2) were each crossed to a susceptible variety IT82D-849 to generate F1 and F2 populations. For the allelic relationship study the two resistant genotypes were crossed among themselves to generate F1 and F2 offspring. The parents and their F1 and F2 progenies were screened in artificially infested pots with Alectra seed in a screen house at Kamboinsé Research Station in Burkina Faso. Resistance/susceptibility of genotypes was assessed by recording the number of emerged Alectra shoots. The data were subjected to the Chi-Square goodness-of-fit test for one, two and three genes segregation ratios. The results revealed that two independent dominant genes confer resistance in the variety B301 and a single dominant gene confers resistance in variety KVx414-22-2. The single dominant gene in KVx414-22-2 is non-allelic to the two genes in B301. The two resistance genes in variety B301 have already been named Rav1 and Rav2 whilst Rav3 is the name of the resistance gene in variety IT81D-994. Therefore, we propose the symbol Rav4 as the name for the resistance gene in variety KVx414-22-2.