Selection of phenotypic traits and resistance to Cowpea severe mosaic virus and Cowpea aphid-borne mosaic virus in cowpea [Vigna unguiculata (L.) Walp.] seeds with rugose white coat

Abstract

Cowpea [Vigna unguiculata (L.) Walp.] is an important protein source in diets in Brazil. The preference of consumers is for large, white, light brown and evergreen seeds with rugose coat and small hilum and hilum ring. The Cowpea severe mosaic virus (CPSMV) and the Cowpea aphid-borne mosaic virus (CABMV) are the main pathogens in cowpea plantations in Brazil. This study selected cowpea offspring with (i) white rugose coat seed characteristics that are accepted by markets and (ii) that present resistance to CPSMV (serotype I) and CABMV. The first selection of asymptomatic plants was carried out using seedlings from F 3 seeds mechanically inoculated with a mixture of the two viruses. Offspring F 3:4 went through a second selection process with two stages, one in the field (with natural inoculation), one in trays (with mechanical inoculation). In total, 40 F 3:4 offspring were selected to evaluate agronomic traits in two field assays, one in Teresina, one in Tracuateua (states of Piauí and Pará, respectively) based on a randomized block design with four repetitions. Significant effect of genotype and of the interaction assay x genotype was observed (p ≤ 0.01) for most of the traits evaluated: weight of 100 seeds, yield, seed length, width, and height; length-to-height ratio; width-toheight ratio, and hilum width-to-length ratio. Fourteen offspring produced large seeds (25 -30 g in 100 seeds), and four presented cross-resistance to CPSMV and CABMV, while 36 offspring were resistant only to CPSMV.

Inheritance of cowpea resistance to Cowpea aphid-borne mosaic vírus

“…Mutations on the amino acids or VPg disable such interaction and lead to plant resistance due to the reduction or absence of virus replication. As the resistance to CABMV in line IT85F-2687 is ruled by a recessive gene, backcrossing is the best genetic improvement method to incorporate resistance into other cowpea genotypes with desirable agronomic traits (Leão et al, 2016). The results of the present study might lead to further genetic mapping research about this gene through the identification of related molecular markers that might be used in markerassisted selection.…”