Molecular characterization of fusarium and screening of cowpea [Vigna unguiculata (L.) walp.] germplasms against fusarium wilt (Fusarium oxysporum f. sp. tracheiphilum)

Fusarium wilt caused by fungal pathogen, Fusarium oxysporum is one of the soil-borne diseases that cause 30 to 100% yield reduction with high plant mortality and severe problem in cowpea production.

The Fusarium spp. isolate was obtained from infected cowpea plants and morphological and molecular characterization were done using universal primers. Similarity and phylogenetic evolutionary relationship analysis were performed with database. The fusarium wilt symptoms occurrence in each germplasm were scored using disease rating scale by artificial inoculation of 10% culture.

Isolated Fusarium spp. was an anamorphic species with medium growth rate (5 mm/day), characterised by white cottony to pinkish colonies, aseptate microconidia (12.879 × 3.570 μm) with false head, septate macroconidia (32.409 × 5.297 μm) along with chlamydospores. While, 90-100% homology was observed between isolate (Accession no: MZ706473) and fusarium reference database. Phylogenetic evolutionary analysis showed that the isolate was closely related to F. oxysporum (OL679453.1) strain supported by 52% bootstrap. Artificial screening of 115 cowpea germplasm under pot culture, identified 18 resistant lines with 0% symptoms. The wilting intensity was maximum during flowering or pod stage than seedling stage in cowpea. The identified resistant cowpea varieties could be used as donor parent in future resistant breeding programmes.