Impact analysis of predisposing factor on downy mildew disease and exploration for resistance sources in basil accessions

Basil Downy Mildew (BDM) is a devastating disease and leads to massive crop losses worldwide due to scarcity of genetic resistance varities. In the present study disease incidence was reported up to 100% under the congenial weather conditions. The causal agent of downy mildew characterized based on the morphological comparison and sequencing of inter transcribed spacer (ITS) and Cox2 genes. Microscopic observations revealed the hyaline sporangiophores 2-7 branching with the mean length of 412.96 μm and branches ultimately dichotomously branched. Further, sequencing of BDM-AG isolate shared >99% sequence identity and in phylogenetic tree sequences form a highly supported clade with other isolates of P. belbahrii. A sudden outbreak of BDM up to 97-98% severity index recorded at the flowering stage, followed by heavy rain. Among the 45 accessions were evaluated, out of which 3 expressed highly resistant responses against downy mildew disease. The phenylalanine ammonia-lyase (PAL) activities was higher (22.39 + 0.618) in diseased leaf samples than healthy leaf tissues. The identified accessions may be further used in the breeding programs for resistance varietal development, which will mitigate the use of fungicides in the management of BDM.