Northern corn leaf blight (NCLB) of maize, caused by Exserohilum turcicum (Pass.) Leonard and Suggs., is an important foliar disease common across maize-producing areas of the world, including Bihar, India. In this study, virulence and distribution of races were observed against Ht-resistant genes and also identified the E. turcicum race population distribution in Bihar. For that, 45 E. turcicum isolates were collected from maize fields in Bhagalpur, Begusarai, Khagaria, Katihar and Samastipur districts between 2020 and 2022. These isolates were screened on maize differential lines containing Ht1, Ht2, Ht3 and HtN1 resistance genes. Five different physiological races were observed based on the symptoms response of the differential maize lines. These races are race 0, race 1, race 3, race 23N and race 123N. E. turcicum race 3 was the most prevalent race having 26.6% frequency followed by race 0 (24.4%) and race 1 (22.2%) and the least prevalent races were race 23N and 123N having 13.3% each. Varied resistance response of different isolates was observed on differential lines having different resistant genes. Despite the fact that virulence was seen against all Ht resistance genes, NCLB control might be increased by combining qualitative Ht resistance genes with quantitative resistance.
Keywords: Bihar; Exserohilum turcicum; NCLB; Setosphaeria turcica; TLB; differential lines; race.