First report of evaluation of new world cotton genotypes (Gossypium hirsutum) for resistance to grey mildew disease caused by Ramularia areola Atk. a potential hazard for cotton belt of Odisha, India

Abstract

Cotton (Gossypium spp.) is a profitable commercial crop that spans over 33 million hectares in 77 countries and is a vital source of natural fibre globally. It is extensively grown in India and supports over 60 million Indians, including 6 million farmers, the majority of whom are small and marginal farmers. The current study used a randomised block design with two replications and a spacing of 90 cm x 60 cm to explore 89 cultivars from one frequently planted tetraploid species (G. hirsutum) in an areolate mildew hotspot in Odisha during the kharif of 2019, 2020, and 2021. The infector row technique was utilised to supplement natural disease pressure, and the severity of grey mildew was graded on a 0-4 scale. Among all the genotypes tested GSHV-159 and GISV-272 were reported to be disease free. While 32 genotypes shown only moderate resistance to the disease, 22 entries had consistently strong resistance over three years. These genotypes can be used as Grey mildew resistant donors. Twenty-four of the types tested were vulnerable to grey mildew, while the remaining nine germplasms were extremely sensitive to the fungus. These findings support cotton producers, particularly small, marginal, and tenant farmers, in selecting the best genotypes with resistance to grey mildew disease, a hazard to the environment, the economy and most importantly, sustainable crop production.