Epidemiology and Management of Maydis Blight Caused by Bipolaris Maydis In Maize

Abstract

Fortnightly survey were conducted to assess the status of maydis blight of maize during Kharif 2017 and 2018 in Jammu sub-tropics and the data revealed that maximum disease severity was observed in Samba district (39.19-47.56%) followed by Jammu (29.97-52.29%) and Kathua (29.12-45.38%), respectively. However, minimum disease was observed in Udhampur district (25.47-31.77%). The Pathogenicity of Bipolaris maydis isolates (Bm1 to Bm35) on cv. Vijay revealed maximum disease severity (67.25%) in isolate Bm23 and least in Bm28 (25.67). Significant and positive correlation of relative humidity (morning) and sunshine hours with maydis blight diseasewas also observed. However, maximum and minimum temperature showed negative, but significant correlation with the disease severity, while rainfall exhibited negative and non-significant correlation. newlineCultural and morphological variability of B. maydis isolates exhibited a great variability in respect of colony characters as olivaceous green, dirty white to black, brown to dark and grey color. The margins of colony varied from circular, undulated irregular form and umbonate to raised elevation, smooth to wrinkled surface while pigmentations recorded were black, dark brown and dark grey. The number of septation in isolates ranged from 6.0 to 9.33 and spore size ranged from 56.68-89.82 µm in length and 9.68-13.50 µm in breadth. The shape of spore was straight to curved. All the isolates showed excellent growth on PDA, good growth on ZDA and NA while, fair and poor growth was observed in MEA and OMA media. On the basis of pathogenic response of B. maydis on different maize cultivars, isolates Bm23 and Bm7 were observed highly virulent whereas, Bm26 was least virulent. newlineThe loss in grain yield varied from 14.34-42.75% in 2017 and 15.07-43.39% in 2018 depending upon disease severity in different genotypes, while genotype C 8 recorded highest loss in grain yield (42.75 and 43.39%) and least in Double Dekalb (14.34 and 15.07%), during both the years. Eighty nine maize genotypes w