Mehra, RakeshManjeet Singh2018-05-072018-05-072017http://krishikosh.egranth.ac.in/handle/1/5810044714The maydis leaf blight disease of maize (Zea mays L.) caused by Bipolaris maydis has emerged as a serious problem in most of the maize growing places of India, leading to considerable yield losses in maize. The present investigation on epidemiology, management and variability (cultural, morphological, pathogenic and genetic) were carried out with twenty six isolates of B. maydis collected from maize growing areas of the country. Out of four dates of sowing of maize, the highest disease intensity, AUDPC and AIR was observed in Ist date of sowing (15 June) followed by IInd date of sowing (27 June), IIIrd date of sowing (10 July) and least disease intensity in IVth date of sowing (25 July) on all the five hybrid and inbreds. Maximum temperature range of (32.2-34.20C), minimum (23.7-25.30C) with relative humidity morning (88-93%) and evening (59.5 -76.7 %), rainfall (0.0-7.4 mm), evaporation (2.6-3.9 mm), sun shine (4.8- 9.7 h/day) and wind speed (2-3.4 km/h) were most congenial for disease progression during Kharif 2015 and 2016. Temporal increase was maximum in 33th to 34th and 36th to 37th metrological weeks in all the five hybrid/inbreds during both the years. Disease progression, AUDPC and AIR value were more in Kharif 2016 as compare to Kharif 2015 however, among the five hybrid/inbreds highest in HKI-PC4B and minimum on HM-4 in all four date of sowing during Kharif 2015 and 2016. Relative humidity, rainfall and temperature showed important role in disease progression. Regression equations on relationship between disease development and weather parameter have been developed for five maize hybrid/ inbreds. Out of one hundred and two inbred lines and one hundred and four hybrids of maize screened against maydis leaf blight under artificial inoculated conditions, six inbreds and eighteen hybrids found resistant respectively. Out of eight fungicides evaluated against B. maydis, propiconazolee and tebuconazole provided maximum per cent growth inhibition, disease control and also increase yield. Among twelve plant extracts evaluated against B. maydis, garlic clove and neem leaves extracts at 20 per cent concentration were found most effective both under in vitro and in vivo conditions. Bio agents, Trichoderma harzianum and T. viride found most effective under in vitro, screen house and field conditions. For integrated disease management, combination of propiconazolee (0.1%) + garlic (20%) + T. harzianum and tebuconazole (0.1%) + neem (20%) + T. viride were most effective and also increase the yield. All the twenty six isolates identified, belonged to B. maydis based on their morpho-cultural characteristics. Among the isolates, BM-22 and BM-23 from Gogunda and Fateh Nagar recorded maximum colony diameter. The growth pattern varies among twenty six isolates of B. maydis showed rough or smooth texture, regular or irregular margin with or without zonation, mycelium of isolates was either appressed or raised type. The colors of the colony were highly variable and size of conidia ranged 28.38-77.40 × 10.32-23.22μm. The conidia size of isolate BM-20 was largest (63.98 × 15.74 μm) with highest average number of' septa (5.9). In pathogenic variations, the isolate BM-16 from Karnal was most virulent and aggressive in comparison to other twenty five isolates of B. maydis, as it showed shortest mean latent period (39.6 h) and maximum mean disease score (4.1) across ten maize genotypes. Molecular variability among the twenty-six isolates of B. maydis has been examined through RAPD and ITS analysis, isolate BM-3 isolate to remain alone in the dendrogram, whereas maximum closeness (97%) was observed between BM-24 and BM-25 isolates.ennullThesis