Rathi, A.S.K. Basavaraj2017-11-182017-11-182017http://krishikosh.egranth.ac.in/handle/1/5810035975White rust disease caused by Albugo candida is an important disease of Indian mustard (Brassica juncea.) in India particularly in northern and North eastern states. Keeping in view the enormous loss caused by the pathogen, the present study has been devised on epidemiology, variability and management studies under field and screen house conditions during rabi 2014-15 and 2015-16 at CCS HAU, Hisar. In epidemiological studies the two Indian mustard varieties namely RH 30 and RH 0749 were sown in different dates to observe the influence of weather factors on onset and progression of the disease. The white rust disease appeared early in the season i.e. last week of December in first three dates of sowings while a week delayed in late sown crops. Initially, after the onset of the disease, disease was slow and non-significant; however it gained momentum and showed significant difference among the observations in all dates of sowing from second week of January. The highest disease intensity was observed during the third week of January. The disease was rapid and more severe on variety RH 30 as compared to RH 0749. The severity was observed to be more with the delayed sowing. Investigation on selective criteria for Indian mustard genotypes for white rust intensity and yield revealed that, existence of great variability among the all the genotypes for white rust intensity and yield characters under all the three environments such as natural, artificially pathogen inoculated and pathogen controlled environment. The disease severity was more in environment where the zoosporangial suspension was artificially inoculated to create a disease pressure compared to naturally infected and controlled environments. In general the genotypes RH 9801, RH 9304 recorded the minimum disease severity while the genotypes RB 50, RH 0725, RH 0673 and RH 1134 were found to be highly susceptible. The genotypes RH 8812, RH 9304, RH 0749 performed better with uniform superiority under both no disease stress and disease stress conditions. So such genotypes can be encouraged to use in breeding programme. The variability among the Albugo candida isolates collected from the six different locations of Northern India and also from the different Brassica species from the Hisar showed considerable variation in morphology and pathological reactions on set of Brassica host species. The isolates showed greater variation in size and germination percentage of sporangia; however very less variability was observed for the shape of sporangia in which all the isolates exhibited spherical to globose. Based on the pathogenic reaction on set of Brassica species, Hisar, Bawal, Bharatpur and Ludhiana were seems to be similar. The Pantnagar and Delhi isolates seems to be entirely distinct isolates from Northern India. The results of cross inoculation studies indicated about existence of variability in the isolates and five groups were identified among the isolates. Among the different fungicides tested for their efficacy against white rust, spray of mancozeb 75 WP 45 DAS @0.2% followed by azoxystrobin 23% SC @ 0.05% at 60 DAS gave maximum control of the disease at both leaf and staghead phase with higher seed yield.ennullThesis