Effect of weather parameters and date of sowing on intensity of Alternaria blight of rapeseed mustard

Abstract

The production and productivity of oilseed brassicas are revelation to the biotic and abiotic stresses that divulges to lower the world average. The Alternaria blight disease severity is confided to weather conditions, varieties, age of host plants and the pathogens. Experiment was set up, to analyze the effect of weather variable and sowing dates on the disease severity of rapeseed mustard and its effect on yield. The data for the Rabi season (2017–2018) shown that the periodical increase in the disease severity with the delay in sowing. Percent diseases intensity (PDI) progression was higher during 3rd sowing (D3) at 75 and 100 Days after sowing in Brassica juncea varieties followed by Brassica napus and Brassica nigra varieties. The disease severity differed significantly among the sowing dates and varieties, RLC-3 showed maximum PDI (52.19%) whereas, PC-6 indicated minimum PDI (0.98%).The maximum seed yield (20.37 q/ha) was recorded on 1st sowing (D1) followed by 2nd sowing (D2) (12.59 q/ha). Giriraj showed maximum seed yield followed by GSC-7. Highest Area under disease progressive curve value was recorded in RLC-3 variety (3885.91) having 3rd sowing (D3) and the lowest was recorded in PC-6 variety (54.77) having 1st sowing (D1). The maximum temperature (15.7–30.3 °C) and minimum temperature (3.3–12.6 °C) was positively correlated with disease severity, disease severity increases with increase in temperature and vice versa.