Effects of nitrogen, plant density, moisture stress and artificial inoculation with macrophomina phaseohna on charcoal rot incidence in grain sorghum

Effects of different levels of nitrogen, plant density, soil moisture stress and of anificial inoculation with Macrophomina phaseolina on charcoal rot incidence in grain sorghum were studied in a split-split-split field plot design. Nitrogen levels were applied to main plots; plant densities, moisture stresses and inoculations were replicated in sub, sub-sub and sub-sub-sub plots. A gradient of soil moisture stress was created during grain filling by line-source sprinkler irrigation. Analysis of variance indicated significant effects of moisture stress, plant density and their interactions on charcoal rot disease incidence as measured by piant lodging. Lodging increased linearly along the gradient of water supply suggesting a positive relationship between moisture stress and disease development. Lodging was also significantly (P < 0.01) and highly correlated with other charcoal rot disease parameters (soft stalk, number of nodes crossed, root infection and plant senescence). There were no significant differences (P < 0.05) in charcoal rot incidence among inoculation treatments. Lodging increased in both high nitrogen and high plant population treatments under moisture stress condition