Influence of soil moisture stress and Macrophomina phaseolina in charcoal rot development in grain sorghum

The effects of Macrophomina phaseolina, soil moisture stress (SMS), and their interaction on charcoal rot development in sorghum were studied in field experiments. Individual effects of the pathogen and that of SMS were studied by eliminating SMS by furrow irrigation, and the pathogen by soil fumigation with methyl bromide, respectively. Significant effects of the pathogen, SMS, and pathogen x SMS interaction were found on charcoal rot development (percentage lodging) in sorghum hybrid CSH 6. Soil fumigation drastically reduced the population of the pathogen. Lodging was 3.18% in no-SMS plots as against 100% in the SMS plots. Under SMS, lodging was 6.27% in the fumigated plots compared with 100% in the non-fumigated plots, indicating that moisture stress alone cannot cause significant lodging in the absence of the pathogen. There was no colonization of stalks by the pathogen in the fumigated SMS plots compared with very high colonization in the non-fumigated SMS plots. Grain yield reduction due to charcoal rot was estimated between 20 and 33%