Soil Temperature and Moisture Effects on Sclerotia Germination and Infection Behavior of Macrophomina phaseolina in Bean

Abstract

Macrophomina phaseolina is a destructive soil-borne fungal pathogen responsible for charcoal rot in beans, leading to significant yield losses, particularly under hot and dry environmental conditions. The present study investigated the effects of soil temperature and moisture on sclerotial germination and infection behavior of M. phaseolina in bean plants. Controlled experiments were conducted to evaluate sclerotial germination rates, mycelial growth, host infection efficiency, and disease development under different combinations of soil temperature and moisture levels. The results demonstrated that both soil temperature and moisture significantly influenced sclerotial germination and pathogenic activity. Higher soil temperatures markedly enhanced sclerotial germination and accelerated mycelial growth, while optimal but limited soil moisture conditions favored infection and colonization of bean roots. Excessively high moisture levels, however, reduced infection efficiency, likely due to reduced aeration and unfavorable conditions for fungal establishment. Under combined high temperature and moderate moisture conditions, rapid disease development and severe root and stem infections were observed in bean plants. In contrast, low temperature and inadequate moisture significantly delayed germination and reduced pathogenicity. The interaction between temperature and moisture was identified as a key determinant of disease severity and pathogen survival in soil. The findings highlight the ecological adaptability of M. phaseolina and its strong association with warm, drought-prone environments. This study provides valuable insights into the environmental regulation of charcoal rot development and supports the development of predictive models and integrated disease management strategies aimed at reducing infection risk in bean cultivation systems.