Higher relative humidity and more moderate temperatures increase the severity of rice false smut disease in the rice–crayfish coculture system

Abstract

AbstractRice false smut, a devastating grain disease in rice, is a great challenge to global food security. Rice–crayfish coculture (RC) has been widely used in recent years because it increases farmers' income, stabilizes rice yield, and reduces the use of pesticides and chemical fertilizers. Currently, rice false smut is becoming a threat to the stability of RC systems. A field experiment demonstrated that rice false smut in RC was much more serious than the disease in rice monoculture (RM) among most rice varieties in both 2019 and 2020. The fold change (RC vs. RM) range of the disease index of different rice varieties ranged from 1.23 to 19.35. Some varieties displayed resistance to rice false smut in RM, but were susceptible in RC, suggesting that the RC system that utilizes deep water irrigation is a better model than the RM to evaluate the resistance of rice varieties to false smut. Under the RC system, varieties YG 16, GBYJZ, and HD 5 displayed good natural resistance to rice false smut. A three‐way ANOVA with year, rice varieties, and culture types as factors showed that each factor had highly significant effects on the disease index. To identify the main factors causing differences between the RC and RM systems, we recorded the field microclimate around rice panicles. In comparison with RM, RC showed higher relative humidity (RH) and more moderate temperatures from the rice booting stage to early filling stage. Under simulated conditions of RC and RM, the germination rate of U. virens conidia under RC was significantly higher than that under RM. These findings indicate that higher RH and more moderate temperatures increase the severity of rice false smut disease in the RC system, and this provides unique insights into how to manage the threat of rice false smut.