Peanut smut (causal agent Thecaphora frezzii) and seasonal drought are the two main factors reducing peanut yields in Argentina. There are no previous studies about the effect of drought on peanut smut occurrence. We evaluated the effect of soil water limitation on smut symptoms in greenhouse and field assays. Additionally, we analysed the biochemical responses of plants to the combined stress caused by water limitation and smut infection in greenhouse experiments. We found that a moderate water deficit (30% of soil water-holding capacity) increased smut symptoms and differentially increased proline and reduced chlorophylls in the host. Subsequently, we studied the correlation between field precipitation data and smut damage from 2015 to 2020 in naturally infected fields with a high T. frezzii spore load in the soils. Strong correlations between precipitation and severely affected pods, severity disease index and incidence were found from January to March (susceptibility window for T. frezzii infections). We suggest a strategy of irrigation in a specific time frame to mitigate smut damage when there is a water deficit in the growing season.

Currently, soil-borne fungal disease (SBFD) have caused a huge damage in agriculture, and small molecule soil disinfectants have been widely used for the prevention and control of SBFD, which could not only kill the chlamydospore of pathogenic fungi, but also completely destroy the microbial community and its functional diversity in the soil, and is not conducive to subsequent plant planting. Therefore, how to effectively inhibit plant pathogenic fungi while maintaining the general balance of microbial population in the soil to facilitate subsequent plant planting come to be critical problem in the prevention and control of SBFD. In this work, a series of polyacrylamide containing quaternary ammonium salts (PAM-X) were synthesized based on the radical copolymerization of acrylamide (AM) and acrylamide containing different quaternary ammonium salts groups (AMX). Owing to the entanglement between polymer chains and soil, PAM-X could be stably absorbed in the soil, thus effectively delaying the free migration of PAM-X chains in soil, and reducing the probability of being leached from soil, which might be the key to obtain novel polymeric quaternary ammonium salts that have less impact on the environment. Banana Fusarium wilt, also known as banana cancer, caused by Fusarium oxysporum f. sp. cubense (Foc), was chosen as a typical soil-borne pathogen disease to verify the rationality of the above thoughts. The results showed PAM-X had well anti-Foc4 activities in soil, and could maintain the general balance of microbial population in the soil, which are almost non-toxic to earthworms in soil and fish, thus provides a new prevention and control method for SBFD.