Occurrence and chemical control strategy of wheat brown foot rot caused by Microdochium majus

Wheat brown foot rot (WBFR) caused by a variety of phytopathogenic fungi, is an important soil-borne and seed-borne disease of wheat. WBFR causes wheat lodging and seedling dieback, which seriously affects the yield and quality of wheat. In this study, 64 isolates of WBFR were isolated from different wheat fields in Yancheng city, Jiangsu Province, China. Three pairs of primers were used to amplify the fragments of the internal transcribed spacer (ITS), elongation factor 1 alpha (EF-1α) and RNA polymerase II subunit (RPB2) respectively, and the sequencing results of the fragments were analyzed with BLAST on NCBI. Through morphological and molecular identification, all the isolates were identified as Microdochium majus (Wollenweber) Glynn & Edwards. Koch's postulates verification confirmed that M. majus was the pathogen causing WBFR. Moreover, the antifungal activities of prochloraz and fludioxonil against 64 isolates of M. majus were determined based on the mycelial growth inhibition method. The results showed that fludioxonil and prochloraz had good antifungal activity against M. majus. The mean EC50 values of fludioxonil and prochloraz against M. majus were 0.2956±0.1285 μg/mL and 0.0422±0.0157 μg/mL, respectively. Pot experiments indicated that M. majus severely damaged the normal growth of wheat, while seed coating with prochloraz and fludioxonil significantly reduced the disease incidence and improved the seedling survival rates. At doses of 7.5g/100kg of fludioxonil and 15g/100kg of prochloraz, the incidence was reduced by 22.26% and 25.33%, seedling survival rates increased by 25.37% and 22.66%, and the control efficacy reached 70.02% and 72.30%, respectively. These findings provide vital references for accurate diagnosis and effective management of WBFR.