Effects of nitrogen deficiency induced by straw decomposition after incorporation into soil on the autophagy and pathogenicity of Fusarium graminearum based on an off‐line simulation

Abstract

AbstractThe high severity of plant diseases has hampered the implementation of straw incorporation technology in practice. To clarify the relationship between the nitrogen deficiency caused by wheat straw decomposition and Fusarium head blight (FHB) occurrence, five nitrogen levels as 0%, 25%, 50%, 75% and 100% were set to simulate the nitrogen changing after straw incorporated into soil and its effects on the pathogenicity of Fusarium graminearum. Nitrogen starvation degree was characterized by autophagy. Seedling infection and toxin production were used to test pathogenicity. The results showed that biomass of F. graminearum cultured in 25% nitrogen level medium for 72 hr and 120 hr were 0.39 g/ml and 0.29 g/ml, respectively, and were greater than those of other treatments at the same time (p < .05). The spore germination in 0%, 25%, 50% and 75% nitrogen level media were greater than those in 100% nitrogen level medium, in which the total nitrogen deficiency was the greatest (p < .05), reaching 64.5%. Total nitrogen deficiency would lead to F. graminearum autophagic death, while other treatments displayed different starvation responses in F. graminearum. F. graminearum cultured in 25% and 50% nitrogen levels media for 48 and 72 hr or in 75% nitrogen level medium for 168 hr produced more deoxynivalenol (DON). The lesion lengths caused by F. graminearum treated with 25%, 50% and 75% nitrogen levels for 72 hr were 18.33 mm, 15.78 mm and 14.96 mm, respectively, which were significantly longer than the lesions at the 0% (10.57 mm) and 100% (12.18 mm) nitrogen levels. The results indicated that the pathogenicity of F. graminearum was affected by nitrogen levels significantly and partial nitrogen deficiency could prompt the severity of FHB.