TRI5 positive Fusarium graminearum strains isolated from different hosts cause root rot and head blight diseases of wheat ( Triticum aestivum L.)

Fusarium graminearum is an economically important pathogen of cereal crops. It causes Fusarium root rot (FRR) and Fusarium head blight (FHB) in wheat, posing a significant threat to food security by reducing wheat yields. The cropping pattern under intensive farming has led to the emergence of new pathotypes. This study aims to assess the pathogenic potential of F. graminearum strains isolated from different hosts on wheat. Twenty isolates (presumptively Fusarium spp.) were obtained from symptomatic plants of various crops, including wheat, maize, and grass. Four out of 20 isolates were identified as F. graminearum based on Trichodiene synthase (TRI5) primer and internal transcribed spacer (ITS) gene analysis. All these strains (n=4) caused Fusarium root rot and Fusarium head blight diseases in wheat susceptible varieties. The F. graminearum strain F1 was found to be highly virulent on both varieties, with a root rot disease score, i.e., Seher (2.9), Galaxy (2.1), and head blight disease score on Seher (5.5) and Galaxy (3.3). None of the strains caused disease on the resistant variety Akbar (disease score 0.6). The virulent strains caused a reduction in photosynthetic pigments, i.e., chlorophyll a, (24-68%), chlorophyll b (26-55%), and carotenoids (17-63%) over control in Seher (susceptible) and Galaxy (moderate susceptible). An enhanced activity of the malondialdehyde (MDA) (6-82%) and antioxidant enzymes was observed in plants inoculated with F. graminearum strains. A significant correlation was observed between the disease score and stress-related markers. These findings highlight the cross-host pathogenicity of F. graminearum on wheat prevailing in different field crops.