Genetic Diversity and Identification of Wilt and Root Rot Pathogens of Tomato in China.

Fungal wilt and root rot diseases affecting tomato have become prevalent in China in recent years and have caused considerable damage. In 2016 to 2018, symptoms of putative wilt and root rot diseases were observed in several locations in tomato cultivars with resistance to f. sp. races 1 and 2. The objective of this study was to identify the causative agents of wilt and root rot of tomato in China and provide a basis for disease prevention and resistance breeding programs. Based on DNA sequence analyses of the internal transcribed spacer (ITS) region, 91 isolates from the roots of tomato plants showing symptoms of wilt and root rot were identified, including (64 isolates), (11 isolates), (2 isolates), (2 isolates), (1 isolate), (6 isolates), sp. (2 isolates), and (3 isolates). accounted for 70.33% of the isolates obtained. In this case, using PCR-based methods for differentiation of , we identified several and races of : 7 isolates were identified as f. sp. race 1, 2 isolates as f. sp. race 2, 35 isolates as f. sp. race 3, and 13 isolates as f. sp. . Pathogenicity tests revealed 55 isolates of tomato wilt and root rot pathogens to be virulent. This study demonstrated that f. sp. race 3 was the most widespread and highly virulent race among these tomato pathogens in China, followed by f. sp. . Therefore, the development of resistant varieties of tomato against f. sp. race 3 and f. sp. would aid efforts to develop effective disease management strategies.