Subgroup identification of Rhizoctonia solani, the causal agent of spinach foot rot, and pathogenicity comparison of the pathogens with the isolates belonging to related subgroups to spinach
2016
Misawa, T. (Donan Agricultural Experiment Station, Agricultural Research Department, Hokkaido Research Organization, Hokuto, Hokkaido (Japan)) | Hagiwara, A. | Ohhira, M. | Yamaguchi, T.
Basal petiole rot and leaf blight symptoms of spinach were observed in Hokkaido, Japan, in the autumn of 2013. Two isolates, which were obtained from each symptom, were identified as Rhizoctonia solani anastomosis group (AG) -1 IB and AG-4 HG-I on the basis of cultural appearance, mycelial growth temperature, hyphal anastomosis, and the result of specific PCR analysis. Pathogenicity to spinach of the two isolates and nine reference isolates obtained from various crops were compared after the artificial inoculation. The two present and seven reference isolates belonging to AG-1 IB, IC, AG-2-2 IV, IIIB, AG-4 HG-I and HG-II caused basal petiole rot and leaf blight, but reference isolates of AG-1 IA and AG-2-2 LP did not induce these symptoms. Although R. solani AG-1, 2-1, 2-2, 4, and 5 have been reported as the pathogen of spinach foot rot, subgroups of the pathogens were not identified in Japan. We confirmed that the pathogens belonged to AG-1 IB and AG-4 HG-I. Furthermore, our inoculation tests suggest that isolates of AG-1 IC, AG-2-2 IV, IIIB, AG-4 HG-II could be the pathogens of spinach foot rot.
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