Comparative Analysis of Pathogens of Rice Spikelet Rot Disease in Heilongjiang, Sichuan and Hainan Provinces

The objective of this study is to identify the pathogenic species and dominant pathogens of rice spikelet rot disease (RSRD) in Heilongjiang, Sichuan and Hainan provinces of China, and to provide reference for accurate prevention and control of RSRD.

RSRD samples were collected from 13 major rice production areas in Heilongjiang, Sichuan and Hainan provinces. A total of 568 strains were isolated and purified by tissue separation and single spore separation methods. Morphological identification methods were performed for each strain, combined with rDNA-ITS sequence analysis and Koch’s rule verification and identification of RSRD pathogens in 13 major rice production areas. The dominant strains and pathogenic characteristics were analyzed.

There were three categories of pathogens of RSRD in Heilongjiang Province, they were Curvularia, Alternaria and Fusarium, and which accounted for 1.10%, 83.43% and 15.47% of the total pathogens, respectively. Alternaria was the dominant strains in Heilongjiang Province. In Hainan Province, there were Curvularia, Fusarium, Nigrospora, Lasiodiplodia and Exserohilum species of RSRD pathogens, which accounted for 1.62%, 89.47%, 0.81%, 1.62% and 6.48% of the total pathogens, respectively, and Fusarium was the dominant strains. There were Curvularia, Alternaria, Fusarium, Nigrospora and Exserohilum species of RSRD pathogens in Sichuan Province, which accounted for 23.57%, 13.47%, 22.86%, 16.43% and 23.57% of the total pathogens, respectively, and no dominant strain. According to the differences of conidia and colony morphology, 23 representative strains were selected, and then rDNA-ITS sequence analysis and Koch’s rule verification were combined. The pathogens of RSRD were identified as C. lunata of the genus Curvularia; A. tenuissima, A. alternata, A. brassicae of the genus Alternaria; F. verticillioides, F. andiyazi, F. equiseti, F. incarnatu, F. chlamydosporum of the genus Fusarium; N. oryzae, N. sphaerica of the genus Nigrospora; L. theobromae of the genus Lasiodiplodia and E. rostratum of the genus Exserohilum. The pathogens of RSRD were inoculated both at booting stage and heading and flowering stage, respectively. It was found that whether japonica or indica rice, the average disease index of pathogen of heading and flowering stage inoculation was higher than that of inoculation at booting stage in Hainan Province; while the pathogens’ average disease index of heading and flowering stage inoculation in Heilongjiang and Sichuan provinces was slightly lower than that at booting stage inoculation.

The pathogens of spikelet rot disease in Heilongjiang, Sichuan and Hainan provinces of China were diverse. The dominant strain was Alternaria in Heilongjiang Province and Fusarium in Hainan Province. The dominant strain was not obvious in Sichuan Province.