关键词: 玉米-大豆带状套作, 大豆种腐病, 镰孢菌, 致病性

Abstract: For effective management of soybean seed decay and improvement of soybean yield and quality, it is
significantly important to find out the fungal species and their pathogenicity of soybean seed decay in maize-soy⁃
bean relay strip intercropping. During 2017-2018, the infected soybean seeds were collected from Renshou, Chong⁃
zhou, Nanchong of Sichuan Province, China, respectively. The fungi were isolated from these infected seeds and pu⁃
rified by hypha tip method, and identified based on morphological characteristic and sequence analysis of rDNA ITS
and EF-1α genes. The pathogenicity tests of the representative isolates were further conducted. Our results showed
that a total of 70 isolates were identified as 5 fungal species including Fusarium fujikuroi, F. equiseti, F. asiaticum,
Diaporthe phaseolorum and D. phaseolorum var. caulivora, with the separation frequency of 62.56 % , 21.43%,
10.00 %, 4.29 % and 1.43 %, respectively. Furthermore, the pathogenicity tests showed that all of the representa⁃
tive isolates belonging to five specie were able to cause seed decay of the intercropped soybean cultivar ND12 and
reduced seed germination and germ length. Fusarium asiaticum and D. phaseolorum had the highest mycelium cov⁃
erage area, and disease incidence with the disease index of 100. This study firstly reports that the Fusarium spp.
and Diaporthe spp. are the dominant pathogens of soybean seed decay in the maize-soybean relay strip intercrop⁃
ping system, which will provide basis for breeding of soybean resistant cultivar and disease management.

Key words: maize-soybean relay strip intercropping, soybean seed decay, Fusarium spp., pathogenicity