关键词: 黄曲霉, 黄曲霉毒素, 花生, 产毒力, 侵染力

Abstract:

【Background】Aspergillus flavus can easily infect peanut and other agricultural products, and the aflatoxin produced by A. flavus is highly toxic, teratogenic and carcinogenic, threatening human and animal health and causing significant agricultural economic losses.【Objective】Based on the previous research about the distribution of A. flavus in China, this study aims to further investigate the infection characteristics of A. flavus strains with different toxigenicity and geographical sources, so as to provide scientific basis for screening and breeding of peanut cultivars with resistance to A. flavus, as well as the early risk warning and control of aflatoxin contamination.【Method】A total of 102 strains of A. flavus isolated from different regions (early maturing peanut region in northeast China, large peanut region in north China, intercropping peanut region in spring and summer in Yangtze River, and double cropping peanut region in spring and autumn in south China) of China were identified as non-toxigenicity (ND), medium-low toxigenicity (0-1 500 μg·kg^-1) and high toxigenicity (>1 500 μg·kg^-1). The soaking method of the spores suspension was used to inoculate peanut seeds to identify the infection grade and infection index of A. flavus, and the infection difference of the strains and their correlation between different toxigenicity and different geographical sources were analyzed.【Result】The infection index of the 102 A. flavus strains to peanut was ranged from 3.89% to 67.50%. The proportion of A. flavus strains with intermediate or strong infectivity (the infection grade was 3 or 4, infection index>31%) accounted for 54.90%, and 18.63% of the total strains, mainly from Zhangshu in Jiangxi Province and Zhanjiang in Guangdong Province, were identified as intermediate or strong infectivity and high toxigenicity strains. Clustering and correlation analysis indicated that there was no significant correlation between the toxigenicity and infection index of A. flavus, however, the infectivity of toxigenic strains was significantly higher than that of the non-toxigenic strains. The infection index of medium-low toxigenicity and high toxigenicity strains accounted for the highest proportion in grade 4 and 3, respectively. Regional differences in the infectivity among the strains were analyzed. The results showed that average infection index of the strains from the south and the Yangtze River regions was 46.59% and 36.12%, respectively, and accounted for the highest proportion in grade 3 and 4. By contrast, the infection index of the strains from the northeast and northern regions was only 15.72% and 27.52%, respectively, and mainly distributed in grade 1 and 2. Strains from Guangdong Province, in the south China, had the highest average infection index (51.89%), while the average infection index of A. flavus in Liaoning Province, the northeast producing area, was the lowest, which was only 15.72%.【Conclusion】The infection characteristics of A. flavus and its relationship with toxigenicity and geographical sources were preliminarily clarified in this research. There was pathogenic differentiation among the strains, and the infectivity of the strains with different toxigenicity grades and geographical origins was significantly different. Strains with strong infectivity are mainly distributed in the south and Yangtze River regions of China. The results of this study are of great importance for the screening and breeding of peanut cultivars with resistance to A. flavus and the accurate early risk warning, prevention and control of aflatoxin contamination.

Key words: Aspergillus flavus, aflatoxin, peanut, toxigenicity, infectivity