Intercropping has been considered as a kind of a sustainable agricultural cropping system. In southwest China, maize/soybean strip intercropping has commonly been practised under local limited agricultural land resources. However, heavy rainfall in combination with high humidity and low temperatures cause severe pod and seed deterioration in the maturity and pre-harvesting stages of intercropped soybean. Numerous Fusarium species have been reported as the dominant pathogens of soybean root rot, seedling blight, as well as pod field mold in this area. However, the diversity and pathogenicity of Fusarium species on soybean pods remain unclear. In the current study, diseased soybean pods were collected during the cropping season of 2018 from five different intercropped soybean producing areas. A total of 83 Fusarium isolates were isolated and identified as F. fujikuroi, F. graminearum, F. proliferatum, and F. incarnatum-equiseti species complex based on morphological characteristics and phylogenetic analysis of the nucleotide sequence of EF1-α and RPB2 genes. Pathogenicity tests demonstrated that all Fusarium species were pathogenic to seeds of the intercropped soybean cultivar Nandou12. Fusarium fujikuroi had the maximum disease severity, with a significant reduction of seed germination rate, root length, and seed weight, followed by F. equiseti, F. graminearum, F. proliferatum, and F. incarnatum. Additionally, the diversity of Fusarium species on soybean pods was also considerably distinct according to the geographical origin and soybean varieties. Thus, the findings of the current study will be helpful for the management and resistance breeding of soybean pod decay in the maize/soybean intercropping system.

The separation of chemical components from wild plants to develop new pesticides is a hot topic in current research. To evaluate the antimicrobial effects of metabolites of Ligusticum chuanxiong (CX), we systematically studied the antimicrobial activity of extracts of CX, and the active compounds were isolated, purified and structurally identified. The results of toxicity measurement showed that the extracts of CX had good biological activities against Botrytis cinerea, Sclerotinia sclerotiorum, Alternaria alternata and Pythium aphanidermatum, and the value of EC₅₀ were 130.95, 242.36, 332.73 and 307.29 mg/L, respectively. The results of in vivo determination showed that under the concentration of 1000 mg/L, the control effect of CX extract on Blumeria graminis was more than 40%, and the control effect on Botrytis cinerea was 100%. The antifungal active components of CX were identified as Senkyunolide A and Ligustilide by mass spectrometry and nuclear magnetic resonance. The MIC (minimum inhibitory concentration) value of Senkyunolide A and Ligustilide against Fusarium graminearum were 7.81 and 62.25 mg/L, respectively. As a new botanical fungicide with a brightly exploitative prospect, CX extract has potential research value in the prevention and control of plant diseases.