Abstract
Fusarium species are the most detrimental pathogens of soybean root rot worldwide, causing large loss in soybean production. Maize/soybean relay strip intercropping has significant advantages on the increase of crop yields and efficient use of agricultural resources, but its effects on the occurrence and pathogen population of soybean root rot are rarely known. In this study, root rot was investigated in the fields of the continuous maize/soybean strip relay intercropping and soybean monoculture. Fusarium species were isolated from diseased soybean roots and identified based on sequence analysis of translation elongation factor 1α (EF-1α) and RNA polymerase II second largest subunit (RPB2), and the diversity and pathogenicity of these species were also analyzed. Our results showed that intercropping significantly decreased soybean root rot over monoculture. A more diverse Fusarium population including Fusarium solani species complex (FSSC), F. incarnatum-equiseti species complex (FIESC), F. oxysporum, F. fujikuroi, F. proliferatum and F. verticillioides, F. graminearum and F. asiaticum was identified from intercropping while FSSC, FIESC, F. oxysporum, F. commune, F. asiaticum and F. meridionale were found from monoculture. All Fusarium species caused soybean root infection but exhibited distinct aggressiveness. The most aggressive F. oxysporum was more frequently isolated in monoculture than intercropping. FSSC and FIESC were the dominant species complex and differed in their aggressiveness. Additionally, F. fujikuroi, F. proliferatum and F. verticillioides were specifically identified from intercropping with weak or middle aggressiveness. Except for F. graminearum, F. meridionale and F. asiaticum were firstly reported to cause soybean root rot in China. This study indicates maize/soybean relay strip intercropping can reduce soybean root rot, change the diversity and aggressiveness of Fusarium species, which provides an important reference for effective management of this disease.
Highlights
Fusarium root rot has been considered as one of the most destructive soil-borne diseases in almost all soybean growing areas worldwide and causes a drastic reduction in the optimum yield and the substantial economic losses [1]
We found that disease incidence (DI) of soybean root rot was steady from 2015 to 2017 in both cropping patterns, whereas a significant increase (p < 0.05) was observed in 2018 when the DI reached up to 61.02% in monoculture and 24.28% in intercropping, respectively (Figure 1A)
The effects of maize/soybean relay strip intercropping on soybean root rot, the diversity and pathogenicity of Fusarium species were investigated in a continuous location field experiment when compared with soybean monoculture
Summary
Fusarium root rot has been considered as one of the most destructive soil-borne diseases in almost all soybean growing areas worldwide and causes a drastic reduction in the optimum yield and the substantial economic losses [1]. The diversity and pathogenicity of these Fusarium species can be often affected by climate factors, soybean cultivars, cropping pattern and other agricultural practices. High disease-resistant cultivars of soybean are still lacking [9,10], several other disease management practices including chemical fungicides [11], biological control agents [12,13], crop rotation/intercropping [14,15] and tilling [16], have been commonly adopted to control the Fusarium root rot. Recent research indicated that intercropping reduced the occurrence of Phytophthora blight of pepper in maize/pepper intercropping [25], suppressed the incidence of Fusarium wilt of watermelon in rice/watermelon intercropping [26] and wheat/maize intercropping [15,27], and soybean red crown rot caused by Cylindrocladium parasiticum in maize/soybean intercropping [14]
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