Objectives Intercropping and inoculation of arbuscular mycorrhizal fungus (AMF) are effective methods for controlling wilt in faba bean. Exploring the role of AMF and intercropping is the prerequisite for controlling faba bean wilt from soil microbial system.
Methods A greenhouse pot experiment was conducted using Funneliformis mossea (Fm) and Glomus tortuosum (Gt) as tested AM fungi. Six treatments were included as monocropped faba bean (CK), intercropping of faba bean and wheat (IF), monocropped faba bean with inoculation of Fm or Gt (MFFm or MFGt), intercropping of faba bean and wheat with inoculation of Fm or Gt (IFFm or IFGt). After faba bean grown for 70 days (in flowering stage), soil and plant samples were collected. The faba bean seedling growth, occurance of Fusarium wilt, rhizosphere microbial C metabolic activity in faba bean rhizosphere soil were measured.
Results In comparison with CK), intercropping significantly increased the dry weight of faba bean seedling by 93.0%, inoculation with AMF by 55.3% and intercropping combine with inoculation by 100%; significantly decreased disease index of faba bean Fusarium wilt by 71.4%, 76.6% and 89.8% respectively. Inoculation of Fm obtained higher dry weight of faba bean seedlings and stronger inhibition of disease index of Fusarium wilt. Studies based on Biolog micro plates showed that intercropping, AMF inoculation, intercropping combining with AMF inoculation increased the average well color development (AWCD value) by 32.3%, 85.4% and 122%. Principal component analyses demonstrated that intercropping, inoculation of AMF, intercropping combining with AMF inoculation changed the rhizospheric microbial community composition obviously, and utilization ability of carbohydrates, amino acids and carboxylic acids carbon sources were significantly increased when intercropping with inoculation AMF. Correlation analyses demonstrated that the disease incidence and index were significantly and positively correlated with the number of F. oxysporum in rhizosphere, and significantly and negatively correlated with AWCD value, Shannon’s diversity index and richness index.
Conclusions Intercropping with wheat and inoculation of AMF have positive effects on inhibiting Fusarium wilt and promoting the growth of faba bean. The intercropping could significantly increase the colonization rate of AMF, and the combination of the two method could further enhance rhizosphere microbial activity, improve rhizosphere microbial community functional diversity and inhibit the growth of Fusarium oxysporum. As a result, the faba bean plant growth is promoted, and the Fusarium wilt occurrence is reduced drastically.
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