Effects of different wheat cultivars intercropped with faba bean on faba bean Fusarium wilt,  root exudates and rhizosphere microbial community functional diversity

Field and pot experiments were conducted to examine effects of three different wheat cultivars［Yunmai 42（YM42），Yunmai 47（YM47） and Mianyang 29（MY29)］and faba bean intercropping on occurrence of faba bean Fusarium wilt, root exudates content and rhizosphere microbial community functional diversity. Results show that compared with the faba bean monocropping, the disease index of faba bean Fusarium wilt is significantly decreased by 47.6%in the yunmai 42 intercropped with faba bean system (YM42//B) and decreased by 33.3% in the yunmai 47 intercropped with faba bean system (YM47//B), while the disease index of faba bean Fusarium wilt is not significantly changed in the mianyang 29 intercropped with faba bean system (MY29//B). Compared with the faba bean monocropping, the YM42//B and YM47//B treatments significantly increase the total content of organic acids and significantly reduce the total content of soluble sugars and free amino acids in the root exudates. The total utilization ability of carbon sources is significantly increased and the microbial community structures of faba bean rhizosphere are altered under the YM42//B and YM47//B treatments, and the YM42//B treatment has more obvious effect than the YM47//B treatment. The MY29//B treatment has no significant effects on substrate utilization, total content of soluble sugars, free amino acids and organic acids in the root exudates and microbial community structures. The rhizosphere microbe of the YM42//B treatment could use more types of carbon source than the YM47//B treatment, and the carbon source types of sugars, amino acids and carboxylic acids used by rhizosphere microbe of the YM42//B treatment are quite different from the YM47//B treatment. The total content of organic acids in the root exudates is increased under YM42 and YM47 intercropped with faba bean, thus the rhizosphere microbial activity and diversity are improved, and more carbon sources are utilized by rhizosphere microorganisms. Meanwhile secretion of soluble sugar and free amino acid is inhibited by the YM42//B and YM47//B treatments. Our result illustrates that the interaction of root exudates and rhizosphere microbes is the main reason of affecting faba bean Fusarium wilt control. Effects of the intercropping on diseases control are influenced by wheat cultivars, and the YM42//B is the best, the YM47//B shows the medium effect and the MY29//B has no significant disease control effect.