Intercropping with wheat suppressed Fusarium wilt in faba bean and modulated the composition of root exudates

Abstract

The causal agent of Fusarium wilt in faba bean is Fusarium oxysporum f. sp. fabae (FOF), which significantly reduces the yield in continuous cropping systems. We aimed to evaluate the role of wheat in alleviating Fusarium wilt in faba bean. We assessed the effect of wheat on the occurrence of Fusarium wilt in faba bean and analyzed the differences in the root exudates produced by faba bean in monocropping and intercropping systems before and after infection by FOF. Treatment with FOF increased the incidence and disease index of Fusarium wilt and significantly increased the number of rhizosphere pathogens. Phenolic acids, organic acids, amino acids and sugars exuded from the roots of faba bean increased by 39.1%, 329.0%, 921.7% and 1195.7%, respectively, while intercropping reduced them by 28.04%, 55.69%, 79.10% and 78.75%, respectively. The rhizosphere pathogens of faba bean decreased significantly following intercropping, and the incidence of Fusarium wilt dropped to tolerable levels. This study suggests that the inoculation with FOF stimulated the exudation of phenolic acids, organic acids, amino acids and sugars from faba bean roots. These compounds were closely related to the changes in the disease resistance of faba bean and could also be used as nutrients to promote pathogen proliferation. After intercropping with wheat, the exudates of faba bean decreased significantly, which may imply that the faba bean recovered from stress, reduced the amount of nutrients needed for pathogen growth, limited the proliferation of pathogens and contributed to the alleviation of Fusarium wilt.