Faba bean–wheat intercropping and appropriate nitrogen supply control fusarium wilt in faba bean via altering specific amino acids in the root exudate of faba bean

With the increased continuous cropping of faba bean (Vicia faba L.), the incidence rate of Fusarium wilt in faba bean is increasing. The application of nitrogen fertilizer and intercropping of faba bean and wheat can affect the occurrence of the disease. In the field experiment, the effect of nitrogen fertilizer and faba bean - wheat intercropping on the occurrence of Fusarium wilt in faba bean was explored and the contents of 12 amino acids in the root exudate of faba bean were determined in a hydroponic experiment. Exudation amounts of seven amino acids were affected significantly. These were selected for an indoor culture experiment, and the effects of various concentrations of amino acids on the growth, reproduction, and pathogenicity of F. oxysporum f. sp. fabae (FOF) was studied. At 90 kg N ha−1, wheat-faba bean intercropping increased the content of in the root exudate of faba bean Ser, Glu, Tyr, and Lys which also inhibited the growth and reproduction of FOF while the content of Asp, Val, and Pro was reduced. The latter promoted the growth and reproduction of FOF. These results suggest, that changes in exudation patterns contribute to the observed reduction in the occurrence of Fusarium wilt in faba bean through intercropping and reduction of nitrogen input in the field. Optimum reduced N-applications combined with species mixtures should be identified and included in agricultural management.