Reducing the Severity of Fusarium Wilt in Common Beans ( Phaseolus vulgaris L.) by Coinoculation of Rhizobium tropici and Azospirillum brasilense

Root diseases caused by Fusarium oxysporum f. sp. phaseoli are major limiting factors for grain production of common beans in Brazil. The use of antagonistic bacteria can inhibit and reduce the incidence of the disease. This study aimed to evaluate the effect of co‐inoculating with Rhizobium tropici and Azospirillum brasilense on the severity of Fusarium wilt in five common bean cultivars. Three field experiments were conducted with five common bean cultivars (Pérola, BRS Estilo, BRS Notável, BRS FC402, and BRS FC104) and three nitrogen sources (coinoculation, nitrogen fertilization, and absolute control), arranged in a randomized complete block design with a 5 × 3 factorial arrangement and four replications. The inclusion of various N sources, such as mineral fertilizer and biological fixation, was crucial to understanding how nitrogen availability and form influence plant resistance, rhizosphere interactions, and grain yield (GY) under Fusarium pressure. Fusarium wilt severity was determined throughout the growth cycle, and GY was determined at physiological maturity. Pérola and BRS FC402 were more resistant to Fusarium wilt than BRS Estilo and BRS FC104. Coinoculation improved resistance by 5% compared to nitrogen fertilization and by 10% compared to the control. The coinoculated cultivars were capable of maintaining yields comparable to nitrogen fertilization. Thus, the severity of Fusarium wilt in common bean is influenced by a combination of cultivar resistance, nitrogen fertilization, and coinoculation of beneficial microorganisms that can provide GY similar to the N‐fertilized condition. In addition, the results demonstrate that coinoculation with Rhizobia and Azospirilla can reduce the severity of Fusarium wilt in common beans, suggesting an ecological and sustainable alternative to chemical control, while promoting plant growth and nitrogen fixation.