Management of rust in faba bean by crop diversification

Trabajo presentado en Legume Science and Practice 2, celebrado online del 1 al 3 de spetiembre de 2021.Faba bean plays a key role in sustainable agriculture, given its ability to fix nitrogen. Rust is one of the most important diseases affecting faba bean. It is caused by the biotrophic fungus Uromyces viciae-fabae, whose windborn spores infect all aerial parts of the plant. The high economic and environmental cost of fungicides, and the scarcity of resistant cultivars adapted to the different agronomic situations make necessary to find alternatives for rust control. Crop diversification has been proposed as a sound option for disease management (Boudreau, 2013). We studied the potential for rust management in faba bean intercrops and in cultivar mixtures. First, we carried out four intercropping field trials across 3 years in two locations each one consisting of faba bean intercropped at 50% proportion either with wheat, barley or pea, in an alternate replacement system. Second, we performed four cultivar mixture field trials in which a resistant and a susceptible faba bean cultivars were mixed at different proportions (0–100, 25–75, 50–50, 75–25 and 100–0). A significant reduction of rust infection was recorded on faba bean when intercropped with barley but not when intercropped with wheat or with pea. Rust was also significantly reduced in cultivar mixtures, the reduction increasing with the proportion of the resistant cultivar in the mixture. Based on these results, additional experiments were performed on faba bean intercropped with barley seedlings inoculated under controlled conditions. Results confirmed rust reduction and suggested a barrier effect by barley as an important mechanism explaining that reduction. To further investigate the mechanisms behind disease reduction the combined effects of intercropping and nitrogen fertilization on rust disease will be assessed by experiments under controlled conditions