Formononetina como estimulante de micorrização em milho

Abstract

Brazilian agriculture is heavily dependent on imported phosphate fertilizers. Studies have proven the importance of mycorrhizal associations to supply phosphorus (P) for plants, including agricultural interests. The isoflavonoid formononetin is a biological stimulant such associations with strong potential for use in agriculture in order to reduce the need for application of phosphorus to soil. The present study aimed to evaluate the efficiency of formononetin (PHC-506) associated with P fertilization in maize (Article 1), and analyze the effects of formononetin on the density of diazotrophic bacteria (Article 2). Experiments were conducted at three locations in the State of Minas Gerais (Lavras, Ijaci and Uberlândia). The effects of PHC-506doses (0, 25, 50 and 100 g ha-1), in three P levels (0, 50% and 100% of recommended) on the rate of mycorrhizal colonization (TCM) and on different agronomic traits of corn (plant height, ear insertion height, 100 grain weight and grain yield) were evaluated. To assess the effects of formononetin on the density of diazotrophic bacteria in therhizosphere of maize plants, samples were inoculated into two culture media (FAM and NFB) semisolid. The bacterial densities in both media were determined by estimating the most probable number. It was concluded that the use of formononetin in field conditions stimulates the rate of mycorrhizal colonization and increases the grain yield of maize grown in low levels of phosphorus. The formononetin did not affect the density of diazotrophic bacteria in maize plants.