Selection of elite Bradyrhizobium strains by biometric techniques for inoculation in cowpea

Abstract

Plant breeding programs seek to obtain genotypes with high yield, yield stability, and wide adaptability to environments. Selection of strains (genotypes) for adoption as crop inoculants has a similar aim. However, in both cases, the genotype × environment interaction hinders selection of materials adapted to the most diverse edaphic and climatic conditions. Nevertheless, with adequate biometric techniques, the variation in the response of each strain in the environments can be analyzed, allowing selection of those with the type of response and standard desired. In the present pioneering field study, the Toler and additive main effects and multiplicative interaction analysis models and the Annicchiarico method were used in a complementary manner with strains of nitrogen-fixing bacteria that are symbionts with cowpea to determine their adaptabilities and phenotypic stabilities. The adaptability and phenotypic stabilities of strains INPA 03-11B and UFLA 03-164 were confirmed by these techniques. These strains have the most stable behavior regardless of the environment. The reliability of adopting these strains exceeded 85%. The good response of strain UFLA03-164, still in the selection phase, is surprising, with results equivalent to application of mineral N, allowing it to be included among the strains approved as inoculants for cowpea.