Genetic and phenotypical correlations, path analysis and genetic gain in two populations of corn with resistance to leaf spot, rust, and blight disease

Phenotypic and genotypic correlations of agronomic traits with resistance to phytopathogens can help identify indirect selection criteria for corn yield. The Brazilian corn cultivar NAP5 is resistant to leaf spot and blight disease, while NAP7 is resistant to rust disease. Trials were conducted in two states from February to July 2015. The following traits were evaluated: GY - grain yield, PH - plant height, EH - ear height, MF - days to male flowering, NP number of plants, NE - number of ears, BP - number of broken plants, LP - number of lodged plants, KW - kernel weight, HT resistance to the fungus Exserohilum turcicum, WS (white spot) resistance to Pantoea ananatis, CS - resistance to corn stunt, PP resistance to Puccinia polysora and CZ - resistance to Cercospora zeae-maydis. The NAP5 population showed high genetic correlations between GY and PH, NP, NE and CS in Jatai, GO. In Uberlandia, MG, NAP5 presented high correlations between GY and PH, NP, NE, WS and CS. For the NAP7 population, genetic correlations were high between GY and CS in Uberlandia and between GY and NE in Jatai. Genetic gains for GY by direct selection ranged from 29 to 31%. The influence of the location was low. NE had the greatest effect on grain yield. For the NAP5 population, indirect selection for yield through selection for NE gave satisfactory genetic gain. The variable NE affected KW, and could be used for indirect selection, though direct selection provides greater gains. The heritability estimate for GY (0.77) in the NAP5 population was higher than for NE (0.61). With direct selection, it is possible to obtain gains of up to 31% in GY. High genetic correlations were also observed in the NAP5 population between NE, GY and CS.