The evaluation of germplasm as a tool in search of disease resistance genes in corn has been a constant target in breeding programs. With this end, it was determined through diallel crossing, the general (GCA) and specific combining ability (SCA) for resistance to Puccinia polyssora eight commercial corn hybrids at different levels of phosphorus fertilization. Were cultured 56 hybrid combinations (F1's and reciprocals) and eight parents in two different environments as the availability of phosphorus (low and high P), and evaluated the severity of disease attack, according to the area below the curve of disease progress. The analysis of variance indicated that the hybrids differed significantly (p<0.01) regarding the progress curve polissora rust, indicating the existence of genetic variability among hybrids in resistance to disease incidence. The largest mean square of GCA compared to SCA showed, these parents, the greatest contribution of additive gene action in the control of rust resistance polissora. The reciprocal hybrids P30F53 x AG 8060 and TRUCK x BM 2202 showed the largest negative average SCA in environments of low and high phosphorus, respectively, classified as promising for obtaining polissora rust resistance.
zea mays; puccinia polysora; biotic stress; breeding; genetic resistance
