Inheritance of Resistance to Orange Rust (Puccinia kuehnii) in Sugarcane Families from Crosses Between Parents with Different Orange Rust Reactions

The aim of this study was to analyze the pattern of inheritance of resistance to orange rust (Puccinia kuehnii) in sugarcane families that originated from crosses between parental clones with different rust reactions. Eighty plants of eight families resulting from crosses between two resistant genotypes, four crosses between resistant and susceptible genotypes and two crosses between susceptible genotypes were analyzed. The progenies were assessed as to its severity with a diagrammatic scale and data were submitted to Chi square test to verify the hypothesis of a gene of major effect controlling resistance. Among the eight families, only one showed a pattern consistent with the hypothesis, suggesting that the resistance to rust may be controlled by one major gene and several genes acting quantitatively. The crosses of parental clones slightly susceptible resulted in a predominantly resistant progeny. There was occurrence of transgressive segregation, because even in crosses between two highly susceptible genotypes, resistant individuals to orange rust were obtained. Therefore, susceptible parents to orange rust should not be eliminated from sugarcane breeding programs.