Genetic parameters for agronomic traits of triticale and other small-graincereals grown on aluminium-toxic soil in southern Brazil

Aluminium (Al) toxicity is a major limiting Factor for plant production on acid soils. Breeding of adapted genotypes presents an alternative to correc tive lime application. This study estimated genetic and non-genetic compone nts of variation, heritabilities, and trait correlations for 20 triticale ( x Triticosecale Wittmack) genotypes grown for 2 years on naturally acidic, Al-toxic (pH 4.4) and lime-amended soils (pH 5.0 and 6.3). Eight traits wer e assessed. A 51% mean reduction in grain yield as a result of soil acidity was due to 27% fewer grains/spike, 11% fewer spikes/m(2) and 7% reduced 10 00-grain weight. Genotypes were the most important source of variation for nearly all traits in the combined analysis across years. Genotype x lime in teraction was relevant only for certain traits in a particular year. Despit e a substantial genotype x year interaction, the general ranking of genotyp es for acid-soil tolerance did not change across years. Genotypic variation was higher on acidic than on lime-amended soil. Heritability estimates wer e similar at the two extreme pH levels. Results suggest that in triticale a wide variation for adaptation to soil acidity exists. Selection under stre ss appears more effective than under optimal conditions. A visual plant-dev elopment-stress-symptom rating can be used to select indirectly for grain y ield in a breeding programme.