GENETICS OF STEM RUST RESISTANCE CAUSED BY Puccinia graminis f. sp. avenae E. & H. IN OAT LINES

Stem rust is a major disease of cultivated oats (Avena sativa L) caused by the fungus Puccinia graminis f. sp. avenae. Genetic resistance of the plant is an effective strategy for controlling this disease and it is conferred by a relatively small number of genes. The aim of this study was to determine the genetics of the resistance to stem rust in the resistant oat line D0RA/OBS//I0RN. S97CV.8A (parent 18), from five biparental populations. Field results showed that stem rust resistance in susceptible x resistant crosses is determined by three genes, one dominant gene and a system of two complementary dominant genes, by grouping resistant families plus segregating families and comparing them with susceptible families a ratio of 57 resistant and 7 susceptible was observed. Results indicated that Agata.B/Diam is not a homozygous line; therefore, any segregation found for two dominant genes is not congruent with the segregation of three genes observed in resistant x susceptible crosses. No segregation was observed in a resistant x resistant cross, indicating that stem rust resistance genes are similar in both parents; however, the progenies of the population originated from a single F1 plant that could be attributed to a self-pollinated seed. To confirm this finding, the allelism test should be repeated. The complementary system found could be attributed to the Pg-a complex and the presence of another dominant gene not yet identified. The findings of this research will help in the development of resistant oat cultivars in the breeding programs of this cereal.