Crown rust resistance in progeny from a derived tetraploid × natural tetraploid cross in Avena

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Abstract
The F1 plants and F2 and F3 populations obtained from a cross between the derived oat tetraploid C.I.7232 and natural tetraploid oat Avena barbata Pott. var. Excoimbra Se1.20 were evaluated for reaction to crown rust. The adult F2 plants exhibited a hypersensitive crown rust resistance reaction and were intermediate to their parents in other characteristics. The F2 and F3 seedling and adult plant populations differed in their response to the same mixture of crown rust races, i.e., a two gene segregation ratio at the seedling stage but only one gene segregation in adult plant tests. The resistance of Se1.20 was found to be a type of "stage" resistance that was effective only in vegetative (seedling) growth stages. The resistance gene of Se1.20 could not be detected in progenies that were rust tested as adult plants. Key words: Puccinia coronata, Avena, derived tetraploid.