Association of avenalumin accumulation with co-segregation of victorin sensitivity and crown rust resistance in oat lines carrying the Pc-2 gene

Abstract

Avenalumin I production, resistance to rust and victorin sensitivity were examined in the progenies of crosses between the oat cv. Victoria (containing the Pc-2 gene) and Kanota, Pc-38 or Shokan-1. The F 1 plants accumulated avenalumin I to intermediate levels of that of Victoria in response to rust infection and the specific elicitor victorin. This suggested that there was a gene-dosage effect of Pc-2 on avenalumin production. Classification of the genotypes for Pc-2 of F 2 plants was successfully done by placing small segments of each primary leaf on a series of victorin dilutions and differentiating the degree of victorin-sensitivity. Sensitivity to victorin which differentiated Pc-2 genotypes, and resistance of the remaining portion of each leaf to rust races 202 and 226 co-segregated in the F 2 and F 3 progenies. Avenalumin accumulation in the lines containing Pc-2 was inherited as a co-dominant single gene factor. The F 2 plants (homozygous for Pc-2) accumulated significantly more avenalumin I than the heterozygous plants, whereas little accumulation of avenalumin occurred in the recessive plants in response to victorin and crown rust races 202 and 226. A detailed genetic analysis of the association between victorin sensitivity and rust resistance did not negate earlier reports that the gene conferring rust resistance and victorin sensitivity could be the same or a tightly linked gene. It was also found that there is at least one gene for resistance in addition to Pc-2 in Victoria, and this gene is closely linked to the Pc-2 gene. This other gene also controls avenalumin accumulation in response to infection by incompatible rust races. Separation of this gene from Pc-2 gene in Victoria will be necessary in order to study the recognition system of the Pc-2 gene to races 202 and 226 as well as victorin.