STUDIES ON THE INHERITANCE OF COVERED SMUT REACTION, LEMMA COLOR, AWN DEVELOPMENT AND RACHILLA PUBESCENCE IN OATS

Abstract

An oat cross, Black Mesdag × Victory, was studied genetically for covered smut reaction, lemma color, awn development and rachilla pubescence. Only the F3 was studied for reaction to the covered smut fungus, Ustilago levis (K. and S.) Magn. Prior to sowing, the caryopses were dehulled and inoculated with smut spores. Hybrid susceptibility (up to 95%) corresponded with that of Victory, the non-resistant parent. Segregation among F3 families occurred in the ratio 4 immune: 9 moderately resistant: 3 susceptible. It is concluded that smut resistance is conditioned by two genetic factors: a dominant factor, which when homozygous gives high resistance or immunity, and a less potent supplementary factor.Both the F2 and F3 were studied for the grain characters mentioned. Each of these characters was found to be controlled by two genetic factors. F2 segregation ratios were as follows:—lemma color, 12 black: 3 gray: 1 white; awn development, 12 strong: 3 intermediate: 1 weak; rachilla pubescence, 12 long: 3 short: 1 glabrous. The F3 gave good substantiation of the F2 ratios except in the case of awn development where fairly wide deviations from the expected occurred, due, it is believed, to environmental influences.No correlations between smut reaction and grain characters were found. Association between rachilla and callus pubescence was observed; but this is not believed to be due, necessarily, to a genetic linkage.Homozygous strains combining smut immunity with agronomically desirable grain characters were obtained.