Inheritance and expression of the naked-grained and fatuoid characters in oats

In both hulled and naked oat (Avena sativa L.), aberrant "fatuoid" plants can occur; these can be recognized by their prominent twisted and geniculate lemma awns. Fatuoids of hulled oat cannot be used as cultivars because their grain shatters from the plant. In contrast, fatuoids of naked oat do not shatter and can be used as cultivars. In naked oat, occasional hulled grains may occur, detracting from grain quality and consistency. Some fatuoid lines of naked oat have been observed to produce few hulled grains. Here, we used crosses involving two fatuoid naked oat lines and three nonfatuoid oat cultivars (one hulled and two naked) to study the inheritance of the naked-grained and fatuoid characters. Phenotypic ratios observed in the F2 generation were not consistent with codominant single-gene models for either character. Dominant single-gene models in which the hulled and fatuoid alleles are recessive, and for which the expression of the dominant gene is variable, were satisfactory in some, but not all, crosses. Within F2 populations, true-breeding fatuoids could be quite reliably selected on the basis of the presence of two or more geniculate lemma awns per spikelet, while true-breeding nonfatuoids could be quite reliably selected on the basis of the absence of geniculate lemma awns. In naked oat, fatuoid plants tended to produce fewer hulled grains than nonfatuoid plants, suggesting that the fatuoid condition may enhance the expression of the naked-grained character. Despite the lack of a complete understanding of the genetic control of the naked-grained and fatuoid characters, it should be possible and useful to develop fatuoid naked oat lines for use as cultivars.