Inheritance of nakedness in crosses between naked genotypes

Abstract

Nakedness in oats is genetically controlled by a dominant major gene, but it is not known if all oat varieties trace back to the same origin. To find out if different sources exist, we made crosses between naked oats. Spelt forms in segregating generations can only be expected in case of different origin of the major genes for nakedness in the parents. Starting with 75 crosses the segregating F2 generation could be obtained for 41 crosses. While 35 crossed yielded only naked oat plants, some spelt oat plants were detected in the remaining six crosses. Two of these crosses, both with the French accession AVE 2841 contained 1 to 2 % plants with hulled grains. Selfed progenies were raised from selected plants of the six crosses. Spelt oat plants were found, and the progenies of plants with clearly hulled grains were nearly uniform for hulled grains, but also segregating progenies with a varying degree of the expression of nakedness were observed. Phenotypic variation also exists in cross progenies between spelt and naked oat. The genetic basis was not the same in the parental naked genotypes. The French accession AVE 2841 carries a different major gene from the German (AVE 1296) and Finnish (AVE 1582). The small percentage of plants with hulled grains supports the hypothesis, that in all parents a dominant major gene for naked grains is responsible. We also found a small percentage of naked grains in selfed progenies from plants with hulled grains explained by minor genes. Seven microsatellites were used in the cross AVE 1296 x AVE 2841 to verify that spelt oat plants were derived from the cross between two naked oat plants. Only F3 plants were analysed, which themselves yielded hulled grains and had 2-3 florets per spikelet. All F3 plants went back to the cross of the two naked oat parents. Though not impossible, the risk of erratic plants is very low. In the F2 generation of another cross AVE 1287 (Finland) x AVE 2842 (Germany) only a few plants with spelt oat character were found. Also in this case some F3 plants with spelt oat phenotype were analysed with five microsatellite markers. But in this case two out of four plants could not be derived from the cross, since they showed foreign alleles for three or four microsatellites. This shows that even with a small number of plants a few microsatellites can be used efficiently to control the genotypes. There is strong evidence that the genetic basis of the French accession AVE 2841 is different from other accessions.