II. 14. A new gene for semi-naked grain.
P. T. Gymer, Rothwell Plant Breeders Limited, Rothwell, Lincoln LN7 6DT, United Kingdom.
In our breeding programme we have found several lines having seminaked grain; on threshing, the hull remains attached on the ventral side only. The character is due to a single recessive gene, giving a 1:3 segregation in the F2 of crosses with hulled barleys. Two of our semi-naked lines were crossed to check allelism; the F1 and F2 generations were all semi-naked. The cross with a fully naked line (Nepal) gave in the F2 a 3:1 segregation of semi-naked: naked, with no fully hulled plants; thus Nepal also carries the semi-naked gene, which is hypostatic to the naked gene.
Scholz (1956) described three semi-naked mutants. Two of these were allelic; the two loci involved he symbolized as smn and sbn. We crossed one of our semi-naked lines with Scholz's mutants. Both Fl's had normal hulls; thus our semi-naked lines contain a different gene from those of Scholz. This has been assigned the gene symbol smn 2.
We made a number of crosses which enabled us to locate our semi-naked gene. The gene segregated independently of Fc (chromosome 1), V TV and msg 2 (chromosome 2), Ii (chromosome 4), int-a2 (chromosome 5), Oo and xn (chromosome 6) and ari-e1 (=lk 9 on chromosome 7). It was, however, linked with yc on chromosome 1:
Segregation in F3 lines from the repulsion cross semi-naked x ycyc
Recombination according to the maximum likelihood method = 29% + 3.88.
Reference:
Scholz, F. 1956. Mutations versuche an Kulturpflanzen V. Die Kulturpflanze 4:228-246.
