II. 15 The deficiens allele.
P. T. Gymer, Rothwell Plant Breeders Limited, Rothwell, Lincoln LN7 6DT, United Kingdom.
From time to time, barley lines having the deficiens type of lateral florets appear in our breeding programmes. The origin is usually Ethiopian lines which were used because of their disease resistance.
Within the deficiens types there are different degrees of reduction of the lateral florets, and pure-breeding lines exist having almost continuous variation from normal two-rowed barleys to barleys having the laterals represented only by one small outer glume.
We have intercrossed quite a number of different deficiens lines; in every F2 population there are only deficiens plants. This indicates that the deficiens phenotype is always caused by a special allele (Vt) which, as we know from the literature, is at the Vv locus on chromosome 2. We do not yet know whether the variations in degree among deficiens genotypes are due to the existence of different Vt - type alleles or to modifying genes elsewhere in the genome.