Submitted to: Journal of Genetics and Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/1998
Publication Date: N/A
Interpretive Summary: Barley normally has 14 chromosomes, which occur in two sets of seven making the plant diploid. Chromosomes have two unequal sections or arms, joined in the middle by a centromere. Occasionally, the chromosome will break near the centromere and leave pieces of the long arm or short arm instead of a whole chromosome. Each chromosome is identified by a number (1) through (7). In barley, chromosome numbers other than 14 have been reported. We found a plant having 13 intact chromosomes and two broken ones. Cytological study indicated that this plant is different from a normal plant because it is missing one chromosome 6. The missing chromosome is replaced by two broken ones. One broken chromosome consists of the short arm and a fragment of the long arm. It is called acrocentric chromosome 6Sl. The other broken chromosome consists of the long arm and a fragment of the short arm of chromosome 6, or acrocentric chromosome 6Ls. When the plant self-pollinated, three chromosome types in the progenies were observed, including one having 14 chromosomes, one with 13+2 acrocentric chromosomes and one with 12+4 acrocentric chromosomes. Two acrocentric chromosomes compensated for the loss of one chromosome 6 and four acrocentric chromosomes replaced two missing chromosome 6. Since the plants carry extra fragments of the short and the long arms of chromosome 6, they are referred to as nearly compensating diploids. If the extra fragments contain beneficial genes, these plants may be useful for enhancement of barley germplasm.
Technical Abstract: A plant with 2n=13+2 acrocentric chromosomes was found in the progenies of an acrocentric trisomic plant (2n=14+1 acrocentric chromosome). Cytological study indicated that one acrocentric chromosome, acro 6S1, consisted of the short arm and 33% of the long arm of chromosome 6 (6H). The other, acro 6Ls, has the long arm and 23% of the short arm. When selfing, the plant with 2n=13+2 acros produced three chromosome types, including 2n=14; 2n=13+2 acros; and 2n=12+4 acros. Since the two acrocentric chromosomes compensate for the loss of one chromosome 6, and four acrocentric chromosomes replace two missing chromosome 6, they are referred to as nearly compensating diploids. These plants may be useful for genetic and breeding studies.