HETEROPLOIDY AND CHROMOSOME INTERDEPENDENCE IN BARLEY (HORDEUM VULGARE): CYTOLOGICAL AND BREEDING BEHAVIOR OF AN EIGHT CHROMOSOME PAIRED BARLEY.

Abstract

The cytological and breeding behavior of barley with 8 pairs of chromosomes, of which 2 pairs are interdependent were evaluated. The 8II material originated from selfed progeny of a Balanced Tertiary Trisomic 57a msg16. Chromosome interdependence was established after a naturally occurring reciprocal translocation between the normal chromosome 5 and the extra interchanged 57a chromosome. The interdependent chromosomes are fragment chromosomes. A Male Sterile Facilitated Recurrent Selection Population (MSFRSP) of 8II plants was developed. Eight chromosome paired plants were crossed onto male sterile plants from barley Composite Cross XXXII. The F₁ plants from the 7II x 8II crosses carried a characteristic 15-chromosome cytotype. In the F₂ of this cross, 5 different cytotype classes of progeny were isolated by root-tip chromosome and microsporocyte analyses: 7II, F₁, 8II, tertiary trisomic where the extra chromosome is a fragment chromosome and a Unique-16 chromosome cytotype which consisted of 6 normal pairs, one pair of fragments, one normal chromosome 5 and one fragment chromosome from the other pair of fragments. The F₂ population was approximately 30% 7II, 50% F₁ and 20% 8II cytotype progeny. Microsporocytes observed from F₂ cytotype plants indicated that the 7II and 8II progeny went through normal meiosis. The F₁ cytotypes produced functional gametes with 7 normal chromosomes, 8 chromosomes equivalent to gametes produced by 8II plants and gametes with 7 normal chromosomes plus a fragment chromosome. The tertiary trisomic progeny produced functional gametes with 7 normal chromosomes and gametes with 7 normal chromosomes plus a fragment chromosome. The Unique-16 cytotype produced functional gametes with 7 normal chromosomes, 8 chromosomes equivalent to gametes produced by 8II plants, 7 chromosomes plus a fragment chromosome and 9-chromosome gametes with 6 normal chromosomes plus 3 fragment chromosomes, two of which are a pair. Crosses and their reciprocals between 7II plants and plants of each F₂ cytotype indicated that the cytological stabilty of an 8II or 7II population would be disrupted if contaminated by pollen from 7II or 8II plants respectively. Growing the populations in physical isolation from each other is a must in order to maintain the cytotype of the population homozygous