Does preferential pairing occur in Secale cereale × S. montanum tetraploid hybrids?

Abstract

SUMMARYMeiosis was examined in F1 hybrids between Secale cereale and S. montanum where tetraploidy had been induced by the use of colchicine. The frequency of ring bivalents was higher, and the average size of multivalents lower, than a model assuming random pairing of chromosome arms predicts. This is interpreted as evidence of preferential pairing.

Pairing competition between identical and homologous chromosomes in diploid and tetraploid cells of rye telotrisomic plants

“…Competitive situations, as in aneuploids and polyploids, have been analyzed on several occasions for detecting pairing preferences between chromosomes with different degrees of homology by using traditional staining techniques (John and Henderson 1962;Timmis and Rees 197 1 ;Elci and Sybenga 1976;Sybenga 1976;Jackson and Hauber 1982;Callow et al 1984;Chapman 1984) or by gene segregation (Doyle 1979a(Doyle , 1979b(Doyle , 1982.…”

“…Theoretical models have been developed to analyze meiotic pairing in such competitive situations because of the impossibility of distinguishing specific chromosomes at meiosis with conventional staining methods. Deviations from these models have usually been taken as evidence for preferential pairing (John and Henderson 1962;Sybenga 1975;Jackson and Hauber 1982;Callow et al 1984;Chapman 1984).…”

Evidence for preferential pairing in telotrisomic plants of rye

“…In both cases the frequencies of trivalents were higher at this stage than at metaphase I. Rees, 1971;Chapman, 1984 Usually, the lack of fit between the observed and expected values calculated by the two ways has been explained by the existence of pairing preferences. On the other hand, with conventional staining techniques it is impossible to identify each specific set and pairing preferences are detected indirectly as a deviation from 2/3 using the mean number of multivalents formed for all sets.…”

“…Most attempts to study pairing preferences in aneuploids and polyploids have been made from the analysis of meiotic configurations at metaphase I, with conventional staining techniques (John and Henderson, 1962;Timmis and Rees, 1971;Sybenga, 1975;Elçi and Sybenga, 1976;Jackson and Hauber, 1982;Chapman, 1984;Callow et aL, 1984). Due to the impossibility of distinguishing specific chromosome arms with such techniques, pairing preferences have been indirectly determined by using theoretical models often based on severe restrictions such as assuming that, 1. all chromosomes of different sets and all chromosomes within the same set have the same probability of pairing.…”

“…There are some discrepancies concerning the meiotic configurations which should be used for the approach. Timmis and Rees (1971) and Chapman (1984) only used those configurations with complete pairing in autotetraploid rye, because the remaining ones, in which any arm is not bound, could represent larger configurations that had degradated by chiasma failures.…”