Adaptive role of interchange heterozygosity in the annual chrysanthemum

Physiological Characteristics Associated with Chromosomal Structure in <i>Chrysanthemum carinatum</i>

“…Certain interchange heterozygotes of C. carinatum have been reported to have evolved in the direction of relatively high degree of fertility by means of a directed type of disjunctional segregation of the interchanged chromosomes at metaphase-I (Rana and Jain 1965).…”

“…It was reported earlier (Rana and Jain 1965) that the observed frequen cies of interchange heterozygotes in several populations of Chrysanthemum carinatum were consistently more than those expected on theoretical con siderations.…”

“…It was observed during a cytological survey of seven populations of Chrysanthemum carinatum that the proportion of heterozygotes, for a particular interchange, to homozygotes ranged from 66.5 to 86.7 per cent (Rana and Jain 1965). While there are numerous reports on the preponderance of structural heterozygotes in relation to homozygotes for the original and the reconstituted chromosomes (For references see Darlington 1956, White 1956, Dobzhansky 1957, Lewis and John 1958, Hrishi and Muntzing 1960, Rees 1961, Snow and Dunford 1961, there is little information in general on those features of the hetero zygotes which account for their predominance over the homozygotes.…”

Cytomorphological Studies in some species of Chrysanthemum L. (Asteraceae)

“…It has been suggested by many investigations that the frequency of multiple formation and disjunction are under gene control (Lawrence 1958;Rees 1961). Rana and Jain (1965) reported involvement of same two pairs of chromosomes in the different populations of C. carinatum, whereas Paria and Pardhan (1971) reported the presence of different pairs of chromosomes in reciprocal translocations.…”

“…Overall 36.7% plants were homozygous with nine bivalent formation, 27.9% have one hexavalent with five bivalent, 11.76% have two quadrivalents with five bivalents and the remaining 16.1% have one hexavalent with one quadrivalent with four bivalents. Rana (1965) was able to synthesize an interchange stock of the species in which 12 of 18 chromosomes were involved in rearrangement and form a single multiple association during meiosis. It has been suggested by many investigations that the frequency of multiple formation and disjunction are under gene control (Lawrence 1958;Rees 1961).…”