Analysis of Variance and Covariance of Chromosomal Association and Behavior During Meiosis in Clones of Dactylis glomerata

Abstract

In replicated data collected from nine clones of D. glomerata, significant differences among clones were found for number of chiasmata per chromosome, number of quadrivalents per sporocyte, frequency of univalents at metaphase I, frequency of lagging and dividing chromosomes at anaphase I, and frequency of micronuclei in the quartets. The correlation coeffs. (r) of quadrivalent frequency with metaphase I univalents and anaphase I laggards were not significant while r of chiasma frequency with metaphase I univalents was negative and significant. Significant positive values of r were obtained between chiasma frequency and quadrivalent frequency, metaphase I univalents and ana-phase I laggards, metaphase I univalents and micronuclei in the quartets, and anaphase I laggards and micronuclei. From the analyses of coyariance, it was found in all but one case that there were significant differences among clones in the dependent variable which could not be ascribed to its regression on the independent variable. The exception was in the relationship of anaphase I laggards with metaphase I univalents. Unequal distribution of chromosomes from quadrivalents occurred only rarely. Evidently the unpaired chromosomes at metaphase I play a major role in the production of aneuploid gametes in D. glomerata. In this regard, 3 of the 9 clones were comparatively regular in meiosis.