REPRODUCTIVE ERRORS IN ANEUPLOIDS: GENERATION OF VARIANT EXTRA-CHROMOSOMAL TYPES BY TOMATO PRIMARY TRISOMICS

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Abstract
Primary trisomics of the tomato spawn an array of other primary trisomics as well as such modified types as secondary, tertiary, and telo-trisomics and primary tetrasomics. Five useful, previously undescribed trisomic types were thereby obtained. Although the frequency of deviant types is very low, they can be readily screened from the total population by their markedly differing phenotypes. It is therefore feasible to obtain specific desired types of aneuploids by systematically seeking them in progenies of the corresponding primary trisomic. The data suggest, although they are not sufficiently extensive to prove, that the deviating aneuploids tend to have shorter chromosomes of the tomato complement as their extra elements and tend to be more frequent in the progeny of trisomics for the shorter chromosomes. Cytological studies of triplo-5, the most prolific source of deviants, revealed a substantial frequency of laggards and chromosomes otherwise behaving abnormally at anaphase of both meiotic divisions, thus suggesting mechanisms to account for the origin of the deviant aneuploids.