CYTOGENETIC ANALYSIS OF CHROMOSOMAL TRANSLOCATIONS IN THE TOMATO: PREFERENTIAL BREAKAGE IN HETEROCHROMATIN

A tester set of eight translocations has been selected involving all 12 chromosomes of tomato (Lycopersicon esculentum Mill.). Using the entire tester set, seven other translocations were identified. Five others were identified, using information from crosses with certain of the testers and with additional translocations. Three lines are homozygous for two translocations (2 04 in the heterozygotes). There are several instances in which more than one stock involves the same two chromosomes. Cytological analyses of tomato translocations show that breakages that give rise to translocation chromosomes occur more frequently in centromeric and heterochromatic regions than in euchromatic and are not distributed according to pachytene chromosome length. A list of available tomato translocations with information on mode of production, source, and breakpoints is included.