CHIMERAS FOR MUTATIONS INDUCED IN DORMANT TOMATO SEEDS

Genetic chimeras of the VFNT cherry tomato line (Lycopersicon esculent um) were produced by mutagenizing seeds with ethyl methane sulfonate ( EMS). The chimeras thereby produced were evaluated by progeny-testing the fruits of the genetically mosaic tissue. A total of 2011 M(1) plan ts was grown from treated seeds and evaluated by screening their 95175 (M(2)) progeny for mutations affecting seedling phenotype. Three vigo rous and fertile M(1) plants bearing mutant progeny with definitive ph enotypes were selected for systematic harvesting and analysis. The spe cific location of each fruit was noted at harvest time, enabling the m utated sporogenous tissue of the mosaic M(1) plants to be traced. Sect oring appeared in both branch and floral tissues. In several cases, mu tant progenies were restricted to individual branches or parts thereof . True-breeding recessive mutants whose monogenic mode of inheritance was later established occasionally segregated within M(1) fruit progen ies at frequencies that indicate a non-homogeneous floral meristem ori gin. The data emphasize the necessity of making a well-distributed har vest of mosaic plants in order to detect as many variants as possible, as mosaic sectors may or may not recur late in ontogeny and may not c ontribute to sporogenous tissue early in development.