MOLECULAR AND ULTRASTRUCTURAL ANALYSIS OF A NONCHROMOSOMAL VARIEGATEDMUTANT - TOMATO MITOCHONDRIAL MUTANTS THAT CAUSE ABNORMAL LEAF DEVELOPMENT

Mutants were recovered in a population of cybrids formed following pro toplast fusion between tomato (Lycopersicon esculentum Mill.) cv UC82 and Lycopersicon pennellii Corr. The cybrids were identified as indivi duals with recombinant cytoplasmic genomes but only tomato nuclear gen omes. The mutants were identified based on two features, a variegated sectoring of light and dark green regions on their leaves, stems, and fruit, and reduced growth in the field. The mutants produced 50% of th e shoot fresh weight and 20% of the fruit fresh weight of the parental type, UC82. The variegated sectoring was maternally inherited. The ch loroplast genome in the mutants was indistinguishable from the chlorop last genome in UC82, when distribution of restriction endonuclease sit es was used as an assay. The mitochondrial genome in the mutants, howe ver, was recombinant, containing genes from UC82 and L. pennellii. Lig ht microscopic analysis of the leaves of the mutants demonstrated an a bsence of the palisade layer in the variegated sectors. Electron micro scopic analysis of these same regions demonstrated an absence of norma l inner membranes in the mitochondria of these cells.