Fruit cuticular and agronomic characteristics of a lecer6 mutant of tomato

The agronomic and physiological characteristics of fruit were compared between two lines of 'Micro Tom' tomato which differed in their fruit cuticle chemistry. A wild-type (WT) and a mutant line (lecer6) deficient in -ketoacyl-CoenzymeA synthase (LeCER6), an enzyme involved in cuticular wax synthesis, were studied.The lecer6 line showed significantly lower levels of wax aliphatics and higher levels of terpenoids. Lecer6 fruit also had lower levels of cutin monomers than WT fruit. The agronomic characteristics of fruit from the mutant line were generally different from WT fruit. Osmotic values and dry weight percentages (% DW) were higher than in WT fruit. These findings can be explained by the higher water permeance of the lecer6 fruit cuticle, resulting in a higher rate of cuticular transpiration. Fruit from lecer6 plants were not as firm as WT fruit, which may also have resulted from excessive water loss through the cuticle. Higher rates of water loss in lecer6 fruit did not seem to be related to changes in cuticle thickness. The biomechanical properties of the cuticle also differed between the two tomato lines. Transient creep tests of isolated cuticles were used to generate stress-strain curves for the fruit cuticles of each line. At the immature (green) stage of development, cuticles of WT fruit were more elastic than those of lecer6 fruit, as shown by a lower elastic modulus. However, at the mature (red) stage of development,WT fruit cuticles had become more rigid, and no differences were apparent between the two lines. These data show that a single gene mutation for fruit cuticular wax synthesis has a pleiotropic effect on many important agronomic and physiological attributes.