CHARACTERIZATION OF THE GREEN RIPE (GR), LUTESCENT (L), HIGH PIGMENT (HP), AND DARK GREEN (DG) MUTANTS OF TOMATO (LYCOPERSICON ESCULENTUM MILL.)

ROBERT LAWRENCE JARRET, Purdue University

Abstract

Four mutants of tomato (Lycopersicon esculetum Mill.) were characterized in order to assess either their potential as germplasm for crop improvement (high pigment (hp), and dark green (dg)) or their suitability as tools for ellucidating physiological processes associated with ripening (green ripe (Gr) and lutescent (l)). Gr is a dominant mutation which greatly protracts the time for ripening processes to occur. Maximal rates of postharvest C(,2)H(,4) and respiratory CO(,2) in Gr fruit were achieved 20 to 30 days after initial increases. Carotenoid accumulation and chlorophyll loss are attenuated by Gr and the rates of their occurrence are diminished. Polygalacturonase (PG) activity in mutant fruit increases with age but reaches only 2% to 5% of that present in 'Rutgers.' Heat inactivation studies suggest that only a single isoenzyme of PG is present in enzyme extracts from Gr fruit. The mutation lutescent (l) conditioned a rapid and spontaneous loss of chlorophyll in all plant tissues. Chlorophyll loss did not appear to be strictly a function of physiological age or the result of a translocatable stimulus. The absence of chlorophyll in mature green mutant fruit did not affect lower levels of ascorbic acid in mature fruit or alter the synchronization or magnitude of other ripening processes. The hp and dg genes condition increased fruit chlorophyll and asorbic acid content. The effects of dg were more pronounced than hp. Ascorbate in mutant fruit was increased at all stages of development and in all fruit portions. Vitamin C in ripe fruit was increased 160% and 170%, and chlorophyll in outer pericarp of mature green fruit 166% and 350% by hp and dg respectively. Chlorophyll of inner fruit portions, and various ripening processes including postharvest C(,2)H(,4) and CO(,2) evaluation rates and PG activity, were uneffected by either gene. Undesirable pleiotropic effects were associated with both mutations. Soluble solids were reduced 5% and 13% hp and dg respectively. Mutant fruit were smaller and more elongate and vegetative and reproductive development were retarded by hp and dg.

Degree

Ph.D.

Subject Area

Botany

COinS