Physiol. Plant. 48: 307-311, 1980 PHYSIOLOGY OF THE TOMATO MUTANT ALCOBACA 307 Physiology of the tomato mutant alcobaca By E. KOPELIOVITCH, Y. MIZRAHI, H. D. RABINOWITCH and N. KEDAR Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel, and (Y.M.) Department of Biology and Research & Development Authority, Ben Gurion University of the Negev, Beer-Sheva, Israel (Received 30 May, 1979: revised 20 August, 1979) Abstract Alcobaca is commonly regarded as an abnormally ripening mut- ant of the tomato (Lycopersicon esculentum Mill.). Alcohaca fruits were found to be similar to cv. Rutgers fruits in the follow- ing characteristics: time between full anthesis and the onset of ripening, response to ethephon, flavor, pH and concentrations of titratable acids, total soluble solids and reducing sugars. The pattern of CO2 and ethylene climacteric are similar in the two plant types, but the peak levels were lower and occurred later in alcobaca than in "Rutgers'. The mutant fruits differed from fruits of normal varieties in their greatly prolonged shelf life, their relatively low activity of polygaiacturonase (PG) and polymethylgalacturonase (PMG), and their low level of en- dogenous ethylene. Fruits of the mutant harvested before the onset of ripening failed to reach normal pigmentation and re- mained yellow. Fruits harvested at the onset of ripening reached an orange color, while fruits ripened while attached to the plant reached almost normal pigmentation. These results suggest that alcobaca is a slow ripening mutant and does not belong to the category of non-ripening mutants. Key words: Tomato; Lycopersicon esculentum; fruit ripening mutant; climacteric; ethylene; shelf life; pigments; pectin- methylesterase (PME); poiygalacturonase (PG); polymethylgalacturonase (PMG). Introduction While ripening criteria of the tomato fruit have been studied in great detail, the factors controlling the process are only partially known. The non-ripening mutants rin and nor were found to differ from normal tomato fruits in various parameters such as rate of respiration, rate of ethylene evolution, the presence and activity of pectolytic enzymes, membrane permeability, the presence and con- centration of pigments, and length of shelf life (Buescher etal. 1976, Herner and Sink 1973, ?oova\ah et al. 1975, Smketal. 1974, Tigchelaare/a/. 1976). It is possible that non-ripening mutants can serve as an excellent tool for the study of the processes controlling fruit ripening. Re- cently, an abnormally ripening mutant, alcobaca, has also been described; it probably originated in Portugal (Leal 1973, Leal and Tabim 1974) and reached the U.S.A. via Brazil. The mutant is characterized by its extended shelf life and the yellow color of its ripe fruits (Leal 1973, Leal and Tabim 1974), The long shelf life of this mutant facilitates its use for commercial breeding. The present work was aimed at studying a number of physiological parameters possibly connected with the ri- pening process and the prolonged shelf of a/cobaca fruits. Materials and methods Unless otherwise stated, the cv. Rutgers of tomato {Lycopersicon esculentum Mill.) was used as the control genotype. Alcobaca and 'Rutgers' plants were grown in a heated glasshouse and trained to a single stem; only two fruits per cluster were allowed to develop (Buescher er al. 1976, McGlasson 1970, Mizrahi et al. 1976, Ng and Tig- chelaar 1977, Poovaiaher al. 1975). Flowers were tagged at anthesis, and fruit size was measured daily commencing 19 days after anthesis. We defined the time required for 100% fruit development as the period between anthesis and maximum fruit size (Lyons and Pratt 1964, Mizrahi etal. 1976). Ethephon treatments were applied on the 26th day af- ter anthesis. Ten fruits of each genotype were dipped in 2% ethephon for 60 s. Ethylene and CO:.. For the determination of the rates of evolution of CO;, and ethylene, freshly picked fruits of 90% fruit development were weighed and sealed in 500-mI glass vials supplied with a continuous flow of air free of CO^ and ethylene. Every day, gas samples from the effluent air stream were analyzed in a Packard Gas chromatograph Model 804 with a T.C. detector for CO2 and Model 873 with an F.I.D. detector for ethylene. 0031-9317/80/020307-05 $03.00/0 € 1980 Physiologia Plantarum