Ripening Behavior of Wild Tomato Species

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Abstract
Nine wild tomato species were surveyed for variability in ripening characteristics. External signs of ripening, age of fruit at ripening and ethylene production patterns were compared. Ethylene production was monitored using an ethylene-free air system and gas chromatography. Based on these ripening characteristics, the fruits fell into 3 general categories: those that change color when they ripen, green-fruited species that abscise prior to ripening and green-fruited species that ripen on the vine. The fruits that change color, Lycopersicon esculentum var. cerasiforme, L. pimpinellifolium and L. cheesmanii, exhibited a peak of ethylene production similar to the cultivated tomato; there were differences, however, in the timing and magnitude of the ethylene production. Peak levels of ethylene production are correlated with age at maturity. For the 2 spp. that abscise prior to ripening, L. chilense and L. peruvianum, ability to produce ethylene varied with stage of maturity. The 2 spp. differed from each other in time of endogenous ethylene production relative to abscission, suggesting differences in the control mechanisms regulating their ripening. For 2 of the green-fruited species that ripen on the vine, L. chmielewskii and L. parviflorum, ethylene production was correlated to fruit softening. For L. hirsutum and Solanum pennellii, however, ethylene production was not correlated with external ripening changes, making questionable the role of ethylene as the ripening hormone in these fruits.