Chemical regulation of ripening of processing tomatoes in the field

Abstract

In a three year field study, the effects of the plant growth regulant (2-chloroethyl)phosphonic acid (ethephon) were observed on transplanted and direct-seeded tomato plants of the Roma and Napoli cultivars in the Richmond, Mudgee, Wellington, and Narromine tomato growing areas of New South Wales. Ethephon increased the percentage yield of usable fruit from a single harvest when applied at a concentration of 300-1 000 mg l-1 to crops containg 0-38 per cent usable fruit. The optimum yield of Napoli fruit was obtained when ethephon was applied to a crop containing about 30 per cent usable fruit and the harvest made some 15-20 days later. The compound 2-(4-chlorophenylthio) ethyldiethylammonium chloride (CPTA), which induces the synthesis of lycopene in many plant tissues, did not increase the rate of accumulation of usable fruit when compared with untreated crop. When used in a combination treatment with ethephon, CPTA did not increase usable fruit accumulation compared with ethephon treatment.