Effects of Fruit Thinning, Covering of the Fruit Truss and CO₂ Enrichment on Radial Fruit Cracking in Tomato Production under Rain Shelter in Cool Uplands

Abstract

Radial fruit cracking (RFC) can contribute to serious economic losses in tomato production under rain shelter in cool uplands. In order to investigate the effects of translocation and distribution of photosynthate to the fruits during the occurrence of RFC, tomato plants were grown under treatments with fruit thinning and CO₂ enrichment, which regulate the strength of sink and source, and treatments with covering of the fruit truss, which decreases solar radiation incident on the fruit surface. The occurrence of RFC was increased by fruit thinning and CO₂ enrichment, and decreased by covering of fruit truss. Time course of the percentage of RFC to total harvest showed a remarkable rise toward the end of August and toward the end of October in 2004, when harvested fruit weight was increasing. These finding suggest that RFC is attributed to excessive enlargement of the fruit by promotion of translocation and distribution of photosynthate from leaves (source) to fruits (sink) and the solar radiation incident on the fruits. In addition, the relation between RFC and the generation of a cork layer is considered.