Blossom-end rot and fruit cracking of tomato grown in net-covered greenhouses in Central Thailand can partly be corrected by calcium and boron sprays

Abstract

Two tomato (Lycopersicon esculentum Mill.) cultivars King Kong 2 (KK2) and FMTT 260 (FMTT) were grown in a net-covered greenhouse in Central Thailand to investigate the influence of fruit applications of combined aqueous calcium (Ca) and boron (B) solutions amended or not with the tenside Glucopon (R) on fruit yield and quality. Special attention was paid on blossom-end rot (BER) and fruit cracking (FC), two prevailing disorders in tomato and main causes for non-marketability of tomato fruits under the conditions of protected cultivation in Central Thailand. While no effect of the additional Ca and B applications on total fruit yield was observed, the composition of the non-marketable fraction of fruit yield differed significantly between treatments and cultivars. Cultivar KK2 proved to be highly susceptible to both BER and FC and, therefore, produced less marketable fruits than cv. FMTT. The Ca and B sprays decreased the incidence of BER but increased FC at the same time. Addition of the tenside Glucopon (R) to the Ca and B solutions did not yield any further advantage. The contrasting effect of the Ca and B sprays on BER and FC resulted in similar levels of non-marketable fruit yield in the treatments with or without the sprays for both cultivars. The nutrient status in different fruit segments was surveyed during fruit development. The Ca concentration in the distal end of the fruit during the time of rapid fruit growth was correlated with the BER incidence in mature fruits. Since additional Ca and B sprays are labor-intensive and did not significantly reduce the portion of non-marketable fruits, the selection of cultivars insusceptible to BER and FC appears to be of highest priority when conditions favoring these disorders are to be expected. This is particularly true for protected cultivation in Central Thailand.