Effects of Double-shoots Training Cultivation on Plant Growth and Fruit Productivity in Processing Tomato (Solanum lycopersicum L.)

Abstract

Recently tomatoes are one of the popular and important vegetables for human food and/or health in lots of countries (Bhowmik et al., 2012; Canene-Adams et al., 2005; Doralis et al., 2008). Among them, processing tomatoes are cultivated for using processed products such as juice, ketchup sauce, paste, and puree etc. Growers are producted them generally under contract with a processing company (Takemoto, 1992), and have the characteristics of determinate-type plant, having a low plant height, and evenly fruited and mature, and having a hard skin (Ito, 1976). Most of them are generally cultivated without support in the open field (Yanokuchi, 1997). This cultivation method has the advantage of requiring less labor and materials (Ito, 1992; Sato et al., 2004). In the future, it is necessary to increase fruit productivity; saving more labor and cost by mechanized cultivation (Mitchell et al., 2012), expanding the scale of management, high labor productivity, and align the flowering period that is convenient for almost one-time harvesting (Ohta and Ikeda, 2017). When the ripening period would be longer, labor productivity is higher, and the efficient management for growers due to work such as the weeding, side dressing, chemical spraying for diseases and pesticides is difficult (Ito, 1976). In general processing tomatoes are grown in the open field, however, there are some problems that the fruits are apt to contact with the surface of the soil and mulch and the incidence of disorders such as rotten and cracked fruits, and disease such as plague and leaf mold are likely to increase due to rainfall during harvest periods. Oda et al. (2008) reported the differences between stem direction and lateral shoot growth in tomato plants. In previous reports (Ahmad and Singh, 2005; Muhammad and Singh, 2007), the vegetative growth, fruit yield, and marketable fruit rate could be increased by staking some tomato cultivars. Also, Ohta and Makino (2019) were reported the influence of stem directions on the fruit yield, plant growth and physiological characteristics in processing tomato cultivation. As a results, in the vertical training plot compared with the horizontal training plot, the stem length and the length of the lateral shoots of the upper nodes were longer, the leaf area was larger, and the dry weight of the entire above-ground part including the leaves, stems in the upper lateral shoots, and roots was also increased. Therefore, it was considered that the promotion of vegatative growth in plant by vertical attraction had an effect on the increase of the initial yield, and the results of this experiment suggested the effectiveness of vertical attraction compared to the conventional cultivation method in processing tomatoes. Furtherfore, it was shown that the number of lateral shoots was not influenced the harvested fruit number and fruit yield in the previous report (Ohta