Role of Foliar Applications by some Safety Compounds and Shading in Alleviating the Harmful Impacts of High Temperature on Tomato

Abstract

In Egypt, a large number of tomato varieties are grown but most of them lost their potential mainly because of the biotic and abiotic factors. Among these factors, heat stress that is one of the most important determinants of the continuity of the production in the late summer period. The aim of the current study was to assay the role of some treatments in lessening the harmful impacts of high temperatures on production of two commercial hyrids Alisa F1 and 888 hybrid. The study was elaborated in the open field at El-Baramoun farm, Mansoura Horticulture Research Station, Dakahlia governorate during two successive late summer seasons of 2014 and 2015. The experimental design was in split plot included six treatments i.e., naphthaline acetic acid (NAA) at 2.5 ppm, Purshade (CaCO3) 1%, Kaoline (Aluminum silicate) 2.5% as foliar spray and intercropping with maize through two levels of shading; shade 2 (intercropping with maize at two meters apart at the same side of ridge planted with tomato; shade 3 (intercropping at three meters apart at the same side of ridge planted with tomato). Significant differences were observed between Alissa F1 and 888 hybrid tomato hybrids for the majority of studied traits. In general, the mean performance of 888 hybrid grown under high temperature was better and more tolerant than Alissa F1. In regard to effect of the treatments, both treatments of shade 2 and NAA gave the highest plant height without significant differences between them. Furthermore, NAA at 2.5 ppm gave the great number of branches per plant over the two seasons. In addition, expressive increase in the leaf area was recorded for all treatments in the second season comparing with the first one, however, the shade 3 treatment gave the highest leaf area over the two seasons estimated by 730.87 cm and 772.8 cm, respectively. The treatment of NAA caused a high and significant increase in the total chlorophyll content over the control during the two seasons estimated by 1.15 and 1.72 mg/g, respectively followed by Kaoline treatment. In contrast, a great accumulation of dry weight was observed with the shade 3 treatment that gave 30.03 % and 30.22%, for the first and second season, respectively followed by NAA treatment. Kaoline caused a significant increase in TSS % compared with the control. High vitamin C content was recorded by the NAA treatment with significant differences comparing with the control. Concerning fruit firmness, shade 3 has a significant effect on firmness over the two seasons that estimated by 30.55 and 30.98 inch/cm2, for the first and second season, respectively followed by Kaoline and CaCO3 treatments. In addition, the foliar application by NAA increased significantly fruit set % that estimated by 13.10 % and 8.83 % for 888 hybrid and Alissa F1, respectively over the control. Concerning the total fruit yield, the shade 3 treatment recorded an increase estimated by 10.45 and 10.68 ton/fed over the control for 888 hybrid and Alissa F1, respectively as a mean performance of the two years followed by NAA treatment. According to the previous results, it can recommended under high temperature spraying tomato plants by NAA at 2.5 ppm combined with intercropping with maize at three meters apart at the same side of ridge planted with tomato which enhanced different vegetative growth parameters as well as the quantity and quality of fruit yield.