Effects of different melatonin doses on the development of some grape varieties grown under high temperature stress

Grapevines are among the oldest plants domesticated and most widely cultivated around the world. Grapes, with their rich nutritional especially vitamins, minerals and phenolic substances, have been used for their berries, seeds, peel, leaves and various derivatives. Grapes having a wide consumption option, as it is processed in the food industry into wine, grape juice, molasses, vinegar, and many other local products, both in its fresh and dried form. The plant of this valuable fruit is the vine and has been cultivated in Anatolia for approximately 6000 years. There are nearly 1500 varieties/genotypes in the "National Collection Vineyard" which is primarily responsible for the protection of Turkey's vine genetic resources. With its deep-rooted history and rich genetic diversity, Anatolia has been considered in the literature as the homeland of the grapevine. However, under the influence of increasing environmental stress factors, it is important to reduce various stress factors that negatively affect plant development and to carry out studies to minimize the effects of these negative conditions on the plant in order to sustainably feed the world population. In this context, melatonin is an important molecule that plays a vital role in combating various abiotic and biotic stresses in plants. Melatonin applications in different plant species have yielded positive results in protecting plants against various stress factors. In grape production, melatonin applications are seen to be quite limited. Within the scope of this study which is planned to be carried out in the Glass Greenhouse in the Department of Horticulture and Breeding of the Faculty of Agriculture of Selçuk University, the physiological and vegetative development responses of four table grape cultivars varieties ('Müşküle', 'Mevlana', 'Hamburg Misketi' and 'Razakı') grafted onto Rupestris du Lot to foliar melatonin applications under high temperature stress will be investigated. In the study, grapevines grown in solid volume soilless culture medium containing equal amounts of pumice and peat will be used. Melatonin will be applied to the leaves at concentrations of 0.1, 1.0 and 10 mM three times at four-week intervals from the beginning of high temperature conditions (around 40 °C) in the glasshouse environment. Following the applications, stomatal conductance, leaf temperature and leaf chlorophyll content values will be recorded. At the end of the growth period, the developmental characteristics of the plants will be examined. According to the general findings, suggestions will be developed about melatonin applications for the sustainability of our national viticulture under the influence of climate change and other multiple stress factors. Leaf melatonin treatments led to significant improvements to many parameters depending on both doses and genotypes. Among the tested doses, 0.1 mM melatonin was outstanding for many parameters. Considering the general investigations, leaf melatonin applications could be recommended to supports grapevines against the insufficiencies in vegetative development commonly seen in ecosystems like Konya and its resembling areas.