Evaluation of the Effect of Native Cultivars as a Rootstock on the Tolerance to Drought Stress in ‘Crimson Sweet’ Watermelon

Document Type : Full Paper

Authors

• Jaber Panahandeh ¹
• Ali Parsafar ¹
• davoud Zarehaghi ²
• mohammadvali Habibi ³
• Asghar Mohammadi ³

¹ Department of Horticultural Sciences, , Faculty of Agriculture, Tabriz University, Tabriz, Iran

² Department of Soil Engineering Sciences, Faculty of Agriculture, Tabriz University, Tabriz, Iran

³ Department of Horticultural Sciences, , Faculty of Agriculture, Tabriz University, Tabriz, Iran.

Abstract

Keywords

• phenol
• proline
• vegetable grafting
• Antioxidant
• irrigation treatment

Main Subjects

• vegetable plant science

Extended Abstract

Introduction

One of the greatest challenges faced by the scientific community in the next few years is minimizing the yield losses caused by drought. Vegetable grafting using rootstocks has emerged as a rapid tool in tailoring plants to better adapt to suboptimal growing conditions. The aim of the present study was to evaluate the potential of some of these local stands of rainfed watermelon as a rootstock for commercial watermelon and compare them with the commercial base of Shintoza in terms of drought tolerance.

Materials and Methods

Experiments were carried out during two consecutive growing seasons in 2016 and 2017 in an experimental greenhouse at the University of Tabriz, located in Tabriz, in the northwest part of Iran (latitude: 38° 1' 22.23" N, longitude: 46° 25' 9.38" E). We conducted this study to evaluate the response of watermelon (Citrullus lanatus (Thunb.) Matsum. et Nakai ‘Crimson Sweet’) to grafting onto three Iranian rainfed and seedy watermelon landraces collected from Khaje, Sabzevar, and Ashtian, along with ‘Shintoza’ (Cucurbita maxima × Cucurbita moschata) seedlings as a rootstock for watermelon. Irrigation was applied in three different levels based on FC as 1-0.8; 0.6 -0.8; and 0.3-0.6 FC by furrow irrigation method. Stomatal density, chlorophyll index, phenolic compounds, leaf relative water content (LRWC), electrolyte leakage, and proline concentration were measured at the end of both growing seasons.

Results and Discussion

The results showed that the number of stomata in the Moderate drought and severe drought stress in watermelons transplanted on Shintoza and Sabzevar plants was significantly reduced compared to the first irrigation treatment. In this experiment, the chlorophyll index was affected by Moderate drought stress. The highest amount of electrolyte leakage in both stress showed a significant difference with the plants under normal irrigation. With increasing the drought stress levels, the amount of LRWC in different stands linearly decreasied, and its lowest amount was observed in the severe drought stress. The amount of proline generally increased in the leaves of the studied watermelons in response to drought stress. Results showed that the Moderate drought stress caused a significant increase in the total carbohydrate content of the leaf in the studied watermelons. Meanwhile, drought stress caused a decrease in the amount of leaf phenol. Irrigation treatment, base and their mutual effects had a significant effect on the total antioxidant capacity, as well as the activity of catalase and peroxidase enzymes. Drought stress reduces the density of stomata in the leaves, which in turn causes a decrease in photosynthesis and yield of the plants. Preservation of chlorophyll index in plants under drought stress is considered as a desirable trait. LRWC plays a strategic role in drought tolerance of plants by inducing osmotic regulation through the accumulation of osmoprotecants. In our study, the accumulation of proline in the plant was increased under severe drought stress, the high amount of proline in grafted plants may be one of the reasons for the drought tolerance of these plants compared to non-grafted plants. The role of phenolic substances, like antioxidant enzymes, is to stop the activity of enzymes involved in the production of free radicals, and the higher activity of phenol in pumpkin rootstalks may be due to its high ability to donate hydrogen and stabilize a larger amount of free radicals. Potassium is an essential cytoplasmic element, and due to its role in osmotic regulation and its competitive effect with sodium, it is often used as an important element to increase resistance to environmental stresses, including water stress and salinity, as well as pests and diseases. Phosphorus also is one of the important components of enzymes, proteins, ATP, RNA and DNA. ATP plays a role in energy transfer reactions, meanwhile both RNA and DNA are components of genetic information. Phosphorus also plays a crutial role in the synthesis of starch and transportation of carbohydrates.

Conclusion

The high levels of chlorophyll index, phenolic compounds, and LRWC of plants grafted onto Shintoza and Sabzevar rootstocks suggested that an Iranian rainfed and seedy watermelons, Sabzevar, can be regarded as a potential rootstock for watermelon under drought stress without any detrimental effects on the fruit quality.