The Effect of Light Quality on Some Quantitative and Qualitative Characteristics of Fruits of Grape (Vitis vinifera L. ‘Yaghooti’), under salinity conditions in greenhouse

Document Type : Full Paper

Authors

• Maryam Keshavarzi ¹
• Mahmood Esna-Ashari ²
• Hassan Sarikhani ³

¹ Department of Horticultural Sciences, Faculty of Agricultural, Bu-Ali Sina University, Hamedan, Iran

² Department of Horticultural Sciences, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran

³ Department of Horticultural Science, Faculty of Agricultural, Bu-Ali Sina University, Hamedan, Iran

Abstract

Keywords

• Anthocyanin
• LED
• antioxidant capacity
• red and blue lights
• electrical conductivity

Main Subjects

• Fruit Science

Extended Abstract

Introduction

    Grapes are one of the most important economic crops in Iran and the world, which are cultivated in a wide range of climatic conditions. The most cultivated areas of grapes in Iran are located in arid and semi-arid regions, and salinity is one of the main factors that limit the production of grapevine in these regions. To overcome the negative effect of salinity, artificial lighting in greenhouse can be considered as a useful tool to remove light limitations and improve fruit antioxidant activities. Therefore, this research investigated the effect of LED lights with the wavelengths of 448 nm (blue light) and 623 nm (red light) as well as their combination on fruit production and the amount of some biochemical compounds in the greenhouse under the hydroponic system and the salinity of the nutrient solution.

Materials and methods

In this research, one-year saplings of grape (Vitis vinifera L. cv. Yaghooti) were used. After disinfection and washing, saplings were transferred into 7-liter pots containing peat and perlite (1:1) and grown in hydroponic conditions by feeding modified Hoagland nutrient solution. The research was carried out as a factorial experiment with two factors. based on a completely randomized design, with three repetitions and conducted over two successive years. The first factor was the different qualities of light at 5 levels and the second factor was the electrical conductivity caused by adding NaCl with a purity of 99.45% to the nutrient solution at 4 levels. Salt and light treatments were applied to the plants at the same time and every other day. After finishing the treatments in the first year, the then were moved again to the greenhouse at the beginning of January. When the plants stablished and reached to the proper growth. about 50 cm in height, they were subjected to different treatments of salt stress and light for another 3 months (February to April) and under the same conditions as the first year. In the second year, when the saplings were three years old, they produced fruits.

Parameters including fruit cluster weight (by digital scale), cluster density (cluster weight to volume ratio), soluble solids (using Atago handheld refractometer, model N1, Japan), total fruit acidity (by titration method according to Ayala-Zavala, 2007), fruit sugar to acid ratio, fruit antioxidant capacity (by DPPH method (Li et al., 2005), fruit total phenol concentration (using Folin-cicalto method (Tezcan et al., 2009), fruit total flavonoid content (Li et al., 2006), fruit total fruit tannin (Taira et al., 1996), fruit peel anthocyanin (Giusti et al., 2001) and vitamin C (using dichlorophenol-endophenol titration method (Hashemi-Dehkordi protocol , 2012) were measured on three-year-old plants.

Results and Discussion

The results of this study showed that in combination of red and blue light (70-30) treatment compared to other light qualities, the weight, length, width and cluster density of fruits were 53, 71.89, 70 and 36% respectively, more than the natural light of the greenhouse at 10.23 Ms/cm of salinity treatment. The combination of red and blue lights increased the amount of dry matter (18.31%), dissolved solids (18.31%), titratable acid (12.51%), antioxidant capacity (20%) and vitamin C (39.49%). compared to the natural light of the greenhouse. It also caused the lowest accumulation of tannin in the fruit (29.55%) in the treatment of 10.23 Ms/cm of salinity. Blue light (100%) led to an increase in the sugar to acid ratio and anthocyanin ratio by 18.31 and 37.41%, respectively, more than natural greenhouse light in grape fruit. It seems that the red and blue lights and their combination increased the life span of the plant by maintaining the greenness and its freshness, and with a positive effect on the amount of photosynthesis and the most useful production metabolites, it led to greater tolerance of the plant in different salinity levels. The result maintained the fruit quality at a favorable level.

Therefore, the combination of red and blue lights, especially the ratio of 70-30%, showed a greater effect in maintaining and improving the quantitative and qualitative characteristics of the fruit in severe salinity treatment.

Conclusion

_{The results of this research showed the positive effect of different qualities of light on fruit quantitative and qualitative characteristics of Yaghooti grapes when irrigated by saline nutrient solution using hydroponic system under greenhouse condition. The combination of red and blue lights, especially with a ratio of 70-30% stimulated the production of useful secondary compounds in fruit compared to the single lights, and were more effective in improving the quality of the fruit.}