Evaluation of physiological performance and fruit quality of citrus trees under colored shade nets and open field conditions: A comparative study

Abstract

Shade nets are frequently used to protect fruit-bearing trees from unfavorable weather conditions. However, the impact of colored shade nets on plant growth and fruit quality of horticultural crops remains poorly understood. This experiment was designed to investigate the effect of colored shade nets on photosystem II efficiency (Fv/Fm), vegetative growth, and fruit quality of tangerine cultivar known as Murcott (Citrus reticulata, 'Murcott'). The experimental design consisted of a randomized complete block with six replications and five different shade net treatments: red 60 %, red 40 %, green 60 %, green 40 %, and an open field as the control. The nets were placed on steel rectangular structures, which had a height of 4.5 m, for a period of three months during the summer season. The results indicated that all shade net treatments led to an increase in relative humidity and a decrease in temperature, as compared to the control group. The green 60 % had the highest Fv/Fm value, even though it had low rates of photosynthetic active radiation (PAR) and light intensity (LUX). On the other hand, the open field had the lowest rate, despite having a high rate of PAR and LUX. Trees under green 60 % had the highest leaf chlorophyll content, while those under red 40 % had the lowest. The open field and green 60 % had the highest shoot growth rate, whereas the lowest rates were observed in trees under red 60 % and green 40 %. There was no significant impact of any of the shade net treatments on leaf area and total yield compared to the control. Compared to the open field, all shade net treatments resulted in a decrease in sunburn incidence. The highest levels of total soluble solids (TSS) were observed under green shade nets and the control group, whereas the lowest levels were detected under the red nets. Furthermore, it was observed that the green 60 % resulted in a significant increase in several parameters including titratable acidity (TA), antioxidant capacity, total phenols, total carotenoids, and color index (Lab∗). Given these positive attributes, the green 60 % option is considered to be a viable choice for covering citrus trees.

Keywords

• Colored shade net
• Photosystem II
• Fruit quality
• Citrus