Sunburn mitigation in dragon fruit (Hylocereus spp.): Unravelling genotypespecific physiological and biochemical responses

Kanupriya Chaturvedi^1*Karunakaran G¹Arivalagan Manivannan¹Laxman R H¹Prakash Kumar²Manjunath, B. L¹Ruchitha, T¹Abhilash, K¹Tridip Kumar Hazarika¹

• ¹Indian Institute of Horticultural Research (ICAR), Bengaluru, India
• ²ICAR - Indian Agricultural Statistics Research Institute, New Delhi, India

Sunburn is one of major abiotic stress affecting dragon fruit (Hylocereus spp.), impairing tissue integrity, disrupting physiological functions, and significantly reducing yield. This study evaluated the efficacy of eleven treatments combining kaolin with shade net, seaweed extract, and various biostimulants to mitigate sunburn stress in red (H. costaricensis 'CHESH-D1') and white (H. undatus 'CHESH-W1') genotypes. Treatments included T1 (water spray control), T2 (kaolin 5% + green monofilament shade net 30%), and T3-T11 involving kaolin (5%) + seaweed extract (0.5%) combined individually with silica (0.5%, T4), micronutrients (0.5%, T5), petroleum oil (0.5%, T6), salicylic acid (0.5%, T7), neem soap (0.5%, T8), microbial consortium (0.5%, T10), brassinosteroids (0.5%, T11), and both neem soap (0.5%) + microbial consortium (0.5%, T9). Among these, T8 and T9 were the most effective in reducing canopy temperature by 4.2-5.1 °C and malondialdehyde (MDA) content by 32-38% over the control. However, these treatments were associated with lower phenolic, flavonoid, and antioxidant enzyme (SOD, POD, CAT) activities compared to the control, suggesting reduced oxidative stress. T2 helped retain maximum chlorophyll content (1.82 mg g⁻¹ FW) due to the UV-shielding effect of the shade net. Additionally, microbial augmentation in T9 improved nutrient uptake. The red pulp genotype exhibited superior sunburn tolerance, with 12% lower MDA levels and 18% higher SOD activity compared to the white genotype. These findings demonstrate that kaolin-based treatments combined with neem soap and microbial amendments (T8 and T9) synergistically alleviate sunburn stress by improving antioxidant enzyme activity and nutrient homeostasis. The observed genotype-specific responses offer valuable insights for precision sunburn mitigation strategies in dragon fruit cultivation under high-radiation conditions.