Sunburn mitigation in dragon fruit (Hylocereus spp.): unravelling genotype-specific physiological and biochemical...

Sunburn is a major abiotic stress affecting dragon fruit (Hylocereus spp.), impairing tissue integrity, disrupting physiological functions, and significantly reducing yield. Developing effective mitigation strategies is critical for sustaining productivity under high radiation conditions.

This study evaluated the efficacy of eleven treatments combining kaolin (5%) with shade net, seaweed extract (0.5%), and various biostimulants 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).

Neem soap (T8) and neem soap + microbial consortium (T9) were the most effective treatments, reducing canopy temperature by 4.2-5.1 °C and malondialdehyde (MDA) content by 32-38% compared to the control. These treatments also showed lower phenolic, flavonoid, and antioxidant enzyme (SOD, POD, CAT) activities, indicating reduced oxidative stress. Shade net + kaolin (T2) retained the highest chlorophyll content (1.82 mg g^-1 FW), while microbial augmentation in T9 improved nutrient uptake. The red genotype exhibited higher tolerance to sunburn, with 12% lower MDA levels and 18% higher SOD activity than the white genotype.

Kaolin-based treatments, particularly when combined with neem soap and microbial amendments, synergistically alleviated sunburn stress by reducing oxidative damage, improving antioxidant enzyme activity, and enhancing nutrient homeostasis. Genotype-specific responses highlight the potential for precision management strategies to improve dragon fruit resilience under high radiation environments.