Impact assessment of physical and cultural interventions on frost injury and stress-responsive biochemical traits in mulberry saplings under temperate conditions

Abstract

Frost is a major abiotic constraint limiting the survival and early establishment of mulberry (Morus spp.) in temperate sericulture regions such as Jammu and Kashmir. Juvenile saplings, particularly those recently transplanted to nursery beds, suffer severe freezing injury that delays growth recovery and reduces foliar biomass. The present investigation evaluated the effectiveness of frost-mitigating cultural and physical interventions by assessing frost injury, growth traits, and stress-responsive biochemical and antioxidant parameters in two mulberry varieties, Goshoerami (V₁) and Kokuso-21 (V₂), during 2022-23 and 2023-24. Five treatments were studied: control (T₀), smoke application (T₁), tender shoot protection with insulating polythene (T₂), sapling covering with plastic bottle (T₃), and split fertilizer application (T₄). Significant variation was observed among treatments for all traits. Polythene insulation (T₂) consistently resulted in the lowest frost damage (9.23% in V₁; 6.11% in V₂) and the highest bud sprouting (88.27% and 90.89%), leaf area, shoot length (118.25 cm and 100.94 cm), and biomass attributes, primarily due to reduced radiative heat loss. In contrast, split fertilizer application (T₄) produced the most superior root traits and the maximum accumulation of soluble proteins, sugars, phenols, proline, chlorophyll pigments, and antioxidant activity including FRAP, SOD, PPO, and catalase, indicating nutrient-supported tissue maturity and stronger activation of stress-responsive pathways under natural frost exposure. Overall, physical insulation through T₂ proved most effective in minimizing frost injury and promoting early spring growth, whereas T₄ maximized physiological and biochemical resilience.