Influence of Plant Height on Morpho-physiological and Biochemical Parameters of Som (Persea bombycina Kost.): Implications for Muga Silkworm Rearing & Cocoon Traits

Abstract

Muga, the golden silk, is the world’s costliest natural fiber, produced by the sericigenous insect Antheraea assamensis Helfer (Saturniidae: Lepidoptera). Among the host plants, Som (Persea bombycina Kost.) and Soalu (Litsea polyantha Roxb.) serve as primary food sources, while Dighloti (Litsea salicifolia), Mejankari (Litsea cubeba), and others act as secondary and tertiary hosts. Due to its superior nutritional profile, Som is the most preferred host, significantly influencing larval growth, grainage efficiency, and cocoon quality in Muga silkworms. Although seasonal variability in Muga crop performance is well-documented, limited research has been conducted on the impact of plantation structure; particularly plant height, on host plant quality and subsequent silkworm productivity. The present investigation aimed to evaluate the influence of five distinct height categories of Som plantations: Short Plant (T1, 6–10 ft), Medium Tree (T2, 20–25 ft), High Tree (T3, 25–30 ft), Wild/Un-pruned Tree (T4, >30 ft), and the recommended Control (Small Tree, 10-15ft) on morpho-physiological, biochemical, and economic traits. Results revealed that T2 (Medium Tree) showed significantly superior outcomes across most parameters. T2 showed significantly higher values for studied morpho-physiological parameters, where leaf area was recorded as 52.4 cm2, fresh leaf weight 580g, dry leaf weight 158g, moisture percentage 72.76%, moisture retention capacity 70.2% and stomatal frequency as 242 per mm2. Female and male larval weights in T2 were highest at 16.21 g and 14.01 g, respectively, compared to the lowest values in T4 (7.24 g and 5.12 g). Fecundity peaked at 168 eggs/khorika in T2 and declined to 69 eggs/khorika in T4. Biochemical parameters in T2 leaves were also optimal, with crude protein at 20.5%, total lipid 5.3%, crude fiber 13.8%, and total ash 6.1%. Cocoon quality traits followed a similar trend: cocoon weight (3.42 g), shell weight (0.48 g), shell ratio (14.03%), and effective rate of rearing (ERR%) (74.6%) were highest in T2, highlighting its superiority over taller, unpruned plantation types. The study conclusively demonstrates that maintaining Som plantations at a height of 20–25 feet (T2, medium height) significantly enhance leaf biochemical composition, supports better larval growth, and leads to improved cocoon yield and grainage performance in Antheraea assamensis. These findings underscore the importance of plantation architecture in host plant management and provide a practical, cost-effective recommendation for maximizing productivity in sustainable Muga sericulture. Integrating this strategy with existing practices could revolutionize silkworm host plant cultivation and ensure higher economic returns for rearers in the Muga-producing regions of India.