Growth performance and gene expression analyses reveal the viability of tree of heaven, Ailanthus altissima as diet for the eri silkworm, Samia ricini (Lepidoptera: Saturniidae)

The generalist feeding habit of the eri silkworm, Samia ricini (Donovan) (Lepidoptera: Saturniidae) enables it to utilize a wide range of host plants with diverse phytochemical compositions, has made understanding its dietary preferences and adaptations complex. In this study, we evaluated the phenotypic responses of the yellow plain strain of S. ricini reared on four diets: castor (Ricinus communis), cassava (Manihot esculenta), tree of heaven (Ailanthus altissima), and the artificial diet Silkmate L4M. Our results demonstrated that diet was the most influential factor shaping phenotypic traits, with additional influences from sex and season, highlighting the complex interplay of these factors in determining eri silkworm life-history characteristics. S. ricini performed best when reared solely on castor when compared with other diets, reinforcing its status as the primary diet. To circumvent suboptimal performance provided by A. altissima, we shifted larvae from castor to A. altissima at the fifth instar and observed minimal compromise in survivability, suggesting a commercially viable strategy and broader diet options for eri silkworm by utilizing this plant. Transcriptomic analysis of fifth instar larvae fed on castor showed significant enrichment in gene pathways associated with metabolic activity, whereas larvae fed on A. altissima or cassava exhibited reduced expression in pathways related to lipid and energy metabolism, correlating with their lower performance and survivability. Our results support the strategic integration of A. altissima to enhance sustainability and facilitate extended eri silkworm rearing seasons, particularly in temperate regions.