Comparative Effects of Glycine max and Glycine soja Leaves on Clanis bilineata tsingtauica Rearing Performance

In China, the enormous gap between domestic soybean supply and increasing consumption necessitates large-scale soybean imports. The use of cultivated soybean (Glycine max) leaves as feed for the edible insect Clanis bilineata tsingtauica further reduces crop yields, posing a threat to national soybean production security. To address this issue, this study evaluated wild soybean (Glycine soja) as a potential alternative feed source. Comparative analyses examined the nutritional and anti-nutritional properties of G. max (cv. Qihuang34) and laboratory-preserved G. soja germplasm, together with their effects on larval growth performance, nutritional composition, and associated microbiota. G. soja leaves exhibited significantly higher crude fat (5.61% vs. 2.17%), ash (11.07% vs. 9.62%), neutral detergent fiber (23.75% vs. 21.00%), calcium (4.05 g/kg vs. 3.41 g/kg), and phosphorus (2.52 g/kg vs. 2.38 g/kg) than G. max, alongside lower trypsin inhibitor levels (P< 0.01) despite higher phytic acid content (P< 0.05). Fifth-instar larvae reared on G. soja leaves achieved a 12.9% increase in body weight (6.846 g vs. 6.066 g), higher crude protein (672.14 g/kg vs. 555.02 g/kg), total soluble sugar (21.27 mg/g vs. 8.96 mg/g), and soluble protein (26.35 mg/g vs. 24.71 mg/g), but lower crude fat (187.44 g/kg vs. 205.82 g/kg, P< 0.05). 16S rRNA sequencing revealed distinct phyllosphere microbial communities, with G. soja enriched in diverse taxa (e.g., Bacteroidota, Proteobacteria) and G. max dominated by Firmicutes. Corresponding differences were observed in larval gut microbiota, with positive correlation analyses suggesting potential microbe transfer from G. soja leaves to larval guts. Overall, G. soja represents a promising alternative feed for C. bilineata, reducing competition with soybean grain production and supporting sustainable insect farming.