Muga silkworms feed on a graded range of host trees. Cocoon colour follows the leaf — som and soalu give the golden cocoon the silk is named for, while Mejankari (Litsea cubeba) gives glossy white cocoons and the finest, highest-priced silk of all, now confined to pockets of Jorhat and Sivasagar.
Host plant tiers
| Tier | Species |
|---|---|
| Primary | Som (Persea bombycina); Soalu (Litsea monopetala) |
| Secondary | Dighloti (Litsea salicifolia); Mejankari (Litsea cubeba) |
| Tertiary | Kathalua (Litsea nitida); Champa (Michelia champaca); Ganasaroi (Cinnamomum glanduliferum); Patihanda (C. obtusifolium) |
Som genotypes
Som has 51 catalogued genotypes (PB001–PB051) classified largely on leaf shape, of which four are tetraploids (PB009–PB012).
| Selection | Genotype |
|---|---|
| Best polyploid | Gadadhar (PB012) |
| Best diploids | Naharpatia (PB003) and Kothalpatia (PB006) |
| Least susceptible to leaf spot | S3 |
Germplasm conservation
The Conservation Centre at Chenijan holds 14 morphotypes and 182 plus-trees of som, 10 morphotypes each of soalu and dighloti, 4 of mejankari, plus 14 S3 × S8 som hybrids and 4 dighloti × soalu hybrids. Leaf yield across the eight isolated som morphotypes ranges from 2.55 to 3.60 kg per plant per harvest.