The present study was conducted to screen the suitable castor (Ricinus communis) cultivar for use in commercial chawki (young age silkworms) rearing of eri silkworm (Samia ricini D.). Five commercially available cultivars of castor viz., NBR-1, Kalpi-6, DCH-519, ICH-66 and DCS-9 were sown in the field and standard package of practices were followed to select the economically viable cultivar in terms of plant growth and yield parameters. The results revealed varying degrees of growth and yield parameters in all five cultivars in terms of plant height, number of leaves per plant and leaf yield at different days after sowing. Among all the cultivars, higher growth and yield parameters was recorded in two cultivars (NBR-1 and Kalpi-6). Further, these two cultivars (NBR-1 and Kalpi-6) were selected for analysis of biochemical constituents. Higher moisture retention capacity (82.65%), protein content (20.60%), carbohydrate content (17.12%) and other leaf quality parameters which are essential for eri young age silkworms (chawki) were recorded in NBR-1. Among the two castor cultivars fed to eri-silkworm, NBR-1 fed worms recorded higher larval weight and more uniformity compared to Kalpi-6 fed worms. The results indicate suitability of NBR-1 cultivar in terms of growth, yield, biochemical constituents and eri young age silkworm rearing. Therefore, NBR-1 is recommended for commercial eri chawki rearing in view of the higher leaf yield obtained at different intervals in a year and superior in improving the rearing performance of eri chawki. Based on these findings a standard package of practice to raise NBR-1 cultivar for chawki rearing has been developed.

Availability of quality seeds in muga culture for commercial rearing during May-June and Oct-Nov seasons is the biggest challenge, which severely affects the total muga silk production. Both the commercial seasons are preceded by seed and pre-seed seasons with highly unfavourable weather conditions, which affects the availability of quality Disease Free Layings (DFLs) due to low cocoon yield, reduced fecundity, poor hatching and male sterility. Therefore, there is an urgent need to develop an integrated approach to improve the availability of quality DFLs during commercial seasons. Towards this end different strategies are being developed and tested. Breeding for selecting muga lines with high fecundity has been taken up. To avoid unfavourable weather conditions during seed crops especially during summer months June-September, efforts are being made to identify the cooler regions in Northeastern states and to take up seed rearing in the selected regions. Wild muga that exhibit winter hibernation are being studied to identify the linked gene and to introgress it into cultivated population to completely avoid rearing during winter season. Adual-purpose cold reeling procedure has been developed, which has also been tested field level, to reel the silk and obtain live pupae for use in grainage. Through biotechnological approaches the realized fecundity has been increased. Improved mountages that provide enough space, aeration and reduced temperature are being tested for increasing the number of good cocoons and also reducing the male sterility due to high temperature. Other approaches such as rearing of seed cocoons in non-traditional areas having muga host plants such an Uttarakhand state, cold preservation of both DFLs and cocoons, new plantations in cooler regions, effective utilization of grainages developed under different government schemes through state governments, etc., are being explored to effectively increase the quality DFL production for use during commercial seasons in muga ecosystem. These approaches are of great promise and help in achieving 'Sustainability Development Goals 2020' of Central Silk Board.