With its rich tradition of silk saris, India is the world’s largest consumer of raw silk. Most of the silk it uses, India also produces. But some is imported. Import of cheaper raw silk poses a threat to indigenous sericulture.

In 2011-12, for instance, about 20% of the total consumption of over 28000 tonnes was imported, mainly from China, the world’s largest producer of raw silk.

Sericulture, the rearing of silkworms for silk production, is a labor-intensive agro-based industry which provides additional income to marginal farmers in India, especially women.

In the recently presented Union Budget, customs duty for import of raw silk was raised from five per cent to fifteen per cent. This move will help improve prices for producers of raw silk in the domestic market.

The Indian government also plans to encourage farmers to take up sericulture on larger scales, by providing incentives to support rearing houses, modern rearing and irrigation equipment.

“Silk production in India needs an improvement in quantity as well as quality as compared to other silk-producing countries,” emphasized Dr. Asoke Banerji, Distinguished Professor, Amrita School of Biotechnology.

Dr. Banerji’s research on bioactive lead compounds led to the isolation of plant extracts namely ecdysterone, juvenile hormone analog (JHA) and moulting hormone (MH). These compounds known to impact insect growth could have very positive implications for sericulture in India.

The isolation of JHA and MH was completed in the phytochemistry laboratory of the Amrita School of Biotechnology. The isolated compounds resulted from bioprospection among the Western Ghats flora, in Wayanad District, Kerala. Sri Sreejit Mahadevan, Associate Professor at S N M College, Ernakulam currently posted at the Amrita School of Biotechnology under UGC’s faculty improvement program is assisting with the work.

“Sreejit was instrumental in identifying Sri Sashi, a progressive farmer, who was ready to undertake the risk for our trials. A six-month pilot study was conducted during July 2012 – December 2012, at two sericulture farms in Kuthannur Panchayath and Kannadi Panchayath, both in Palakkad District, Kerala,” explained Dr. Banerji.

“Now many other farmers are showing interest to try out our preparations. The aim is to develop and transfer technology for efficiently utilizing the two compounds for the benefit of poor sericulture farmers of Kerala,” he added.

“Bivoltine refers to those species that have two broods in one year. Bivoltine double hybrids (FC1 & FC2) were brought in the second instar stage from Chawki Rearing Centre of the Central Silk Board and grown in field conditions. Temperature was maintained at around 23 C and humidity was adjusted to about 75 % relative humidity. Mulberry leaves of Victory 1 genotype from a periodically watered garden were fed liberally three times a day,” Dr. Banerji explained.

Elaborating further, he added, “Mounting of larvae is a cumbersome process and requires a lot of care and labour. If the cocooning is not synchronized, the larvae which are late in cocooning may damage the already cocooned shells by urinating on them, changing the colour to brown.”

“In our experiments we found that MH at 10 ppm hastened cocooning. 90% of larvae matured and started spinning within 18 hours from time of spraying.

A 15-25 % increase of individual cocoon weight was obtained with a 2-3 ppm JHA concentration,” he specified.

“JHA can be used in sericulture for yield improvement. In the geographical regime and the bivoltine variety studied, a 1-3 ppm concentration can bring about a considerable increase in economic returns. MH is highly active in hastening larval maturation and reducing the mounting time. Both compounds are recommended for the sericulture farmer’s benefit, since plants are readily available and the preparation of the spray costs almost nothing,” Dr Banerji concluded.

April 11, 2013
School of Biotechnology, Amritapuri