World Association of Young Scientists

ERI SEED TECHNOLOGY

Dr.M.C.Sarmah

INTRODUCTION

Seed is the key for successful crop. Like wise, in sericulture industry also quality silkworm seeds play a significant role to ensure a good crop harvest. Eri silkworm, Samia ricini (Donovan) is multivoltine in nature and 5 - 6 brood can be reared through out the year. Eri silkworm is polyphagous in nature, although the castor, Ricinus communis Linn is the best food plant for seed production. At farmers level, aspect of quality control is often ignored. Under traditional practice, the rearers use to collect seed cocoons very often from different sources without knowing the history of the previous crop and/or sometimes from their own crop. Further, the most of the rearers do not adopt any scientific method of seed production in their grainage and never resort to microscopic examination of the mother moth to eliminate diseased layings. Hence, quality of the layings thus produced, are not ensured. But, success of sericulture depends on proper multiplication of basic silkworm seeds. To produce quality eri silkworm seed, it is very important to follow scientific methods of seed production.

ARRANGEMENT OF REQUISITES

The first and foremost activity of eri seed production is to acquire necessary materials for grainage operation.
An ideal grainage hall is essential for successful grainage operation.
 The site of grainage hall should be cool, dry and well ventilated.
 A grainage room having a working area of 34ft length x 18ft breadth x 12ft height is suitable for processing 5000 seed cocoon in each operation.
 All round verandah of 5ft to 6ft breadth is also required to maintain the cool temperature of grainage house.
 The ground surface should be plastered with concrete for easy cleaning and draining of water.
 There should be separate site for seed coon preservation, oviposition and moth examination.
 The grainage house should be fly proof by providing additional netted windows and doors.

Different equipments & accessories are required for grainage operation like 1) Foot sprayer, 2) Centrifuge, 3) Compound microscope, 4) Slide & cover slip, 5) Moth crushing set, 6) Masks & gloves, 7) Eye protecting glass, 8) Egg box, 9) Cocoon cage, 10) Kharika, 11) Cocoon cage stand, 12) Bloating & tissue paper, 13) Measuring cylinder, 14) Balance (minimum weighing cap. 0.1 g), 15) Scissor, 16) Chair, stool & moth examination table, 17) Non-absorbent cotton, 18) Bucket, 19) Thread, 20) Foot wear, 21) Apron.
Besides, certain chemicals are also required for grainage operation like, Bleaching powder, Lime powder, Potassium carbonate, potassium hydroxide.

DISINFECTION
First and foremost step of grainage operation is disinfection of grainage house and appliances. The steps of disinfections are as follows.
 Drench the walls and other bigger appliances with 5% bleaching powder solution.
 Dip smaller appliances in 5% bleaching powder solution.
 Spray 5% bleaching powder solution and 0.5% slaked lime mixture and leave the hall closed for 24 hours.
 Seal the grainage hall 3 days prior to operation.
 Use disinfection mask, apron and hand gloves while disinfecting.
 Complete the process of disinfection at least 3 days before consigning seed cocoon.

SEASON OF SEED PRODUCTION

Considering the performance of different grainage characters such as good moth emergence, higher coupling realization, higher fecundity, low emergence of cripple moth and higher hatching of egg the Autumn season was found as significantly best season for eri seed production and Summer season was comparatively unsuitable season for eri silkworm seed. Remaining seasons are also suitable for eri silkworm seed production.

SELECTION OF SEED COCOONS:

After harvesting of cocoon, proper selection of seed cocoon is must for a successful grainage operation.

 Select only full formed and compact cocoons.
 In case of female seed cocoons, minimum 0.35- 0.4 g shell weight and minimum 2.8- 3.0 g cocoon weight is preferable.
 Male and female seed cocoon ratio should be around 3:2 for optimum coupling recovery.

TRANSPORTATION OF SEED COCOONS:

During transportation of seed cocoons proper care is to be taken.

 Transport the seed cocoons preferably in bamboo basket after complete pupation.
 Avoid exposure to direct sunlight, heat, rain, jerks etc. that may damage the seed cocoons.

STORAGE OF SEED COCOONS:

Proper storage of seed cocoons also depends for a successful grainage.

 Store seed cocoons in single layer in the cocoon cage to facilitate easy moth emergence.
 Maintain semi dark condition in the seed cocoon preservation room by providing black curtain in the windows and doors.
 Maintain proper aeration in the grainage house.
 Maintain grainage room temperature between 26-28oC and relative humidity (RH) around 75-80%

MOTH EMERGENCE & COUPLING:
It is necessary to manage proper coupling of male and female moth for a successful grainage.

 Eri moth is generally emerged cool hours of the day, but intensity is more in evening hours.
 Moth coupled during the night.
 Optimum period of coupling is 5-6 hours.
 Pick the coupled moth one by one and tie the one hind wing of the female moth with kharika using a short cotton thread.
 Hang the kharika 6-8 inch apart in a cool & semi dark place.
 Decouple in the morning hours with soft handling without rupturing of the reproduction organ.
 Keep the female moth in kharika for oviposition

OVIPOSITION :

 Eri moth generally laid egg up to 5-6 days.

 Consider the eggs laid on the first three days for commercial rearing. In case of seed rearing only first 2 days lay egg is suitable.

MOTH EXAMINATION:

This is very important step to produce disease free layings.

 Conduct examination of indidual mother moth for detection of pebrine
 Crush the moth with 0.8-1.0% potassium carbonate at 1:6 ratio in moth crushing set, filter with cotton and centrifuge at 5000 rpm for 5 minutes.
 The sediment should be dissolved in 2% potassium hydroxide (KOH) by stirring with a glass rod.
 Examine the sediment under microscope keeping on a slide with cover slip with 600x magnification using 15x eyepiece and 40x objective.
 Excessive smear should be removed by sucking with a bloating or tissue paper.
 Detected pebrinized slide should be kept in 5% bleaching solution for over night
 Pebrinized and other diseased moth along with eggs and kharika should be burn immediately.

SURFACE STERILIZATION AND DRYING OF EGGS:

 Dip the dfls in 0.1% sodium hydroxide solution for 0.5 minutes and then wash thoroughly in running water by gently rubbing with hand to eliminate gummy substances.
 Dry the eggs preferably in shade by spreading on a bloating paper.

EGG PACKING AND TRANSPORTATION:

 Pack individual dfl in egg boxes made up of porous hard paper bag.
 For buck quantity make boxes of appropriate sizes at least for 50 Dfls with muslin cloth with wooden frame.
 Label each egg box mentioning grainage name, weight, race and probable date of hatching
 During transportation of eggs exposure to direct sunlight, heat, rain etc. should be avoided.

MAINTENECE OF HYGIENE AT GRAINAGE ROOM:

 Dispose off the crushed moth, melted cocoons, papers etc. in soak pit after treating with 5% bleaching powder solution away from the grainage hall or burn them.
 Dispose off the pierced cocoons as soon as possible.
 Wash hands with alkaline soap and then 2% bleaching powder solution before entering the grainage hall.
 Avoid using shoes inside grainage room.
 Keep a foot mate soak with 2% bleaching powder solution in front of the grainage hall.
 Burn the dead and melted cocoons immediately.