For sustainable and regular use of germplasm, the foremost requirement is the information about the germplasm. Therefore, characterisation, documentation and information management are very essential aspects of germplasm management.
During the course of germplasm collection, characterisation and evaluation, considerable information on the germplasm are generated. Germplasm maintenance and conservation are useful only when they are utilised effectively on a continuous basis. However, for wider and regular use of germplasm, information/database are essential. Therefore effective utilization of germplasm resources mainly depends on the information documented so that the breeders and other researchers can objectively select the desirable genotype required for specific breeding and other research programmes. The CSGRC, Hosur has developed an information package for silkworm germplasm data maintenance and retrieval, Silkworm Germplasm Information System (SGIS). The information package facilitates data maintenance, analysis, data listing and easy retrieval with facility to multiple query. The germplasm information system maintains passport data, collection data, characterisation data, evaluation data and conservation information. (Fig.9)
The germplasm information management system developed at the Hosur centre is flexible and facilitates easy data entry, data evaluation during input stage and multiple analysis and therefore the information management system is user friendly. The SGIS was developed using integrated data base technique incorporating user friendly menu driven facilities for easy data view, information retrieval, updation and report generation. Each file of the integrated data base is linked to the accession number of the germplasm which is an unique number assigned to each silkworm germplasm accession serving as the primary key. The systems are flexible enough to allow modifications and insertions of new modules as per the changing needs. Also, the facility for identification of the accession(s), on the basis of certain desirable criteria up to 10 quantitative and/or qualitative characters has also been developed as separate module. This information system promotes utilization of germplasm in large scale. Utilising the SGIS, the first volume of catalogue on silkworm germplasm was compiled and published for circulation among the breeders and other research workers.
3.1.1 Descriptor/stock characterisation
To promote utilization of silkworm genetic resources, the following activities are undertaken at the germplasm resources centre.
1) Characterisation of silkworm germplasm and data base generation.
2) Evaluation of silkworm germplasm for biotic and abiotic stresses in the specific hot-spots
3) Evaluation of silkworm germplasm for yield potentials at multi-locations.
Silkworm races from different geographical regions exhibit considerable variations for several important heritable characters viz., egg and cocoon colour, shape and size, voltinism, larval markings, moulting behaviour, amylase activity in the digestive juice, carotenoid and flavonoid content in the silk fibre etc., Similarly, there are distinct molecular differentiation at the genome level in different silkworm accessions. Therefore, a proper and exhaustive characterisation will help to identify the distinctness of different silkworm accessions through phenotypic, biochemical and molecular markers; which will help selection of parents for silkworm breeding. Through characterisation, the specific identity of each accession is maintained, which helps to distinguish the accessions. Characterisation is mainly based on the heritable quantitative and qualitative characters, viz. morphological, anatomical, cytological, embryological, physiological, biochemical and biomolecular aspects. Characterisation also facilitates registration of germplasm and thereby establishes the Intellectual Property Rights (IPR).
In the case of silkworm germplasm characterisation a set of descriptors containing 'collection data' (Annexe-2), 'passport data' (Annexe-3), 'Specimen data' (Annexe-4), 'characterisation descriptor' (Annexe-5 & 6), and 'evaluation descriptor' (Annexe-7 & 8) are utilised for generation of information on the silkworm germplasm. The collection data elicit information on origin, location, geographical details of the accession. The passport data contain information on source and history of the accession. The specimen data contain bio-data of the accession, including parentage, voltinism, larval, cocoon and silk characteristics. These informations are obtained at the time of collection along with the accession. At the time of introduction of the accession into the base collection, accession(s) are studied meticulously for 27 characters (descriptor - characterisation) of egg, larva, cocoon, pupae and adult. The methodology for collection of data (descriptor - states) for descriptor characterisation is given in Annexe-6. The informations generated through these formats are precise and exhaustive and help to identify the specific accession(s).
Molecular characterisation of silkworm germplasm
Systematic genetic analysis of quantitative and resistance traits in silkworm has not been done, although the correlated changes in different quantitative traits are well understood Quantitative Trait Loci (QTL) mapping has become very powerful tool in plant and animal improvement programme and silkworms offer as a very interesting insect for such exercise. (Nagaraju 1997 & 1999).
There is no comprehensive method available for genetic characterisation of the silkworm gene pool at the molecular level. However, the well known molecular markers viz., Restriction Fragment Length Polymorphic (RFLP) markers, Minisatellite DNA markers, Microsatellite DNA markers, Random Amplification of Polymorphic DNA (RAPD) markers, Inter Simple Sequence Repeat (ISSR) markers and Amplified Fragment Length Polymorphic (AFLP) markers provide valuable information to identify duplicate accessions apart from trait based mapping and molecular tags. Molecular characterisation helps to identify the genetic distinctness of a race/breed/stock and thereby helps to eliminate duplicates and reduce the cost of germplasm maintenance and volume of work. Thus, the genetic markers facilitate molecular characterisation, maintenance, conservation and cost effective management of plant and animal genetic resources (Bruford and Wayne, 1993).
Molecular markers that are linked to metric and resistance traits and their subsequent mapping in silkworm is essential. Also these genetic markers can be applied periodically to monitor changes in heterogeneity and heterozygosity in the accessions, as they are routinely reproduced for maintenance. These molecular markers provide essential information for the development of "Core Collections". Molecular markers also facilitate genome specific and accurate information on genetic variability that may escape during characterisation of a race based on morphological, anatomical and biochemical parameters. Such molecular characterisation promote molecular marker assisted selection which will eliminate narrow genetic bases, inbreeding, common pedigree etc.
Molecular characterisation of 56 multivoltine and 80 bivoltine silkworm accessions were carried out; using SSR-Anchored PCR method involving amplification of the regions between pairs of microsatellites and anchored repeat primers to generate multiple polymorphic bonds. Inter-microsatellite DNA polymorphism was also studied by using two anchored primers. The primer [(GCT) (AGT) (GCT) (CA) TC] amplified a high number of polymorphic bonds. The polymorphism is quite evident among the accessions tested. PCR amplification of [(GT) 8 (A/G) TCC] primer also amplified large number of bonds, which shows less polymorphism among the accessions screened. The anchored primer identified a high cocoon weight marker of approximately 182-183 bp size mostly in high yielding silkworm accessions. Different statistical analysis were carried out to make use of the DNA profiles generated by the two primers. The discriminant function analysis to test the validity of the zone identification with regard to polymorphic DNA profiles indicated five discrete groups. The hierarchical clustering analysis based on yield parameters indicate that some of the accessions are very unique. The results indicate that the silkworm accessions available in the Indian germplasm collection are from different zones and these biotechnological tools can be used for analysing the actual genetic differences/genetic distance among the accessions based on the genetic characters which are more reliable, rather than the phenotypic characters alone.
3.1.2. Descriptor/stock evaluation
Evaluation of germplasm promotes effective and greater utilization of the germplasm, particularly in breeding and crop improvement. At the time of introduction of the accession into the base collection 38 characters of evaluation parameters are studied. The evaluation descriptors are mainly for commercial characters viz., cocoon yield and raw silk quality. The descriptor states for evaluation is given in Annexe-8.
Evaluation of silkworm germplasm under stress condition
Evaluation of germplasm under abiotic and biotic stress conditions is very essential to identify promising germplasm for further utilization in specific crop improvement programmes. The promising germplasm are further tested under multilocational trial to assess the genetic potential and genotype × environment interaction and genotype stability. The silkworm accessions undergo preliminary evaluation at CSGRC, Hosur for identification of the genetic potential of the accession and the data are utilised for classifying them as high yielding / tolerant to high temperature / disease tolerant / short larval accession etc., based on their performance in the preliminary evaluation trial. In the preliminary evaluation the accessions are subjected to uniform treatment and their response are evaluated from the performance. The preliminary evaluation trial is conducted for 3 crops to study the potential and stability of the characters. The silkworm breeds are also subjected for evaluation under different seasons. The silkworm races are evaluated for 13 rearing parameters and 16 silk characters (Annex-8). From the preliminary evaluation data, the silkworms are classified and grouped based on Warts' minimum variance method to identify the genetic relationship between the clusters and this method helps in grouping the silkworm germplasm. Such study will help the breeders to select the silkworm germplasm required for specific breeding studies.
After screening the silkworm germplasm through preliminary evaluation, the potent / selected accessions are subjected to screening against various biotic and abiotic stresses to identify tolerant / resistant breeds under hot spots / sick beds. The biotic stress include various pathogens (protozoan, bacterial, viral and fungal). The results of such hot spots / sick beds evaluation indicate the most potential accessions / breeds which are tolerant / resistant to specific biotic stress. Similarly the selected silkworm germplasm after preliminary evaluation are subjected to abiotic stress, particularly the adverse climatic condition (high temperature and high humidity / high temperature and low humidity).
Preliminary evaluation facilitates identification of silkworm clusters for resistant to a specific biotic or abiotic stress and only the selected accessions are subjected to sick-bed/hot spot evaluation for further estimation of the genetic potentials of the selected breeds and the best performed breed is used directly in the breeding programme. Hot spot evaluation of silkworm to important biotic and abiotic stress is considered as most useful evaluation to identify the silkworm breed with useful genes conferring better adaptation to stress environment and resistance to disease and pests. The hot spot evaluation is conducted in different regions with collaboration of the networking centres.
The screening of silkworm germplasm for biotic and abiotic stresses in the in-situ conditions under hot spots/sick beds provides objective assessment and evaluation of the germplasm and the information generated helps the silkworm breeders to select the right parents for specific silkworm breeding programme.
All India Mulberry and Silkworm Germplasm Evaluation Programme (AIMSGEP)
The CSGRC at Hosur has identified some silkworm races as best performing by multiple scoring analysis and these accessions are either at par or even performing better than the popular silkworm breeds commercially exploited in the field. In order to select the best performing breeds, the identified silkworm breeds are tested in different biogeographic zones along with local and national checks (popular breeds). The first field trial of 10 silkworm races is under trial at different places. The consistently best performing silkworm races will be sent for race authorisation trial, before release to the field in the particular area where the race performs better. The race authorisation trial is a multi-location trial to identify region/season specific breed.
Cataloguing and inventory of silkworm germplasm
After characterisation and preliminary evaluation of silkworm germplasm, the data are subjected to statistical analysis and the information are published in the catalogue. In the first phase 56 multivoltine and 195 bivoltine accessions were studied and the data were published in Catalogue on silkworm, Vol.1, 1997 (Thangavelu et al. 1997). The second issue of catalogue on silkworm containing information on 07 multivoltine and 103 bivoltine accessions is under publication in Vol.II. The information published in the silkworm catalogue Vol.I is available on our website - www.silkgermplasm.com, and sample pages of catalogue are enclosed. (Annex-9) The germplasm centre has prepared an inventory of all the silkworm accessions available in the centre, and maintain them along with information on characterisation, evaluation, supply, exchange, and utilization in the Silkworm Germplasm Information System (SGIS).
The information sharing on silkworm germplasm at global level among the countries is very much limited, unlike in agriculture, horticulture, sericulture, animal husbandry and fisheries etc. Hence it is very essential for sharing the information on silkworm germplasm among the nations, which will promote silkworm breeding and sericulture development. In several countries sericulture is not sustainable and cost of production of silk is very high mainly because suitable silkworm breeds are not available and they are also unable to evolve silkworm breeds suitable to their own agro-climatic conditions. Therefore, it is essential to share the information on silkworm germplasm among the countries involved in sericulture.
3.3.1 Standardisation of formats
The terminology(ies), evaluation, estimation methods and the information formats used for descriptor characterisation and evaluation need standardisation to promote international exchange of silkworm germplasm, since different countries may be adopting their own methods / standards / terminology / formats etc.
Also a set of core characters may be identified for uniform characterisation in all the silk producing countries; based on which clustering and core collection of silkworm germplasm can be made; core collection will actually facilitate the silkworm breeders in decision making to identify the parents for breeding and also select tester and lines for hybridisation from among the elite accessions.
3.3.2 Publication in common language and circulation
Sericulture is practiced in different countries across Asia, Africa and Latin America and the languages spoken in these countries are quite different and therefore there is a communication barrier among the nations. This is an important bottleneck for sharing the information on sericulture germplasm and sericulture related activities. Therefore to facilitate sharing of information on sericultural germplasm, it is essential to publish important information on sericulture germplasm in common language for circulation among the nations.
3.3.3 Internet uploading, sharing and establishment of internet links
The internet is a "network of networks" and operates through the computer systems around the world using a common set of rules called 'Transmission Control Protocol' or 'Internet Protocol'. It is very useful for speedy exchange of information. Using the internet facility many organizations around the world have developed their own Website and display their products, information and promote their business. The internet facility helps scientific research also for exchange of information. On the same lines, internet facility may be used for the development of website containing data on sericultural germplasm to facilitate exchange of information and promote utilization of sericultural germplasm.
In order to promote the utilization of sericultural germplasm available at CSGRC, Hosur, a website "www.silkgermplasm.com" was launched by the Centre on 5-6-2002. The website is designed with static and dynamic pages, containing information about the centre, mandate, activities and germplasm details respectively. The dynamic page on silkworm germplasm contain information on 225 silkworm accessions with more than 70 descriptors/evaluation data. The website also facilitate the selection of accessions, based on input criteria. This website facilitate further uploading of data from CSGRC, Hosur, India (Annexe-10). Japan also has developed a website for sericultural germplasm, but the information is very limited. For promotion of sericultural germplasm utilization the countries like China, France, Italy, Uzbekistan, Ukraine and other countries may develop website and make the information on sericultural germplasm available to sericultural scientists across the world for sharing of information to promote utilization of sericultural germplasm.
3.3.4 Global exchange of silkworm germplasm and establishment of Working Group
Sericulture is practiced in 53 developing and under developed countries benefiting 150 million people mainly from rural area and economically weaker sections of the society. Therefore, sericulture development will improve the quality of life of economically poor people in under developed and developing countries, for which high yielding mulberry varieties and robust silkworm breeds, and breeds tolerant to adverse agro-climatic conditions are essential; which means the available mulberry and silkworm germplasm need to be exchanged among the countries for the benefit of mankind in the world.
FAO may promote silkworm breeding among the member countries involved in sericulture and facilitate need based exchange of sericultural germplasm among the member countries. The silkworm and mulberry germplasm available in Japan, South Korea, France, Italy, erstwhile United Socialist Soviet Russia (USSR) and other countries where sericulture has declined may be deposited in China/India for conservation and utilization among the FAO member countries, for which FAO may provide financial assistance and infrastructure facilities, similar to the International Agricultural Research Centres functioning under the auspices of Consultative Group on International Agricultural Research (CGIAR) and facilitate exchange of sericultural germplasm similar to International Board for Plant Genetic Resources (IBPGR), Rome.
To organise an international centre for conservation of sericultural germplasm and formulate the procedure, terms and conditions for the exchange of germplasm among the FAO member countries, the FAO may constitute a Working Group and prepare a proposal for sanction by FAO.
