Silkworm genetics research: developing silkworm strains adapted to lowland Philippine conditions

Professorial Chair Lecture

Development Fund Professorial Chair Lecture

Place

Plant Pathology Auditorium, BioSci Bldg, UPLB, College, Laguna

Date

4-12-2002

Abstract

Sericulture started in the Philippines in 1593, but even today, it is still considered as a local fledging industry. Its sustainability depends largely on the quantity and quality of available strains for hybridization. The potential of mutation induction in generating diversity to the locally available gene pool is briefly presented. This lecture deals mainly with the efforts of UPLB Sericulture R & D from 1980 to 2001 in improving the genetic diversity of locally available strains by developing stable established ("pure") lines through inbreeding of local and foreign hybrids. Selective breeding at UPLB focuses on the improvement of economically important characters such as high % egg hatch, uniformity of hatching, synchronicity in larval development, high survival rates and cocoon yield, long silk filament, uniformity in denier, high % silk and reelability. The % egg hatch and hatching synchronicity were significantly influenced by the duration of cold storage of the eggs and the conditions prevailing during cold storage and egg incubation. A continuous increasing trend (1984-85) in % egg hatch was noted in LBS1, LBS2 and NB18. Culling late developers during the larval stage resulted in better synchronicity of hatching and larval development during the breeding work of the 1990s. Selection for specific larval and cocoon characters significantly improved the uniformity of current inbred lines that include LBS6, LBS7, CJ102, CN144, Guanong, Kinshu x Showa and Shoukou Ryuuhaku. Data on cocoon length (1984 to 1985) indicated that LBSI and LBS2 were fairly stable for this parameter, but NB 18 cocoons became 16% shorter after 5 generations of inbreeding. Cocoon live weight for 7 UPLB strains also declined after 5 generations of sibmating, but with the implementation of closed line mating in the breeding protocol, these strains have recovered. Initial analysis of LBS cocoons showed a low degree of correlation (r = 0.10 to 0.59) between cocoon length and width, live weight, pupal weight and shell weight. Analysis of the relationship between cocoon live weight and shell ratio showed a higher degree of correlation in males than in females for the 4 strains reared September-November 2001. Filaments with mean lengths over 1,000 meters have been obtained from LBS6, LBS7 and Kinshu x Showa. Denier data (June 1999 to September 2001), an indicator of the fineness of silk, ranged from 1.88 to 3.03 g/m and was the least variable among the filature characteristics. Percentage silk values of LBS7 (June 1999 to September 2001) ranged from 30.09-51.77%, a considerable gain when compared to 1992 values. High percentage reelability values from 73.3 to 96.48% were obtained during this period. Mean fecundity of moths for 8 rearings (April 1999 to September 2001) fluctuated between 178.5 to 538.4 eggs/female. During the October-November 2000 rearing, the strains were inadvertently exposed to insecticide and this not only decimated the JAM strain and nearly wiped out LBS6, but the lowest values in cocoon live weight, total filament length and moth fecundity were also recorded for this particular rearing season. Hybrid compatibility studies and on-site testing of hybrids have been done in during the 1980s and 1990s, and the first simultaneous evaluation at UPLB and FIDA, Wangal, Benguet has just been concluded this March 2002. PTRI and SRDI, DMMMSU have been breeding silkworms since the 1970s and 1980s, respectively and currently have their own collection of "pure" and hybrid lines. Problems and prospects for sericulture R & D are discussed herein.

Location

UPLB Main Library Special Collections Section (USCS)

College

College of Arts and Sciences (CAS)

Language

English

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