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Studies on the Heterosis for Silk Productivity in Three-way Crosses of Multivoltine Silkworm, Bombyx Mori L. in Bangladesh.

M. Tajimul Haque
Senior Research Officer
BSRTI, Rajshahi.

K.T. Haque
Senior Reseach Officer
BSRTI, Rajshahi.

M.S. Islam
Research Officer
BSRTI, Rajshahi.

Abstract/ Executive Summary:

Hybrids of silkworm are superior to their parents in respect of silk production. Now a days introduction of hybrids instead of pure started a new direction in the sericulture industry since the discovery of Fl for economic traits in silkworm (Datta and Pershad 1988). Largest silk producing country like India, where the advantages of using three-way crosses of the silkworm hybrids had been demonstrated by some silkworm breeders to increase silk production (Krishnaswami 1987, Subba Rao et al. 1989 and Das et al. 1994). Moreover, silk productivity is an important breeding index in evaluating silkworm breeds (lyengar et al. 1983). Very recently it was reported that three-way crosses would be more useful for production of commercial cocoon in the unfavourable rearing season of West Bengal instead of a single cross (Chattapadhyay et al. 1995). The climatic condition of Bangladesh is very much similar to the condition of West Bengal, so, there is a wide scope to introduce the same technique in our country as well.

Keywords: Heterosis, Silk productivity, Three way crosses, Bombyx mori L.

Location: Bangladesh Sericulture Research and Training Institute

Start Date:

End Date:

Program Area: Socio-economic and Policy

Commodity: Silkworm

Objectives:

To determine the extent of heterotic expression with respect to silk productivity in three way crosses on multivoltine silkworm.

Methodology:

Four existing popular combinations suitable for unfavourable rearing season namely, N (M) x 83/2, 83/2 x N (M), N(M) x 85/3, 85/3 x N(M) and HTHRB-5 were selected for this investigation. The females of HTHRB-5 were crossed with all the males of the popular combinations and eggs for 4 three-way crosses viz., HTHRB-5 x N(M) x 83/2), HTHRB-5 x (83/2 x N(M), HTHRB-5 x N(M) x 85/3 HTHRB-5 x 85/3 x N(M) were prepared and reared during the favourable Agrahyoni (October-November) and unfavourable Bhaduri (August-September) rearing seasons of Bangladesh. Three replications with 400 larvae per tray (3'x2'x3") were taken for each of the crosses. Silkworm rearing technique was followed as suggested by Krishnaswami (1978) and silk productivity was calculated following the formula (Udupu and Gowda 1988). Mean values of shell weight, 5th Instar larval duration and productivity of four three -way crosses and their parents in two seasons have been recorded. A wide range of variation performance in all the three-way crosses was evident for the character of silk productivity in both the crops (Agrahyoni: 2.12-2.25 eg/day: Bhaduri: 1.67-2.08 eg/day). Among the crosses silk productivity was found to be maximum in HTHRB-5x(N(M)x85/3) (2.25 eg/day) followed by its reciprocal (2.20) in Agrahyoni crop whereas it was (2.08) eg/day) in HTHRB-5x(N(M)x83/2) followed by HTHRB-5x(85/3xN(M) (2.00 eg/day) in Bhaduri crop. The mean values in respect of silk productivity in the favourable season (Agrahyoni) revealed that the parents indicated in values of hybrids, this may be due to favourable seasons for all types of mulberry silkworm rearing reported by Sengupta et al. (1974), Das et al. (1994) and Chattopadyay et al. (1995).

Source of Information: Bulletin of Sericulture Research. 1998 Vol.9 :73-75 published by Bangladesh Sericulture Research and Training Institute.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Perceptible heterotic effect was observed in any crosses in the favourable seasons. However, positive significant heterotic effect was found in the cross HTHRB-5 x (N(M) x 83/2) over the MPV (44.94) as well as BPV (32.40) in unfavourable rearing season. Evaluation of the 4 three-way crosses of the present investigation clearly indicated that only HTHRB-5 x (N(M) x 83/2) hybrid was found to be the best cross for silk productivity in the unfavourable rearing season (Bhaduri) of Bangladesh.

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