Detection of a single nucleotide polymorphism (SNP) DNA marker linked to cocoon traits in the mulberry silkworm, Bombyx mori (Lepidoptera: Bombycidae)

Sivaramakurup Sreekumar,Syed M.H Qadri,Sundaramurthy N Kumar,Monika Slathia,Southekal K Ashwath

doi:10.14411/eje.2011.043

Abstract

Cocoon weight and shell weight are the key economic traits ultimately determining silk yield. In order to detect the main quantitative trait loci (QTL) associated with the cocoon traits of the mulberry silkworm, Bombyx mori, the parents of larvae that pro- duced cocoons that differed greatly in weight and shell weight were screened using 240 primer pairs of single nucleotide polymor- phic markers (SNPs) representing all the 28 linkage groups in silkworm. Out of the 240 primer pairs, 48 (20%) revealed distinct polymorphism between the parents, which was confirmed by the co-dominant expression of both polymorphic PCR products in the F1 generation. The bulked segregant analysis (BSA) was used to compare the SNP profiles of the parents, F1 and F2 bulks using the 48 informative SNP primers. This revealed that out of 48 primer pairs, only one pair, i.e., No. 04124 of the linkage group 4 showed clear differences in the amplified products between the bulks corresponding to that of the parents with different cocoon traits sug- gesting that the DNA regions amplified by this primer pair are closely linked to the QTL controlling the cocoon traits. The results were also confirmed by screening the backcross (BC) progeny. This is the first report of the identification of a QTL using SNPs with BSA. The results of the present study indicate that it might be possible to use SNPs for marker assisted selection (MAS) in silkworm breeding programs aimed at improving cocoon traits.

Highlights

Though India is today the second largest producer of silk in the world, the twin problems of low productivity and poor fibre quality continue to impair an increase in production
The resultant line is known as near isogenic lines (NILs), which is nearly isogenic with the recurrent parent (RP) as most of its genome is derived from RP along with a small portion of the genome of donor parent (DP) flanking the target gene
Bulked segregant analysis using single nucleotide polymorphic markers (SNPs) primers revealed large differences in the cocoon traits of the parents, their F1 and bulked samples of F2 and BC progeny, which clearly indicate linkage of the DNA segments amplified by SNP primer pair No 04124 to linkage group

Summary

Introduction

Though India is today the second largest producer of silk in the world, the twin problems of low productivity and poor fibre quality continue to impair an increase in production. To overcome these drawbacks, new breeding strategies adopted in the early ’90s have resulted in the production of a number of productive silkworm strains. New breeding strategies adopted in the early ’90s have resulted in the production of a number of productive silkworm strains These strains are popular only with those farmers who can provide adequate inputs and managerial skills. The available bivoltine strains that produce quality silk are not hardy

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