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

Abstract

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 produced cocoons that differed greatly in weight and shell weight were screened using 240 primer pairs of single nucleotide polymorphic 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 suggesting 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. 347* Corresponding author. MATERIAL AND METHODS Silkworm strains used and raising of F2 and BC progenyThe silkworm strains Pure Mysore (PM) and CSR2, which differ in cocoon traits, were used in the present study. The parents were reared under standard conditions and the F1 generation of PM × CSR2, F2 by selfing of F1 progeny, backcross progeny, viz., (PM × CSR2) × PM and (PM × CSR2) × CSR2, were produced and reared simultaneously. After cocooning the cocoons were cut open and sexes of the pupae determined by recording the markings on the individual pupae. Cocoon weight represents the total weight of the pupa along with the silken shell. The shell weight is the weight of the cocoon after removing the pupa. Generally, female pupae are heavier than those of males, as they contain 350 to 500 eggs and a geater amount of fat tissue. To determine the mean cocoon weight of parents and progeny, a sample of 100 cocoons consisting of 50 female and 50 male cocoons of the parents, F1, F2 and BC progeny were weighed. Further the shell weight was recorded using the same cocoon samples. The frequency distribution of the cocoon and shell weight of the F2 was analyzed. The cocoon weight and shell weight data were sorted in descending order and the top ten (high weight) and the bottom ten (low weight) in the samples of F2 and BC progeny were selected. DNA extractionHigh molecular weight genomic DNA was extracted from frozen moths of PM females, CSR2 males, and their F1 progeny (PM × CSR2). Frozen pupae were used for the extraction of DNAs from F2 and BC progenies. All DNA...

Frequency of hybridization between Ostrinia nubilalis E‐and Z‐pheromone races in regions of sympatry within the United States

“…SNP markers were previously developed from O. nubilalis expressed sequence tags (ESTs; Coates et al 2008Coates et al , 2011a, and subsequently applied to detect significant levels of genetic differentiation among O. nubilalis populations (Coates et al 2011a) and to determine linkage groups associated with Bacillus thuringiensis resistance traits (Coates et al 2011b). SNPs have been used in other species of Lepidoptera to identify population genetic structure (Margam et al 2011) and to detect genome regions that influence traits (Sreekumar et al 2011). Our data show that the segregation of three SNP markers within the O. nubilalis pgfar gene are significantly correlated with the proportion of E11-14:OAc produced in the female pheromone gland.…”

Implications of genetic diversity in the improvement of silkworm Bombyx mori L.

“…This has allowed, during the last decade, the identification and development of markers with such potential applications as the identification and characterization of genetic stocks (facilitating the study of diversity and the estimation of the degree of kinship that exists within the germplasm banks); molecular map construction; marker-assisted selection; the identification of quantitative trait loci (QTL); the positional cloning of visible mutations; and the construction of BAC libraries (Zhan et al, 2009;Sreekumar et al, 2011;Venkatesh and Chikkaswamy, 2017;Buhroo et al, 2018b). Buhroo et al (2016b) indicate that markers are necessary tools that can further accelerate silkworm improvement.…”

Analysis of transcripts of heat shock protein genes in silkworm, Bombyx mori (Lepidoptera: Bombycidae)

“…CSR2 is bivoltine and is widely reared in Southern India. It was bred from Japanese hybrids highly productive in favourable environ-mental conditions and as a consequence is not tolerant of high temperatures and humidity (Sreekumar et al, 2011). In the present study the tolerance of these three silkworm breeds was measured in terms of percentage pupation and expression of Hsp genes at high temperatures.…”