Linkage and mapping analysis of a non‐susceptibility gene to densovirus (nsd‐2) in the silkworm, Bombyx mori

Abstract

Nonsusceptibility to Bombyx mori densovirus type 2 (BmDNV-2) is controlled by a recessive non-susceptibility gene, nsd-2 (non-susceptibility to DNV-2) in B. mori. Taking advantage of a lack of crossing over in females, reciprocal backcrossed F1 (BF1) progeny were used for linkage analysis and mapping of nsd-2 using silkworm strains C124 and 902, which are classified as being highly susceptible and non-susceptible to DNV-2, respectively. BF1 larvae were inoculated twice with DNV-2 virus at the first and second instar stages. DNA was extracted from each of the surviving fifth instar larvae and analysed by RFLP inheritance patterns using probes specific to each of the 28 linkage groups of B. mori. Our results indicated that the non-susceptibility gene was linked to linkage group 17, since all surviving larvae showed the homozygous profile of strain 902 in their genotype. The other linkage groups showed mixtures of heterozygous and homozygous genotypes, indicating an independent assortment. A linkage map of 30.6 cM was constructed for linkage group 17 with nsd-2 mapped at 24.5 cM and three closely linked cDNA markers were identified.

Genetic mapping of a food preference gene in the silkworm, Bombyx mori, using restriction fragment length polymorphisms (RFLPs)

“…In our results, the food preference gene was found to exist on the chromosomal region between clone e73 and ep16, and the closer clone e73 was mapped at the distance of 4.2 cM. This distance is estimated as 2 Mbp at the sequence level because 1 cM corresponds to approximately 500 kbp in B. mori (Promboon et al, 1995;Abe et al, 2000;Ogoyi et al, 2003). This is an important step to obtain the most closely linked marker for cloning the food preference gene.…”

“…With respect to clone m112, which has been assigned to linkage group 28 using strains RF02 and RF50 (KadonoOkuda et al, 2002), Ogoyi et al (2003) reported that this clone was sorted into linkage group 27. In this study, clone m112 gave the same pattern as linkage group 27.…”

“…Linkage analysis and mapping Linkage analysis and mapping of the food preference gene were performed using previously described methods (Hara et al, 2001Kadono-Okuda et al, 2002;Ogoyi et al, 2003). In subsequent linkage analysis, cDNA clones on the chromosome where the food preference gene is located were determined based on the RFLP segregation pattern in 14 larvae grown until the second instars using artificial diet without mulberry leaf powder.…”

“…Based on this biphasic nature of genetic recombination, a non-susceptibility gene to densovirus (nsd-2) was effectively mapped on the 17th chromosome in B. mori by linkage analysis and repeated three point test of cDNA-RFLP markers (Ogoyi et al, 2003).…”

Marker-assisted selection in breeding silkworm strains with high silk production and resistance to the densonucleosis virus

“…Abe et al (1998Abe et al ( , 2000 identified and mapped several random-amplified polymorphic DNA (RAPD) markers linked to the nsd-1 and nsd-2 genes. Ogoyi et al (2003) mapped nsd-2 using the restriction fragment length polymorphism method, and obtained 3 closely linked cDNA markers. Based on a map-based cloning analysis, Li et al (2001a) identified an RAPD marker linked to nsd-Z.…”