2008 年 77 巻 1 号 p. 1_59-1_66
In the silkworm, non-susceptibility to B. mori densonucleosis virus type-1 (DNV-1) is controlled by a dominant gene, Nid-1. In this report, simple and effective methods for linkage analysis and for mapping were improved. Three strains were used: No. 908, a virus resistant strain carrying Nid-1, and RF02 and RF50, which were used as standard wild type strains in our previous linkage analyses and mapping. Linkage analysis of Nid-1 was carried out by using survivors of two kinds of backcrosses, (RF50×908) females crossed to RF02 males and (RF02 × 908) females crossed to an RF50 male, after oral inoculation with DNV-1. The ordered DNA patterns from two families of BF1 segregants was enough to determine linkage group by analysis of RFLP patterns of previous mapped cDNA clones, specific for each of the twenty-eight linkage groups (RFLGs). The results indicated that Nid-1 was linked to linkage group seventeen (RFLG17). Individual genomic DNA samples of 64 survivors from the backcross of RF02×(RF50×908) were used to locate five clones and Nid-1. The relative distances between them were determined by repeated three-point analysis and showed that Nid-1 was closely linked to two genes (m025 and m237), at a distance of 4.7cM from them.