Submitted to: Animal Biotechnology International Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 11, 1997
Publication Date: N/A
Technical Abstract: Marek's disease (MD) is an important lymphoproliferative disease of poultry and the causative agent is the MD herpesvirus (MDV). The recent development of a genetic map of the chicken enabled us to identify quantitative trait loci (QTL) affecting susceptibility to MD. The inbred lines 63 (MD resistant) and 72 (MD susceptible) were mated to create 300+ F2 chickens. The F2 chickens were challenged with JM strain MDV at one week of age, and monitored for symptoms of MD up to ten weeks of age prior to the evaluation of gross MD tumors. A multistage approach was used for QTL mapping. In stage 1, 65 DNA markers selected from the East Lansing genetic map were typed on 40 of the most MD susceptible and 40 of the most MD resistant F2 chickens, and 21 markers (P less than or equal to 0.20) residing near suggestive QTL affecting MD susceptibility were revealed by ANOVA. In stage 2, the suggestive markers plus flanking markers were typed don 272 F2 chickens, and four suggestive QTL (P less than or equal to 0.0016) were identified by ANOVA. In stage 3, using a suite of interval mapping programs (MAPMAKER/QTL, Map Manager QT, and QTL Cartographer), eight genomic regions with closely linked or pleiotropic QTL affecting several components of MD susceptibility were identified. In stage 4, using multivariate approaches of QTL analysis, three to six loci collectively explained between 12 and 23 percent of the total phenotypic MD variation. The majority of the QTL were recessive with respect to the line 72 allele. This study sheds light on the multigenic basis of MD susceptibility in the chicken, and indicates that MD is controlled by the interaction of non- additive genetic factors.