No abstract

SUMMARYTwo White Plymouth Rock lines (WPR), both developed into lines resistant for Marek's disease (MD), and one commercial WPR line, supposedly susceptible to the disease, were mated in a number of combinations to evaluate resistance to MD in their pure-and crossbred progeny. For this purpose the pedigreed 1-day-old progeny chicks were exposed to 3-week-old spreader chicks which had been inoculated at 1-day-old with virulent MD virus (MDV) and reared with them for the whole experimental period of 15 weeks.Response to the challenge showed that resistance to MD in the crossbreds was intermediate to that of resistant and susceptible parental Unes. It appeared that, besides a sex effect in the male progeny, the trait for MD resistance was most effectively transferred to the crossbred progeny by the resistant male parents.