DIFFERENTIATING BETWEEN PARTHENOGENETIC AND POSITIVE DEVELOPMENT EMBRYOS IN TURKEYS BY MOLECULAR SEXING

In mated or inseminated turkeys, 5 to 15% of eggs set for incubation s how only rudimentary development. Most of these embryos die during the first 24 to 48 h of incubation and contain only unorganized sheets of tissue. This abnormal development is termed ''positive development'' (PD). Turkey eggs also show incidence of parthenogenesis and the resul ting progeny is believed to be always male. As both types of embryos a re morphologically similar at the early stage of incubation, it has be en speculated that PD embryos may in fact be parthenogens. By identify ing the sex at the blastodermal stage with the help of DNA markers, we have differentiated between the PD embryos and parthenogens. Partheno genetic embryos were obtained from eggs laid by uninseminated or virgi n Beltsville Small White (BSW) hens, and the PD embryos were obtained from eggs of inseminated Nicholas and British United Turkeys of Americ a (BUTA) hens. DNA was extracted from blastoderms of parthenogenetic a nd PD embryos. Turkey W-chromosome specific DNA probe and primers were used to detect females in all samples by Southern blot and polymerase chain reaction (PCR), respectively. No female was detected among the 35 parthenogens examined, whereas there were 3 females among the 11 PD embryos. The presence of both males and females among PD embryos sugg ests that they are products of fertilization, and that at least these 3 female embryos, if not all the 11 PD embryos, are not of parthenogen etic origin. It is concluded, therefore, that PD embryos result from e rrors in fertilization or from early embryonic mortality following suc cessful fertilization, and that they are unlikely to be of parthenogen etic origin.