Breeding and Resistance Analysis of Near Iso-transgenic Lines with a Single Copy of the Transgene Xa21 in Rice
水稻单拷贝Xa21近等转基因系的培育与抗性分析

Plant transgene expression is affected by the integration sites in host genome to some degree, which is generally termed as "transgene position effects". The bacterial blight resistance gene Xa21 was previously transferred into a rice variety, Minghui63, through Agrobacterium-mediated transformation, and transformants with different transgene copy numbers were obtained. Through self-pollination of transgenic plants, identification and selection of transgene integration sites for several generations, homozygous transgenic lines with only one copy of the transgene Xa21 located at different chromosome positions were obtained on the Minghui63 genetic background. These transgenic lines were almost identical on their genome except for their different transgene locus and could be regarded as near iso-transgenic (NIT) lines. Six NIT lines were obtained and verified through Southern hybridization and genetic mapping of the transgene. These NIT lines displayed almost the same resistance level to bacterial blight, indicating that the integration sites did not affect the resistance expression of Xa21, and there were no position effects for the transgene.