Fitness of Hybrids between Two Types of Transgenic Rice and Six Japonica and Indica Weed Rice Accessions

Abstract

Studies of hybrid fitness can help in evaluating the potential introgression of a transgene from transgenic rice (Oryza sativa L.) to weedy rice. The objective of this study was to assess the composite fitness of intra‐ (within the same subspecies either indica or japonica) and inter‐ (between individuals of different subspecies) hybrids between two transgenic glufosinate‐resistant rice lines and six weedy rice accessions in the field. Compared with their weedy rice counterparts, intrahybrids may be similar or greater, and the interhybrids may be lower, similar, or greater in fitness. Using japonica transgenic rice Y0003 as male progenitor, composite fitness of intrahybrids increased over generations, while that of interhybrids kept variable over generations. Using indica transgenic rice 86B as paternal plants, the composite fitness of all intrahybrids decreased, but that of interhybrids increased over generation. Regardless of japonica or indica transgenic rice being paternal plant, pollen viability, and seed set were greater in intrahybrids but lower in interhybrids than their weedy rice counterparts. Moreover, inter‐F2 and inter‐F3 hybrids segregated for plant height, heading period, and seed set. Therefore, potential risk of gene flow from transgenic rice to weedy rice was dependent on the genotype of both weedy rice and transgenic rice. Gene flow from transgenic rice to weedy rice of the same or different subspecies should be prevented either through mitigation or stewardship owing to the similar or greater fitness of intraspecific hybrids compared with parental weedy rice and the similar or increased composite fitness of majority interhybrids over generations.