Creation and identification of diploid and tetraploid interspecific hybrids between Oryza sativa and Oryza barthii

Abstract

Wild rice species are invaluable resources for genetic improvement of cultivated rice. “Breeding super rice using double advantages of wide cross and polyploidization” is a novel pathway in rice breeding. To exploit the favorable genes of wild rice fully, a technical system composed of hormone treatment, repeated pollination, hybrid embryo rescue, and chromosome doubling was established for efficient creation of distant hybrids and allopolyploids. Using the technical system, the diploid and tetraploid interspecific hybrids between Oryza sativa L. and Oryza barthii A. Chev. were successfully established. Morphological traits such as lemma tip color, stigma color and exsertion, awn color and length of interspecific hybrids exhibited the characters of their wild rice parents. Some traits such as plant type and grain length were intermediate their parents. Overall, the fertility of hybrids was very low. The results of simple sequence repeat molecular marker detection indicated that the interspecific hybrids possessed the bands of both parents. After chromosome doubling, the grain size, and the seed-set rates of the tetraploid interspecific hybrids increased significantly, but the tiller number per plant, panicle length, and the total grain number per panicle decreased significantly. The results showed the efficiency and importance of the technical system in establishment of distant hybrids and allopolyploids. The study provides novel germplasm resources for rice breeding and theoretical research.