ABSTRACT
G46B is a promising holding line used for three-lines breeding strategy in hybrid rice, but it is susceptible to blast disease caused by Pyricularia grisea. To improve its blast resistance, three rice varieties, Digu, BL-1, and Pi-4, with blast resistance genes, Pi-d(t), Pi-b, and Pi-ta2, respectively, were used to be crossed with G46B, and 15 plants with these three blast resistance genes, Pi-d(t)1, Pi-b, and Pi-ta2, were selected from their F2 and B1C1 populations via a marker-aided crossing procedure. Among them, four plants were heterozygotes in the three resistance genes, with the genotype of Pi-d(t)1 pi-d(t)/Pi-b pi-b/ Pi-ta2 pi-ta2; ten plants were heterozygotes in two of the three resistance genes, of which six with the genotype of Pi-d(t)1 Pi-d(t)1/Pi-b pi-b/Pi-ta2 pi-ta2, three with the genotype of Pi-d(t)1 pi-d(t)1/Pi-b pi-b/Pi-ta2 Pi-ta2, and one with the genotype of Pi-d(t)1pi-d(t)1/Pi-b Pi-b/Pi-ta2 pi-ta2; and only one plant was homozygote in two of the three resistance genes with the genotype of Pi-d(t)1 Pi-d(t)/Pi-b pi-b/Pi-ta2 Pi-ta2. These results demonstrate the capacity of maker-assisted selection (MAS) in gene pyramiding for rice blast resistance and its enhancement for the efficiency in rice resistance breeding.
Subject(s)
Crosses, Genetic , Genes, Plant , Genetic Markers , Genotype , Oryza , Genetics , Plant Diseases , Genetics , Selection, GeneticABSTRACT
2600 Anthers from T0 modified cry1 Ac-transgenic rice lines of Minghui 81, an elite restoring line of commercial CMS indica hybrid rice, were cultured on SK3 media. 83 green plantlets were recovered, 43 double haploid (DH) and 40 haploid among them. Results of PCR analyzes indicated that 55 plants of 83 were harbored the cry1Ac gene, and the ratio of cry1Ac-positive against cry1Ac-negative was 2:1 (55/28). 36 putative transgenic DH plants were further confirmed by Southern blot. ELISA detection showed that Cry1Ac level in different transgenic rice plants of the same cry1Ac-DH clone was almost equal and the highest one amount to 0.25% of the total soluble protein. Pest insect-resistant bioassay at field trials demonstrated that some of the homozygous cry1Ac-transgenic rice plants not only showed high-level resistance against striped stem borer (Chilo suppressalis) but also retained elite agronomy characters. These results demonstrated that rice anther culture has a great value in rice molecular breeding.