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United States Department of Agriculture

Agricultural Research Service

Title: DNA Polymorphisms of the Pi-Ta Alleles in the Rice Blast Resistant and Susceptible Cultivars

Authors
item JIA, YULIN
item Bryan, Gregory - AG RES, NEW ZEALAND
item Farrall, Leonard - DUPONT
item Valent, Barbara - KANSAS STATE UNIV

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 5, 2002
Publication Date: N/A

Interpretive Summary: Rice is one of the most important crop plants in the world, and the rice blast disease caused by fungus, Magnaporthe grisea, is one of the most destructive diseases. Incorporation of resistance genes into existing rice varieties is a common practice for the control of the disease. Therefore, it is essential for rice breeders to know whether breeding materials contain a particular blast resistance gene. The rice blast resistance gen Pi-ta protects rice crops against the fungal pathogen M. grisea expressing the corresponding avirulence gene AVR-Pita in a gene-for-gene manner. Pi- ta originally introgressed into japonica rice cultivars from indica was isolated by positional cloning. The genomic organization of the susceptible pi-ta gene in a japonica susceptible cultivar, Tsuyuake, was investigated in this study. A genomic library of Tsuyuake was constructed and an overlapping contig spanning the pi-ta gene was generated. The nucleotide sequences of the pi-ta gene were determined using an ABI sequencer. The DNA sequence of susceptible pi-ta allele is 99.6% identical to the dominant resistance Pi-ta allele. An unusually low nucleotide level of polymorphisms was identified in the region of the Pi-ta gene. The greatest sequence diversity was discovered in the intron region. The pi-ta allele was transcribed and has an interrupted open reading frame that encodes a protein that is 99.3 % identical to Pi-ta. The resistant dominant Pi-ta gene was identified in the rice cultivars Katy and Drew by direct sequencing of products of polymerase chain reaction. Oligonucleotides designed based on these DNA polymorphisms should be dominant markers to identify rice cultivars that contain the Pi-ta gene. The resulting knowledge is the basis for breeding for broad-spectrum blast resistance.

Technical Abstract: The rice blast resistance gene Pi-ta protects rice crops against the fungal pathogen Magnaporthe grisea expressing the corresponding avirulence gene AVR-Pita in a gene-for-gene manner. Pi-ta originally introgressed into japonica rice cultivars from indica origin was isolated by positional cloning. The genomic organization of the susceptible pi-ta gene in a japonica susceptible cultivar, Tsuyuake, was investigated in this study. DNA fragment near the amino terminus of Pi-ta hybridized to a smear of background, and DNA fragment encoding 3' terminus hybridized to a single band in DNA blot analysis. A genomic library of Tsuyuake was constructed and an overlapping contig spanning the pi-ta gene was generated. The nucleotide sequences (5125 bp) of the pi-ta gene were determined using an ABI sequencer. The DNA sequence of susceptible pi-ta allele is 99.6% identical to the dominant resistance Pi-ta allele. An unusually low nucleotide level of polymorphisms was identified in the region of the Pi-t gene. The greatest sequence diversity was discovered in the intron region (0.7%). The pi-ta allele was transcribed and has an interrupted open reading frame that encodes a protein that is 99.3 % identical to Pi-ta. The resistant dominant Pi-ta gene was identified in the rice cultivars Katy and Drew by direct sequencing of products of polymerase chain reaction. Oligonucleotides designed based on these DNA polymorphisms should be dominant markers to identify rice cultivars that contain the Pi-ta gene. The resulting knowledge is the basis for breeding for broad-spectrum blast resistance.

Last Modified: 8/19/2014
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