ARS | Publication request: Identification and QTL mapping of blast resistance in wild Oryza species

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 16, 2010
Publication Date: August 12, 2010
Citation: Eizenga, G.C., Prasad, B., Jackson, A.K., Jia, M.H. 2010. Identification and QTL mapping of blast resistance in wild Oryza species. p. 95 In: Proc. 5th Int. Rice Blast Conf. 12-14 Aug. 2010. Little Rock, Arkansas USA.

Technical Abstract: Leaf blast disease of rice (Oryza sativa L.) caused by Magnaporthe oryzae B. Couch is one of the most devastating rice fungal diseases worldwide. Wild relatives of rice (Oryza spp.) may contain novel genes for biotic and abiotic stress resistance lost during domestication. A collection of 67 wild Oryza spp. accessions was evaluated for reaction to eight U.S. races of M. oryzae and four accessions showed resistance to all races. Subsequently, we developed an advanced backcross mapping population with one O. nivara accession, as the wild donor parent. Our objective was to identify the QTLs associated with blast in this mapping population and compare the location of these putative QTLs to known blast (Pi-) genes. Bengal (PI 561735) is a popular U.S. medium grain rice variety which is susceptible to blast races IB-1 and IB-49. Bengal was chosen as the recurrent parent and O. nivara (IRGC104705) from Maharashtra, India as the donor parent. The advanced backcross method was used to develop the mapping population because this method has proven to be effective for simultaneously identifying QTLs and improving germplasm, especially when the donor parent is not adapted. The resulting population, composed of 253 BC2F2 families, was evaluated for reaction to blast disease in the greenhouse using races IB-1 and IB-49. The BC2F1 founder lines were genotyped with 133 SSR markers distributed throughout the 12 rice chromosomes. Products of the PCR reactions were visualized on an ABI Prism 3730 and “allele calling” completed with GeneMapper 3.7. The linkage map was created using JoinMap 4.0 and QTLs identified using multiple interval mapping as performed by QGene 4.3.6. Graphical Genotype (GGT) was used to determine the percentage of the genome heterozygous for Bengal/O. nivara. Preliminary results of the inoculation suggest approx. 10 BC2F2 families are resistant to both blast races, IB-1 and IB-49. QTL mapping results will be presented. The location of the putative blast QTLs identified will be compared to that of known blast genes and the marker–trait associations previously identified in the collection.