Crop Biotech Update

Developing DNA Markers of Rice Blast Resistance Gene Locus

May 21, 2010

Rice blast caused by the fungal pathogen Magnaporthe oryzae is one of the major problems in rice production all over the world. The use of host resistance is still the most efficient method for disease management. Many resistance (R) genes have been identified and one of which is the Pi-km. To facilitate rice breeding programs, Stefano Costanzo and Yulin Jia of the U.S. Department of Agriculture Agricultural Research Service developed a Pi-km specific DNA marker using 15 US rice cultivars. Based on the DNA sequence analysis and computational translation conducted, the researchers found six alleles within the Pi-km locus. Moreover, artificial blast inoculations with some rice cultivars exhibited high levels of sequence polymorphism of the blast isolates which are associated with specific Pi-k genes. Such occurrence introduces new insight about the complex characteristic of the R gene locus, which may greatly affect the recognition of the pathogen-encoded signalling substances for defense reaction.

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