Geographic Distribution of Avirulence Genes of the Rice Blast Fungus Magnaporthe oryzae in the Philippines

Abstract

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</p><p>A total of 131 contemporary and 33 reference isolates representing a number of multi-locus<br />genotypes of Magnaporthe oryzae were subjected to a PCR test to detect the presence/absence of<br />avirulence (Avr) genes. Results revealed that the more frequently occurring genes were Avr-Pik<br />(81.50%), Avr-Pita (64.16%) and Avr-Pii (47.98%), whereas the less frequently occurring genes were<br />Avr-Pizt (19.08%) and Avr-Pia (5.20%). It was also laid out that the presence of Avr genes in M. oryzae<br />is strongly associated with agroecosystems where the complementary resistant (R) genes exist.<br />No significant association, however, was noted on the functional Avr genes and the major geographic<br />locations. Furthermore, it was identified that the upland varieties locally known as “Milagrosa” and<br />“Waray” contained all the R genes complementary to the Avr genes tested.</p><br />