| Summary: | In order to understand the pathogenicity differentiation of rice blast fungus (<i>Pyricularia oryzae</i> Cavara), a total of 206 isolates of <i>P. oryzae</i> were collected from three Japonica rice regions in Jilin Province, northeast China. Pathogenicity test showed that the reaction pattern of 25 monogenic differential varieties (MDVs) of rice (<i>Oryza sativa</i> L.) demonstrated a wide pathogenic diversity among the isolates. Those MDVs harbor 23 resistance (<i>R</i>) genes with the susceptible variety Lijiangxintuanheigu (LTH) as control. Virulent isolates of MDVs harboring <i>R</i> genes <i>Pish</i>, <i>Pit</i>, <i>Pia</i>, <i>Pii</i>, <i>Pik-s</i>, <i>Pik</i>, <i>Pita</i> (two lines), and <i>Pita-2</i> (two lines) had high frequencies ranging from 80 to 100%, to MDVs harboring <i>R</i> genes <i>Pib</i>, <i>Pi5</i>(t), <i>Pik-m</i>, <i>Pi1</i>, <i>Pik-h</i>, <i>Pik-p</i>, <i>Pi7</i>(t), <i>Piz</i>, <i>Piz-5</i>, and <i>Piz-t</i> showed intermediate frequencies ranging from 40 to 80%, and to MDVs with <i>R</i> genes <i>Pi3</i>, <i>Pi9</i>(t), <i>Pi12</i>(t), <i>Pi19</i>(t) and <i>Pi20</i>(t) presented low frequencies ranging only from 0 to 40%. The U-i-k-z-ta pattern of race-named criteria categorized the 206 isolates into 175 races. Sub-unit U73 for <i>Pib</i>, i7 for <i>Pi3</i> and <i>Pi5</i>(t), k177 for <i>Pik-m</i>/<i>Pik-h</i>/<i>Pik-p</i>, z17 for <i>Pi9</i>(t), and ta332 for <i>Pi20</i>(t) were crucial on pathogenic differences in regions. Twenty-seven standard differential blast isolates (SDBIs) were selected to characterize resistance in rice accessions. This study could help to build a durable identification system against blast in the <i>Japonica</i> rice area of northeast China and enhance our understanding of the differentiation and diversity of blast races in the world.
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