Population genetic diversity of Pyricularia grisea on rice in Portugal
1999
Lima, A. (Instituto Superior de Agronomia, Lisbon (Portugal). Dept. de Proteccao das Plantas e de Fitoecologia)
Rice blast caused by Pyricularia grisea is a serious disease on rice in Portugal. We present a genetic study on this fungus from rice in Portugal. Monoconidial isolates of the pathogen were collected, in 5 regions, from 12 rice cultivars during 1991-1996. Among the 192 combinations made with 4 fertile tester, 85% of the isolates behaved as female sterile MATI-1 and 15% as neuters. We inoculated 110 isolates by spraying and by injecting on a differential set of Japanese cultivars. Frequency of virulent phenotypes ranged from 0.0 to 0.93. The highest frequencies were obtained with the genes Pi-a (0.93), Pi-i(0.87), Pi-ks (0.78) and Pi-t (0.78). The resistance gene Pi-ta and Pi-b had no complementary virulence genes when the isolates was inoculated by pulverisation. A low level of Genetic Diversity was found (HT=16,2% and HS=15,5%) the diversity between regions (DST) was 0.0075. Twenty five physiological races were identified. After inoculating rice cultivars grown in Portugal since 1940, we concluded that some of these possessed genes for resistance. Using RAPD technique we divided the isolates on physiological races into lineages
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