Pyricularia grisea fungus which causing rice blast disease is one of the main pathological races threats to rice crop in Egypt and worldwide. Thirty isolates out of known 144 strains of this fungus were selected according to geographical locations. Isolates of P. grisea, were analyzed by SSR markers to determine the amount of genetic variability among these races. Sixteen primers out of 26 were amplified and produced a total of 83 alleles . Number of alleles per marker ranged from 3 for C7-1.4, P9-0.4 and P9-1.9 to 9 for H6-0.8-5 primer, with an average of 5.2. The polymorphic information content (PIC) values were high for all markers with an average of 0.70 and ranged from as low as 0.51 for C7-1. 4 to high of 0.83 for H6-0.8-5 marker. UPGMAcluster-analysis based on genetic distance coefficients clearly separated all isolates of P. grisea. The results showed that the studied isolates were classified into 4 lineages by cutting off the dendrogram at 0.70 similar linkage level. Group D was the major group and represented most of those isolates. The average similarities within cluster was greater than the average similarities between clusters. In general, the results of this investigation confirmed that microsatellite markers would be useful and suitable for determining the genetic diversity in P. grisea populations.
Experiments were carried out at Rice Research and Training Center during 2009 to 2012 growing seasons. This study aimed at evaluation of some commercial Egyptian rice cultivars and some promising lines against blast disease, identification of effective rice blast resistant genes, and distribution of physiological races and common races of Pyricularia grisea. One hundred and thirty two of P. grisea isolates were collected from rice-cultivating governorates in Egypt, namely Kafr EL-Sheikh (36 isolates), Gharbia (48 isolates), Dakahlia (18 isolates), Sharkia (12 isolates), Damietta (6 isolates) and Beheira (12 isolates). IH race group was the most common race (47.69%), followed by IC (26.58%) and IF (12.15%) groups, While IG, ID and IE (6.06, 6.04 and 1.49%, respectively) were the minor race groups during this study period. The promising line GZ 9057-6-1-3-2 revealed the highest level of resistance against most isolates tested (98.48%) followed by Giza 178 and GZ 9523-2-1-1-1 (96.22% for each). On the other hand, the susceptible rice cultivars, Sakha 101 and Sakha104, were infected with the most tested isolates (25.76 and 61.36 % resistance, respectively). Pi-z-5 gene found in IRBLz5-CA and IRBLz5-CA (R) lines scored the highest effective gene of blast resistance (97.76 and 95.50%, respectively). This gene was followed by pita-2 gene, found in the monogenic line IRBLta2-Re (91.70%). On the other hand, Pia gene found in IRBLa-A and IRBLa-C lines was the lowest effective resistant gene with zero efficacy against the tested isolates. The highest percentage of race groups from the total identified isolates were obtained from Gharbia and Kafr El-Sheikh governorates (36.53 and 27.27%, respectively). On other hand, Damietta governorate had the lowest percentage of race groups (4.56% from the total identified races).
Ten commercial rice cultivars were evaluated to partial resistance for blast disease under greenhouse conditions at Rice Research and Training Center, Sakha, in 2000 season .Ten isolates of Pyriculuria grisea collected from different locations were tested and identified on the international differential rice varieties (IDV) and commercial rice cultivars. Five from the new cultivars i.e Giza 177, Giza 178, Sakha 101, Sakha 102, and Sakha 104 showed susceptible reactions to one or two of the tested isolates. Giza 159 and Giza 171 were susceptible to all tested isolates. The isolates placed in seven race-groups i.e. two isolates for each of group IA, IC and ID, whereas, one isolate conformed each of IB, IG, IH and II races. Two races I A-69 (Isolate No.5) as highly virulent and IG-1 (isolate No.52) as a less virulent on the IDV were selected to study partial resistace parameters. Total number of lesions / leaf or plants, sporulation density and lesions type that developed differed greatly among cultivars. The number of lesions decreased by increasing leaf age. High numbers of necrotic spots (type 1-2) on new rice cultivars than on old cultivars could be attributed to hypersensitivity phenomenon. The new rice cultivars had lower number of type 4 lesions and less number of spores / lesion (sporulation capacity) than the old cultivars. This is may reflect a level of partial resistance in addition to major gene effects on the new cultivars than the old ones.
The study aimed to evaluate certain commercial Egyptian rice cultivars in both seedling and adult stages to blast disease, identify rice blast hot spots at different rice governorates, and identify effective rice blast resistance genes and common physiological races of Pyricularia grisea under field conditions during 1994 to 2007 seasons. Fourteen Egyptian rice cultivars were tested during the period of study. In addition, ten Japanese differential varieties and two international differential varieties evaluated at three locations i.e. Sakha, Gemmiza and Zarzora were included and tested under natural infection at blast nursery tests.As for field resistance, the cultivars Giza 171
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