Issam Al-Khlifa
General Commission for Scientific Agricultural Research-
Aleppo Research Center
Faculty of Agriculture, Aleppo University

Abstract

The study was conducted in the fields and laboratories of the International Center for Agriculture Research in the Dry Areas (ICARDA) during the growing season 2007 – 2008. The study aims to.
(i) determine the virulence of wheat stem rust fungi in Syria.
(ii) isolate and determine the most virulence and the latest virulence race in the natural population of Puccinia graminis pres.f.sp.tritici fungi.
(iii) study the behavior of resistance and the mode of inheritance in some bread wheat cultivars; and determine a number of genes conferring resistance.
1. Isolation and determination of physiologic races of wheat stem rust fungi
During the season 2007, sixty infected plant samples from the fields of the International Center in the Dry Areas (ICARDA) and twenty samples from different regions in Syria were collected. Single spore were isolated from each infected sample and multiplied on seedlings of the susceptible cultivar Morocco. The differential set which used in the nomenclature of the physiologic races was inoculated separately with each isolate. Furthermore, seedlings of the Near Isogenic Lines (NILs) were inoculated.
The study showed the presence of 18 physiologic races spread in Syria during 2007 season: (BBBCC-BBHBC-GBHHM-GBHBP-GBHCC-JJHBC-JDBBC-KDCKM-LMBGR-LGDHP-MTBJT-MQDSF-RKBSK-RKJSR-RSKTK-RTGPT-RTJSR-RTKTP).
The weakly race BBBCC was able to attack two resistance genes in the differential cultivars and the most virulent race RTKTP was able to overcome seventeen resistance genes. The study also indicated that the physiologic races were varied in their pathogencity in the Near Isogenic Lines. The data showed that the most weakly race was BBBCC which found in Yhmol but the  most virulence race was KDCKM found in Al-Shegh Othman I Hassakeh province. In spite of the virulent of the physiologic races of stem rust fungi which found in Syria during the growing season 2007, still there is  a number of resistant genes such as sr (24,31,33,36,sr) can be used in the breeding programs to produce resistant cultivars to this disease.
2.  Inheritance of resistance in bread wheat
Seven bread wheat cultivars were used in the study, three as a resistant parents to stem rust disease (Pyn/bau//Milan, Cham-6/ww 1402, Samar-12/dollarbird) and four as a susceptible parents (Cham-4, Cham-6, Kasyon/genaro.81//cham-4, Cham-6/ghurab ‘s’//regrag-1).The parents were planted in the field during the cropping season 2007.The crosses were done in one direction, therefore each resistant parent was crossed with all susceptible parents 3—4=n. To get the (F1) plants the hybrids were planted in plastic pots at the plastic house. The parents were planted in pots nearby the hybrids to back crossed.
Seeds of parents, hybrids, (Bc1) and (F1) progenies were divided into two part and planted in two isolated plastic house for artificial inoculation. The artificial inoculation was done separately in each plastic house. The reaction types of the plants were evaluated at heading stage. Although seedlings of parents, (F1), (F2) and (Bc1) were evaluated against the two races under controlled conditions.
The statistical analysis and study of the segregation were done using X2 test.
2.1 Against the race BBBCC:
–  Reaction type of the parents:
Test of reaction type of the parents in seedling and adult plant against the race BBBCC showed that the cultivars (Pyn/bau//Milan, Cham-6/ww 1402, Samar-12/dollarbird) were resistant to race BBBCC in the two stages, while the parents (Cham-4, Cham-6, Kasyon/genaro.81//cham-4, Cham-6/ghurab ‘s’//regrag-1) were susceptible at the two stages.
–  Reaction of the F1s:
Results of the reaction type of F1 hybrids of susceptible — resistant parents showed that the resistant were dominant in all crosses.
–  Reaction of the F2s:
Segregation in F2 progenies of the crosses of the susceptible parent Cham4 with the resistant parents (Pyn/bau//Milan, Cham-6/ww 1402, Samar-12/dollarbird) showed that resistance was controlled by one dominant gene at both stages seedling and adult plant.
Results of F2 segregation of the crosses of the susceptible parent Cham-6 with the resistant parents (Pyn/bau//Milan, Cham-6/ww 1402) showed that the resistant was controlled by one dominant gene in seedling and adult plant, while with the resistant parent (Samar-12/dollarbird) was controlled by two genes interact in epistasis way in seedling stage and two complementary genes at adult plant stage.
Results of segregation in F2 progeny of the crosses of the susceptible parent (Kasyon/genaro.81//cham-4) with the resistant parents (Pyn/bau//Milan, Samar-12/dollarbird) showed that resistant was controlled by one dominant gene in seedling and adult plant, while with the resistant parent (Cham-6/ww 1402) the resistant was controlled by two genes interact in epistasis way in seedling and adult plant.
Results of segregation in F2 progeny of the crosses of the susceptible parent (Cham-6/ghurab ‘s’//regrag-1) with the resistant parents (Pyn/bau//Milan, Cham-6/ww 1402) showed that resistant was controlled by two genes interact in epistasis way in seedling stage and two complementary genes at adult plant stage. While with the resistant parent (Samar-12/dollarbird) the resistant was controlled by one dominant gene in seedling and adult plant.
2.2 Against the race RTKTP:
–  Reaction type of the parents:
Test of reaction type of the parents in seedling and adult plant against the race RTKTP showed that the cultivars(Pyn/bau//Milan, Cham-6/ww 1402, Samar-12/dollarbird) were resistant to race BBBCC in the two stages, while the parents (Cham-4, Cham-6, Kasyon/genaro.81//cham-4, Cham-6/ghurab ‘s’//regrag-1) were susceptible at the two stages.
–  Reaction of the F1s:
Results of the reaction type of F1 hybrids of susceptible— resistant parents showed that the resistant were dominant in all crosses.
–  Reaction of the F2s:
Segregation in F2 progenies of the crosses of the susceptible parent Cham4 with the resistant parents (Pyn/bau//Milan, Cham-6/ww 1402, Samar-12/dollarbird) showed that resistant was controlled by one dominant gene in both stages seedling and adult plant.
Results of F2 segregation of the crosses of the susceptible parent Cham-6 with the resistant parents (Pyn/bau//Milan, Cham-6/ww 1402) showed that the resistant was controlled by one dominant gene in seedling and adult plant, while with the resistant parent (Samar-12/dollarbird) was controlled by one dominant gene in seedling stage, whereas was controlled by two genes interact in epitasis way at adult plant stage.
Results of segregation in F2 progeny of the crosses of the susceptible parent (Kasyon/genaro.81//cham-4) with the resistant parents(Pyn/bau//Milan, Cham-6/ww 1402, Samar-12/dollarbird) showed that resistant was controlled by one dominant gene at both stages seedling and adult plant.
Results of segregation in F2 progeny of the crosses of the susceptible parent (Cham-6/ghurab ‘s’//regrag-1) with the resistant parent (Pyn/bau//Milan) was controlled by one dominant gene in seedling and adult plant, while with the resistant parents (Cham-6/ww 1402, Samar-12/dollarbird) was controlled by two genes interact in epistasis way in seedling stage and one dominant gene at adult plant stage.