Abstract: 【Objective】 Wheat growing region in Yunnan Province of Southwestern China plays a pivotal role in spread and epidemic of wheat stem rust disease in China. Thus, once Ug99 and its lineage mutants invade in China, it is highly possible that the pathogen will preferably colonize, repeatedly reproduce and disseminate to entire country. The objective of this study is to clarify the resistant levels of the main wheat cultivars (lines) in Yunnan Province and the Ug99-resistant materials of CIMMYT to wheat stem rust races in China and those Ug99-resistant genes contained in these wheat materials, and to provide guidance for the layout of the resistant varieties.【Method】From Oct., 2013 to Mar., 2014, all of the 119 wheat varieties (lines) from Yunnan Province and 20 of Ug99 resistant materials including the susceptible control Little Club (LC), were sown in the 10 cm diameter clay pots, when the primary leaves were fully expanded or at about 7-day-old seedlings, they were inoculated using talc-urediospore powder mixture of the common races 21C3HTTTM, 34MRGQM and a new race 34C3RTGQM which was obtained from an aecia sample on barberry, maintained humidity overnight in humid chamber, and then transferred to greenhouse for incubation at 15-26℃ (night/day). About two weeks later, when the pustules on LC could be scored into type ‘4’, the infection types (ITs) on test cultivars (lines) were investigated and recorded. The IT standard was determined in accordance with ‘0-4’ (0-2⁺ being resistant and 3^--4 being susceptible). The IT data were used to appraise the resistance of the tested materials. In addition, the primary leaf tissue of each healthy test cultivar (line) was taken to extract genomic DNA, amplified with the reported specific primer pair of Ug99 resistant genes (Sr22, Sr25, Sr26 and Sr28)and detected through 2.0% agarose gel electrophoresis as well as polyacrylamide gel electrophoresis for the resistance gene marker (s) to figure out those genes carried in tested cultivars (lines).【Result】Of the 119 tested varieties (lines), 42 materials were resistant (accounting for 35.3%), with 6 materials being immune or nearly immune (5%), 36 materials were highly resistant or moderately resistant (30.3%) and the rest (77 materials) were susceptible with 42 materials being highly susceptible (35.2%) and 35 materials moderately susceptible (29.4%). Of the 20 CIMMYT’s materials, two were highly susceptible (10%) and two moderately susceptible (10%). The result of molecular marker detection indicated that two CIMMYT’s materials contained Sr25, one contained Sr26 and one contained Sr28.Interestingly, 12 of Yunnan materials were met with the same one gene, ie. Sr28.【Conclusion】To the races tested, the resistant level of wheat varieties (lines) in Yunnan is considerably low and a small section of CIMMYT’s materials show some degrees of susceptibility, too. However, the 12-Sr28-carrying materials are Ug99 resistant resources rarely reported in China.

Key words: wheat stem rust, resistance of cultivars, Ug99, gene, molecular detection