Relationship Of Virulence And DNA Polymorphism Of Puccinia Triticina And Its Molecular Detection Of Physiological Race

Wheat leaf rust is one of the important diseases which caused heavy loss of the wheat production in the world. The resistant cultivars has been considered as the most effective measure to control the disease. The "breakdown" of resistant wheat cultivars resulted in the emergence and development of new physiological races of the pathgens. So the survey of race and virulence of Puccinia triticcina is of significance for the breeding for rust resistance and reasonable plant of resistance cultivars.Virulence of eighty four isolates of P. triticcinia were analyzed by using forty near-isogenic wheat lines with known leaf rust resistancegene as the differentials Two dominant races of PHT and THT were found. PHT were surveyed at the frequencies of 46.7% in 2000. 37.5% in 2002 and 37.9% in 2003 respectively, and the frequency of THT had raised to 27.6% in 2003 from the two frequencies in 2000 and 2002. Clustering results indicated there existed obviously difference in virulence of P. triticcinia between Mexico, Austrilia and China. Some similarity of virulence of P. triticcinia isolates were also found in the same wheat growing areas, with the coefficiencies of 0.69 in the Northwest winter wheat area,0.66 in the Southweast winter wheat areas,0.70 in the Huanghuaihai winter wheat areas,0.74 in the middle-low Yangtz River winter wheat areas and 0.77 in the North winter wheat areas.respectively.Thirty-three single-uredinial isolates of P. triticcina were tested for virulence on seedling plants of wheat thatcher lines with known leaf rust resistance genes. And AFLP techniques were also used to analyze the DNA polymorphism of P. triticcina isolates. Through comparing the polymorphism of virulence and molecular genetic, it was found that their clustering graph existed some relative. The coefficient is 0.2184.A total of twenty-three physiological races of Puccinia triticcina from wheat growing-areas of China and Mexico were investigated for the DNA polymorphism by amplified fragment length polymorphism (AFLP). Sixty-four pairs of AFLP primers were used to generate polymorphic bands and one specific DNA fragment was amplified by M05/E03 primer combination in race MFR of Puccinia triticcina. The specific DNA polymorphic fragment, a 325 base pair band, was excised and cloned into T-easy vector. Based on the cloning and sequencing, the AFLP-marker was converted to a sequence characterized amplified region (SCAR) marker. Sixty isolates of Puccinia triticcina were tested with the SCAR marker, indicating that MFR race could be differentiated from the rest races by the specific DNA marker exactly. The results provide an useful aid to establish the system of molecular detection for the physiological races of wheat rust fungi.