Studies On Isolation And Identification Of Mycoparasites From Pathogens Of Powdery Mildew And Its Biological Characteristics

Powdery mildew is one of the most important plants diseases in China. The powdery mildew fungi which causing severe damage and difficult to control have a wide range of hosts, various ways to spread and fast speed to be epidemic. Mycoparasitisim is fungi themselves parasite by other fungi which is a common phenomenon in nature. As one of the main mechanisms for controlling plant diseases, mycoparasitism has obtained more and more domestic and foreign plant pathologists′ attention. Ampelomyces quisqualis is the most frequently reported mycoparasites on powdery mildew fungi, and has been developed commercial biocontrol agents AQ10 and Q-fect in several foreign countries. In order to clarify the species and distribution of mycoparasites on powdery mildew fungi, so as to lay the foundation for screening and identifying potential biocontrol isolates in further, the author collected samples infected powdery mildew from the western region of Guanzhong Shaanxi, including Chencang District of Baoji, Mei County, Zhouzhi and Yangling. The method combining morphological identification and rDNA-ITS molecular identification was used to classify and identify the mycoparasites on powdery mildew. On this basis, the biological characteristics of representative strains of different species of mycoparasites of powdery mildew were analyzed and compared. Furthermore, the ability to parasite cucumber powdery mildew of representative strains was determined under greenhouse conditions, the results are as follows:1. In western region of Guanzhong Shaanxi including Chencang District of Baoji, Mei County, Zhouzhi and Yangling,the author collected 10 families, 16 genera plants infected powdery mildew and isolated and identified 17 strains of mycoparasites which parasited powdery mildew in nature. The mycoparasites parasited plants mainly distributed in four families which were Asteraceae, Cucurbitaceae, balsaminaceae, Solanaceae. The 17 strains of mycoparasites were identified as Ampelomyces quisqualis, Ampelomyces humuli and Phoma glomerata by r DNA ITS molecular method. Furthermore, the Ampelomyces humuli and Phoma glomerata were isolated from the plants infected powdery mildew fungi in nature for the first time in China.2. The 5 isolates represented Ampelomyces quisqualis, Ampelomyces humuli, Phoma glomerata were selected to determine the effect of different temperature, pH, C source, N source and culture medium on their growth. The results showed that all tested strains can grow at 5-35℃, the optimum temperature was 20-25℃, in which the optimum growth temperature of CF6-1, CF6-2, CF8-3 was 25℃, the optimum temperature of CF12-2, CF4-3 is 20℃. Each strain grew well in the PDA medium with pH5-10, especially at pH 5-7. Stains CF6-1, CF12-2, CF4-3, CF6-1, CF5-2, CF8-3 utilized lactose, soluble starch, fructose, sucrose, maltose, glucose better, and the differences between different carbon source was not significant. The N source which conducive to the growth of each strain was glycine, NaNO3, but the utilization of NH4NO3 was poor. Strains could grow well in various media, especially grew best on Czapek-Dox Ager medium, wherein CF4-3, CF5-2, CF8-3 grew pooly on BA medium.3. The ability to parasite cucumber powdery mildew of 5 strains represented Ampelomyces quisqualis, Ampelomyces humuli and Phoma glomerata was determined under greenhouse. The results indicated that Ampelomyces quisqualis, Ampelomyces humuli and Phoma glomerata all could parasite cucumber powdery mildew fungi, and the ability of the 5 isolates was different, which the parasitic ability of Ampelomyces quisqualis was strong, Ampelomyces humuli was moderate and Phoma glomerata was weak.