Studies On The Mechanisim Of Trichoderma Aureoviride Against Pythium Aphanidermatum Causing Turfgrass Root Rot And Its Biocontrol Preparation

1. In 2007 and 2008, Pythium root rot of the truf grass was surveyed in 13 districts of Lanzhou City. The results showed that the incidence in the most serious fields was 83.33%, the disease index was 36.67. The disease caused different symptoms on different position of turf grass. Three types of symptoms on the turf grass were observed: Leaf tip blight, Leaf middle shrink and Rhizoma-brown rot. The chief pathogen, according to their morphology, cultural characteristics and pathogenicity, was identified as P.aphanidermatum (Edson) Fitzpatrick, the isolation frequency was 100% in rhizome. The incubation period for P.aphanidermatum (Edson) Fitzpatrick was 14～15 hours at 30℃and RH 90%.2. The hyphae of root rot pathogen for P.aphanidermatum (Edson) Fitzpatrick could grow from 15℃to 35℃, the rang of fit temperature was 20~25℃; optimal pH value was 7~8; The best cultural condition for hyphal growth was 24 h darkness while 24h illumination was the worst cultural condition. Ultraviolet Irradiation could accelerate the growth of hyphae; The best resourse of C are amylum , and the best resourse of N are ammonium nitrate; The pathogen hyphae could grow in CAA very well, in PDA and TCA the thickness of mycelium is bigger.3. According to confront culture, the Trichoderma aureoviride could inhibit the growth of Pythium aphanidermatum causing Turfgrass Root Rot. It could cover the P.aphanidermatum colony and produced large number of conidia. The effective concentration was at 4.65×10~6 cfu/ml, and the inhibitory effect reached 53.56%. Comparing the inhibition effect of T. aureoviride suspension with three kinds of fungicides against P.aphanidermatum, the T. aureoviride with the concentration of 107cfu/ml had the same effect as 25% metalaxyl. The inhibition rates were 77.37% and 79.57%, respectively. By Microscopic observation , the results showed that T. aureoviride either enwinded to the hyphae of P.aphanidermatum or grew parallel with the hyphae of P.aphanidermatum, then penetrated and parasitized in them. The main antagonistic mechanism of T. aureoviride against P.aphanidermatum was hyperparasitism.4. Trichoderma aureoviride was used in the study to describe the quantitative changes of bacteria,actinomycetes and fungi in soil of turfgrasses. The results showed that the amount of soil microbes was abundant , however , the difference of quantity among three microbes and the quantity from high to low was in the order : bacteria >actinomycetes >fungi . T. aureoviride could change the Soil Microflora significantly. The number of soil bacteria increased Slowly, the number of soil fungi decreased obviously and there was no obvious change in the actinomycetes.5. By measuring the speed of colony growth and sporulation per unit area, Carried out the biological compatibility about used additives and T. aureoviride. In the test of carriers, the silica gel and control were no significant difference; In the test of fungicide, the metalaxyl 3000X and Control was no significant difference; In the test of UV-protector, the humic acid no significant impact on the vitality of T. aureoviride. Determined the additives which had good biological compatibility with the T. aureoviride, provided an important basis for T. aureoviride biocontrol preparation...