On Biological Characteristics And Their Inheritance Of Fusarium Solani Causing Tree Peony Root Rot In Tongling

The causal organism of tree peony root rot was identified and a systematic research was done on biological characteristics, inheritance stability of biological characters, vegetative compatibility, electrophoresis analysis on esterase isozymes and soluble protein of Fusarium solani and on screening of effective fungicides controlling causal organism of tree peony root rot. The test results were as follows:1. Identification of the Causal Organism of Tree Peony Root RotAccording to the classification system of C. Booth and Nelson, 12 strains isolated from tree peony root rot in Tongling, Anhui were identified as Fusarium solani through its morphology and culture characteristics and biological characteristics.2. Biological characteristics of Fusarium solani caused tree peony root rotThe studies on the biological characteristics of Fusariun solani showed that the pathogen could use many carbohydrate and nitrogen sources, but the optimum carbon sources were glucose, maltose and mannose. The optimum medium for conidial production was sucrose. Fructose and maltose, as sources of carbon, were more optimum for mycelial growth of Fusariun solani inTiquid medium. The optimum nitrogen sources were (NH₄)₂HPO₄, KNO₃ and NH₄NO₃ respectively. The optimum medium for conidial production was NH₄NO₃, and the growth of Fusariun solani in liquid medium showed that NaNO₃, as a source of nitrogen, was optimum for mycelial growth. The optimum media for mycelial growth of Fusariun solani were potato I and potato II, and the conidial production in the soluble starch medium was the highest one. The hyphae could grow in 10-35℃, the optimum temperature was in the range of 25-30℃, and the temperature lower than 5℃or higher than 40℃was not fit for the mycelial growth, the lethal temperature of conidial was 52℃for ten minutes. The mycylia could grow under the condition of pH 4.1-12.5, and the optimum were pH 5.5 and pH 10.3, the optimum pH for conidia spore germination was between 3.99 and 7.0.3. Inheritance stability of biological character of Fusarium solani isolates inconidium progenyThe test result showed that the colony morphology and mycelial growth rate could be stably inherited in macroconidia progeny, no significant difference on morphology and mycelial growth rate among spores in later generation. The colony morphology of MD-1-5 and GH-1-1, with nearly circular and neat colony, was identical with its parental strains in each generation. The mycelial growth rates of strains MD-1-5 and GH-1-1 were nearly the same in each macroconidia generation. The strains of asexual spores of F-3 were nearly the same to its parental strain on colony morphology and mycelial growth rates, and no significant differences were existed in strains from F-3 on mycelial growth rate.4. Studies on the vegetative compatibility of Fusarium solani causing treepeony root rotAmong 12 Fusarium solani isolates, we totally got 99 nit mutants by using chlorate medium. All of the nit mutants were then transferred into the media containing different nitrate as single nitrogen source to find which nit type they belonged to. Among the 99 nit mutants, 64 nit mutants were nit1,19 nit mutants were nit3, and 16 nit mutants were nitM. Complementation occurred between the different nit mutantphenotypes derived from the same parental strain. Complementation occurred readily and reliably in nitM which was used to identify the vegetative compatibility of other nit mutants, and the test results showed 12 isolates belongs to 3 vegetative compatibility groups. The nit mutants were all transferred on the PDA medium, and the most majority of nit mutants were stable except 4 nit mutants.5. Analysis on esterase isozymes and soluble protein electrophoresisThe soluble protein and esterase isozyme of 12 isolates of Fusarium solani, the causal organism of tree peony root rot in Tongling, were analyzed by the technique of electrophoresis. The results showed that there was only one main band at Rf 0.78 in esterase isozyme electrophoresis of the 12 isolates. The soluble protein patterns were obviously different among the 12 isolates tested, and they can be classified into 4 types. Of 12 isolates, 2 isolates belonged to Type A having 8 main bands, occupying 16.7% of the total. Eight isolates belonged to Type B having 7 main bands, occupying 66.7%. Type C and Type D had 6 and 5 main bands respectively, including 1 isolate (occupying 8.3%) each. The soluble protein bands were mainly distributed in 3 areas: the Rf in Area I was from 0.24 to 0.36, Rf in Area II was from 0.42 to 0.67, and Rf in Area IIIwas from 0.70 to 0.79. The three bands at Rf 0.24, Rf 0.36 and Rf 0.42 were the specific bands of the pathogenic fungus. Both esterase isozyme and soluble protein electrophoresis showed similarity among the isolates tested and low variation in species.6. Screening tests of the effective fungicides controlling tree peony root rotToxicity of 6 fungicides to Fusarium solani which caused tree peony root rot were tested by the means of mycelial growth method and spore germination method under the condition of laboratory, respectively. The toxicity result by the way of mycelial growth method showed that the order of EC50 values of 6 fungicides was as following: Azoxystrobin>Chlorothalonil>Difenoconazole>Mancozeb> Carbendazin> Prochloraz; the inhibition effect of Prochloraz against the pathogen was significant among those fungicides being tested. The toxicity result by mean of spore germination method showed that Chlorothalonil, with EC₅₀ value as 0.343 mg·L^-1, has the highest toxicity on the fungus. Toxicity of Prochloraz, Difenoconazole, Carbendazin, Mancozeb were gradually weakened in turn, with the toxicity of Azoxystrobin being the lowest one.