| Phytophthora sojae is an important plant pathogenic oomycete that causes Phytophthora root rot of soybean(PRRS).PRRS is still classified as plant quarantine object in China.The oomycete and soybean blight caused by it were discovered in Helongjiang,Fujian and Anhui successively,and the disease in Helongjiang and Fujian were more serious.However,the difference among the three districts of the oomycete are unknown to date.In this dissertation,a systematic study was carried out on 12 test strains in Fujian,Anhui and Heilongjiang provinces under different environmental conditions,and the effects of different temperatures,different media and different pH on the growth of Phytophthora sojae were discussed.The pathogenic differences of soybean phytophthora strains from different sources were studied and compared,and the main results were as follows.1 Tests of the influence of temperature on mycelium growth and lethal temperature of different isolates in Phytophthora sojaeIn this paper,the growth of mycelium of soybean Phytophthora strains with different sources in different temperature conditions was discussed.The results showed that the optimum growth temperature range of the strains HY25 and HY22 and Gz16-2 was 20?~25?,and the optimum growing temperature of the 25?~30?,hy11-2 was 2,and the most suitable growth temperature for 1 and 3rd strains in Heilongjiang province was 25?~30?,while that of the number of the bacteria in the strain of soybean strains of strain No.The 4th strains were more suitable for growing when the temperature was 20?~25?.The optimum growth temperature of soybean Phytophthora strains in Fujian province is 25?~30?,wherein YY1460 is suitable for growth when the temperature is 20?-30?.The results of determination of lethal temperature showed that the lethal temperature of each strain was different.The lethal temperature of the test strains in Fujian province was 50 ?.The lethal temperature of gz16-2 and Hy11-2 was 49 ? in the test strain of Anhui province,and the lethal temperature of HY22 and HY25 was 50 ?.In the test strains of Heilongjiang province,the mycelial lethal temperature of strain 1 and strain 3 was 49 ?,and the mycelial lethal temperature of strain 2 and strain 4 was 48?.2 Effects of different pH on mycelium growth of different isolates in Phytophthora sojaeThe results showed that the mycelial growth rate and colony morphology of the test strains in different provinces showed obvious differences.The strains were the slowest growth in pH4 and pH11,and they grew faster in Ph6-8,when the pH 7 was the most suitable and hypha growth.Phytophthora sojae strains can grow between pH 4-11,but the strains in Fujian province grow faster than neutral-alkali environment in neutral-acid environment.Under the condition of pH 4,the colony diameters of the test strains in Anhui and Heilongjiang province were less than 20 mm,and under the condition of alkaline environment,the strain growth was faster than that of the acidic environment.Although all strains can grow under the environment of partial acid and alkali,the mycelium is slender,sparse structure,uneven distribution and irregular edge in the environment of alkali.3 Effects of different medium on mycelium growth and oospore production of different isolates in Phytophthora sojaeThe mycelium of 1 and 2nd in Heilongjiang was the fastest growing in Lima Bean Medium(LBA),and the average velocity of 9.62 mm/d and 10.57 mm/d,3 and 4th was the fastest growth in potato medium(PDA),and the average velocity was 10.17 mm/d and 9.76 mm/d respectively.The growth rate of Anhui test strain hy11-2 on oat medium(OMA)was the fastest,reaching 11.20 mm/d,HY22,Gz16-1 and HY25 had the fastest growth rate in vegetable juice medium(V8),11.42 mm/d,10.25 mm/d and 11.28 M/D,the growth rate of BS1450,BS1428 and YY1460 in the vegetable Juice Medium(V8)was the fastest,and the mycelial growth rate was 10.31 mm/d,10.88 mm/d and 11.36 mm/d,and LK1518 on the Lima Bean Medium(LBA).Growth is best,averaging 8.86 mm/d.The correlation between mycelial growth rate and spore yield showed that the correlation was not significant.It was indicated that different media had significant effect on the growth rate of soybean Phytophthora strains and oospores,and there were significant differences between strains.The growth rate and spore formation ability of mycelium were different with the same culture medium.4 Sporangium difference of different isolates in Phytophthora sojaeThe results showed that the spore sac produced by the strains of LK1518 and Anhui HY22,HY25 and Heilongjiang strains 2 and 3 were similar,mostly oval,pear-shaped or similar spherical,and the strain Sporangia mastoid was not obvious.In addition to these five strains,the remaining 7 strains have obvious mastoid structure.There was no difference in morphology between the spore sac morphology of each strain except the mastoid.Although the size,length and width of the spores and the length of the stems and the mastoid process were obviously different,there was no significant difference in the mean.5 Tests of pathogenicity of different isolates in Phytophthora sojaeThe results showed that in the artificial culture environment,the disease spot diameter of strain BS1450 and HY25 was larger than that of other strains,which showed that the infection ability was stronger under the condition of laboratory.Strains 1,3 and 4th in Heilongjiang Province were less pathogenic than those in other provinces. |
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