Identification And Biological Characteristics Of The Causal Organisms Of Soybean Fusarium Root Rot In Anhui

One hundred and eighty five Fusarium isolates were identified by different selectiveculture medium cultivating diseased-partition, cut and divided from one hundred and tensamples collected from Soybean root rot fields of Huaiyuan in Anhui. By single-sporeisolating of185Fusarium strains, the results of species identification based on morphologyand molecular showed that: these Fusarium isolates belonged to six species and a varietiesas follows：F. solani, F. oxysporum, F. avenum, F. graminearum, F. acuminatum, F.proliferatum and F. solani var.coeruleum. Their occurence frequency were32.2%,23.5%,13.7%,12.3%,8.7%,6.2%and3.4%, respectively, with that of F. solani being the highest,F. oxysporum the second, F. solani var. coeruleum being the lowest.The results of the pathogenicity comparison of various Fusarium isolates by means ofinoculating the soybean seedlings with the method of the spore suspension root-dippingshowed that F. solani had the most virulence and the F. oxysporum followed by the second,F.proliferatum had the worst virulence.The biological characteristics of F. solani, the main causal organism of soybeanFusarium root rot in Anhui were investigated further, and the results were as follows:(1) The mycelium could grow at10-40℃，with the optimum temperature being in therange from20℃to30℃. It couldn’t grow below5℃, the mycelium. grow slower below10℃and above40℃. The conidial productionhad linear positive correlation with thetemperature. that is from5℃of not produce conidia to35℃of producing moreconidia.When it comes to40℃,the conidial production of the F.solani begin to fall.Theconidial could germination at10-40℃, with the optimum temperature being in the range of20℃-40℃, It couldn’t germination below5℃.(2) The mycelium could grow under the condition of pH5to12. The growth rates ofthe mycelium and the conidial production of the F.solani were optimal under the conditionof pH5, The conidial production and the growth rate of the F.solani is linear negativecorrelation being in the range of pH5-pH12. The conidiospore could germinate under thecondition of pH5-12, with the optimum pH for conidiospore germination being between5.0and7.0.(3) The optimum condition for the mycelium growth of F. solani was in dark.Alternation of light and dark followed by the second, and under the condition of light wasthe most negative. By contrast, under the condition of the light was good for theconidiospore production and conidiospore germination. Alternation of light and dark followed by the second, under dark condition was worst.(4) Studies on the influence of the different solid medium, carbon sources andnitrogen sources to the mycelial growth and conidial production of the pathogen werecarried out, and the results showed the better media for mycelial growth of F. solani wasPDA media among the7tested media. Oat meal media followed by the second, theconidial production under different medium exist remarkable differences. The optimummedium for conidial production was Czapek medium. It’s production outclassed othermediums. PSA media followed by the second. For mycelial growth and conidialproductionon solid media.The optimum carbon source was sucrose,maltose followed bythe second. The optimum nitrogen sources for mycelial growth was urea, NH4NO3followed by the second.The optimum nitrogen sources for conidial production wasNH4NO3.Virulence test of seven pesticides to the pathogen showed that EC50为0.8125mg/L ofdiniconazole against pathogen was best. carbendazim, propiconazole and triadimefonsubsequently and its EC50respectively was2.3837mg/L，2.7428mg/L，3.6025mg/L,effected of EC501393.9588mg/L of Mancozeb on pathogen was worst.