Isolation And Identification Of The Pathogens Causing Root Rot Disease In Alfalfa And The Evaluation Of Alfalfa Resistant Varieties Resistance To Fusarium Spp.

Alfalfa root rot is the most common root disease.It occurs in all alfalfa planting areas and can cause alfalfa production and quality to decline,which seriously affects the development of animal husbandry in China.The pathogens of alfalfa root rot are more complicated,and the types of the pathogens vary from region to region and environment.Therefore,clarifying the species and dominant strains of alfalfa root rot in different ecological environments is very important for the prevention and control of alfalfa root rot.In this study,Koch’s law was used to isolate and identify suspected root rot samples from alfalfa fields collected from three different locations in Hohhot,Ordos,and Xing’an League in Inner Mongolia.The biological characteristics of the isolated pathogenic strains and the mutual pathogenicity between different hosts were studied,and the resistance of different alfalfa varieties to root rot was evaluated.The results obtained are as follows:1.Disease samples from suspected root rot in alfalfa fields collected from three different locations in Hohhot,Ordos,and Xing’an League were isolated and identified.A total of 9 different species of isolates were obtained,which are Fusarium equiseti,F.acuminatum,F.thapsinum,F.incarnatum,F.oxysporum,F.tricinctum,Rhizoctonia solani,Bipolaris sorokinian and Plectosphaerella cucumerina.these 9 isolates were identified for pathogenicity and found to be pathogenic.2.In the study of the biological characteristics of the isolated pathogenic strains,the effects of temperature,p H,light,and different media on the growth of alfalfa root rot were mainly studied.The experimental results as shown,XAMJ-4(F.thapsinum),CYS1-3(F.oxysporum),and MS-7(R.solani)showed no significant difference in growth in the four media,and the remaining 6 pathogens were in different media.There are different degrees of undergrowth.The temperature range for the growth of mycelium of 9 pathogens is 5-40℃.Except for the optimal temperature of MX1(F.tricinctum)is 20℃,the temperature of the remaining 8 pathogenic bacteria is 25℃.Nine kinds of pathogens can grow at p H 4-11,but the hyphae growth of MS-2(B.Sorokinian)and MS-7(R.solani)strains is less affected by p H than the other seven.Some strains exhibit acidic properties,such as XAMG-6(F.equiseti)with an optimal p H 5.MX1(F.tricinctum)and MS-7(R.solani)grew faster under full darkness than under full light and alternating light and dark.XAMG-6(F.equiseti),CYSG-1(F.incarnatum),and CYS1-3(F.oxysporum)grew most slowly under full darkness.3.Cross-pathogenicity studies on Fusarium isolated from alfalfa and other Fusarium from different host sources have found that Fusarium on alfalfa can also infect sunflowers and potatoes,while Fusarium on potatoes and sunflowers also affect Has different degrees of pathogenicity.And it has the characteristics that its pathogenicity is stronger than that of other hosts.4.Thirty-two different alfalfa varieties were selected to study the resistance level of alfalfa root rot.The study found that for MX1(F.tricinctum),there were 18 alfalfa varieties showing a medium resistance level,accounting for 56.25% of the tested varieties.Varieties are representative.there are 14 medium-sensing varieties,accounting for 43.75%,and Gannong No.6 is the representative.no varieties showing high sensitivity to Fusarium spp.For MX2(F.equiseti),9 alfalfa varieties exhibiting medium resistance levels,accounting for 28.13%,are represented by the large galaxy varieties.14 varieties exhibiting medium sensitivity,accounting for 43.74%,which is based on standard standards.Zhun Geer variety as the representative.nine varieties represented b y Zhaodong showed high sensitivity level.A total of 9 alfalfa varieties that showed intermediate resistance against both pathogenic bacteria,including Kangsai,Dayinhe,Adina,Babiao,Maguam 7,Jingxi,Baixu 202,Qishi T and WL169 HQ,accounted for The ratio was 28.13%.