Pathogen Identification Of Bulb Rot Disease In Edible Lily(Lilium Brownie Var. Viridulum) And Toxicity Determination Of Fungicides In Laboratory

Bulb rot disease is a destructive disease of edible lily(Lilium brownie var. viridulum cv. Longya) in Longhui county, Hunan province. This disease occurs on the bulbs at late growth stage with the typical symptom of browning and rot emerged on the whole bulbs, and the whole plant would wither. On this paper, the isolation and identification of the pathogen, biological characteristics and fungicides toxicity determination in laboratory was studied systematically. The main results are as follows.1. Identification PathogenEight fungi and six bacteria strains were isolated from the rot bolb. After a needle-pricking inoculation with isolate HNLH07on healthy lily scales, rot symptom was reproduced while the other strains caused no symptoms. The isolated fungus HNLH07on potato dextrose agar (PDA) media developed white mycelium. The shape of microconidia and macronidia were oval and sickles-shaped, respectively. PCR amplification was carried out by using universal rDNA-ITS primers. Sequence of PCR product showed99%identity with those of F. oxysporum by BLAST in NCBI. Phylogenetic analysis showed that HNLH07(No. JQ316463) was clustered with F.oxysporum with a high bootstrap value of99%. HNLH07failed to infect bulbs of gladiolus or tulip in a same inoculation test. It comes to a conclusion that the pathogen causing bulb rot of cv. Longya in Longhui county should be F. oxysporum f.sp. lilii.2. Biological CharacteristicsThe research of Biological characteristics of F. oxysporum f.sp. lilii showed that the optimum pH for conidial production and mycelium growth was between pH4to12. For mycelium growth, the optimum pH was5. For conidial production,the optimum pH was6. For mycelial growth,the range of temperature was25-31℃and the optimum temperature was28℃For conidial production, the range of temperature was31-35℃and the optimum was34℃.The lethal temperature of conidial was52℃for10min. For the mycelial growth and optimum medium for conidial production on solid media, the optimum carbon source was fructose. For the mycelial growth,the optimum nitrogen source was D-Aspartic acid. For conidial production, the optimum nitrogen source was KNO3.3. Fungicides Toxicity Determination in Laboratory Thirteen kinds of fungicides against F. oxysporum f.sp. lilii were tested by means of mycelial growth rate method, respectively. The results showed that diniconazole, difenoconazole, myclobutanil-thirm, hexaconazole and zhongshengmycin had a good inhibition against the fungus.It is an important innovation of this study that Lily Wilt is actually caused by bulb rot and its pathogen is Eoxysporum f.sp. lilii.