Identification Of Pathogen Causing Root Rot Of Lagenaria Siceraria And Screening Of Lagenaria Siceraria Germplasm Sources Resistance To Root Rot

In recent years, the root rot of gourd is widespread in Ningbo areas.The disease is getting worseyear after year. The root rot pathogen from Lagenaria siceraria planted in Ningbo county were studiedin the Paper, and identified it with molecular method, assessed the resistance of Lagenaria sicerariaseeds which were bred in Ningbo Institute of Academy of Agricultural Sciences of Vegetable,meanwhile the indoor toxicities of seven chemical fungicides on pathogen of Lagenaria siceraria rootrot were also determined, the results were showed as follows:1、 Pathogenicity determination: soil mixed with pathogen, immersing-root inoculation andtoothpick inoculation were used to inoculate the pathogen to the root of healthy gourd seedlings, theseedlings showed typical symptoms of root rot, the result of molecular identification of the isolatedpathogen exhibit was consistent with the former isolate. And the symptoms were also the same after beinoculated. In these methods, soil mixed with pathogen showed the best in efficient and pathogeniceffects, and it was chosen for selecting resistant germplasm screening. Through running nucleotide Blastwith one of the NCBI tools using TEF1-αsequences, we found a significant sequence homology as highas100%between the pathogen and Fusarium.solani. According to the TEF1-α sequence analysis, theoriginal Lagenaria siceraria root rot fungi was confirmed to be F. solani.2、Pathogen biological characteristics showed that: the pathogen could grow in a wide range ofpH4-pH10.In weak alkaline pH conditions, it grew faster than other pH conditions. But when close toneutral pH conditions, the sporulation got to the largest proportion. In the light conditions, it got to thefastest growth rate, while in dark got more sporulation. The best carbon source for mycelium growthwas glucose, and the optimum nitrogen source was potassium nitrate, the optimum carbon and nitrogensources of sporulation were also glucose and potassium nitrate. The mycelium lethal temperature was56°C.3、The toxicity determination of fungicides to the pathogen:7fungicides in the set under differentconcentrations showed a certain inhibitory effect on the growth of the pathogen. But the inhibition effectof fungicides to pathogen had difference, in which EC50of Thiophanate, Oxadixyl MZ, HymexazolIsoprothiolane, Chlorothalnil, Urea cream MZ, Carbendazim and PCNB carbendazim for F.solani were21.98,119.87,406.06,8.30,37.78,1.99,4.47μg/mL respectively. The inhibition effect of Carbendazimdemonstrated the strongest place, the average inhibition rate was69.43%; PCNB carbendazim tooksecond, the average inhibition rate reached48.85%, while Hymexazol Isoprothiolane was the weakestone, the average inhibition rate was25.34%only. The correlation coefficient of7kinds of fungicideswas above0.95. And positive correlation was found between fungicide concentration and inhibitioneffect.4、Resistance results of gourd varieties shows that: the resistant to Fusarium solani existeddifferential among gourd varieties, but lacked high-resistant varieties in present. There were only twomoderate-resistance materials in the all disease-resistant gourd materials. They are10A-2and12A-16,others were mid-susceptible or susceptible materials.