| Tomato(Lycopersicon esculentum Mill.)is an annual and perennial plants of Solanaceae.It is native to South America and widely cultivated in China.However,the diseases have increased with the extension of the cultivation period,especially the root rot disease,which has become one of the main factors in hindering the development of the tomato industry.In this study,the pathogen(Fusarium)of tomato root rot disease was studied including the analysis of pathogenicity,the screening of fungicides,and the selection of disease-resistant seeds.The aim of this research is to provide a theoretical basis for prevention and control measures of the tomato root rot disease.Meanwhile,we focused on the screening of the disease-resistant varieties.The research mainly included the following aspects:1.In 2016,the root rot diseases of tomato seedlings and adult plants in Northwest China(Qinghai,Xinjiang,Ningxia,Gansu)were investigated.It was found that the root rot disease caused by Fusarium was common,with an average incidence rate of 5%-20%.A total of 106 tomato root rot samples were obtained by multi-point sampling.2.According to the symptoms and isolated pathogens,combined with the research of tomato diseases,the identified tomato root rot diseases were divided into two kinds: the tomato crown root rot and the tomato Fusarium foot rot.The symptom of crown root rot mainly manifested the browning of the base of stem and root,the drying of skin.The old leaves became yellow and fall off.Near the ground portion,there are brown rot and the stem lesions often surrounds a circle.And part of the plant was enveloped with visible white mold layer.The stem of seedlings was constricted,and the vascular bundle browned in longitudinal section,meanwhile,the phloem necrosed.At worst,the plant wilted.Tomato Fusarium foot rot could cause red or brown speck in taproots or large secondary roots,and the cortex discolored at lesions of the roots.There are chloasma in the veins of leaves,and the leaves became white.At worst,the shoots brown,and the plant withered.3.The isolation and purification of the fungus were based on the methods of tissue separation and single spore separation,seperately.The pathogenicity was analyzed according to the Koch’s law.The fungi was identified based on the characteristics of morphological colony and molecular biological.The results showed that Fusarium oxysporum was the tomato crown and root rot dominant pathogens,the Fusarium solani was the Fusarium foot rot dominant pathogens.4.The study of the pathogenicity on the pathogen of tomato root rot disease showed that the pathogenicity between the same strains was quite different.The pathogenicity of strains determined by the beaker water agar method was higher than that of strains determined by the plotting method,and the difference was significant.However,the correlation analysis showed that the pathogenicity measured by the two methods was extremely significantly correlated.Thus,it is indicated that the trends of morbidity and pathogenicity measured by the two methods are consistent.5.In total,33 domestic and foreign tomato varieties planted in large areas in China were screened for disease resistance varieties with the pot culture method.The results showed that among the 33 tomato varieties,no varieties that were immunized against the two diseases.Most varieties were characterized by susceptible varieties or medium sensations.Four disease-resistant varieties were selected including Taiwan Fenyunv,Jingpin Hongmeinv,Hua Xiuqiu and Yuanming Fenyunv.6.We screened seven chemical fungicides and measured their toxicity in the lab by inhibitory method of dishhyphae.The results showed that all the seven chemical agents have certain effects on the two kinds of diseases.Moreover,with the increase of the concentration of the drug,the inhibition rate was also strengthened.Thus,the concentration of the drug is positively correlated with the inhibition rate.screened out riazolidone was good control effect Chemicals. |
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