Studies On Identification And Infection Routes Of Fusarium Solani F. Sp. Cucurbitae

Grafting technology has been considered as an effective method of controling soil-borne diseases on cucumber. In recent years, as the cultivated area of grafted cucumber increasing,the plants has appeared to die off, which is caused by soil-borne diseases. Symptoms and pathogens of the disease seem to be complex which are still confused. Therefore, a preliminary study has been made on the pathogens of grafted cucumber seedlings diseases and the pathogenic differentiation of the pathogens in view of the problems of confusion with the pathogens, inaccurate diagnosis and control of the grafted cucumber seedlings diseases.The main achievements are:1.For the first time in China, the pathogens and symptoms of grafted cucumber seedlings diseases were clarified. Based on the pathogenicity tests, morphological characters and molecular biological methods, the [Fusarium solani (Mart.) Sacc.] was determined as the pathogen of grafted cucumber seedlings diseases. Colony appeared little aerial mycelia and a cream color on the reverse side.With of the 3-sept and 5-sept macroconidia were less than 5μm. The symptoms consisted of dark brown, water-soaked lesions and a dense white mycelial mat formed at the base of the stem. Serious symptoms appeared falling over without wilting.Crown was more seriously infected and root seemed to be healthy. In summary, the symptoms was determined as crown rot of grafted cucumber.2.By the pathogenicity tests of differential hosts, for the first time in China,the pathogens were identified as Fusarium solani f. sp. cucurbitae Snyder & Hansen. According to the foreign researches,11 isolats were inoculated on 14 differential hosts to conduct the pathogenicity test.With the same results of the foreign researches, 8 cucurbits differential hosts were infected,while 6 other differential hosts were healthy.Therefore, 11 isolates were identified as Fusarium solani f. sp. cucurbitae.3.The infection routes and influences on seeds of the Fusarium solani f. sp. cucurbitae was determined.Infected seeds were collected from inoculated fruit of pumpkin. Germination rate of infected seeds was declined.By isolation of stem, crown, root collected from the infected plants, Fusarium solani f. sp. cucurbitae was isolated only from the inoculated tissues ,which did not infect the whole plant, not the same as Fusarium oxysporum.4.Inoculated method for screening resistant rootstocks was clarified. By using soil mixed with pathogens to perform pathogenicity tests ,1 HR and 1 MR cultivars were collected.This study identified the seedling disease of grated cucumber as crown rot caused by Fusarium solani f. sp. cucurbitae for the first time in China, providing theoretical basis for diagnosis and control of the grafted cucumber seedlings diseases.