The Study On The Pathogen Isolation And Identification, Pathogenicity Differentiation And Infection Process Of Sunflower Wilt

Sunflower wilt caused by Fusarium spp. is a kind of vascular disease,even leads to the whole plant dead. In 2013-2015, the sunflower diseases investigation was done in sunflower planting areas in China. Some wilt plants were founds in different locations and the disease incidence is variable. In this study, the diseased plants from different sunflower planting areas were chosen to identify their pathogen via Koch’s postulate. At the same time, the pathogenic differentiation of pathogens and the infection process in sunflower are also studied, and the results obtained are as follows:1.58 purified cultures were isolated from 28 different sunflower planting areas in 7 provinces, and identified as 12 species of Fusarium genus via morphological and molecular identification, they are F. oxysporum, F. verticilloides, F. lateritium, F. acuminatum, F. redolens, F. equiseti, F. proliferum, F. solani, F. tricinctum, F. cerealis, F. incarnatu and Plectosphaerella cucumerina.2. One representative strain randomly chosen from different species was used to perform biological characteristic study, including growth rate, sporulation, effect on growth of temperature and the pH, toxin production ability and pathogenicity. The results showed that different species of Fusarium has significant difference in the growth rate, sporulation, toxicity and pathogenicity.3. The study on pathogenicity differentiation of dominant species, results showed that Fusarium oxysporum and Fusarium proliferatum exist in pathogenicity differentiation phenomenon, but there is no host biotype differentiation.4. The evaluation of resistant level of different sunflower varities to F. proliferatum, the domiant species among all Fusarium spp., was performed under lab condition, the results showed that oil sunflower generally has higher resistance compared with confectional sunflower variety, and JK103 was the most resistant variety in all confectional sunflower varieties.5. We got the Fusarium proliferatum transformation labled with GFP by ATMT. The colony morphology, growth rate, spore germination rate, crude toxin content and pathogenicity of 8 randomly transformation were compared with the wild type strain, then choose the FP-4, which was not different from the wild strain, as a follow-up study on the infection process.6. Using FP-4 observed the infection process, we found that the the early stage of infection sites were in mature regions of the root and lateral root, and hyphae can extended in the cortex and vessels. Meanwhile, F. proliferum could infect the whole growth period of sunflower. We do obseve the GFP signals in roots, stems, petioles, leaf, subtending leaf, capsule, seed membrane and pollen.7. There was no significant difference in colonization ability of pathogenic in the roots of the resistant and susceptiable varietie during the initial stage of infection. However,21dpi, GFP signal do observe in root, stem and leaf of susceptiable variety, and the green signal only observed in root and stem of resistant varieties. Q-PCR results is also match with the results observed under flurescence microscopy, the pathogen colonized more dense in different tissues of susceptiable variety than that in resistant variety.