Study On Tomato Yellow Leaf Curl Virus In Shanghai Area

Tomato (Lycopersicon esculentum Miller) is a warm-season plant which belongs to Lycopersicon genus of Solanaceous and originated from Ecuador and Peru. It be cultiated extensively all around the word because of its wide adaptability, it has excellent taste and high nourishment value. Tomato yellow leaf curl virus(TYLCV),transmitted by the whitefly Bemisia tabaci, is one of the most severe diseases of tomato, which causes economic losses up to 100% in tomato crop in many tropical and subtropical regions. Recent years, this disease expanded to almost all the world with increasing seriousness. So we must find a feasible and effective method to solve this problem. Disease-resistant breeding is the most effective and direct method to deal with disease up to now. This study first began with the detection of TYLCV in tomato, and found a convenient artifical inoculation method to detect TYLCV at seedling stage. Then 24 tomato varieties provided by tomato breeding laboratory of Horticultural Research Institute in Shanghai Academy of Agricultural Science were appraised in resistance to TYLCV use this method. And we set up molecular markers linked to resistant genes. These lay a foundation for tomato yellow leaf curl virus breeding. The results were as follow:1 Based on the conserved regions of the reported nucleotide sequences of whitefly- transmitted geminiviruses (WTGV), a pair of primers was designed to anneal to the conserved sequence. The tomato samples infected geminivirus-like from Shanghai were detected by PCR. A 575bp specific fragment was amplified from the samples. The specific fragment was cloned and sequenced, and the sequence was compared with all nucleotide sequences in GenBank by Blast of NCBI. The result showed that the fragment belonged to tomato yellow leaf curl virus DNA.。 2 The methods using whitefly-mediated inoculation and graft inoculation to screening tomato seedling resistant to TYLCV were set up. Then 24 tomato varieties were appraised in resistance to TYLCV by whitefly- mediated inoculation. The result indicated that there were 3 immune materials, 11 resistant varieties, which lay a foundation for tomato yellow leaf curl virus breeding.3 The molecular markers linked to the tomato yellow leaf curl virus resistant genes were isolated from 12 RAPD primers in resistance and susceptible materials. A RAPD marker 697 was obtained.4 Molecular marker-assisted selection systems of Ty-1 genes,Mi genes,Cf-5 genes,Tm22 genes were established. Mutiplex-CAPS reaction two genes system were developed, including Ty-1 gene and Mi gene, Ty-1 gene and Cf-5 gene, Ty-1 gene and Tm22 gene. The PCR products were almost completely correspond to the amplified bands produced by single CAPS primer, proving that two resistant genes could be identified simultaneously by using corresponding CAPS primer under advisable condition.