SUMMARY

The thesis “Identification of virus belong to Begomovirus genus infected Tomato yellow leaf curl disease (TYLCD) in Lam Dong province” was carried out from April 2009 to December 2010 at the Department of Biotechnology, Institute of Agricultural Sciences for Southern Vietnam. The aims of the study were to identify the virus belong to Begomovirus genus which infect yellow leaf curl disease on tomato in Lam Dong province.

The survey of TYLCD infection was conducted on 200 samples of tomato leaves from 40 tomato small households in Lam Dong province, of which there were 34 households in Don Duong district and six households in Duc Trong district. Each household provided five samples of tomato leaves to the survey.

Results of the study showed that ten samples of tomato plant leaves appeared yellow leaf curl disease, accounting for 5%.  

DNA of these samples was extracted by applying Doyle and Doyle (1999) methods which were suitably adjusted to favorable conditions of the study. The extracted result was satisfactory with the purity of DNA (OD 260/280 ratio at 1,72).

The study designed two sets of primers to amplify two DNA fragments into the CP and Ren gene. The set of primer TYLC-F1/TYLC-R1 amplified DNA fragments with size 750 bp and the set of primer TYLC-F2/TYLC-R2 amplified DNA fragments with size 512 bp.

The Tomato yellow leaf curl disease was identified by PCR protocol. The first one was optimized the temperature of annealing at 53⁰C for 45 seconds and the 0,4 μM of primer with the set of primer TYLC-F1/TYLC-R1 and the second one was optimized the temperature of annealing at 52⁰C in 30 seconds and 0,4 μM of primer with the set of primer TYLC-F2/TYLC-R2.

Among 200 samples tested by PCR, 30 samples were positive for Begomovirus, occupied of 15%. This result indicates that PCR technique have a higher exact level than clinical symptoms method in detection of TYLC disease.

Two positive samples for Begomovirus corresponding to each set of primer were selected to sequence. The sequencing results were used to analyze the genetic characteristics of virus. Homologous nucleotide sequence and phylogenetic tree of colleted samples, and 17 strains which represented ten Begomovirus species related to TYLCD were performed by using BioEdit, DNAstar and MEGA 4.1 softwares.

The results revealed that nucleotide sequence identity between the collected isolate and the identified strains (in Vietnam) was 75% - 99%, and the strains in the world rank from 68% to 94%. Of these, the studied sample was closely to trains of TYLCKaV species which appeared in Thailand and Vietnam with nucleotide sequence similarity ranging from 94% to 99%.