Title: Effective Assessment of RNA Extraction Methods for Diagnosis of Tristeza Disease on Citrus and Investigation of Disease Incidence in King Mandarin Nurseries of Mekong Delta

Abstract
Citrus tristeza virus (CTV) is the important disease on citrus. The study was carried out to find an
effective total RNA extraction method for RT-PCR In the identification of CTV and investigation of CTV
incidence in King mandarin nurseries of Mekong Delta. Firstly, a comparison of different RNA extraction
methods (i.e. NEXprepTM, RCTAB, SDS-P:C, TRIzolTM) on leaf symptoms caused by CTV. The results
found that the Rapid-CTAB method is the best effective method, and equivalent to the standard TRIzolTM reagent. Secondly, evaluation disease incidence of CTV in 10 King mandarin seedling nurseries from Long Ho District, Vinh Long Province, and Cho Lach District, Ben Tre Province. Interestingly and seriously, the results showed that all of the 30 surveyed seedlings were positive for CTV (100%) by RT-PCR analysis with T36CPR/T36CPF specialized primer pairs. The finding indicated that the control strategy of Tristeza disease of citrus cultivation in Mekong Delta of Vietnam should be considered.

Keywords: Citrus tristeza virus, citrus seedling, nurseries, disease incidence, RT-PCR, RNA extraction