Detection Of Citrus Bacterial Canker Disease By Real Time - PCR

Citrus bacterial canker Disease (CBCD), caused by Xanthomonas axonopodis pv. citri (Xac), is a serious disease of most citrus species and cultivars in many citrus-producing areas in the world. More than 30 countries and areas worldwide which produce citrus have suffered from CBCD including Asia, Mideast, Africa, the islands in Pacific and Indian Ocean, Australia, South America and the southwest of America. In China, this disease is mainly distributed in the south provinces such as Fujian, Guangdong, Guangxi, Jiangxi, Zhejiang, Hunan, Hubei, Yunan, Guilin, Sichuan and so on. Most commercial cultivars can be infected by Xac. The host plants are barely put to death directly, but they will suffer defoliation, fruit-fall, vitality decline and lesion on the fruits which greatly degrades the quality and economic value of the fruits.For the lack of resistant cultivars and specific chemicals, the following measures have been adopted to control CBCD for a long time: enhanced construction of non-quarantine area and phytosanitary system against the spread of Xac, eradication and mass destruction methods dealing with infected plants. A fast and robust method for diagnostic and detective purpose is badly needed to support the monitoring of non-quarantine area construction and custom detection system for citrus materials.Traditionally, the conventional detection methods for CBCD include identification based on typical symptoms, pathogen cultivation and pathogenicity detection. Besides, phage detection, enzyme-linked immunosorbent assay (ELISA) and dot immunobinding assay (DIA) are also used for detection. These methods above are all time-consuming, complex and less sensitive in a certain extent, which can not fulfill the requirements of quarantine adequately.With the great development of biotechnology especially the DNA recombination technology, the genes relative to the pathogenecity have been identified and cloned constantly which makes the diagnostics for plant disease come into the molecular level. Molecular detection methods are characterized by speediness, specificity and sensitivity, which can meet the requirements of modern phytosanitation. As an important quarantine pathogen, the rapid detection technologies for Xac have also made great progress in recent years, like DNA hybridization, DNA fingerprint map analysis and polymerase chain reaction (PCR) detection method. Real time fluorescent PCR (RTi-PCR) is a new-emerging molecular technology. In contrast to conventional PCR, RTi-PCR has higher sensitivity and specificity; it does not need gel electrophoresis analysis which...