Correction to: Sensitive detection, quantification, and monitoring of Erwinia psidii colonization of guava plants using intercalating dye-based real-time PCR

Bacterial blight caused by Erwinia psidii is considered an important disease of the guava crop in Brazil. The disease has been disseminated to different geographic areas due to the movement of infected but asymptomatic propagating plant material. Consequently, methods showing high specificity and sensitivity for early detection of latent infections are required to aid in the establishment of the use of pathogen-free seedlings and propagating material. In this study, an intercalating dye-based real-time PCR (qPCR) method using newly designed species-specific primers targeting the recA gene sequence was developed. Primer specificity was first confirmed in silico and then by PCR amplification using DNA from strains of a collection of E. psidii and other plant-associated bacterial species. DNA from strains of other bacterial species obtained from uninfected guava and eucalypt leaves or from other plant species were not amplified. When bacterial suspensions and purified DNA were used in qPCR, detection limits were 10(3) CFU mL(-1) and 10(2) genomic units mu L-1, respectively. Using qPCR, E. psidii was detected in 100% of samples from symptomatic and in 57.1% of samples from asymptomatic trees collected in four guava orchards. The qPCR method allowed quantification of E. psidii populations in infected tissue of varieties Pedro Sato and Sassaoka as well as confirmation of the previously reported E. psidii acropetal and basipetal movement inside the plant. This new detection method with improved sensitivity has great potential not only for implementing disease diagnosis in guava and eucalypt nurseries and orchards but also for investigating relevant aspects of E. psidii life cycle and epidemiology.