Isolation and identification of bacteria associated with Guava decline in Egypt

Guava (Psidium guajava Linn.) is one of the most popular fruits in Egypt. Guava decline is thought to be a complex disease prevailing in tropical and subtropical regions. Several studies were completed on the role of fungi and nematode in the deterioration of guava. There is unsatisfactory information on the involvement of bacteria in this disease. In the present work, twelve isolates of bacteria were recovered from diseased guava trees at Rashid territory of El-Behera government in Egypt. The results of 16S rRNA gene sequences compared with the sequences of the Gen Bank DNA database showed that eight of these isolates belong to family Enterobacteriaceae, two isolates belong to family Rhizobiaceae and two isolates belong to family Pseudomonadaceae. The Pectobacterium aroidearum is the only species that has shown a positive result with a hypersensitive reaction (HR) test. Agrobacterium salinitolerans was the only species able to form small tumors in squash fruits. No evidence of formed hyperplastic syndrome on the tomato plants by Agrobacterium salinitolerans or any of these isolated bacteria were recognized. Potato soft rot test confirmed that only Pectobacterium aroidearum have the potential to cause soft rot in potato slices. The results indicate that, despite difference in pathogen propensities, Pectobacterium aroidearum and Agrobacterium salinitolerans can get involved in guava decline syndromes either single or in combination, bearing in mind the role of other pathogens such as fungi and nematodes. Further studies are needed. [A.F. Abd El-Rahman, Naglaa M. Balabel and Rabab, M. Abd -El–Aziz. Isolation and identification of bacteria associated with Guava decline in Egypt. J Am Sci 2020;16(3):51-62]. ISSN 1545-1003 (print); ISSN 2375-7264 (online). http://www.jofamericanscience.org. 7. doi: 10.7537/marsjas160320.07.