Skip to main content
ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #313786
Title: Reaction of detached leaves of different varieties of sweet orange (Citrus sinensis L. Osbeck) to inoculation with Xanthomonas citri subsp. citri

Author
item GONCALVES-ZULIANI, ALINE M. - University Of Maringa
item KERN, KATIA - University Of Maringa
item BELASQUE JR., JOSE - Universidad De Sao Paulo
item ZANUTTO, CARLOS - University Of Maringa
item HASHIGUTI, HERALDO - University Of Maringa
item Bock, Clive
item NAKAMURA, CELSO - University Of Maringa
item NUNES, WILLIAM M. - University Of Maringa

Submitted to: Summa Phytopathologica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2016
Publication Date: 4/1/2016
Citation: Goncalves-Zuliani, A.O., Kern, K.A., Belasque Jr., J., Zanutto, C.A., Hashiguti, H.T., Bock, C.H., Nakamura, C.V., Nunes, W.C. 2016. Reaction of detached leaves of different varieties of sweet orange (Citrus sinensis L. Osbeck) to inoculation with Xanthomonas citri subsp. citri. Summa Phytopathologica. 42:125-133.

Interpretive Summary: Citrus genotypes show a range of resistance to Asiatic citrus canker (ACC). The objective of this study was to evaluate a detached leaf method to compare citrus genotypes that exhibit a range of resistance to ACC, and to contrast infection, colonization and symptom development of the most resistant and most susceptible varieties using Scanning Electron Microscopy (SEM). The variety Pera IAC was the most resistant to the pathogen, and had lesions of the least diameter. The variety Washington navel was the most susceptible and had the largest lesions, indicating low resistance to Xcc. The observations from the SEM showed that Pera IAC had smaller stomatal openings and produced a greater quantity of foliar exudates compared with Washington navel. We hypothesize that the exudates may contain compounds toxic to Xcc and thus may be a defense mechanism to infection by Xcc.

Technical Abstract: Citrus genotypes show a range of resistance to infection with the plant-pathogenic bacterium, Xanthomonas citri subsp citri (Xcc), which causes Asiatic citrus canker (ACC). The objective of this study was to evaluate a detached leaf method to compare nine different citrus genotypes that exhibit a range of resistance to ACC, and to contrast infection, colonization and symptom development of the most resistant and most susceptible varieties using Scanning Electron Microscopy (SEM). Inoculation was by needle wounding with Xcc (108 CFU/ml). At 7, 10 and 13 days after inoculation (DAI), lesion diameters were measured. The variety Pera IAC was the most resistant to the pathogen, and had lesions of the least diameter (overall mean in the first and second experiments = 1.213 and 1.317, respectively). The variety Washington navel was the most susceptible and had the largest lesions (overall mean in the first and second experiments = 1.815 and 1.838, respectively), indicating low resistance to Xcc. SEM images were taken of lesion development, and sections were cut from the canker lesions of the most resistant variety Pera IAC and the most susceptible variety Washington navel at 3, 7 and 14 DAI. The observations from the SEM showed that Pera IAC had smaller stomatal openings and produced a greater quantity of foliar exudates compared with Washington navel. We hypothesize that the exudates may contain compounds toxic to Xcc and thus may be a defense mechanism to infection by Xcc.