Vol 127 (2014): Proceedings of the Florida State Horticultural Society
Handling & Processing

Huanglongbing increases diplodia stem end rot in Citrus sinensis

Wei Zhao
USDA-ARS
Jinhe Bai
USDA-ARS
Greg McCollum
USDA-ARS
Elizabeth A. Baldwin
USDA-ARS
2014 Proceedings Florida State Horticultural Society Volume 127
Published March 15, 2018

Abstract

Huanglongbing (HLB), one of the most devastating diseases of citrus is caused by the α-Proteobacteria Candidatus Liberibacter. Diplodia natalensis Pole-Evans is a fungal pathogen which has been known to cause a postharvest stem-end rot of citrus, the pathogen infects citrus fruit under the calyx, and the fruit decay typically occurs following harvest and is exacerbated by exposure to ethylene. In this study, we report that high incidence of Diplodia infection in HLB symptomatic fruit. The incidence of SER in 300 ʻHamlinʼ and 300 ʻValenciaʼ orange fruit, with or without ethylene treatment was determined. Two weeks following exposure to ethylene (10 ppm, four days), the incidence of SER in HLB-symptomatic fruit was as high as 66.7% (ʻHamlinʼ) and 58.7% (ʻValenciaʼ); whereas for asymptomatic fruit, less than 10% of the fruit were affected by SER. Confirmation of Diplodia in calyx abscission zone was by qPCR validation of the isolates and morphology of conidia.