Japan International Research Center for Agricultural Sciences (JIRCAS)
Abstract
Citrus trees affected by greening (huanglongbing, HLB)often develop symptoms that resemble those of Zn or Fe deficiency in their leaves. However, there have been few studies of mineral concentrations in infected leaves. To examine the effects of infection by ‘Candidatus Liberibacter asiaticus’ (the causal organism of the Asiatic form of HLB) on mineral nutrition, Citrus jambhiri ( Lush.), C. reticulata cv.Siem,
and C.depressa Hayata were patch-grafted with infected bark
squares and grown in pots in greenhouses in Japan and Indonesia. In addition, leaves were collected from field-grown C.tankan Hayata and C. unshiu Marc. in Japan and
C.reticulata cv.Siem in Indonesia, and their disease status
was determined by PCR.Leaf samples were homogenized in
2-(N-morpholino)ethanesulfonic acid buffer and the concentrations of water-soluble Cu,Fe,Mn,and Zn in the macerate were determined using inductively coupled plasma
atomic emission spectrometry (Japan)or atomic absorption spectrometry (Indonesia).In general, infected leaf samples
had lower Fe and Zn. On average,the concentrations of Fe
and Zn in infected plants were approximately half those in
healthy plants. Cu was not significantly reduced by infection and Mn was occasionally lower. In C.unshiu, the
concentrations of Fe and Zn were reduced before chlorosis
appeared. These results suggested that the concentrations
of particular elements (Fe and Zn) rather than element concentrations in general are reduced by infection by ‘Candidatus Liberibacter asiaticus’. Discipline: Plant disease Additional key words: Citrus depressa, Citrus greening, Huanglongbing, Liberibacte