First report of 'Candidatus Liberibacter asiaticus' associated with Hunglongbing in Fars province

 
 

 
Huanglongbing (HLB) also known as citrus greening is one of the most destructive disease of citrus worldwide. Three bacterial species including ‘Candidatus Liberibacter asiaticus’, ‘Ca. L. africanus’ and ‘Ca. L. americanus’ have been identified as causal agents associated with this disease (Bové 2006). ‘Ca. L. asiaticus’, agent of Asiatic form of the HLB disease has been previously reported in Sistan-Baluchistan, Hormozgan (Faghihi et al. 2008) and Kerman (Mohkami et al. 2012) provinces. Based on the presence of Asian citrus psyllid, vector of ‘Ca. L. asiaticus’ and exhibition of Huanglongbing-like symptoms including mottling of leaves and yellowing of shoots in citrus growing areas of Fars province, samples of psyllids and symptomatic citrus trees were tested for the presence of HLB using PCR assay. Direct PCR using F1/R1 primer pair and nested PCR using primer pairs F1/R1(first round) and F2/R2 (second round), specific for Asiatic form of HLB, resulted in amplification of expected fragments of 535 and 400 bp, respectively from six out of 14 psyllid and three out of 10 Lisbon lemon samples in Renjaco (Mohammadabad, Jahrom), 10 out of 14 psyllid samples in Dashte-peergheyb (Darab), five of eight Valencia sweet orange and three of five grapefruit samples in Tange Eij (Fasa) (Fig. 1). No amplicons were obtained from symptomless sweet orange trees and psyllid samples reared on healthy sweet orange seedlings. Direct PCR-amplified fragment from a psyllid and  a Lisbon lemon sample from Jahrom were directly sequenced and submitted In GenBank database under accession numbers KT626605 and KT626604 respectively, BLAST search using obtained sequences showed 99% identity with corresponding sequences of ‘Ca. L. asiaticus’ rplKAJL-rpoBC operon from Hormozgan province (GenBank accession number, FJ172759) and other areas in the world (GenBank accession numbers, M9439, AY34200 and EU078703). This is the first report on the occurrence of HLB disease in Fars province. HLB in Fars province is a serious threattocitrus productioninadjacent provinces