Phytoplasma identification in pome fruit trees and Cacopsylla bidens (Hemiptera: Psyllidae) in Jordan

During field surveys conducted in 2021 in western Jordanian heights, phytoplasma-like symptoms were observed, including leaf reddening along with slow decline in pear (pear decline symptoms) and leaf yellowing followed by scorch in apple trees. Abundant populations of the psyllid Cacopsylla bidens were found in the pear trees. Nested PCR amplifying 16S rDNA detected phytoplasmas in 63% and 36% of symptomatic pear and apple samples, respectively, and in 46% of pooled C. bidens specimens. No phytoplasmas were detected in symptomless plant samples. PCR product nucleotide sequence analyses attributed the phytoplasmas detected in pear to 'Candidatus Phytoplasma pyri', 'Ca. P. solani', 'Ca. P. omanense', and 'Ca. P. aurantifolia', and those identified in apple to 'Ca. P. solani' and 'Ca. P. omanense'. All phytoplasma strains identified in C. bidens were attributed to 'Ca. P. pyri'. To the best of our knowledge, this is the first report of phytoplasmas associated with pear and apple diseases, including pear decline, in Jordan. Even though a limited number of pome fruit samples were analyzed, a surprising diversity was found among detected phytoplasmas. Further studies will be carried out to investigate the complex etiology of such diseases, and the 'Ca. P. pyri' vectoring activity of C. bidens.