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Title: MOLECULAR IDENTIFICATION AND CLASSIFICATION OF STRAWBERRY PHYLLOID FRUIT PHYTOPLASIMA IN STRAWBERRY

Author
item JOMAUTIENE, RASA - MISC
item Maas, John
item TAKEDA, F - ARS-KEARNEYSVILLE
item DAVIS, ROBERT - MPPL,BARC

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: Phytoplasmas are bacteria-like organisms that infect many plants and often cause serious crop losses. Strawberry plants also can be infected with phytoplasmas, causing fruit losses as well as plant death. It has been only recently that research has focused on identifying and characterizing phytoplasmas from commercial strawberry and associating their presence with disease symptoms. One characteristic symptom of phytoplasma infection is deformation of fruit, called phyllody, in which leafy growths develop from the fruit. Often this symptom is followed by plant decline and death. Several plants in a winter greenhouse production facility in West Virginia produced fruit with extensive fruit phyllody. These fruit were found to be infected by a new phytoplasma, which we named STRAWBPhF phytoplasma. This organism is closely related to, but distinct from, other phytoplasmas infecting strawberry. The information developed here will benefit plant disease researchers who are concerned with phytoplasma diseases of plants and the evolution of phytoplasmas in general.

Technical Abstract: Plants of commercial strawberry (Fragaria x ananassa Duch., cv. Camarosa) that exhibited extensive fruit phyllody were observed in a winter greenhouse production facility in West Virginia. These fruit were assessed for phytoplasma infection by use of the nested polymerase chain reaction and reamplification of phytoplasma 16S ribosomal (r) DNA (16S rRNA gene) sequences. Phytoplasma-characteristic 1.2 kbp DNA sequences were amplified from diseased tissues. Restriction fragment length polymorphism (RFLP) patterns of rDNA digested with AluI, KpnI, HhaI, HaeIII, HpaII, MseI, RsaI, and Sau3A1 endonucleases indicated that the phylloid plants were infected by a phytoplasma (STRAWBPhF phytoplasma) that belonged to group 16SrI (group I, aster yellows phytoplasma group). The collective RFLP patterns of STRAWBPhF 16S rDNA differed from that of the apparently close relative in group I, clover phyllody (CPh) phytoplasma. The STRAWBPhF phytoplasma 1.2 kbp DNA product of PCR primed by primer pair F2n/R2 was sequenced, and the sequence deposited in GenBank under Accession No. AY102275. STRAWBPhF 16S rDNA shared 99.9% sequence similarity with CPh operon rrnA and 99.8 with CPh operon rrnB. STRAWBPhF 16S rDNA sequence differed from CPh operon rrnA by a single base substitution. STRAWBPhF 16S rDNA differed from CPh operon rrnB in three restriction sites with MseI, HaeIII, and AluI in RFLP analyses, and in three base substitutions. There was no evidence for the presence in STRAWBPhF phytoplasma of a second rRNA operon similar to rrnB described in CPh phytoplasma. Due to the unique RFLP patterns of STRAWBPhF phytoplasma rDNA, we are required by current convention to classify this phytoplasma in a separate subgroup (i.e., I-R), although STRAWBPhF and CPh phytoplasmas apparently are closely related to one another. STRAWBPhF phytoplasma is identical to Cirsium yellows phytoplasma (GenBank Accession No. AF200431) reported, but phylogenetically unclassified, from Lithuania in Cirsium arvense L.. Future studies on STRAWBPhF phytoplasma may provide important information on the evolution of phytoplasmas.