|Legard, D - UNIV OF FL GREC DOVER FL|
Submitted to: Acta Horticulture Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 17, 1997
Publication Date: N/A
Interpretive Summary: Phytoplasmas (tiny wall-less bacteria) cause many plant diseases, reducing product quality, hindering exports, and reducing farmer profits in fruit crops including strawberry. Previously, we demonstrated that F. multicipita, a rare plant species from Canada, is in reality a phytoplasma-diseased strawberry. Analyses of 16S rDNA indicated that the F. multicipita phytoplasma belonged to 16S rRNA group 16SrVI and was closely related to, but differed from, group VI member clover proliferation (CP) phytoplasma reported in Canada. In this paper, we report that another group VI phytoplasma was associated with symptoms of strawberry multiplier disease in winter production fields in Florida. We concluded that the multiplier-associated group VI and the "F. multicipita" phytoplasmas were closely related to each other and to CP phytoplasma. The findings indicate a possible link between these phytoplasmas. Such a link may be an evolutionary/taxonomic one. At present, there is no evidence of an epidemiological link between the phytoplasmas in Canada and strawberry disease in Florida. The results provide pathogen targets for managing quarantined plant germplasm and a basis for investigating possible epidemiological as well as evolutionary links between the phytoplasmas and strawberry diseases, and for assessing whether the "F. multicipita" phytoplasma and/or CP phytoplasma could not present a threat to cultivated strawberry. The findings will be of interest to diagnostic companies, APHIS, and strawberry growers.
Technical Abstract: The rare plant taxon, "Fragaria multicipita" Fernald, is characterized by dwarfing, a cushion-like growth habit with multiple crowns, lack of runners, and development of floral aberrations. Through the use of polymerase chain reaction (PCR)-RFLP based analyses of 16S rRNA gene sequences, we found the unusual, but species diagnostic, vegetative morphology of F. multicipita to be associated with a previously undescribed phytoplasma that is capable of inducing the same vegetative morphotype in healthy strawberry plants (F. chiloensis) grafted with tissues from F. multicipita. Analyses of 16S rDNA indicated that the F. multicipita phytoplasma was closely phylogenetically related to clover proliferation (CP) phytoplasma reported in Canada. During simultaneous investigations of a strawberry disease problem in winter production fields in Florida, we found that another previously undescribed phytoplasma (strains Flmulti1 and Flmulti2) was associated with symptoms of strawberry multiplier disease. On the basis of RFLP anaylsis of PCR-amplified 16S rDNA, we concluded that the F. multicipita phytoplasma and phytoplasma strains Flmulti1 and Flmulti2 were phylogenetically closely related to one another and to CP phytoplasma. These findings indicate a possible link between two phytoplasmas (CP and "F. multicipita" phytoplasmas) found in Canada and a phytoplasma (strains Flmulti1 and Flmulti2) found in diseased strawberry plants in Florida, but it is important to note that such a link may be an evolutionary/taxonomic one. At present, there is no evidence that this link is an epidemiological one.