NC State Extension Publications

Introduction, Symptoms and the Pathogen

Phytoplasmas are organisms that multiply in the phloem of strawberry plants and are carried from plant-to-plant by leaf hoppers (vectors). The disease occurs at very low levels in annual fruit production systems and infected plants are associated with plant source. First symptoms observed include plant stunting and the development of multiple crowns (Figure SS-1; Figure SS-2). The pathogen can also cause plants to grow oddly – leaves may grow from fruit (phyllody; Figure SS-3). Levels are so low that control recommendations are not warranted. It is not important to remove these plants in annual systems since disease spread does not occur within the field in during the production cycle. These pathogens are easily transmitted through tissue culture and any vegetative propagation program. Therefore, it is essential that plants in a certification program be evaluated to ensure they are phytoplasma free. This can be accomplished using the polymerase chain reaction (PCR). Protocols have been established for isolation of DNA from plants, including DNA from pathogens such as the phytoplasmas. The DNA is amplified using PCR and then the DNA is visualized using agarose gel electrophoresis. DNA methods are also used to identify the genotypes of the pathogen.

Phytoplasma in the field

Figure SS-1: Plants showing a distinct stunting compared to non-infected plants. These plants have multiple crowns and small leaves.

Frank J. Louws

Phytoplasma in pots

Figure SS-2: Plants showing a distinct stunting and compressed growth. These plants were harvested form the field in late winter.

Frank J. Louws

Phytoplasma phyllody

Figure SS-3: Odd growth of leaves from strawberry fruit (phyllody).

Frank J. Louws

Author:

Director NSF Center for IPM; Professor Plant Pathology
Plant Pathology

Publication date: July 24, 2014

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