Submitted to: Dekker Encyclopedia of Plant and Crop Science
Publication Type: Other
Publication Acceptance Date: 10/23/2003
Publication Date: 6/1/2004
Citation: Lee, I., Klopmeyer, M., Gundersen, D.E. 2004. Beneficial phytoplasma infection of poinsettia causing free-branching. Dekker Encyclopedia of Plant and Crop Science. Available:http//www.dekker.com/servlet/product/productid/E.
Interpretive Summary: This is a book chapter.
Technical Abstract: Free-branching poinsettia cultivars that produce numerous axillary shoots are essential for propagating desirable multi-flowered potted poinsettias and comprise the majority of commercial cultivars propagated today. Many free-branching cultivars (>100) have been developed and propagated commercially in the last decade. In the United Sates poinsettias are one of the most economicaly important floricultural crops. Over 65 million plants were sold in the US alone in 2000. The branching factor has been a mystery to horticulturists for decades. Recent evidence has indicated that the poinsettia branching factor is a graft-transmissible biological agent. Using PCR and DNA finger printing (RFLP analysis) diagnostic procedures we have provided evidence indicating that the self-branching ability of the majority of commercial free-branching cultivars of today is not due to genetic traits selected through breeding but by the grafting of new seedlings (phytoplasma-free) to a free-branching rootstock that contains phytoplasma. The presence of phytoplasma causes the induction of free-branching in these infected poinsettias. This is the first reported example of a pathogenic phytoplasma as the causal agent of a desirable and economically important trait.