Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/12/2007
Publication Date: 4/1/2007
Citation: Lee, I., Bottner, K.D., Black, M.C. 2007. First report of Yucca phyllody associated with 16SrI-A phytoplasmas in the U.S. Plant Disease. 91:467. Interpretive Summary: Phytoplasmas are unusual bacteria that lack a cell wall and cause several hundred economically important diseases in plants worldwide. A phytoplasma causing severe yellows disease in China aster is termed aster yellows phytoplasma. This phytoplasma and closely related strains represent the most diverse phytoplasma group and cause more than 100 diseases in diverse plant species including ornamental, vegetable, grain, fruit, and forest crops. The aster yellows group phytoplasmas have been classified into more than 20 subgroups. Subgroup A and B are most commonly present in the US. This year, a new disease occurred in yucca, a popular flowering plant, in southwestern Texas. The infected plant had abnormal buds and produced no flowers. Our studies show that the disease is caused by a subgroup A phytoplasma and this is the first report that aster yellows phytoplasmas cause disease in yucca. As the aster yellows phytoplasmas are transmitted by insects that are present in abundance in this region, there is potential for this disease to spread in the future. The information will aid implementation of quarantine regulations and help extension workers and plant diagnosticians to determine how to combat the disease.
Technical Abstract: In 2006, a newly emerging disease in yucca (Yucca treculeana) plants occurred sporadically in southwestern Texas. The affected yucca exhibited phyllody and abnormal bud proliferation on the inflorescence. The symptoms resembled those caused by phytoplasmal infection. Samples from four symptomatic and two asymptomatic yucca plants were collected. Total nucleic acid was extracted from abnormal bud tissue. To assess the etiological aspect of the disease, nested PCR, using phytoplasma specific primer pair P1/16S-SR followed by R16F2n/R16R2n, was employed for the detection of putative phytoplasmas. An amplicon about 1.2 kb was amplified from symptomatic yucca plants but not from asymptomatic plants. Restriction fragment length polymorphism patterns of 16S rDNA digested singly with AluI, KpnI, HpaII, MseI, HhaI, and RsaI endonucleases indicated that affected yucca plants were infected by a phytoplasma belonging to aster yellows group 16SrI ('Candidatus Phytoplasma asteris'), subgroup 16SrI-A. This is the first report of 16SrI-A phytoplasma infecting yucca.