The Association of Phytoplasma with Stunting, Leaf Necrosis and Witchesʹ Broom Symptoms in Magnolia Plants

In 1999±2000 a severe disease was observed on plants of four Magnolia spp. cultivated in a commercial nursery in Poland. A€ected plants showed a progressive loss of vigour, were stunted, and had severely malformed leaves, leaf necrosis and witchesʹ broom. Phytoplasma was detected in magnolias with severe symptoms and in dodder-inoculated Catharanthus roseus seedlings by nested polymerase chain reaction (PCR) assay with primer pair R16F1/R0 followed by universal (rA/fA) and group speci®c (R16(I)F1/R1) primer pairs which ampli®ed a fragment of phytoplasma 16S rDNA. The PCR products (560 bp or 1.1 kb) of all samples used for restriction fragment length polymorphism analysis after digestion with endonuclease enzymes AluI and MseI produced the same pro®le which corresponded to that of an aster yellows phytoplasma reference strain. Phyto- plasma DNA was detected throughout the growing season in roots, stems and young but not mature leaves. Electron microscope examination of the ultra-thin sections of the leaf and stem of diseased magnolias showed collapsed and degenerated sieve tube elements with wall thickening. The reduced lumen of these sieve elements contained numerous vesicles and membrane- bound structures, but no typical phytoplasma cells. This is the ®rst report of aster yellows phytoplasma in magnolia identi®ed by molecular assays.