Abstract
Phytoplasma-infected paulownia tissue cultures showing typical witches'-broom symptoms were heat-treated at 35°C in a growth chamber for five weeks. Then the meristem tissues were excised and cultured in MS medium at 25°C. Untreated comparable infected paulownia tissue cultures were maintained at 25°C as control. The treated paulownia plantlets were symptomless and grew vigorously with healthy appearance. The total DNAs were extracted from both treated and untreated tissue cultures. After amplification by polymerase chain reaction (PCR), no phytoplasmas were detected in 94% of the meristem cultures from the treated plantlets and in all of healthy control cultures using universal primers. A very faint DNA band was observed in 6% of the meristem cultures. A specific, prominent DNA fragment was amplified from DNA samples of the diseased cultures. The results showed that the phytoplasma-free paulownia plantlets could be obtained by selecting meristem cultures through PCR-based phytoplasma DNA detection after the heat treatment of infected tissue cultures.
