Propagation and Long-Term Preservation of Several Isolates of Jujube Witches‘ Broom and Paulownia Witches‘ Broom-Phytoplasmas in in vitro Cultured Plantlets and Grafting Transmission of the Pathogens from the Diseased to Healthy Plantlets Genetic Variation of Paulownia Provenances Resistance against Paulownia witches‘Broom Effects of Agrobacterium tumefaciens on the Symptoms of Paulownia sp. Plantlet in Vitro Cultured ELIMINATION OF MLOS FROM PAULOWNIA TISSUE CULTURE BY MEANS OF THERMOTHERAPY COMBINED WITH STEP TIP CULTURE