A destructive phytoplasma disease - jujube witches' broom and its control.

摘要

Jujube witches' broom (JWB) is a destructive phytoplasma disease of Chinese jujube (Ziziphus jujube Mill.), an increasingly important fruit tree in dry lands. The trees infected with JWB usually die within 2-3 years. This paper briefly reports the results of the authors' research on JWB in the past 12 years. A practical fast fluorescence microscope check using DAPI and accurate PCR detection method for JWB phytoplasma were established. Year-round observation showed that JWB phytoplasma could well survive in branches throughout the winter and roots were not necessary for the multiplication of phytoplasma and symptom development. The heavier the disease, the higher the Zeatin content and value of Zeatin/IAA; both parameters were significantly higher in diseased parts than in the healthy ones. The contents of Ca, Mg and Mn in diseased leaves were significantly lower than in healthy ones. On the contrary, the activity of peroxidase and polyphenol oxidase in diseased trees was higher than in healthy ones. A sustainable preservation and multiplication system for JWB phytoplasma via tissue culture of host plant was successfully established which provides a convenient and reliable platform for the basic and applied research on JWB. Four individuals were selected for their high resistance to JWB. Very promising was the resistance of a clone of cultivar Junzao, which was then named cultivar 'Xingguang'. Based on this study, a control strategy for JWB was put forward.