Abstract:

Jujube Witches' Broom (JWB), caused by phytoplasma, is the most serious and destructive disease of Chinese Jujube. The distribution and year-round concentration variation of JWB phytoplasma were studied under fluorescence microscope using DAPI. The results showed that phytoplasma might exist in the sieve tubes of all organs, phytoplasma contents varied with organs, sides of organs and growing seasons, phytoplasma usually existed in the roots of the same direction with diseased branches. The uneven-distribution could be observed much often in lightly diseased trees than in seriously diseased one. In roots, the content of phytoplasma was highest in May, relatively low in June, July and August, and lowest in December to March. In branches, the content of phytoplasma increased gradually with the rising of the temperature after bud sprouting in April and May, then increased dramatically and reached peak in July and August, thereafter decreased in autumn. From December to February, there was still a large amount of phytoplasma in diseased branches. The content of phytoplasma in branches kept higher than in roots throughout a year.

Key words: Jujube Witches' Broom, phytoplasma, distribution, year-round variation