Abstract:

The resistance of 6 cultivars of Ziziphus jujuba var. Hupingzao, Hamazao, Pozao, Mayazao, Dunzizao, Changhongzao, and a sour date Z. spinosa as well as 46 single resistant trees selected from Pozao against jujube witches-broom symptom were appraised by graft transmission using infected barks and twigs at the test site located at Tang County, Hebei Province. It was shown that both Hupingzao and Hamazao did not displayed any witches broom symptom (high resistance) after continuous graft inoculation six times from 1996 to 2002, while cultivars, Changhongzao, Mayazao, sour date, Pozao and Dunzizao demonstrated different susceptibility in order of 66.6%, 78.6%, 80.0%, 100% and 100%, respectively. The selected 46 resistant single trees of Pozao were with average disease incidence of 81 1% and with distinct resistance diversity among them, 4 trees did not show any symptom in the course of all graft inoculation, indicating they possessed relative high and stable resistance. Further detection by means of DAPI fluorescence microscopy and polymerase chain reaction(PCR), specially PCR, it could be found phytoplasmas usually from most resistant clones without symptom after graft inoculation, indicating that which had already carried low number of phytoplasmas and suggesting possible inhibition of those materials to the phytoplasma propagation. It was found that a different specific light blue spot in the resistant and susceptible clones by thin layer chromatography in two system, more unique golden spots were found by means of auto fluorescence microscopy spreading in the areas of phloem and parenchyma related to two Pozao and one Hupingzao in bark section.

Key words: jujube witches-broom disease, resistance, graft transmission, phytoplasma detection, fluorescent substance