SCREENING OF CHINESE JUJUBE GERMPLASM WITH HIGH RESISTANCE TO WITCHES’ BROOM DISEASE

Chinese jujube (Ziziphus jujuba Mill.) is an important multi-purpose fruit tree both in China and South Korea.
Jujube witches’ broom disease (JWB) is a destructive disease caused by a phytoplasma.
After a literature review and other investigations, 30 accessions with no record of being infected with JWB were collected to construct a gene bank.
Five years tests showed that the method (II) of grafting healthy germplasm to be checked onto seriously diseased plants is much more effective for selecting highly-resistant accessions than the traditional method (I) of grafting diseased bark onto healthy germplasm to be checked.
Using method II, seven accessions (E, N, O, U, W, X, Z) were selected, which could be used to breed new cultivars and reconstruct the crowns of diseased trees.
The general characteristics of these highly-resistant accessions included low disease rate and late appearance symptoms that are light and alleviate gradually.
Grading systems (5 grades) of the disease severity at branch and at fluorescence microscopy level were constructed, and the relationship between the two levels was established.
It was discovered that disease resistance could be enhanced significantly through trans-grafting.
After three years of trans-grafting, the disease index of the accessions E, U, O and X decreased to 0% from 12.5-50%.

XI Eucarpia Symposium on Fruit Breeding and Genetics

M.J. Liu, J.Y. Zhou, J. Zhao

Ziziphus jujuba, phytoplasma, trans-grafting, gene bank, fluorescence microscopy

https://doi.org/10.17660/ActaHortic.2004.663.100