Molecular Mechanism Of The Resistance To Jujube Witches Broom Disease In Ziziphus Jujuba Mill. 'Junzao'

Chinese jujube (Ziziphus jujuba Mill.) is an important and native fruit tree of China. Jujube witches'broom (JWB), caused by phytoplasma, is one of the most serious and destructive disease of Chinese jujube. Selecting cultivars with high resistance was regarded as the most powerful method to eradicate JWB and had made some progress,but the mechanism of resistance was still in its beginning stage.'Jiao 2', a strain of Ziziphus jujuba Mill.'Junzao', showed different resistance to JWB when it was grafting on diseased'Dongzao'and'Zanhuangdazao'. In this paper,'Jiao 2'was used as material to study the molecular mechanism of the resistance to JWB. The different mechanism was analyzed on the molecular level and the result would provide foundation for cloning of resistance gene and resistance breeding. The main results were as follow:1. Using phenol during the DNA extraction had significant affect on the detecting of JWB phytoplasma. Comparing the result of detecting of JWB phytoplasma and AFLP between using phenol and unusing phenol,the detection rate of JWB phytoplasma was decreased and even JWB phytoplasma couldn't be detected when the amount of JWB phytoplasma was in lower level. But using phenol during the DNA extraction had no significant effect on the result of AFLP analysis compared with the contrast.2. The molecular taxonomic status of JWB phytoplasma of'Dongzao'and'Zanhuangdazao'was defined. Based on the analysis of 16SrDNA conserved sequence,it proved that the similarity of JWB phytoplasma from'Dongzao'and'Zanhuangdazao'was 99.86% and both of them belonged to 16Srâ…¤group.3. The different resistance mechanism of'Jiao 2'to JWB was identified preliminarily. According to the result of AFLP analysis, the scions with phenotypic discrepancy when they were grafted on different diseased rootstocks were caused by the genotypic difference of rootstocks. The result of cDNA-AFLP showed that the scions with phenotypic discrepancy in the same rootstock were caused by the differential expression on RNA level.4. Based on the result of AFLP, 5 bands of cc-nbs-lrr gene which related to the resistance were gained. Among them,4 bands were from'Jiao 2'grafting on diseased'Dongzao'and 1 band was from'Jiao 2'grafting on'Zanhuangdazao'. The similarity between the sequences of those bands and mRNA of cc-nbs-lrr was more than 70%.5. 94 bands of differential expression were gained by cDNA-AFLP analysis of'Jiao 2'with phenotypic discrepancy on the same rootstock. 8 bands expressed specifically in later period of grafting; 74 bands were related to the expression of the resistance mechanism; 12 bands were related to growth and development of jujube. The result of blast showed that 15 sequences had high similarity(more than 97%)with E.coli BL21(DE3);3 sequences had similarity of 78% with Vitis vinifera contig VV78x205215.10;2 sequences had similarity of 72% with mRNA of Populus trichocarpa.