Effect Of Plant Growth Regulators On Disease Physiology Of Jujube Witches’ Broom

Chinese jujube is one of the most representative fruit tree in China and has very important economic value. Jujube witches-broom disease (JWB) caused by phytoplasma is the deadly infectious disease of Chinese jujube and the majority of Chinese jujube cultivars are highly sensitive to JWB. The chlorophyll content, enzymes activity, protein content and other physiological indicators of leaves in healthy tree and leaves in diseased tree were determined in our research. And then, the diseased planlets of JWB were cultured by using different concentration and kinds of plant growth regulators in vitro. The relevant biochemical and physiological indicators, the pathogen and endogenous hormone content of diseased plantlets with different treatments were determined in order to elaborate the influence of the phytoplasma on physiological metabolism of jujube tree and the effect of plant growth regulators on regulatory mechanism of plantlets with witches’broom disease. Those results would provide a reference for disease physiology of JWB.The main results were as follows:1. The photosynthesis of diseased jujube with JWB phytoplasma infection was significantly dereased. The content of chlorophyll a, chlorophyll b and the ratio of chlorophyll a/b of diseased tree leaves were all significantly lower than those of healthy leaves. In the later growth stage, chlorophyll content of healthy leaves decreased, but that of diseased leaves increased. The chlorophyll content of phyllody was the highest.2. The activity of protection enzymes of diseased jujube with JWB phytoplasma was significantly dereased. Compared with healthy leaves, the peroxidase (POD) and superoxide dismutase (SOD) activities of leaves in diseased tree increased, PPO activity was no significantly change. Their activities of phyllody and little leaf of diseased tree showed more significant change than other treatments.3. The content of soluble protein in leaves of diseased tree were significantly lower than that of healthy trees. MDA content of diseased leaves were significantly higher than that of healthy leaves. MDA content of phyllody was the highest in later growth stage.4. The chlorophyll content and a/b ratio of diseased plantlets could be significantly increased by IBA0.5mg/L and6-BA1.5-2.0mg/L.5. SOD, PAL, PPO and POD activity of diseased plantlets with JWB was significantly affected by IBA and6-BA. SOD, PAL and PPO activity could be significantly increased by a certain concentration of IBA and6-BA. POD activity of diseased plantlets was reduced by all concentration of IBA and6-BA.6. Soluble protein content and proline content of diseased plantlets were reduced by IBA treatment. Soluble protein content and proline content were significantly increased by treatment with6-BA. MDA content of diseased plantlets was significantly reduced by IBA and6-BA treatments.7.The effection of plant growth regulators on endogenous hormones of disease plantlets showed that:Fristly, the plant growth regulators could significantly regulate metabolism of endogenous hormones of diseased plantlets and increased contents of IAA, ZR, ABA and GA. Secondly, compared with IBA,6-BA had a much greater effect on hormones metabolism, the6-BA0.5mg/L had the most significant effect; Thirdly, the metabolism of IAA and ABA were more sensitive to treatment of plant growth regulators.8. Relevance analysis indicated that endogenesis IAA content was significantly negatively correlated with chlorophyll content, ABA content and PAL activity; but endogenesis ZR content were significantly negatively correlated with PAL activity. With IBA2.0mg/L, endogenesis IAA content was significantly negatively correlated with endogenesis ZR content; but with6-BA1.5mg/L, endogenesis IAA content was significantly positively correlated with endogenesis ZR content. With IBA1.5mg/L, IAA content was significantly positively correlated with endogenesis GA content, SOD activity and free proline content.