| Citrus Huanglongbing(HLB) is caused by “Candidatus Liberibacter spp.” which can cause the economic loss of citrus production, quality decrease of fruit and the death of plant, The HLB was also known as "cancer" of Citrus. With the development of citrus industry, HLB is widely spread in Asia, Africa, America and other citrus production areas. The HLB was able to affect alomost all citrus cultivars and seriously affects the healthy development of citrus industry. The disorder starch metabolism is the main phenomenon of citrus after the plant was infected by “Candidatus Liberibacter asiaticus”. There is a large number of starch accumulation in the leaves and stems after infection. In order to analyze the expression level of relevant enzymes involved in starch synthesis condition and find out the reason of starch accumulation after infection, three enzymes, granule- bound starch synthase, ADP glucose pyrophosphorylase and Citrus sinensis beta-amylase 8- like were selected and evaluated on citrus shatangju.Huanglong molecular detection technology need skilled technical personnel, expensive apparatus,reagents and long testing time which is not suitable for large-scale survey in the field. So it is important for huanglong and prevention to develop a rapid detectionmethods which can be applied in the field diagnosis. In this study, we designed a set of rapid diagnostic methods for HLB based on the phenomenon of starch accumulation with Iodine starch reaction. The accurary of this method was evaluated and compared with the conventional PCR and real-time PCR method. The realization of this rapid detection is significant for the prevention and control of HLB.The main research conclusions are as follows:1. Compared with healthy controls, The expression of granule-bound starch synthase in Shatangju is up-regulated, after being infeccted by “Ca. L. asiaticus”. Early stage of infection, the fluctuation of gene expression reflects the host response to the bacterium; With the growth of the bacteria, the impact of bacteria to the host, tend to be stable, the granule-bound starch synthase up-regulated stablely.2. The ADP-glucose pyrophosphorylase is down-regulated in march and may, and up-regulated in other month. The fluctuation of gene expression during February and may may have a relationship with the season or the growth repair function afer grafting. Compared with healthy controls, The expression of ADP-glucose pyrophosphorylase in Shatangju is up-regulated, after being infeccted by “Ca. L. asiaticus ”.The stable up-regulated time of ADP-glucose pyrophosphorylase is earlier than granule-bound starch synthase, but the expression of granule-bound starch synthase is higher. We speculate that, ADP-glucose pyrophosphorylase plays a leading role during the growth of the bacteria, and with the improve expression of granule-bound starch synthase, it plays a leading role after November.3. The expression of sinensis beta-amylase 8-like in Shatangju is up-regulated after being infeccted by “Ca. L. asiaticus”. The up-regulation of granule-bound starch synthase and ADP-glucose pyrophosphorylase lead to the starch accumulation, which induce the up-regulation of sinensis beta-amylase 8-like.4. By comparing the samples on young trees and old trees, we find that the rapid detection technology of HLB effects best on the old trees in spring with the accuracy of 94.12%. There is little difference between young trees and old trees in other seasons. It has a higher accuracy of the rapid detection on maturely symptomatic leaf In spring and summer and on young leaves in autumn and winter, all with the accuracy of more than 80%. |
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