High-throughput screening system of citrus bacterial cankerassociated transcription factors and its application to the regulation of citrus canker resistance

One of the main diseases that adversely impacts the global citrus industry is citrus bacterial canker(CBC),caused by the bacteria Xanthomonas citri subsp.citri(Xcc).Response to CBC is a complex process,with both proteinDNA as well as protein–protein interactions for the regulatory network.To detect such interactions in CBC resistant regulation,a citrus high-throughput screening system with 203 CBC-inducible transcription factors(TFs),were developed.Screening the upstream regulators of target by yeast-one hybrid(Y1H)methods was also performed.A regulatory module of CBC resistance was identified based on this system.One TF(CsDOF5.8)was explored due to its interactions with the 1-kb promoter fragment of CsPrx25,a resistant gene of CBC involved in reactive oxygen species(ROS)homeostasis regulation.Electrophoretic mobility shift assay(EMSA),dual-LUC assays,as well as transient overexpression of CsDOF5.8,further validated the interactions and transcriptional regulation.The CsDOF5.8–CsPrx25 promoter interaction revealed a complex pathway that governs the regulation of CBC resistance via H2O2homeostasis.The high-throughput Y1H/Y2H screening system could be an efficient tool for studying regulatory pathways or network of CBC resistance regulation.In addition,it could highlight the potential of these candidate genes as targets for efforts to breed CBC-resistant citrus varieties.

Factors Influencing Bacterial Canker Disease of Kiwifruit and the Control Countermeasures

Survey was conducted to investigate the occurrence laws of bacterial canker disease of kiwifruits in Liupanshui area, Guizhou Province, and the patho- gens and hazard symptoms of the canker disease were introduced. The results showed that the factors influencing the occurrence of bacterial canker disease of ki- wifruit were identified as inter-species resistance, agronomic traits, meteorological and ecological conditions, cultivation and management techniques and fertilization levels. Techniques for the comprehensive control of kiwi canker disease were stated, and control suggestions were proposed.

CONTROL TECHNIQUE OF BACTERIAL CANKER OF POPLAR

The poplar bacterial canker caused by Erwinia sp. is a serious disease spreading in most parts of Northeast China, where poplars are cultivated. The disease seriously infects those poplars belonging to section Aigeiros or the intersection hybrids of section Tacamahaca and section Aigeiros and their clones. Five fine poplar cultivars resistant to the bacterial canker have been obtained by screening tests. They are Lz2(Populus simonii × nigra var. italica), A15(P. × sp.), 613(P. × sp.), A102and A98(P. × simonii × sp.). The following chemicals are obviously effective, such as: 50% DT germicide, 40% XF-136 and 10% C.C.M.A. or 12.5% ramphencol and 50,000 ppm/ml validamycin, with which the stems or the roots can be watered.

Control Efficacy of Streptomyces sp. SY-L12 and Chitooligosaccharide on Kiwifruit Bacterial Canker, Pseudomonas syringae pv. actinidiae

[ Objective] The paper was to develop a priority scheme for prevention and control of kiwifruit bacterial canker with biological agents. [ Method ] The inhibitory effect of Streptomyces sp. SY-L12 on the growth of Pseudomonas syringae pv. actinidiae were assessed using liquid co-culture and inhibition zone meth- ods. The control efficiency of Streptomyces sp. fermentation broth against kiwifruit bacterial canker was studied via potted trial. [ Result ] As Streptomyces sp. SY- L12 was incubated for 24 h, the growth inhibition rate of its fermentation broth on P. syr/ngae pv. actinidiae was 94.0%. The control efficiency of fermentation broth against P. syringae pv. actinidiae was the best of 85.4% in potted trial when Streptomyces sp. SY-L12 grew at 28~C, 150 rpm for 8 -9 d, better than that of control agent copper hydroxide. The control efficiency was improved as the agent was mixed with 1 mg/L chitooligosaccharide. [ Conclusion] Streptomyces sp. SY-L12 could effectively inhibit the growth of P. syr/ngae pv. actinidiae, and can be developed as biological agent against kiwifruit bacterial canker.

Indoor Screening of Bactericides against Kiwifruit Bacterial Canker

[ Objective ] The paper was to screen the effective agents against kiwifruit bacterial canker in Wanzhou District of China. [ Method ] Ten kinds of com- mon commercial bactericides preliminarily screened were selected for indoor antibacterial test using paper plate method and plate streaking method, and six kinds of bactericides with good antibacterial effects were further screened for indoor toxicity test. [ Result] Chloramphenicoloethylicin had the best antibacterial effect, with EC50 of 36.34 rag/L; followed by Xintianxlucai No. 6 and embamycin, with EC50 of 83.21 and 92.34 mg/L, respectively. [ Conclusion] Cldoramphenicoloethylicin, Xintianxiucai No. 6 and embamycin screened in the test had good antibacterial effect against kiwifruit bacteriai canker in Wanzhou District, and chlorampheni- coleethylicin was the most effective agent. These three agents could be directly applied to control kiwifruit bacterial canker in production, while application time and climate conditions in fields should also be considered during the actual application process. It is suggested that three agents can be used alternatively in order to de- lay the resistance of plants.

Characterization of Chinese Isolates of Mango Bacterial Canker Xanthomonas campestris pv. mangiferaeindicae

Mango bacterial canker is caused by Xanthomonas campestris pv. mangiferaeindicae. During 2009 and 2013,leaves,twigs and fruits of mango were collected from commercial and experimental mango fields with typical canker symptoms in Hainan,Guangxi,Guangdong and Szechwan Provinces of China. The causal agent was identified as X. campestris pv. mangiferaeindicae through KC semi-selective medium isolation,pathogenicity tests,and sequencing of the gyrB gene.

BACTERIAL SWOLLEN STEM CANKER ON POPLAR:THE DISEASE AND ITS CAUSES

The bacterial swollen stem canker of poplar is prevalent in planted poplars of northeast China. Serious damage occurs in the form of necrosis, putridity, cankers, swollen stems and discolored wood of trunks and branches of young and mature trees. Tests of allergic reaction, pathogenicity, culture characteristic, Gram stain and anaerobic culture revealed that the pathogen is Erwinia sp. Its occurrence depends mainly on the predisposing factors of the disease among which the susceptibility of poplars is the most important one. The disease becomes widespread in association with low-lying and high-humidity terrain, frost injury, node wounds, insect damage, and pruning and other mechanical wounds. Harmful factors promote the disease.

Preliminary Study on the Control of Kiwifruit Canker by 6%Ascorbic Acid Water Aqua

[Objectives]This study was conducted to investigate the control efficacy of 6% ascorbic acid water aqua on kiwifruit bacterial canker. [Methods]The ascorbic acid water aqua was sprayed onto annual potted kiwifruit seedlings once every 5 d,for three times in total,and Pseudomonas syringae pv. Actinidiae was inoculated by needle punching 7 d later. Scab diameter and number of newly infected scab were investigated to analyze the control efficacy. [Results] Kiwifruit plants were treated with 6% ascorbic acid water aqua,and after 30 d,the 20 mg/L treatment showed an incidence rate of 25. 5%,and the 60 mg/L treatment exhibited an incidence rate only of 12. 1%; and after 60 d,the relative control efficacy reached 90. 7% at the mass concentration of 60 mg/L. [Conclusions] The6% ascorbic acid water aqua weakened the destruction and expansion of the pathogen in plants,effectively improved the resistance in kiwifruit plants,and had certain control efficacy on kiwifruit canker.