Rubber Tree Resistance Induced By BTH To Rubber Powdery Mildew

Rubber powdery mildew is one of the most important diseases on rubber trees, which is caused by Oidium heveae B.A.Steinm. It affects seriously the growth and yield of rubber trees. Induced resistance is the use of biotic or abiotic inducers to stimulate plant defense genes to achieve the effects of disease prevention. Induction of plant resistance has become a new way of plant protection to control plant diseases, pests and parasitic weeds.In this experiment, four inducers of BTH (benzothiadiazole), PHDC (Prohexadione calcium), Chitosan and Comcat(?) were screened with rubber clone Reyan 7-33-97 and Oidium in pot tests. The effective inducer BTH was used to conduct a series of tests on induction intervals, the numbers of induction and the activity of enzymes related. At the same time, the cDNA library induced by BTH to powdery mildew of rubber tree leaves was established using suppression subtractive hybridization (SSH) technology. Gene expression of induced resistance to powdery mildew was analysed. It tries to explain the mechanism of BTH-induced resistance to rubber tree powdery mildew in molecular level and provide a new control method for the disease. The results of the study included the following six aspects:1. Four inducers of BTH, PHDC, Chitosan and Comcat could induce rubber tree resistance to powdery mildew. BTH at 250mg/L and Chitosan at 500 times had better control of 57.8% and 51.4%, respectively. But BTH was significant better than Chitosan and other treatments.2. The optimal inoculation intervals were from 5 to 11 days after induction of BTH at 250mg/L, those had control efficacy of 33 to 57%. The duration was at least more than 11d. After induction, with the inoculation interval increasing, the effect of induced resistance was also reduced.3. Activities of POD (peroxidase) and PAL (phenylalanine ammonia lyase) were significantly higher than control after BTH at 250mg/L treatment and the pathogen inoculation. Activities of the enzymes were increased again after BTH twice treatment when the enzyme activities declined to control level.4. The modified SDS method was the best method for extraction of total rubber RNA, which could effectively remove the leaves latex and polysaccharides and conductively construct cDNA library with suppression subtractive hybridization (SSH), after comparison of RNAiso Reagent Kit, modified SDS and modified CTAB-PVP method. 5. cDNA library of BTH induced rubber tree resistance to powdery mildew was constructed by Clontech's PCR-select cDNA subtraction kit. so in the case of small amount of RNA synthesis of cDNA has high efficiency, the smooth development of SSH basis. The subtractive library had high quality after detection of all key processes of SSH, such as joint connection efficiency, subtractive efficiency and conversion efficiency.6. There were 21 cDNA sequences and 2 repeats known of function as energy and basic metabolism, signal transduction, membrane and transport and secondary metabolism,14 sequences unknown of function and 2 sequence no significant match in nucleic acid sequences database after detection of sequences of 42 positive clones randomly selected from the cDNA library and comparison on nucleic acid sequences in Genbank.BTH could effectively induced rubber tree resistance to powdery mildew through increasing expresses of defense-related genes and activities of resistance-related enzymes in leaves of rubber tree. It provides a new approach for rubber tree powdery mildew control and lays a good foundation for further study on expresses of defense-related genes and signal translocation in rubber trees.