| The induced resistance or the acquired resistance is a kind of resistance produced by plant infected by pathogens or treated by chemistrical materials,which can protect plant from the subsquent infection of plant pathogens.Plants can acquire partial or systematic resistance when they were induced by different biological or abiotic elicitors, and these elicitors can activate a special dot of signal web by different signal route,then induce different plants to produce special protein for resisting the attack of pathogens and pests.Systematic acquired resistance(SAR) is a kind of special induced resistance, which has three charactoritics:systematic,persisting and broad spectrum of resist disease.It has significant theoretical and practical value to research and find materials that can induce plant resistance.DL-β-aminobutyric acid(BABA) is a kind of chemical elicitor for plant,which has widely induced resistance activities.In order to develop and exploit this kind of amino acid pesticides,a study on induced resistance produced by BABA and its preparations in pepper and tomato against TMV,CMV,Phytophthora capsici PC48,Xanthormonas vesicatoris(Boidge) Dowson and Meloidogyne incognita(Kofoid and white) Chitwood in greenhouse,and inducing resistance activation of cabbage against Peronospora parasitica in fields Were conducted.Furthermore,enzyme and moleculer research work with respect to mechanism of BABA inducing pepper to resist disease also had been done.The main results were as following:BABA could induce pepper to acquire resistance against TMV and CMV when pepper leaves and stems was sprayed with this kind of amino acid pesticides.The effects of BABA on resistance induction were not significantly different among the varieties of Qiemen,931 and 21.The effects of BABA on induction was influenced by concentrations of elicitors.The optimal treatment concentration was about 1000μg/mL, and the plants would not be damaged at this concentration.The resisitence was generated from three pepper strains 3 days later when they were treated by BABA.With time prolong,the resistance began to rise,and the induced resistance effect of BABA came to the highest after the plants were treated five or six days with BABA,then it began to decrease,the effect could remain more than 15days With the prolong of pepper reproductive period,the induced effect of BABA on sweet pepper strengthened.The resistance effect could be improved with the increasing of TMV concentration.BABA,JA and MeJA could induce pepper to generate resistance against TMV after the leaves and stems was treated.Inducedresistance effect &three elicitors didn't show obvious diference,and the highest induced effect could reach above 50%.The effect of BABA,JA and blend solution on Qianmeng was 42.2%,35.2%and 36.7% repectively;the effect produced by above three elicitors on 931 was 349%,42.8%and 44.5%respectively;and the effect of them on 21 was 46.2%,39.6%and 43.6%.The induced resistene effect produced by blend solutiont with equal concentration was located in the middle of BABA and JA,which showed that resisting action and increasing effect action were not existeA between BABA and JA.The induced effect of 10%BABA powder against several plant diseases was better than that of the pure BABA,especially against pepper Phytophthora capsici.Its induced resistance effect against pepper Phytophthora capsici was still kept 88%after applied ten days.The induced effect of BABA on the cabbage against Peronospora parasitica was better than that of other usual pesticides used in production.BABA derivative also showed induced resistance ability to TMV,CMV,Phytophthora capsici and MeIoidogyne incognita.The results of enzymes assays showed that activities ofβ-1,3-glucanases, chitinases and POD all increased in different levels after BABA treated,but the increasing extent of PR protein activities in three peppers were higher than that of PR protein activities in sweat peppers,and the activity changes and induced effects of three PR protein concorded with each other.The expression of Chitinase ClassⅢgene and lipoxygenase gene could be expressed when plant was induced by BABA.Afterward treatment,the gene expression of Chitinase ClassⅢand lipoxygenase all showed a high-low-high developing trend,a few genes expressed six hours later afterward treatment,the expression quautities came to peak between 12 and 24 hours afterward treatment,then gene expression began to decrease,till 48 hours later,gene expression stopped or expressed a few Nucleotide sequence analysis of the differential cDNA fragment showed that the nucleotide sequence is highly homologous with the nucleotide sequence encoded lipoxygenase of Capsicum.P450 is responsible for biosynthesis and metabolism in plants.Some of P450 have significant actions in plant defence response.Through RT-PCR and RACE,The complete sequence of CYP92A was cloned from gene expression systems of pepper (Capsicum chmense) leaves induced by BABA,The analysis of bioinformatics showed that CYP92A gene encoded a 509-amino acid multi-peptide,which contained a conservertive Heme-binding region of cytochrome P450.This protein took on similarity of secondary structure with crystal structure of CYP450 reported,therefore,it was confirmed that CYP92A was cytochrome P450 in fact.By phylogenetic analysis,it was believed that CYP92A belong to 92A sub-family of P450.integrating with other reports with respect to 92A sub-family genes,it can assume that CYP92A may perticipate in plant defence response.Above results showed that BABA has a potential to induce pepper(Capsicum chinense) to produce good resistance against virus,bacteria and fungi deseases.The generation of resistance was related to the expression of corresponding gene and the production of relative proteins during the disease period.At the same time,BABA could induce gene expression of P450 in Capsicum chinense leaveso All these results provided a new concept for understanding the mechanism of the induced resistance of BABA.
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