Physiological And Biochemical Study On The Response Of Capsicum Annuum To Phytophthora Capsici Infection

Phytophthora capsici Leon.is a destructive disease,which causes incalculable loss to yield of Capsicum L.in China.It is a great significance in guiding to study physiological and biochemical mechanism of Capsicum annuum to Phytophthora capsici infection on control of Phytophthora capsici in yield of Capsicum L.,and genetic improvement of Capsicum to Phytophthora capsici.Three different cultivar of Capsicum L.,which have distinct difference in resistance to Phytophthora capsici Leon.,are used to study on physiological basis to Phytophthora L.,and salicylic acid(SA)and methyl jasmonate(MJ),two kinds of hormone, which can also used to be elicitor,are employed to treat the three cultivar,through which the role of SA & MJ in the defense response to Phytophthora L.is investigated and analyzed at large from inside and outside.The results are showed as following:JTJ,L-11 and ADJ are different cultivar of Capsicum L.,having distinct difference in resistance to Phytophthora capsici Leon.When compared to the control,many of physiological indicators of the treatment inoculated with Phvtophthora capsici Leon.are changed,including parameters of chlorophyll fluorescence,content of reactive oxygen species(ROS)and activity of oxidant scavengers.But many of them have not any rule besides parameters of chlorophyll fluorescence,the possible reasons of which are the difference in resistance to Phytophthora capsici Leon.or different mechanism among the cultivar.Compared to the control,the treatment inoculated with Phvtophthora capsici Leon.lead to decrease in parameters of chlorophyll fluorescence.The other physiological indicators are different in cultivar,for example the content of soluble sugar,dissociative amino acid and praline of resistant variety(JTJ)is reduced;but to susceptible variety(ADJ),the content of soluble sugar and dissociative amino acid are elevated,and content of praline is decreased.For ROS and oxidant scavengers,content of superoxide radical is increased,content of hydrogen peroxide and activity of superoxide dismutase and peroxidase are increased;but to activity of catalase, resistant variety is enhanced and susceptible variety is depressed.The resistance induced by SA/MJ can fortify the capability of Capsicum L.to Phytophthora capsici Leon.,which is embodied in the many aspects:activity of SOD of either resistant or susceptible variety is hoisted;the content of O₂^?=of resistant variety(JTJ)is heightened,and of susceptible variety(ADJ)is attenuated.By the study and analysis of dynamic curve of SA and MJ,it is found that SA and MJ play an important role in the resistant to Phytophthora capsici in Capsicum annuum,the early stage of which the content of SA or MJ is changed acutely.The correlation among SA,MJ,ROS and oxidant scavengers is also analyzed especially by statixtical analysis methods.It is verified that the correlation between ROS and enxymatic antioxidants,and found the relation between SA and H₂O₂,MJ and POD,SA and CAT,though the correlative coefficient of them are not arrived at 0.01 or 0.05 significance levels,it can also help us to study the physiological and biochemical on response of Capsicum annuum to Phytophthora capsici infection.All in all,ROS,SA and MJ play an very important role,as signal transduction material,in the response of Capsicum annuum to Phytophthora capsici infection.ROS are a central component in stress responses and the level of ROS determines the type of response.Whereas at low concentrations ROS induce defence gene and adaptive response,at high concentrations celldeath is initiated.To allow for this dual role,cellular levels of ROS must be tightly controlled, in which the oxidant scavengers provide the flexibility necessary for these functions.SA and MJ are two kinds of signal in the response to diease,which play an important role in the response of Capsicum annuum to Phytophthora capsici infection,and endow Capsicum annuum with acquired resistance.By the study on SA and MJ which act as elicitors,it is found that spraying with SA/MJ can induce resistance of Capsicum L.,and enhance capability to disease.