A Preliminary Study On Induced Resistance Against Cotton Insect By Methyl Jasmonate And Salicylate

Taking at the age of1-2real leaves of Zhongmiansuo37for study, and using soilbioassay and physical metering methods, in order to study the induced effect mechanisms ofnutrient substances, phenolic secondary metabolites and defensive protease activities in cottonleaves treated by exogenous methyl jasmonate and salicylate from the perspective of physiologicaland biochemical; In addition, using the analysis method of univariate two factors or three-wayANOVA and multiple comparisons for physiological and biochemical substances (free aminoacid, protein, soluble sugar, tannin, flavonoids, phenolic acid, PPO, PAL, CI, TI) in cotton leaves,based on three processing levels of different times, concentrations, and xenobiotics. Moreover, westudied on the effect of the cotton aphids’ growth and development included survival rates,reproductive rates and body weight etc, feeding with the cotton leaves treated by differentconcentrations of methyl jasmonate and salicylic acid after4days, provided a theoretical andpractical basis for biological control of A. gossypii. The results were as follows:1. Exogenous MeJA and SA treatment can induce cotton leaves to reduce the nutrientcontent significantly, and the induced effect was related to the xenobiotics, times and theconcentrations of the treatment.With the prolonging of the treatment time, soluble sugar, protein, free amino acid content incotton leaves was decreased firstly and then rising, and with a characteristics of "V" type changes.The induced effects on soluble sugar and free amino acid content in cotton leaves were thestrongest after treated for2days, the content is the lowest, and the protein content in cottonleaves processed after4days was the lowest.The induced effect on free amino acid and soluble sugar content was the largest afterexogenous MeJA0.5mmol/L treatment; The content of protein in cotton leaves processed byMeJA0.5and5mmol/L treatment, significantly lower than control treatment of27%. SAtreatment on cotton leaves free amino acids and soluble sugar content has inductive effect ofincreasing concentrations, after the treatment of5mmol/L and its content was the lowest, lowerthan the control treatment about22%and11.78%respectively, The most inductive effect ofprotein content was treatment after SA0.5mmol/L and SA5mmol/L, and the protein content wassignificantly lower than control treatment7%~8.52%, and there is no obvious difference betweenthem.Moreover, it was showed that induced effects of exogenous MeJA on the nutritional contentin cotton leaves becomes more apparent compared with SA, from a single dependent variablethree-way ANOVA and multiple comparisons.2. Exogenous MeJA and SA treatment can induce phenolic secondary metabolites content incotton leaves increases significantly.In a processing time range of8days, with the extension of processing time, the content offlavonoid, tannin and the total phenol showed a trend was inverted "V" shaped. After univariatetwo-way ANOVA and multiple comparisons showed that the induced effects on the content of flavonoids, tannins and total phenol in cotton leaves under the treatment of different times,concentrations and their interactions differences significantly. The induced effect on flavonoidsand total phenol content in cotton leaves was most significant, treated by MeJA and SA after4days, and the content of them was significantly higher than other processing time. And the inducedeffects on tannin content was significantly higher than other processing time under MeJA handleafter4days and SA treated on6days.Secondly induced effect is also related to the concentration of the MeJA and SA. Theflavonoid, tannin, phenolic content in cotton leaves treated by MeJA and was significantly higherthan the control treatment.Moreover, it was showed that induced effects of exogenous MeJA on thetannin, flavonoid and total phenolic content in cotton leaves becomes more apparent comparedwith SA, from a single dependent variable three-way ANOVA and multiple comparisons.3. The defense protease activity within the cotton leaves could be induced increased under thetreatment of exogenous MeJA and SA.Analysis by a single dependent variable two factors and three-way ANOVA and multiplecomparison showed that, there were significant differences for PPO, PAL, CI and TI activitiesinduced by different time, concentration, xenobiotics (MeJA or SA) and their interactions. Theactivities of PPO, PAL, CI and TI in cotton leaves had a changing trend of increased first and thendecreased, then increased with the time goes on. The induced effect of PPO and PAL activity incotton leaves was significantly higher than other time processing after treated by MeJA and SA inthe4thday, and the activities of TI and CI were the most significant induced by MeJA in the4thday and the6thday respectively. In addition, the TI activity in G. hirsutum leaves rise to themaximum processed by SA in the fourth day, and CI activity reached to the highest in the4th,8th,6thday, and there was no obviously difference between them.Furthermore, the induced effect was related to the concentrations of the treatment, theinductive effect on the PPO activity was significant, after handled by MeJA0.5、5mmol/L andSA5mmol/L; PAL activity was the highest after treatment of MeJA0.5mmol/L and SA5mmol/L,and it was significantly higher than the control around32.07%and10.38%. After spraying thecotton leaves with MeJA0.5mmol/L, the induced effects on activities of TI and CI were the mostsignificant, and higher than the control treatment of30.77%and19.92%.Moreover, it was showed that induced effects of exogenous MeJA on the PPO、PAL、TI、CI activity in cotton leaves becomes more apparent compared with SA, from a single dependentvariable three-way ANOVA and multiple comparisons.4. MeJA and SA treatment could cause certain influence to the growth and development ofAphis gossypii.Exogenous MeJA and SA treatment had obviously induced delay effect on the course ofdevelopment of A. gossypii nymphs. The biggest induced treatment were MeJA0.5mmo/L andMeJA5mmo/L, as a result, the developmental duration of aphid’ was extended for1.67~1.77dcompared with control. There was no significant induced effect on survival rates of the wholenymphal stage under the treatment of MeJA and SA.Exogenous MeJA and SA treatment could reduce the amount of litter A. gossypii significantly,and the fecundity of A. gossypii reached lowest after treated by MeJA0.5mmo/L, lower than thatof the control about11.37.It could reduced body weight of instar nymphs and adult aphid, when feeding on the cotton leaves treated by the exogenous MeJA and SA, the body weight of instar nymphs were thelowest after the treatment of MeJA0.05mmo/L, and it was lower than the control of50%.According to ANOVA and multiple comparison shows that, it had obvious inductive effecton net appreciation rate, developmental duration, intrinsic rate and population doubling time of A.gossypii under the treatments of MeJA and SA, exogenous MeJA0.5mmol/L treatment couldobviously inhibit the reproduction of A. gossypii, population diffusion, and development trend.Visibly, the exogenous MeJA had a more significant impact on growth and development of A.gossypii.