| Abiotic stresses,such as salinity and drought will not only affect the growth and development of cotton plants,but also affect the secondary metabolism in cotton plants.The secondary metabolites may affect the occurrence of pests on cotton plants,and thus become an important factor affecting the population dynamics of Tetranychus cinnabarinus under salt and drought stress.This paper studies and analyzes the secondary metabolism of cotton induced by salt and drought stress and its relationship with the growth and detoxification enzyme activities of T.cinnabarinus.It aims to reveal the effects of abiotic stress on the growth and development of T.cinnabarinus on cotton plants and its mechanism.To provide theoretical basis and technical support for the comprehensive control of T.cinnabarinus in saline-alkali and dry land.1.In order to determine the effects of salt and drought stress on secondary metabolism of cotton,we conducted an experiment to determine the gossypol and tannin contents in cotton leaves stressed with different concentrations of Na Cl and PEG 6000(polyethylene glycol),respectively.The results showed that the content of gossypol and tannin in the leaves of SCRC28 and K836 were significantly affected by salt and drought stress.With the increase of Na Cl and PEG 6000 concentration,the content of gossypol and tannin in the leaves of SCRC28 and K836 were higher and higher.Compared with the control,the gossypol content in SCRC28 treated with 50?100?150?200 m mol·L-1Na Cl increased by 9.19%?13.43%?19.79%and 34.63%respectively;the tannin content in SCRC28 treated with 50?100?150?200 mmol·L-1Na Cl increased by 10.71%?25.00%?30.36%and 40.63%respectively.The gossypol content in K836 treated with 50?100?150?200 m mol·L-1Na Cl increased by 2.21%?9.78%?14.83%and 30.91%respectively;the tannin content in K836 treated with 50?100?150?200 mmol·L-1Na Cl increased by 5.13%?17.95%?26.67%and 34.87%respectively.The content of gossypol in SCRC28 treated with 2.5%and 5%PEG 6000 increased by 10.74%and 37.60%respectively compared with CK,the content of tannin increased by 20.10%and44.50%respectively compared with CK.The content of gossypol in K836 treated with 2.5%and 5%PEG 6000 increased by 8.30%and 32.41%respectively compared with CK,the content of tannin increased by 18.93%and 39.32%respectively compared with CK.Therefore,abiotic stress such as salt and drought promoted the accumulation of cotton secondary metabolites such as gossypol and tannin.As the concentration of salt or drought stress increased,the contents of gossypol and tannin gradually increased.2.In order to determine the population growth and decline of T.cinnabarinus on cotton plants stressed with salt and drought,this paper investigated the occurrence of T.cinnabarinus on cotton seedlings.The development and fecundity of T.cinnabarinus on cotton seedlings under different concentrations of Na Cl and PEG 6000 were also studied.The results showed that,salt and drought stress inhibited the population growth and decline of T.cinnabarinus on cotton plants.With the increase of salt concentration,the number of mites on salinity and droughty stressed SCRC28 and K836 plants becomes lighter and lighter.The immature stage of T.cinnabarinus in salt-stressed and drought-stressed cotton plants was significantly extended,while the total amount of oviposition per female was significantly reduced,and the hatchability of T.cinnabarinus was significantly decreased.The immature stage of T.cinnabarinus in the leaves of SCRC28 treated with 50,100,150,200 m mol·L-1Na Cl increased by 2.93%,5.71%,9.31%,and 12.84%respectively compared with CK,the total amount of oviposition per female decreased by 7.54%,14.93%,22.57%,and 31.96%respectively,and the hatchability of eggs decreased by 4.52%,11.75%,14.91%,and 18.99%respectively.The immature stage of T.cinnabarinus in the leaves of K836 treated with 50,100,150,200 m mol·L-1 Na Cl increased by 2.03%,5.15%,6.25%and 11.94%,respectively compared with CK,the total amount of oviposition per female decreased by 1.80%,15.60%,26.91%and36.16%respectively,and the hatchability of eggs decreased by 3.53%,8.96%,11.50%,and 18.36%respectively.The immature stage of T.cinnabarinus in SCRC28 treated with 2.5%and 5%PEG 6000 increased by 6.13%and 16.47%respectively compared with CK,the total amount of oviposition per female decreased by17.77%and 41.43%respectively,and the hatchability of eggs decreased by 9.40%and 20.08%.The immature stage of T.cinnabarinus in K836 treated with 2.5%and 5%PEG 6000 increased by 3.62%and 10.07%respectively compared with CK,the total amount of oviposition per female decreased by15.73%and 31.96%respectively,and the hatchability of eggs decreased by 5.20%and14.45%.It can be seen that salt and drought stress affect the growth,development and reproduction of T.cinnabarinus,which is an important factor in reducing the occurrence of T.cinnabarinus.3.In order to find out the mechanism of population growth and decline of T.cinnabarinus on the cotton plant under salt and drought stress,the detoxification enzyme activity of T.cinnabarinus on the cotton leaves under different concentrations of Na Cl and PEG 6000 was measured,and the differential expression of the toxic enzyme genes was studied.The results showed that the Car E activity and P450 activity of T.cinnabarinus was significantly higher than that of the control,and the GST activity was not significantly different from that of the control(P<0.5).The Car E activity of T.cinnabarinus feeding on leaves of SCRC28 treated with 50,100,150 and 200 m mol·L-1 Na Cl were 1.70,2.46,3.30and 3.76 times the control,respectivel.The P450 activity were 1.51,1.92,2.22 and 2.55 times the control,respectivel.The Car E activity of T.cinnabarinus feeding on leaves of K836treated with 50,100,150 and 200 m mol·L-1 Na Cl were 1.10,1.36,1.77 and 2.05 times the control,respectivel.The P450 activity were 1.67,2.82,4.44,and 5.48 times the control,respectivel.The Car E activity of T.cinnabarinus feeding on leaves of SCRC28 under 2.5%amd 5%PEG 6000 stress was 1.77 and 3.38 times the control,respectively.The P450 activity was 1.57 and 2.58 times the control,respectively.The Car E activity of T.cinnabarinus feeding on leaves of K836 under 2.5%amd 5%PEG 6000 stress was 1.16 and 2.10 times the control,respectively.The P450 activity was 2.20 and 3.86 times the control,respectively.Analysis of the transcriptome sequencing results showed that the gene expression of T.cinnabarinus on SCRC28 treated with 200 m mol·L-1 Na Cl was 107 genes that were significantly different from the control.Among them,47 were up-regulated and 60 were up-regulated.Down.The expression of cytochrome P450 3A8 gene related to P450s and Gene9913 gene related to carboxylesterase were up-regulated.Compared with the control,the gene expression of T.cinnabarinus on SCRC28 treated with 5%PEG was compared with the control,and there were a total of 2466 significantly differentially expressed genes,among which 1907 were up-regulated and 559 were down-regulated.Gene9913 expression related to carboxylesterase was significantly up-regulated.Pathway analysis showed that the top five pathways for up-regulated gene enrichment were“Metabolic pathways”?“Lysosome”?“Bile secretion”?“Metabolism of xenobiotics by cytochrome P450”and“Antigen processing and presentation”.It can be seen that the Car E and P450s activities and related differentially expressed genes are involved in the detoxification metabolism of gossypol and tannin by T.cinnabarinus.4.To determine the relationships of abiotic stress with secondary metabolism and T.cinnabarinus population dynamics,the relationships between gossypol and tannin content of cotton plants under salt-stress and drought-stress and immature stage,total amount of oviposition per female,the Car E activity and P450 activity were analyzed.Correlation analysis indicated that the gossypol and tannin contents of each treatment were positively correlated with the immature stage of T.cinnabarinus,negatively correlated with the total amount of oviposition per female,positively correlated with the Car E activity and P450activity.Thus,abiotic stress such as salinity and droughty enhanced the secondary metabolism and increased accumulation of secondary metabolites such as gossypol and tannin,which finally inhibited the population dynamics of T.cinnabarinus.T.cinnabarinus can resist the toxicity of gossypol and tannin by increasing the activity of Car E and P450. |
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