| Ginseng(Panax ginseng C.A. Mayer) is one of the earliest valuable medicine herb plants, the medicinal history of which has reached thousands of years.It has been known as the King of Herbs and gained popularity over the word. Ginseng is cultivated at a large area in China,its yield accounts for 70% of the total yield of the world. Ginseng has a long growing period, and from sowing to harvesting it will last about 4-6 years. Ginseng requires relatively rigorous soil and climate environments, and is easily infected by diseases, which will affect the final yield. Azoxystrobin, a strobilurin fungicide, is a new environmentally friendly fungicide of high efficiency, low toxicity and residue, and wide adaptability. It has a unique mechanism of action and strong absorption, with no cross resistance to other fungicides. Azoxystrobin can not only effectively control Basidiomycetes, Oomycetes Ascomycetes, and Alternaria panax whetz, but it is also safe to target organisms. Nowadays, no research on the effect of azoxystrobinon on ginseng growth has been found. Azoxystrobin on ginseng has been registered in China, and the maximum recommended dose is 225 a.i.g/hm2. In this study, field trial method was used, and five-year old Panax ginseng C.A. Mey. cv.(the cultivar of Ermaya) under natural environmental conditions during the growing season of 2013-2014 in Baishan city of Jilin province and Huanren Manchu Autonomous County of Liaoning province were chosen as test materials. When plants were at phenological growth stage [PGS] 800/909(All fruit green), 25% azoxystrobin SC plus water control was sprayed on the foliage in the plots from both sides until runoff. Azoxystrobin was sprayed three times at different concentrations(150 a.i.g/hm2 and 225 a.i.g/hm2) at 7 d intervals of each application. Ginseng plants of normal growth were selected as water control plot. Ginseng samples were collected at different growth stages to explore its effects on ginseng morphological indicators, physiological indicators and quality, and its molecular regulation mechanism was also discussed in order to provide a scientific way of reasonable application of azoxystrobin on ginseng. The results are shown as follows:1. A modified Qu ECh ERS rapid detection method was developed for the simultaneous determination of 42 pesticides in Panax ginseng. The method is simple and reliable. It provided reliable results in Baishan city of Jilin province and Huanren Manchu Autonomous County of Liaoning province in China. The results showed that: 42 pesticide residue concentrations were low, excluding the possible impact on subsequent study, and ensuring that all the results of the study were caused by the single pesticide of azoxystrobin.2. The research on the effects of azoxystrobin on ginseng morphologic indicators was conducted. The results showed that azoxystrobin had significant regulatory function to morphology of ginseng leaves, stems, roots and seeds, improved ginseng leaf color, brightness and seed color, significantly increased stem diameter, leaf width, ratio of ginseng root height and fruit shape index, and reduced plant height, and promotion or inhibition effect of the high-dose azoxystrobin treatment group was more obvious. Azoxystrobin treatment could delay ginseng plant aging for more than 14 d compared with water control. Compared with control, morphological changes of the specific indicators of azoxystrobin treatment are as follows: azoxystrobin in high dose(225 g a.i./hm2) and low dose(150 g a.i./hm2) treatments reduced the height of ginseng plants by 2.96% and 1.44%, increased stem diameter and leaf width by 55.21% and 26.04%, 18.53% and 9.18%, and increased the ratio of ginseng root height and fruit shape indicators 65.35% and 37.28%, 6.25% and 2.08%, respectively(Experimental results are the mean of the two places in two years).3. The research on the effects of azoxystrobin on ginseng physiological indicators was conducted. The results showed that azoxystrobin had significant regulatory function to physiological indicators of ginseng. The results indicated that azoxystrobin significantly increased the content of chlorophyll and soluble protein content in ginseng plant and enhanced resistance of plant and root, and it also inhibited the excessive growth of ROS and MDA in ginseng plants, and significantly increased SOD, CAT, POD and APX activity of antioxidant enzymes in ginseng plants and roots. Compared with control, specific physiologic indicator changes at [PGS]809/909(red fruits) are as follows: azoxystrobin in high dose(225 g a.i./hm2) and low dose(150 g a.i./hm2) treatments increased chlorophyll by 56.20% and 29.97% in leaves and 18.21% and 7.61% in stems, and increased soluble protein, SOD, CAT, POD and APX in ginseng leaves, stems and roots by 41.55% and 22.40%, 80.77% and 43.27% and 31.15% and 21.53%, and 128.36% and 89.28%, 116.50% and 88.45% and 55.27% and 33.59%, and 74.51% and 57.34%, 135.53% and 112.33% and 38.96% and 15.63%,and 57.42% and 24.22%, 19.43% and 3.53% and 99.50% and 74.17%, and 77.97% and 67.28%, 131.33% and 110.87% and 33.51% and 16.16%, respectively(Experimental results are the mean of the two places in two years).4. The research on the effects of azoxystrobin on ginseng quality was conducted. The results showed that azoxystrobin had significant regulatory function to quality of ginseng. Azoxystrobin significantly increased ginsenosides content in ginseng leaves, stems, roots and fruits, and two new fatty acids esters(ethyl linoleate and methyl linolenate) were first detected in ginseng stems by the application of azoxystrobin. It also significantly increased the content of vitamin E and tocopherol in ginseng roots, and greatly increased the soluble solids content of ginseng fruit. Compared with control, specific quality indicator changes at [PGS]809/909(red fruits) are as follows: azoxystrobin in high dose(225 g a.i./hm2) and low dose(150 g a.i./hm2) treatments increased ginsenosides content by 82.03% and 62.21%, 34.29% and 27.38%, 37.43% and 21.81% and 3.98% and 1.59% in ginseng leaves, stems, roots and fruits, increased vitamin E and tocopherol content by 16.67% and 5.01% of ginseng roots, and increased soluble solids content by 9.12% and 7.63%, respectively. The content of ethyl linoleate and methyl linolenate was 4.67 mg/g and 3.56 mg/g in ginseng stems(Experimental results are the mean of the two places in two years).5. The research on the effects of azoxystrobin on molecular mechanism of biosynthesis ginsenosides was conducted. The results showed that azoxystrobin had significant regulatory function to ginsenosides gene FPS, SQS, SQE and P450, and P450 is the most significant. The high dose and low dose treatments significantly increased the expression of genes, and the high dose treatment is more significant. Compared with control, specific gene expression changes at [PGS]809/909(red fruits) are as follows: azoxystrobin in high dose(225 g a.i./hm2) and low dose(150 g a.i./hm2) treatments increased ginsenosides gene FPS, SQS, SQE and P450 content by 133% and 129%, 125% and 119%, 137% and 125% and 272% and 162%, respectively, in ginseng roots(Experimental results are the mean of the two places in two years).This study confirms that azoxystrobin can control ginseng disease effectively, optimize the morphological indicators, physiological indicators, delay senescence of ginseng, increase ginsenosides content and improve the quality of ginseng. It also explores the molecular mechanism with which azoxystrobin can improve ginsenosides content. This study suggests that azoxystrobin is of great theoretical and practical value. It provides basis for the study of ginsenosides biosynthesis and regulation of molecular mechanisms, and technical support for the ginsenosides industrialization. |
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