| Polyphagotarsonemus latus (Banks) is a kind of pandemic harmful mites, also a kind of important national vegetable harmful mites, which do serious harm to more than30families and more than70species of plants such as eggplant, pepper, bean, sponge gourd, cucumber, radish, etc. The plague of the mites often causes the decline in quality and production of peppers,resulting in major economic losses increasing year by year.In China, the researches on the anti-mite measures of peppers were lately started, and the main antiacarien property identification methods of different peppers include leave hazard index method, mite-ratio method, life parameter methods, etc, and these methods have many advantages but some defects and deficiencies as well. At present, some scholars have made related researches on relationship between pepper leaf nutrients and the anti-mite property, however, the in-depth researches on the relationships between the protective enzymes and some secondary metabolites and their anti-mite properties.In order to meet the needs of the researches on pepper anti-mite properties, and seek the quick and easy method of resistance determination and explore the relationship between secondary metabolites and screening of the anti-mite properties, the author of this paper carried out a outdoor anti-mite property identification and screening of31pepper varieties from different regions, and determined antibiosis and repellency of anti-polyphagotarsonemus latus properties of the screened6pepper varieties with the difference of anti-mite properties, and studied the relationships between a number of biochemical substances in pepper leaves and the anti-mite property, the results are as follows:1. Primary field screening of anti-polyphagotarsonemus latus properties of pepper varietiesTo carried out anti-mite identification of31pepper varieties adopting leave hazard index method, mite-ratio method, a variety with high anti-mite property was found:Paojiao No.1;3highly susceptible varieties:DufengNo.5, Tiaojiaoxinxiu and Techangxianglaerjingtiao.The results of the two kinds of identification methods reach a contact ratio of74.19%. Through the analysis of the linear correlation, the author finds a highly significant positive correlation (P<0.01) between leaf hazard index (x) and mite-ratio (y), and the correlation coefficient was r=0.9508(y=6.5654x-0.7402).2. Antibiosis and repellency determination of anti-polyphagotarsonemus latus properties of pepper varietiesTaked the6different infection-resistant varieties as tested materials, the author determined the antibiosis and repellency of anti-polyphagotarsonemus latus properties of pepper varieties, the results showed that the Paojiao No.1identified as a highly resistant variety by the field screening had the highest antibiosis and repellency of anti-polyphagotarsonemus latus, while Mexico Pepper, Jingxuantedaniujiaowang and Techangxianglaerjingtiao showed a relatively poor antibiosis and repellency, and the latter has the lowest antibiosis, and the former has the lowest repellency. In the test, the anti-mite properties of the six pepper varieties were collaborative ly controlled and regulated by the antibiosis and non-selective property.3. Relationship between pepper leaf protective enzyme activity and anti-mite propertyTaked the6different infection-resistant varieties as tested materials, the author studied the relations between the four kinds of protective enzymes activities of pepper leaves and the anti-mite properties of the varieties. Before feeding mites, the difference between the pepper leaf SOD and POD activities of the infection-resistant varieties and the susceptible varieties was not significant (P>0.05), the CAT and PAL activities of anti-mite varieties were very significantly higher than the activities of mite-susceptible varieties (P<0.01). After7days and14days of feeding the mites, the SOD and POD activities of the pepper leaves increased with the increase in the time of feeding the mites,respectively; while the CAT activity decreased after7days of feeding the mites. After21days of feeding the mites the SOD and POD activities of the pepper leaves decreased obviously, even lower than the activities before feeding the mites; while the CAT activity showed an upward trend. After feeding the mites, the change of leaf PAL activity was more complex: after7days and14days of feeding the mites, the PAL activities of the resistant varieties increased with the increase in time, while the PAL activities of the mite-susceptible varieties showed a downward trend; after21days of feeding the mites, the PAL activities of resistant varieties leaves began to decline, while the PAL activities of mite-susceptible varieties began to rise. The analysis of linear correlation showed that after feeding the mites, there was a significant negative correlation (P<0.05) between the average increase rate of the POD and PAL activities (x) and leaf hazard index (y), and the correlation coefficients were r=-0.8353(y=-0.0818x+0.4327), r=-0.8762(y=-0.0883x+0.5517), respectively, and after feeding the mites, there was a significant negative correlation (P<0.01) between the average increase rate of SOD and CAT activities (x) and leaf hazard index (y), and the correlation coefficients were r=-0.9035(y=-0.2376x+0.6424), r=-0.9342(y=-0.4716x+0.6337), respectively. The above results showed that the overall trend of the four kinds of protective enzyme activities was related to the damage inducement of harmful mites, and the size of the inductivity increases with the increase in the resistance level of the pepper varieties.4. Relationship between pepper leaf secondary metabolites and anti-mite propertyTaked the6varieties as tested materials, the author studied the relationship between the contents of pepper leaf secondary metabolites and the anti-mite properties of the varieties. In the7days before feeding the mites and the7days after feeding the mites, no capsaicin was detected in the pepper leaves, after14days and21days of feeding the mites, there appeared change of leaf capsaicin content and the differences between varieties, but no significant correlation between the change and the anti-mite property of pepper(P>0.05). Analyzing the linear relationship between the average content of leaf capsaicin (x) after21days of contacting mites and leaf hazard index (y), it was found that the correlation coefficient between the two is only r=-0.2272(y=-0.151x+0.4696), indicating that the relationship between content of capsaicin and the anti-mite property of pepper is not significant (P>0.05).While researching the relationship between the contents of pepper leaf polyphenol and tannin and the anti-mite property of pepper, it was found that before feeding the mites, both the contents of polyphenol and tannin in pepper leaves showed differences between varieties. And after feeding the mites, the content changes of polyphenol and tannin in pepper leaves were similar to each other:after7days of feeding the mites, the contents of polyphenol and tannin in the leaves of mite-resistant varieties increased comparing to the contents before feeding the mites, and the rate of increase rise with the increase in the anti-mite properties of the varieties, while after14days and21days of feeding the mites,the content of phenols begans to decline;the content changes of polyphenol and tannin in the leaves of mite-susceptible varieties were just contrary to the anti-mite varieties. Carried out,respectively, linear analysis of the average contents of polyphenol and tannin in pepper leaves before contacting mites (x) and leaf hazard index (y), it was found that there was a significant negative correlation (P<0.05) between the two, and the correlation coefficients were r=-0.8410(y=-0.1263x+0.9814), r=-0.8714(y=-0.153x+0.8918), respectively, which showed that there was a positive correlation between the contents of different varieties of phenols in leaves before feeding the mites and the resistance levels of the pepper varieties, which wasa constitutive resistance. Analyzing the linear correlation between the average contents of polyphenol and tannin in pepper leaves after21days of feeding mites (x) and leaf hazard index (y), it was found that there was a extremely significant negative correlation between the two (P<0.01), and the correlation coefficients were r=-0.9826(y=-0.7261x+0.9311), r=-0.9133(y=-0.6157x+0.8217), respectively, which showed that the content change of the phenols in the leaves after feeding the mites was related to the damage inducement of harmful mites, and the size of the inductivity increased with the increase in the resistance levels of the pepper varieties. |
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