Study On Relationship Between Evaluation On Alfalfa Tolerance To Pest And Fall Dormancy

Insect resistance is a characteristic refers to when some varieties under the samenumber pests as the susceptible varieties, still can output good quality and highyield. Alfalfa fall dormancy is a growth characteristic, because of the autumn temperaturedrop and light reduction, result the alfalfa morphological type and production performancechange. In this paper, through theoretical research on alfalfa tolerance and fall dormancyrelevant information, and observed different fall dormancy alfalfa varieties’ growthdynamic in field and greenhouse, proposed the relationship between alfalfa tolerance topest evaluation and fall dormancy, investigated the technical standard of evaluatingdifferent fall dormancy alfalfa varieties’ tolerance to pest, found the period and thestandard of evaluating alfalfa fall dormancy class in Lanzhou, with a view to the futureprovide the basis for the correct evaluating alfalfa tolerance to pest and insect resistantbreeding. This is the first research on concepts junction of the alfalfa tolerance to pest andfall dormancy. The main research contents of this thesis are as follows:1.The evaluating standards of alfalfa fall dormancy in LanzhouThe fall dormancy levels of11different alfalfa cultivars were evaluated by measuringits fall regrowing height,the study in order to determine the evaluating criterion of the falldormancy in Lanzhou, and evaluated the fall dormancy class of G5、Cossack and sun-god.The results showed that the measuring stage for alfalfa fall dormancy in Gansu Provinceare: the considerable cutting period was suggested in early September and the measuringperiod of regrowing height was suggested in early October; G5、Cossack and sun-god’sfall dormancy class are11、3and7, respectively.2．The evaluating standards of alfalfa tolerance to pestWhile evaluating the tolerance of alfalfa varieties to pests, such as thrips, plantsheight difference can be used as the character index，but the plant height difference is alsoused as the character index to evaluate the alfalfa varieties’ fall dormancy class. In order to get an accurate evaluation of alfalfa tolerance to pests, the misjudgment caused by falldormancy must be avoided. In this experiment, the plant height dynamic of11alfalfavarieties with different fall dormancy classes were observed in Lanzhou field and in thegreenhouse. The results showed that in Lanzhou field, the best period of evaluatingdifferent fall dormancy class alfalfa varieties’ tolerance to pest was from early August toearly September. During this period, the average temperature of air was higher than19.5℃, sunshine time of day was longer than13.5h, the plant growth height of differentalfalfa varieties with different fall dormancy classes had no significant differences（P<0.05）, errors will be not produced by the fall dormancy. In the greenhouse, while thetemperature of air were21℃,25℃,sunshine hours of day were13.5h,15h, the plantgrowth characteristics of different fall dormancy class alfalfa varieties were not significant（P<0.05）.These conditions were suitable for evaluating alfalfa tolerance to pest. Basedon the comprehensive analysis, the temperature of air was higher than21℃, sunshinetime of day was longer than14h, these conditions were best suitable for evaluating alfalfavarieties’ tolerance with different fall dormancy to pests in field and indoor as the index ofplant height difference.3. Evaluation on tolerance to thrips of different fall dormancy alfalfa varietiesIn order to investigate the relationship between alfalfa tolerance to thrips and falldormancy, evaluated the tolerance to thrips of different fall dormancy alfalfavarieties using plant height difference as the index. The results showed that, the toleranceof G5is the strongest, with the rising of fall dormancy rate the tolerance to thripsenhanced.