Resistance Mechanism Of Wheat Cultivars To Wheat Bloom Midge Sitodiplossis Mosellana Gehin

The wheat blossom midge, Sitodiplosis mosellana Gehin, is one of the intermittentlydisastrous insect pests injuring wheat. Two times of broad and disastrous damages wererecorded in China history in1950’s and1980’s respectively. In recent yspikes, there is aobvious trend extending of wheat blossom midge distribution. Therefore, the potential threatof the wheat blossom midge to the wheat production did not disappspike. It has been foundthat planting resistant culitivar is the most economical and effective way to control damage.In this paper,86cultivars resistant to Sitodiplossis mosellana were evaluated in the field,clspikeed the stable resistance cultivars; the morphological traits of different resistance levelswere analyzed statistically, and the total phenols, ferulic acid, tannins, flavonoids and solublesugar content in wheat grains of different resistance levels were measured and correlationanalysis of inclusion contents with midge resistance were made to explore mechanism ofresistance of wheat cultivars to wheat bloom midge. It is the first time to analysis the spatialpattern of larvae on the spike of cultivars in different resistance levels, explored the resistanceperformance from different angles. The present resspikech will provide a foundation foridentifying resistance wheat cultivars and theory warranty for breeding of wheat resistance towheat midge and integrating wheat midge management. The main results were as follows.(1) Identification of resistant wheat cultivarsResistant to Sitodiplossis mosellana of86cultivars were evaluated in the field. Theresults showed that there was significant difference in resistance to wheat bloom midgebetween different cultivars. Among the all of evaluated cultivars,2cultivars were highlyresistant to wheat midge, only about2.35%of all cultivars.4cultivars,4.71%of all, havemoderate resistance，and19cultivars,22.35%of all, were low resistant. There were25cultivars, about29.41%of all cultivars, were resistance.60cultivars,70.59%of all, weresusceptible to wheat midge.(2) Relationship between different resistant indicatorsThe relationship between the quantity of wheat bloom midge in every spike, infect rate,losing rate and resistant index were found that were significant at0.01level. The coefficientof percentage of infested grain with resistant index was0.8863, the highest. The coefficient ofPercentage of infested spike with resistant index was lowest,0.4964. The mean coefficient of percentage of infested grain between other resistant indicators was0.7172, the highest. Thecoefficient of Percentage of infested spike with between other resistant indicators was thelowest,0.5123.(3) Relationship between the resistance and morphological characters8morphological characters of spike were measured and liner regression analyzed withresistance index of wheat cultivars. The result showed that the thickness of shell indicated aclspike negative correlation with the resistance index to wheat midge. The thickness of shellincreased with the increase of resistance of wheat cultivars to what midge. The correlationbetween resistance index and other morphological characters were insignificant.(4) Relationship between the resistance and metabolic charactersThe contents of total phenols, ferulic acid, tannins, flavonoids and soluble sugar contentin grains of12wheat cultivars of different resistance were measured and analyzed. The resultshowed that there was significant difference between different cultivars. The content offerulic acid indicated a clspike negative correlation with the resistance index to wheat midge（P <0.05）. The content of tanning indicated a negative linspike correlation with theresistance index to wheat midge, close to significant（P=0.0507）. The correlation betweenresistance index and other metabolic characters were insignificant.(5) Spatial distribution pattern of larvae of wheat midge in the spikeSpatial distribution pattern of wheat midge larvae in the spike of86cultivars wereanalyzed and it was founded that the number of larvae on different part of spike of resistantcultivars were insignificant, the number of larvae on lower part of spike was significanthigher than other part of wheat spike. Spatial distribution pattern of wheat midge larvae on allcultivars and all part of spike belonged to aggregation distribution. According the aggregationindex, middle part was the most aggregative part on resistant cultivars, and upper part was themost aggregative part on susceptible cultivars.