Evaluation And Identification Of Sitobion Miscanthi(Takahashi)(Hemiptera: Aphididae)Resistance Sources From Spring Wheat Germplasm Accessions In Ethiopia And China

Wheat is the most important food crop in the world.China is the world's largest producer of wheat and contributes vital role in the world market.Ethiopia also one of the leading producers of spring wheat in Sub-Saharan Africa.Grain aphid,Sitobion miscanthi(Takahashi)causes severe damage by removing nutritional contents and transmission of viral diseases to wheat plants.Wheat producer usually use insecticide to control aphid,but overused of insecticide results in insecticide resistant and environmental pollution.The drawbacks of chemical insecticides use needs to search for an alternative approach.Deploying aphid resistant wheat cultivars that reduces aphid population is recognized as the most economic and environmental-friendly strategy.However,there is shortage of wheat cultivars resistant to S.miscanthi.In our study,one hundred and thirty-six spring wheat accessions collected from different localities of Ethiopia and China to identifying new wheat cultivars resistant to S.miscanthi.To identify S.miscanthi resistant wheat cultivars,different approaches such as antibiosis and antixenosis resistance screening on 114 Ethiopian and 22 Chinese spring wheat accessions,aphid bioassay for further antibiosis and antixenosis resistant test,aphid feeding behaver using electrical penetration graph(EPG),phenolic acid content analyses by HPLC and imaging of leaf trichome densities using 3D microscope were applied.Among 136 wheat accessions screened,2 high,27 moderate,and 35 low antibiosis resistant wheat accessions against S.miscanthi were identified.The antibiosis resistance test showed prolonged pre-adult and pre-reproductive period,shorter reproductive period,lower fecundity,intrinsic rate of increase(r_m)and finite rate of increase(?)of S.miscanthi on Lunxuan145,Wane,Lunxuan6,204511,Lunxuan103 and 5215 than those on the aphid-susceptible accession Beijing 837.The changes for parameters of aphid feeding behavior,including spending a longer time in the penetration and phloem salivation phases and less time in the phloem sap-feeding phase on the resistant wheat accessions,indicated that the aphid resistance may occur during the phloem phase and may be due to difficulties in the mechanical probing of the mesophyll cells.Additionally,the HPLC analysis showed higher contents of 1)ferulic acid in Lunxuan145,Lunxuan103 and Lunxuan6;2)p-coumaric acid in Lunxuan145;3)vanillic acid in Lunxuan145,Wane and Lunxuan6;4)syringic acid in Lunxuan103;and 5)caffeic acid in 5215.The contents of some phenolic acids within wheat leaves,such as p-courmaric acid and vanillic acid showed significant positive correlation with the aphid development times,but negative correlation with the aphid fecundity.The concentrations of these acids may be the causes of antibiosis resistance to S.miscanthi.According to the results of antixenosis resistance screening,1 highly,25 moderately and 38 lowly resistant to S.miscanthi were identified.Aphid bioassay for choice settling tests showed that Luxuan266,243726and 213312 were the least preferred after 12,24,48 and 72 hours of S.miscanthi released.The EPG result shows relatively longer duration of Np,time to 1^st probe and shorter duration of E2 waveforms on Lunxuan266,243726and 213312 than Beijing 837.The number of winged S.miscanthi settled on the wheat seedlings after 12,24,48and 72 hours were negative correlation with the durations of Np and E1 waveforms,but showed positively correlated with the duration of E2 waveforms.Trichome density on adaxial leaf surface of Lunxuan266,243726and 213312,and abaxial leaf surface of Lunxuan266 and 243726 were significantly higher when compared with aphid-susceptible variety Beijing 837.And,number of winged aphids settled on the wheat accessions showed negatively correlated with trichome density of wheat leaves.We concluded that Lunxuan266,243726 and213312 were antixenosis resistant to S.miscanthi based on the choice test,EPG results and leaf trichome densities.The grain aphid-resistant wheat accessions identified in our study,after S.miscanthi resistance test in the field,will be helpful to pest control by resistant wheat layout,then breeding program in future.