Resistance Assessment Of Cabbage Cultivars AndHerbivores Induced Volatiles Released From CabbageCultivars Affects Host Selection Behaviour Of GreenPeach Aphid,(Hemiptera:Aphididae)

The green peach aphid,Myzus persicae(Sulzer)(Hemiptera:Aphididae),is an important pest of many crops in the world,and a vector of more than 100 plant viruses.The green peach aphid is a major pest of Brassica vegetables such as the Chinese cabbage in northern China.Chemical control is extensively used to manage this aphid around the world;however,development of insecticide resistance has been a major obstacle facing growers.Host plant resistance in the Chinese cabbage against M.persicae has not been reported yet.Moreover,plants emit volatile organic compounds(VOCs)in response to herbivore attack and host selection.VOCs emitted from the Chinese cabbage cultivars in response to the damage by the green peach aphid,M.persicae,were unknown.In this study,we investigated the resistance categories in seven Chinese cabbage cultivars and impact of volatile organic compound released from these cabbage cultivars(intact and aphid infested cabbage cultivars)on host selection behaviour against M.persicae.The resistance categories of these cultivars include antixenosis,antibiosis,and tolerance related to leaf color and wax content,using a solid-phase micro extraction-based headspace collection method,we investigated and compared the emissions of VOCs from seven Chinese cabbage cultivars(Qibao,Qingan 80,Lvlong,Yuanbao,Qingan 70,Jinlv,and Lvqiu 66)in response to M.persicae attack.Our results showed that,Yuanbao cultivar had antibiotic and tolerance effects on the aphid.The rate of intrinsic increase(r_m)of M.persicae was lower on Yuanbao compared to the other cultivars.Yuanbao also had the highest level of antibiosis against the aphid.In term of preference,the aphid preferred Qingan 80,which had the highest wavelength(green)in leaf colour.Yuanbao had a significantly negative correlation with the preference of M.persicae and it may be related with the highest wax content in Yuanbao.However,VOCs emitted from the cultivars Qingan 80 and Yuanbao differed significantly from the other cultivars in response to the attack of wingless M.persicae.Most importantly,out of the 27 detected compounds,caryophyllene was detected only in Qingan 80 and Qibao,but not in the other five cultivars.Among the compounds detected,2 green leaf volatiles(GLVs)and 12 terpenes were predominant in all cabbage cultivars.We report qualitative and quantitative differences in herbivore-induced plant volatile blends from both intact and infested cabbage cultivars after aphid infestation.The volatile blends of infested cabbage cultivars are dominated by terpenes and green leaf volatiles.Overall,aphid-infested plants release more volatiles than intact plants.Caryophyllene was the only compound detected in both intact and infested Qingan 80(QG 80)and Qibao(QB)cultivars.Furthermore,the wingless M.persicae showed preference to Qingan80,perhaps because it had the highest nitrogen content among the tested cultivars.Moreover,we found a remarkable relationship among M.persicae attraction,plant nitrogen content,and total volatile emissions.Nitrogen content of the plants had a significant impact on volatile emission and preference behaviour of M.persicae.This study will be helpful in understanding aphid host selection,and sets a stage to further study the attractant-based integrated aphid management programs.