| The whitefly Bemisia tabaci(Hemiptera:Aleyrodidae)is influenced by many factors,such as the external stress factor,the host plant and so on.Atmospheric ozone(O3)was considered as greenhouse gas(contributing to global warming)and as air pollution has been continuously increased from less than 10 ppb(parts per billion)a century ago to 40 ppb today.Tomato yellow leaf curl virus(TYLC V)is transmitted by the whitefly in a persistent circulative manner.This virus has devastated tomato production in a part of China and is frequently found on tomatoes in areas where B.tabaci occurs.Whitefly is one of the most destructive pest insects,has been regarded as a species complex composing of at least 24 morphologically indistinguishable species.Among these,Middle East-Minor Asia 1 genetic group(well known as biotype B)and Mediterranean genetic group(well known as biotype Q)are the most two invasive and widely distributed biotypes(putative species).Although both biotypes have wide host ranges,MEAM1 and MED differ in host suitability.In the present study,we compared the effects of external stress factors(including elevated O3 and TYLCV)and host plants on whitefly Bemisia tabaci.(1)The effects of elevated atmospheric ozone(O3)levels on herbivorous insects have been well studied,but little is known about the combined effects of elevated O3 and virus infection on herbivorous insect performance.Using open-top chambers in the field,we determined the effects of elevated O3 and Tomato yellow leaf curl virus(TYLCV)infection on wild-type(Wt)tomato and 35S tomato(jasmonic acid(JA)defense-enhanced genotype)in association with whitefly,Bemisia tabaci Gennadius biotype B.Elevated O3 and TYLCV infection,alone and in combination,significantly reduced the contents of soluble sugars and free amino acids,increased the contents of total phenolics and condensed tannins,and increased salicylic acid(SA)content and the expression of SA-related genes in leaves.The JA signaling pathway was upregulated by elevated O3,but downregulated by TYLCV infection and O3 +TYLCV infection.Regardless of plant genotype,elevated O3,TYLCV infection,or O3 + TYLCV infection significantly decreased B.tabaci fecundity and abundance.These results suggest that elevated O3 and TYLCV infection,alone and in combination,reduce the nutrients available for B.tabaci,increase SA content and SA-related gene expression,and increase secondary metabolites,resulting in decreases in fecundity and abundance of B.tabaci in both tomato genotypes.(2)The performance of herbivorous insects is greatly affected by host chemical defenses and nutritional quality.Some herbivores have developed the ability to manipulate plant defenses via signaling pathways.It is currently unclear,however,whether a herbivore can benefit by simultaneously reducing plant defenses and enhancing plant nutritional quality.Here,we show that the better performance of the whitefly Bemisia tabaci Middle East-Asia Minor 1(MEAM1;formerly the "B"biotype)than Mediterranean(MED;formerly the "Q" biotype)on cabbage is associated with a suppression of glucosinolate(GS)content and an increase in amino acid supply in MEAM1-infested cabbage compared with MED-infested cabbage.MEAM1 had higher survival,higher fecundity,higher intrinsic rate of increase(rm),a longer life-span,and a shorter developmental time than MED on cabbage plants.Amino acid content was higher in cabbage infested with MEAM1 than MED.Although.infestation by either biotype decreased the levels of total GS,aliphatic GS,glucoiberin,sinigrin,glucobrassicin,and 40H-glucobrassicin,and the expression of related genes in cabbage,MED infestation increased the levels of 4ME-glucobrassicin,neoglucobrassicin,progoitrin,and glucorapheane.The GS content and expression of GS-related genes was higher in cabbage infested with MED than with MEAMI.Our results suggest that MEAM1 performs better than MED on cabbage by manipulating host defenses and nutritional quality. |
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