Plant-mediated Interspecific Interaction Between Aceria Pallida And Bactericera Gobica

The gall mite,Aceria pallida Keifer,and the psyllid,Bactericera gobica Loginova are two destroy concomitant pests of goji berry,Lycium barbrum L.,which feed and live on the foliage.As occupying similar niches in the growing season,they are likely to be competitors for plant resources.However,in contrast with other herbivorous mites that hibernate on host plants,A.pallida is a phoront that is obligately phoretic on B.gobica for overwintering.Undoubtedly,the gall mite benefits from the psyllid during hibernation,but the influence of the the gall mite on its vector is unclear.Because gallmakers can manipulate host plant metabolism and construct galls to amass nutrients,they are more likely to be superior competitors when competing with other herbivores.As a gall maker,how the obligate phoretic mite A.pallida interacts with its vector B.gobica during the growing season to achieve phoresy is unclear.In addition,it is unknown whether the vector obtains some benefits at the cost of carrying the mite after detachment.Here,the basic biology and the interspecific interaction between the gall mite and the psyllid were studied.The materials that influenced their interaction was studied via measuring host plant physiological and biochemical indexes and transcriptome.And the effects of SA on the infestation and development of the mite was studied.The main results were shown as follows:1.The living habits of B.gobica and A.pallida were further clarified.B.gobica adults often aggregated abaxial foliage with their heads facing petiole;nymphs excreted honeydews by swing their abdomens,and their body length growth rate was 51.6%.A.pallida often cooperated with each other to invade tender tissues;the suitable temperature and relative humidity for the mite infestation and development were 25? and 60%RH,repectively;and neither lower temperature nor high humidity were suitable for the mite infestation.2.The commensalism mechanism of the phoretic association between A.pallida and B.gobica was preliminarily clarified from their biological level.Our laboratory results showed the mortality and development duration of psyllid nymphs were increased on the seedlings infested with the gall mite.Meanwhile,the growth of the mite gall and the mite population were also adversely affected.Our field results showed that the infestation of the gall mite and the psyllid had detrimental effects on mutual population growth.However,the competition decreased rather than accelerated foliage defoliation caused by the psyllid,which was conductive to the persistence of the psyllid population,and then indirectly contributed to the phoretic association.Our results suggested that the plant-mediated competition between the phoretic gall mite and its vector after detachment facilitated the phoretic association.3.The materials that influenced the interspecific interaction between A.pallida and B.gobica was preliminarily identified from plant physiology.After the gall mite infestation,the contents of soluble sugar,total phenols and flavonoids,and the activities of POD,PAL and PPO in host plant foliage were increased.However,the percentage of C and the ratio of C/N were declined.After the psyllid infestation,the contents of soluble sugar,total phenols and flavonoids,and the percentage of C and N in host plant foliage were declined;the ratio of C/N was increased;and the activities of POD,PAL and PPO were not induced.After the gall mite and the psyllid infestation,the contents of soluble sugar,total phenols and flavonoids,and the percentage of C and N were declined;and the activities of POD,PAL,PPO were increased.Our results suggested that the gall mite competed with the psyllid via inducing plant defences,and the psyllid competed with the gall mite via decreasing plant nutrition.4.The molecules that influenced the interspecific interaction between A.pallida and B.gobica were preliminarily identified from plant transcriptome.After the gall mite infestation,the SA-mediated defense genes and the key enzyme genes in plant secondary metabolism pathway were up-regulated compared with non-infestation plants.However,the mite infestation had little influence on the genes' expression in JA,plant photosynthesis,tetrapyrrole and mitochondrial e-transport pathways.Ater the psyllid infestation,the negative regulatory genes in the SA and JA pathways and the genes in plant mitochondrial e-transport pathway were up-regulated;the genes in plant photosynthesis and tetrapyrrole pathways and the key genes in plant secondary metabolism pathway were down-regulated;and the SA-and JA-mediated defense genes were suppressed.After mixed-species infestation,the negative regulatory genes in plant SA and JA pathways,the genes in plant mitochondrial e-transport pathway and the key genes in secondary metabolism pathway were up-regulated;the genes in plant photosynthesis and tetrapyrrole pathways were down-regulated;and the SA-and JA-mediated defense genes were suppressed.Our results suggested that the gall mite induced plant SA defense and plant secondary metabolites'synthesis;the psyllid infestation led to plant nutrition reduction and suppressed plant SA-and JA-mediated defenses and plant secondary metabolites' synthesis;and mixed-species infestation led to plant nutrition reduction and JA-mediated defenses' suppression,and stimulated plant secondary metabolites' synthesis.5.The effects of exogenous SA on the infestation and development of A.pallida were clarified.Exogenous SA had no influence on the gall mite infestation,but could suppress the growth of galls and mite population.However,the negative effects were not enhaced when SA concentration was beyond 0.5 mmol/L.This study preliminarily revealed the mechanism of the commensalism relationship between A.pallida and B.gobica,and found that A.pallida could manipulate host plant metabolism to compete with B.gobica in the growing season,and the plant-mediated competition could facilitate the phoretic association between them.The results provided scientific basis for revealing the co-evolutionary relationship among L.barbarum,A.pallida and B.gobica and their prevetion.