| Sitobion avenae (Fabricius), Hemiptera, Aphididae, is one of the most importantagricultural pests in the whole world. One of internal factors of widely harm is polarization ofbody-color morphs (red and green morphs) in species caused by the change of environment.As the selective stress, the change of environment accelerates the evolution of S. avenae.Based on previous researches, to explore the ecological mechanism of polarization ofbody-color morphs, the development, reproduction and intraspecific competition of twomorphs of S. avenae were estimated under the condition of UV-B, aposymbiosis, plant viruses(CYDV-PRV and WDV) in this study. Under these conditions, the research on feedingbehavior was also carried out by Electronical Penetration Graph (EPG). The following are theresults of this research:1. UV-B radiation directly is one of the driving forces for the polarization of body-colormorphs of S. avenaeThe parameters of development, fecundity and feeding behavior of S. avenae wereestimated after radiating the first instar nymphs of body-color morphs by UV-B in differentdose (0,216,432,864kJ/m~2). The results indicated that, the development and fecundity werepromoted by low-dose UV-B (216kJ/m~2), and effected negatively by high-dose UV-B (432，864kJ/m~2). For red aphids, the capacity of adaptation to this was stronger than green aphids.Trough determining the feeding behavior by EPG, we could demonstrate that: radiation ofhigh-dose UV-B not only restrained the feeding in phloem but also prolonged the prickingtime in the part of cuticle and mesophyll. The fact that the feeding behavior of green aphidspricking host plant cuticle and phloem was more difficult than that of red aphids demonstratedthat red aphids was the evolutionary biotype to adapt the UV-B.2. The indirect effects on S. avenae through radiating host plant by UV-B is anotherdriving force for the polarization of body-color morphsThe parameters of development, fecundity and feeding behavior of S. avenae wereestimated after radiating barley by UV-B in different dose (0kJ/m~2as the control,600kJ/m~2as normal UV-B radiation, double-dose UV-B is1200kJ/m~2). The results indicated that: thedevelopment and fecundity of two body-color morphs were restrained significantly under thecondition of radiating post plant by double-dose UV-B. It could include that two types of aphids had adapted post plants exposed to the normal UV-B radiation. For Red aphids, thecapacity of adaptation to this was stronger than green aphids. The result of feeding behaviorcould indicate that cuticle resistance, mesophyll resistance and phloem resistance of two typesof S. avenae were all increased under the condition of double-dose UV-B radiation. Moreover,the resistance of post plant to green aphids was higher than the Red aphids exposed to threetreatments, which further demonstrated that red aphids demonstrated that red aphids was theevolutionary biotype to adapt the UV-B.3. Aposymbiosis in S. avenae plays an important role in the polarization course ofbody-color morphsThe parameters of development, fecundity and feeding behavior of S. avenae wereestimated after disrupting symbiotic bacteria from aphids by rifampicin which was one kindof antibiotics. The results indicated that: the development and fecundity were influencednegatively for the two morphs Bacteria-free aposymbiotic aphids. The influence ofaposymbiosis to Red aphids was more serious than green aphids. It was demonstrated fromthe result of feeding behavior that the feeding of two morphs aphids was restrained, such as,pricking time in the part of cuticle and mesophyll was prolonged and the time of feeding inphloem was shortened. Furthermore, the feeding behavior of Red aphids was more difficultthan that of green aphids. It was indicated that aposymbiotic involved in the polarizationcourse of body-color morphs of S. avenae.4. The non-transmission plant virus could affect polarization of body-color morphs of S.avenaeThe development and fecundity of two body-color aphids could be promoted afterinfecting host plant (barley) successfully by non-propagative CYDV-PRV and WDV. Theeffect on green aphids was stronger than the red aphids. The result of feeding behavior couldindicate that cuticle, mesophyll and phloem resistance to two types of S. avenae were alldecreased by non-propagative CYDV-PRV and WDV. Moreover, the phloem resistance ofhost plant infected viruses to green aphids was lower than the red aphids. Therefore thenon-transmission plant virus plays an important role in the polarization course of body-colormorphs.5. The population competitiveness of two body-color morphs of S. avenae induced byenvironmental stress could influence polarization of body-color morphsThe parameters of development and fecundity of S. avenae were estimated through risingseparately and mixed in the host plants exposed to the treatments of control, double-doseUV-B radiation and CYDV-RPV virus. The results indicated that: in the treatment of control,the competitiveness of two body-color morphs had not significant difference. UV-B radiation could generate stronger competitiveness for green aphids. However, the red aphids had highercompetitiveness under the induction of plant viruses. It could demonstrate that environmentalstress could influence polarization of body-color morphs through affecting populationcompetitiveness of two body-color morphs of S. avenae.In short, the adaptation and competitiveness of two body-color morphs of S. avenae weredifferent significantly under the environmental stress. The effect and the ecologicalmechanism were also various based on the different environmental factors. We candemonstrate that environmental stress is the main cause of polarization of body-color morphs,which has the important significance for exploring the mechanism of polarization and providethe theoretical basis for the management of S. avenae and plant virus under the condition ofever-changing environment.The innovations are following in this study:1. We demonstrate that UV-B radiation and plant virus were the driving forces for thepolarization of body-color morphs of S. avenae.2. It was demonstrated that aposymbiosis in S. avenae played an important role in thepolarization course of body-color morphs.3. The ecological mechanism of polarization of body-color morphs of S. avenae wasproposed.4. The conclusion that UV-B radiation could generate stronger competitiveness for greenaphids and the red aphids had higher competitiveness under the induction of plant viruses wasobtained in this research. |
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