Virus transmission efficiency: investigation on Chinese clone diversity of wheat aphids and role of aphid endosymbionts

Clone diversity in aphids (Hemiptera: Aphididae) was known to be related to acceptance and suitability of host plant. Occurrence of particular patterns of bacterial endosymbionts was demonstrated to specific plant – aphid interactions. Barley yellow dwarf virus (BYDY) has a high degree of vector specificity to be transmitted only by specific species of cereal aphids. BYDV and their aphid vectors are associated in a variety of complex interactions. In this context, the main objective of this dissertation was to understand the virus partners in host-aphid interactions, the role of endosymbionts pattern on virus transmission efficiency and (E)-β-farnesene (EBF) production.
Aphids were of closely association with bacterial endosymbionts; which substantially affect the physiology, ecology, reproduction and behaviors of aphids in a variety of way. Firstly, endosymbionts were selective eliminated by antibiotic, the EBF production was reduced; from the result of protein analysis, some protein from Buchnera aphidicola were found. It demonstrated that endosymbionts take part in the EBF production. Secondly, Fourteen populations of Sitobion avenae Fabricius (Hemiptera: Aphididae) originating from China were tested for their ability to transmit Barley yellow dwarf virus-PAV (BYDV-PAV, one isolate from Belgium, another from China) using wheat plants. All populations could transmit BYDV-PAV and variation in transmission rates ranged from 24.42% to 66.67% with BYDV-PAV-Belgium and from 23.55% to 56.18% with BYDV-PAV-CN. Significant differences of percentages of transmission between the populations with BYDV-PAV-Belgium and BYDV-PAV-CN were observed. Buchnera and seven S-symbionts (PASS, PABS, PAUS, Rickettsia, Spiroplasma, Wolbachia and Arsenophonus) universally found in different local population with different infection frequencies. The endosymbionts in most and least efficient vector aphid clones were selectively eliminated by antibiotic, the BYDV transmission efficiencies were inhibited. Compared with the result of western blot, Buchnera plays an import role on BYDV transmission. Finally, according to the direct toxic effect of lectins on insect biological parameters but also to the potential competitive effect of lectins towards viral particles in virus transmission by aphids, GNA and PSL incorporated in an artificial diet, the BYDV transmission efficiencies were inhibited. The inhibition rate of GNA-treatment reached to 46.63% in STY-BYDV-PAV-CN treatment and PSL-treatment was 46.47% in STY-BYDV-PAV-CN treatment. It is demonstrated that lectins represent a very promising protein to control aphid pest damages in crops.