Potential Involvement of Buchnera aphidicola (Enterobacteriales, Enterobacteriaceae) in Biotype Differentiation of Sitobion avenae (Hemiptera: Aphididae)

<i>Buchnera aphidicola</i>, an obligate endosymbiont of most aphid species, can influence aphids' host adaptability through amino acid metabolism, potentially mediating biotype differentiation. However, its role in the biotype differentiation of <i>Sitobion avenae</i> remains unclear. To address this issue, six <i>S. avenae</i> biotypes were tested in this study. <i>Buchnera</i> abundance varied among biotypes fed on different wheat/barley varieties (i.e., Zhong 4 wumang, 186-TM12-34; Dulihuang, Zaoshu No.3, Xiyin No.2). The reduction in <i>Buchnera</i> abundance through antibiotic (rifampicin) treatment altered the virulence of five <i>S. avenae</i> biotypes. Based on transcriptome analysis, the differential expression of three genes (i.e., <i>LeuB</i>, <i>TrpE</i>, and <i>IlvD</i>) related to leucine, tryptophan, isoleucine, and valine metabolism was detected between different biotypes. Principal component analysis showed that leucine and tryptophan deficiencies most significantly impacted nymph development duration and aphid fecundity. Additionally, a neighbor-joining phylogenetic tree indicated the genetic differentiation of <i>Buchnera</i> among different biotypes. These results suggest <i>Buchnera</i>-mediated amino acid metabolism is correlated with biotype differentiation in <i>S. avenae</i>, although the precise mechanisms by which <i>Buchnera</i> influences this differentiation require further investigation. This study can offer a theoretical basis for the development of resistant crops, leading to the sustainable control of this aphid and reduced reliance on chemical insecticides.