Background: Leaf-associated microbes play an important role in plant development and response to exogenous stress. Insect herbivores are known to alter the phyllosphere microbiome. However, whether the host plant’s defense against insects is related to the phyllosphere microbiome remains mostly elusive. Here, we investigated bacterial communities in the phyllosphere and endosphere of eight wheat cultivars with differing aphid resistance, grown in the same farmland. Results: The bacterial community in both the phyllosphere and endosphere showed significant differences among most wheat cultivars. The phyllosphere was connected to more complex and stable microbial networks than the endosphere in most wheat cultivars. Moreover, the genera Pantoea, Massilia, and Pseudomonas were found to play a major role in shaping the microbial community in the wheat phyllosphere. Additionally, wheat plants showed phenotype-specific associations with the genera Massilia and Pseudomonas. The abundance of the genus Exiguobacterium in the phyllosphere exhibited a significant negative correlation with the aphid hazard grade in the wheat plants. Conclusion: Communities of leaf-associated microbes in wheat plants were mainly driven by the host genotype. Members of the genus Exiguobacterium may have adverse effects on wheat aphids. Our findings provide new clues supporting the development of aphid control strategies based on phyllosphere microbiome engineering.

Life table and predation data were collected for Coccinella septempunctata (Linnaeus) (Coleoptera: Coccinellidae) feeding on three different host aphid species, Aphis craccivora (Koch) (Hemiptera: Aphididae), Lipaphis erysimi (Kaltenbach) (Hemiptera: Aphididae), and Myzus persicae (Sulzer) (Hemiptera: Aphididae), under laboratory conditions, using age-stage, two-sex life table. The preadult developmental period of C. septempunctata was the shortest on M. persicae (21.12 d) and the longest on A. craccivora (28.81 d). Net reproductive rate (R₀) ranged from 77.31 offspring per individual on A. craccivora to 165.97 offspring per individual on M. persicae. Mean generation time (T) ranged from 39.10 d on M. persicae to 51.96 d on L. erysimi. Values of the intrinsic rate of increase (r) decreased in the order M. persicae, A. craccivora, and L. erysimi (0.1302, 0.0864 and 0.0848 dˉ¹, respectively). The highest finite rate of increase (λ) was observed on M. persicae (1.1391 dˉ¹) and the lowest was observed on A. craccivora and L. erysimi (1.0903 and 1.0885 dˉ¹, respectively). This information will be useful in relation to the mass rearing of C. septempunctata in biological control systems.

Sitobion avenae (Fabricius), Rhopalosiphum padi (Linnaeus), Schizaphis graminum (Rondani), and Metopolophium dirhodum (Walker) (Hemiptera: Aphididae) are important pests of wheat and other cereals worldwide. In this study, the susceptibilities of four wheat aphid species to seven insecticides were assessed. Furthermore, the activities of carboxylesterase (CarE), glutathione S-transferase (GSTs), and cytochrome P450 monooxygenase (P450s) were determined in imidacloprid treated and untreated aphids. The results showed that the susceptibilities of four wheat aphid species to tested insecticides are different and M. dirhodum has shown higher tolerance to most insecticides. Relatively higher CarE and GST activities were observed in M. dirhodum, and P450s activities increased significantly in response to imidacloprid treatment. Moreover, susceptibility to imidacloprid were increased by the oxidase inhibitor piperonyl butoxide in M. dirhodum (20-fold). The results we have obtained imply that P450s may play an important role in imidacloprid metabolic process in M. dirhodum. We suggest that a highly species-specific approach is essential for managing M. dirhodum.

Rhopalosiphum padi (L.) (Hemiptera: Aphididae) is an important cosmopolitan pest in cereal crops. Reference genes can significantly affect qRT-PCR results. Therefore, selecting appropriate reference genes is a key prerequisite for qRT-PCR analyses. This study was conducted to identify suitable qRT-PCR reference genes in R. padi. We systematically analyzed the expression profiles of 11 commonly used reference genes. The ΔCt method, the BestKeeper, NormFinder, geNorm algorithms, and the RefFinder online tool were used to evaluate the suitability of these genes under diverse experimental conditions. The data indicated that the most appropriate sets of reference genes were β-actin and GAPDH (for developmental stages), AK and TATA (for populations), RPS18 and RPL13 (for tissues), TATA and GAPDH (for wing dimorphism), EF-1α and RPS6 (for antibiotic treatments), GAPDH and β-actin (for insecticide treatments), GAPDH, TATA, RPS18 (for starvation-induced stress), TATA, RPS6, and AK (for temperatures), and TATA and GAPDH (for all conditions). Our study findings, which revealed the reference genes suitable for various experimental conditions, will facilitate the standardization of qRT-PCR programs, while also improving the accuracy of qRT-PCR analyses, with implications for future research on R. padi gene functions.