Succinate dehydrogenase (SDH) is an important respiratory enzyme which participates in the tricarboxylic acid cycle and oxidative phosphorylation. A previous study of the baseline sensitivity of Botrytis cinerea against SDH inhibitors (SDHIs) showed that intrinsic sensitivity of the small population against the SDHIs exhibited significant differences. In the sequencing assay, we found five kinds of amino acid polymorphism in SDH subunit C (SdhC) of B. cinerea isolates which were never exposed to the SDHIs. To validate that amino acid polymorphism in the SdhC of B. cinerea confers intrinsic sensitivity against the SDHIs, the replacement mutants containing each kind of amino acid polymorphism of SdhC exhibited phenotype differences in intrinsic sensitivity to SDHIs, mycelial growth, sporulation, virulence, oxidative stress response, and carbon source utilization. These results indicated that SdhC of B. cinerea experienced positive selection during evolution and resulted in amino acid polymorphism which is involved in intrinsic sensitivity to SDHIs and biological fitness.

The phytophagous mite Tetranychus truncatus is a serious pest in East Asia but has a relatively narrower host range than the pest mite Tetranychus urticae, which can feed on over 1200 plant species. Here, we generated a high‐quality chromosomal level genome of T. truncatus and compared it with that of T. urticae, with an emphasis on the genes related to detoxification and chemoreception, to explore the genomic basis underlying the evolution of host range. We also conducted population genetics analyses (in 86 females from 10 populations) and host transfer experiments (in 4 populations) to investigate transcription changes following transfer to a low‐quality host (Solanum melongena, eggplant), and we established possible connections between fitness on eggplant and genes related to detoxification and chemoreception. We found that T. truncatus has fewer genes related to detoxification, transport, and chemoreception than T. urticae, with a particularly strong reduction in gustatory receptor (GR) genes. We also found widespread transcriptional variation among T. truncatus populations, which varied in fitness on eggplant. We characterized selection on detoxification‐related genes through ω values and found a negative correlation between expression levels and ω values. Based on the transcription results, as well as the fitness and genetic differences among populations, we identified genes potentially involved in adaptation to eggplant in T. truncatus. Our work provides a genomic resource for this pest mite and new insights into mechanisms underlying the adaptation of herbivorous mites to host plants.

The rapid evolution of pesticide resistance imposes great pressure on food production. However, how resistance alleles arise and spread across field populations remains largely understood. Here, we study the evolutionary trajectories of resistance alleles in Tetranychus urticae, a rapidly evolving pest. We sequence the genomes of 258 T. urticae females collected from China. Combined with global reference genomic data, we examine the evolutionary origin(s) of 18 mutations across 10 target-site genes and analyze the global population genetic structure using genome-wide SNPs. Our findings reveal a striking prevalence of multiple independent origins of resistance mutations, with only two of 18 mutations showing an apparent single origin. Population structure and haplotype analyses point to an important role of gene flow in the spread of resistance alleles. Selection analyses reveal pesticide-driven sweeps affecting genetic diversity. These findings advance our understanding of the rapid adaptation of arthropod herbivores to extreme selective pressure.

Nine microsatellite loci were isolated from the genome of Laodelphax striatellus (Homoptera: Delphacidae) by constructing (TC)(6)(AC)(5) and (AG)(6)(AC)(5) compound SSR-enriched libraries using suppression-PCR procedures. These loci were found to be highly polymorphic, with 13 to 30 alleles per locus in the three populations that we investigated (Jiangsu, Shandong and Zhejiang). The observed and expected heterozygosities ranged from 0.255 to 0.833 and 0.392 to 0.929, respectively. These microsatellite markers can be used for the study of population genetic structure and genetic diversity of L. striatellus.