Flupyradifurone is a promising new insecticide used for controlling Bemisia tabaci during vegetable production.  In this study, we assessed the fitness costs and mode of inheritance associated with resistance to flupyradifurone in B. tabaci by comparing the susceptible strain (MED-S) to one field-evolved flupyradifurone-resistant strain (WH-R, with 199-fold resistance) and one laboratory-selected flupyradifurone-resistant strain (FLU-SEL, with 124-fold resistance).  Progenies of reciprocal crosses between WH-R and MED-S (F_1A, F_1B, and pooled F₁), and between FLU-SEL and MED-S (F_1C, F_1D, and pooled F₁’), showed varying degrees of dominance, indicating that resistance to flupyradifurone in WH-R was autosomal and incompletely dominant, yet in FLU-SEL it was autosomal and incompletely recessive.  Furthermore, the development of resistance to flupyradifurone occurred at the expense of fitness costs for the resistant populations.  Compared to the MED-S strain, WH-R showed a relative fitness of 0.50 with significantly prolonged developmental durations and reduced survival rates of the nymphal and pseudopupal stages, as well as decreased fecundity and hatchability.  Similarly, FLU-SEL showed a relative fitness of 0.65 and also demonstrated prolonged developmental durations and reduced survival rates of nymphs and pseudopupae, as well as decreased hatchability in comparison with the MED-S strain.  However, no significant differences in fecundity were observed between MED-S and FLU-SEL.  The present study provides useful knowledge for formulating pest management strategies in the field, which will allow growers to slow the development of resistance to flupyradifurone and to sustainably control B. tabaci.

The Bemisia tabaci (Gennadius) cryptic species complex comprises important insect pests that cause devastating damage to agricultural crops worldwide.  In China, the B. tabaci Mediterranean (MED) (or biotype Q) species is threatening agricultural production all over the country as resistance to commonly used insecticides has increased.  This situation highlights the need for alternative pest control measures.  Cyantraniliprole, a novel anthranilic diamide insecticide, has been widely employed to control Hemipteran pests.  To monitor the levels of resistance to cyantraniliprole in B. tabaci field populations in China, bioassays were conducted for 18 field samples from nine provinces over two years.  Compared with median lethal concentration (LC₅₀) for the MED susceptible strain, all field samples had significantly higher resistance to cyantraniliprole.  Furthermore, resistance factors (RFs) increased significantly in samples from Shanxi (from 5.62 in 2015 to 25.81 in 2016), Hunan (3.30 in 2015 to 20.97 in 2016) and Hubei (from 9.81 in 2015 to 23.91 in 2016) provinces.  This study indicates a considerable decrease in the efficacy of cyantraniliprole against B. tabaci and establishes a baseline of susceptibility that could serve as a reference for future monitoring and management of B. tabaci resistance to cyantraniliprole.

Four strains of the Q biotype and one of the B biotype of the whitefly Bemisia tabaci collected from China were characterised for resistance to four neonicotinoid insecticides and pymetrozine. Q biotype strains showed moderate to strong resistance to imidacloprid, thiamethoxam and acetamiprid, but little or no cross-resistance to dinotefuron. Resistance to neonicotinoids was consistently associated with resistance to pymetrozine, despite the latter having a distinct (though unresolved) mode of action. The single B biotype strain proved largely susceptible to all the insecticides investigated. Resistance in the Q biotype strains was associated with over-expression of a cytochrome P450 monooxygenase gene, CYP6CM1, whose substrate specificity presumably accounts for the observed cross-resistance profiles.

The whitefly Bemisia tabaci are considered as a taxonomically complex that contained some destructive pests. Two of the most prevalent cryptic species are B. tabaci Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED). In an extensive field survey of the B. tabaci complex present throughout part of China from 2004 to 2007, we obtained 93 samples of B. tabaci from 22 provinces. We determined that these Chinese haplotypes included 2 invasive species (MEAM1 and MED), and 4 indigenous cryptic species (Asia II 1, Asia II 3, China 3 and Asia II 7) by sequencing mitochondrial cytochrome oxidose one gene (mtCOI). The diversity and genetic differentiation of a subset of 19 populations of B. tabaci were studied using cDNA amplified fragment length polymorphism (AFLP). Prior to 2007, MEAM1 was a dominant species in many provinces in China. By 2007, MED was dominant in 11 provinces. Both invasive and indigenous species were simultaneously found in some regions. Indigenous species of B. tabaci were found in six provinces in southern China. MED and MEAM1 have broad ranges of host plants, and indigenous species appeared to have much narrower host ranges. All Asia II 3 samples were found on cotton except one on aubergine. China 3 has more host plants than Asia II 3. Twelve samples of China 3 were collected from sweet potato, Japanese hop, squash and cotton. A total of 677 reproducible bands amplified with 5 AFLP primer combinations were obtained. The highest proportion of polymorphic bands was 98.7% and the lowest was 91.9%. Unweighted pair-group method analysis indicated that the clustering was independent of the different species. MED showed the lowest degree of similarity than the other species. The data indicate that both MEAM1and MED were rapidly established in China.

Roots are vital for crop growth, development, yield and tolerance to various types of environmental stress.  Numerous genetic loci associated with soybean root morphological traits have been identified, but few genes associated with these traits have been identified.  In this study, seven quantitative trait loci (QTLs) containing stable SNPs significantly associated with the root dry weight in soybeans were identified through a genome-wide association study.  Among these QTLs, qRDW14-2 presented the greatest significance.  In qRDW14-2, the gene GmRGD14, encoding the lysophosphatidic acid acyltransferase LPAT4, was identified as a candidate.  GmRGD14, in block63, which contained the significant SNP S14_6521715, had the highest expression level in soybean roots, and its Arabidopsis homologous mutant lpat4 presented more lateral roots than did the control Col-0.  GmRGD14 was localized primarily to the cell membrane and endoplasmic reticulum.  The heterologous overexpression of GmRGD14 in Arabidopsis significantly increased the lateral root number, which was similar to the phenotype of atlpat4.  Furthermore, overexpression of GmRGD14 resulted in a greater total root length, root tip number, root surface area and root volume in the hairy roots of transgenic soybean plants than in those of WT soybean plants, whereas knockdown of the gene via RNA interference in soybean hairy roots resulted in the opposite phenotype.  GmRGD14, which is highly genetically variable in wild soybean, has been gradually utilized during soybean domestication.  Overall, this study revealed that GmRGD14 is a new key gene that plays a role in root growth, providing a new genetic target for breeding elite soybean varieties with strong root systems.