Morph-specific fitness throughout the life cycle of the grain aphid, nonhost-alternating, holocyclic Sitobion avenae (Hemiptera: Aphididae).

Aphids exhibit seasonally alternating asexual and sexual reproductive modes. Different morphs are produced throughout the life cycle. To evaluate morph-specific fitness during reproductive switching, holocyclic Sitobion avenae were induced continuously under short light conditions, and development and reproduction were compared in each morph. Seven morphs, including apterous and alate virginoparae, apterous and alate sexuparae, oviparae, males, and fundatrices, were produced during the life cycle. The greatest proportions of sexuparae, oviparae, males, and virginoparae were in the G1, G2, G3, and G4 generations, respectively. Regardless of asexual or sexual morphs, alate morphs exhibited a marked delay in age at maturity compared with that of apterous morphs. Among the alate morphs, males had the longest age at maturity, followed by sexuparae and virginoparae. Among the apterous morphs, sexuparae were older at maturity than the fundatrices, virginoparae, and oviparae. The nymphs of each morph had equal survival potentials. For the same wing morphs, apterous sexuparae and oviparae exhibited substantial delays in the pre-reproductive period and considerable reductions in fecundity, compared with those of apterous virginoparae and fundatrices, whereas alate sexuparae and alate virginoparae had similar fecundity. The seven morphs exhibited Deevey I survivorship throughout the life cycle. These results suggest that sexual production, particularly in males, has short-term development and reproduction costs. The coexistence of sexual and asexual morphs in sexuparae offspring may be regarded as an adaptive strategy for limiting the risk of low fitness in winter.

Early monitoring of parasitism by Aphidiinae parasitoids on the grain aphid Sitobion miscanthi in wheat fields using DNA barcoding.

BACKGROUND: Sitobion miscanthi is a major wheat pest at the grain-filling stage found in China. Identifying parasitoid species and understanding parasitism rates are keys to controlling the aphids via natural enemies in the wheat field. RESULTS: In the present study, a method based on DNA barcoding for early determination of the community composition of Aphidiinae parasitoids and parasitism on the aphid was developed. The proposed method detected Aphidius gifuensis as the predominant parasite, with parasitism rates of 40.1 ± 2.8% in 2019 and 65.7 ± 3.7% in 2022, and found that the rate varied significantly among different wheat varieties. COI primers efficiently amplified the Aphidiinae parasitoids COI fragments and amplified the aphid COI fragments derived from parasitized (mummified) S. miscanthi. Thus, the COI barcode is not sufficiently specific to unambiguously detect immature parasitoids inside their S. miscanthi hosts. However, it can be used to detect the DNA extracted from mummified aphids. In contrast, the 16S and LWRh primers effectively amplified and identified the parasitoids in parasitized aphids. The 16S primer was reliable even in the early stages of parasitism (24 h) and for DNA samples stored at -20 °C for 5 days. The three barcodes from COI, 16S, and LWRh genes could not clearly distinguish a few certain Aphidiinae species owing to relatively low intraspecific and interspecific diversity. CONCLUSION: The morphological features remain indispensable when identifying Aphidiinae species. Nonetheless, the COI and 16S primers could be used in combination for monitoring the parasitism rates on S. miscanthi in wheat fields. © 2022 Society of Chemical Industry.

Prediction of the Current and Future Distributions of the Hessian Fly, Mayetiola destructor (Say), under Climatic Change in China.

The Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae), is a destructive wheat pest worldwide and an important alien species in China. Based on 258 distribution records and nine environmental factors of the Hessian fly, we predicted the potential distribution area in China under three current and future (2050s and 2070s) climate change scenarios (RCP2.6, RCP4.5, and RCP8.5) via the optimized MaxEnt model. Under the current climate conditions, the suitable distribution areas of the Hessian fly in China were 25-48° N, 81-123° E, and the total highly suitable distribution area is approximately 9.63 × 105 km2, accounting for 9.99% of the total national area. The highly suitable areas are mainly located in northern Xinjiang and central and eastern China. With the rising global temperatures, except for the high-suitable areas under the RCP8.5 scenario, most potential geographic distribution areas would expand in the future. The minimum temperature in February (tmin-2), precipitation in March (prec-3), maximum temperature in November (tmax-11), and precipitation seasonality (bio-15) are important factors that affect the potential geographic distribution of the Hessian fly. This study provides an important reference and empirical basis for management of the Hessian fly in the future.

Effects of Crop Resistance on the Tritrophic Interactions between Wheat Lines, Schizaphis graminum (Hemitera: Aphididae), and Propylaea japonica (Coleoptera: Coccinellidae).

Crop resistance and biological control are both considered efficient and environmentally friendly methods of sustainable pest control. In this study, we aimed at investigating the direct influence of four wheat lines with varying resistance level on the life-history traits of the greenbug, Schizaphis graminum, and the mediational effect on the functional response of a predatory ladybird, Propylaea japonica, under laboratory conditions. Results showed that the aphid fitness was the lowest for aphids that had been feeding on wheat line '98-10-19' for one year. These aphids had the longest development time, and least adult mass, minimal mean relative growth rate, and lowest reproductive fitness. In contrast, the aphids that fed on wheat line '98-10-30' were the fittest, with the shortest development time and highest levels of reproductive fitness. The predatory activities of the ladybeetle, especially the adult male significantly decreased following the consumption of aphids belonging to the '98-10-19'-acclimated population. However, there were no significant differences in predatory efficiency (net attack frequency) among the four aphid acclimated populations. Our results showed that the wheat line '98-10-19' has a relative higher resistance to S. graminum than the other three wheat lines, which could further decrease the amount of prey available for consumption. However, the ecological effect of the resistance of '98-10-19' to S. graminum posed no negative influence on the biocontrol potential of P. japonica to these aphids, as their predatory efficiency increases at the fourth instar larvae phase.

Multi-generational Effects of Different Resistant Wheat Varieties on Fitness of Sitobion avenae (Hemiptera: Aphididae).

Crop resistance plays a role in preventing aphid damage, benefiting food production industries, but its effects are limited due to aphid adaptation and phenotypic plasticity. Therefore, furthering understanding of aphid-crop interactions will improve our ability to protect crops from aphids. To determine how aphids adapt to resistant varieties of wheat, Triticum aestivum L. over time, we performed a laboratory experiment to assess the multi-generational effects of three wheat varieties, Batis, Ww2730, and Xiaoyan22, with different resistance levels on the fitness of Sitobion avenae (Fab.) (Hemiptera: Aphididae). The results showed that Ww2730 and Xiaoyan22 were more resistant than Batis to S. avenae, regardless of whether the aphids were newly introduced or had been acclimated before being introduced to the three wheat varieties. However, the effect of resistance on aphid life-history traits was time dependent. Aphid weigh gain increased and they development faster of the acclimated generation compared to the newly introduced generation on all three varieties. And the fecundity on the three varieties and net reproduction rates on Batis and Xiaoyan22 significantly decreased. Aphid fitness in terms of individual life-history parameters improved, whereas aphid fitness in terms of reproductive decreased, and a convergence effect, the difference gaps and standard errors of all life-history traits among the three acclimated populations had narrowed and were less than those in the three first-generation populations, was observed during the 3-mo experimental period. We suggested that S. avenae could rapidly respond to wheat resistance through life-history plasticity.

Previous Aphid Infestation Induces Different Expression Profiles of Genes Associated with Hormone-Dependent Responses in Near-Isogenic Winter Wheat Lines.

Hormone-dependent responses in host plants induced by herbivore infestation have species-specific effects. This study focused on determining the relative expression profiles of the genes associated with hormone-dependent pathways in two near-isogenic wheat lines when attacked by cereal aphids. Infestation with Rhopalosiphum padi Linnaeus (Hemiptera: Aphididae) and/or Sitobion avenae Fabricius (Hemiptera: Aphididae) significantly upregulated the expression of marker genes related to the salicylic acid (SA)- and jasmonic acid (JA)-dependent pathways in the tested lines. In the resistant line 35-E4, previous infestation with R. padi significantly increased the relative expression of plant pathogenesis-related protein 1 at all sampling times but did not have a significant effect on the expression of the phenylalanine ammonia-lyase (PAL) gene. In addition, the expression levels of the lipoxygenase (LOX) and allene oxide synthase (AOS) genes immediately increased after the aphid attack. In susceptible line 35-A20, infestation with either R. padi or S. avenae led to significantly increased expression levels of the AOS and PAL genes. Moreover, sequential aphid infestation induced higher expression of AOS compared with a single-species aphid infestation, whereas the expression of the PAL gene was antagonistically affected by sequential aphid infestation. Overall, these results showed that aphid infestation induced SA- and JA-dependent responses in host plants. However, the expression profiles of these genes in resistant and susceptible host lines were significantly different.

Maternal effects of the English grain aphids feeding on the wheat varieties with different resistance traits.

The maternal effects of the English grain aphid, Sitobion avenae on offspring phenotypes and performance on wheat varieties with different resistance traits were examined. We found that both conditioning wheat varieties(the host plant for over 3 months) and transition wheat varieties affected the biological parameters of aphid offspring after they were transferred between wheat varieties with different resistance traits. The conditioning varieties affected weight gain, development time (DT), and the intrinsic rate of natural increase (rm), whereas transition varieties affected the fecundity, rm, net reproductive rate, and fitness index. The conditioning and transition wheat varieties had significant interaction effects on the aphid offspring's DT, mean relative growth rate, and fecundity. Our results showed that there was obvious maternal effects on offspring when S. avenae transferred bwteen wheat varieties with different resistance level, and the resistance traits of wheat varieties could induce an interaction between the conditioning and transition wheat varieties to influence the growth, development, reproduction, and even population dynamics of S. avenae. The conditioning varieties affected life-history traits related to individual growth and development to a greater extent, whereas transition varieties affected fecundity and population parameters more.

Resistance of Seven Cabbage Cultivars to Green Peach Aphid (Hemiptera: Aphididae).

The green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), is an important pest of many crops in the world and a vector of more than 100 plant viruses. It is a major pest of Brassica vegetables such as Chinese cabbage in northern China. Chemical control is extensively used to manage this aphid around the world; however, development of insecticide resistance has been a major obstacle facing growers. Host plant resistance in Chinese cabbage against M. persicae has not been reported yet. In this study, we investigated the resistance categories in seven Chinese cabbage cultivars against M. persicae. The resistance categories of these cultivars included antixenosis, antibiosis, and tolerance related to leaf color and wax content. The cultivar 'Yuanbao' had antibiotic and tolerance effects on the aphid. The rate of intrinsic increase (rm) of M. persicae was lower on Yuanbao compared with the other six cultivars. Yuanbao also had the highest antibiosis against the aphid. The aphid preferred 'Qingan 80', which had the highest wavelength (green) in leaf color. The highest wax content was found in Yuanbao, which had a significantly negative correlation with the preference of M. persicae. The cabbage cultivar Yuanbao was resistant to M. persicae and could be used in the development of integrated pest management (IPM) programs against the aphid in the field.

Resistance of Wheat Accessions to the English Grain Aphid Sitobion avenae.

The English grain aphid, Sitobion avenae, is a major pest species of wheat crops; however, certain varieties may have stronger resistance to infestation than others. Here, we investigated 3 classical resistance mechanisms (antixenosis, antibiosis, and tolerance) by 14 wheat varieties/lines to S. avenae under laboratory and field conditions. Under laboratory conditions, alatae given the choice between 2 wheat varieties, strongly discriminated against certain varieties. Specifically, the 'Amigo' variety had the lowest palatability to S. avenae alatae of all varieties. 'Tm' (Triticum monococcum), 'Astron,' 'Xanthus,' 'Ww2730,' and 'Batis' varieties also had lower palatability than other varieties. Thus, these accessions may use antibiosis as the resistant mechanism. In contrast, under field conditions, there were no significant differences in the number of alatae detected on the 14 wheat varieties. One synthetic line (98-10-30, a cross between of Triticum aestivum (var. Chris) and Triticum turgidum (var. durum) hybridization) had low aphid numbers but high yield loss, indicating that it has high antibiosis, but poor tolerance. In comparison, 'Amigo,' 'Xiaoyan22,' and some '186Tm' samples had high aphid numbers but low yield loss rates, indicating they have low antibiosis, but good tolerance. Aphid population size and wheat yield loss rates greatly varied in different fields and years for '98-10-35,' 'Xiaoyan22,' 'Tp,' 'Tam200,' 'PI high,' and other '186Tm' samples, which were hybrid offspring of T. aestivum and wheat related species. Thus, these germplasm should be considered for use in future studies. Overall, S. avenae is best adapted to 'Xinong1376,' because it was the most palatable variety, with the greatest yield loss rates of all 14 wheat varieties. However, individual varieties/lines influenced aphid populations differently in different years. Therefore, we strongly recommend a combination of laboratory and long-term field experiments in targeted planting regions to identify varieties/lines that consistently show high resistance to S. avenae infestation.

Testing the fecundity advantage hypothesis with Sitobion avenae, Rhopalosiphum padi, and Schizaphis graminum (Hemiptera: Aphididae) feeding on ten wheat accessions.

The fecundity advantage hypothesis suggests that females with a large body size produce more offspring than smaller females. We tested this hypothesis by exploring the correlations between life-history traits of three aphid species feeding on ten wheat accessions at three levels of analysis with respect to the host plant: overall, inter-accession, and intra-accession. We found that fecundity was significantly correlated with mean relative growth rate (MRGR), weight gain, and development time, and that the faster aphid develops the greater body and fecundity, depending on aphid species, wheat accession, and analyses level. Larger aphids of all three species produced more offspring overall; this held true for Sitobion avenae and Schizaphis graminum at the inter-accession level, and for S. avenae, Rhopalosiphum padi, and S. graminum for three, five, and eight accessions respectively at the intra-accession level. Only one correlation, between intrinsic rates of natural increase (rm) and MRGR, was significant for all aphid species at all three analysis levels. A more accurate statement of the fecundity advantage hypothesis is that cereal aphids with greater MRGR generally maintain higher rm on wheat. Our results also provide a method for exploring relationships between individual life-history traits and population dynamics for insects on host plants.

Effects of zinc on CarE activities and its gene transcript level in the English grain aphid, Sitobion avenae.

As a selective stress, heavy metals play an important role in inducing the adaptive adjustments of insects to changing environments. Carboxylesterase (CarE) is one kind of biomarker that could help us to explore the adaptation mechanism of aphids to heavy metal stress. In this study, CarE activity and gene expression level were investigated in English grain aphids, Sitobion avenae (F.) (Hemiptera: Aphididae), exposed to Zn2+ at concentrations of 0, 400, and 1600 mg/kg for 5, 15, 25, and 30 generations. The results showed that the CarE activity was significantly different between different Zn2+ concentrations and different generations. The CarE activity significantly decreased with increasing generations. In the higher generations, the CarE activity was strongly inhibited by the 1600 mg/kg of Zn2+. Realtime quantitative PCR revealed that the CarE gene expression pattern in S. avenae was up-regulated under the condition of 400 mg/kg and 1600 mg/kg of Zn2+, but a significant difference was not found after long-term exposure to high concentrations of Zn2+. It was concluded that CarE could be the sensitive biomarker for S. avenae response to the presence of Zn2+. In order to adapt to heavy metal Zn2+ stress, S. avenae had particular patterns of gene expression under long-term stress.

Tripartite interactions of Barley yellow dwarf virus, Sitobion avenae and wheat varieties.

The tripartite interactions in a pathosystem involving wheat (Triticum aestivum L.), the Barley yellow dwarf virus (BYDV), and the BYDV vector aphid Sitobion avenae were studied under field conditions to determine the impact of these interactions on aphid populations, virus pathology and grain yield. Wheat varietal resistance to BYDV and aphids varied among the three wheat varieties studied over two consecutive years. The results demonstrated that (1) aphid peak number (APN) in the aphid + BYDV (viruliferous aphid) treatment was greater and occurred earlier than that in the non-viruliferous aphid treatment. The APN and the area under the curve of population dynamics (AUC) on a S. avenae-resistant variety 98-10-30 was significantly lower than on two aphid-susceptible varieties Tam200(13)G and Xiaoyan6. (2) The production of alatae (PA) was greater on the variety 98-10-30 than on the other varieties, and PA was greater in the aphid + BYDV treatment on 98-10-30 than in the non-viruliferous aphid treatment, but this trend was reversed on Tam200(13)G and Xiaoyan6. (3) The BYDV disease incidence (DIC) on the variety 98-10-30 was greater than that on the other two varieties in 2012, and the disease index (DID) on Tam200(13)G was lower than on the other varieties in the aphid + BYDV and BYDV treatments in 2012, but not in 2011 when aphid vector numbers were generally lower. (4) Yield loss in the aphid + BYDV treatment tended to be greater than that in the aphid or BYDV alone treatments across varieties and years. We suggested that aphid population development and BYDV transmission tend to promote each other under field conditions. The aphids + BYDV treatment caused greater yield reductions than non-viruliferous aphids or virus treatment. Wheat varietal resistance in 98-10-30 affects the aphid dispersal, virus transmission and wheat yield loss though inhibits aphid populations from increasing.

The resistance and correlation analysis to three species of cereal aphids (Hemiptera: Aphididae) on 10 wheat varieties or lines.

Winter wheat resistance is an efficient and environmentally friendly means to controlling aphids. By using principal component analysis and correlation analysis, we evaluated the resistance of 10 winter wheat varieties or lines from three countries to the following three aphid species: Sitobion avenae, Rhopalosiphum padi, and Schizaphis graminum. The data show that Batis was susceptible to Si. avenae and R. padi, but had adverse effect on the development of Sc. graminum; Astron was advantageous to WG and r(m) of Si. avenae and R. padi, but not to Sc. graminum; Amigo was resistant to Sc. graminum and R. padi, but susceptible to Si. avenae; 98-10-35 was resistant to Si. avenae and R. padi, but not to Sc. graminum; 98-10-30 was adverse to growth and fecundity of Si. avenae, but better for Sc. graminum and R. padi; Xiaoyan22 was susceptible to Sc. graminum, but not to R. padi; Ww2730 were resistant to Si. avenae, but susceptible to Sc. graminum; 186tm was susceptible to R. padi, but caused high mortality for Si. avenae and Sc. graminum. Correlation analysis suggests the wheat varieties or lines that were resistant to Si. avenae were always resistant to R. padi, but susceptible to Sc. graminum. However, the overall similarities in resistance classifications were not because of the same phenotypic characters of the wheat varieties or lines. We conclude that the wheat varieties or lines had specific different resistances to the three aphid species, and the resistant traits (antibiosis) can be defined at two or more hierarchical levels. There was even a stronger "trade-off" for the comparison of Si. avenae versus Sc. graminum and R. padi versus Sc. graminum.

Life table evaluation of survival and reproduction of the aphid, Sitobion avenae, exposed to cadmium.

The effects of cadmium (Cd) on the development, fecundity, and reproduction of the grain aphid, Sitobion avenae Fabricius (Hemiptera: Aphididae) were estimated by constructing a life table of S. avenae exposed to Cd. The concentrations of Cd in the soil were as follows: 0, 10, 20, 40, 80, and 160 mg/kg. The correlation analysis of the Cd concentration in soil and wheat revealed that the amount in the wheat increased with the increase of Cd concentrations in soil. The results indicated that, the latter part of the reproduction period was significantly affected by Cd, according to the curve of the total survival rate (l(x)). The net reproductive rate (R(0)), innate capacity of increase (r), and finite rate of increase (λ) of S. avenae all decreased under the stress of Cd, and were lowest at a Cd concentration of 20 mg/kg. Cd also negatively affected fecundity and m(x) (the number of offspring produced by an individual female). At 20 mg/kg, the decline of them was most obvious. In conclusion, survival and reproduction of S. avenae were inhibited under the treatment of the heavy metal Cd. Sitobion avenae was more sensitive to Cd at concentration of 20 mg/kg compared to the other concentrations. This concentration can be used to examine the mechanisms behind population genetics and biological mutation of S. avenae when exposed to heavy metal.

[Effects of UV-radiation on biological characteristics of different body-color biotypes of Sitobion avenae (Fab.)].

UV-radiation exerts strong selection stress on the evolution of aphid populations, and thus, leads to their genetic differentiation. However, the effects of UV-radiation on different body-color biotypes of aphids are still ambiguous. In this study, new-born nymphae of red and green biotypes of Sitobion avenae were placed on two wheat varieties (Xiaoyan-22 and Astron), bred in an artificial bioclimatic chamber under strict controlled conditions (at 15 degrees C, 20 degrees C, and 25 degrees C, and treated with 30 W lamp of UV-B for 30 min per day for 5 days), and their development duration, mass, and mean relative growth rate were measured. The results showed that at lower temperature, UV-radiation delayed the growth of green biotype aphid on Xiaoyan-22 and Astron significantly; while at higher temperature, UV-radiation significantly delayed the growth of red biotype aphid on Xiaoyan-22, but had lesser effects on the growth of the two biotypes on Astron, illustrating that different biotypes of aphids had different responses to UV-radiation, and the responses were correlated to temperature and wheat varieties.