Dynamic changes of root proteome reveal diverse responsive proteins in maize subjected to cadmium stress

Toxic symptoms and tolerance mechanisms of heavy metal in maize are well documented. However, limited information is available regarding the changes in the proteome of maize seedling roots in response to cadmium(Cd) stress. Here, we employed an i TRAQ-based quantitative proteomic approach to characterize the dynamic alterations in the root proteome during early developmental in maize seedling. We conducted our proteomic experiments in three-day seedling subjected to Cd stress, using roots in four time points. We identified a total of 733, 307, 499, and 576 differentially abundant proteins after 12, 24, 48, or 72 h of treatment, respectively. These proteins displayed different functions, such as ribosomal synthesis, reactive oxygen species homeostasis, cell wall organization, cellular metabolism, and carbohydrate and energy metabolism. Of the 166 and 177 proteins with higher and lower abundance identified in at least two time points, 14 were common for three time points. We selected nine proteins to verify their expression using quantitative real-time PCR. Proteins involved in the ribosome pathway were especially responsive to Cd stress. Functional characterization of the proteins and the pathways identified in this study could help our understanding of the complicated molecular mechanism involved in Cd stress responses and create a list of candidate gene responsible for Cd tolerance in maize seeding roots.     

Sublethal effects of sulfoxaflor on the fitness of two species of wheat aphids,Sitobion avenae(F.) and Rhopalosiphum padi(L.)

Sitobion avenae(F.) and Rhopalosiphum padi(L.) are two important pests of wheat in China. They typically coexist in fields during the late period of wheat growth. Sulfoxaflor is a novel sulfoximine insecticide that demonstrates broad-spectrum efficacy, especially in targeting sap-feeding insects. This study was carried out to investigate the sublethal effects of sulfoxaflor on the development, longevity, and reproduction of two species of wheat aphids. Our results showed that sublethal concentrations of sulfoxaflor did not cause significant effects on the fecundity or the longevity of the parent generation(F_0 generation) of either S. avenae or R. padi. However, it caused transgenerational sublethal effects. For S. avenae, adult longevity of F_1 generation was significantly decreased. No significant differences were observed on the population parameters of S. avenae in the F_1 generation. For R. padi, the adult preoviposition period(APOP) and the total preoviposition period(TPOP) of F_1 generation were significantly reduced. The mean generation time(T) was significantly reduced in the R. padi F_1 generation. What's more, the intrinsic rate of increase(r_m) and the finite rate of increase(λ) were significantly increased in the R. padi F_1 generation. Taken together, these results suggest that exposure to the LC_(25) of sulfoxafl had no effects on the parent generation of S. avenae or R. padi, but it reduced adult longevity of S. avenae as a negative effect and increased the r_m and λ of R. padi in the first progeny generation, which may have an impact on the population dynamics of R. padi.     

GsMAPK4, a positive regulator of soybean tolerance to salinity stress

Salt stress is one of the major factors affecting plant growth and yield in soybean under saline soil condition. Despite many studies on salinity tolerance of soybean during the past few decades, the detailed signaling pathways and the signaling molecules for salinity tolerance regulation have not been clarified. In this study, a proteomic technology based on two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS) were used to identify proteins responsible for salinity tolerance in soybean plant. Real-time quantitative PCR (qRT-PCR) and Western blotting (WB) were used to verify the results of 2-DE/MS. Based on the results of 2-DE and MS, we selected glucosyltransferase (GsGT4), 4-coumarate, coenzyme A ligase (Gs4CL1), mitogen-activated protein kinase 4 (GsMAPK4), dehydration responsive element binding protein (GsDREB1), and soybean cold-regulated gene (GsSRC1) in the salinity tolerant soybean variety, and GsMAPK4 for subsequent research. We transformed soybean plants with mitogen-activated-protein kinase 4 (GsMAPK4) and screened the resulting transgenics soybean plants using PCR and WB, which confirmed the expression of GsMAPK4 in transgenic soybean. GsMAPK4-overexpressed transgenic plants showed significantly increased tolerance to salt stress, suggesting that GsMAPK4 played a pivotal role in salinity tolerance. Our research will provide new insights for better understanding the salinity tolerance regulation at molecular level.     

Phenotypic characterization and genetic mapping of the dwarf mutant m34 in maize

Plant height is one of the most important agronomic traits associated with yield in maize.In this study,a gibberellins(GA)-insensitive dwarf mutant,m34,was screened from inbred line Ye478 by treatment with the chemical mutagen ethylmethanesulfonate(EMS).Compared to Ye478,m34 showed a dwarf phenotype with shorter internodes,and smaller leaf length and width,but with similar leaf number.Furthermore,m34 exhibited smaller guard cells in internodes than Ye478,suggesting that smaller cells might contribute to its dwarf phenotype.Genetic analysis indicated that the m34 dwarf phenotype was controlled by a recessive nuclear gene.An F2 population derived from a cross between m34 and B73 was used for mutational gene cloning and this gene was mapped to a chromosome region between umc2189 and umc1553 in chromosome 1 bin1.10,which harbored a previously identified dwarf gene Zm VP8.Sequencing analysis showed a nucleotide substitution(G1606 to A1606)in the sixth exon of ZmVP8,which resulted in an amino acid change(E531 to K531)from Ye478 to m34.This amino acid change resulted in anα-helix changing to aβ-sheet in the secondary protein structure and the‘SPEC’domain changed to a‘BOT1NT’domain in the tertiary protein structure.Taken together,these results suggested that m34 is a novel allelic mutant originally derived from Ye478 that is useful for further ZmVP8 functional analysis in maize.     

The synergistic advantage of combining chloropicrin or dazomet with fosthiazate nematicide to control root-knot nematode in cucumber production

The highly-damaging root-knot nematode(Meloidogyne spp., RKN) cannot be reliably controlled using only a nematicide such as fosthiazate because of increasing pest resistance. In laboratory and greenhouse trials, we showed that chloropicrin(CP) or dazomet(DZ) synergized the efficacy of fosthiazate against RKN. The combination significantly extended the degradation half-life of fosthiazate by an average of about 1.25 times. CP or DZ with fosthiazate reduced the time for fosthiazate to penetrate the RKN cuticle compared to fosthiazate alone. CP or DZ combined with low or medium rate of fosthiazate increased the total cucumber yield, compared to the use of each product alone. A low-dose fosthiazate with DZ improved total yield more than a low dose fosthiazate with CP. Extending the half-life of fosthiazate and reducing the time for fosthiazate or fumigant to penetrate the RKN cuticle were the two features that gave the fumigant-fosthiazate combination its synergistic advantage over these products used singularly. This synergy provides the opportunity for farmers to use a low dose of fosthiazate which lowers the risk of RKN resistance. Farmers could combine DZ at 30 g m~(-2) with fosthiazate at a low rate of 0.375 g m~(-2) to control RKN and adequately control two major soil-borne diseases in cucumber greenhouses.     

Population genetic structure of Chinese Puccinia triticina races based on multi-locus sequences

Puccinia triticina, the causal agent of wheat leaf rust, is one of the most devastating rust fungi attacking wheat worldwide. Seventy-six isolates of the wheat leaf rust pathogen from Yunnan, Sichuan, Gansu and Henan provinces, China, were tested on wheat leaf rust differentials and the population structure was analyzed using four presumably neutral partial sequence markers such as elongation factor-1α(EF-1α), glyceraldehyde-3-phosphate dehydrogenase(GAPDH), β-tubulin(TUB) and the second largest RNA polymerase subunit(RPB2). The phenotypic diversity of Yunnan and Sichuan populations was higher than that of Gansu and Henan populations. The four populations were separated into two clusters based on the pathogenic data. A total of 12 single nucleotide polymorphisms(SNPs) and 32 haplotypes were identified among the four sequences. The 32 haplotypes were divided into two clusters in a neighbor-joining tree. Bayesian analyses also identified two clusters. Pairwise FST between populations in different regions were significantly different(P0.05). Analysis of molecular variance(AMOVA) indicated that 68% of the total genetic variation was within populations.     

Species-specific COI primers for rapid identification of a globally significant invasive pest,the cassava mealybug Phenacoccus manihoti Matile-Ferrero

The globally invasive cassava mealybug Phenacoccus manihoti Matile-Ferrero is a pernicious pest of cassava,and its recent introduction into Asia has raised considerable alarm.To slow or prevent further invasion,an accurate,simple,and developmental-stage-independent detection method for P.manihoti is required.In the present study,a PCR method based on a species-specific mitochondrial DNA cytochrome oxidase I(SS-COI)marker was developed for rapid identification of P.manihoti.One pair of SS-COI primers(PMSSZW-1F and PMSSZW-1R)was designed based on sequence variations in the COI gene among P.manihoti and related mealybug species.Specificity of the primer pair was validated on 21 closely related species.Sensitivity tests were performed on four immature developmental stages and female adults.Efficacy tests demonstrated that at the relatively low concentration of(135.2±14.7)pgresuspended DNA,the specific fragment was detected in all replicates.Furthermore,the SS-COI primer pair was assayed on three populations of P.manihoti from major exporting countries of cassava.The PCR assay was proved to be a rapid,simple,and reliable molecular measure for the identification of P.manihoti.This tool will be useful for quarantine,monitoring,and management of this invasive pest.     

Characterization of field-evolved resistance to cyantraniliprole in Bemisia tabaci MED from China

Cyantraniliprole is a novel anthranilic diamide insecticide with significant efficacy against Bemisia tabaci, an important pest insect worldwide. In this study, we conducted reversion and selection work and genetic analysis, and determined cross-resistance spectrum and synergism of cyantraniliprole resistance based on the reported population, SX population, of B. tabaci collected from Shanxi Province, China. Compared with a susceptible strain (MED-S), SX population, the field-evolved cyantraniliprole-resistant population exhibited 26.4-fold higher resistance to cyantraniliprole. In SX, a sharp decline of cyantraniliprole resistance was shown in the absence of selection. Another tested strain, SX-R, was established from SX population after successive selection with cyantraniliprole and recently developed 138.4-fold high resistance to cyantraniliprole. SX-R had no cross-resistance to abamectin, imidacloprid, thiamethoxam, sulfoxaflor, or bifenthrin. Genetic analysis illustrated that cyantraniliprole resistance in SX-R was autosomally inherited and incompletely dominant. Additionally, piperonyl butoxide (PBO) significantly inhibited cyantraniliprole resistance in the SX-R strain. In conclusion, the selection of SX with cyantraniliprole led to high resistance to cyantraniliprole which is incompletely dominant and no cross-resistance to several common types of insecticides. Enhanced oxidative metabolism is possibly involved in the resistance of SX-R, yet target-site resistance could not be excluded.     

Global sensitivity analysis of wheat grain yield and quality and the related process variables from the DSSAT-CERES model based on the extended Fourier Amplitude Sensitivity Test method

A crop growth model, integrating genotype, environment, and management factor, was developed to serve as an analytical tool to study the influence of these factors on crop growth, production, and agricultural planning. A major challenge of model application is the optimization and calibration of a considerable number of parameters. Sensitivity analysis(SA) has become an effective method to identify the importance of various parameters. In this study, the extended Fourier Amplitude Sensitivity Test(EFAST) approach was used to evaluate the sensitivity of the DSSAT-CERES model output responses of interest to 39 crop genotype parameters and six soil parameters. The outputs for the SA included grain yield and quality(take grain protein content(GPC) as an indicator) at maturity stage, as well as leaf area index, aboveground biomass, and aboveground nitrogen accumulation at the critical process variables. The key results showed that:(1) the influence of parameter bounds on the sensitivity results was slight and less than the impacts from the significance of the parameters themselves;(2) the sensitivity parameters of grain yield and GPC were different, and the sensitivity of the interactions between parameters to GPC was greater than those between the parameters to grain yield; and(3) the sensitivity analyses of some process variables, including leaf area index, aboveground biomass, and aboveground nitrogen accumulation, should be performed differently. Finally, some parameters, which improve the model's structure and the accuracy of the process simulation, should not be ignored when maturity output as an objective variable is studied.     

First report of cereal cyst nematode (Heterodera filipjevi) on winter wheat in Shandong Province,China

正The cereal cyst nematodes(Heterodera avenae,Heterodera filipjevi,Heterodera latipons)are considered to be one of the most important plant parasitic nematodes attacking most cereals and can cause significant crop losses(Sikora 1988).In China,H.filipjevi(Madzhidov 1981)Stelter,1984,was first reported from Henan province(peng et al.2010)and a few years later in Anhui province and Xinjiang Uygur Autonomous Region(peng et al.2016,2018).In December 2017,a survey for cereal     

The effects of Trichoderma on preventing cucumber fusarium wilt and regulating cucumber physiology

In our previous studies, we identified 3 Trichoderma strains with anti-Fusarium oxysporum activity, including T. asperellum 525, T. harzianum 610, and T. pseudokoningii 886. Here, we evaluated the effects of these 3 Trichoderma strains on preventing cucumber fusarium wilt through pot culture and greenhouse culture experiments. All 3 Trichoderma strains demonstrated higher control effects toward cucumber fusarium wilt than previous studies, with efficacies over 78%. Additionally, inoculation with the 3 Trichoderma strains significantly promoted the quality and yield of cucumbers. Among the 3 strains, Trichoderma 866 was the most effective, with disease control efficacy of 78.64% and a cucumber yield increase of 33%. Furthermore, seedlings inoculated with Trichoderma exhibited significantly increased measures of plant height, stem diameter, leaf area, aboveground fresh weight, underground fresh weight, chlorophyll content, and nitric nitrogen content, as well as the activities of several stress-resistance enzymes, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), polyphenol oxidase (PPO), and ascorbate oxidase (AAO). In addition, the plants inoculated with Trichoderma showed decreased cell membrane permeability and malondialdehyde (MDA) content in the leaves. Together, our results suggest that T. asperellum 525, T. harzianum 610, and T. pseudokoningii 886 inoculations inhibit F. oxysporum infection, stimulate the metabolism in cucumbers, and enhance the activities of stress-resistance enzymes, which consequently promote the growth of cucumber plants, prevent cucumber fusarium wilt, and improve the yield and quality of cucumbers. T. harzianum is a commonly used biocontrol fungus, while few studies have focused on T. asperellum or T. koningense. In this study, strains of T. asperellum and T. pseudokoningii showed excellent plant disease prevention and growth promoting effects on cucumber, indicating that they also have great potential as biocontrol fungi.     

Seedling and adult plant resistance to leaf rust in 46 Chinese bread wheat landraces and 39 wheat lines with known Lr genes

Wheat leaf rust,caused by Puccinia triticina(Pt),is an important foliar disease that has an important influence on wheat yield.The most economic,safe and effective way to control the disease is growing resistant cultivars.In the present study,a total of 46 wheat landraces and 34 wheat lines with known Lr(leaf rust resistance)genes were inoculated with 16Pt pathotypes for postulating seedling resistance gene(s)in the greenhouse.These cultivars and five wheat differential lines with adult plant resistance(APR)genes(Lr12,Lr22b,Lr34,Lr35 and Lr37)were also evaluated for identification of slow rusting resistance in the field trials in Baoding,Hebei Province of China in the 2014–2015 and 2015–2016 cropping seasons.Furthermore,10 functional molecular markers closely linked to 10 known Lr genes were used to detect all the wheat genotypes.Results showed that most of the landraces were susceptible to most of the Pt pathotypes at seedling stage.Nonetheless,Lr1 was detected only in Hongtangliangmai.The field experimental test of the two environments showed that 38 landraces showed slow rusting resistance.Seven cultivars possessed Lr34 but none of the landraces contained Lr37 and Lr46.Lr genes namely,Lr9,Lr19,Lr24,Lr28,Lr29,Lr47,Lr51 and Lr53 were effective at the whole plant stage.Lr18,Lr36 and Lr45 had lost resistance to part of pathotypes at the seedling stage but showed high resistance at the adult plant stage.Lr34 as a slowing rusting gene showed good resistance in the field.Four race-specific APR genes Lr12,Lr13,Lr35 and Lr37 conferred good resistance in the field experiments.Seven race-specific genes,Lr2b,Lr2c,Lr11,Lr16,Lr26,Lr33 and LrB had lost resistance.The 38 landraces showed slow rusting resistance to wheat leaf rust can be used as resistance resources for wheat resistance breeding in China.     

Distribution pattern and titer of Candidatus Liberibacter asiaticus in periwinkle (Catharanthus roseus)

Candidatus Liberibacter asiaticus (CaLas), an uncultured Gram-negative alphaproteobacterium, is the causal agent of Huanglongbing (HLB) in citrus. CaLas resides in phloem sieve tubes and has been shown to be unequally distributed in different tissues. Although HLB is a disease of citrus plants, it has been demonstrated that periwinkle can serve as an experimental host of CaLas, which can be transmitted from citrus to periwinkle via the parasitic plant dodder (Cuscuta spp.). To investigate the distribution of CaLas in various periwinkle tissues, the bacteria were transmitted from an infected periwinkle plant to healthy periwinkles by top-grafting. The movement of the inoculum and associated titer changes were observed over time in various tissues. CaLas could be detected in the leaves, main stems, and roots of infected periwinkle by conventional PCR, and in all three tissues a clear time-dependent change in CaLas titer was observed, with titer increasing soon after inoculation and then decreasing as disease symptoms became severe. The highest titer was found at 25, 35 and 35 days after inoculation in leaves, main stems and roots, respectively. The titer in leaves was much higher than in the main stems and roots at the same time point, and the spatial distribution of CaLas in the leaves, main stems and roots of infected periwinkle was uneven, similar to what has been shown in citrus. The results provide guidance for selecting the proper periwinkle tissues and sampling times for early detection of CaLas.     

Estimates on nitrogen uptake in the subsequent wheat by above-ground and root residue and rhizodeposition of using peanut labeled with 15N isotope on the North China Plain

Leguminous crops play a vital role in enhancing crop yield and improving soil fertility. Therefore, it can be used as an organic N source for improving soil fertility. The purpose of this study was to (i) quantify the amounts of N derived from rhizodeposition, root and above-ground biomass of peanut residue in comparison with wheat and (ii) estimate the effect of the residual N on the wheat-growing season in the subsequent year. The plants of peanut and wheat were stem fed with ¹⁵N urea using the cotton-wick method at the Wuqiao Station of China Agricultural University in 2014. The experiment consisted of four residue-returning strategies in a randomized complete-block design: (i) no return of crop residue (CR0); (ii) return of above-ground biomass of peanut crop (CR1); (iii) return of peanut root biomass (CR2); and (iv) return of all residue of the whole peanut plant (CR3). The 31.5 and 21% of the labeled ¹⁵N isotope were accumulated in the above-ground tissues (leaves and stems) of peanuts and wheat, respectively. N rhizodeposition of peanuts and wheat accounted for 14.91 and 3.61% of the BG¹⁵N, respectively. The ¹⁵N from the below-ground ¹⁵N-labeled of peanuts were supplied 11.3, 5.9, 13.5, and 6.1% of in the CR0, CR1, CR2, and CR3 treatments, respectively. Peanut straw contributes a significant proportion of N to the soil through the decomposition of plant residues and N rhizodeposition. With the current production level on the NCP, it is estimated that peanut straw can potentially replace 104 500 tons of synthetic N fertilizer per year. The inclusion of peanut in rotation with cereal can significantly reduce the use of N fertilizer and enhance the system sustainability.     

Steam explosion of crop straws improves the characteristics of biochar as a soil amendment

Five crop straws(wheat, rice, maize, oil-rape, and cotton) were first steam-exploded for 2 min at 210°C, 2.5 MPa and then pyrolyzed at 500°C for 2 h. Steam explosion(SE) induced 47–95% and 5–16% reduction of hemicellulose and cellulose, respectively, in the crop straws. The biochars derived from SE-treated feedstocks had a lower specific surface area(SSA) and pore volume, compared to those from pristine feedstocks, with one exception that SE enhanced SSA of oil-rape straw biochar by approximately 16 times. After SE, biochars had significant higher anion exchange capacity(AEC)(6.88–11.44 cmol kg~(–1)) and point of zero net charges(PZNC)(pH 3.61–5.32) values. It can thus be speculated that these biochars may have higher potential for anions adsorption. In addition, oil-rape straw might be suitable to SE pretreatment for preparing biochar as a soil amendment and sorbent as well. Further work is required for testing its application in soil.     

Residue management induced changes in soil organic carbon and total nitrogen under different tillage practices in the North China Plain

Crop residue retention has been considered a practicable strategy to improve soil organic carbon(SOC) and total nitrogen(TN), but the effectiveness of residue retention might be different under varied tillage practices. To evaluate the effects of residue management on the distribution and stocks of SOC and TN under different tillage practices, a bifactorial experiment with three levels for tillage practices(no-tillage, rotary tillage, and conventional tillage) and two levels for residue managements(residue retention and residue removal) was conducted in the North China Plain(NCP). Results showed that after a short experimental duration(3–4 years), concentrations of SOC and TN in the 0–10 cm layer were higher under no-tillage than under conventional tillage, no matter whether crop residues were retained or not. Residue retention increased SOC and TN concentrations in the upper layers of soil to some degree for all tillage practices, as compared with residue removal, with the greatest increment of SOC concentration occurred in the 0–10 cm layer under rotary tillage, but in the 10–30 cm layer under conventional tillage. The stocks of SOC in the 0–50 cm depth increased from 49.89 Mg ha–1 with residue removal to 53.03 Mg ha–1 with residue retention. However, no-tillage did not increase SOC stock to a depth of 50 cm relative to conventional tillage, and increased only by 5.35% as compared with rotary tillage. Thus, residue retention may contribute more towards SOC sequestration than no-tillage. Furthermore, the combination between residue retention and no-tillage has the greatest advantage in enhancing SOC and TN in the NCP region.     

Correlation of production constraints with the yield gap of apple cropping systems in Luochuan County,China

Apple occupies a dominant position in fruit production globally, and has become the main income source of local smallholder farmers in Luochuan County in the Loess Plateau area, one of the largest apple production areas in China. However, the annual productivity of apple orchards in this region remains low and has gradually declined over the years. The distinction and correlation of production constraints can contribute to the promotion of apple orchard productivity and the development of a sustainable orchard system. In the present study, survey data from 71 smallholder farmers were analyzed using a yield gap model to distinguish the production constraints and determine their correlation with the yield gap based on the structural equation model(SEM). The results indicated that the average apple yield in Luochuan County was 29.9 t ha~(–1) yr~(–1), while the attainable yield(Y_(att); the highest yield obtained from the on-farm surveys) was 58.1 t ha~(–1) yr~(–1). The average explained and unexplainable yield gaps were 26.3 and 1.87 t ha~(–1) yr~(–1). According to the boundary line analysis, crop load,number of sprayings and base fertilizer N were the top three constraints on apple production in 9.8, 7.8 and 7.8% of the plots, respectively. Among the production constraints, crop load and fruit weight affected apple yield through direct pathways,whereas other constraints influenced apple yield through an indirect pathway based on the SEM, explaining 51% of the yield variance by all the main production constraints. These results can improve the current understanding of production constraints and contribute to the development of management strategies and policies for improving apple yield.     

Field effect of Cnaphalocrocis medinalis granulovirus (CnmeGV) on the pest of rice leaffolder

Rice leaffolder, Cnaphalocrocis medinalis(Guenée), has become a major pest throughout the rice cultivating areas of China and caused severe damage to rice production. Cnaphalocrocis medinalis granulovirus(CnmeGV), a naturally occurring baculovirus, is revealed as a potential microbial agent for the pest control. Field applications of CnmeGV were conducted against rice leaffolder larvae in rice paddies. CnmeGV infected the larvae not only in the current generation but also in the successive generation, resulting in a sustained infection in the larva population for at least 48 days. Under diferent concentrations of CnmeGV(7.5×10~(11) and 1.125×10~(12) occlusion body(OB) ha~(-1)) at 30 days after spraying, larval population reduced up to 76.32% and rice leaf rolled rate kept in 15.42%. Simultaneously, CnmeGV had no impact on arthropod predators of C. medinalis, with abundances ranging from 2.39 to 3.79 per ten hills. These results revealed that CnmeGV is suitable as a bio-pesticide for rice leaffolder management in rice paddies.