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Due to the high resistance/reactance (R/X) ratio of a low-voltage microgrid (LVMG), virtual complex impedance-based P-· V/Q-ω droop control is adopted in this article as the primary control (PC) technique for stabilizing the system. A distributed event-triggered restoration mechanism (ETSM) is proposed as the secondary control (SC) technique to restore the output-voltage frequency and improve power sharing accuracy. The proposed ETSM ensures that neighboring communication happens only at some discrete instants when a predefined event-triggering condition (ETC) is fulfilled. In general, the design of the ETC is the crucial challenge of an event-triggered mechanism (ETM). Thus, in this article, a static ETM (SETM) is proposed as the ETC at first, where two static parameters are utilized to reduce the triggering frequency. Bounded stability is ensured under the SETM, which means that the output-voltage frequency is restored to the vicinity of its nominal value, and close to fair utilization of the distributed generators (DGs) is achieved. To further improve the power sharing accuracy and accelerate the regulation process, a dynamic ETM (DETM) is then introduced. In the DETM, two dynamic parameters that converge to zero in the steady state are designed, which promises asymptotic stability of the system. Besides, Zeno behavior is excluded in both mechanisms. An LVMG consisting of four DGs is constructed in MATLAB/Simulink to illustrate the effectiveness of the proposed methods, and the simulations correspond with our theoretical analysis.

In the light of user-side energy power control requirements, a power control strategy for a household-level EPR based on HES droop control is proposed, focusing on the on-grid, off-grid and seamless switching process. The system operating states are divided based on the DC bus voltage information with one converter used as a slack terminal to stabilize the DC bus voltage and the other converters as power terminals. In the on-grid mode, the GCC and the HES are used as the main control unit to achieve on-grid stable operation, whereas in the off-grid mode, the PV, HES and LC are used as the main control unit at different voltages to achieve stable operation of the island network. Finally, a DC MG system based on a household-level EPR is developed using the PSCAD / EMTDC simulation platform and the results show that the control strategy can effectively adjust the output of each subunit and maintain the stability of the DC bus voltage.

Stem color is an important agronomic trait in zucchini ( Cucurbita pepo , C. pepo ) for robust seedings and high yield. However, the gene controlling this trait has not been characterized. This study identified a single locus accounting for dark green stem color in C. pepo ( CpDsc-1 ). Genetic analysis of this trait in segregation populations derived from two parental lines (line 296 with dark green stem and line 274 with light green stem) revealed that it was controlled by a single dominant gene (dark green vs. light green). Using the bulked segregant analysis method, CpDsc-1 was mapped to a 2.09 Mb interval on chromosome 15. Then this region was further narrowed down to 65.2 kb using linkage analysis in the F 2 population. Sequencing analysis revealed a 14 kb deletion between Cp4.1LG15g03420 and Cp4.1LG15g03360 , encoding a two-component response regulator-like protein (APRR2). The incomplete structures of the two APRR2 genes and the abnormal chloroplasts in line 274 might be the main reason for the light green phenotype. Gene expression pattern analysis showed that only Cp4.1LG15g03420 was upregulated in line 296. The subcellular localization analysis indicated that Cp4.1LG15g03420 was a nuclear gene. Furthermore, a co-dominant marker G4563 (93% accuracy rate) and a co-segregation marker Fra3 were established in 111 diverse germplasms, and both were tightly linked with the color trait. This study provide new insight into the chlorophyll regulation pathway, and these markers would be valuable for marker-assisted selection in zucchini breeding.

Cp4.1LG15g03420 (CpDsc-1), which encodes a two-component response regulator-like protein (APRR2) in the nucleus, influences dark green stem formation in Cucurbita pepo by regulating the chlorophyll content. Stem color is an important agronomic trait in zucchini (Cucurbita pepo) for robust seeding and high yield. However, the gene controlling the stem color has not been characterized. In this study, we identified a single locus accounting for the dark green stem color of C. pepo (CpDsc-1). Genetic analysis of this trait in segregated populations derived from two parental lines (line 296 with dark green stems and line 274 with light green stems) revealed that stem color was controlled by a single dominant gene (dark green vs. light green). In bulked segregant analysis, CpDsc-1 was mapped to a 2.09-Mb interval on chromosome 15. This region was further narrowed to 65.2 kb using linkage analysis of the F

In recent years, air circulation has been used in protected cultivation to improve the microenvironment around seedlings, which in turn enhances photosynthesis and seedling growth. However, a practical and precise air circulation device has not yet been reported, especially one for growing seedlings in a greenhouse. Considering the use of a seedbed in seedling cultivation, a blower that can move back and forth on the seedbed and accurately control the air velocity is designed. In this experiment, we take the nonblowing treatment as the control (CK); three air velocities (0.3, 0.6, and 0.9 m/s) were selected to investigate the effect of interval blowing on the microenvironment of the canopy, physiology of seedling growth, stomatal characteristics of leaves, and stem mechanics of tomato seedlings. The three air velocities were found to significantly reduce the canopy temperature by 0.44, 0.78, and 1.48 °C lower than the CK, respectively, and leaf temperature by 0.83, 1.57, and 2.27 °C lower than the CK, respectively, in cultivated seedlings during summer. The relative humidity of the tomato seedling canopy decreased by 2.7% to 7.0%. Compared with the CK, the plant height of tomato seedlings decreased by 13.54% and root dry mass, root-shoot ratio, and seedling quality index (SQI) increased by 34.63%, 21.43%, and 14.29%, respectively, at 0.6 m/s. In addition, mechanical indexes such as hardness and elasticity of the tomato seedling stem were higher under air disturbance than those of the CK. The best effect was seen in the treatment with the air velocity of 0.6 m/s, in which the hardness and elasticity of the stem base and the first node were significantly higher than that of the CK. In conclusion, air disturbance generated by the air blowing device we designed effectively improved the microenvironment around the plants, enhanced the physiological activity of the seedlings, and thereby promoted seedling growth.

Begonia semperflorens (B. semperflorens), belonging to the family Begoniaceae, has now been widely cultivated worldwide and is famous for its ornamental plants with colourful flowers and distinctive leaves. The selection of appropriate internal reference genes is very important to accurately determine target gene expression via quantitative real-time PCR. However, internal reference gene selection has never been conducted in B. semperflorens. In this study, seven candidate reference genes of B. semperflorens, including 18S ribosomal RNA (Bs18S), pentatricopeptide repeat-containing protein (BsPPR), actin-related protein 5 isoform X2 (BsACT), DNAJ homologue subfamily C member 17 (BsDNAJ), glyceraldehyde-3-phosphate dehydrogenase (BsGAPDH), NAD-dependent malic enzyme 59 kDa isoform, mitochondria (BsNAD-ME), and peptidyl-prolyl cis-trans isomerase CYP26-2, chloroplast (BsCYP), which were obtained from our previous studies, were selected. The stabilities of these genes under stress conditions were analysed using geNorm and NormFinder. Validation of target gene expressions, including phenylalanine ammonia-lyase (BsPAL) and respiratory burst oxidase homologue D (BsRBOHD) under biotic and abiotic conditions, phenylalanine ammonia-lyase (BsPAL), anthocyanidin synthase (BsANS), chalcone synthase (BsCHS), and flavanone-3-hydroxylase (BsF3H) under low temperature, using these seven internal reference genes for normalisation further confirmed the stabilities of the selected genes and indicated the need for reference gene selection for normalising gene expressions in B. semperflorens. Of the seven candidate reference genes, the combination of BsACT, BsDNAJ, and BsNAD-ME was the ideal reference gene set for normalising gene expression in samples under biotic conditions. BsCYP combined with BsACT or BsGAPDH was the best reference gene pair under abiotic conditions. BsACT and BsPPR could be combined to normalise gene expression under low temperature. Our results will benefit future studies on gene expression in plants of Begoniaceae.

The WRKY transcription factors play important roles in various physiological processes, especially in regulating plant resistance to environmental stresses. Watermelon (Citrullus lanatus) plants suffer from various stressful climate conditions during their growth, especially cold stress. However, little information about the exact role of WRKYs in watermelon responses to cold was available. In this study, a total of 57 candidate ClWRKY genes from watermelon genome were identified and they were distributed unevenly on 11 chromosomes. After excluding five ClWRKY genes with incomplete WRKY domains, phylogenetic analysis showed that the remaining 52 ClWRKY genes could be divided into three groups with 11 members in Group 1, 34 in Group 2, and seven in Group 3. The ClWRKY genes in group 2 could be further classified into five subgroups with three members in 2a, five in 2b, 13 in 2c, six in 2d, and seven in 2e, respectively. The expression profiles of ClWRKY genes in response to cold stress could be classified into four types: four ClWRKY genes had little or no change in transcript levels, seven ClWRKY genes had irregular expression patters, 17 ClWRKY genes were upregulated, and 25 ClWRKY genes were downregulated. The different regulation patterns of ClWRKY genes in response to low-temperature treatment revealed that the WRKY gene family was crucial for cold stress tolerance and there were multiple regulatory pathways involved in cold resistance.

The coordinated scheduling of plug-in electric vehicle (PEV) charging should be constructed in distributed architecture due to the growing population of PEVs. Since the information and communication technology makes the adversary more permeable, the distributed PEV charging coordination is vulnerable to cyber-attack which may degrade the performance of scheduling and even cause the failure of scheduler task. Considering the tradeoff between system-wide economic efficiency, distribution level limitations and PEV battery degration, this paper investigates the resilient distributed coordination of PEV charging to resist cyber-attack, where the steps of detection, isolation, updating and recovery are designed synthetically. Under the proposed scheduling scheme, the misbehaving PEVs suffering from cyber-attack are gradually marginalized and finally isolated, and the remaining well-behaving PEVs obtain their own optimal charging strategy to minimize the total system cost in distributed architecture. The simulation results verify the effectiveness of theoretical method.

Simple sequence repeats (SSRs) are widely used in mapping constructions and comparative and genetic diversity analyses. Here, 103,056 SSR loci were found in Cucurbita species by in silico PCR. In general, the frequency of these SSRs decreased with the increase in the motif length, and di-nucleotide motifs were the most common type. For the same repeat types, the SSR frequency decreased sharply with the increase in the repeat number. The majority of the SSR loci were suitable for marker development (84.75% in Cucurbita moschata, 94.53% in Cucurbita maxima, and 95.09% in Cucurbita pepo). Using these markers, the cross-species transferable SSR markers between C. pepo and other Cucurbitaceae species were developed, and the complicated mosaic relationships among them were analyzed. Especially, the main syntenic relationships between C. pepo and C. moschata or C. maxima indicated that the chromosomes in the Cucurbita genomes were highly conserved during evolution. Furthermore, 66 core SSR markers were selected to measure the genetic diversity in 61 C. pepo germplasms, and they were divided into two groups by structure and unweighted pair group method with arithmetic analysis. These results will promote the utilization of SSRs in basic and applied research of Cucurbita species.

Considering the communication resources limitation, the hybrid-triggered mechanism based distributed control of islanded microgrids cluster is proposed, which can restore the frequency to the rated value and realize the active power sharing when the disturbance occurs. The hybrid-triggered mechanism consists of the self- and event-triggered mechanisms, which are configured at each leader and follower distributed generation to determine the inter-microgrids and intra-microgrid information transmission, respectively. The communication burdens can be sharply reduced since the information is transmitted aperiodically only when the proposed triggering conditions are satisfied under the hybrid-triggered mechanism. Moreover, Zeno behavior is analyzed to be avoided to make the hybrid-triggered mechanism reasonable and practicable for practical islanded microgrids cluster. The simulation verifies the effectiveness of theoretical results.

Due to the high R/X ratio and mismatched feeder impedance of low-voltage microgrids, conventional droop method is no longer able to decouple the active and reactive power of distributed generators and the power-sharing accuracy is degraded. In this article, a virtual complex impedance based $P-\dot{V}$ droop method is proposed to decouple the powers and improve the power-sharing accuracy among DGs. With the virtual impedance method, the equivalent impedance between virtual power source and point of common coupling is shaped to be purely resistive. Then, a $P-\dot{V}$ strategy is adopted to alleviate the effect of mismatched line impedance, where the virtual powers rather than the ordinary P/Q are used in the droop equation. In case the output voltage violates the operation code, a restoration mechanism is proposed to reset $\dot{V}$ to zero. Compared with existing virtual impedance and $Q-\dot{V}$ droop methods, the proposed method combines the advantages of both. Besides, a modified $P-\dot{V}$ strategy is also presented to accelerate the restoration process and improve the active power-sharing accuracy at the same time. Simulation results validate the effectiveness of the proposed method.

In this study, the role of Brassinosteroids (BRs) and the relationship between the mitochondrial alternative oxidase (AOX) and ROS in the BR-induced defence response to salt stress was studied in mustard plants. Salt stress induced a significant activation of AOX. Exogenous BR significantly enhanced the capacity of the cyanide-resistant pathway, and reduced the damage of cell membrane. Pretreatment with brassinazole (Brz, an inhibitor of the BR biosynthesis pathway) significantly blocked the capacity of the cyanide-resistant pathway. BR could partly recover the AOX inactivation under salicylhydroxamic acid (SHAM, an inhibitor of the cyanide-resistant pathway) pretreatment. It was also found that BR could enhance the ROS accumulation and the antioxidant enzyme activities, while the AOX could eliminate the excessive ROS and enhance the antioxidant enzyme activities. Furthermore, the suppression of the cyanide-resistant pathway significantly increased the MDA content and the electrolyte leakage in mustard leaves, and the suppression of the BR biosynthesis had little effect on their recovering. Taken together, the cyanide-resistant pathway was involved in BR-induced salt tolerance and played an important role in maintaining the permeability of the cell membrane.

Figure S1. The motif distribution of dinucleotide (A), trinucleotide (B) and tetranucleotide (C) in watermelon. Figure S2. The chromosome position of the 32 SSR markers in watermelon. Figure S3. Delta K distribution across various clusters (K) as estimated by Structure Harvester. (PDF 833Â kb)

The role of the mitochondrial alternative oxidase (AOX) pathway and the relationship between AOX and ethylene in resistance to Turnip mosaic virus (TuMV) were investigated in systemic infected mustard leaves. Expressions of AOX1a and ethylene biosynthesis-related genes were enhanced in the upper uninoculated leaves at 6 days of postinoculation (dpi). Increased accumulation of AOX1a transcript and reduced levels of TuMV-CP were also observed after pretreatment with AA (a cytochrome pathway inhibitor) or ACC (an ethylene precursor) at non-lethal concentrations. Meanwhile, application of AVG (an ethylene biosynthesis inhibitor) mostly blocked TuMV-induced AOX activity and substantially increased TuMV susceptibility in the upper leaves. SHAM (AOX pathway inhibitor) pretreatment partially reduced the ACC-induced cyanide-resistant respiration and TuMV resistance. Conversely, AA and SHAM pretreatments had little effect on generation of ethylene. These results suggested that the TuMV-induced increase of AOX was partly involved in the ethylene pathway, and ethylene unregulated AOX in upper uninoculated mustard leaves.

A new alternative oxidase (AOX) gene, designated as BjAOX1a, of mustard (Brassica juncea) was cloned by reverse transcription-polymerase chain reaction (RT-PCR). The full-length cDNA of BjAOX1a was 1,346 bp in size and containing an open reading frame (ORF) of 1,083 bp in size. The predicted amino acid sequence exhibited 82.17% homology to the alternative oxidase of Arabidopsis thaliana. Analysis of functional regions revealed that the BjAOX1a protein contained several metal-binding regions, α-helical regions, and cysteine residues, similar to other AOX1 proteins. Pretreatment of mustard plants with salicylhydroxamic acid (SHAM), an inhibitor of AOX protein, inhibited AOX activity and promoted systemic movement of the coat protein of Turnip mosaic virus (TuMV), whereas pretreatment of plants with antimycin A (AA), a cytochrome pathway inhibitor, inhibited the systemic movement of the coat protein of TuMV. Furthermore, H2O2 and O2− contents were enhanced following SHAM pretreatment. Thus, AOX1 might alleviate reactive oxygen species (ROS) and enhance resistance of mustard plants to TuMV, and could serve as a critical component in TuMV resistance.

This study investigated the cold responses of watermelon plants modulated by the alternative oxidase (AOX) pathway. Salicylhydroxamic acid was used in watermelon (Citrullus lanatus) plants in order to chemically inhibit the AOX pathway. After exposure to cold temperature (10°C) for 24 h, the SHAM-treated plants showed more serious cold-induced damage compared to non-treated plants. To investigate how the AOX pathway modulated the watermelon plants’ responses to cold, a polymerase chain reaction (PCR)-based suppression subtractive hybridization technique was used to isolate genes differently expressed between cold-stressed leaves of SHAM-treated and non-treated watermelon germplasm “IVSM No. 9”. After sequencing 400 randomly chosen cDNA clones, 314 uniquely expressed sequence tags (ESTs) were obtained. A total of 114 ESTs encoded unknown proteins or had no similarity in the database. Identified genes with significant protein homology mainly participated in stress and defense responses, metabolism and energetic processes, regulation of gene expression, signal transduction, protein fate and synthesis, cellular transport and others. These results indicated that watermelon plants could not respond appropriately to cold stress and suffer greater damage with an inhibited AOX pathway, thus, the AOX pathway had an important role in defining the plants cold responses.

Grain yield is the most important and complex trait in maize. In this study, a total of 258 F(9) recombinant inbred lines (RIL), derived from a cross between dent corn inbred Dan232 and popcorn inbred N04, were evaluated for eight grain yield components under four environments. Quantitative trait loci (QTL) and their epistatic interactions were detected for all traits under each environment and in combined analysis. Meta-analysis was used to integrate genetic maps and detected QTL across three generations (RIL, F(2:3) and BC(2)F(2)) derived from the same cross. In total, 103 QTL, 42 pairs of epistatic interactions and 16 meta-QTL (mQTL) were detected. Twelve out of 13 QTL with contributions (R(2)) over 15% were consistently detected in 3-4 environments (or in combined analysis) and integrated in mQTL. Only q100GW-7-1 was detected in all four environments and in combined analysis. 100qGW-1-1 had the largest R(2) (19.3-24.6%) in three environments and in combined analysis. In contrast, 35 QTL for 6 grain yield components were detected in the BC(2)F(2) and F(2:3) generations, no common QTL across three generations were located in the same marker intervals. Only 100 grain weight (100GW) QTL on chromosome 5 were located in adjacent marker intervals. Four common QTL were detected across the RIL and F(2:3) generations, and two between the RIL and BC(2)F(2) generations. Each of five important mQTL (mQTL7-1, mQTL10-2, mQTL4-1, mQTL5-1 and mQTL1-3) included 7-12 QTL associated with 2-6 traits. In conclusion, we found evidence of strong influence of genetic structure and environment on QTL detection, high consistency of major QTL across environments and generations, and remarkable QTL co-location for grain yield components. Fine mapping for five major QTL (q100GW-1-1, q100GW-7-1, qGWP-4-1, qERN-4-1 and qKR-4-1) and construction of single chromosome segment lines for genetic regions of five mQTL merit further studies and could be put into use in marker-assisted breeding.

With the development of the integrated production technology of computer processor, the calculation ability of microcomputer increases, while the price of minicom decreases continually. The new dispatching automation operation platform, which harmonize the minicom and microcomputer, not only took advantages of Unix platform's operation stability, high data processing ability and high security, but also have Windows' friendly man-machine interface, convenient to manipulate and maintain, and it has become the inevitable developing tendency for the electric power dispatching automation system. This paper first states the project for associated platform system which has been used in China, then introduces the structure, design idea, pivotal technology of ON2000, the integrated automation system based on Unix/Windows associated platform, finally, states the application of ON2000 system. (5 pages)

Background Microsatellite markers are one of the most informative and versatile DNA-based markers used in plant genetic research, but their development has traditionally been difficult and costly. The whole genome sequencing with next-generation sequencing (NGS) technologies provides large amounts of sequence data to develop numerous microsatellite markers at whole genome scale. SSR markers have great advantage in cross-species comparisons and allow investigation of karyotype and genome evolution through highly efficient computation approaches such as in silico PCR. Here we described genome wide development and characterization of SSR markers in the watermelon (Citrullus lanatus) genome, which were then use in comparative analysis with two other important crop species in the Cucurbitaceae family: cucumber (Cucumis sativus L.) and melon (Cucumis melo L.). We further applied these markers in evaluating the genetic diversity and population structure in watermelon germplasm collections. Results A total of 39,523 microsatellite loci were identified from the watermelon draft genome with an overall density of 111 SSRs/Mbp, and 32,869 SSR primers were designed with suitable flanking sequences. The dinucleotide SSRs were the most common type representing 34.09 % of the total SSR loci and the AT-rich motifs were the most abundant in all nucleotide repeat types. In silico PCR analysis identified 832 and 925 SSR markers with each having a single amplicon in the cucumber and melon draft genome, respectively. Comparative analysis with these cross-species SSR markers revealed complicated mosaic patterns of syntenic blocks among the genomes of three species. In addition, genetic diversity analysis of 134 watermelon accessions with 32 highly informative SSR loci placed these lines into two groups with all accessions of C.lanatus var. citorides and three accessions of C. colocynthis clustered in one group and all accessions of C. lanatus var. lanatus and the remaining accessions of C. colocynthis clustered in another group. Furthermore, structure analysis was consistent with the dendrogram indicating the 134 watermelon accessions were classified into two populations. Conclusion The large number of genome wide SSR markers developed herein from the watermelon genome provides a valuable resource for genetic map construction, QTL exploration, map-based gene cloning and marker-assisted selection in watermelon which has a very narrow genetic base and extremely low polymorphism among cultivated lines. Furthermore, the cross-species transferable SSR markers identified herein should also have practical uses in many applications in species of Cucurbitaceae family whose whole genome sequences are not yet available. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2870-4) contains supplementary material, which is available to authorized users.