Propylea japonica (Coleoptera: Coccinellidae) is a natural enemy insect with a wide range of predation in Chinese mainland and is commonly used in pest management.  However, its genetic pattern (i.e., genetic variation, genetic structure, and historical population dynamics) is still unclear, impeding the development of biological control of insect pests.  Population genetic research has the potential to optimize strategies at different stages of the biological control processes.  This study used 23 nuclear microsatellite sites and mitochondrial COI genes to investigate the population genetics of Propylea japonica based on 462 specimens collected from 30 sampling sites in China.  The microsatellite dataset showed a moderate level of genetic diversity, but the mitochondrial genes showed a high level of genetic diversity.  Populations from the Yellow River basin were more genetically diverse than those in the Yangtze River basin.  Propylea japonica has not yet formed a significant genealogical structure in China, but there was a population structure signal to some extent, which may be caused by frequent gene flow between populations.  The species has experienced population expansion after a bottleneck, potentially thanks to the tri-trophic plant–insect–natural enemy relationship.  Knowledge of population genetics is of importance in using predators to control pests.  Our study complements existing knowledge of an important natural predator in agroecosystems through estimating its genetic diversity and population differentiation and speculating about historical dynamics.

Jincheng orange (Citrus sinensis Osbeck) is widely grown in Chongqing, China, and is commonly consumed because of its characteristic aroma contributed by the presence of diverse volatile compounds.  The changes in aroma during the development and maturation of fruit are indicators for ripening and harvest time.  However, the influence of growth stages on the volatile compounds in Jincheng orange remains unclear.  In addition, volatiles originate from fatty acids, most of which are the precursors of volatile substances.  On this basis, gas chromatography–mass spectrometry (GC–MS) was performed to elaborate the changes in volatile constituents and fatty acids as precursors.  This study tested proximately 60 volatiles and 8 fatty acids at 9 growth and development stages (AF1–AF9).  Of those compounds, more than 92.00% of total volatiles and 87.50% of fatty acids were terpenoid and saturated fatty acids, respectively.  As shown in the PCA plot, the AF5, AF6, and AF9 stages were confirmed as completely segregated and appeared different.  In addition, most of the volatiles and fatty acids first increased at the beginning of the development stage, then decreased from the AF6 development stage, and finally increased at the AF9 maturity stage.  Moreover, the highest contents of terpenoid, alcohols, aldehydes, ketones, and saturated fatty acids in Jincheng orange peel oil were d-limonene, linalool, octanal, cyclohexanone, and stearic acid during development stages, respectively.  Our results found that the growth stages significantly affected the volatile constituents and precursors in Jincheng orange peel oil.

Soil salinization is a critical environmental issue restricting agricultural production.  Deep return of straw to the soil as an interlayer (at 40 cm depth) has been a popular practice to alleviate salt stress.  However, the legacy effects of straw added as an interlayer at different rates on soil organic carbon (SOC) and total nitrogen (TN) in saline soils still remain inconclusive.  Therefore, a four-year (2015–2018) field experiment was conducted with four levels (i.e., 0, 6, 12 and 18 Mg ha^–1) of straw returned as an interlayer.  Compared with no straw interlayer (CK), straw addition increased SOC concentration by 14–32 and 11–57% in the 20–40 and 40–60 cm soil layers, respectively.  The increases in soil TN concentration (8–22 and 6–34% in the 20–40 and 40–60 cm soil layers, respectively) were lower than that for SOC concentration, which led to increased soil C:N ratio in the 20–60 cm soil depth.  Increases in SOC and TN concentrations in the 20–60 cm soil layer with straw addition led to a decrease in stratification ratios (0–20 cm:20–60 cm), which promoted uniform distributions of SOC and TN in the soil profile.  Increases in SOC and TN concentrations were associated with soil salinity and moisture regulation and improved sunflower yield.  Generally, compared with other treatments, the application of 12 Mg ha^–1 straw had higher SOC, TN and C:N ratio, and lower soil stratification ratio in the 2015–2017 period.  The results highlighted that legacy effects of straw application as an interlayer were maintained for at least four years, and demonstrated that deep soil straw application had a great potential for improving subsoil fertility in salt-affected soils.

Exploring the effects of sowing date and ecological points on the yield of semi-winter wheat is of great significance.  This study aims to reveal the effects of sowing date and ecological points on the climate resources associated with wheat yield in the Rice–Wheat Rotation System.  With six sowing dates, the experiments were carried out in Donghai and Jianhu counties, Jiangsu Province, China using two semi-winter wheat varieties as the objects of this study.  The basic seedlings of the first sowing date (S1) were planted at 300×10⁴ plants ha⁻¹, which was increased by 10% for each of the delayed sowing dates (S2–S6).  The results showed that the delay of sowing date decreased the number of days, the effective accumulated temperature and the cumulative solar radiation in the whole growth period.  The yields of S1 were higher than those of S2 to S6 by 0.22–0.31, 0.5–0.78, 0.86–0.98, 1.14–1.38, and 1.36–1.59 t ha^–1, respectively.  For a given sowing date, the growth days increased as the ecological point was moved north, while both mean daily temperature and effective accumulative temperature decreased, but the cumulative radiation increased.  As a result, the yields at Donghai County were 0.01–0.39 t ha^–1 lower than those of Jianhu County for the six sowing dates.  The effective accumulative temperature and cumulative radiation both had significant positive correlations with yield.  The average temperature was significantly negatively correlated with the yield.  The decrease in grain yield was mainly due to the declines in grains per spike and 1 000-grain weight caused by the increase in the daily temperature and the decrease in the effective accumulative temperature.

Dry direct-seeded rice (DDR) sown using a multifunctional seeder that performs synchronous rotary tillage and sowing has received increased attention because it is highly efficient, relatively cheap, and environmentally friendly.  However, this method of rice production may produce lower yields in a rice–wheat rotation system because of its poor seedling establishment.  To address this problem, we performed field experiments to determine the rice yield at five seedling density levels (B1, B2, B3, B4, and B5=100, 190, 280, 370, and 460 seedlings m⁻², respectively) and clarify the physiological basis of yield formation.  We selected a representative high-quality rice variety and a multifunctional seeder that used in a typical rice–wheat rotation area in 2016 and 2018.  The proportion of main stem panicle increased with increasing seedling density.  There was a parabolic relationship between yield and seedling density, and the maximum yield (9.34−9.47 t ha⁻¹) was obtained under B3.  The maximum yield was associated with a higher total spikelet number m⁻² and greater biomass accumulation from heading to maturity.  The higher total spikelet number m⁻² under B3 was attributed to an increase in panicle number m⁻² compared with B1 and B2.  Although the panicle numbers also increased under B4 and B5, these increases were insufficient to compensate for the reduced spikelet numbers per panicle.  Lower biomass, smaller leaf area, and lower N uptake per plant from the stem elongation stage to the heading stage were partially responsible for the smaller panicle size at higher seedling density levels such as B5.  The higher biomass accumulation under B3 was ascribed to the increases in the photosynthetic rate of the top three leaves m⁻² of land, crop growth rate, net assimilation rate, and leaf area index.  Furthermore, the B3 rice population was marked by a higher grain–leaf ratio, as well as a lower export ratio and transport ratio of biomass per stem-sheath.  A quadratic function predicted that 260−290 seedlings m⁻² is the optimum seedling density for achieving maximum yield.  Together, these results suggested that appropriately increasing the seedling density, and thereby increasing the proportion of panicles formed by the main stem, is an effective approach for obtaining a higher yield in DDR sown using a multifunctional seeder in a rice–wheat rotation system.

Denitrification-induced nitrogen (N) losses from croplands may be greatly increased by intensive fertilization.  However, the accurate quantification of these losses is still challenging due to insufficient available in situ measurements of soil dinitrogen (N₂) emissions.  We carried out two one-week experiments in a maize–wheat cropping system with calcareous soil using the ¹⁵N gas-flux (¹⁵NGF) method to measure in situ N₂ fluxes following urea application.  Applications of ¹⁵N-labeled urea (99 atom%, 130–150 kg N ha⁻¹) were followed by irrigation on the 1st, 3rd, and 5th days after fertilization (DAF 1, 3, and 5, respectively).  The detection limits of the soil N₂ fluxes were 163–1 565, 81–485, and 54–281 μg N m⁻² h⁻¹ for the two-, four-, and six-hour static chamber enclosures, respectively.  The N₂ fluxes measured in 120 cases varied between 159 and 2 943 (811 on average) μg N m⁻² h⁻¹, which were higher than the detection limits, with the exception of only two cases.  The N₂ fluxes at DAF 3 were significantly higher (by nearly 80% (P<0.01)) than those at DAF 1 and 5 in the maize experiment, while there were no significant differences among the irrigation times in the wheat experiment.  The N₂ fluxes and the ratios of nitrous oxide (N₂O) to the N₂O plus N₂ fluxes following urea application to maize were approximately 65% and 11 times larger, respectively (P<0.01), than those following urea application to wheat.  Such differences could be mainly attributed to the higher soil water contents, temperatures, and availability of soil N substrates in the maize experiment than in the wheat experiment.  This study suggests that the ¹⁵NGF method is sensitive enough to measure in situ N₂ fluxes from intensively fertilized croplands with calcareous soils.

Deep-sowing is an important method for avoiding drought stress in crop species, including maize.  Identifying candidate genes is the groundwork for investigating the molecular mechanism underlying maize deep-sowing tolerance.  This study evaluated four traits (mesocotyl length at 10 and 20 cm planting depths and seedling emergence rate on days 6 and 12) related to deep-sowing tolerance using a large maize population containing 386 inbred lines genotyped with 0.5 million high-quality single nucleotide polymorphisms (SNPs).  The genome-wide association study detected that 273 SNPs were in linkage disequilibrium (LD) with the genetic basis of maize deep-sowing tolerance.  The RNA-sequencing analysis identified 1 944 and 2 098 differentially expressed genes (DEGs) in two comparisons, which shared 281 DEGs.  By comparing the genomic locations of the 273 SNPs with those of the 281 DEGs, we identified seven candidate genes, of which GRMZM2G119769 encoded a sucrose non-fermenting 1 kinase interactor-like protein.  GRMZM2G119769 was selected as the candidate gene because its homologs in other plants were related to organ length, auxin, or light response.  Candidate gene association mapping revealed that natural variations in GRMZM2G119769 were related to phenotypic variations in maize mesocotyl length.  Gene expression of GRMZM2G119769 was higher in deep-sowing tolerant inbred lines.  These results suggest that GRMZM2G119769 is the most likely candidate gene.  This study provides information on the deep-sowing tolerance of maize germplasms and identifies candidate genes, which would be useful for further research on maize deep-sowing tolerance.

Manual fruit thinning (MFT) in fruit trees has been previously shown to increase fruit size and enhance fruit quality, but the effect of MFT on Ponkan (Citrus reticulata Blanco) and the underlying mechanisms remain poorly understood.  In this study, efforts were made to elucidate how MFT influences the fruit quality of Ponkan.  The results showed that MFT substantially increased fruit size and elevated fruit total soluble solids in comparison with the fruit from the unthinned trees (used as control).  Expression analyses demonstrated that mRNA abundance of three important sugar transporter genes, including CrSUT1, CrSTP1 and CrTMT1, was evidently elevated in the flesh of thinned fruit when compared with those of the control.  In addition, MFT prominently up-regulated the transcript levels of various auxin and gibberellin (GA) biosynthesis and signaling genes, including CrYUC6, CrAUX/IAA, CrGA20ox1 and CrGA3ox1.  Concurrently, the contents of endogenous IAA and GA₃, measured at 90 d after fruit thinning, were notably elevated in the fruit from trees with the thinning treatment relative to the control, although no difference was detected in the two groups before the thinning manipulation.  Taken together, these results indicate that manual fruit thinning could greatly improve fruit quality, which may be attributed to promoting fruit expansion due to the increased auxin levels and expediting sugar accumulation through the up-regulation of sugar transporter genes.

No tillage (NT) and straw return (S) collectively affect soil organic carbon (SOC).  However, changes in the organic carbon pool have been under-investigated.  Here, we assessed the quantity and quality of SOC after 11 years of tillage and straw return on the North China Plain.  Concentrations of SOC and its labile fractions (particulate organic carbon (POC), potassium permanganate-oxidizable organic carbon (POXC), microbial biomass carbon (MBC) and dissolved organic carbon (DOC)), components of DOC by fluorescence spectroscopy combined with parallel factor analysis (PARAFAC) and the chemical composition of SOC by ¹³C NMR spectroscopy were explored.  Treatments comprised conventional tillage (CT) and NT under no straw return (S0), return of wheat straw only (S1) or return of both wheat straw and maize residue (S2).  Straw return significantly increased the concentrations and stocks of SOC at 0-20 cm depth but no tillage stratified them with enrichment at 0-10 cm and a decrease at 10-20 cm in comparison to CT, especially under S2.  Labile C fractions showed similar patterns of variation to that of SOC, with POC and POXC more sensitive to straw return and the former more sensitive to tillage.  Six fluorescence components of DOC were identified comprising mostly humic-like substances with smaller amounts of fulvic acid-like substances and tryptophan. Straw return significantly decreased the fluorescence index (FI) and autochthonous index (BIX) and increased the humification index (HIX).  No tillage generally increased HIX in topsoil but decreased it and increased the FI and BIX below the topsoil.  The chemical composition of SOC was: O-alkyl C>alkyl-C>aromatic-C>carbonyl-C.  Overall, NT under S2 effectively increased SOC and its labile C forms and DOC humification in topsoil and microbially-derived DOC below the topsoil.  Return of both wheat and maize straw was a particularly strong factor for promoting soil organic carbon in the plough layer, and the stratification of SOC under no tillage may confer long-term influence on carbon sequestration.

Alginate oligosaccharides (AOS), belonging to the class of functional marine oligosaccharides, are low-molecular polymers linked by β-1,4-mannuronic acid (M) and α-1,4-guluronic acid (G), which could be classically obtained by enzymatic hydrolysis of alginate. With low viscosity and good water solubility, as well as anti-oxidant, immune regulation, anti-bacterial and anti-inflammatory activities, AOS have been widely used in medical science and functional food, green agriculture and other fields. As new bio-feed additives, AOS have broad potential applications in animal husbandry. In this review, the sources of alginate, chemical structure and preparation methods of AOS, and their biological activities and application in livestock and poultry are summarized. We expect this review could contribute to lay a foundation of application and further research for AOS in livestock and poultry.

Mechanical pot-seedling transplanting is an innovatively developed transplanting method that has the potential to replace mechanical carpet-seedling transplanting.  However, the initial pot-seedling transplanting machine lacked optimized density spacing and limited yield potential for japonica rice.  Therefore, ascertaining the optimized density by wide-narrow rows and the appropriate transplanting method for yield formation and grain quality of japonica rice is of great importance for high-quality rice production.  Field experiments were conducted using two japonica rice cultivars Nanjing 9108 and Nanjing 5055 under three transplanting methods in 2016 and 2017: mechanical pot-seedling transplanting with wide-narrow row (K, average row spacing of 30 cm); equidistant row (D, 33 cm×12 cm); and mechanical carpet-seedling transplanting (T, 30 cm×12.4 cm).  In addition, five different density treatments were set in K (K1–K5, from 18.62×10⁴ to 28.49×10⁴ hills ha^–1).  The results showed that the highest yield was produced by a planting density of 26.88×10⁴ hills ha^–1 in mechanical pot-seedling transplanting with wide-narrow row with a greater number of total spikelets that resulted from significantly more panicles per area and slightly more grain number per panicle, as compared with equidistant row, and yield among density in wide-narrow row showed a parabolic trend.  Compared with mechanical carpet-seedling transplanting, the treatment of the highest yield increased yield significantly, which was mainly attributed to the larger sink size with improved filled-grain percentage and grain weight, higher harvest index, and increased total dry matter accumulation, especially the larger amount accumulated from heading stage to maturity stage.  With the density in wide-narrow row decreasing, processing quality, appearance quality, and nutrition quality were all improved, whereas amylose content and the taste value were decreased.  Compared with mechanical carpet-seedling transplanting, mechanical pot-seedling transplanting improved processing quality and nutrition quality, but decreased amylose content and deteriorated appearance quality.  These results suggested that mechanical pot-seedling transplanting with wide-narrow row coupling produced a suitable planting density of 26.88×10⁴ hills ha^–1 and may be an alternative approach to improving grain yield and quality for japonica rice.

Mechanical transplanting with carpet seedlings (MC) and mechanical direct seeding (MD) are newly developed planting methods, which increase in popularity and planted area each year. Knowing the difference for yield and rice quality under different planting methods is of great importance for the development of high quality and yield cultivation techniques under mechanical conditions. Therefore, three kinds of japonica rice including hybrid japonica rice, inbreed japonica rice, and soft rice were adopted as materials. And the differences in the quality of processing, appearance, cooking and eating quality, nutrition, and the rapid viscosity analyzer (RVA) profile were studied to reveal the effects of planting methods on yield and quality of different types of japonica rice. Results showed that the milled rice and head rice rates under MC was significantly higher than those under MD, and the processing quality of inbreed japonica rice was the most stable. Compared with MC, length/width ratio of rice under MD was significantly increased, and chalkiness rate, size, and degree were significantly decreased. The protein content under MD was lower than that under MC. MC showed higher peak viscosity and breakdown value than MD. The taste value was the greatest for soft rice, followed by inbreed japonica rice, and then by japonica hybrid rice, with no significant differences resulting from planting methods. Compared with MC, MD significantly improved the appearance quality, though processing quality and nutritional quality were decreased. And there was no significant difference in cooking and eating quality between MC and MD. Under different planting methods, the appearance quality of inbreed japonica rice changed the most and the processing quality was the most stable. The nutritional, cooking and eating quality of soft rice changed the least. Therefore, according to the different planting methods and market needs, selecting the appropriate rice varieties can reduce the risks in rice production and achieve good rice quality.