Stigma color is a critical agronomic trait in watermelon that plays an important role in pollination.  However, there are few reports on the regulation of stigma color in watermelon.  In this study, a genetic analysis of the F₂ population derived from ZXG1553 (P₁, with orange stigma) and W1-17 (P₂, with yellow stigma) indicated that stigma color is a quantitative trait and the orange stigma is recessive compared with the yellow stigma.  Bulk segregant analysis sequencing (BSA-seq) revealed a 3.75 Mb segment on chromosome 6 that is related to stigma color.  Also, a major stable effective QTL Clqsc6.1 (QTL stigma color) was detected in two years between cleaved amplified polymorphic sequencing (CAPS) markers Chr06_8338913 and Chr06_9344593 spanning a ~1.01 Mb interval that harbors 51 annotated genes.  Cla97C06G117020 (annotated as zinc finger protein CONSTANS-LIKE 4) was identified as the best candidate gene for the stigma color trait through RNA-seq, quantitative real-time PCR (qRT-PCR), and gene structure alignment analysis among the natural watermelon panel.  The expression level of Cla97C06G117020 in the orange stigma accession was lower than in the yellow stigma accessions with a significant difference.  A nonsynonymous SNP site of the Cla97C06G117020 coding region that causes amino acid variation was related to the stigma color variation among nine watermelon accessions according to their re-sequencing data.  Stigma color formation is often related to carotenoids, and we also found that the expression trend of ClCHYB (annotated as β-carotene hydroxylase) in the carotenoid metabolic pathway was consistent with Cla97C06G117020, and it was expressed in low amounts in the orange stigma accession.  These data indicated that Cla97C06G117020 and ClCHYB may interact to form the stigma color.  This study provides a theoretical basis for gene fine mapping and mechanisms for the regulation of stigma color in watermelon. 

Agronomic measures are the key to promote the sustainable development of ratoon rice by reducing the damage from mechanical crushing to the residual stubble of the main crop, thereby mitigating the impact on axillary bud sprouting and yield formation in ratoon rice.  This study used widely recommended conventional rice Jiafuzhan and hybrid rice Yongyou 2640 as the test materials to conduct a four-factor block design field experiment in a greenhouse of the experimental farm of Fujian Agricultural and Forestry University, China from 2018 to 2019.  The treatments included fertilization and no fertilization, alternate wetting and drying irrigation and continuous water flooding irrigation, and plots with and without artificial crushing damage on the rice stubble.  At the same time, a ¹³C stable isotope in-situ detection technology was used to fertilize the pot experiment.   The results showed significant interactions among varieties, water management, nitrogen application and stubble status.  Relative to the long-term water flooding treatment, the treatment with sequential application of nitrogen fertilizer coupled with moderate field drought for root-vigor and tiller promotion before and after harvesting of the main crop, significantly improved the effective tillers from low position nodes.  This in turn increased the effective panicles per plant and grains per panicle by reducing the influence of artificial crushing damage on rice stubble and achieving a high yield of the regenerated rice.  Furthermore, the partitioning of ¹³C assimilates to the residual stubble and its axillary buds were significantly improved at the mature stage of the main crop, while the translocation rate to roots and rhizosphere soil was reduced at the later growth stage of ratooning season rice.  This was triggered by the metabolism of hormones and polyamines at the stem base regulated by the interaction of water and fertilizer at this time.  We therefore suggest that to achieve a high yield of ratoon rice with low stubble height under mechanized harvesting, the timely application of nitrogen fertilizer is fundamental, coupled with moderate field drying for root-vigor preservation and tiller promotion before and after the mechanical harvesting of the main crop.

Cyperus difformis L. is a troublesome weed in paddy fields and has attracted attention due to its resistance to acetohydroxyacid synthase (AHAS) inhibitors.  It was found that the amino acid mutation in AHAS was the primary cause for the resistance of Cyperus difformis.  However, the effect of different mutations on AHAS function is not clear in Cyperus difformis.  To confirm the effect of mutations on AHAS function, six biotypes were collected, including Pro197Arg, Pro197Ser, Pro197Leu, Asp376Glu, Trp574Leu and wild type, from Hunan, Anhui, Jiangxi and Jiangsu provinces, China and the function of AHAS was characterized.  The AHAS in vitro inhibition assay results indicated that the mutations decreased the sensitivity of AHAS to pyrazosulfuron-ethyl, in which the I₅₀ (the half maximal inhibitory concentration) of wild type AHAS was 0.04 μmol L^–1 and Asp376Glu, Pro197Leu, Pro197Arg, Pro197Ser and Trp574Leu mutations were 3.98, 11.50, 40.38, 38.19 and 311.43 μmol L^–1, respectively.  In the determination of enzyme kinetics parameters, the Km and the maximum reaction velocity (Vmax) of the wild type were 5.18 mmol L^–1 and 0.12 nmol mg^–1 min^–1, respectively, and the Km values of AHAS with Asp376Glu, Trp574Leu, Pro197Leu and Pro197Ser mutations were 0.38–0.93 times of the wild type.  The Km value of the Pro197Arg mutation was 1.14 times of the wild type, and the Vmax values of the five mutations were 1.17–3.33-fold compared to the wild type.  It was found that the mutations increased the affinity of AHAS to the substrate, except for the Pro197Arg mutation.  At a concentration of 0.0032–100 mmol L^–1 branched-chain amino acids (BCAAs), the sensitivity of the other four mutant AHAS biotypes to feedback inhibition decreased, except for the Pro197Arg mutation.  This study elucidated the effect of different mutations on AHAS function in Cyperus difformis and provided ideas for further study of resistance development.

 

Heavy metal contamination has been regarded as an environmental variable that affects the efficiency of pest biological control, but the parasitic fitness of parasitoids under heavy metal stress is poorly understood.  Herein, the effect of Cd exposure through the host pupa of Hyphantria cunea on the parasitic fitness of Chouioia cunea was investigated, and the mechanism by which Cd exposure affects the interaction between H. cunea and C. cunea from the perspective of innate immunity in host insect and the oxidative status in the parasitoid offspring was explored.  Our results indicated that Cd can be transferred from the H. cunea pupae to the parasitoid offspring, and the transfer coefficient reflected biological amplification.  There were no significant differences in the rates of parasitism success and offspring emergence between the untreated and Cd-treated groups.  However, after parasitizing Cd-accumulated pupae, the parasitic fitness of offspring wasps (e.g., the number, individual size and life span) decreased significantly.  Under Cd exposure, the cellular and humoral immunity of H. cunea pupae decreased significantly.  Compared with the untreated group, the H₂O₂ content of parasitoid offspring in the Cd-treated group was significantly increased.  Cd exposure significantly inhibited superoxide dismutase activity in parasitoid offspring, but the contents of ascorbic acid and glutathione were significantly increased by Cd stress.  Taken together, these results indicate that Cd exposure reduces the cyclic utilization efficiency of C. cunea on H. cunea pupae.  The oxidative status of parasitoid offspring triggered by Cd exposure could be responsible for the reduced parasitic fitness of C. cunea on Cd-accumulated H. cunea pupae.

In order to establish grading standards of evaluation indices for sour flavor of apples, 10 indices of samples from 106 apple cultivars were tested, including: malic acid (Mal), oxalic acid (Oxa), citric acid (Cit), lactic acid (Lac), succinic acid (Suc), fumaric acid (Fum), total organic acids (ToA, the sum of the six organic acids tested), titratable acid (TiA), acidity value (AcV), and pH value.  For most of the cultivars studied (85.8%), the order of the organic acid contents in apples was Mal>Oxa>Cit>Lac>Suc>Fum.  Mal was the dominant organic acid, on average, accounting for 94.5% of ToA.  Among the 10 indices, the dispersion of pH value was the smallest with a coefficient of variation of only 8.2%, while the coefficients of variation of the other nine indices were larger, ranging between 31 and 66%.  There were significant linear relationships between Mal and two indices (ToA and AcV) as well as between ToA and AcV.  There were significant logarithmic relationships between pH value and four indices: Mal, TiA, ToA, and AcV.  All the equations had very high fitting accuracy and can be used to accurately predict related indices.  According to this study, Mal, ToA, and AcV of apple were normally distributed, TiA was close to normally distributed, whereas pH value had a skewed distribution.  Using the fitted normal distribution curves, the grading standards of Mal, TiA, ToA, and AcV were established.  The grading node values of pH value were obtained using the logarithmic relationship between pH value and Mal.  The grading standards of these five indices can be used to evaluate the sour flavor of apple.  This study provides a scientific basis for evaluating apple flavor and selecting apple cultivars.

Crop root system plays an important role in the water cycle of the soil-plant-atmosphere continuum. In this study, combined isotope techniques, root length density and root cell activity analysis were used to investigate the root water uptake mechanisms of winter wheat (Triticum aestivum L.) under different irrigation depths in the North China Plain. Both direct inference approach and multisource linear mixing model were applied to estimate the distribution of water uptake with depth in six growing stages. Results showed that winter wheat under land surface irrigation treatment (T_s) mainly absorbed water from 10–20 cm soil layers in the wintering and green stages (66.9 and 72.0%, respectively); 0–20 cm (57.0%) in the jointing stage; 0–40 (15.3%) and 80–180 cm (58.1%) in the heading stage; 60–80 (13.2%) and 180–220 cm (35.5%) in the filling stage; and 0–40 (46.8%) and 80–100 cm (31.0%) in the ripening stage. Winter wheat under whole soil layers irrigation treatment (Tw) absorbed more water from deep soil layer than T_s in heading, filling and ripening stages. Moreover, root cell activity and root length density of winter wheat under T_w were significantly greater than that of T_s in the three stages. We concluded that distribution of water uptake with depth was affected by the availability of water sources, the root length density and root cell activity. Implementation of the whole soil layers irrigation method can affect root system distribution and thereby increase water use from deeper soil and enhance water use efficiency.

The adsorption of Cu(II) from aqueous solution onto humic acid (HA) which was isolated from cattle manure (CHA), peat (PHA), and leaf litter (LHA) as a function of contact time, pH, ion strength, and initial concentration was studied using the batch method. X-ray absorption spectroscopy (XAS) was used to examine the coordination environment of the Cu(II) adsorbed by HA at a molecular level. Moreover, the chemical compositions of the isolated HA were characterized by elemental analysis and solid-state 13C nuclear magnetic resonance spectroscopy (NMR). The kinetic data showed that the adsorption equilibrium can be achieved within 8 h. The adsorption kinetics followed the pseudo-second-order equation. The adsorption isotherms could be well fitted by the Langmuir model, and the maximum adsorption capacities of Cu(II) on CHA, PHA, and LHA were 229.4, 210.4, and 197.7 mg g–1, respectively. The adsorption of Cu(II) on HA increased with the increase in pH from 2 to 7, and maintained a high level at pH>7. The adsorption of Cu(II) was also strongly influenced by the low ionic strength of 0.01 to 0.2 mol L–1 NaNO3, but was weakly influenced by high ionic strength of 0.4 to 1 mol L–1 NaNO3. The Cu(II) adsorption on HA may be mainly attributed to ion exchange and surface complexation. XAS results revealed that the binding site and oxidation state of Cu adsorbed on HA surface did not change at the initial Cu(II) concentrations of 15 to 40 mg L–1. For all the Cu(II) adsorption samples, each Cu atom was surrounded by 4 O/N atoms at a bond distance of 1.95 Å in the first coordination shell. The presence of the higher Cu coordination shells proved that Cu(II) was adsorbed via an inner-sphere covalent bond onto the HA surface. Among the three HA samples, the adsorption capacity and affinity of CHA for Cu(II) was the greatest, followed by that of PHA and LHA. All the three HA samples exhibited similar types of elemental and functional groups, but different contents of elemental and functional groups. CHA contained larger proportions of methoxyl C, phenolic C and carbonyl C, and smaller proportions of alkyl C and carbohydrate C than PHA and LHA. The structural differences of the three HA samples are responsible for their distinct adsorption capacity and affinity toward Cu(II). These results are important to achieve better understanding of the behavior of Cu(II) in soil and water bodies in the presence of organic materials.

Germplasm resources are essential for the sustainable development of biodiversity and husbandry of local chickens, as well as for the breeding and industry of superior quality chickens. Unfortunately, many local and indigenous chicken breeds are at risk of declining numbers, emphasizing the need to conserve breed resources for endangered chickens. Primordial germ cells (PGCs) are crucial for preserving germplasm resources by inheriting genetic information from parents to offspring and ensuring stability of genetic material between germlines. In this study, PGCs were isolated from chicken embryos' gonads and cultured in FAcs medium without feeder cells. Over a period of approximately 40 days, the cells proliferated to a number of up to 10⁶, establishing various cell lines. Particularly, 18 PGC lines were created from Rugao Yellow Chicken and Shouguang Chicken, with an efficiency ranging from 39.1% to 45%. Furthermore, PGCs that had been cultured for 40 passages exhibited typical PGC characteristics, such as glycogen staining reaction, and expression of pluripotency and reproductive markers. These results confirm that PGCs maintain stem cell properties even after long-term in vitro culture. Additionally, PGCs cryopreserved for up to 120 days remained viable, maintained typical PGC morphologies, and possessed stable cell proliferation ability. Through intravascular injection into chicken embryos, green fluorescent protein (GFP)-PGCs were found in the recipient embryos' gonads and could develop into gametes to produce offspring, indicating that even after extended culture, PGCs retain their migratory and lineage-transmitting capabilities. This research offers valuable insights into the in vitro cultivation and preservation of PGCs of Chinese indigenous chickens. The findings of this study can be applied in transgenic chicken production and the preservation of genetic resources of indigenous chicken breeds.

Long-term excessive nitrogen (N) application does not increase or even decreases grain yield and N use efficiency (NUE) of maize, in which the roles of root morphological and physiological characteristics are not clear.  The goal of this study was to explain the mechanism underlying no increment in grain yield under excessive N application from the perspective of root morpho-physiological characteristics.  A 10-year long-term N fertilizer trial was conducted in Jilin Province, Northeast China, growing maize at three N fertilizer levels (zero N, N0; recommended N, N2; and high N level, N4) in 2019, 2020 and 2021.  Two widely planted maize genotypes: ‘Xianyu 335’ (XY335) and ‘Zhengdan 958’ (ZD958) were used.  Grain yield, N content, root morphology and other physiological characteristics were analyzed to further evaluate the relationships between N uptake, N utilization, plant growth, and root systems under different N treatments.  Compared with N0, root biomass, post-silking N uptake and grain yield were significantly improved with increased N input, whereas no significant differences were observed between recommended N and high N.  High N application increased root length and root surface area, but decreased root activity (measured by TTC (2,3,5-triphenyltetrazolium chloride) method), nitrate reductase activity and root activity absorbing area regardless of genotypes.  Root length and root to shoot ratio negatively contributed to N uptake (by -1.2% and -24.6%), while root surface area, root activity, nitrate reductase activity and root activity absorbing area were positively contributed to N uptake.  The interaction effect between cultivar and N application was significant on NUE.  XY335 obtained the highest NUE (11.6%) and N recovery efficiency (18.4%) through higher root surface area (23.6%), root activity (12.5%), nitrate reductase activity (8.3%) and root activity absorbing area (6.9%) compared with other treatments.  Overall, recommended N application promoted Post N uptake, NUE and grain yield by root surface area and root activity, nitrate reductase activity and root activity absorbing area, while high N application did not increase or even decreased NUE by reducing root surface area, root activity, nitrate reductase activity and root activity absorbing area.  Our case study successfully revealed that root surface area, root activity, nitrate reductase activity and root activity absorbing area were the limiting factors of NUE increase under high N application.

Soil compaction has become a seriously limitation for further increasing grain yield of maize (Zea mays L.) in the North China Plain (NCP).  However, considerable variability exists among maize hybrids in their grain yield response to soil compaction.  To understand the physiological processes relate to the variation of responses to various soil compactions among maize hybrids, a two-year field experiment was conducted with 17 maize hybrids and three soil compaction treatments (NC, no compaction, SBD, soil bulk density=1.0-1.3 g cm^-3; MC, moderate compaction, SBD=1.4-1.5 g cm^-3, and HC, heavy compaction, SBD>1.6 g cm^-3) to examine the root and shoot morphological traits, dry matter accumulation, and grain yield.  Compared to NC, MC and HC significantly decreased maize yield by 0.9-26.7% and 5.9-41.1% across hybrids and years, respectively.  High compaction tolerance (H) had greater grain yield than hybrids of middle compaction tolerance (M) and low compaction tolerance (L), particularly under HC.  Yield benefits obtained from H hybrid were enhanced due to better root and shoot growth under HC condition.  Greater root length, root surface area, and root weight, as well as root activity, absorption capacity, and antioxidant capacity for H hybrid were found under HC condition, and then maintained increased leaf area index and dry matter accumulation.  Moreover, the increases of root growth indices for H hybrid were greater than that of shoot growth, particularly under HC condition, leading to an increased root/shoot ratio.  We conclude that soil compaction impacts maize root and shoot growth differently depending on genotype, and root growth advantages of H hybrid were more obviously than shoot growth, which enhanced the yield benefits from H hybrid under heavy compaction condition.