Table of Content

20 September 2018, Volume 27 Issue 9

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Orignal Article

Characterization of greenhouse gases emissions from rainfed soils in different cropping systems on the Loess Plateau

DENG Chang-fang, LUO Zhu-zhu, LI Ling-ling, NIU Yi-ning, CAI Li-qun, ZHANG Ren-zhi, XIE Jun-hong

2018, 27(9):  1-13.  DOI: 10.11686/cyxb2017530

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This paper compares the effects of different lucerne planting patterns on the dynamic flux of soil greenhouse gases (CO₂, CH₄ and N₂O) in dry farmlands of the Loess Plateau.Effects of soil temperature, soil water content, and soil enzyme activities on greenhouse gas emissions were studied, using static chamber gas chromatographic techniques to measure CH₄ and N₂O and a LI-8100 measurement system to determine CO₂ flux. The research included 6 treatments: lucerne-lucerne (L-L), lucerne-fallow (L-F), lucerne-wheat (L-W), lucerne-corn (L-C), lucerne-potato (L-P) and lucerne-millet (L-M). The results showed that farmland soil served not only as source of atmospheric CO₂ and N₂O,but also as sink of atmospheric CH₄, with seasonal gas fluxes higher in summer and autumn than in spring and winter. L-L had the highest cumulative emission of CO₂ and L-W had decreased 42% compared with it, while L-C had the highest cumulative emission of N₂O and L-P had the lowest. The CH₄ absorption of L-M was higher by 62.71% and 31.87%, respectively, than L-F and L-L.The calculated global warming potential was L-L>L-M>L-C>L-P>L-F>L-W. Correlation analysis showed there were significant relationships between greenhouse gas fluxes and activities of soil enzymes urease, and catalase, and with soil temperature (P<0.01).Gas fluxes were also correlated with soil water content in some soil layers; stepwise regression analysis found that soil temperature and catalase activities were the dominant factors affecting CO₂ and CH₄ flux. Soil temperature influenced greenhouse gas emission significantly. N₂O flux displayed no significant correlation with biological factors, but was positively correlated with soil temperature and soil water content. In general, planting of other crop species after lucerne cropping reduced intensity of soil greenhouse gas emission, and the overall greenhouse gas emission of the farmland, and the treatment L-W was the most effective.

Structural features of Lycium ruthenicum communities and associated soil characteristics on different types of desert rangeland in the lower reaches of the Shiyang River

GUO Chun-xiu, MA Jun-mei, HE Fang-lan, WANG Li-de, LI Jin-hui, AN Fu-bo, YUAN Hong-bo, LIU Kai-lin

2018, 27(9):  14-24.  DOI: 10.11686/cyxb2017440

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The species composition and soil characteristics of black wolfberry communities in four different types of desert rangeland (loose sand dunes, salt flats, gravels, vegetated or semi-vegetated dunes) in the lower reaches of the Shiyang river were studied. Key content of this paper includes: 1) Among the plant communities investigated, there were 31 species (12 shrub plants, 8 perennial herbs and 11 annual herbs) belonging to 9 families and 28 genera. Hence the community structure at each studied site typically comprised a few families represented by a single taxon from one or more genera. Lycium ruthenicum had a dominance role in each of the 4 communities with ‘importance values’ of 58.9%, 17.6%, 18.2% and 38.1%, respectively, for the above 4 site categories. Only at the gravel flats site was another species more important (Setaria viridis, 28.9%). 2) A range of soil chemical properties are tabulated for 0-10 cm, 10-20 cm, 20-40 cm, and 40-60 cm soil depths. Soil organic C for the 0-10 cm soil depth was 0.30%, 1.08%, 0.29%, and 0.37% (mean s.e.±0.05%), respectively, for loose dune, salt flat, gravel and vegetated dune sites. The measured soil properties generally did not vary significantly with soil depth, but along with SOC, soil total P and available K were markedly higher in saline flats than at the other site categories. 3) Site rankings for soil microbial biomass were saline soil (-300 mg·kg^-1)>loose sand>vegetated dunes>gravel (-125 mg·kg^-1). Soil enzyme activities are reported for the 4 soil depths for catalase, sucrose, urease, phosphatase and invertase, and were highest in the saline soil in each case. 4) There was a significant positive correlation between soil organic matter and microbial biomass carbon, microbial biomass nitrogen, phosphatase and sucrase (P<0.01), and a significant positive correlation with urease and catalase (P<0.05). Phosphorus content was significantly positively correlated with urease, phosphatase and invertase (P<0.01), and positively correlated with microbial biomass carbon (P<0.05). Soil available potassium content was significantly positively correlated with microbial biomass nitrogen and phosphatase (P<0.01).

Leaf decomposition and nutrient release characteristics of different plant species in the Loess Hilly region

LIU Jing, XIE Wan-yu, ZHANG Qiao-ming, XU Shao-jun

2018, 27(9):  25-33.  DOI: 10.11686/cyxb2017442

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The decomposition of leaf litter has important significance for nutrient cycling in ecosystems. Robinia pseudoacacia, Pinus tabulaeformis and Festuca arundinacea are commonly used species for returning farmland to forests in the Loess Hilly Region of western Henan, and Caragana korshinskii is a widely distributed herbaceous plant in this region.We studied the differences in decomposition characteristics of R. pseudoacacia, P. tabulaeformis, F. arundinacea and C. korshinskii leaf litter, using a nylon bag method. Leaf litter of F. arundinacea decomposed, respectively, 8.86%, 19.87% and 13.18% faster than litter of R. pseudoacacia, P. tabulaeformis and C. korshinskii. Leaf litter decomposition processes followed Olson’s exponential model. Decay rates for leaf litter of the 4 species ranked F. arundinacea>R. pseudoacacia>C. korshinskii>P. tabulaeformis. During the decomposition process, the C/N and P content the leaf litter of 4 litters species decreased gradually but the lignin content increased slowly, while the cellulose content initially increased and then decreased. Change with time in C and P concentration of decomposing leaf litter followed a ‘direct release’ model, while N concentration followed an ‘enrichment-release’ model. The concentrations of total C, and lignin and the C/N ratio were significantly, negatively correlated with decomposition rate of the leaf litters (P<0.01).Therefore, the concentrations of total C, lignin and C/N ratio in leaf litter samples could be used as decomposition indicators to predict litter decay rate in this region. We also noted that physical characteristics of leaf litter (specific leaf area, thickness, hardness, etc.) are additional factors with important effects on leaf litter decomposition rate.

Effects of tillage method and straw mulching on grain yield and protein content in wheat and soil nitrate residue under a winter wheat and summer soybean crop rotation in drylands

HUANG Ming, WU Jin-zhi, LI You-jun, WANG He-zheng, FU Guo-zhan, CHEN Ming-can, LI Xue-lai, MA Jun-li

2018, 27(9):  34-44.  DOI: 10.11686/cyxb2017439

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Based on a long-term field experiment to compare different cropping patterns, conducted in western Henan province, the effects of tillage method and straw mulching on wheat productivity and soil nitrate residue in drylands under a winter wheat (Triticum aestivum) and summer soybean (Glycine max) rotation were investigated from October 2014 to June 2016. The experiment included four treatments: plough tillage (PT); plough tillage with straw mulching (PTSM); rotary tillage (RT); and rotary tillage with straw mulching (RTSM). The plant nitrogen (N) absorption and utilization, grain yield, grain protein content in wheat and the nitrate residue in the 0-200 cm soil depth were measured. Compared with PT, RT did not change grain yield, but decreased post-anthesis N accumulation, grain protein content and protein yield in wheat by 60.0%, 8.6% and 13.0%, respectively, and increased nitrate residue in 0-200 cm soil depth by 28.6%. Compared with no mulching, straw mulching with the same tillage method increased not only the spike numbers, kernels per spike, 1000-kernel weight and harvest index, but also the pre-jointing and post-anthesis N accumulation and N translocation from vegetative organs to the grain in wheat. As a result, the grain yield, N uptake efficiency, grain protein content and protein yield under PTSM were 11.5%, 13.5%, 7.4% and 21.3% higher than that under PT, and the corresponding values for RTSM were, respectively, 23.0%, 39.5%, 12.8% and 38.5% higher than that under RT. At wheat maturity after seven years of continuous cropping, PTSM decreased the nitrate residue in the 0-200 cm soil depth by 31.3% compared with PT, whereas RTSM decreased the nitrate residue by 51.4% compared with RT. Therefore, straw mulching is an alternative cropping technique because it can not only increase the N uptake efficiency, grain yield, grain protein content and protein yield in wheat, but also decrease soil nitrate residue under winter wheat and summer soybean rotation in drylands, especially for the RTSM treatment.

Effects of soil particle composition on seed germination and seedling growth of Paspalum wettsteinii under different temperatures

WANG Yu-zhen, HUANG Xiao, CAI Li-ping, ZHENG Hui-xin, HOU Xiao-long, ZHOU Chui-fan, ZHANG Hong, HUANG Peng-ping, HUA Cong

2018, 27(9):  45-55.  DOI: 10.11686/cyxb2018012

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In order to explore the effects of soil surface texture (sand and fine gravel) on seed germination and seedling growth in regions vulnerable to soil erosion, the effects of temperature and soil particle composition on seed germination and seedling growth of Paspalum wettsteinii were assessed. The study utilized topsoil collected from eroding areas to use as substrate, with 4 different temperatures (15, 20, 25 and 30 ℃) and 5 soil mixtures created by mixing different soil particle composition based on soil particle diameter. The results showed that the temperature and soil particle composition had a significant influence on seed germination and seedling growth of P. wettsteinii. The time to initiation of seed germination after seeding reduced, the duration of seed germination shortened, and the germination rate increased as temperature rose from 15 to 30 ℃. The seed germination rate, germination energy and seedling biomass at 20 and 25 ℃ were higher than other temperatures. The germination index, vigor index and seedling growth at 20, 25, 30 ℃ were significantly higher than that at 15 ℃. The root-shoot ratio of seedlings initially decreased and then increased, but was lowest at 25 ℃. The seed germination indexes were lowest in the soil with the composition of 100% coarse particles and highest in the soil with the composition of 25% or 50% coarse particles. With increasing coarse particles, the seedling shoot height increased, while the root length and root-shoot ratio of growth decreased. The above-ground and root biomass of seedlings were higher in the soil with the composition of 50% or 75% coarse particles. The results indicated that high proportion of coarse-grained soil was beneficial to shoot growth, while harmful to root growth, and the soil with the composition of 25%, 50% or 75% of coarse particles was propitious to seed germination and the accumulation of seedling biomass.

A study of the allelopathic effect of extracts from different parts of Iva xanthiifolia on five Brassicaceae species

YAO Shu-kuan, LI Feng-lan, PENG Li-na, FENG Xu, DONG Jia-min, FENG Zhe, ZHANG Jun-feng, ZHAO Qiao-qin, FENG Shan-shan, XU Yong-qing, HU Bao-zhong

2018, 27(9):  56-66.  DOI: 10.11686/cyxb2017398

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This study investigated the allelopathic effect of extracts of Iva xanthiifolia root and stem tissues on Raphanus sativus, Brassica campestris, Brassica pekinensis, Brassica juncea, and Brassica oleracea. In this study, the effects of different concentrations (10, 20, 30, 40 g·L^-1) aqueous extract on the germination and seedling growth of the above 5 Brassicaceae species were studied indoors to elucidate allelopathic effects of I. xanthiifolia on these crops indoors. Significant (P<0.05) allelopathic effects on the germination rate, germination potential, germination index, vigor index, root length, seedling height and fresh weight were found, and some differences in response among the five tested brassica species. A notable feature of the results were that growth promoted effects on seed germination and growth of R. sativus, B. pekinensis and B. campestris at the lowest treatment rate of 10 g·L^-1 I. xanthiifolia extract and inhibitory effects at higher rates, while B. juncea and B. oleracea were inhibited even at the lowest treatment rates. Stem extract of I. xanthiifolia was more potent than root extract, which indicated that the aqueous extract of the stem contained the main allelochemicals with inhibitory effects on seed germination and seedling growth. The results of this comprehensive allelopathy index evaluation, demonstrated that aqueous extracts of I. xanthiifolia exert a strong inhibitory effect on seedling growth of the five Brassicaceae species tested.

Evaluation of salt tolerance in different alfalfa varieties under uniform and non-uniform salt stress

XIONG Xue, GUI Wei-yang, LIU Mo-han, CHEN Ji-hui, ZHANG Ying-jun

2018, 27(9):  67-76.  DOI: 10.11686/cyxb2017461

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Soil salinity is rarely spatially uniform under field conditions; it varies greatly in the single plant rhizosphere. While many previous studies have assessed the effects of uniform salt stress on different plant varieties, much less is known about plant salt tolerance under non-uniform salt stress, which more closely resembles field salt conditions. The salt tolerance of six varieties of alfalfa were assessed at uniform salt stress (100, 200 mmol·L^-1NaCl) and non-uniform salt stress (0/200 mmol·L^-1NaCl) by using a split-root system. The plant growth rate, aboveground biomass, belowground biomass, water uptake, electric conductivity, malondialdehyde (MDA), chlorophyll (Chl) and proline (Pro) contents were measured. The membership function method was utilized to assess salt tolerance. Our results showed both uniform salt stress and non-uniform salt stress significantly decreased growth rate, above/below-ground biomass, water uptake, and chlorophyll content, while membrane permeability, malondialdehyde and proline increased at high salt stress. Varieties differed in their response to salt stress. The salt tolerance of each cultivar at uniform salt stress of 100 and 200 mmol·L^-1 NaCl was Zhongmu No.1>WL354HQ>WL343HQ>WL353LH>Algonquin>WL298HQ, non-uniform salt stress of 0/200 mmol·L^-1NaCl was Zhongmu No.1>WL354HQ>WL298HQ>WL343HQ>WL353LH>Algonquin. Zhongmu No.1 appeared to be the most tolerant cultivar to different salinity, whereas Algonquin had a lower salt tolerance. WL298HQ under uniform and non-uniform salt stress varied greatly while other cultivars showed a moderate salt tolerance.

Effects of DTA-6 seed soaking on morphological and leaf physiological characteristics in proso millet at seedling stage

ZHANG Pan-pan, WANG Xiao-lin, GUO Ya-ning, YAN Jia-kun, FENG Bai-li, ZHANG Xiong

2018, 27(9):  77-84.  DOI: 10.11686/cyxb2018056

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The aim of this research was to define the effect of diethyl aminoethyl hexanoate (DTA-6) seed soaking on morphology and leaf physiological characteristics in proso millet (Panicum miliaceum) at the seedling growth stage. Nianfeng 5 proso millet was the variety chosen for study, and seedling growth, leaf area per plant, leaf photosynthetic characteristics and carbohydrate accumulation of seedling plants were measured following seed soaking at different DTA-6 concentrations (0 [CK], 10, 50, or 250 mg·L^-1). It was found that DTA-6 enhanced seedling growth. Plant height, leaf dry weight, stem dry weight, and root dry weight under 250 mg·L^-1 DTA-6 treatment were, respectively increased by 55.73%, 277.99%, 162.88%, 123.55% compared to CK plants, while stem diameter was highest (54.18%>CK) in the 50 mg·L^-1 DTA-6 treatment, and the root:shoot ratio was highest (20.55%>CK) in the 10 mg·L^-1 DTA-6 treatment. DTA-6 significantly promoted leaf area per plant, leaf net photosynthetic rate and stomatal conductance, intercellular CO₂ concentration, but not leaf transpiration rate. Leaf area per plant, leaf stomatal conductance, and intercellular CO₂ were increased most in the 250 mg·L^-1 DTA-6 treatment, with values, respectively, 71.78%, 37.44% and 18.04% greater than CK, while net photosynthetic rate was highest in the 50 mg·L^-1 DTA-6 treatment. Carbohydrate levels of plants grown from seeds treated with DTA-6 showed different patterns compared to CK plants for different metabolites. DTA-6 reduced leaf soluble sugar content and fructose content, while sucrose content was increased to different degrees, but highest for the 50 mg·L^-1 DTA-6 treatment. In summary, DTA-6 seed soaking had marked effects on leaf photosynthetic characteristics, and improved leaf sucrose content, thereby enhancing the growth of proso millet plants. So, it is better to list the DTA-6 concentrations used the 50 mg·L^-1.

Effects of intercropping on the metabolism of carbon and nitrogen of soybean at the seedling stage and its relationship with lodging

REN Shen-mao, DENG Yu-chuan, WEN Feng-jun, LIU Ming-jie, YUAN Xiao-qin, Sajad Hussain, PU Quan-ming, LIU Wei-guo, YANG Wen-yu

2018, 27(9):  85-94.  DOI: 10.11686/cyxb2017455

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The purpose of this study was to clarify the role of photosynthetic capacity of soybean at the seedling stage in maize soybean intercropping. Our research studied the strongly shade tolerant soybean variety (Nandou 12) and weakly shade tolerant variety (Nan032-4), under soybean monoculture and maize soybean intercropping systems. The percentage of lodging,stem morphology, photosynthetic rate, carbon content and nitrogen metabolic activity of stems and leaves were measured. Compared with monoculture soybean, the stem length:diameter ratio was significantly increased by maize shading, but leaf photosynthetic rate and the lodging percentage were decreased. However, the degree of response differed between varieties. In the intercropping system, the stem morphology changes and increase in lodging were relatively small in the shade tolerant variety Nandou 12, and greater in the intolerant variety, Nan032-4. Lodging percentage was highly significantly correlated (r=0.946; P<0.01) with the stem length:diameter ratio, and negatively correlated with the photosynthetic rate (r=-0.886; P<0.05).Meanwhile, the photosynthetic rate was highly significantly positively correlated with the photosynthetically active radiation (r=0.900; P<0.01). The results show that shading by maize reduced the photosynthetically active radiation and photosynthetic rate, which in turn triggered plant height increase and stem diameter decrease responses, leading to increased plant lodging. Compared with soybean monoculture, the carbon:nitrogen ratio of intercropped soybean was significantly decreased by maize shading, but again Nandou 12 was significantly less affected than Nan032-4. Leaf photosynthetic rate was highly significantly and negatively correlated with the carbon:nitrogen ratios of leaf and stem (r=-0.871 and -0.930, respectively; P<0.05). The leaf and stem carbon:nitrogen ratios were highly significantly (r=0.985 and 0.968, respectively; P<0.01) and positively correlated with lodging percentage. These findings show that a high carbon:nitrogen ratio in soybean stem and leaf tissues provides a physiological basis for maintenance of higher lodging resistance and the variety with this trait (Nandou 12) was more suitable for intercrop planting than Nan032-4. Compared with soybean grown in monoculture, the content of carbon and nitrogen and photosynthetic activity and substrate export of stem and leaf tissue was significantly decreased when shaded by maize in the intercrop system. Soybean monoculture and maize soybean intercropping systems were used as in this study to explore the relationship between plant lodging, and carbon and nitrogen metabolism to provide a theoretical basis for development of appropriate fertilization management and cultivation practices to promote lodging resistance and identify varieties to lodging in intercropping systems.

The effect of jasmonic acid methylester on cell growth and β-ecdysterone accumulation in Ajuga lobata

WANG Xiao-mei, CHI De-fu, YU Jia

2018, 27(9):  95-109.  DOI: 10.11686/cyxb2017449

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High β-ecdysterone (β-EC) levels were contained in a cell suspension of Ajuga lobata. In order to further improve β-EC content, jasmonic acid methylester was added. The effects of adding jasmonic acid methylester was based on 4-10 generations of cell suspension of A. lobata and the influence of different MeJA concentrations and adding times on cell growth and β-EC accumulation was assessed. For β-EC content, high performance liquid chromatography (HPLC) was utilised. Results showed that the growth curve of the cell suspension and accumulative line of β-EC followed the Logistics model. Adding different concentrations of MeJA in the early (the 4th day of culture) or middle stages (the 7th day of culture) of the rapid cell growth period did not greatly affect cell growth; the growth curves were similar and each produced a peak. Adding MeJA on the 4th day and 7th day of culture resulted in peaks mostly occurring on the 5th and 3rd day after MeJA addition respectively. Dry weights of the cell suspension reached 0.60 g and 0.62 g respectively. Adding different concentrations of MeJA at the peak (the 10th day of culture) of rapid cell growth, resulted in a decline in growth in all cell cultures. The growth of suspended cells was significantly reduced by adding MeJA. Fresh and dry weights were usually significantly lower than that in the control group (P<0.05). The cell fresh weights were significantly correlated with β-EC contents after adding MeJA into the culture system during the early or middle stages of rapid cell growth. After adding 10-50 μmol·L^-1 MeJA cell fresh weights increased significantly compared with that of the control. Adding 50 μmol·L^-1 MeJA achieved the highest cell fresh weight (35.90 g), significantly higher than other treatments (P<0.05). Similarly β-EC content (0.5095 mg·g^-1) was also highest with 50 μmol·L^-1 MeJA. Adding 200 μmol·L^-1 MeJA, significantly reduced cell fresh weights compared with the control (38.88% reduction). After adding 100-200 μmol·L^-1 MeJA β-EC content was greatly increased, reaching 3.5315 mg·g^-1, 14.44 times the control treatment(P<0.01). At the peak of rapid cell growth (10th day of culture), adding 10-200 μmol·L^-1MeJA, reduced cell fresh weights compared with that of the control. The results illustrated that adding MeJA during cell growth could inhibit cell growth. Adding 10-50 μmol·L^-1 MeJA at the peak of rapid cell growth resulted in a massive surge in β-EC content shortly after adding, the highest level being 1.4136 mg·g^-1, 5.06 times the control (P<0.01). When the MeJA concentration reached 100-200 μmol·L^-1, the accumulation of β-EC was significantly reduced. We concluded that cell growth was mildly stimulated by adding 100 μmol·L^-1 MeJA treatment in the middle stage of cell rapid growth period with β-EC content reaching 3.5315 mg·g^-1.

Effects of epibrassinolide on ion absorption and distribution in Medicago species under NaCl stress

WANG Xiao-shan, JI Xiao-min, LIU Long-yang, JI Bing-qin, TIAN Yin-fang

2018, 27(9):  110-119.  DOI: 10.11686/cyxb2017413

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The aim of this study was to explore the mechanism of salt tolerance of Medicago species and the effect of exogenous brassinolide on salt tolerance of Medicago species. NaCl stress and the effects of epibrassinolide (EBR) on biomass, uptake, distribution and transport of Medicago species were studied under NaCl stress. Medicago truncatula, M. polymorphal and M. polymorpha were selected as experimental materials. The results show that NaCl stress inhibited the growth of Medicago plants and affect the distribution of K⁺, Ca²⁺, Mg²⁺ in plants. EBR effectively relieved the inhibitory effect of NaCl stress on plant growth, maintaining ion balance in plants and improving tolerance to salt. Salt tolerance in M. sativa was strong whereas tolerance in M. truncatula was poor. Under salt stress, the roots of M. sativa inhibited the uptake of Na⁺ to reduce the toxicity effects. M. truncatula transported Na⁺ from roots to the stem and leaves.

Effects of ethylene on the ascorbate-glutathione cycle and callose deposition in ISR disease-resistance reaction in creeping bentgrass

JIANG Han-yu, WANG Ya-feng, XU Ming, GAN Pei-wen, ZHANG Jin-lin, MA Hui-ling

2018, 27(9):  120-131.  DOI: 10.11686/cyxb2017429

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Creeping bentgrass seedlings cv. ‘Penn-A4’ infected with Rhizoctonia solani, which was produced by the induced-systemic-resistance (ISR) disease-resistance action induced by butanediol (BDO), was sprayed with different concentrations of the ethylene synthesis inhibitor, CoCl₂ and ethylene synthesis promoter, 1-amino cyclopropane carboxylic acid (ACC). Subsequently, changes inascorbic acid (AsA) and glutathione (GSH) contents and related enzyme activity in theascorbate-glutathione (AsA-GSH) cycle in seedlings were measured. Paraffin sectioning and fluorescence microscopy techniques were used to assess the effects of ethylene on callose deposition during ISR disease-resistance reactions. Under low ethylene concentrations AsA content was low and ascorbate peroxidase (APX) activity was reduced. A large amount of GSH was catalytically reduced to oxidize glutathione (GSSG) which accumulated. Glutathione reductase (GR) activity was low; GSSG is reduced to GSH by GR, consequently GSH remained at low levels. However, under high ethylene concentrations, AsA content was high and APX activity was higher. GSSG was catalytically reduced to GSH which accumulated. Therefore, in ISR disease-resistance reaction, high concentrations of ethylene induced the accumulation of AsA and GSH, which involved not only in the metabolic balance of reactive oxygen species, but also acted as signaling molecules playing an important role in the disease resistance of ISR. Callose was mainly deposited in sclerenchyma cells, phloem, xylem tissues and epidermis seedling leaves in ISR reaction induced by BDO. Callose deposition was highest in sclerenchyma cell and least in the epidermis. Callose deposition areas had differences in ethylene signal compounds but became less significant with reduced treatment time. Ethylene concentration affected callose deposition in ISR reaction induced by BDO; callose deposition increased significantly with reduced treatment time. Areas of callose deposition occupied 9.916 mm² under 100 μmol·L^-1 ACC treatment after 5 d, and increased to 38.396 mm² after 10 d. However, in the later stages of disease invasioncallose deposition area decreased to 20.052 mm² under 100 μmol·L^-1 ACC after 15 d. These results suggest that the ethylene molecular signalhas a short-term effect on callose deposition and increased the disease-resistance of creeping bentgrass. This research provides a theoretical basis for the exploration of ET signal molecules to control the physiological characteristics of resistance in ISR resistance response in creeping bentgrass.

Function of the soybean GmCYS20 gene in symbiotic nodulation of Lotus japonicus

KE Dan-xia, PENG Kun-peng, ZHANG Meng-ke, JIA Yan

2018, 27(9):  132-141.  DOI: 10.11686/cyxb2018042

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Cystatin plays an important role in the symbiotic relationship between leguminous plants and rhizobium. We cloned the soybean cystatin gene GmCYS20 (291 bp) for analysis in this study. The analysis of amino acid multiple sequence alignment with homologous proteins showed that the similarity between soybean GmCYS20 and wild soybean (Glycine soja) CYS was up to 99%. The plant overexpression vector was constructed and GmCYS20-overexpression composite plants were obtained in Lotus japonicas using the hairy root transformation method. Positive hairy roots were identified by GUS staining and RT-PCR assay. After inoculation with rhizobia for 4 weeks, overexpression of GmCYS20 increased the number of nodules in composite Lotus japonicus and up regulated the expression levels of symbiotic related genes. Further analysis of rhizobial infection phenotypes after inoculation with rhizobia for 10 days showed that overexpression of GmCYS20 gene did not affect the rhizobium infection process but played a positive role in initiation and development of nodules. These results showed that the GmCYS20 gene was involved in the regulation of symbiotic nodulation by promoting nodule initiation and development in L. japonicus. The results provide new molecular biological avenues to reveal the mechanisms of the symbiotic interaction between leguminous plants and rhizobium.

Interspecific relationships between hexaploid species in the Triticeae tribe with St, H and Y genomes

CHEN Shi-yong, MA Xiao, ZHANG Xin-quan, CHEN Zhi-hua, ZHOU Qing-ping

2018, 27(9):  142-151.  DOI: 10.11686/cyxb2018002

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Species with St, H and Y genomes comprise the largest group in the tribe Triticeae, which includes many important forage grasses and is the source of elite genes for improving forage and cereal crops. While this group has considerable economic and ecological value, the nature of its inter genera and interspecific relationships remains a matter a dispute, especially for hexaploid species. Relatively little research has been undertaken on interspecific relationships among these species, which has limited the ability to utilize their germplasm resources. Therefore, this study aimed to reveal the interspecific affinity of the group’s hexaploid species and so to provide important information on their genetic diversity and biosystematics. A total of 25 hexaploid species with StHY, StStY, StStH and StHH genomic constitutions were systematically collected and highly transferable SSR markers were used to study their genetic variation, differentiation and affinity. A total of 229 bands were amplified based on 27 SSR markers, of which 213 bands were polymorphic (93.01%). Based on SSR data, the Dice genetic similarities coefficient ranged from 0.479 to 0.981, with an average of 0.670. The GS coefficients among StHY species ranged from 0.544-0.981 (average 0.722), while StStY species ranged from 0.509-0.899 (average 0.700), StStH species from 0.530-0.843 (average 0.663) and StHH species from 0.550-0.827 (average 0.677). The results revealed abundant genetic variation and differentiation among the species studied. Moreover, clustering based on the unweighted pair group with arithmetic mean method showed that species with the same or similar genomic constitution could be grouped together. However, some species with the same genomic constitution were highly differentiated. Those with the StHY genome divided into three distinct types, with these types also corresponding with species’ morphology. The results indicate that the genomic constitution of hexaploid species of Elymus in China are of the StHY type. Overall, the results showed that there is rich genetic diversity and differentiation among the hexaploid species and that those with the same or similar genomes have close phylogenetic relationships. These results provide a systematic basis for the classification of the hexaploid species of Elymus and Roegneria based on their genomic constitution.

Genetic analysis and QTL mapping for seven agronomic traits in maize (Zea mays) using two connected populations

ZHAO Xiao-qiang, FANG Peng, PENG Yun-ling, ZHANG Jin-wen, ZENG Wen-jing, REN Bin, GAO Qiao-hong

2018, 27(9):  152-165.  DOI: 10.11686/cyxb2017438

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Seven important agronomic traits that influence the ecological adaptability, lodging resistance, dense planting ability and the production potential of maize are plant height (PH), ear height (EH), panicle aspect ratio (PAR), leaf area (LA), leaf shape coefficient (LSC), anthesis-silking interval (ASI) and tassel branch number (TBN). In order to analyze the heterosis of these seven traits, two F₂ populations were derived from crosses of Langhuang×TS141 (LTpop) and Chang7-2×TS141(CTpop). Analysis was also undertaken to reveal the relationship between these traits and ear weight (EW), and to detect QTLs and their corresponding QTL effects. The results showed that: 1) The PAR and ASI of the two F₁ hybrids showed significant mid-parent heterosis, while the other traits showed significant positive over-parent heterosis. The F₁ heterosis index and relative heterosis results were consistently PH>EH>TBN>LA>LSC>ASI>PAR. However, the F₂ advantage reduction rate results were LA>PH>EH>TBN>ASI>LSC>PAR. 2) EW was significantly negatively correlated with ASI and was significantly positively correlated with the other six traits. Moreover, except for TBN, optimal regression equations between EW and the other six traits were successfully constructed via stepwise regression analysis. 3)56 QTLs were detected in the two F₂ populations using composite interval mapping (CIM), with the results explaining 4.22%-15.74% of phenotypic variation per QTL. For these QTLs, PH, PAR, ASI and TBN showed both additive and non-additive effects, while the other traits showed non-additive effects. Further analysis identified 12 stable QTLs (sQTLs) in the two F₂ populations. These sQTLs were for PH (Bin1.07; umc1278-bnlg1025), LA (Bin1.08-1.10; mmc0041-phi308707), ASI (Bin2.02; umc1823-umc2363), EH and PAR (Bin4.06; bnlg1621a-umc2027), ASI and TBN (Bin4.09; umc2287-umc2360), ASI(Bin6.05; umc2040-bnlg1174a),TBN (Bin7.00; umc2177-umc1378), PAR (Bin8.08; umc1005-umc2218), and for PH and PAR (Bin10.01-10.02; bnlg451-umc1337). This study has provided valuable information for application in the breeding, precision mapping and positional gene cloning for desired agronomic traits in maize.

Effects of different dietary energy levels on apparent digestibility, nitrogen metabolism and growth performance of Tibetan sheep under low nitrogen conditions

KANG Jing-peng, WANG Wen-ji, GUO Ya-min, JING Xiao-ping, ZHONG Chong-liang, GUO Wei, LONG Rui-jun, ZHOU Jian-wei

2018, 27(9):  166-174.  DOI: 10.11686/cyxb2017443

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The objective of this study was to investigate the effects of different dietary energy levels on the apparent digestibility, nitrogen metabolism and growth performance of Tibetan sheep under low nitrogen conditions, and thus to provide useful references for the supplementary feeding of alpine ruminants during the cold season. Twenty-four healthy, 1.5-year-old castrated Tibetan sheep with similar body weights (48.5±1.89 kg)were selected and then divided into four treatment groups: LE (low energy), MLE (medium low energy), MHE (medium high energy) and HE (high energy). Each group included 6 replicates. Diets were formulated to have similar crude protein (CP) content (6.97%±0.05%) but four different digestible energy levels: 8.23, 9.31, 10.45 and 11.57 MJ·kg^-1 respectively. The animals were fed these diets for 49 days, with total collection of feces and urine for analysis. The results obtained were as follows: 1) Dry matter (DM), CP and gross energy (GE) intakes were similar among the four groups, whereas DM and GE apparent digestibilities all increased linearly with rising dietary energy levels (P<0.05). 2) Serum free fatty acid (FFA) concentration decreased linearly as dietary energy increased (P<0.05) while urea nitrogen (BUN) increased (P<0.05). 3) As dietary energy levels increased, urinary nitrogen excretion decreased linearly (P<0.05); however, the nitrogen balance and nitrogen deposition rates both increased (P<0.05). There was a strong linear regression between nitrogen deposition rates (NDR, %) and dietary energy levels (DE, MJ·kg^-1): NDR=5.2143DE-39.006 (R²=0.9616,n=24). 4) With the exception of the low energy group, all the average daily gain (ADG) values were positive and increased linearly with dietary energy (P<0.05).These results indicate that while the energy and protein requirements of Tibetan sheep are relatively low their apparent digestibility, nitrogen metabolism and growth performance could be improved with supplements of dietary energy.

Effects of different dietary fiber on growth performance, intestinal development and digestive enzyme activity of piglets

LIU Bo-shuai, WANG Wen-jing, SUN Xiao, LI De-feng, ZHU Xiao-yan, LI Zhen-tian, WANG Cheng-zhang, SHI Ying-hua, QIU Xiao-dong

2018, 27(9):  175-182.  DOI: 10.11686/cyxb2017514

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The objective of this study was to explore the effects of different types of dietary fiber on the growth performance, intestinal development and digestive enzyme activities of piglets. A total of 840 piglets (Duroc×Landrace×Large×White, aged 32 days) with a body weight of (9.26±0.17) kg were randomly allotted to three treatments: a basic diet group (CG), an alfalfa meal group(AG) and a commodity fiber concentrate group(OG). Each treatment included four replicated pens with 70 piglets apiece. Intestinal weight and length, the small intestine villus morphology structure and its digestive enzyme activity concentration were measured after 25 days. The results showed that compared with CG, AG significantly reduced the piglets’ diarrhea rate (P<0.05), but that it had no significant effects on average daily gain (ADG), average daily feed intake (ADFI) or the feed:gain ratio (P>0.05). Compared with CG, AG and OG significantly increased the length and weight of piglets’ large intestine (P<0.05), while AG improved the villus height (VH) and villus height/crypt depth (VH/CD) of jejunum (P>0.05). Compared with OG, AG significantly increased VH and VH/CD (P<0.05). Compared with CG, OG significantly increased ileum VH (P<0.05) and significantly decreased amylase activity in jejunum (P<0.05). Compared with CG and OG, AG significantly increased chymotrypsin activity (P<0.05). These results show that adding appropriate amounts of alfalfa meal to piglets’ diet could promote intestinal development and reduce diarrhea rates, thus facilitating their growth and development.

The history of alfalfa cultivation and utilization in the Sui and Tang Dynasties

SUN Qi-zhong, LIU Qian, TAO Ya, LI Feng, XU Li-jun

2018, 27(9):  183-193.  DOI: 10.11686/cyxb2017453

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As one of the best available forages, alfalfa played an important role in the development of horse breeding in the Tang Dynasty that followed the Qin and Han Dynasties. The article applies the principles and methods of plant textual research to the records of the Sui, Tang and Five Dynasties in order to explore the history of alfalfa’s distribution, cultivation and utilization. The results showed that during the Tang Dynasty the development of alfalfa was promoted through 8 lanes, 48 imperial offices and 1296 land stations in Longyou. “Achievements praising monument of Longyou” (Song Dynasty) recorded that the total area of wheat and alfalfa had reached 1900 ha and was typically used for livestock feeding in winter in Song Dynasty. Investigations show that, during the Tang Dynasty, alfalfa was widely distributed across Longyou, Guannei, Hedongsandao, Anxidu, Pishadu, Weihe River and the lower reaches of the Yellow River regions. The “New Tang History Book”(Song Dynasty,1975) records that 4 ha of alfalfa were used to raise horses. “Six Codes of the Tang Dynasty” records the number of horses kept at post stations, with the biggest courier station raising 75 horses on 200 ha of alfalfa farmland and the smallest raising 8 horses and 21.33 ha of farmland. Croplands were similar to grazing land, with both types of land use focusing on growing alfalfa to solve the problem of feeding horses. Special departments were established during the Sui Dynasty to administer alfalfa planting, and were followed by the “Ding organization of alfalfa” in the Tang Dynasty. During the Tang Dynasty, laws were used to promote the cultivation of alfalfa and its use as fodder to solve the key problem faced by animal husbandry at that time, winter feeding. At this time, the cultivatinging technique was still used, a technique that was handed down from the Han Dynasty. Alfalfa was used not only for animal winter management but also as food, medicine and spice.The management experience and planting technologies developed during the Sui, Tang and Five Dynasties continue to have a positive effect on the development of alfalfa in China today.

Effects of excess manganese toxicity on growth and antioxidant enzyme activity in Stylosanthes guianensis seedlings

LIU Pan-dao, LUO Jia-jia, BAI Chang-jun, CHEN Zhi-jian, LIU Guo-dao

2018, 27(9):  194-200.  DOI: 10.11686/cyxb2017441

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The aim of this study was to investigate the potential mechanisms underlying stylo (Stylosanthes guianensis) tolerance to high Mn levels. The growth responses and Mn tolerance in stylo were assessed in two stylo genotypes, TF210 and TF226 grown hydroponically. Plant dry weight, root growth parameters, chlorophyll concentration (soil plant analyzer development, SPAD), maximum photochemical efficiency (F_v/F_m) as well as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were measured under two Mn levels. Results showed that significant decreases in shoots and roots growth, SPAD and F_v/F_m values were observed in stylo genotype TF210 compared to TF226 under 400 μmol·L^-1 MnSO₄ treatment, suggesting that TF226 was a more Mn-tolerant genotype compared to TF210. Although Mn content in shoots and roots of both genotypes was increased by high Mn treatment, Mn content in TF226 was lower than that in TF210, suggesting that less Mn was accumulated in TF226 compared to TF210. Furthermore, SOD, POD and CAT activities in leaves of TF226 were significantly increased under high Mn treatment, while only SOD activity in leaves of TF210 was increased by high Mn. Activities of the three tested enzymes in TF226 were higher than those in TF210 under high Mn. These results suggest that regulations of root growth, Mn accumulation and antioxidant enzyme activities might be the adaptive mechanisms of stylo tolerance to Mn toxicity. The present study not only provides theoretical basis for dissecting Mn tolerant mechanisms, but also providing germplasm resources for improving adaptation to Mn toxicity in stylo.

Effects of whole-plant corn silage on performance, digestibility and blood biochemical parameters in Simmental crossbred bulls

SUN Xue-li, LI Qiu-feng, LIU Ying-cai, CAO Yu-feng, WANG Zeng-lin, LI Yi, ZHAO Yang-yang, GE Han-cong, LIU Tao-tao, ZHAO Li-xin

2018, 27(9):  201-209.  DOI: 10.11686/cyxb2017417

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In this experiment, 45 healthy Simmental hybrid bulls weighing approximately 350 kg were randomly divided into three treatment groups that were fed different diets for a period of 140 d: GroupⅠ(concentrate +corn straw storage), Group Ⅱ (concentrate+whole-plant corn silage) and Group Ⅲ (concentrate+whole-plant corn silage+lactic acid bacteria compound preparation). The results showed that Group Ⅲ’s average daily gain was significantly higher than both Groups Ⅰ and Ⅱ (P<0.01). The daily gain of Group Ⅲ was 90.35% and 24.00% higher than Groups Ⅰ and Ⅱ respectively. The dry matter intake of Group Ⅰ was significantly higher than Groups Ⅱ and Ⅲ (P<0.01), while there were no significant differences between Groups Ⅱ and Ⅲ. The feed:gain ratio of Groups Ⅱ and Ⅲ were significantly lower than Group Ⅰ (P<0.01). The digestibility of crude protein (Measurement using the FOSS Automated Protein Analyzer (USA)[1])for Groups Ⅱ and Ⅲ was higher than Group Ⅰ (P<0.05), and especially so in the case of Group Ⅲ (P<0.01). The apparent digestibility of neutral detergent fiber and acid detergent fiber in Group Ⅲ were significantly higher than Group Ⅰ (P<0.05). The content of free fatty acids and leptin in Group Ⅰ were significantly higher than Groups Ⅱ and Ⅲ (P<0.05).The levels of bovine insulin-like growth factor in Groups Ⅱ and Ⅲ were significantly higher than Group Ⅰ(P<0.05) and there was also a significant difference between Groups Ⅱ and Ⅲ (P<0.05). The average daily benefit of Group Ⅲ was 22.21 yuan and 9.27 yuan higher than that of Groups Ⅰ and Ⅱ respectively. In conclusion, this experiment showed that, in terms of fattening effects and economic benefits, cattle diets with additive whole corn silage outperformed the other two treatments studied.