Table of Content

20 March 2016, Volume 25 Issue 3

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Orginal Article

Temporal and spatial distribution of grassland degradation in northern Tibet based on NDVI

CAO Xu-Juan, Ganjurjav H, LIANG Yan, GAO Qing-Zhu, ZHANG Yong, LI Yu-E, WAN Yun-Fan, DANJIU-Luobu

2016, 25(3):  1-8.  DOI: 10.11686/cyxb2015378

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An expansive alpine grassland ecosystem dominates the landscape in Northern Tibet, and the status of this grassland has significant implications for the major Asian rivers, and for the climate and eco-environment of Tibet and the wider region. The harsh natural environment and fragile ecosystem, together with increasing frequency and intensity of human activities such as pastoralism, and climate change, have resulted in increasing reports of degradation of the grassland ecosystem. We used vegetation cover as main indicator of ecosystem health, and with remote sensing monitoring, calculated the grassland degradation index (GDI) and evaluated grassland degradation in Northern Tibet from 2000 to 2010. The analysis was based on the Normalized Differential Vegetation Index (NDVI) data from the Advanced Very High-Resolution Radiometer (AVHRR) with a spatial resolution of 8 km from 1981 to 1985 and from Moderate Resolution Imaging Spectroradiometer (MODIS) with a spatial resolution of 0.25 km of 2000-2010. Then, we have analyzed the temporal and spatial distribution of grassland degradation in Northern Tibet from 2000 to 2010. It was found that grassland degradation in Northern Tibet was still severe. The GDI was 1.97 in 2010, near to seriously degraded status. The extremely seriously degraded and seriously degraded categories occupied 6.5% and 19.0% of the study area, respectively. The moderately and slightly degraded grassland categories accounted for 15.1% and 12.1%, respectively. Undegraded grassland occupied 41.8% of the total grassland area in 2010. The extent of extremely seriously degraded and seriously degraded categories was greatly increased in the data from 2000-2010, compared with the period from 1981-1985. However, the increase in grassland degradation in Northern Tibet from 2000 to 2010 was slight, with the mean value of the GDI being 1.84 in 2010, representing a change from light degradation to moderate degradation in Northern Tibet from 2000 to 2010.

Methods for estimating nitrogen, phosphorus and potassium content based on hyperspectral data from alpine meadows in Guinan and Maqin Counties, Qinghai province

GAO Jin-Long, HOU Yao-Chen, BAI Yan-Fu, MENG Bao-Ping, YANG Shu-Xia, HU Yuan-Ning, FENG Qi-Sheng, CUI Xia, LIANG Tian-Gang

2016, 25(3):  9-21.  DOI: 10.11686/cyxb2015268

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Using typical alpine meadows in Maqin and Guinan Counties in Qinghai province as the research area, hyperspectral data from 20 plots were collected by spectrometer, while the forage nutrient concentrations were measured in the laboratory for each plot. Using regression analysis, the correlations between the nitrogen, phosphorus and potassium contents of the alpine meadow forage and the original reflectance data and the first-order differential of reflectance were analyzed. Inversion models were established for estimating the nitrogen, phosphorus and potassium content of alpine meadow forage based on spectrum location, spectrum area and vegetation index, and the accuracy of the models was also evaluated. It was found that first-order differential reflectance curve better predicts nitrogen, phosphorus and potassium content in the forage, than does the original data. In the red band (680-760 nm), the nitrogen, phosphorus and potassium levels in forage show a strong relationship with canopy hyperspectral reflectance curve parameters. The model which included spectrum location worked well for estimating concentration of nitrogen, phosphorus, and potassium in alpine meadow forage. A logarithmic model for spectrum location (R'_708.88) can estimated forage nitrogen content with an R² of 0.67, and an accuracy of 83.56%, while a logarithmic model for spectrum location (R'_704.85) can estimated forage phosphorus content, with an R² of 0.55, and an accuracy of 92.15%, and a logarithmic model for spectrum location (R'_697.36) estimated potassium content, with an R² of 0.86, and an accuracy of 82.44%.

A comparative study of methods for monitoring plant diversity in montane shrub grassland in the Lhasa River Basin

LUO Li-Ming, WU Jian-Shuang, YU Cheng-Qun, PAN Ying, MIAO Yan-Jun, WU Jun-Xi, MING Sheng-Ping, GUO Ying-Jie

2016, 25(3):  22-31.  DOI: 10.11686/cyxb2015199

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Biodiversity is an important consideration in the monitoring and assessment of the ecological stability of rangelands in Tibet. Climate warming and grazing disturbance both threaten the stability of the Tibetan rangelands; hence, research into species succession, transition patterns and species diversity is important for the protection and utilization of grasslands in the region. A field survey was carried out to measure the community species composition and the species change along an altitudinal gradient in the Bailang village valley, Linzhou County in the Lhasa River Basin. Three conventional sampling methods, random square quadrats, repeat sampling lines and the Modified-Whittaker plots, were compared in this study. Key results were: (1) All three sampling methods indicated that α-diversity initially increased and then decreased with increasing altitude, though the line transect method using three 50 m transects detected more species than the other two methods. (2) The Sorensen similarity index and the Bray-Curtis index of β-diversity decreased with increasing altitude. (3) The intercept c and slope z of the relationship between species and sampling area showed unimodal patterns with increasing altitude as also did species richness. (4) In order to cover 80% of local plant species, the minimum sampling area should be up to 100 m². Future research should focus on the factors determining biodiversity distribution and community assembly in response to climate change and grazing disturbance.

Isolation and identification of endophytes infecting Stipa purpurea, a dominant grass in meadows of the Qinghai-Tibet Plateau

BAO Gen-Sheng, LI Chun-Jie

2016, 25(3):  32-42.  DOI: 10.11686/cyxb2015214

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Stipa purpurea is a dominant grass species in alpine grassland of the Qinghai-Tibet Plateau. Research on this species to date has focused on defining genetic diversity, community classification, ecological function, physiological traits and grassland community characteristics; however, isolation and identification of endophyte fungi from S. purpurea has seldom been attempted. Endophyte was isolated from S. purpurea by leaf surface sterilization and axenic culture, and hyphae, colony physical characteristics, and conidial morphology were observed. Endophyte nucleotide sequences were cloned by tubB, tefA, and actG specific primers, and representative endophyte sequences were downloaded from Genbank to determine homology. A maximum likelihood method was applied to construct a phylogenetic tree. It was found that endophyte occurrence in S. purpurea was relatively high in Qinghai province, compared to other sites. Colony morphology characteristics, growth speed and morphology of conidia were identical to those of Epichloё spp. The results of tubB and tefA phylogeny indicated that four endophyte strains isolated from S. purpurea were most closely related to Epichloё chisosa from North American Achnatherum eminens and formed two distinct branches. Four other endophyte strains isolated from S. purpurea were most closely related to Epichloё indbrians and Epichloё gansuensis, which infect Achnatherum inebrians and these strains formed another distinct branch. In addition, analysis of actG phylogeny indicated that four clarify further endophyte strains isolated from S. purpurea were also most closely related to Epichloё chisosa from North American A. eminens and formed another distinct branch. Other endophyte strains isolated were most closely related to Epichloё gansuensis from China (Xinjiang) and formed another distinct branch. Our results suggest that the host-specificity might not occur in endophytes infecting S. purpurea and S. purpurea appears to be infected by various Epichloё species.

Diversity and anti-microbial activity of endophytic actinomycetes isolated from Stellera chamaejasme sampled in Aba, Sichuan

LIAO Min, ZHANG Bo, FAN Zhong-Han, CHEN XIONG Chun-Rui, ZHANG Xiao-Ping

2016, 25(3):  43-51.  DOI: 10.11686/cyxb2015262

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In order to develop new biologically active substances in medicinal plants, an isolation and culture method was employed to investigate the taxonomic diversity and anti-microbial activities of endophytic actinomycetes isolated from Stellera chamaejasme sampled in Aba, Sichuan. It was found that the number of isolates was affected by many factors, especially organic matter content which was significantly positively correlated with the isolate number (P<0.05, r=0.86). Fifty two isolates were obtained on Gauze No.1 growth medium, accounting for 30.4% of total isolations. The numbers of isolates decreased in the following order: root, stem, leaf and flower. Analysis using 16S rDNA-RFLP divided these isolated strains into 11 clusters and further phylogenic analysis classified representative strains as genera Streptomyces, Nocardia, Kitasatospora and Kribbella, respectively, with Streptomyces being predominant. PKS (4) and NRPS (2) genes were detected in the study and most of representative strains had antibiotic activity towards the pathogenic fungal strains, with SCAUEⅢD11-1 being most potent. It is concluded that behavior of isolates of endophytic actinomycetes from S. chamaejasme is affected by many factors with resulting diversity of expression. Functional genes and antibiotic activity indicated endophytic actinomycetes from S. chamaejasme sampled in Aba had potential medicinal value.

The major types and epidemic trends of alfalfa diseases in Northeast and North China

WANG Yu, YUAN Qing-Hua, MIAO Li-Hong, ZHANG Li, PAN Long-Qi

2016, 25(3):  52-59.  DOI: 10.11686/cyxb2015260

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Alfalfa diseases in Northeast China (Heilongjiang and Jilin Provinces) and North China (Hebei Province and the Inner Mongolia Autonomous Region) were investigated in 2013 and 2014. Fourteen alfalfa diseases were found in Northeast China, 12 in Heilongjiang Province and 10 in Jilin Province, and 17 diseases were found in North China, 10 in Hebei Province and 13 in Inner Mongolia. Common leaf spot, spring black stem and leaf spot, stemphylium leaf spot, downy mildew and Fusarium root rot were the five most prevalent diseases that would cause serious plant damage in Northeast China. The occurrence of these diseases peaked in July and August. Major differences existed in the disease varieties found at each investigation site in North China. There were five major diseases (downy mildew, rust, stemphylium leaf spot, spring black stem and leaf spot and Fusarium oxysporum root rot) which would cause serious damage in Inner Mongolia, especially when their occurrence peaked from June to September. Six diseases (common leaf spot, rust, stemphylium leaf spot, spring black stem and leaf spot, Fusarium equisetum root rot and anthracnose) were found in Langfang City and four (downy mildew, common leaf spot, rust and spring black stem and leaf spot) in Zhangjiakou City of Hebei Province. These diseases would cause serious damage, especially when their occurrence peaked from July to October for Langfang City and from June to October for Zhangjiakou City.

Isolation of cellulose-degrading bacteria and determination of their degradation activity

JIA Hui, CHEN Xiu-Rong, LU Guang-Xin, KONG Ya-Li, YANG Cheng-De

2016, 25(3):  60-66.  DOI: 10.11686/cyxb2014172

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Eight bacterial strains were isolated from soil in the east Qilian Mountains. Of these, four strains had a higher capacity for degradation of plant cellulose when cultured on a CMC-Na plate medium. The growth characteristics of the four strains were studied, and the optimum temperature range of the 4 active strains was 25-30℃, the optimum pH for growth was 5-8, and the optimum sodium concentration was 4% to 5%. A strain designated X1-2 possessed the highest cellulose degradation ability. Based on morphology, gram stain reaction, and 16S rRNA phylogenetic comparison, this strain was identified as a member of the genus Bacillus (Bacillus sp.). It is a bacterium with strong plant cellulose degradation ability.

Proteomic analysis of nitrogen stress-responsive proteins in the leaves of tall fescue

LI Xiao-Dong, SHU Jian-Hong, YU Er-Ru, WU Jia-Hai, CAI Yi-Ming, WANG Xiao-Li

2016, 25(3):  67-76.  DOI: 10.11686/cyxb2015470

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In order to thoroughly investigate the protein level changes of tall fescue in low-nitrogen conditions, we analyzed the proteome of the leaves from 30 day old plants exposed to low-nitrogen stress using the iTRAP technique. In total, 595 proteins were differentially accumulated (295 up-regulated and 300 down-regulated), which participated in diverse metabolic pathways. According to a strict selection standard, we discovered that the genes related to redox reactions and stresses significantly increased. Physiological and biochemical analysis revealed that the contents of chlorophyll, soluble proteins and free amino acid dramatically decreased, while reactive oxygen-scavenging enzymes such as POD, SOD and GS were highly active. The expression pattern of affected genes, detected by real-time fluorescence quantitative RT-PCR, coincided with the proteomic data. Notably, most of the 14-3-3 family of proteins were enriched by nitrogen shortage, suggesting that these involve the key genes that take part in diverse stresses in tall fescue. In this study, we provide proteomic information for tall fescue subjected to low-nitrogen availability. We also highlight some of the key genes involved and discuss their potential uses.

The genetic diversity of 9 populations of dry-desert Agropyron mongolicum collected in northern China

LI Xiao-Quan, GAO You-Han, LIU Yang, SUO Pei-Fen, Han Bing

2016, 25(3):  77-85.  DOI: 10.11686/cyxb2015219

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Agropyron mongolicum is one of the dominant species in desert steppe across Eurasia, due primarily to its cold and drought resistance. In this study, we analyzed chromosome polymorphism and DNA polymorphism in 9 populations of A. mongolicum in northern China. The chromosome number of the 9 populations was 7. Cells were diploid and showed no polymorphism in chromosome ploidy. A total of 138 pairs of wheat SSR primers were amplified and analyzed. A total of 21 primer pairs were amplified with specific fragments. The screening rate of SSR primers was 15.2%. A total of 119 specific bands were amplified: specificity was 5.6 and the polymorphism of DNA was rich. POPGEN 32 software was used to calculate the genetic diversity of the 9 populations of A. mongolicum. Population P₈ was found to have the least level of diversity, while P₃ had the highest. AMOVA software was used to analyze genetic differentiation, indicating that genetic differences come mainly from individuals in the populations. The UPGMA method was used for a cluster analysis of the 9 populations. When the genetic similarity coefficient is 0.80, the materials tested divided into three groups: P₁-P₆, P₇-P₈ and P₉. This paper lays the foundation for the development and utilization of new varieties of A. mongolicum.

The phenotypic traits and molecular genetic variation of Bermudagrass (Cynodon dactylon) cultivars and breeding lines

XIE Huan, JIANG Lin-Feng, MA Hong-Ping, ZHANG Xin-Quan, LIU Wei, PENG Yan

2016, 25(3):  86-95.  DOI: 10.11686/cyxb2015228

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Bermudagrass (Cynodon dactylon) is a perennial, warm-season turfgrass well known and widely used for different purposes throughout the world. In order to further clarify the characteristics and genetic basis of C. dactylon germplasm in China, this study performed a comparative study of the phenotypic traits and molecular genetics of 5 cultivars and 1 breeding line, as well as 1 cultivar introduced in China. The green stage and turf speed are 53 and 269 d for the breeding line '02011', higher than the 5 cultivars. The differences between cultivars in terms of plant height, flag leaf, creeping stem, and inflorescence characteristics were highly significant (P<0.01). 8 DUS (distinctness, uniformity and stability) characteristics (including stolon surface color, degrees of heading, color of surface blade, reproductive shoot cyanine glucoside color, growth habit, glume cyanine glucoside color, glume tip cyanine glucoside color) differed among the tested cultivars to varying degrees. 167 and 316 bands were amplified for 18 pairs of primers by SRAP and SSR, of which 87.51% and 70.13% were polymorphic. SRAP and SSR showed that C. dactylon cultivars from the same geographical area could exhibit similar phenotypic traits and relatively close genetic similarities.

Adaptive changes in the young leaf cell ultrastructure of crown buds in Medicago sativa (Leguminosae) during overwintering

FANG Qiang-En, ZHANG Bo, LI Yu-Bo, SHI Shang-Li

2016, 25(3):  96-107.  DOI: 10.11686/cyxb2015443

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In order to explore the cytological mechanism of cold resistance in alfalfa crown buds during winter, a study of ultrastructural changes in young leaf cells of crown buds in the alfalfa variety 'WL168' was conducted by means of TEM. The results showed that: 1) a series of active changes in cell ultrastructure adapted to cold temperature take place during overwintering. The major changes included plasmalemma invaginations, the large central vacuole segmentation into multiple small vacuoles, chromatin condensation, plastid becoming crescent or horseshoe-shaped, starch grains depletion or even disappearance and plasmolysis. The capacity for cold resistance in buds was improved gradually by these adaptive adjustments of cell ultrastructure. 2) Two kinds of crown buds were found in winter: white bud and brown bud. These two kinds have different cellular growth states. The white bud cells had a slow response to cooling before winter and did not fully form specialized structures for winter hardiness until soil freezing, but they regrew quickly after cold resistance release in early spring. The cold resistance development of white buds during overwintering went through 4 phases: enhanced phase (late Oct-mid-Dec), maintenance phase (late Dec-mid-Jan), decline phase (late Jan-late Feb) and termination phase (early Mar-mid-Mar). In comparison, brown bud cells responded earlier to low temperatures before winter but more slowly to the warming of temperatures in spring. By mid-March, the cellular structure of brown buds still maintained their cold tolerance. The coexistence of brown and white buds during winter, whose cell ultrastructure changes asynchronously in response to low temperature, could be an adaptive strategy of alfalfa to cold stress.

Analysis of botanical traits and self-compatibility in winter rapeseed Brassica napus and Brassica rapa and F₁ hybrid populations

ZHAO Yan-Ning, MI Chao, SUN Wan-Cang, LIU Zi-Gang, WU Jun-Yan, FANG Yan, LI Xue-Cai, LIU Hai-Qing, Dong Yun

2016, 25(3):  108-119.  DOI: 10.11686/cyxb2015103

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Changes in cold tolerance, botanical morphology (BM), growth habit (GH) and self-compatibility (SC) of Brassica napus, Brassica rapa and their hybrids were compared. Vision (B. napus), Longyou 9 (B. rapa) and their reciprocal crosses progenies were used in the study. The cold tolerance, BM, GH and SC of the hybrids were evaluated by comparing BM, winter performance, bagging selfing and pollen-stigma interactions with that of the parent lines. The BM and dry matter accumulation of F₁ hybrids (Vision×Longyou 9) was intermediate while GH was similar to B. rapa. Winter survival of F₁ plants in reciprocal crosses were 68.75% and 65.00%. Root length of reciprocal crosses in F₁ plants were 14.83 and 14.30 cm. Crown diameter of F₁ hybrids from reciprocal crosses were 6.08 and 5.67 mm. The SC was highest in Vision and declined in order; F₁ (Vision×Longyou 9), F₁ (Longyou 9×Vision), Longyou 9 with SC indices being 20.83, 1.09, 1.06 and 0.87, respectively. The self-compatibility of parents and F₁ plants was consistent with the level of pollen germination. The cold tolerance of hybrids was stronger than B. napus but weaker than B. rapa. The F₁ hybrids were self-compatible, but the degree of the SC was much less than that of B. napus.

Karyotype study of 8 kinds of Avena nuda

GENG Fan, ZHOU Qing-Ping, LIANG Guo-Ling, JIA Zhi-Feng, LIU Wen-Hui, DING Cheng-Xiang, LIU Yong, YAN Hong-Bo

2016, 25(3):  120-125.  DOI: 10.11686/cyxb2015101

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In order to provide cytological information for the collection, identification, utilization and breeding of Avena nuda germplasm, karyotype analysis and an evolution trend investigation have been undertaken of 8 A. nuda cultivars from different provinces of China using the conventional tableting method. The karyotype formulas of the 8 cultivars as follows: Qingyou No. 3: 2n=6x=42=22m+20sm (4SAT); Pingan: 2n=6x=42=18m+24sm (4SAT); Baiyan No. 2: 2n=6x=42=18m+24sm (2SAT); Huazao No. 2: 2n=6x=42=20m+22sm (2SAT); Huawan No. 6: 2n=6x=42=14m+28sm (6SAT); Jinyan No. 8: 2n=6x=42=22m+20sm (4SAT); Ningyou No. 1: 2n=6x=42=16m+26sm (2SAT); Dingyou No. 6: 2n=6x=42=16m+26sm (4SAT). The karyotype of the 8 cultivars belongs to the 2B type. According to clustering and evolutionary trend analysis, Baiyan No. 2 is a relatively new cultivar and Qingyou No. 3 is the most original cultivar.

Determination of general combining ability and estimation of genetic parameters for yield and quality in alfalfa

WANG Hong, SHI Shang-Li, ZHANG Xu-Ye, ZHANG Li

2016, 25(3):  126-134.  DOI: 10.11686/cyxb2015170

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To breed high yielding high quality alfalfa cultivars, seeds of 16 half-sib lines with good performance, obtained from the progeny of multiple crosses, were selected. General combining ability (GCA) and the broad-sense heritability (H²) for yield and quality were analyzed and evaluated. Cluster analysis was conducted based on GCA. Two genotypes with high GCA (White flower No. 3 and Fast-growing No.4) and eight strains with moderate GCA (Fast-growing No.15, Fast-growing No.12, White flower No.1, White flower No.2 and Fast-growing No.1 etc.). Strains with high yield and quality can be used as parents in the next crossing cycle. The estimated H² values for attributes affecting relatively feeding value were in the order>hay yield>leaf-stem ratio>crude protein>branch number>internode length>plant height>growth rate. Most H² values were >80%, which means they could be used as early generation selection indicators in a breeding programme.

Biomass change, energy distribution and hormone concentrations in Elymus sibiricus reproductive stems during seed development

LIU Jin-Ping, WANG Da-Wei, YOU Ming-Hong, ZHANG Xiao-Jing, CAI Jian, ZENG Xiao-Lin

2016, 25(3):  135-142.  DOI: 10.11686/cyxb2015250

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A three year old stand of Elymus sibiricus, was studied with the aim of determining the change in reproductive stem biomass, water content, biomass and energy distribution among floral components during the seed head development, in order to better understand the energetics of seed head development. During flowering various measurements were made, including photosynthetic rate of reproductive culms, biomass and energy distribution (including proportional allocation to stem, leaf, peduncle, and flower), 1000-seed weight, hormone concentration. Measurements were repeated at stem elongation, anthesis, seed filling, the milk stage, the dough stage and seed maturity. Key results were: 1) The total biomass of reproductive stems significantly increased from anthesis to seed filling to the milk stage (P<0.05). Seed head biomass peaked when plants were in the dough stage. The biomass proportion of vegetative organs gradually decreased with seed head development. Leaf comprised 18.39% of total biomass at anthesis, and that dropped to 9.76% at seed maturity. The proportion of stem biomass reached a maximum at the milk stage, then significantly decreased. The biomass of reproductive organs, especially the flowers, significantly increased from the milk stage to the dough stage. However, the biomass of peduncle was relatively static. 2) The photosynthetic rate of reproductive stems changed little from anthesis to the milk stage, but dropped significantly after the milk stage (P<0.05). The total energy content of reproductive stems reached its maximum at the dough stage, but two peaks were observed; one between anthesis and seed filling, and one from seed filling to the milk stage (P<0.05). Energy distribution differed significantly between seed head components (P<0.01), and ranked in order: panicle>leaf>stem>peduncle. 3) The energy content of stems and leaves declined during seed development. The energy content of leaves showed two obvious troughs, with a minimum of 13.69%, from seed filling stage to the dough stage. The energy content of stems was declined significantly from milk the stage to seed maturity. 4) During seed development, seed fresh weight significantly increased twofold, and seed dry weight significantly increased fivefold (P<0.05). Seed yield (units are needed) significantly increased from the milk stage to the dough stage, then significantly decreased after the dough stage (P<0.05). 5) The gibberellic acid concentration fell by 50.25% from seed filling to seed maturity, while abscisic acid concentration increased by 91.37% from the dough stage to the seed filling stage. Therefore, seed production fields should be managed so as to maintain the integrity and health of leaves until the milk stage of seed development, to provide energy for seed development. Seed should be harvested at the end of the dough stage.

Effect of sowing date and variety on grain-filling in naked oats

LIU Wen-Hui

2016, 25(3):  143-153.  DOI: 10.11686/cyxb2015207

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To understand the grain-filling characteristics of 3 naked oat (Avena nuda) varieties; Qingyin No. 3, Baiyan No. 2, Bayan No. 3 and to provide technical guidelines for seed production of naked oats in the Qinghai-Tibetan Plateau, the effect of sowing date on grain-filling were assessed. Grain-filling in all 3 varieties, irrespective of sowing date, consisted of 3 stages; early, mid and late which fitted a Richards function. Durations of the early, mid and late stages were 16-20 d, 7-9 d and 4-7 d, respectively. Maximum rate of grain-filling observed in the mid stage was 1.54 g/d (1000-seeds), 2.53 times and 3.23 times that of the early and late stages, respectively. During grain-filling dry-matter accumulation (thousand kernel weight, TKW) was initially slow, rapid in the intermediate stage and slow in the late stage. Conversely, moisture content decrease followed the same pattern. Sowing date had no effect on grain-filling in any variety, but did influence TKW. The maximum dry matter accumulation rate from the earliest sowing (April 3^rd) was 2.59 g/(1000-seeds) and 4.05 g/(1000-seeds) higher than those in the later sowing dates, 7 and 14 d, respectively. The TKW accumulation was negatively correlated with the rate of grain-filling and positively correlated with the duration of grain-filling. Baiyan No. 2 had the highest TKW and grain-filling rate (1.22 g/d·1000-seeds). It is implied that the higher TKW of the naked oat varieties in this study was more dependent on higher grain-filling rate, and is less dependent on the duration of grain-filling. The results of the study showed that sowing date significantly affected the accumulation of dry matter; sowing in early April in the Qinghai-Tibetan Plateau resulted in greater accumulation of dry-matter and higher yield of naked oats.

Effects of irrigation frequency and fertilizer rate on alfalfa seed yields in the Yellow River irrigated region

CHEN Dong-Dong, WANG Yan-Rong, HAN Yun-Hua

2016, 25(3):  154-163.  DOI: 10.11686/cyxb2015269

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Given crop demand for water in the Yellow River irrigation region of Gansu province, irrigation needs to be supplied for fixed periods. To explore optimum irrigation strategies and fertilizing methods, the effects of different irrigation frequencies (two, three and four times) and application rates of phosphate diamine (0, 180, 360, 540 kg/ha) on alfalfa seed yield and yield components were studied. The results showed significant differences in seed yield for the different irrigation frequencies (P<0.01). Seed yield decreased with increased irrigation frequency. Irrigating two times was suitable for local alfalfa seed production, with the average yields in 2013 and 2014 being 686 and 891 kg/ha respectively. With increased fertilizer rates, actual seed yield first increased and then decreased, with the highest yields achieved under a fertilizer rate of 360 kg/ha (average yields in 2013 and 2014 were 631 and 786 kg/ha respectively). Irrigation frequency and fertilizer rate interacted in terms of alfalfa seed yield. Under two-times and three-times irrigation, increasing fertilizer rates could improve seed yield significantly. Under four-times irrigation, with increased fertilizer rates the seed yields first increased and then decreased. In 2013, the highest actual seed yields (757.28 kg/ha) were obtained with two-times irrigation and a fertilizer rate of 360 kg/ha. In 2014, the highest actual seed yields (1018.75 kg/ha) were obtained with two-times irrigation and a fertilizer rate of 540 kg/ha. Alfalfa seed yield had significant correlations with effective fertile tiller number (R²=0.503) and inflorescence number (R²=0.835). In summary, two-times irrigation and a fertilizer rate of 360 kg/ha are recommended for local alfalfa seed production.

Effects of alternate furrow irrigation on the biomass allocation and water use efficiency of alfalfa

ZHANG Jing, WANG Qian, XIAO Yu, PANG Xiao-Pan, JIA Ting-Ting, SONG Rui, LIU Hui-Xia

2016, 25(3):  164-171.  DOI: 10.11686/cyxb2015232

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Alternate furrow irrigation has been widely applied to crop production in order to optimize the harvesting of seeds and fruits. A field experiment was conducted to determine the effects of alternate furrow irrigation on alfalfa above-ground yield and its components, root biomass, root to shoot ratio and water use efficiency. The experiment aimed to establish whether alternate furrow irrigation can apply to alfalfa whose harvest target is vegetative mass. The results showed that alternate furrow irrigation significantly improved the water use efficiency of alfalfa. Moreover, there was no significant effect on above-ground biomass because branches per plant increased while leaf numbers per plant decreased. Alternate furrow irrigation increased root biomass at 0-20 cm and 0-60 cm soil levels, but decreased root biomass at 20-60 cm. Alternate furrow irrigation also increased root to shoot ratio, therefore improving alfalfa's drought resistance under water stress. These results prove that alternate furrow irrigation not only improves water use efficiency but also maintains the yields of alfalfa. It does so by improving plant drought resistance by encouraging root system development and increasing the number of branches per plant. The results thus indicate that alternate furrow irrigation can be applied to the management of alfalfa production.

Effect of partial shading on the morphological plasticity and biomass allocation of Potentilla anserina

FAN Xing, CAI Jian, LIU Jin-Ping, LI Ying, ZHANG Xiao-Jing, ZENG Xiao-Lin

2016, 25(3):  172-180.  DOI: 10.11686/cyxb2015208

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In this study, genet, mother ramet and some clonal fragments of Potentilla anserina were used to analyze the effect of partial shading. The quantitative traits and biomass allocation of root, stem and leaf were also measured. The purpose of the study was to analyze the effect of partial shading on the morphological plasticity and biomass allocation of the mother ramet, daughter ramet and genet of P. anserina. The results showed that: 1) For mother ramets, partial shading displayed a significant effect on plant height, leaf length, leaf width, leaf area and root depth (P<0.05). Partial shading increased plant height, leaf length and total leaf area, but different shading positions or shading intensities had different effects on leaf width, single leaf area and root length. 2) For daughter ramets, partial shading had a significant impact on leaf length and leaf area. Shading of the clonal fragment was the main factor affecting leaf size of daughter ramets, with shading of mother ramets second placed. 3) Partial shading significantly increased the number of cloned fragment daughter ramets and new daughter ramets, and also increased the cloned fragment number of genets (P<0.05). Shading mother ramets had an important influence on stolon elongation and the formation of new cloned fragments. 4) Partial shading displayed a highly significant effect on the root, stem and leaf water content of genets, as well as on their leaf and root biomass accumulation (P<0.01). With shading of more than 2 clonal fragments or mother ramets, the root biomass accumulation of genets significantly increased, but with full shading of genets the root biomass was clearly lower than the control. 5) Partial shading also had significant effects on the allocation ratio of stem, leaf and root biomass of genets (P<0.01). Shading had the greatest effect on leaf allocation ratio and a lower effect on stem allocation ratio, but the lowest effect was on the root allocation ratio. 6) Partial shading had a significant effect on the underground biomass ratio (P<0.01). Shading had an important effect on the root/stem and stem/leaf ratios (P<0.01), which increased remarkably with full shading. In summary, partial shading displayed a direct influence on the morphological plasticity and biomass allocation of various types of P. anserina plants, including mother ramets, daughter ramets, clonal fragments and genets.

Effect of nitrogen application on intercropping advantages and crop interactions under an oil flax and soybean intercrop system

YANG Ping, LI Jie, ZHANG Zhong-Kai, CUI Zheng-Jun, YANG Tian-Qing, NIU Jun-Yi

2016, 25(3):  181-190.  DOI: 10.11686/cyxb2015235

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Nitrogen is one of the greatest nutritional resources in agriculture, affecting the yield advantage of many intercrop systems. However, it is unclear how nitrogen application affects oil flax and soybean intercrop systems in northern dry farming land. A field experiment was conducted to explore productivity, interaction and yield under intercropping supplemented with different nitrogen rates (0, 75 and 150 kg N/ha). Oil flax/soybean intercropping systems exhibited interspecific advantages. The land equivalent ratio (LER) based on biomass and yield were greater than 1. With increased nitrogen application, the LER initially increased before peaking at 75 kg N/ha, 1.25 and 1.30 respectively for biomass and yield, and subsequently declining. The interspecific competition ability of oil flax was better than soybean under 0 and 75 kg N/ha, and weaker under 150 kg N/ha. The yield and biomass of oil flax/soybean intercrop systems were maximized at 75 kg N/ha, achieving 2440.5 and 7594.3 kg/ha respectively.

Preliminary evaluation of adaptability of 13 Quinoa varieties in the Linxia Arid region of Gansu Province, China

HUANG Jie, YANG Fa-Rong, LI Min-Quan, WEI Yu-Ming, GU Xian, QI Yong-Hong

2016, 25(3):  191-201.  DOI: 10.11686/cyxb2015423

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In order to study adaptive performance of quinoa varieties in the Linxia arid region of Gansu province, we tested 13 different quinoa varieties (designated CK, Q₁ to Q₁₂), to determine seedling emergence rate, phenology, botanical characters, yield, quality and disease resistance. Cluster analysis was applied to evaluate the relationships among selected traits. It was found that all 13 quinoa varieties are able to reach maturity in the test region. There were significant differences among varieties for plant height, branching index, effective branching rate, inflorescence spike length, inflorescence spike diameter, thousand kernel weight, and crude protein and crude fiber content. In addition, cluster analysis revealed Q₇ and Q₈ are dwarf early varieties, while varieties Q₁, Q₇, Q₈, Q₉, Q₁₀ show disease resistance. Q₉ is high yielding (4247 kg/ha, 1252 kg/ha higher than control). There were no phenology characters of obvious relevance to variety choice. Considering all factors measured, Q₉ had the best all round performance and could potentially be planted more widely as a crop in the Linxia arid region of Gansu province.

Analysis of soil and plant nutrients in alfalfa fields in China

XIE Kai-Yun, HE Feng, LI Xiang-Lin, HAN Dong-Mei, WAN Li-Qiang

2016, 25(3):  202-214.  DOI: 10.11686/cyxb2015206

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A scientific approach to fertilizer management is important to ensure optimal plant growth, high fertilizer use efficiency and to resolve the contradictions surrounding production and environmental issues. In order to understand fertilizer management in alfalfa production, a survey was conducted to investigate alfalfa yield at first cut, as well as soil nutrients and plant nutrient content in 49 alfalfa fields in northern China over two years (2012 and 2013). Simultaneously, a survey (questionnaire) was conducted to determine how alfalfa growers (including farmers and corporate growers) managed fertilizer application. Alfalfa was mostly planted in relatively barren sandy soils. Among 49 fields, 35 fields were sandy soil (71.4%), mainly in Inner Mongolia, Gansu and Xinjiang. Soil available nitrogen (N) was high in most fields and deficient in only 10% of fields, mainly due to extremely low organic matter content. Available phosphorus (P) was low in 24.5% of fields and very low in 10.2% of fields. Available potassium (K) was low in 10.2% of fields. Calcium and magnesium were plentiful in all soils. Analysis of micronutrients revealed that 32.2% fields had low available iron (mainly Gansu and Inner Mongolia); 7.1% of fields low available manganese (Gansu and Inner Mongolia); 14.3% of fields had low available copper (1 field Gansu, 3 Inner Mongolia); 50% of fields had low available zinc; 10.7% of fields had low available molybdenum (Mo) (mainly Inner Mongolia); conversely all fields were high in available boron. The alfalfa stands generally had good N nutrition but were low P and K. Among 49 fields 49% of fields had low Mo. Correlation analysis showed that soil total and available P were significantly positively correlated (P<0.05) with alfalfa dry matter yield, suggesting that P fertilizer would significantly increase alfalfa yield. Growers of 18 fields, mostly farmers, didn't apply any fertilizer. 57.1% of growers applied N to increase yields, mostly corporate growers. Phosphate was applied to 41% of fields K to 26.5%. Organic fertilizer was only applied in 8 fields. Micronutrients were not applied to any crops. It was concluded that application of N to alfalfa was relatively common, contradicting the ability of the crop to biologically fix N. Soil P and K levels in soils were low, especially K in China, suggesting that many alfalfa crops would benefit from application of these nutrients. Molybdenum may be limiting in some alfalfa crops.

Green manure returning effect of Amaranthus hypochondriacus harvested at different times on soil fertility

CHEN Guo-Jun, YAN Hui-Feng, WU Kai, YANG Ju-Tian, TIAN Lei, TAN Xiao-Lei, ZONG Hao, CHEN Xiu-Zhai, ZHANG Yong-Chun, SUN Yan-Guo, LIU Hai-Wei, SHI Yi

2016, 25(3):  215-224.  DOI: 10.11686/cyxb2015415

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In order to study the returning effect of Amaranthus hypochondriacus on soil fertility, an incubation experiment was carried out to simulate the returning of A. hypochondriacus as green manure to the field. The dynamic change in concentrations of DOC (soil dissolved organic carbon), Nmin (mineral nitrogen), available potassium and slowly released potassium was measured in the soil with plants harvested on 45, 55 and 65 d after growth. During the first 14 d of incubation, the concentrations of soil DOC, Nmin, available potassium and slowly released potassium increased significantly compared to the control. Apparent nitrogen release rate in A. hypochondriacus was more than 19.5%, and for potassium, it was above 63.4%. During 14-56 d of incubation, soil Nmin, available potassium, slowly released potassium concentrations showed the order as sample harvested on 45 d after growth>55 d>65 d>Control, but there were no differences in soil NH₄⁺-N and DOC concentration between the treatments and control (for NH₄⁺-N, sample harvested on 45 d as an exception). After 56 d of incubation, Nmin concentration in the soil was 3.4 times of that under Control, available potassium concentration was at least 3.1 times and slowly released potassium concentration was at least 1.1 times under all treatments with A. hypochondriacus. In addition, the treatments using A. hypochondriacus harvested on 45 d resulted in lower apparent release rates of nitrogen and potassium than the other two treatments using A. hypochondriacus during the incubation. Conclusively, returning A. hypochondriacus to soils obviously improved soil available nutrients, and the plants harvested on 45 d showed better effect on soil fertility.

The effects of corn and green manure intercropping on soil nutrient availability and plant nutrient uptake

DU Qing-Feng, WANG Dang-Jun, YU Xiang-Yu, YAO Lu-Hua, HE Yu-Ji, WANG Rui, MA Sheng-Lan, GUO Yan-Jun

2016, 25(3):  225-233.  DOI: 10.11686/cyxb2015483

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Intensive cropping and a high multiple cropping index have been shown to be important for food security in China. However, inappropriate cropping systems decreases soil quality and causes environmental problems. In this study, three legume green manures, Crotalaria junceal, Phaseolus calcaltus and Sesbania cannabina were intercropped with summer corn in a winter canola production area in Chongqing, southwestern China. Soil nutrient availability, plant nutrient content, and aboveground biomass yields were assessed. Corn yield increased 35% when intercropped with C. junceal, reduced by 21% when intercropped with S. cannabina, and was not affected by P. calcaltus. No differences in plant nitrogen and phosphorus were detected apart from S. cannabina which had higher nitrogen when intercropped. Potassium contents were higher under monoculture compared with intercropping for all three intercrop species. Compared with monoculture corn, nitrogen, phosphorus and potassium increased in corn intercropped with green manures. Soil NO₃ nitrogen, available phosphorus and available potassium under intercropped corn were all higher than under monoculture corn. Correlation analysis indicated that nitrogen content was positively correlated with soil NO₃ levels. Among the three legume green crops, S. cannabina had the lowest plant nitrogen content and aboveground yield which negatively influenced corn yield; P. calcaltus had higher aboveground yield and had no effect on corn yield, however its long vines hindered the corn harvest. However, C. junceal had high nitrogen content and high yield, and increased corn yield suggesting that C. junceal might be a suitable legume green manure crop with summer corn.

The biological characteristics of Digitaria sanguinalis pathogen Fusarium chlamydosporum strain ZC201301

LI Jian, LI Yan, GAO Xing-Xiang, FANG Feng, LI Mei

2016, 25(3):  234-239.  DOI: 10.11686/cyxb2015374

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Fusarium chlamydosporum strain ZC201301 showed high herbicidal activity towards Digitaria sanguinalis. In the present study, the 'single factor at a time' method was used to determine biological characteristics of ZC201301. It was found that the optimal mycelial growth media were potato dextrose agar (PDA) and crabgrass leaf juice (CAJ), and the optimal temperature for mycelia growth ranged from 25 to 30℃. The optimal initial pH for culture media was 6-8. Strain ZC201301 can sporulate in a variety of media, but the optimal sporulation medium was CAJ. Mycelial growth did not differ significantly in fluorescent light from that in the dark, but darkness was beneficial for sporulation. The optimal carbon sources for mycelium growth was glucose, and the best nitrogen source was NH₄NO₃. Oxygen is essential for mycelial growth, and mycelial growth was inhibited when the liquid/gas ratio was less than 1:1. The herbicidal activity of strain ZC201301 was sensitive to relative humidity, and was significantly decreased when humidity was less than 60%. These results indicate the strain ZC201301 is amenable to propagation, which is important for the preparation of bio-control agents and for their survival under field conditions.

Effect of chicken manure application on SPAD value, hay yield and protein content of Lolium multiflorum cv. Tetragold

WANG Wen-Shi, TIAN Yu, LOU Yu-Jie

2016, 25(3):  240-244.  DOI: 10.11686/cyxb2015267

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The effect of chicken manure application on the chlorophyll content (SPAD value), hay yield and crude protein content of Lolium multiflorum cv. Tetragold were evaluated through a field trail. The experiment included 3 treatments with different nitrogen levels (0, 130.77 and 261.54 kg N/ha) with 3 replicates. The SPAD value was determined by using a Chlorophyll meter at different growth stages. Hay yield and crude protein content were determined simultaneously. Correlation between SPAD value and the other indexes at different growth stages were also calculated. Chicken manure application significantly improved SPAD value at the booting and flowering stages, hay yield at the flowering and maturing stages and crude protein content at flowering. There were significant positive correlations between SPAD value and hay yield, and crude protein content at all four stages.

Decomposition characteristics of a Vulpia myuros cover crop in an orchard soil and its effect on N supply

LIANG Bin, DONG Jing, SUI Fang-Gong, LIU Qing-Hua, LI Jun-Liang

2016, 25(3):  245-250.  DOI: 10.11686/cyxb2015201

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Cover cropping in orchard is an efficient soil management technique for improving soil fertility and reducing soil erosion. However, the effect of cover crops on nutrient supply is not well understood and a concern for growers. An experiment was conducted to investigate the decomposition characteristics of a cover crop (Vulpia myuros) and its effect on N supply in orchard soil. The decomposable organic C in straw of V. myuros accounted for 51% of organic C; the remainder increased soil C sequestration by 1 t/ha per year. Application of exogenous N fertilizer had no effect on annual net C sequestration, although it increased the decomposition rate of V. myuros straw. During decomposition, immobilized N ranged from 39-65 mg/kg. Consequently an additional 60-100 kg N/ha should be applied during V. myuros decomposition in low fertility soils in the first few years to avoid competition between soil microbes and crop trees, and to improve soil fertility.

Effects of nitrogen and water addition on herbage N and P concentrations of Stipa breviflora in a desert steppe grassland

BAI Chun-Li, LIU Yong-Zhi, WANG Ming-Jiu, SHAN Yu-Mei, Hasihu

2016, 25(3):  251-256.  DOI: 10.11686/cyxb2015391

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Knowledge of herbage nitrogen (N) and phosphorus (P) in plants is fundamental to the study of absorption and utilization of nutrients by the plants. In order to better understand limiting factors and plant adaption strategies to environmental factors in the grassland ecosystem, water and N enhancement experiments were carried out in a Stipa breviflora steppe. Four treatments were set up: nitrogen addition (ND), water addition (WD), nitrogen and water addition (NWD) and control (CK) with five replicates in a free grazed paddock in a S. breviflora desert steppe, Inner Mongolia. The S. breviflora leaf N and P concentrations and their stoichiometry under different treatments were analyzed. It was found that S. breviflora enhanced adaptability to barren habitats by increasing leaf N content. Uptake of N by S. breviflora was limited by low soil N and water contents. The absolute leaf N and P contents and the N:P ratio were more sensitive to the environmental addition of N and water in mid season than in late season. The availability of environmental N greatly influenced the leaf N and P contents and N:P ratio in mid season and the N:P ratio in late season when plants were withering. However, the availability of water only affected the leaf N and P content in mid season and not in late season.