Table of Content

12 November 2014, Volume 40 Issue 11

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Construction of Sugarcane Hybrids Core Collection by Using Stepwise Clustering Sampling Approach with Molecular Marker Data

LIU Xin-Long,LIU Hong-Bo,MA Li,LI Xu-Juan,XU Chao-Hua,SU Huo-Sheng,YING Xiong-Mei,CAI Qing,FAN Yuan-Hong

Acta Agron Sin. 2014, 40(11):  1885-1894.  doi:10.3724/SP.J.1006.2014.01885

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Sugarcane hybrids are important breeding parent sources of commercial varieties. To use efficiently and evaluate the sugarcane hybrids conserved in National Nursery of Sugarcane Germplasm Resources (NNSGR), we selected a total of 161 accessions of sugarcane hybrids including 136 accessions from the pre-core collection of sugarcane hybrids constructed previously and 25 accessions introduced recently for constructing a core collection. Using stepwise UPGMA clustering sampling approach with three kinds of genetic similarity coefficient calculated according to SSR molecular data, these accessions were further screened to form a core collection with random sampling strategy as control. We tested the quality of core collections using nine indices, including Nei’s diversity index, Shannon-Wiener diversity index, total band number, polymorphic band number, percentage of polymorphic bands (PPB), variable rate of coefficient of variation (VR), coincidence rate of range (CR), variance difference percentage (VD) and mean difference percentage (MD). The results showed that 161 sugarcane hybrids possessed abundant genetic diversity at 20 SSR loci, which amplified 294 bands with 290 polymorphic bands taking up a mean of 98.64% of total bands. According to three kinds of genetic similarity coefficient (Jaccard, SM, and Dice) and two sampling strategies, ultimately eight core collections were gained. In the quality evaluating of core collections, three indices including Shannon-Wiener diversity index, total band number and polymorphic band number, performed high identifying efficiency, but the rest presented low efficiency. The core collection constructed on the basis of Jaccard or Dice genetic similarity coefficient was higher in quality than others, which consisted of 107 sugarcane hybrids with 0.9785 in Nei’s diversity index and 4.1854 in Shannon-Wiener diversity index, and did not have significant difference in molecular diversity with total resource at P < 0.05, moreover, MD = 0.00% (< 20.00%) and CR = 94.32% ( > 80.00%). All the mentioned above indicated the core collection can represent completely the diversity level of total resource in agronomic traits and molecular markers, and will can provide crucial basis for evaluating and utilizing sugarcane hybrids, and mining elite genes.

Effect of Different Recurrent Selection Methods on a Narrow Base Maize Population

LI Lu-Jiang,LAN Hai,PAN Guang-Tang,YANG Ke-Cheng

Acta Agron Sin. 2014, 40(11):  1895-1904.  doi:10.3724/SP.J.1006.2014.01895

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The narrow basis of maize germplasm is the main factor blocked the development of maize breeding in China. The population improvement via recurrent selection is one of effective methods for the improvement and expansion of maize germplasm. In this study, three kinds of recurrent selection methods were carried out to improve the narrow base maize population P4C0: a) five cycles of biparental mass selection (MS); b) one cycle of half-sib and S2:3 family combining selection (HS-S2:3) followed by three cycles of MS; and c) one cycle of open improvement (OI) by crossing two inbred lines to the population. In different ecological environments, the phenotypes of the developed populations were analyzed and the combining abilities were tested according to an incomplete diallel model to study the effects of the different methods. The effects of the different methods on genetic diversity of the populations were also analyzed by using 51 pairs of SSR markers. It was found that the effects of different methods on the main traits, general combing ability (GCA) and the genetic diversity were different. The effects of MS on yield, yield components and their GCAs were greater than these of HS-S2:3. In addition, MS was more effective on maintaining the genetic diversity of the population. The HS-S2:3 were more beneficial to maintain plant height and ear height of the population. The OI was more effective on the improvement of yield, yield components and their GCAs than MS. Genetic diversity was maintained in the first two cycles of MS on P4C0 then decreased slightly from the 3rd cycle. Genetic diversity decreased after one cycle of HS-S2:3 and increased after 3 cycles of MS or 1 cycle of OI.

Functional Analysis of Photo-Oxidative Stress Responsive Genes in Wheat Using Virus-Induced Gene Silencing System

CHEN Kun-Mei,LI Hong-Wei,LIN Fan-Yun,CHEN Yao-Feng,LI Bin,ZHENG Qi,LI Zhen-Sheng

Acta Agron Sin. 2014, 40(11):  1905-1913.  doi:10.3724/SP.J.1006.2014.01905

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Functional analysis of photo-oxidative stress responsive genes in wheat (Triticum aestivum L.) may benefit wheat improvement for high radiation use efficiency. A Chinese variety Xiaoyan 54 developed from distant hybridization between common wheat (T. aestivum, 2n=42) and tall wheatgrass (Thinopyrum ponticum, 2n=70) shows significant tolerance to high light induced photo-oxidative stress. Based on previous transcriptome analysis of Xiaoyan 54 in response to high light stress, six genes were selected in this study to assess their possible roles in photo-oxidative stress response using barley stripe mosaic virus (BSMV) mediated virus-induced gene silencing (VIGS) system in Xiaoyan 54. The BSMV induced silencing of the targeted genes together with the BSMV:GFP control plants were exposed to low temperature and high lightII (F_v/F_m), the photosynthetic performance index (P.I.), malondialdehyde (MDA) content, and biomass were evaluated. The results showed that Ta23008 and Ta92165 were involved in the responses of wheat to LTHL, DCMU, MV, and H₂O₂, respectively. Ta106078 was responsible for wheat tolerance to DCMU, MV, and H₂O₂ while Ta27787 was responsible for LTHL, DCMU, and H₂O₂ stress. Ta24695 participated in the response of wheat to both LTHL and H₂O₂. However, Ta119251 seemed to be only responsible for the DCMU stress in wheat. Additionally, four genes, Ta23008, Ta92165, Ta106078 and Ta119251, were likely to regulate biomass accumulation because the biomass was significantly reduced when they were silenced in wheat. These results provided new hints toward understanding the molecular mechanism of tolerance to photo-oxidative stress in Xiaoyan 54.(LTHL), N-(3,4-dichlorophenyl)- N’,N’-dimethylurea(DCMU), methylviologen (MV), and hydrogen peroxide (H₂O₂) stress, respectively. The maximum photochemical efficiency of photosystem

SNP Detection and Analysis of Genes for Flavonoid Pathway in Yellow- and Black-Seeded Brassica napus L.

QU Cun-Min,LU Kun,LIU Shui-Yan,BU Hai-Dong,FU Fu-You,WANG Rui,XU Xin-Fu,LI Jia-Na

Acta Agron Sin. 2014, 40(11):  1914-1924.  doi:10.3724/SP.J.1006.2014.01914

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Flavonoids as the secondary metabolites play a crucial role in colour changing process of flower, leaf, fruit and seed. In this research, primers for amplifying full-length ORF sequences of the genes involved in the favonoid biosynthesis pathways were designed according to conserved nucleotide regions from the public databases. Using the homology-based cloning strategy, 41 gene copies were obtained from 13 genes using 17 pairs of specific primers in different yellow- and black-seeded seed coats of B. napus. Each of full-length ORF sequences was sequenced and analyzed in the levels of both nucleic acid and protein. The results showed that the SNPs in four flavonoid pathway genes (BnTT3, BnTT18, BnTTG1,and BnTTG2), ranged from 16 to 52, but there were olny 2 to 16 amino acid mutations detected in the protein level, indicating that the mutation of SNPs may not be involved in the mutation of amino acid. In addition, continuous bases deletion existed in different positions of sequence of BnTTG2 (119 to 121 bp, 183 to 189 bp and 325 to 330 bp), and two consistent amino acid mutation sites were detected in BnTT3 and BnTT18 among different materials, inferring that BnTT3 and BnTT18 may play an important role in difference of seed coat colour formation in yellow- and black-seeded B. napus. Therefore, these genes involved in flavonoid pathway could be distinguished by the allelic-specific PCR in yellow- and black-seeded B. napus. These results could help to develop specific seed coat gene chips and elucidate the genes and their action sites for the seed coat colour in B. napus

cDNA Cloning and Expression of Two Cellulose Synthase Genes from Boehmeria nivea

LIU Yu-Xiang,CHEN Jiang-Rong,PENG Yan,HUANG Yu,ZHAO Yan,HUANG Li-Hua,GUO Qing-Quan,ZHANG Xue-Wen

Acta Agron Sin. 2014, 40(11):  1925-1935.  doi:10.3724/SP.J.1006.2014.01925

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 Two potentially high homologous fragments CL789 and Unigene20360 were identified as plant cellulose synthase character sequence from the transcriptome data we obtained previously by Blast aligning and homologous screening. The two pairs of specific primers were then designed based on the CL789 and Unigene 20360 sequences information. The intermediate fragments of two cellulose synthase gene cDNA were cloned from ramie variety Xiangzu 3 by RT-PCR. And the whole cDNA was cloned by followed 5' and 3' RACE. The full length cDNAs were sequenced and their encoded putative proteins were identified as cellulose synthase by the conserved domain analysis. These two cDNA sequences were named as BnCesA2 and BnCesA3 respectively. The full-length coding sequence of BnCesA2 gene is 3240 bp, and encodes a putative 1079 amino acids. The coding sequence of BnCesA3 gene is 3120 bp, and could be translated into a 1039 amino acids protein. We designed the specific primers based on cDNA sequences of the two genes and their expression levels were tested by quantitative real-time PCR (qRT-PCR), indicating that BnCesA2 and BnCesA3 were both actively expressed in phloem and xylem in the four different cultivars of ramie. But the level of expression showed significant difference that the BnCesA2 expressionwas 2 to 5 multiples higher than BnCesA3 in both phloem and xylem. It is speculated that both the BnCesA2 and BnCesA3 participate the primary and secondary cell wall biosynthesis.

Identification of Ideal Test Environments for Multiple Traits Selection in Cotton Regional Trials

XU Nai-Yin,LI Jian

Acta Agron Sin. 2014, 40(11):  1936-1945.  doi:10.3724/SP.J.1006.2014.01936

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Crop breeding needs an integrating selection for the desirable traits. Screening locations with high discriminating ability and typical environments in light of cultivar selection index established by target traits and weights facilitates improving breeding efficiency and saving cost. Cultivar selection index was constructed on the basis of the National Register Criteria for Cotton Variety, namely, SI=0.40´lint cotton yield+0.13´fiber strength+0.09´(fiber length+micronaire value)+0.11´Fusarium wilt+0.09´Verticillium wilt+0.10´harvesting ratio of seed cotton before frost. GGE biplot method was adopted to evaluate the identification, representativeness, and ideal index of cultivar selection index by using 15 locations data from 39 sets of national cotton variety regional trials including 585 trials in the Yangtze River Valley (YaRV) during 2000–2013. The results showed that Huanggang in Hubei Province and Nanjing in Jinagsu province were evaluated as the most desirable trial locations; Jingzhou and Wuhan in Hubei Province and Yancheng in Jiangsu Province were desirable trial locations; while Nanyang in Henan Province, Xiangyang in Hubei Province, Changde in Hunan Province, Janyang and Shehong in Sichuan Province were considered as undesirable locations for cotton cultivar selection. The ideal environments were all located in the Middle and Lower Reaches of YaRV, while the undesirable locations included Jianyang and Shehong in the Sichuan basin in the upper reaches of YaRV, and Nanyang and Xiangyang in Nan-Xiang basin at the northern border of YaRV. Changde in Hunan Province was also considered as undesirable location although it is located in the Middle Reaches of YaRV, probably because of the significantly low plant density used in the farming. In conclusion, this study has established a feasible selection index according to the national cotton registration criteria, and identified desirable test locations for reliable and effective variety evaluation in the area of YaRV. This study sets an example of test location evaluation utilizing historical data for the similar studies in other regions and for other crops.

Physiological Characteristics and Gene Mapping of a Leaf Early-Senescence Mutant osled in Rice

ZHAO Chen-Chen,HUANG Fu-Deng,GONG Pan,YANG Xi,CHENG Fang-Min,PAN Gang

Acta Agron Sin. 2014, 40(11):  1946-1955.  doi:10.3724/SP.J.1006.2014.01946

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Leaf early senescence directly affects crop yield and quality, therefore, studying the molecular and physiological mechanism of leaf early senescence means a lot to crop genetic improvement. This work used ⁶⁰Co γ-radiation to radiate rice Varity 93-11 and a leaf early senescence mutant osled was obtained. The mutant senesced quite early even at tillering stage, showing grey at the tip and edge of leaves and red-brown lesion. Under the treatment of simulative drought stress, the mutant senesced at early seedlings and its plant height and root length were obviously shortened. Analysis in physiology and biochemistry showed the content of malondialdehyde (MDA), activities of superoxide dismutase (SOD) and peroxidase (POD) were basically unchanged from flag leaf to third-top leaf in wild type, while significantly increased, and dramatically higher in the second-top and third-top leaves of mutant. Contents of soluble protein and chlorophyll, and catalase (CAT) activity all gradually reduced in top three leaves of both the mutant and wild type, however, contents in second-top and third-top leaves of the mutant were quite lower than these in wild type. Histochemical stainings of trypan blue, 3,3’-diaminobenzidine (DAB), and nitro blue tetrazolium (NBT) not only suggested the destructions of membrane system but also illustrated the accumulation of H₂O₂ and O₂^?  in the mutant. Besides, ultrastructure of mesophyll cells further explained the degradation of chloroplast in osled. Genetic analysis suggested the osled was controlled by a single recessive gene. Through using gene mapping technologies, the OsLED gene was successfully mapped into an interval from marker RM15528 to marker RM15553 at the long arm of chromosome 3.Genetic distances were both 0.7 cM. These results laid a foundation for later gene cloning and its functions study.

Resistance to Heterodera filipjevi in Triticum aestivum?Aegilops geniculata Germplasm

XING Xiao-Ping,YANG Jing,YUAN Hong-Xia,ZHANG Jia-Jia,LI Hong-Lian*,LIU Wen-Xuan*

Acta Agron Sin. 2014, 40(11):  1956-1963.  doi:10.3724/SP.J.1006.2014.01956

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Heterodera filipjevi is a pathogenic nematode of wheat newly discovered in Huang-Huai Plain of China. However, germplasm resistant to H. filipjevi has been rarely found in genus Triticum. To mine resistance genes from wheat relative species, we identified the resistance to H. filipjevi in 34 accessions of Aegilops geniculata by inoculating H. filipjevi Xuchang population with mean of female number per plant method and relative resistance index method in greenhouse. Six candidates of germplasm were identified including PI542187 with high resistance and other five accessions (PI564186, PI573396, PI374365, PI361880, and PI374365) with resistance. A set of Chinese Spring (CS)?Ae. geniculata addition lines were used to chromosomally locate the resistance gene(s). Lines 7U^g and 5M^g showed obviously fewer females per plant than CS. In two consecutive years, 17 CS?Ae.geniculata 5Mg-5D translocation lines were further tested for resistance against H. filipjevi. Lines 5M^g464, 5M^g466, and 5Mg457 exhibited resistance to H. filipjevi.

Inheritance of Major Gene Plus Polygene of Water-logging Tolerance in Brassica napus L.

JIN Yan,Lü Yan-Yan,FU San-Xiong,QI Cun-Kou

Acta Agron Sin. 2014, 40(11):  1964-1972.  doi:10.3724/SP.J.1006.2014.01964

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The middle and lower reaches of Yangtze River is a main producing region of canola (Brassica napus L.) in China. However, canola in this region is subjected to water-logging during planting period to reduce yield. It is of importance to study the inheritance of water-logging tolerance for canola. In this paper a family lines population of six generations of P₁, F₁, P₂, B_1:2, B_2:2, F_2:3 derived from the cross of WR-4 (resistant)×WR-5 (non-resistant) was used to analyse genetic segregation by applying major gene plus polygene mixed inheritance model. The seedling mortality was recorded on the 7th day after logging-removing for plant recovery following six days full-submergence treatment of the seedlings in 2012 and 2013. The results showed that the seedling mortality was respectively fitted the genetic model of E-0 and B-3 i.e. two pairs of additive- dominant-epistatic major gene plus additive-dominant-epistatic polygene model and two pairs of additive major genes model. This result confirms that water-logging tolerance of seedling in this cross is controlled mainly by two major genes which expressed in the mode of additive-dominant-epistatic effects. While dominant effects expressed (2012) it gave a higher value of |h_a|=0.3475, |h_b|=0.0069 than the additive effect of the major genes which was |d_a|=|d_b|=0.0036. In the populations of B_1:2, B_2:2, and F_2:3, h²_mg was 36.25%, 61.40%, and 61.84% respectively with an average of 53.16% in 2012, and 8.30%, 30.48%, and 43.13% respectively with an average of 27.30% in 2013. Variance from environment effects was 59.77% of the total phenotypic variance on an average in two years. A conclusion could be made that water-logging tolerance of seedling in B. napus is controlled by two major genes but heavily affected by environment. Since a higher value of h²_mg was detected in F_2:3 populations, selection in early generations might be an effective way for waterlogging tolerance breeding in B. napus.

Transformation of BADH Gene into Maize and Salt Tolerence of Transgenic Plant

WANG Xiao-Li,DU Jian-Zhong,HAO Yao-Shan,ZHANG Li-Jun,ZHAO Xin-Mei,WANG Yi-Xue,SUN Yi

Acta Agron Sin. 2014, 40(11):  1973-1979.  doi:10.3724/SP.J.1006.2014.01973

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In order to obtain transgenic maize plants tolerant to salt stress, maize inbred Zheng 58 was transformed with BADH gene by pollen-mediated method. The results of Km-resistant screening, PCR detection and Southern blot analysis proved that BADH gene was introduced into maize plants and integrated into the maize genome. Effects of various concentrations of NaCl solution on growth of T₂ transgenic and non-transgenic maize plants were investigated．The results indicated that transgenic maize seedlings had an improved resistance to salt, and their growth performance was superior to that of non-transgenic maize seedlings. On the basis of the growth status of non-transgenic plants, 250 mmol L^-1 of NaCl solution was used to screen transgenic plants. An analysis on morphological and physiological indexes under the stress of 250 mmol L^-1 NaCl showed that compared with non-transgenic plants, the seedling height of transgenic plants was increased by 10.94%–25.7%, fresh weight was increased by 8.62%–18.2%, dry weight was increased by 9%–18.18%, relative conductivity was decreased by 37.21%–58.14%, chlorophyll content was increased by 15.89%–90.65%, superoxide dismutase (SOD) activity was increased by 64.92%–148.29%, and MDA content was decreased by 26.97%–48.05%. In conclusion, introducing betaine aldehyde dehydrogenase (BADH) gene enhances salt tolerance in maize plants. The first report on introducing BADH gene into the elite maize inbred proved that pollen-mediated transformation approach is an economical, effective and practical plant transformation method without genotype dependence.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Water Utilization and Matter Production in Winter Wheat under Soil-Coated Ultrathin Plastic-Film Mulching and Irrigation Management 

HE Li-Qian,ZHANG Wei-Hong,ZHANG Yong-Sheng,CAO Cai-Yun,LI Ke-Jiang,DU Xiong

Acta Agron Sin. 2014, 40(11):  1980-1989.  doi:10.3724/SP.J.1006.2014.01980

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Serious deficiency of water resource is one of the biggest problems in winter wheat production in North China Plain. We conducted a field experiment in 2010–2011 and 2011–2012 growing seasons to study the effect of soil-coated ultrathin plastic-film mulching (SCUPFM) in combination with controlled irrigation on water use efficiency and matter production of winter wheat. Compared to traditional planting practice (control), SCUPFM plus zero (rainfed) or small-amount irrigation produced wheat yield more than 7500 kg ha^-1, and consumed 2/3 to 3/4 of water. The yield-based water use efficiency of SCUPFM treatments was 24.8–26.5 kg mm^-1 ha-^1, which was 28.3–41.0% higher than that of the control. Under SCUPFM condition, the biomass-based water use efficiency in the whole growing period was 1.3–2.7 folds of the control, with an earlier peak from heading to jointing stage. Meanwhile, the harvest index also increased under SCIPFM with no or small irrigation. SCUPFM resulted in slow consumption of soil water, and 600 mm of moisture content in 2 m soil profile at seeding stage could provide enough water for the whole growing period of wheat. Water supply from 2 m soil layer was 212.2 mm in loam at Xinji site and 230.0 mm in clay at Shenzhou site. SCUPFM with irrigation or small irrigation before anthesis could significantly enhance net photosynthetic rate (P_n) and decrease transpiration rate (T_r) within 20 days after anthesis. As a result, the leaf-based water use efficiency increased significantly. However, late irrigation at mid-filling stage had no such effect. Therefore, SCUPFM in combination with no or small irrigation at proper stage is effective to maintain wheat yield and increase water use efficiency greatly in North China Plain.

Characteristics of Grain Filling and Nitrogen Translocation of Maize Parent Lines Released in Different Eras in China

LI Cong-Feng,ZHAO Ming,LIU Peng,ZHANG Ji-Wang,YANG Jin-Sheng,DONG Shu-Ting

Acta Agron Sin. 2014, 40(11):  1990-1998.  doi:10.3724/SP.J.1006.2014.01990

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The purpose of this study was to investigate the evolution characteristic of grain filling and nitrogen translocation in maize hybrids parents released in different eras, which provides the critically important information for nitrogen efficient cultivar. Sixteen elite parent lines released in 1960s, 1980s, and 2000s with widely popularized and utilized in China were used in 2007–2008 to analyze the changes in grain filling traits and nitrogen efficiency associated with yields in genetic improvement during the past four decades. The results showed that compared with 1980s and 1960s hybrids and their parents, the modern hybrids and parent lines had higher grain yield significantly, and the correlation analysis indicated that the yield increasing of hybrids closely related to that of their parents (P < 0.05). However, the yield of parents was not significantly related with their ear numbers, and was significant positively correlated with 100-kenerl weight (P < 0.05) in different eras. Compared with 1980s and 1960s hybrids parents, their contemporary parents had higher initiation potential(R₀), delayed time of the highest filling rate, and higher growth amount at biggest filling rate (W_max) and the highest grain filling rate (G_max). Also, the modern hybrids parents maintained higher dry matter accumulation, stem-sheath matter exportation rate, and stem-sheath matter contribution. As far as nitrogen translocation, the modern hybrids parents had higher N accumulation amount (P < 0.05), without obvious advantages in transportation rate and contribution rate, and higher nitrogen utilization efficiency (NUE) and higher nitrogen harvest index (NHI) (P < 0.05). These demonstrated that the modern hybrids parent lines maintain higher grain yield and nitrogen efficiency, which is closely correlated with stronger grain filling ability and organic matter accumulation efficiency.

Differences in Yield Response to Nitrogen Fertilizer among Rice Cultivars and Their Relationship with Root Morphology and Physiology

LIU Li-Jun,WANG Kang-Jun,BIAN Jin-Long,XIONG Yi-Wei,CHEN Lu,WANG Zhi-Qin,YANG Jian-Chang

Acta Agron Sin. 2014, 40(11):  1999-2007.  doi:10.3724/SP.J.1006.2014.01999

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Yield responses to nitrogen (N) rates in indica rice cultivars Tianyouhuazhan, Liangyoupeijiu and japonica rice cultivars Lingxiangyou 18 and Ningjing 1 were investigated and showed significant differences among them. The optimal N rates in Tianyouhuazhan and Lingxiangyou 18 were only 242.5–255.5 kg ha^-1, significantly lower than those in Liangyoupeijiu and Ningjing 1 (327.3–328.0 kg ha^-1), when the maximum grain yield (10.1–10.3 t ha^-1) reached. The agronomic use efficiency and partial factor productivity of N fertilizer were much higher in Tianyouhuazhan and Lingxiangyou 18 than in Liangyoupeijiu and Ningjing 1, indicating that the yield is much more sensitive to N rate in the former two cultivars than in the latter two rice cultivars. Under high-yielding (10.5–10.9 t ha^-1) conditions, root dry weight, root length and total root absorbing area at main growth stages were lower, but the root active absorbing area and its ratio to total root absorbing area, root bleeding sap and root activity were higher in Tianyouhuazhan and Lingxiangyou 18 than in Liangyoupeijiu and Ningjing 1. These results suggested that increasing root active absorbing area, root bleeding sap and root activity through the regulation of cultivation or breeding will be much more beneficial to decreasing N rate and increasing grain yield and N use efficiency in rice.

Effects of Nitrogen Topdressing Method and Time on Plant Type and Dry Mass Production of Super Early-rice

ZENG Yong-Jun,Lü Wei-Sheng,PAN Xiao-Hua,ZHU De-Feng,TAN Xue-Ming,HUANG Shan,SHANG Qing-Yin,SHI Qing-Hua

Acta Agron Sin. 2014, 40(11):  2008-2015.  doi:10.3724/SP.J.1006.2014.02008

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Two super hybrid early-rice combinations Luliangyou 996 and Ganxin 203 were used to study the effects of nitrogen topdressing method and time on plant type and dry mass production. The results showed that, compared with the treatment of nitrogen top dressed one time at the 5th day after transplanting one time, higher grain yields were obtained in the treatments of fractionalized top-dressing due to the longer top three internodes, stronger stem and ideotype plant, high chlorophyll contents in leaves and dry matter accumulation from heading to maturity. Under the condition of 20% nitrogen top-dressed at the 5th day after transplanting, 30% panicle nitrogen fertilizer applied in the second leaf age from top was beneficial to obtaining a higher grain yield resulting from the reasonable stems-leaves distribution of the plant and the high amount of dry matter production after heading. If the panicle nitrogen fertilizer applied earlier than that time, the grain yield would be reduced because of the too long leaves, too large leaf drop angle, less spikelet number per panicle, low grain-leaf ratio and low dry matter production after heading. Grain yield would be also reduced if the panicle nitrogen fertilizer applied too late because of the low leaf area index and low dry matter production before heading.

Some Characteristics of Mechanically Transplanted Pot Seedlings in Super High Yielding Population of Indica-japonica Hybrid Rice Yongyou 2640

HU Ya-Jie,ZHU Da-Wei,QIAN Hai-Jun,CAO Wei-Wei,XING Zhi-Peng,ZANG Hong-Cheng,ZHOU You-Yan,CHEN Hou-Cun,WANG Hong-Yang,DAI Qi-Gen,HUO Zhong-Yang,XU Ke,WEI Hai-Yan,GUO Bao-Wei

Acta Agron Sin. 2014, 40(11):  2016-2027.  doi:10.3724/SP.J.1006.2014.02016

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In order to identify the characteristics of super high yielding population and its yield formation in mechanically transplanted pot seedlings of rice with wheat straw return, we selected a large panicle type indica-japonica hybrid rice Yongyou 2640 as material in Donghai, Xinghua and Hai’an, and analyzed grain yield and its components and characteristics of its super high yielding population (SHY 13.5 t ha^-1) and high yielding population (HY 12.0 t ha^-1). The results showed that, compared with HY, SHY had more total population spikelets owing to its very significantly increased spikelets per panicle. There were no differences in effective panicle, percentage of filled grain and 1000-grain weight between SHY and HY treatments. SHY showed fewer tillers at the early growth stage, achieved expected number of stem and tiller at the critical leaf age for productive tiller, and had lower number of peak tiller at the jointing stage. Then, the number of population stems and tillers began to decrease slowly after jointing. At maturity, the percentage of productive tiller in SHY was higher than that in HY. The leaf area index of SHY was lower than that of HY at the critical leaf age for productive tiller and the jointing stage, the max leaf area index was about 8.5 at booting, which decreased stably after booting, and with the value above 3.5 at maturity. The dry matter accumulation of SHY was comparable to that of HY at the critical leaf age for productive tiller and at the jointing stage, increased greater after jointing, and was higher at booting, heading and maturity than that of HY. The ratio of total biomass accumulation was higher in SHY than in HY at the middle and late growth stage. The nitrogen accumulation, photosynthetic potential, crop growth rate and net assimilation rate were smaller at the early stage and higher at the middle and late stages in SHY. Therefore, SHY has greater photosynthate production and higher nitrogen accumulation than HY at the middle and late growth stage. In this study, we also discussed the key cultivation techniques for super-high-yielding production of pot seedling mechanical transplanting rice with wheat straw return.

Effect of Nitrogen Application Methods on Crop Yield and Grain Filling Characteristics of Maize in Maize-Soybean Relay Strip Intercropping System

DONG Qian,YONG Tai-Wen,LIU Xiao-Ming,LIU Wen-Yu,XU Ting,SONG Chun,WANG Xiao-Chun,YANG Wen-Yu

Acta Agron Sin. 2014, 40(11):  2028-2039.  doi:10.3724/SP.J.1006.2014.02028

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Nitrogen fertilizer overused and low use efficiency in agricultural system leads to wasting resources and environment pollution, which is unfavorable for the sustainable agricultural production.In order to improve the nitrogen use efficiency in maize-soybean intercropping system, a two-year field experiment was conducted to investigate the effect of different N application rates and distances on dry matter accumulation and translocation during post-anthesis and grain filling of maize, and the total crop yield in maize-soybean relay strip intercropping system. The experiment included three N application rates [210, 270, and 330 N kg ha^-1, which represent reduced 36% (RN36%), 18% (RN18%), and conventional N application amount (CN) , respectively] and four fertilizer application locations [the N fertilizer was applied in the area between the maize and soybean plant rows, the distance from the fertilizer application locations to maize rows was 0 cm (D1),15 cm (D2), 30 cm (D3) and 45 cm (D4), respectively]. The results showed that, compared with CN, dry matter translocation amount and rate, and its contribution to grain yield during maize post-anthesis in the RN18% treatment increased by 22.65%, 18.75%, and 15.90%, respectively, the average filling rate and the maximal filling rate of maize increased by 9.79% and 10.76%, the grain yield of maize, soybean and total crop yield in the maize-soybean relay strip intercropping system increased by 4.95%, 7.07%, and 5.35%, respectively. The fertilizer application locations significantly affected the dry matter accumulation and contribution to grain yield during maize post-anthesis. The fertilizer effect was optimal when the fertilizer application distance was between 15 and 30 cm. With the reduced 18% N application, the average filling rate, the maximal filling rate, grain number per spike and 100-kernel weight of maize in the treatment of D2 were increased by 10.32%, 10.92%, 9.08%, and 4.75%, respectively, compared with the treatment of D1. The maximal grain yields of maize and soybean in this maize-soybean relay strip intercropping system were observed in the treatment of RN18% and D2. It is concluded that reduced N application rate (RN18%) and properly N application locations (15–30 cm to maize row) could promote the dry matter accumulation and translocation during maize post-anthesis, increase the maize grain filling rate, grain number per spike and 100-kernel weight, which could further improve the total grain yield of maize and soybean in this intercropping system.

Effects of Precision Seeding without Thinning Process on Yield and Yield Components of Cotton

DAI Jian-Long,LI Zhen-Huai,LUO Zhen,LU He-Quan,TANG Wei,ZHANG Dong-Mei,LI Wei-Jiang,XIN Cheng-Song,DONG He-Zhong*

Acta Agron Sin. 2014, 40(11):  2040-2045.  doi:10.3724/SP.J.1006.2014.02040

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Thinning is a considerably popular practice in cotton field management in the Yellow River valley of China, but such a traditional practice is currently facing a big challenge because of labor costs and time consuming. The objective of the present study was to determine the effects of precision seeding on seed cotton yield and yield components so as to provide a new alternative technique to simplify cotton cultivation in the Region. A three-year field experiment was conducted at four experimental sites (Linqing, Xiajin, Huimin and Dongying) to comparatively investigate the effects of precision seeding without thinning on plant population density, seed cotton yield and yield components, with conventional seeding with thinning (seeding rate of 22.5 kg hm^–2 and thinning seedlings two times after emergence) as the control. There existed significant interaction effects among planting years, experimental sites and planting patterns on plant density, seed cotton yield and number of bolls per unit area. In 2011–2013, the plant population reached 4.5–8.5 plants m^{–2 in precision seeding treatment at ten out of twelve sites, and number of bolls per unit area and seed cotton yield were equivalent to those of conventional seeding at these ten sites. However, the seed cotton yield of precision seeding treatment at Dongying in 2011 and at Huimin in 2012 was significantly reduced by 14.2% and 5.5% owing to the low density (3.53 and 3.63 plants m–2}) and their boll number was reduced by 13.8% and 9.7% relative to that of conventional seeding treatment. There was no significant difference in single boll weight between the two seeding patterns. The yield reduction of precision seeding treatment at two experimental sites was mainly attributed to the decrease in number of bolls per unit area as a result of reduced plant density. Therefore, costs saving without yield reduction can be realized through precision seeding under the support of improved seeding quality and a relatively high plant density. Precision seeding without seedling thinning can be one of the simplified cultivation measures of cotton production in the Yellow River valley of China.

RESEARCH NOTES

Effects of Irrigation and Nitrogen on Antioxidant Contents in Yumai 49-198 Grains

SUN De-Xiang,MA Dong-Yun*,WANG Chen-Yang,LI Yao-Guang,LIU Wei-Xing,LI Qiu-Xia,FENG Wei,GUO Tian-Cai*

Acta Agron Sin. 2014, 40(11):  2046-2051.  doi:10.3724/SP.J.1006.2014.02046

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Two field experiments were carried out in Wenxian and Zhengzhou of Henan Province in 2012–2013 wheat season to study the effects of nitrogen (N) application rate and irrigation on total phenol, flavonoids, and carotenoid contents and antioxidant activity in winter wheat cultivar Yumai 49-198. In the N application range of 0–300 kg ha^-1, all indices tested increased with increasing N rate and reached peak values under 300 kg ha^-1. With the increase of irrigation frequency (0–2 irrigations), total phenol and flavonoids contents and antioxidant activity had the maximum values under one irrigation condition at jointing, whereas the carotenoid content varied across locations. The interaction between N application rate and irrigation had a significant effect on antioxidants in wheat grain. Treatments of irrigation at jointing stage plus N application of 240–300 kg ha^–1 resulted in the high antioxidant content and antioxidant activity, whereas twice irrigation at jointing and anthesis stages plus N application of 240–300 kg ha^–1 resulted in antioxidant accumulation. Total phenol and flavonoids contents were positively correlated with antioxidant activity, indicating that high contents of total phenol and flavonoids were favorable for high antioxidation. The correlations of grain antioxidant content with soil moisture and NO₃^--N content varied in different soil layers. Generally, N fertilizer had the effect on increasing total phenol and carotenoid contents and soil water had the effect on accumulating flavonoids.

Discussion of Multistage Sampling Optimum Test Plans on Rice Cadmium Detection for Jiangsu Province

WANG Wei,SONG Wen,YIN Shuang-Yi,XU Chen-Wu

Acta Agron Sin. 2014, 40(11):  2052-2056.  doi:10.3724/SP.J.1006.2014.02052

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A three stage sampling survey as a real example was used to investigate the optimal plan of the sampling survey for cadmium in rice in Jiangsu Province. F-test showed that differences of the survey among cities and sampling villages were both very significant, and the error variance among cities was the largest in the experiment. In this paper, considering the survey expenses, the optimal sampling plan was explored under a certain accuracy. The results indicated that six cities were randomly sampled and twenty villages or agricultural extension stations were selected at random from each city, with twice sampling in each village in order to increase the precision of the survey. If there is a lack of funds, on the basis of ensuring the current sampling accuracy, we suggest that ten villages or agricultural extension stations from each city can be sampled alternatively.