Table of Content

12 May 2017, Volume 43 Issue 05

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REVIEW

Key Technologies for Light and Simplified Cultivation of Cotton and Their Eco-physiological Mechanisms

DONG He-Zhong,YANG Guo-Zheng,LI Ya-Bing,TIAN Li-Wen,DAI Jian-Long,KONG Xiang-Qiang

Acta Agron Sin. 2017, 43(05):  631-639. 

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Light and simplified cultivation (LSC) of cotton refers to the use of modern agricultural equipment instead of manual operation, the simplification and minimization of field management and operations, as well as the integration of agricultural machinery and agronomic technologies to reduce production costs and labor intensity during cotton farming and cultivation. The connotation, key technical contents and the related eco-physiological mechanisms of LSC are reviewed in this paper. The achievement of easy and convenient as well as cost-saving and benefit-increasing production of cotton is dependent on the key technologies of LSC, mainly including practices of precision seeding, simplified seedlings nursing and transplanting, high-efficient fertilization, water-saving irrigation and regulation of fruiting distribution and so on. The mechanism of well-established strong seedlings by individual seeding lies in the hypocotyl differential expression of hook formation genes HLS1 and COP1 as well as hypocotyl elongation genes HY5 and ARF2 during seed germination and emergence. The mechanism of the inhibited growth and development of vegetative branches by close-planting lies in differential expression of genes related to hormone synthesis in cotton plants. That of yield stability lies in the adaptive coordination among yield components, biomass, and harvest index under LSC. Optimized and concentrated fruiting in cotton plants can be realized through the establishment of a high photosynthetic efficiency population in terms of the required LAI and its dynamics, rational plant height and the ratio of seed cotton to stalks. The absorption of fertilizer N in cotton occurs mainly within 20 days after flowering and is mainly distributed to the reproductive organs with the highest use efficiency when N fertilizer applies at early flowering which provides a theoretical basis for efficient and simplified fertilization of cotton. The mechanism of water use efficiency improvement through partial root-zone irrigation (PRI) lies in the enhanced water absorption in the irrigated root side, which is regulated by the shoot-sourced jasmonic acid transported through the phloem. In order to provide a more powerful theoretical and technical support for LSC of cotton in the future, on the one hand, in-depth study is required to reveal the physiological and ecological mechanisms of LSC; on the other hand, it is necessary to further reform and optimize the cotton cropping systems, to innovate the key cultivation techniques, and to develop the corresponding agricultural equipment with better integration of agronomic technology. Improved LSC technologies will further promote the sustainable development of cotton production in China.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Cloning and Expression Analysis of Alkane Hydroxylase Gene MAH1 from Brassica napus

XU Yi**,PENG Yang**,LI Shuai,ZHAO Qiu-Ling,ZHANG Shuang-Juan,LI Jia-Na,NI Yu*

Acta Agron Sin. 2017, 43(05):  640-647.  doi:10.3724/SP.J.1006.2017.00640

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In wax biosynthesis, the mid-chain alkane hydroxylase (MAH) catalyzes the hydroxylation reaction from alkanes to secondary alcohols and further to corresponding ketones. In this study, using Arabidopsis P450-dependent enzyme CYP96A15 / MAH1 gene as a probe, the full-length coding sequences of two Brassica napus MAH1 genes, BnMAH 1-1 (GenBank Accession: KT795344) and BnMAH1-2 (GenBank Accession: KT795345), were isolated by in silico cloning and RT-PCR. The ORF lengths of BnMAH1-1 and BnMAH1-2 were 1491 bp, and no intron was included. BnMAH1-1 and BnMAH1-2 shared 92.4% and 90.9% of sequence identity at nucleotide and amino acid level, respectively. The predicted BnMAH1-1 and BnMAH1-2 protein contained 496 amino acid residues, with typical P450 protein family conserved domains P415xR417x, K helix (E359xxR362), C-terminal hemopexin-like domain (F436xxGxRxCxG445) and oxygen binding zone (A/G)G309x(D/E)T312(T/S). NCBI BlastN, multiple alignment of amino acid sequence, and phylogenetic analysis showed that they were most homologous to A. thaliana CYP96A15/MAH1. Real-time quantitative PCR showed that BnMAH1-1 and BnMAH1-2 were mainly expressed in stem, leaf, flower, and silique. The highest expression level was found in leaf and the lowest was in root, which was consistent with the wax deposition on aerial part of plant. The expression of BnMAH1-1 and BnMAH1-2 was barely detected in stem and leaf of wax deficient cultivar, suggesting that the reduced wax deposition is due to the down-regulation of MAH1 transcription. The expression of BnMAH1-1 and BnMAH1-2 was significantly induced by exogenous application of SA, MeJA, ACC, and ABA and exposure to NaCl and drought, among which BnMAH1-1 may play a major role in response to water stress.

Physiological Characters and Gene Mapping of a Spotted-leaf Mutant splZ97 in Rice

WEI Li-Quan,LUO Yan-Min,WANG Wen-Qiang,CHI Chang-Cheng,HUANG Fu-Deng,XIANG Xun,CHENG Fang-Min,PAN Gang

Acta Agron Sin. 2017, 43(05):  648-657.  doi:10.3724/SP.J.1006.2017.00648

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A spotted-leaf mutant splZ97 was isolated from a mutant bank generated by EMS mutagenesis of indica restore line Zhen 97. Under field conditions, the brown lesion-mimics mutant splZ97 firstly displayed at the tip and edge of leaf blade at tillering stage, and then gradually spread to whole leaf, resulting in the death of the whole blade when the symptom was severe. At the same time, the major agronomic traits including plant height, grain number per panicle and seed-setting rate were markedly affected. Compared with the wild-type the flag leaf, the second leaf from top and the third leaf from top at heading stage, chlorophyll contents in the mutant splZ97 significantly decreased, while POD (peroxidase, POD) activity, O2? level and MDA (malondialdehyde, MDA) content increased. In addition, CAT (catalase, CAT) activity and soluble protein content of the second leaf from top and the third leaf from top of the mutant decreased as compared with the wild type; on the contrary, the SOD (superoxide dismutase, SOD) activity significantly increased. The histochemical analysis further indicated that O2? accumulated in the leaf blade of the mutant splZ97. In addition, under salt stress at seedling stage, the shoot length and root length of the mutant splZ97 were significantly shorter than these of the wild type. Genetic analysis and gene mapping showed that splZ97 was controlled by a single recessive nuclear gene, which was mapped to a region of 189 kb flanked by two SSR markers RM28466 and RM28485 on the long arm of chromosome 12. These results achieved in the present study would further facilitate the cloning and functional analysis of the gene SPLZ97.

QTL Mapping of Seven Panicle Traits in Rice (Oryza sativa L.) Using Chromosome Segment

SHE Dong, LIU Qiang-Ming, LI Da-Lu, LIANG Yin-Feng, LIU Er-Bao,DANG Xiao-Jing,HONG De-Lin

Acta Agron Sin. 2017, 43(05):  658-668.  doi:10.3724/SP.J.1006.2017.00658

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In order to mine elite alleles of panicle traits in rice, a population of chromosome segment substitution lines (CSSLs) was constructed by using an indica variety II-32B as receptor parent and a japonica variety A7444 as donor parent. QTLs for seven panicle traits were detected using the CSSL population by QTL IciMapping 4.1 software. A total of 26 QTLs for the seven traits were identified across two years. Among the 13 QTLs detected in both years, four QTLs for primary branch number (PBN) were located on chromosomes 1, 6, 8, and 9, with average contribution rate of 15.16%, 13.1%, 29.74%, and 11.21%, and average additive effects in two years of ?1.40, 1.01, 1.11, and 0.77, respectively. Two QTLs for secondary branch number (SBN) were located on chromosomes 6 and 8, with average contribution rate of 10.97% and 21.39%, and average additive effects of 5.45 and 6.36, respectively. Three QTLs for spikelets per panicle (SPP) were located on chromosomes 2, 6, and 8, with average contribution rate of 8.65%, 12.52%, and 31.22%, and average additive effects of ?18.61, 22.23, and 31.87, respectively. One QTL for grains per panicle (GPP) was located on chromosome 8, with average contribution rate of 28.06%, and average additive effect of 30.85. Two QTLs for 1000-grain weight (TGW) were located on chromosome 2, with average contribution rate of 44.65% and 17.51%, and average additive effects of 2.88 and ?2.51. One QTL for grain width (GW) was located on chromosome 10, with average contribution rate of 21.96% in two years, and average additive effect of 0.11. QTL segment controlling SBN, SPP and GPP simultaneously were found on chromosomes 2, 6 and 8, respectively. From the bi-parent DNA sequence comparison, it is speculated that QTL qSBN6 and qSBN8 might be different alleles of Hd1 and DTH8, respectively. QTL qSBN2 was a novel locus detected in the present study. The results of this study provide useful information for pyramiding breeding through marker-assisted selection.

Molecular Regulation and Substance Exchange Dynamics at Dormancy and Budbreak Stages in Overwintering Buds of Tea Plant

TANG Hu,HAO Xin-Yuan,WANG Lu,XIAO Bin,WANG Xin-Chao,YANG Ya-Jun

Acta Agron Sin. 2017, 43(05):  669-677.  doi:10.3724/SP.J.1006.2017.00669

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Early sprouting cultivar Longjing 43 and later sprouting cultivar Biyun were employed in this study. The levels of substance exchange were monitored by detecting the fluorescence signal in calcein treated overwintering buds. The glucanase related genes were identified by sequence homology analysis. Their characteristics and expression patterns during different time of winter were further analyzed. The substance exchanges were detected either in stem-bud unit or mother leaf-stem unit. From the initial formation to release in dormancy, the substance exchange in overwintering buds showed strong-weak-strong variation patterns in both test cultivars, however, the duration of weak exchange stage was much shorter in Longjing 43 than in Biyun. Moreover, there was a close correlation between substance exchange variation pattern and the expression pattern of CsGLU1, a gene identified in tea plant with positive callose hydrolyzation activity. On the basis of promoter sequence analysis, plenty of transcription factor binding sequences related to hormone signaling, cold stimulation and dormancy regulation were found in CsGLU1 promoter region, which validates its putative functions in dormancy regulation. In conclusion, overwintering buds of tea plant have substance exchange with stem and mother leaf both in dormancy and non-dormancy status, furthermore, the variation of substance exchange level was consistent to the changes of dormancy status. CsGLU1 is a callose hydrolyzation related gene, which is supposed to be a key gene regulating tea plant dormancy transition through affecting the substance exchange in overwintering buds. The study provides meaningful results for understanding the changes of dormancy statuses in overwintering buds and deeply exploring the regulation mechanism in tea plant with different sprouting phenophase.

Mapping of QTLs and Heterotic Loci for Flowering Time-related Traits in Maize

YANG Hui-Li,LIN Ya-Nan,ZHANG Huai-Sheng,WEI Xiao-Yi,DING Dong,XUE Ya-Dong

Acta Agron Sin. 2017, 43(05):  678-690.  doi:10.3724/SP.J.1006.2017.00678

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Flowering is an important trait in maize evolution and adaptation. Dissecting the genetic basis of heterosis of flowering will promote the selection for elite hybrids adapted to different ecosystems. In this study, a panel of 203 single segment substitution lines (SSSLs) and its testcross population derived from an elite inbred line Xu178 as recipient parent and inbred line Zong3 as donor parent, were applied for mapping flowering time-related traits in maize. Flowering time-related traits, including days to anthesis (DTA), days to silk (DTA) and anthesis-to-silking interval (ASI), were scored in the two populations at three locations in two years. A total of 40 quantitative trait loci (QTLs) and 37 heterosis loci (HLs) for flowering-related traits were detected. Of them, six QTLs and four HLs were detected at the three locations simultaneously. Of all detected chromosomal regions, there were 11 regions in which the genes affected both flowering time-related QTLs and HLs.

Glu-B1 Silencing Influences Protein Body Formation and Expression of Genes Regulating Synthesis and Processing of Seed-Storage Protein in Somatic mutant Wheat AS208

LIU Hui-Yun,WANG Wan-Qing,LI Xin, WANG Ke,WANG Long,DU Li-Pu,YANG Yue-Ming,YE Xing-Guo

Acta Agron Sin. 2017, 43(05):  691-700.  doi:10.3724/SP.J.1006.2017.00691

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High-molecular-weight-glutenin subunits (HMW-GSs) are important components of seed storage proteins in grains of wheat (Triticum aestivum L.), which determine wheat dough elasticity and processing quality. Using AS208, a wheat somatic variation line with silenced 1Bx20 and 1By20 at Glu-B1 locus, and its originating cultivar Lunxuan 987, we studied the present status of Glu-B1, protein body (PB) formation progress, and expression trends of four kinds of genes (BiP, Dof, PDI, and SPA) related to glutenin synthesis and accumulation at different stages of grain development. Southern blotting analysis revealed that AS208 had two specific bands less than its control parent Lunxuan 987. The fluorescence in situ hybridization (FISH) assay showed six and four chromosomes with signals in Lunxuan 987 and AS208, respectively. These results prove that the Glu-B1 locus has been deleted from the genome of AS208. Compared to Lunxuan 987, AS208 showed similar size and shape of seed PB during PB formation under a transmission electron microscope (TEM). A total of 12 transcription-factor or molecular-chaperone genes were subjected to qRT-PCR assay. These genes were related to glutenin coding genes expression, storage proteins accumulation and processing, PB assembling and transportation. Seven out of 12 genes had simialr expression patterns in AS208 and Lunxuan 987, and eight genes were expressed more in AS208 than in Lunxuan 987, especially the expression levels of Bip, PDI-1, and PDI-5 were 1.5–2.0 folds higher in AS208 than in Lunxuan 987. Our results suggested that Glu-B1 silencing had no significant effect on the formation of PB during wheat grain development, but partially spurred the expression of some genes regulating the synthesis and processing of seed-storage proteins. As a result, via a negative feedback regulation pathway, the protein content in seed and the shape and size of PB remain in similar levels between AS208 and its originating cultivar.

Quantitative Trait Locus Shelling Percentage and Correlation Between Shelling Percentage with Pod Traits in Cultivated Peanut (A. hypogaea L.)

CAI Yan,XU Zhi-Jun,LI Zhen-Dong,LI Xin-Ping,GUO Jian-Bin,REN Xiao-Ping,HUANG Li,CHEN Wei-Gang,CHEN Yu-Ning,ZHOU Xiao-Jing,LUO Huai-Yong,JIANG Hui-Fang*

Acta Agron Sin. 2017, 43(05):  701-707.  doi:10.3724/SP.J.1006.2017.00701

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Peanut is an important oil crops, the shelling percentage of mature pods in peanut is not only associated with peanut oil, also related to the thickness of shell and the extent of easy-shelling. Therefore the shelling percentage is a crucial component for peanut genetic breeding. In this study, 188 recombinant inbred lines (RIL), derived from a cross between two Spanish type peanut cultivars (Yuanza 9102 × Xuzhou 68-4) were used to analyze their in 2013 and 2014 years phenotype data and shelling percentage. Compared with their parents, 29 lines had higher shelling percentage. There were significantly or very significantly negative correlation between shelling percentage and pod size related traits. On the basis of a linkage map (containing 365 markers and 22 linkage groups) constructed before, QTL mapping of shelling percentage traits was conducted by using CIM model in WinQTLcart 2.5. A total of 22 QTLs were detected in the two environments, every single QTL explained the phenotypic variation ranging from 3.61% to 13.49%. A total of five intervals (AHGS0344–AGGS2438, AGGS0957–AHGA7048, AGGS0058–AHGA72558, AHTE0446–AHGA363492, AGGS0311–AGGS2287) were detected in both environments to be located on the linkage group 2, linkage group 3 and linkage group 10 explaining phenotypic variation of 3.68%–13.99%. There were QTLs both related to pod and shelling percentage in four intervals, including AHGS0344–AGGS2438 on linkage group 2 and AGGS1363–AHGA24894 on linkage group 6 containing QTLs related to pod length; AHTE0470–AGGS1233 on linkage group 13 containing QTLs related to pod length and weight of 100-pod; AHTE0381–AGGS0100 on linkage group 18 containing QTLs related to pod, besides genetic effects between shelling percentage and pod traits in the same intervals were opposite.

Cloning and Function Analysis of Metal Tolerance Gene (CsMTP11) in Tea Plant (Camellia sinensis L. O. Kuntze)

YUAN Lian-Yu,CHEN Ying-Juan,WEI Xu,TONG Hua-Rong*

Acta Agron Sin. 2017, 43(05):  708-717.  doi:10.3724/SP.J.1006.2017.00708

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As a member of cation diffusion facilitator family, metal tolerance protein (MTP) is involved in the regulation of heavy metal stress process in plant. Here, we cloned a MTP gene, CsMTP11 (GenBank accession number: KX450265) from Zhongcha 108 tea plant. The full-length cDNA of CsMTP11 is 1197 bp, and the gene encodes a novel protein of 398 amino acids, which shares significant sequence similarity with VvMTP11(90%). The molecular weight and theoretical pI of this protein are 44.85 kD and 5.34, respectively. The conserved domain analysis indicated that CsMTP11 contained five transmembrane domains and the conserved CDF domain. The phylogenetic tree indicated that CsMTP11 had sequence conservation among different species. The transcriptional level of CsMTP11 in old leaf was higher than that in root. Futher more, the heavy metal Mn and Co stresses induced the expression of CsMTP11. The subcellular localization assay using CsMTP11-YFP fusion gene expressed in the Arabidopsis protoplast showed that CsMTP11 was localized in the plasma membranes. CsMTP11 heterologous expression in wild-type yeast BY4741 and the mutants showed that it was able to increase tolerance to Mn and Co. Taken together , our results indicated that CsMTP11 is a member of the Mn-CDF family, and it may be involved in the regulation of heavy metal stress process in tea plant.

Genetic Diversity Analysis of Potato varieties

DUAN Shao-Guang,JIN Li-Ping*,LI Guang-Cun,BIAN Chun-Song,XU Jian-Fei,HU Jun,QU Dong-Yu

Acta Agron Sin. 2017, 43(05):  718-729.  doi:10.3724/SP.J.1006.2017.00718

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Based on the 16 phenotype traits, we performed UPGMA cluster analysis for 454 potato accessions. All the accessions were grouped into two clusters A1 and A at the Euclidean distance of 14.66. The cluster A1 was further grouped into two subclusters A11 and A12 at the Euclidean distance of 12.74. All the accessions were grouped into nine clusters (A, B, C, H, D, E, F, G, and I) at the Euclidean distance of 11.73, and the cluster I was the biggest group, accounting for 57.5% of all the accessions. The cluster analysis more accurately revealed the morphological difference among potato materials, and distinguished the parental materials with different ecological types and genetic differences. Meanwhile, the genetic diversity of 559 potato accessions from worldwide was analyzed with 36 pairs of SSR primers. A total of 134 polymorphic alleles were amplified. Polymorphic alleles were amplified by each pair of primer ranging from one to seven, with a mean of 3.72. The fragment size amplified varied from 106 to 308 bp. The polymorphic information content values (PIC) were from 0.1545 to 0.7743 with a mean of 0.5783, which indicated SSR markers can reflect more abundant genetic diversity information in potato varieties. The further phylogenetic tree analysis showed that all 559 accessions were clustered into three groups. Group I was a mixed one, containing 133 (23.8%) materials from almost all regions. Group II was one mostly gathered by accessions from Europe, North America, Northeast and Northwest regions in China. There were 187 materials in this group, accounting for 33.5% of all. Group III consisted of 239 accessions (42.8%), mainly distributing in North America, South America, Northeast and Southwest regions in China. The clustering results based on phenotypic traits were similar to those based on SSR markers, both highly relating to geographic location, indicating that both method should be combined to use in potato genetic polymorphism evaluation.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of Slow/Controlled Release Fertilizer Types and Their Application Regime on Yield in Rice with Different Types of Panicle

WEI Hai-Yan,LI Hong-Liang,CHENG Jin-Qiu,ZHANG Hong-Cheng*,DAI Qi-Gen,HUO Zhong-Yang,XU Ke,GUO Bao-Wei,HU Ya-Jie,CUI Pei-Yuan

Acta Agron Sin. 2017, 43(05):  730-740.  doi:10.3724/SP.J.1006.2017.00730

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Rice cultivars of Yongyou 2640 with big panicle and Nanjing 9108 with more panicles were adopted in this study. Three types of slow/controlled release fertilizer (polymer-coated urea, sulfur-coated urea, and urea formaldehyde) and two fertilization methods (both slow/controlled release fertilizer and conventional urea as basal fertilizer, slow/controlled release fertilizer as basal fertilizer with conventional urea as tillering fertilizer) were applied in field with conventional urea split fertilization as control (CK). The application of slow/controlled release fertilizer could not increase the yield of Yongyou 2640 that has big panicles and a large amount of spikelets. Compared with CK, most nitrogen of slow/controlled release fertilizers were released at early and middle stage of rice resulting in rapid decrease of LAI, fewer nitrogen accumulation and LAD, insufficient dry matter production and poor grain filling at middle and late stage. For Nanjing 9108, compared with CK, the yield in treatment with urea formaldehyde as basal fertilizer and conventional urea as tillering fertilizer was increased by 5.2% to 5.9%. And rice yield in treatment with polymer-coated urea as basal fertilizer and conventional urea as tillering fertilizer or treatment with both urea formaldehyde and conventional urea as basal fertilizer was similar to that of CK, while the fertilizer application frequency was decreased by 2 to 3 times. Rice yields in treatments with slow/controlled release fertilizer as basal fertilizer and conventional urea as tillering fertilizer were higher than those in treatments with both slow/controlled release fertilizer and conventional urea as basal fertilizer. Compared with the application of both slow/controlled release fertilizer and conventional urea as basal fertilizer, the application of slow/controlled release fertilizer as basal fertilizer and conventional urea as tillering fertilizer could increase the number of rice tillers effectively with a large number of panicles and a higher percentage of productive tillers. Meanwhile, the leaf area index and leaf area duration in treatment with both slow/controlled release fertilizer and conventional urea as basal fertilizer were large, which could enhance the accumulation of dry matter and nitrogen in rice. Rice yield by using different types of slow/controlled release fertilizer showed a tendency of urea formaldehyde > polymer-coated urea > sulfur-coated urea. In Nanjing 9108, the reason of high yield by using urea formaldehyde was that, nitrogen of urea formaldehyde could be steadily released at the late stage also, therefore, the application of urea formaldehyde as basal fertilizer and conventional urea as tillering fertilizer could not only promote tillering but also maintain a high level of productive tiller and leaf area index after peak seedling stage. And the highest leaf area duration, dry matter accumulation after elongating and the final nitrogen use efficiency were beneficial to obtain high yield. In conclusion, for rice cultivars with different types of panicle and various characteristics of yield, the application of optimal type of slow/controlled release fertilizer as basal fertilizer and conventional urea as tillering fertilizer can achieve labor saving and yield increasing simultaneously in rice production.

Effects of Restructuring Tilth Layers on Soil Physical and Chemical Properties and Cotton Development in Continuous Cropping Cotton Fields

WANG Shu-Lin,QI Hong,WANG Yan,ZHANG Qian,FENG Guo-Yi,LIN Yong-Zeng

Acta Agron Sin. 2017, 43(05):  741-753.  doi:10.3724/SP.J.1006.2017.00754

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In continuous cropping cotton areas, the application of rotary tillage in successive years results in solid plow pan, decreases soil water storage ability, enriches nutrients in topsoil and aggravates diseases in the Yellow River Valley of China. The field experiments were conducted with randomized block design in 2014 and 2015 at Wei county experimental station of Cotton Research Institute of Hebei Academy of Agriculture and Forestry Science where cotton was cropped over 20 years. Four treatments including T1 (exchanged a soil layer of 0–15 cm for that of 15–30 cm), T2 (exchanged a soil layer of 0–20 cm for that of 20–40 cm, loosed 40–55 cm layer), T3 (exchanged a soil layer of 0–20 cm for that of 20–40 cm, loosed 40–70 cm layer) and CK (rotary tillage in the depth of 15 cm) were designed to investigate soil physical and chemical properties, cotton development traits, weeds, disease and presenility indices. The results showed that soil bulk density of T2 at 20–40 cm soil layer was 0.13 g cm–3 and 0.15 g cm–3 lower than those of CK in 2014 and 2015, respectively. The contents of total N, available P, available K of T2 and T3 were significantly higher than those of CK and T1 at 20–40 cm soil layer. After irrigation or rain soil water storage in deep layers increased and after sowing at 40–60 cm and 60–80 cm layers compared with CK soil water storage of T2 was 3.5 mm and 5.5 mm higher in 2014, 6.7 mm and 3.4 mm higher in 2015, respectively. At square stage in drought conditions compared with CK soil water storage of T2 at 0–20 cm and 20–40 cm layers was 6.6 mm and 8.7 mm higher in 2014, 4.2 mm and 9.2 mm higher in 2015, respectively. Restructuring tilth layers increased cotton roots greatly and dry matter accumulation above ground was lower than that of CK before flowering stage but higher after flowering stage. The boll number per plant, boll weight and lint yield of restructuring tilth layers were significantly higher than those of CK, and lint yield of T2 was increased by 6.1% and 10.2% compared with CK in 2014 and 2015 respectively. Restructuring tilth layers was effective in weeds control and decreasing diseases and presenility, and the disease and presenility indices (DPI) of T2 were decreased by 41.7% and 31.9% in 2014 and 2015, respectively. Appropriate restructuring tilth layers (T2) is an effective measure to solve problems in continuous cotton cropping fields and increase cotton yields.

Synergistic Effect of Root Interaction and Density on Yield and Yield Components of Wheat/Maize Intercropping System

WANG Yi-Fan, QIN Ya-Zhou, FENG Fu-Xue, ZHAO Cai, YU Ai-Zhong, LIU Chang, CHAI Qiang*

Acta Agron Sin. 2017, 43(05):  754-762.  doi:10.3724/SP.J.1006.2017.00754

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As planting density is a key strategy for improvement of yield and efficiencies in intercropping, the present study was conducted to explore the mechanism of yield response to close planting in intercropping systems. The field experiment was carried out in Hexi oasis irrigation area from 2014 to 2015, of which, three root partition patterns, i.e. no root barrier, nylon mesh barrier (obstructs overlapping of wheat roots with maize roots, but allows water and nutrients to exchange through the nylon mesh) and plastic sheet barrier (prevents water and nutrients from exchange between the two intercrops and no overlapping of wheat roots with maize roots), were combined with two planting density levels, i.e., 90 000 plants ha-1 and 105 000 plants ha-1. The main objective was to determine the effect of above- and below-ground interrelation on grain yield and yield components. The results showed that a complete effect of above- and below-ground interaction increased the intercropping-advantage (i.e. LER) by 48.3% compared to sole cropping. Besides, increase of maize density would led to the LER increased by 9.7%. Generally, the below-ground interaction attributed 21.0% to the LER, and with maize density increased, the contribution rate was increased by 5%. The compensation effect of root overlapping and the complementary of moisture/nutrient exchange attributed 9.0% and 11.1% to the LER, respectively. A complete effect of below- and above-ground interaction also had the highest grain yield, which was increased by 58.8%–62.2% under the higher density and by 36.1%–36.8% under the lower density, compared to the corresponding monocultures. On average, the below-ground interaction attributed 26.5%–31.5% to the grain yield of intercropped wheat, of which, the compensation effect of root overlapping and the complementary of moisture/nutrient exchange attributed 12.9%–13.2% and 12.2–16.0%, respectively. For maize grain yield in the wheat-maize intercropping, the below-ground interaction attributed 9.7%–22.6%, and with maize density increased, the contribution rate was increased by 7.0–11.0%. Increase of maize density increased grain yield by 18.1%–23.3% and 12.5%–21.5% under no root barrier and nylon mesh barrier, this indicated that a complete root interaction could improve the positive effect of close planting. The below-ground interaction attributed 5.5%–11.4% to wheat era number, but not influenced by the density. Similarly, the below-ground interaction attributed 12.5%–16.3% to maize era number, and was further increased by 3.6% to 14.1% with the increase of the density. Based on the result of path analysis, it could conclude that the improvement of grain yield of wheat and maize was mainly attributable to the increase of era number per area. This study showed that increase of planting density could significantly promote the intercropping advantage and the contribution rate of the below-ground interaction. Furthermore, a complete effect of above- and below-ground interaction would facilitate the positive effect of close planting. Accordingly, the results will provide sound theoretical base for the further exploring of the mechanism in intercropping advantage under close planting.

Effects of Plant Growth Regulators on Fiber Growth and Development in Colored Cotton Ovule Culture in vitro

ZHANG Xiao-Meng,LIU Song-Jiang,GONG Wen-Fang,SUN Jun-Ling,PANG Bao-Yin,DU Xiong-Ming

Acta Agron Sin. 2017, 43(05):  763-776.  doi:10.3724/SP.J.1006.2017.00763

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Naturally colored cotton is an ideal textile raw material for the environmental protection and human health. The ovule of cotton varieties Z1-61, Lyumian CC28 and RT-baixu (CK) was cultured in the media with different concentrations of plant growth regulators (MeJA, SHAM, BR, BRz, FLD, ETH, CoCl2, PAL inhibitor, 4CL inhibitor, Urea, and Chl). After 30 days, the fiber color, fiber length, ovule fresh weight, ovule dry weight and fiber dry weight were determined and analyzed with Duncan's new multiple range method. Under the treatments of salicylhydroxamic, phenylalanine ammonia solution enzyme inhibitor and 4CL inhibitor, the color of Z1-61 and Lyumian CC28 cotton fiber was light, and the higher the concentration of the Salicylhydroxamic acid, the lighter of the cotton fiber color. BRz (2.5 μmol L–1) was conducive to the pigment accumulation in brown cotton fiber, while did not have any significant effect on the pigment appearance of green cotton. Both FLD and CoCl2 made the color of brown cotton fiber lighter, while CoCl2 had little influence on the green color cotton fiber and inhibited the formation of callus. Moreover, salicylhydroxamic acid, BRz, FLD, CoCl2, phenylalanine ammonia solution enzyme inhibitor or 4CL inhibitor decreased the fiber length, ovule fresh weight, fiber dry weight and ovule dry weight. In addition, 5 g L-1 urea or 1 mg L-1 Chl were advantageous to the brown cotton fiber pigment synthesis. In conclusion, the growth regulators tested in this study revealed the correlations among pigments synthesis, hormone, flavonoid metabolism and protein metabolism, which would be useful for developing colored cotton cultivars.

Effects of Post-Flowering Shading Intensities on Starch Components and Physicochemical Properties in Waxy and Non-waxy Wheats

LIU Xi-Wei,ZHANG Min,LI Yong,ZHANG Yu-Chun,SONG Xiao-Jun,ZHAO Cheng,CAI Rui-Guo

Acta Agron Sin. 2017, 43(05):  777-786.  doi:10.3724/SP.J.1006.2017.00777

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Post-flowering shading may change the accumulation and structure formation of starch in wheat, resulting in deterioration of flour processing and edible qualities. In this study, we observed the changes of starch components and physicochemical properties under 0%, 30%, or 60% shading intensity after flowering in the non-waxy wheat “Lunxuan 987” and the waxy wheat “Nongdanuo 50206”. Under shading stress, the starch content decreased, however, the proportion of A-type starch granules and the relative crystallinity increased in both cultivars. The starch peak viscosity, hold trough, final viscosity, breakdown, and setback in Lunxuan 987 showed increasing trends with the increase of shading intensity; on the contrary, those in Nongdanuo 50206 showed decreasing changes. In Lunxuan 987, stronger shading stress led to decreased onset temperature, peak temperature, and end temperature, but increased gelatinization enthalpy. In Nongdanuo 50206, these starch thermodynamic parameters all decreased with the increase of shading intensity. The correlation analysis showed that amylose content, amylose/amylopectin ratio, and A-type starch granules volume proportion were positively correlated with the relative crystallinity, peak viscosity, hold trough, breakdown, pasting temperature, and gelatinization enthalpy, but negatively correlated with final viscosity and setback. Our findings suggest that post-flowering shading stress has the negative effects on starch components and particle size distribution, thus, resulting in the changes of relative crystallinity, gelatinization, and thermodynamic properties of wheat starch.