Table of Content

12 January 2012, Volume 38 Issue 01

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REVIEW

Preharvest Aflatoxin Contamination in Crops and Its Management

WANG Hou-Miao, LIAO Bo-Shou

Acta Agron Sin. 2012, 38(01):  1-9.  doi:10.3724/SP.J.1006.2012.00001

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Aflatoxin contamination caused by Aspergillus flavus and A.parasiticus is considered as the most serious factor influencing food safety concerning human health. Preharvest aflatoxin contamination in the field has been a common problem in certain agricultural products including corn, peanut, cottonseed, pepper and tree nuts. Several factors have been associated with preharvest aflatoxin contamination in various crops. Drought stress along with high temperature is the most major environmental factor related to preharvest aflatoxin contamination. Resistance of host plant could effectively reduce the contamination. Genetic enhancement for resistance to fungi invasion and aflatoxin production as well as diseases and insect pests and tolerance to drought through combination of conventional breeding and molecular biology approaches will be the priority for aflatoxin contamination management. Meanwhile, integrated control of diseases and pests with suitable crop management is also crucial to prevent preharvest aflatoxin contamination.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Genetic Analysis for the Diversity of Heading Date of Cultivated Rice in China

WEI Xiang-Jin, XU Dun-Feng, JIANG Ling, WANG Hong-Jun, ZHOU Zhen-Ling, ZHAI Hu-Ju, MAN Jian-Min

Acta Agron Sin. 2012, 38(01):  10-22.  doi:10.3724/SP.J.1006.2012.00010

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Heading date (HD) determines the adaptability to growing regions of cultivated rice. There is a rich diversitycultivated rice. In this study, of HDs in Chinese HDs of 83 typical japonica rice and 51 typical indica rice cultivars native to different regions in China were investigated and their basic vegetative growth (BVG), photoperiod-sensitivities (PS) and temperature-sensitivities (TS) were analyzed. A regression analysis showed that HD was closely correlated with PS and BVG. The PS and BVG of cultivars were weak in high latitude regions of China, and strong in low latitude regions.Genetic analyses of the 134 cultivars were conducted using a set of HD tester lines. The results showed that, on the whole, when the cultivars carried no-PS allele e₁,the plants headed earlier with weaker PS and BVG, when the cultivars carried the PS allele E₁ or E₁^t, the plants headed later with strong PS and BVG. When the cultivars carried the allele Ef-1,the plants headed earlier with weaker BVG, when the cultivars carried the allele Ef-1^t or ef-1, the plants headed later with strong BVG. It suggested that E₁and Ef-1 are two major determinants of variation in heading date of cultivated rice in China. Otherwise, the distribution of different alleles of the major heading date genes in different regions of China was analysed, and the results showed that the leading alleles of the major HD genes in different regions of China was different.

Characterizations of a Mutant Gene hw-1(t) for Green-revertible Albino, High Tillering and Dwarf in Rice (Oryza sativa L.)

GUO Tao, HUANG Xuan, HUANG Yong-Xiang, LIU Yong-Zhu, ZHANG Jian-Guo, CHEN Zhi-Jiang, WANG Hui

Acta Agron Sin. 2012, 38(01):  23-35.  doi:10.3724/SP.J.1006.2012.00023

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A rice (Oryza sativa L.) mutant hfa-1 exhibiting green-revertible albino, high-tillering dwarf was detected from a M₂ population of an American variety Francis by space mutagenesis. hfa-1 displayed distinctive albino before 3rd leaf stage but finally turned to normal green after 3rd leaf stage, and the expression of this phenotype was conditionally controlled by development and temperature. Examining ultrastructure and measuring chlorophyll content indicated that hfa-1 showed albino due to abnormal development of chloroplast, which resulted in inhibiting chlorophyll synthesis and decreasing photosynthetic efficiency. Moreover, the increased tiller number of hfa-1 was ascribed to initiate more higher-order tiller buds. Further endogenous hormones analysis demonstrated that the enhanced tillering capacity of hfa-1 might not result from inhibiting the synthesis of IAA. In addition, the dwarfism of hfa-1 was caused by shortening internodes and was independent of biosynthesis and signal transduction of GA. Genetic analysis indicated that the phenotype of green-revertible albino, high-tillering dwarf in hfa-1 was controlled by a recessive nucleic gene, namely hw-1(t). Using a large F₂ mapping population derived from a cross between hfa-1 and an japonica rice variety, 02428, hw-1(t) was fine mapped into a 46.9 kb of physical distance between two InDel markers, HW27 and HW7 on chromosome 4, where 13 open reading frames were predicted. In the mapping interval LOC_Os04g57320 encoded a IMMUTANTS protein, which was the most properly candidate gene of hw-1(t).

Identification and Characterization of a Novel Fiber Mutant from Transgenic Progeny in Gossypium hirsutum L.

ZHANG Rui, LV Fen-Ni, WANG Hai-Hai, GUO Wang-Zhen

Acta Agron Sin. 2012, 38(01):  36-42.  doi:10.3724/SP.J.1006.2012.00036

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The discovery and identification of the fiber mutant has been vital for genetic and functional genomic research in cotton. In this study, we found a linted-fuzzless fiber mutant in transgenic cotton by Agrobacterium-mediated transformation path, the pure line of the mutant was obtained in T₃ generation. We named the novel fiber mutant as CM mutant. PCR analysis showed that the mutation trait had no relationship with T-DNA insertion, but was deduced to be caused by point mutation in the process of tissue culture. Analysis of inheritance and allelic tests were conducted by crossing CM mutant with TM-1, Junhai1, and a series of fiber developmental mutants such as XinFLM, N1N1, n2n2, and T586 with linted-fuzzless fiber and XinWX, XZ142WX, SL-7-1, and MD17 with lintless-fuzzless fiber, respectively. Of above 10 combinations, the F₁ were fuzzless, and F₂ generations of CM×TM-1 and CM×Junhai1, all showed the separation ratio of 3:1 of linted-fuzzless to linted-fuzzed phenotypes. Based on the genetic analysis, we indicated that there was one dominantly different locus between the mutant and TM-1or Junhai1. Allelic tests and gene mapping all showed that the fuzzless gene of the mutant was allelic to N1, dominantly controlling naked-seed trait. Scanning electron microscopy (SEM) analysis was conducted to investigate the development of fiber cell initials in CM mutant during early developmental stages (0–3 DPA). Just like N1N1 mutant, the mutation gene could result in the process of fiber cell formation and elongation delayed. Compared to N1N1, the lint percentage of CM was significantly higher and 100-seed weight was significantly lower. In conclusion, we speculate on that the mutation gene in CM is one of multiple allele genes of dominant naked-seed N1, and the result also shows the mutation reproducibility for fiber development in different cotton materials.

Polymorphism Analysis of Ten Functional Genes in Brassica napus Using SSCP Method

LI Yuan-Yuan, CHEN Qiang-Fang, FU Ting-Dong, MA Chao-Zhi

Acta Agron Sin. 2012, 38(01):  43-49.  doi:10.3724/SP.J.1006.2012.00043

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A sensitive technology is very necessary to detect the polymorphisms of functional genes in different cultivars, for the coding sequences of functional genes tend to be conserved even between species. Single-strand conformational polymorphism (SSCP) is a desirable method for DNA polymorphism analysis because of its high sensitivity and cost effectiveness. In previous publications, we developed 177 functional markers corresponding to 111 differentially expressed genes between the parents of a Brassica napus hybrid. And, 45 functional markers involved in 39 genes or expressed sequence tags (ESTs) were linked to the QTLs of 12 yield-related traits in the F₂ population from SI-1300×Eagle using SSCP analysis. In the present research, we sequenced some polymorphic bands detected by SSCP analysis to confirm the high sensitivity of SSCP analysis. Firstly, a total of ten primer pairs, which were designed according to ten B. napus functional genes or ESTs, were used to survey polymorphisms between SI-1300 and Eagle. All primers showed polymorphisms, resulting ten polymorphic loci. Subsequently, ten polymorphic bands were randomly selected, sequenced and aligned with the gene sequences for primers designed using the bl2seq software. The results indicated that the average identity was 98%, and the average number of different bases was only 2.3 between the sequenced fragments and their functional genes. Furthermore, the sequence comparison of polymorphic fragments amplified by five primer pairs was performed between SI-1300 and Eagle. The polymorphic fragments are highly conserved between SI-1300 and Eagle, and there were 39 single-nucleotide polymorphisms (SNPs) and five insertion-deletions (INDELs) in the DNA fragments amplified by the five primer pairs. The average frequency of sequence polymorphism was estimated to be one SNP every 30 bp and one INDEL every 233 bp. In conclusion, the sequences of functional genes, which could be really amplified by specific primers, are highly conversed among different cultivars in B. napus, and SNP is the most basic genetic variation for functional genes. This study will provide a foundation for investigating the molecular basis of important traits in rapeseed using comparative genomics.

Factors Affected BC₁F₁ Size for Development of Genome-wide Introgression Lines

YAN Long, LIU Hui-Yong, LI Yang-Hui, ZHANG Meng-Chen, QIU Li-Juan

Acta Agron Sin. 2012, 38(01):  50-54.  doi:10.3724/SP.J.1006.2012.00050

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Introgression lines are important genetic materials for genetics study and breeding. Development of those lines involves cross and backcross processes between recipient and donor parents. The population size of BC₁F₁ is a critical parameter for fully covering donor genome and successfully obtaining desired introgression lines. However, the minimum sufficient number of BC₁F₁ plants is unknown for each species and can not be obtained experimentally. We have developed a computer program by simulating the recombination process during meiosis to define the ideal BC₁F₁ population size. The reliability of the program was confirmed by mathematics and experimental data. Three factors including linkage groups number, linkage group length and gene density were analyzed and all of them had positive relation with the BC₁F₁ population size. The population size increased from 6.06 to 9.49 when the linkage number increased from 5 to 40. The population size was 7.14 when the linkage group length was 80 cM, while it became 8.64 when the length was 200 cM. The population size was 7.65 with the density of 20 cM per gene and 8.22 with 10 cM per gene. The BC₁F₁ population sizes of rice, wheat, maize and soybean were predicted to be 12, 13, 14–15, and 13 by the program with 95% confident level.

Variation and Distribution of Vitamin E and Composition in the Seeds among Different Rice Varieties

ZHANG Gui-Yun, LIU Ru-Ru, ZHANG Feng, XU Yong, SHU Jiang, GU Ming-Hong, LIANG Guo-Hua, LIU Qiao-Quan

Acta Agron Sin. 2012, 38(01):  55-61.  doi:10.3724/SP.J.1006.2012.00055

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Vitamin E, including of tocotrienols and tocopherols, is one of miner nutrients that must be acquired regularly from dietary sources. The structure of tocotrienols differs from that of tocopherols by the presence of three trans-double bonds in the hydrocarbon chain. In this study, a reverse-phase HPLC method was used to simultaneously measure the contents of either tocopherols or tocotrienols in the brown rice, and their contents were compared among 18 indica and 16 japonica cultivars. The results showed that the contents of these vitamin E isomers were extremely different between indica and japonica rice, and the mean content of total tocopherol or vitamin E was significantly higher (P<0.01) in japonica rice than in indica rice, while the total tocotrienol content showed no differences between them. The principal isomer of vitamin E was also different between the two subspecies, for example, γ-tocotrienol was the predominant compound in indica rice, on the contrary, in japonica rice, the most abundant isomer was α-tocopherol. The ratio of total tocotrienols to tocopherols was also significantly higher (P<0.01) in indica (1.61) than in japonica rice (0.95). Pearson’s correlation analysis demonstrated that α-tocopherol content was positively correlated with α-tocotrienol content in rice. The same relationship was also presented between the contents of γ-tocopherol and γ-tocotrienol, but there was a negative correlation between contents of α- and γ-isomers. Taking together, all the present results provide some useful information for research on vitamin E metabolism or nutritional improvement in rice.

cDNA-AFLP Analysis of Differentially Expressed Genes in Tobacco Infected by TMV

CHEN Rong-Beng, LIU Lei, MO Xiu-Qing, QIU En-Jian, WANG Chun-Jun, SONG Bao-Gang, YA Pei-Jiang, YANG Tie-Zhao

Acta Agron Sin. 2012, 38(01):  62-70.  doi:10.3724/SP.J.1006.2012.00062

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Flue-cured tobacco variety Longjiang 925 with high resistance to tobacco mosaic virus (TMV) was used as the tested material, and we selected 240 pairs of primers and amplified cDNA from the tobacco leaf inoculated by TMV. The results showed that approximately 9500 gene transcript fragments were obtained, and twelve inducible expressed gene fragments were selected out by cloning and sequencing. The inducible fragments functions, involve in the nucleic acid metabolism, protein synthesis and modulation, energy metabolism, stress responding, intracellular transport, metabolism of carbohydrates. To validate the functions of these differentially expressed gene sequences obtained, we analyzed TIF2 fragment by real-time PCR with the samples collected at 0, 12, 24, 48, and 72 hours after inoculation, and the mRNAs samples were isolated. The result of real-time PCR indicated that the genes isolated were related to TMV-resistance. Then, both 5′- and 3′-rapid amplification of cDNA ends (RACE) were preformed. A full length cDNA sequence of TIF2 contained 875 bp, with a coding zone of 101 bp to 613 bp conjecturably, encoding 170 amino acids. Analyses of Blastn and Blastp showed that the gene was not homologous to tobacco, and probably was the TMV-resistance related novel gene. The results will be helpful for the future research on tobacco resistant-breeding to TMV in molecule level and so on.

Relationship between Polymorphism at Wx Gene and Amylose Content in Hulless Barley

WU Hun-Lun, ZHAO Yuan, CHI De-Zhao

Acta Agron Sin. 2012, 38(01):  71-79.  doi:10.3724/SP.J.1006.2012.00071

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Hulless barley (Hordeum vulgare L. var. nudum Hook. f.) is a typical crop in Tibetan Plateau in China. Starch, including amylopectin and amylose, is the main storage component in hulless barley, of which amylose is in low content or even absent in the endosperm of waxy barley. The Waxy gene (Wx) located on the short arm of chromosome 7H is a key gene responsible for amylose synthesis, and also acts as a favorable gene in breeding of hulless barley. However, it is difficult to select hulless barley germplasm with Wx due to lack of effective molecular markers. This study aimed to find out molecular markers applicable in the identification of Wx gene. A total of 150 accessions of hulless barley were primarily tested by staining endosperm with I₂-KI, and four accessions (IG107028, Puebla, Huzhushuangcaoren, and APM-HC1905) were found as waxy genotypes. The amylose contents (AC) of the 150 accessions measured using dual-wave length spectrophotometry method varied from 12.4% to 38.5% with an average of 26.0%. The amylose contents of the four waxy genotypes namely IG107028, Brachvtic, Kunlun 2, and Huzhushuangcaoren，were 12.4–18.6% with an average of 16.7%. No genotype was found without amylose. We selected 51 accessions with obvious difference in AC to validate the polymorphism of four pairs of SSR markers. Primers P1 and P3 showed no polymorphism among the 51 accessions, and primer P4 exhibited four types of amplified product, and the fragment size positively correlated with amylose content. The P4 primer was designed according to the sequence of Wx gene on chromosome 7H of barley. Primer P4 can be used as an effective marker in the selection of waxy hulless barley cultivars.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Analysis on Distribution, Yield Structure and Key Culture Techniques of Maize Super-high Yield Plots in Recent Years

CHEN Guo-Beng, GAO Ju-Lin, DIAO Meng, DONG Shu-Ting, LI Shao-Hun, YANG Qi-Feng, LIU Yong-Gong, WANG Li-Chun, XUE Ji-Quan, LIU Jing-Guo, LI Chao-Hai, WANG Yong-Hong, WANG You-De, SONG Hui-Xin, ZHAO Jiu-Ran

Acta Agron Sin. 2012, 38(01):  80-85.  doi:10.3724/SP.J.1006.2012.00080

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Maize high-yield potential and small-area super-high yield research in different areas were conducted in 2006–2010. The geographical distribution, yield components and key culture techniques of 159 maize super-high yield plots with yield of ≥15 000 kg ha^-1 were analyzed comprehensively. Results showed that: (1) most high-yield plots distributed in higher latitude (40°–43°N) and higher elevation regions (1 000–1 500 m) with abundant sunlight and higher temperature in the daytime and lower temperature in the nighttime which were the primary factors affected super-high yield; (2) the yield structure was 88 950 ears ha^-1, 541 kernels per ear, 360.0 g per 1000-kernel, 191.8 g per ear, and the average yield was 16 692 kg ha^-1;the ear and kernel numbers among yield components were correlated significantly with yield; (3) the key culture techniques for maize high-yield was selecting high density tolerant maize cultivar combined with reasonable dense planting, abundant water and fertilizer supply, scientific management, and film mulching.

The Highest Population Productivity of Nitrogen Fertilization and Its Variation Rules in Rice Cultivars

ZHANG Hong-Cheng, MA Qun, YANG Xiong, LI Min, LI Guo-Ye, DAI Ji-Gen, HE Zhong-Xiang, HU Ke, WEI Hai-Yan, GAO Hui, LIU Yan-Yang

Acta Agron Sin. 2012, 38(01):  86-98.  doi:10.3724/SP.J.1006.2012.00086

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Based on the concept of the highest population productivity of N fertilization, we carried out a field experiments with 50 early-maturing late japonica rice varieties which were the representativein the region of Yangtze River, using seven nitrogen applying levels (0, 150, 187.5, 225, 262.5, 300, 337.5 kg ha^-1), to investigate the difference of the most population productivity of N fertilization in varieties. Its relationships with yield components, plant-type characteristics and nitrogen agronomic efficiency were also analyzed. The main results were as follows. (1)With the basic yield capacity of sandy loam being 6 t ha^-1, optimum N levels of 50 tested varieties which were corresponding to their highest population yield converged in the range of 225–300 kg ha^-1, while the highest grain yield showed significant differences, varying from 7.42 to 11.02 t ha^-1.(2) There was significantly positive correlation between the highest productivity of N fertilization and the total spikelet number, with the correlation coefficient of 0.865. The top- and high-level yielding varieties had extremely significantly larger amount of population spikelets than the middle- and low-level yielding varieties, and this superiority of total spikelets was mainly due to the extremely remarkable increase of spikelets per panicle. (3) The highest productivity of N fertilizer rose as the high-efficiency leaf area and the weight per panicle increased. Compared with middle- and low-level yielding cultivars, top- and high-level yielding cultivars performed superior plant type characteristics: the plant height ranged from 105–110 cm, the width of basal internodes was circa 0.65 cm, the high-efficiency leaf area index was higher than 5, and panicles were big. (4) Generally speaking, the theoretical highest population productivity of N fertilization increased with the increasing of corresponding applied N amount. But within each group of similar optimum N level, various rice cultivars produced significantly different grain yields. (5) Taking into consideration of the production capacity and the nitrogen agronomic efficiency of all 50 rice varieties, six varieties with high yield and high efficiency were selected and recommended.

Response of Some Key Enzyme Activities Involved in Nitrogen Metabolism to High Temperature at Filling Stage and Its Relation to Storage Protein Accumulation in Rice Grain

CAO Zhen-Zhen, ZHANG Ji-Fang, HUI Ke-Su, YANG Wei-Li, LIU Guang-Kuai, CHENG Fang-Min

Acta Agron Sin. 2012, 38(01):  99-106.  doi:10.3724/SP.J.1006.2012.00099

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The influence of high temperature after flowering period on the activities of some enzymes, including glutamine synthetase (GS), glutamic-oxaloacetic transaminase (GOT)and glutamic-pyruvic transaminase (GPT) in developing grains, and also its relation to grain storage protein and amino acid accumulations were investigated by using two early-indica rice cultivars grown under two temperature regimes of daily average temperature 32℃ and 22℃, respectively, and expression responses of two GS isoform genes to temperature were detected by real-time fluorescence quantitative PCR(FQ-PCR). The results indicated that the effects of high temperature after flowering period on GOT and GPT activities showed the similar trend, with increasing at early grain filling stage and decreasing at late grain filling stage. However, the increase f total contents of crude protein and various amino acids under high temperature after flowering period were not always due to the enhancement of grain nitrogen transport capacity and protein synthesis ability. GS activity under high temperature was generally higher than that under temperature in the same period. GS2,one of the isoforms of GS gene, was highly expressed in rice endosperm. The expression levels of GS2 was even higher than that of GS1 in late grain filling stage, while high temperature stress regulated GS activity through changing GS1 and GS2 genes transcription level in grain.

Role of Irrigation Patterns in Reducing Harms of High Temperature to Rice

DUAN Hua, SHU Zheng-Hua, XU Yun-Ji, WANG Zhi-Qin, LIU Li-Jun, YANG Jian-Chang

Acta Agron Sin. 2012, 38(01):  107-120.  doi:10.3724/SP.J.1006.2012.00107

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Possible irrigation patterns to reduce the injury of high temperature to rice growth and development were studied using two mid-season indica cultivars of Huanghuazhan and Shuanggui 1. Both high temperature (mean temperature during the day/night at 35.1℃/20.8℃) and normal temperature (mean temperature during the day/night at 29.0℃/20.8℃) treatments and three irrigation patterns, including alternate wetting and moderate soil drying (MD, plants were re-watered when soil water potential reached to -15 kPa), alternate wetting and severe soil drying (SD, plants were re-watered when soil water potential reached to -30 kPa), and well-watered (control, continuously flooded), were conducted during heading and grain filling. The grain yield and quality of rice were investigated. The results showed that under either normal or high temperature, compared with the control, the MD significantly increased seed-setting rate, 1000-grain weight, grain yield, brown rice, milled rice and head rice, and reduced chalky grains and chalkiness degree. The MD also increased the break down viscosity and decreased the setback viscosity. The SD showed the opposite effects. The two cultivars behaved the same. These results indicated that the MD may maintain a higher grain yield and better quality of rice under high temperature. The reduction of relative humidity in the panicle canopy, decreased reactive oxygen (O₂^?) production rate, elevated contents of ascorbic acid, reduced glutathione, and increased concentrations of cytokinins in leaves and spermidine and spermine in grains are the ecological and physiological reasons for reducing harms of high temperature to rice by the MD regime.

Effects of Nitrogen Application Rate and Plant Density on Lodging Resistance in Winter Wheat

WANG Cheng-Yu, DAI Xin-Long, SHI Yu-Hua, WANG Zhen-Lin, CHEN Xiao-Guang, HE Meng-Rong

Acta Agron Sin. 2012, 38(01):  121-128.  doi:10.3724/SP.J.1006.2012.00121

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To make clear on the effects of nitrogen (N) application and plant density on lodging resistance and grain yield of winter wheat, we carried out a field experiment with split-plot design using a middle-spike cultivar, Shannong 15, in Tai’an, Shandong Province, China in 2008–2009 and 2009–2010 growing seasons. The main plot was N application rate with levels of 180 (N1) and 240 kg ha^-1 (N2), and the subplot was plant density with levels of 1.50 (D1) and 2.25 million plants per hectare (D2). The lodging-resistance-related traits including morphological characters, chemical components in basal internode, culm lodging resistance index (CLRI), activities of enzymes involved in lignin synthesis, and grain yield weremeasuredin different growth stages. The results showed that the grain yield was decreased with the increase of N rate or plant density, and the largest grain number per spike, 1000-grain weight and grain yield were observed in the N1D1 treatment. The culm height of center of gravity and length of basal internode were larger in the N1 or D1 treatment than in the N2 or D2 treatment, whereas, the diameter, thickness, filling degree, and mechanical strength of the basal internode and the CLRI value showed an opposite trend. With the increase of N rate or plant density, the cellulose content, lignin content, C/N ratio of basal internode were decreased but the N content was increased. The interaction between N rate and plant density was significant, which resulted in poor lodging resistance under high N rate plus high plant density. Stepwize regression analysis indicated that N rate had more important effect on lodging resistance than plant density. Therefore, under the experimental condition in this study, the N1D1 treatment (180 kg ha^-1 of pure N and 1.50 million plants per hectare) is a proper combination of N application and plant density, which may not only improve lodging resistance of winter wheat but also obtain high grain yield.

Monitoring Cotton Field with Suspected Verticillium wilt Using Satellite Remote Sensing with TM Satellite Image as an Example

CHEN Bing, WANG Ke-Ru, LI Shao-Hun, XIAO Chun-Hua, SU Yi, TANG Jiang, CHEN Jiang-Lu, JIN Xiu-Liang, LV Yin-Liang, DIAO Mo-Yang, WANG Jie

Acta Agron Sin. 2012, 38(01):  129-139.  doi:10.3724/SP.J.1006.2012.00129

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The cotton fields of suspected disease were diagnosed and classed through analyzing and electing best period (single period) in multi-temporal information of TM image, which would provide the technology support to take the active measurements for cotton industry and increase the yield and efficiency of cotton production. Multi-temporal satellite images and data of ground surveying were taken in research areas. On the basis of them, the best wave band and the best period used to recognize cotton fields infected disease were selected and the cotton fields with suspected Verticillium wilt were classified and tested. The results showed that the health and disease cotton fields had obvious difference in the major cotton growth stages, it was feasible to diagnose cotton field with disease through the interpretation symbol of satellite image. In addition, TM₄ band of satellite could be regarded as the best wave band to monitor cotton field with disease; the peak boll forming sage (from the last ten-day of July to mid Aug) could be regarded as the best period to monitor disease of cotton with TM image. On the basis of above analyses, using the supervised classification of parallelepiped, the cotton fields with suspected Verticillium wilt were divided into three classes: health, light disease and severe disease cotton fields. The proportions of cotton field infected disease were about 29% and 23% in two years, respectively. The tested results indicated the overall accuracy and kappa coefficient were both over 85% at the crucial growth periods in two years. The further analysis revealed the disease condition within cotton field infected Verticillium wiltcould be reflected by the thematic map of cotton disease. Thus, it is feasible to diagnose the cotton fields with suspected Verticillium wilt by multi-temporal satellite data.

Effects of Nighttime Temperature Increase at the Late Growth Stage on the Cotton Fiber Yield and Fiber Strength in Xinjiang

TIAN Jing-Shan, HU Xiao-Bing, GOU Ling, LUO Hong-Hai, ZHANG E-Li, ZHAO Rui-Hai, ZHANG Wang-Feng

Acta Agron Sin. 2012, 38(01):  140-147.  doi:10.3724/SP.J.1006.2012.00140

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Cotton yield and quality depend on genotype and environment interaction. Temperature is one of key factors to influence fiber synthesis at the late growth stage of cotton. In the paper, Using early-maturing cotton varieties as experimental material, increased night temperature was simulated in the field using far-infrared quartz tube set mounted in semi-mobile incubators, relative to normal night temperature treatment (control), to determine the effects of night temperature on the cotton yield and fiber strength at the late growth stage. The results showed that compared to the control, increased night temperature shortened cotton bolling period, the rapid accumulation at age of single boll fiber dry matter came earlier, and the single boll fiber yields significantly increased in the late growth stage of cotton. Increased night temperature mainly moved up the transformation from soluble sugar to fiber, and the duration was evidently extended, and also the initial time of rapid accumulation of cellulose synthesis came in advance, but the minimum night temperature ≥15.0℃ statistically had no effect on the duration of the rapid accumulation and the maximum accumulation rate before end of cellulose speedy accumulation period. Simultaneously, the fiber strength was affected slightly by minimum night temperature ≥14.1℃ during in the cotton fiber development. So the minimum temperature in the nighttime was a major factor associated with soluble sugar transformation and cellulose accumulation. Consequently, dry matter accumulation and fiber yield of single boll were closely associated with the minimum nighttime temperature.

Effect of Wheat/Maize/Soybean and Wheat/Maize/Sweet Potato Relay Strip Intercropping on Soil Nitrogen Content and Nitrogen Transfer

YONG Ta-Wen, YANG Wen-Yu, XIANG Da-Bing, MO Yan, LIU Wei-Guo, WANG Xiao-Chun

Acta Agron Sin. 2012, 38(01):  148-158.  doi:10.3724/SP.J.1006.2012.00148

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The aim of this study was to characterize nitrogen transfer in the relay strip intercropping system of wheat/maize/soybean, and to investigate the N promotion mechanism. A pot experiment was conducted to determine the soil N content and transfer in the relay strip intercropping of wheat/maize/soybean and wheat/maize/sweet potato using the direct ¹⁵N foliar feeding technique. The N application rates were 0, 150, 300, and 450 kg ha^-1. The results showed that N application increased the soil total N contents in wheat and maize seasons. The total N content of soil reduced when N applied in an excessive rate, and the highest values of soil total N content appeared at the N rate of 150–300 kg ha^-1. Moreover, the soil total N contents in wheat and maize seasons in the relay strip intercropping of wheat/maize/soybean were higher than those in the wheat/maize/sweet potato system. After soybean planted in the relay strip intercropping, the soil total N contents increased by 38.6%, 20.2%, 9.4%, and 16.7% at applied N rates of 0, 150, 300, and 450 kg ha^-1, respectively. Whereas after sweet potato planted, they were reduced by 3.1%, 1.8%, 14.0%, and 3.8%, respectively. Therefore, the soybean season was beneficial to maintaining soil fertility. The soil NO₃-N contents in wheat and maize seasons increased with the raising of N application rate, and the values in wheat/maize/soybean system were lower than those in wheat/maize/sweet potato system. The soil NO₃-N contents in soybean season were higher than those in sweet potato season. Bi-directional ¹⁵N transfer existed in both relay systems. The amount of transferred ¹⁵N reduced with the increasing of N application rate. The strength and amount of net transferred ¹⁵N in the wheat/maize/soybean system were higher than those in the wheat/maize/sweet potato system. The amounts of net transferred ¹⁵N in wheat, maize, and soybean in the wheat/maize/soybean system increased by 3.3–12.1%, 27.0–166.2%, and 26.2–78.7% compared to the corresponding crops in the wheat/maize/sweet potato system, respectively. Moreover, the directions of the ¹⁵N transfer were evident, which were from maize to wheat, from soybean to maize, and from maize to sweet potato.

Changes in Starch Accumulation and Activity of Enzymes Associated with Starch Synthesis under different Nitrogen Applications in Japonica Rice in Cold Region

DU Xiao-Dong, ZHAO Hong-Wei*, WANG Jing-Guo, LIU Hua-Long, YANG Liang, HU Jing, SONG Jin-Tong

Acta Agron Sin. 2012, 38(01):  159-167.  doi:10.3724/SP.J.1006.2012.00159

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The effect of different nitrogen application regimes on rice starch accumulation, starch biosynthetic enzyme activity and the relationship between them after flowering was studied under same N amount with different application periods time, and Songjing 6 and Songjing 9. The results showed that reducing the proportion of base nitrogen fertilizer and increasing the nitrogen fertilizer proportion in grain killing period could promote grain filling, increase total starch content, and appropriately increase amylopectin content. Under different nitrogen applications, the trends and the peak activities of changed of key enzymes associated with starch synthesis were different. In grain filling stage, the activities of ADPG pyrophosphorylase and Q enzyme could be improved significantly by reducing base N and increasing ear-N. In the early grain filling stage, the SSS activity was decreased with decreasing the ratio face fertilizer to tillering fertilizer. the activities of ADPG pyrophosphorylase, Q enzyme, and SSS were significantly correlated the content of starch. Fertilizer application ratio influenced both the content and the composition of starch. Reasonable fertilizer application ratio (5:3:1:1, at processing stage, tillering stage, panicle stage and grain filling stage) could regulate the activities of key enzymes for starch synthesis in different stages and increase contents of starch and starch components.

RESEARCH NOTES

Analysis of Phenotype and Physiology together with Mapping of a Leaf Apex Dead Gene (lad) in Rice (Oryza sativa L.)

DU Jing, FANG Li-Kuai, SANG Xian-Chun, LING Yang-Hua, LI Yun-Feng, YANG Zheng-Lin, HE Guang-Hua, ZHAO Fang-Meng

Acta Agron Sin. 2012, 38(01):  168-173.  doi:10.3724/SP.J.1006.2012.00168

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Leaf plays an important role in photosynthesis. Studying the leaf premature senescence is important for increasing the economic yield of crop. A new mutant of rice leaf apex dead reported in the paper derived from a restorer line Jinhui10 treated by EMS. In the mutant, the leaf apexes appeared normal before the 5th leaf unfolded. However, the leaf apexes of all leaves except the 5th leaf exhibited yellow and gradually died when the 5th leaf fully expanded; and afterwards the apexes of new fully expanded leaves became yellow and dead. The physiological and biochemical analysis showed that the lad mutant contained lower contents of chlorophyll and soluble protein compared with the wild type control, and the activity of SOD was abnormal. Again, the plant height, leaf length, grain number and seed setting rate of the lad mutant were significantly lower than those of the control. Thepremature senescence mutant was controlled by a single recessive nuclear gene. And the LAD gene was mapped between the SSR markers SWU11-19 and SWU11-5 on the 11th chromosome, with 13 cM of the genetic distance. Furthermore, the LAD gene was co-segregated with the markers SWU11-25 and SWU11-27. The results laid a favorable foundation for further map-based cloning and functional analysis of the LAD gene.

Characteristics and Correlation Analysis of N and P Uptake and Utilization of Early Maturing Late Japonica under Different N Fertilizer Levels

YANG Xiong, MA Qun, ZHANG Hong-Cheng, WEI Hai-Yan, LI Guo-Ye, LI Min, DAI Ji-Gen, HE Zhong-Xiang, HU Ke, ZHANG Qiang, GUO Bao-Wei, GE Meng-Jie

Acta Agron Sin. 2012, 38(01):  174-180.  doi:10.3724/SP.J.1006.2012.00174

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A field experiment was carried out with 50 early-maturing late japonica rice varieties adopted in the region of Yangtze River under seven nitrogen application levels (0, 150.0, 187.5, 225.0, 262.5, 300.0, and 337.5 kg ha^-1) to investigate N and P accumulation, N and P uptake rate, N and P use efficiency and correlations between them. The main results were as follows. (1) In the range of 0–337.5 kg ha^-1, N concentration and accumulation amount were significantly increased with the increase of N fertilizer under three growth stages. P concentration and accumulation amount were significantly improved with the increase of N fertilizer at elongation and heading of rice, but P accumulation was significantly deceased at maturing when N fertilizer was too high. (2) N and P uptake rates were significantly increased with the increase of N fertilizer during sowing to elongation. During elongation to heading, N and P uptake rates were increased at first and then decreased with the increase of N fertilizer. There were no regular patterns of N and P uptake rate under different N fertilizer levels, and the maximum of N and P uptake rate was at 225.0 kg ha^-1 N fertilizer during heading to maturing of rice. (3) N and P use efficiencies of grain yield production (NUEg and PUEg) were significantly decreased with the increase of N fertilizer (except PUEg at 0 kg ha^-1). There was a parabola regular pattern of N and P harvest index in the range of 0–337.5 kg ha^-1 N fertilizer, and the maximum was at 262.5 kg ha^-1 N fertilizer. (4)The relationship of nitrogen and phosphorus uptake and utilization was significantly synergic during the rice growth stage. Rice yield was significantly correlated with N/P accumulation and N/P uptake rate before heading. Increasing N fertilizer may help to increase nitrogen and phosphorus uptake and utilization. But it may not increase or even decrease when N fertilizer is too high.

Anatomical Structure of Leaf in Different Mung Bean Varieties

GAO Xiao-Li, GAO Jin-Feng, FENG Bai-Li, WANG Feng-Ke, CHAI Yan

Acta Agron Sin. 2012, 38(01):  181-185.  doi:10.3724/SP.J.1006.2012.00181

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The morphological stracture is the basis of physiological function of plants, leaf is the main organ of photosynthesis that gives seed yield in mung bean [Vigna radiata(L.)Wilczek], so it is necessary to analyze anatomical structure of leaf in different genotypes of mung bean. The objective of this experiment was mainly to study the anatomical structure in the leaves of mung bean genotypes with different photosynthetic capabilities and reactive oxygen metabolisms in the flowering and podding stage, and explore the anatomical structure changes of mung bean during the whole aging process. The results showed that after the plants flowered, their functional leaves aged gradually from bottom to top. In the aging process, leaf structures gradually senesced, mesophyll cells gradually disintegrated, palisade tissue arrangement tended to disorder, thickness of leaf and palisade tissue, ratio of palisade tissue thickness to leaf thickness tended to decrease. There were significant differences in dynamic changes of leaf structure of mung beans. Compared with low-yield varieties, the leaf structures of the high-yield varieties aged slower and thickness of leaf was thicker, palisade tissue more developed and the structure of organism was closer, and mesophyll cells disintegrated slowly at the late growth stage. The above results indicated that the change in anatomical structure of leaf was closely correlated with the yield, and the genotypes of mung bean with high yield potential had thicker functional leaves and more developed palisade tissue.

Establishment of a HPLC-UV Method for Simultaneous Determination of DON, 15ACDON, and 3ACDON in Wheat

YANG Dan, GENG Zhi-Meng, MA Hong-Xiang, TAO Jin-Bao, ZHANG Xu, ZHANG Beng-Beng, ZHANG Feng

Acta Agron Sin. 2012, 38(01):  186-189.  doi:10.3724/SP.J.1006.2012.00186

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A HPLC-UV method was established to determine deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ACDON) and 15- acetyldeoxynivalenol (15-ACDON) in wheat. Wheat sample was extracted by water, and the extracting solution was precipitated with an equal volume of ethanol followed by solid phase extraction with Oasis HLB cartridge. Qualitative and quantitative analyses of DON, 15ACDON and 3ACDON were done by HPLC-UVD using gradient elution program with acetonitrile and 0.005% phosphoric acid solution. Results showed that at the linear range of 0.5–15.0 mg L^-1, the recoveries were 89.8%, 93.4%, and 92.9%, respectively. The relative standard deviations were 2.2%, 2.0%, and 2.5%, respectively, and the detection limit levels were 12.2, 10.5, and 16.7 μg kg^-1, respectively. The method was accurate and reproducible. Sample purification lessened interference peaks, and due to the use of organic solvents was greatly reduced, the cost was decreased. Therefore, the method was suitable for the large batch determination of type B trichothecenes in wheat.