Acta Agronomica Sinica

Table of Content

12 August 2013, Volume 39 Issue 08

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REVIEW

Progress on Gene Regulatory Mechanisms by Small RNAs during Plant Polyploidization

ZHAO Xu-Bo,LI Ai-Li,MAO Long*

Acta Agron Sin. 2013, 39(08): 1331-1338. doi:10.3724/SP.J.1006.2013.01331

Abstract ( 1001 )

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Polyploidization is an important mechanism during plant evolution and polyploids are prevalent in the plant kingdom. Compared with their parents, polyploids often have strong growth vigor. Thus, how genes from different species are regulated in polyploid plants is a research area of great interest. Recently, small RNAs were found to be involved in re-establishing gene expression balance during plant polyploidization. In this paper, we presented an up to date overview on cis- and trans-gene regulatory mechanism in plant polyploidization that is mediated by small RNAs, especially by miRNAs and siRNAs. We also provided opinions on future directions in polyploid crop research.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Expression Characteristics of Key Genes in Lignin Pathway among Different Lodging Resistance Lines of Brassica napus L.

HUANG Jie-Heng**,LI Wei**,QU Cun-Min,LIU Lie-Zhao,XU Xin-Fu,WANG Rui,LI Jia-Na*

Acta Agron Sin. 2013, 39(08): 1339-1344. doi:10.3724/SP.J.1006.2013.01339

Abstract ( 947 )

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Lignin is related to not only plant disease resistance but also lodging resistance. The lignin content and six key genes (PAL, 4CL, C4H, CCR1, CCR2, and CAD) expression characteristics of the middle stem were analysed at early flowering stage and podding stage of 15 Brassica napus L. varieties with different lodging resistance level. The results indicated that the lignin content generally increased by 28% from early flowering stage to podding stage, especially by 33.5% in the varieties with stronger lodging resistance. Lignin content was significantly different between the varieties with different lodging resistance levels. The expression of key enzyme genes was remarkably different between two stages, and the expression of genes PAL, 4CL, and CCR1 was remarkably different between the varieties with different lodging resistance levels. The expression of gene PAL was significantly correlated with lignin content at both stages, and the expression of gene 4CL was significantly correlated with that of most other genes. Our results suggested that all the genes studied in the paper could control the lignin synthesis, and PAL and 4CL were the most important genes in lignin pathway.

Overexpression of Elicitor Protein Encoding Gene Hrip1 Improves Tolerance to Drought and Salt Stresses in Arabidopsis

PENG Xue-Cong,YANG Xiu-Fen,QIU De-Wen,ZENG Hong-Mei,GUO Li-Hua,LIU Zheng

Acta Agron Sin. 2013, 39(08): 1345-1351. doi:10.3724/SP.J.1006.2013.01345

Abstract ( 1023 )

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Hrip1 is a novel hypersensitive response-inducing protein secreted by necrotrophic fungus,Alternaria tenuissima. The Arabidopsis thaliana transgenic plants overexpressing Hrip1 showed increased tolerance to drought and salt stresses. Five transformed lines of Arabidopsis were confirmed by PCR, RT-PCR and Western blot analysis. T₄ progenies of transgenic Arabidopsis lines and the wild-type plants were tested. The results showed the seed germination rate and root length of transgenic plants were all significantly higher than those of wild type plants (P<0.05) under stress conditions. The average seed relative germination rate of transgenic Arabidopsis lines was 32.1% and 77.9%, which were 3.72 and 5.61 times higher than those of wild-type plants in the two days incubation with 50 mmol L⁻¹ NaCl and 75 mmol L⁻¹ mannitol, respectively. The average relative root length in transgenic plants was 81.79% and 93.25%, which were 1.53 and 1.34 times of that in wild type plants at 7th day on the medium containing 150 mmol L⁻¹ NaCl and 50 mmol L⁻¹mannitol, respectively. Stress tolerances were improved in the three-week old soil-grown seedlings. Survival rate of transgenic plants and wild type plants was 67 % and 42 % under 250 mmol L⁻¹NaCl stress for 20 days, respectively and 72 % of the transgenic plants and 44 % of wild-type plants were survived at 5th day re-watering after dehydration stress for 25 days. Otherwise, POD and CAT activities were increased in transgenic plants compared with three wild type plants under salt and drought stresses. At 24 h of treatment with 200 mmol L⁻¹ NaCl and 200 mmol L⁻¹ mannitol, the average POD activity in transgenic seedlings was 1.56 and 1.85 times, CAT activity was 1.64 and 1.86 times higher than those in wild plants, respectively. These data indicated thatthe expression of Hrip1 gene positively regulates salt and drought tolerance in transgenic Arabidopsis.

Cloning and Expression Analysis of SbDREB2 Gene from Sorghum bicolor

XIE Deng-Lei,CUI Jiang-Hui,CHANG Jin-Hua

Acta Agron Sin. 2013, 39(08): 1352-1359. doi:10.3724/SP.J.1006.2013.01352

Abstract ( 944 )

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DREBs play important roles in regulating the expression of downstream genes in response to a variety of abiotic stresses. In this paper, a DREB-like gene, named SbDREB2, was assembled by searching sorghum EST and genome databases. The SbDREB2 gene was cloned from salinity-stressed sorghum seedling by RT-PCR. SbDREB2 contains a 789 bp complete open reading frame (ORF) which encodes a peptide of 262 amino acids. The predicted molecular weight and isoelctric point of SbDREB2 are 28.64 kD and 5.52, respectively. There is a 740 bp intron in the DNA sequence of SbDREB2. The amino acids analysis indicated that the predicted protein sequence contained a typical AP2 DNA-binding domain in the 82–145 regions. Multiple sequences alignment revealed that SbDREB2 shared 84% and 69% sequence similarities with Zea mays DREB2A and Oryza sativa DREB1, respectively. Prokaryotic expression vector pET28a-SbDREB2 was established and transformed BL21 (DE3) into E. coli after IPTG induction, showing a successful gene expression. The expression pattern analysis carried out by quantitative real-time PCR indicated that SbDREB2 was constitutively expressed in various tissues of sorghum, and was strongly up-regulated under high salinity, drought and exogenous application of abscisic acid (ABA). However, the expression of SbDREB2 was not affected by low temperature.

Effects of Aspergillus niger phyA2 Transgenic Maize on Utilization of Organic Phosphorus in Soil

HOU Wen-Tong,YANG Li-Ping,CHEN Ru-Mei,ZHANG Shao-Jun

Acta Agron Sin. 2013, 39(08): 1360-1365. doi:10.3724/SP.J.1006.2013.01360

Abstract ( 802 )

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Homozygous phyA2 transgenic maize lines at T9 generation and the corresponding generation of negative control were grown in low-phosphorus (P) soil to investigate the ability of maize plant to acquire P from organic sources. It showed that the soil phosphatase activity increased by 5.17% and 5.48%, the moderately labile organic P decreased by 16.2% and 28.2% respectively in phyA2 transgenic maize rhizosphere, and the P accumulation of transgenic plant increased significantly by 140% and 100% respectively as compared with a control plant line when supplied with phytate as P sources and without P-fertilizer. The plant growth of phyA2 transgenic maize was better improved than that of the negative control plant. These data indicated that we can improve the ability of plant to utilize soil organic P, the plant P accumulation and the plant growth by transferring Aspergillus niger phyA2 gene into maize.

Excavation of Neutral Alleles S_aⁿ, S_bⁿ, and S_cⁿ from the Rice Germplasm Harboring S₅ⁿ Gene

LI Hong-Yan**,WANG Si-Zhe**,SHAHID Muhammad Qasim**,CHEN Zhi-Xiong,WANG Lan,CHEN Feng-Yi,LIU Xiang-Dong*,LU Yong-Gen*

Acta Agron Sin. 2013, 39(08): 1366-1376. doi:10.3724/SP.J.1006.2013.01366

Abstract ( 858 )

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One of the principal barriers in utilization of heterosis between indica and japonica subspecies of Asian cultivated rice is F₁pollen sterility. According to the “specific compatibility gene” theory, there are at least six loci, which cause indica and japonica hybrid pollen sterility. Excavation and utilization of neutral alleles for overcoming F₁ hybrid sterility have great importance in hybrid breeding. Varieties carrying S₅ⁿgene were used to cross with Taichung 65 and its near isogenic lines (NILs) to produce F₁ hybrids with single-locus interaction, double-loci interaction and triple-loci interaction. Pollen fertility and seed setting rate of these hybrids were observed in F₁ to pre-judge the existence of neutral alleles and then F₂generation was genotyped with molecular markers tightly linked to S_a, S_b and S_cloci to verify the presence of S_aⁿ, S_bⁿ and S_cⁿ by detecting segregation ratio. The results showed that two materials (Huibeizi and Madhukar) carried S_aⁿ and S_bⁿ, three materials (Fanhaopi, Biwusheng and YuetaiB) carried S_bⁿ and one material (Jackson) carried S_cⁿ. These materials have wide compatibility and neutral alleles are important germplasm for hybrid breeding and knowing the molecular mechanisms underlying hybrid male sterility.

Virulence and Genetic Diversity of Blumeria graminis f. sp. tritici Collected from Shandong and Hebei Provinces

ZHAO Zi-Hui, HUANG Jiang, LU Ming, WANG Xiao-Ming, WU Long-Fei, WU Xiao-Fei, ZHAO Xin, LI Hong-Jie

Acta Agronomica Sinica. 2013, 39(08): 1377-1385. doi:10.3724/SP.J.1006.2013.01377

Abstract ( 1036 )

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Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is one of the most important diseases that damages wheat (Triticum aestivum L.) production in China. Analysis of virulence structure and effectiveness of resistance genes is important in the control of powdery mildew with host resistance. This study was conducted to test virulence structures of 41 isolates collected from Shandong and Hebei provinces in 2011. The genetic diversity of these isolates was also analyzed using SSR markers. The virulence frequencies of isolates tested ranged from 0.35 (Bg40-2, Yantai, Shandong) to 0.74 (Bg46-1, Pingdu, Shandong). The mean virulence frequency for the isolates from Shandong was not significantly different from that of the isolates from Hebei Province. Except for a few resistance genes such as Pm17, the virulence frequencies of isolates from Shandong and Hebei provinces on most resistance genes were not different. None of the isolates tested was virulent on Pm24 carried by the Chinese landrace Chiyacao. A few isolates were virulent to Pm1c, Pm16, Pm20, PmH, and Mlxbd. Two isolates from Handan and Huanghuang of Hebei Province were virulent on Pm21, but none of the isolates from Shandong Province was virulent on Pm21. The virulence frequencies for Pm5e, Pm6, Pm12, Pm13, Pm17, Pm40, Pm2+6, and Pm5+6 ranged from 0.18 to 0.48. Genes Pm1a, Pm3a, Pm3c, Pm3g, Pm4a, Pm4b, Pm4c, Pm5a, Pm7, Pm8, Pm19, Pm33, Pm43, PmY39, PmPS5A, and PmDR147 had the virulence frequencies over 0.6. Analysis of genetic diversity indicated that the genetic variation of Bgt isolates occurred within the population, and gene flow occurred among isolates. Although some single spore progenies from the same location were clustered together, some were not classified into the same cluster, indicating the variation in their genetic bases. The polymorphism of virulence patterns for various resistance genes was not necessarily consistent with the DNA polymorphism as revealed by SSR markers.

Agronomic Traits and Grain Quality of Chinese Spring–Dasypyrum villosum Translocation Lines T1DL*1VS and T1DS*1VL

DONG Jian,YANG Hua,ZHAO Wan-Chun,LI Xiao-Yan,CHEN Qi-Jiao,GAO Xiang

Acta Agron Sin. 2013, 39(08): 1386-1390. doi:10.3724/SP.J.1006.2013.01386

Abstract ( 836 )

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To understand the effect on agronomic traits and grain processing quality of Chinese Spring (CS)–Dasypyrum villosa compensating Robertsonian translocation lines T1DL?1VS and T1DS?1VL, we conducted a 2-year field trial at Yangling, Shaanxi Province from 2008 to 2011. Some agronomic traits and processing quality characteristics of T1DL?1VS and T1DS?1VL were compared with those of CS, and the high-molecular-weight glutein subunit (HMW-GS) genes of D. villosum were located on chromosome arms using SDS-PAGE method. The heading and maturity dates of both translocation lines were the same, but 1–2 d later than those of CS. Compared to CS, T1DS?1VL had similar other agronomic traits; however, T1DL?1VS showed higher values of spring tillers per plant, 1000-grain weight, and grain weight per plant. Although the seed protein contents of both translocation lines were not significantly different from those of CS, T1DS?1VL exhibited significantly lower Zeleny sedimentation value, developing time, stability, and quality index of farinograph than CS; the values of these quality parameters were significantly higher in T1DL?1VS than in CS. Therefore, T1DS?1VL has a significant negative effect on wheat dough strength, and T1DL?1VS significantly increase gluten strength. HMW-GS gene Glu-V1 of D. villosum was located on both of 1VS and 1VL, but the gene expression level might be higher in T1DL?1VS than in T1DS?1VL.

Cloning and Expression Analysis of GbMFT1 Gene in Gossypium barbadense L.

GU Chao,LI Chao,LI Xiao-Bo,XIAO Xiang-Wen,CUI Bai-Ming,HUANG Xian-Zhong

Acta Agron Sin. 2013, 39(08): 1391-1399. doi:10.3724/SP.J.1006.2013.01391

Abstract ( 931 )

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One MFT (MOTHER OF FT AND TFL1)-like homolog was isolated from Gossypium barbadense L. cv. Xinhai14 through RT-PCR and RACE method, which was designated as GbMFT1 gene. The open reading frame (ORF) of GbMFT1 is 528 bp in length, encoding a putative protein of 175 amino acids. GbMFT1 gene has a phosphatidylethanolamin-binding protein (PEBP) conserved motif. Liking almost all MFT-like proteins, GbMFT1 protein has a conserved proline residue near the C-terminus. Phylogenetic analysis revealed that GbMFT1 showed closer kinship with VvMFT and SP2G, indicating that they belong to the same evolutionary branch. Expression analysis by qRT-PCR indicated that GbMFT1 displayed a much broader expression range, with a maximum expression in petal. GbMFT1 was also expressed in different developmental stages of cotton fibres, especially in the two DPA ovules and nine DPA fibres. Expression analysis by semi-quantitative method indicated that GbMFT1 had a high expression level at the begining of seed germination. There existed no significant difference of expression in germinating seeds treated with different concentrations of ABA, indicating the expression of GbMFT1 is not regulated by ABA. Our results lay a good foundation in studying the function of cotton GbMFT1 gene further.

Cloning, Expression, and Activity Analysis of Ascorbate Peroxidase (APX) Gene from Winter Turnip Rape (Brassica campestris L.)

ZENG Xiu-Cun1,2,SUN Wan-Cang1,*,FANG Yan1,LIU Zi-Gang1,DONG Yun3,SUN Jia4,WU Jun-Yan1,ZHANG Peng-Fei1,SHI Peng-Hui1,KONG De-Jing1,ZHANG Teng-Guo5,HE Li1,ZHAO Cai-Xia1

Acta Agron Sin. 2013, 39(08): 1400-1408. doi:10.3724/SP.J.1006.2013.01400

Abstract ( 994 )

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Ascorbate Peroxidase (APX) is a key enzyme which eliminates oxygen free radicals and increases plant resistance in adverse circumstances. The complete open reading frame of APX gene was cloned from an extremely low temperature (–32℃) resistant winter turnip rape (Brassica campestris L.) cultivar Longyou 7 using the method of reverse transcription PCR (RT-PCR). The primers were designed according to the published APX cDNA sequences. The sequence of APX from B. campestris L. was 753 bp, encoding a protein of 250 amino acid residues with a predicted molecular weight of 27.7 kD and a theoretical pI of 5.58. Bioinformatics analysis showed that the predicted APX protein contained a conserved amino acid sequence corresponding to the plant peroxidase (POD) superfamily. The APX had no signal peptide and was a hydrophilic protein locating in cytoplasm. The prediction of the second structures indicated theAPX was a steady protein with more random coils and α-helices. The expression analysis of APX gene using real time RT-PCR and the activity of APX in response to lower temperature showed that the APX could be induced and the activity of APX could be changed by lower temperature. In conclusion, APX gene might play a role in cold tolerance of the B. campestris L. cultivar Longyou 7.

Genetic Analysis and Gene Mapping of a Rice White Midrib Mutant wpsm

ZHU Xiao-Yan,XU Fang-Fang,SANG Xian-Chun,JIANG Yu-Dong,WANG Nan,ZHANG Chang-Wei,HE Guang-Hua

Acta Agron Sin. 2013, 39(08): 1409-1415. doi:10.3724/SP.J.1006.2013.01409

Abstract ( 966 )

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A white midrib mutant temparily designated as wpsm (white primary and secondary midrib) was screened out in the progeny of an excellent indica restorer line Jinhui 10 with seeds treated by ethyl methane sulfonate (EMS). The wpsm mutant displayed normal leaves during the seedling stage. In the late booting stage, the primary and secondary midrib of the first, second and third leaves of the wpsm mutant showed a bleached appearance, compared with those of the wild type, while mesophyll cells kept normal. This mutational character was maintained to maturity. The photosynthetic pigment of the wpsm was significantly lower than that of the wild type, so were P_n and ETR. Agronomic traits such as plant height, filled grain number per panicle, seed setting rate and 1000-grain weight were significantly decreased when compared with the wild type. Genetic analysis suggested that the mutational characters were controlled by a single recessive nuclear gene. Xinong 1A was crossed with the wpsm, 892 recessive mutants from the F₂ segregation population were used for gene mapping. WPSM was mapped on chromosome 6, between InDel 10 and InDel 4, with physical distance of about 56 kb. This result provides a foundation for WPSM gene cloning by map-based strategy as well as its functional analysis.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Studies on Full Heading and Safe Sowing Date for Different Maturing-type Japonica Rice Cultivars of Jiangsu Province

ZHANG Hong-Xi,ZHANG Zu-Jian,WANG Cai-Lin,YANG Jian-Chang,ZHAO Bu-Hong,QIN De-Rong,CHEN Xin-Hong,WANG Jian-Ping,SUN Ju-Ying,JI Hong-Juan,SONG Yun-Sheng,ZHU Qin-Sen

Acta Agron Sin. 2013, 39(08): 1416-1424. doi:10.3724/SP.J.1006.2013.01416

Abstract ( 877 )

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To know heading dates corresponding to sowing dates of four maturing-type japonica rice cultivars in regions from north to south of Jiangsu Province and to establish the theoretical basis for sowing date arrangement for direct seeding and mechanical transplanting of rice by ascertaining the critical safe sowing dates, we directly seeded five japonica cultivars including Lianjing 4 (mid-maturing and mid-season rice), Huaidao 10 (late-maturing and mid-season rice), Yangjing 4038 (early-maturing and late-season rice), Nanjing 44 (early maturing and late-season rice), and Nanjing 46 (mid-maturing and late-season rice) in Lianyungang (34°83' N), Huai’an (33°34' N), Yangzhou (32°25' N) and Suzhou (31°18' N) at an interval of ten days from May 10 to July 20. A model y = a + b₁x₁+ b₂x₂ was used to fit the virtual sowing dates and heading dates. Based on the results from four experimental locations and five cultivars, we obtained 20 sets of data, and 20 prediction equations with good fitting degrees of which the values of R² ranged from 0.9927 to 0.9998 were produced. On the basis of annually daily average temperatures and corresponding safe full heading dates of japonica rice during past 25 years, the sowing date for safe full heading was deduced by means of iterating repeatedly, then, a set of safe sowing dates with 90% assurance were evaluated, and the application of the safe sowing dates in various locations was finally analyzed. The results showed that, in a wheat-rice double cropping system of Lianyungang, the earliest sowing or transplanting date was June 15, which was suitable for mid-maturing and mid-season japonica rice cultivars with a safe sowing date of June 21 for direct-seeding; but other maturing-type varieties should have earlier sowing dates and could not be used for direct-seeding. In the south of Huai’an with a rice-wheat cropping system, the earliest date for sowing or transplanting was about June 12, and the safe sowing date was July 4 for mid-maturing and mid-season cultivars and June 22 for late-maturing and mid-season cultivars, and these cultivars could be used for direct-seeding. The safe sowing date was June 17 or 18 for early-maturing and late-season japonica rice cultivars, with a risk of direct-seeding because of a short growing period; the sowing date for safe full-heading of mid-maturing and late-season japonica rice cultivars was June 8, and such cultivars could not be used for direct-seeding. The earliest sowing or transplanting date in the south of central Jiangsu was June 8–11, and the safe sowing date was July 12, July 3, and June 25–28, respectively, for mid-maturing and mid-season, late-maturing and mid-season, and early-maturing and late-season cultivars, and these cultivars could be used for direct-seeding in this district; the safe sowing date of a mid-maturing and late-season cultivar was June 11, and this type of cultivars could not be used for direct-seeding owing to a too short growing period. In the south of Jiangsu, the earliest sowing or transplanting date was June 5, and the safe sowing date was July 18, July 13, July 9–10, and July 3, respectively, for the above four types of cultivars, and all cultivars could be used for direct-seeding if only considering a safe full-heading stage. However, the grain yield could not be high for mid-season cultivars with direct-seeding because they had short growing period.

Identification Method of Drought Tolerance and Association Mapping for Sesame (Sesamum indicum L.)

LI Dong-Hua,LIU Wen-Ping,ZHANG Yan-Xin,WANG Lin-Hai,WEI Wen-Liang,GAO Yuan,DING Xia,WANG Lei,ZHANG Xiu-Rong

Acta Agron Sin. 2013, 39(08): 1425-1433. doi:10.3724/SP.J.1006.2013.01425

Abstract ( 1045 )

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This research aims at understanding the drought tolerance of sesame germplasm and getting related molecular markers. Ten sesame varieties with different seed coat colors from separate origins were treated with PEG 6000 with different concentrations, and the relative shoot length, relative fresh weight, relative seedling rate and the relative vigor index of the ten sesame varieties were investigated and analyses. The result showed 15% PEG6000 was proper for testing sesame drought tolerance. A comprehensive analysis based on principal component, regression equation and correlation showed that the relative seedling rate could be used as a key indicator to identify drought tolerance of sesame at germination stage. Using the method above, drought tolerance of 216 core collections during germination period was studied, the drought tolerance coefficients of sprout percentage were from 12.15% to 93.52%, the average was 60.74%, the coefficient of variation was 25.22, sprout abundant variation and accordant with normal distribution; together with marker screening, 30 loci were significantly (P<0.05) associated with sesame drought tolerance at germination stage, explaining the phenotypic variation from 1.99% to 4.96%, with an average of 2.84%. So the relative seedling rate is the most suitable and most convenient drought tolerance index, which is suitable for drought tolerance identification of sesame resources.

Effect of Planting Methods on Differentiation and Retrogression of Branches and Spikelets of Hybrid Rice Cultivar

LIU Li,LEI Xiao-Long,WANG Li,DENG Fei,LIU Dai-Yin,REN Wan-Jun

Acta Agron Sin. 2013, 39(08): 1434-1444. doi:10.3724/SP.J.1006.2013.01434

Abstract ( 786 )

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In order to explore the characteristics in spikelets formation of hybrid rice with mechanical sowing and transplanting, the effects of planting method and seedling number per hill on differentiation and retrogression of branches and spikelets were studied using F you 498 in the field experiments. The results showed that the number of differentiated and survived branches in mechanical direct seeding and mechanical transplanting was significantly higher than that in artificial transplanting, however, the survived spikelets in mechanical direct seeding and mechanical transplanting were significantly lower than those in artificial transplanting. The number of differentiated and survived primary branches and spikelets were higher in mechanical direct seeding than in artificial transplanting, while those in mechanical transplanting were the lowest. The numbers of differentiated and retrograded secondary branches in mechanical direct seeding and mechanical transplanting were significantly higher than those in artificial transplanting. However, the number of differentiated secondary spikelets was higher in mechanical transplanting than in artificial transplanting, and was the lowest in mechanical direct seeding. The number of differentiated and retrograded primary and secondary branches and spikelets were significantly lower in high seedling number per hill than in low seedling number per hill. The number differences of differentiated and retrograded secondary branches in all of the planting methods presented mainly on the basal panicle, the number of survived secondary branches showed an increased and then decreased tendency on different primary branches, which was mainly related to the serious secondary branches retrogression. The number of survived primary spikelets decreased from panicle bottom to top, the number of survived secondary spikelets was related to the ability of spikelets differentiation. Therefore, for the effect of interaction between planting methods and seedling number per hill, the low seedling number per hill showed the combined with mechanical transplanting and artificial transplanting, while the high seedling number per hill showed the combined with mechanical direct seeding.

Effect of Biochar on Root Morphological and Physiological Characteristics and Yield in Rice

ZHANG Wei-Ming,MENG Jun,WANG Jia-Yu,FAN Shu-Xiu,CHEN Wen-Fu

Acta Agron Sin. 2013, 39(08): 1445-1451. doi:10.3724/SP.J.1006.2013.01445

Abstract ( 1247 )

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In order to clear the effects of biochar on rice root and yield and in further proved the value of biochar application on rice production, effects of biochar on root growth, morphological and physiological characteristics of super japonica rice were studied in a pot experiment. The results showed that biochar application in soil could increase the main root length, volume and fresh weight of rice roots during the earlier growing stage, enlarge root total absorption area and active absorption area. Biochar delayed root senescence and maintained a higher root activity to some extent in the later growth stage. Biochar promoted the root physiological activities, showing a higher bleeding rate, larger root activity and higher soluble protein content, as comparison with the control in the whole growth stage. The yield was 25.28% more than the control with an improved rice panicle number per hill, grain number per panicle and seed setting rate. The highest yield with a 33.21% increase was achived in the treatment with 20 g biochar per kilogram of dry soil. Biochar plays a promoting role in optimizing morphological and physiological characteristics of rice roots.

Hormone Contents in Kernels at Different Positions on an Ear and Their Relationship with Endosperm Development and Kernel Filling in Maize

XU Yun-Ji,GU Dao-Jian,ZHANG Bo-Bo,ZHANG Hao,WANG Zhi-Qin,YANG Jian-Chang

Acta Agron Sin. 2013, 39(08): 1452-1461. doi:10.3724/SP.J.1006.2013.01452

Abstract ( 1068 )

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Kernels at the upper position of a maize ear usually show poorer filling and lower weight in contrast to those at the basal position. The mechanism has not been understood. The experiments were conducted using a maize cultivar Denghai 11, grown in both field and greenhouse conditions, to determine number of endosperm cells, kernel filling rate, and contents of zeatin (Z) + zeatin riboside (ZR), indole-3-acetic acid (IAA), abscisic acid (ABA), and gibberellin-3 (GA₃) in the kernels at different positions on an ear from silking to maturity. The results indicated that the maximum number of endosperm cells, maximum division rate of endosperm cells,mean endosperm cell division rate,maximumkernel filling rate, mean kernel filling rate and 100-kernel weight for kernels showed an order of basal position > middle position> upper position. During the active endosperm development and the active kernel filling period, contents of Z+ZR, IAA and ABA in kernels were the greatest at the basal position, the mediate at the middle position, and the least at the upper position on an ear. The two experiments exhibited similar results. The endosperm cell division rate and kernel filling rate were very significantly and positively correlated with contents of Z+ZR, IAA, and ABA in kernels, whereas significantly and negatively correlated with content of GA₃. The results suggested that a lower kernel weight at the upper position on a maize ear is mainly due to a smaller division rate of endosperm cells, leading to less number of endosperm cells, which is closely associated with lower contents of Z+ZR, IAA, and ABA, as well as higher content of GA₃ in the kernels during kernel filling.

Effects of Root Excision and Water Stress on Root Hydraulics and TaPIPs Expression in Wheat Seedlings

WANG Wei-Feng,YANG Xiao-Qing,ZHANG Sui-Qi,SHAN Lun

Acta Agron Sin. 2013, 39(08): 1462-1468. doi:10.3724/SP.J.1006.2013.01462

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Root excision can break water balance between the water uptake by roots and the transpriation in shoots and induce hydraulic responses of roots, which is helpful to explain how hydrostatic gradient regulates root hydraulic traits. To explore the regulation mechanisms of root hydraulics to the broken whole plant water balance by root excision and water stress, we investigated the changes of individual root (Lp_root) and cortex cell (Lp_cell) hydraulic conductivities of wheat (Triticum aestivum, cv. Changwu 134) after root excision and water stress with root and cell pressure probes. The transcription levels of TaPIP1;2 and TaPIP2;5 were also measured with Quantitative Real-time PCR. Root excision or water stress treatment significantly reduced the leaf transpiration rate and stomatal conductance of wheat seedlings, but the Lp_root or Lp_cell of the remained roots had no significant changes. The transpiration rate, stomatal conductance, leaf water potential, Lp_root, and Lp_cell of root-excised plants were significantly higher than those of plants under water stress. However, these parameters of plants with both root excision and water stress were significantly lower than those with a single treatment or the control. Irrespectively of root excision or water stress, Lp_cell had a significantly positive correlation with Lp_root (R²= 0.97, P < 0.05), which suggested the accordance in root water uptake ability at cell level and individual root level. Root excision significantly up-regulated the relative mRNA contents of TaPIP1;2 and TaPIP2;5 in wheat roots, but water stress had an effect of down-regulation. The relative mRNA contents of TaPIP1;2 and TaPIP2;5 of root excised and water stressed seedlings were the lowest in the four treatments. These results may suggest that root excision could reduce the tolerance of wheat seedling to the following water stress; cortex cell hydraulic conductivity could be accordant with individual root hydraulic conductivity during wheat root hydraulics regulation; and TaPIP1;2 and TaPIP2;5 may be involved in regulating root hydraulics of wheat.

Estimation of Severity Level of Wheat Powdery Mildew Based on Canopy Spectral Reflectance

FENG Wei,WANG Xiao-Yu,SONG Xiao,HE Li,WANG Yong-Hua,GUO Tian-Cai

Acta Agron Sin. 2013, 39(08): 1469-1477. doi:10.3724/SP.J.1006.2013.01469

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Understanding spectrum characteristics and sensitive bands of wheat infected by Blumeria graminis f. sp. tritici (Bgt) and estimatiing the disease severity will provide a basis for monitoring and subsequently accurately controlling powdery mildew in wheat planted in large scales using aerial remote sensing. Canopy reflectance of winter wheat infected by artificial inoculationof Bgt with different severity levels was measured in disease nursery, field, and pot experiments, and the severity levels in different growth phases were also investigated at the same time. The results indicated that spectrum reflectance increased significantly in visible light region (350–710 nm) with the increase of disease severity level, and the light region between 580 nm to 710 nm was the sensitive bands to wheat powdery mildew, which varied greatly in near-infrared region (710–1100 nm) across treatments with different disease severity levels. However, the correlation between spectrum reflectance and traditional disease index (DI) was low. When the conventionalDI was replaced by modified DI, the correlation was improved significantly. An integrated linear regression equation of disease severity level to red edge width (Lwidth) described the dynamic pattern of disease severity level in wheat, with R² of 0.811 and relative error (RE) of 17.7%. Besides, correlation coefficients between spectral parameters (mND705, SIPI, CTR2, and TSAVI) and modified DI were higher than 0.6. No common integrated regression equation could be establishhed due to poor compatibility among experiments. The relative spectral indices (ΔMSAVI and ΔmND705) exhibited high correlations (R² > 0.76) with the disease sensitive level, with RE values of 18.4% and 19.4%, respectively. The results suggested that the models with sensitive spectral indices could retrieve and forecast the disease severity level accurately in a large area.

Effects of Nitrogen Application on Accumulation and Distribution of Nitrogen, Phosphorus, and Potassium of Summer Maize under Super-High Yield Conditions

JING Li-Quan,ZHAO Fu-Cheng,WANG De-Cheng,YUAN Jian-Hua,LU Da-Lei,LU Wei-Ping

Acta Agron Sin. 2013, 39(08): 1478-1490. doi:10.3724/SP.J.1006.2013.01478

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Establishing a high quality population is an important prerequisite to achieve high grain yield. Nitrogen (N) application is one of the most important practices in maize (Zea mays L.) production and plays a critical role in regulating population quality. To explore the effects of N application on accumulation and distribution of N, phosphorus (P), and potassium (K) of summer maize under the conditions of super-high yield (≥13 500 kg ha^-1), we planted two maize cultivars (Suyu 20 and Xundan 20), wtih different N application levels across three years, and the highest grain yield reached to14 753 kg ha^-1. The results showed that in the growth process, N, P, K accumulation increased gradually in the plants and grains of Suyu 20 and Xundan 20, and showed a curvilinear change in leaves, stems and sheatheswith a peak value at trumpeting stage and anthesis stage, respectively. The increasing of N accumulation and transfer rate in leaves at filling stage promoted the N and P accumulation of grain at mature stage, leading to super-high yield groups. In Suyu 20, yield, grain production per kg N, N agronomy efficiency, N utilization efficiency, N, P, K content in leaves, stems and sheathes were the highest at 450 kg ha^-1 which were 14 753 kg ha^-1, 44.0 kg, 19.24%, 38.63%, 335.4 kg ha^-1, 178.2 kg ha^-1, 230.7 kg ha^-1, respectively. But N, P, K accumulation and yield decreased when N application level was too high or too low. According to the regression equations between N application rate and yield of two varieties, for Xundan 20 the optimal N amount was 457.0 kg ha^-1, the range of optimum N was 418.5-495.4 kg ha^-1, 418.3-495.7 kg ha^-1 for super-high yield groups; and for Xundan 20, the optimal N was 452.7 kg ha^-1, the range of optimum N was 410.8-494.6 kg ha^-1

Effects of Nitrogen, Phosphorus, Potassium, and Boron Fertilizers on Winter Oilseed Rape (Brassica napus L.) Direct-sown in the Yangtze River Basin

WANG Yin,LU Jian-Wei,LI Xiao-Kun,REN Tao,CONG Ri-Huan,ZHAN Li-Ping

Acta Agron Sin. 2013, 39(08): 1491-1500. doi:10.3724/SP.J.1006.2013.01491

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Oilseed rape is the dominant oil crop in China. Direct-sowing method has the great significance in increasing winter oilseed rape yield and guaranteeing national edible oil security. Field trials were conducted at 36 sites in the Yangtze River Basin to determine the fertilization effects of nitrogen (N), phosphorus (P), potassium (K), and boron (B) on seed yield, economic benefit, nutrient uptake and fertilizers efficiencies of direct-sown winter oilseed rape. Then we compared the differences between recommended fertilization and farmers’ fertilizer practice (FFP), and between direct-sowing and transplanting cultivations. The objective was to discuss and offer appropriate suggestions of fertilization management for direct-sown winter oilseed rape in China. Combination application of N, P, K, and B fertilizers (NPKB) resulted in the greatest seed yield (2001 kg ha^–1) and economic income (8205 Yuan ha^–1), which were significantly higher than those of FFP treatment. The effects of different fertilizers on oilseed rape as N >P>B＞K. Nutrient uptakes were obviously improved in NPKB treatment, with the average accumulation of 104.2 kg N ha^–1, 20.4 kg P ha^–1,and 160.2 kg K ha^–1. In addition, the apparent recovery efficiency of N, P, and K fertilizers was 35.8%, 22.3%, and 45.9% in NPKB treatment, respectively, which was considerably higher than that in FFP treatment (20.8%, 7.2%, and 28.0%). Overall, our results demonstrated that suitable fertilization management (combination application of N, P, K, and B fertilizers) would be recommended in the production of direct-sown oilseed rape at the current stage. Both fertilization time and ratio should be adjusted to coordinate with oilseed rape growth and nutrient uptake regulation under direct-sowing cultivation.

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Construction and Application of a Reference Plasmid Molecule Suitable for phyA2 of Phytase Transgenic Maize

ZHANG Guang-Yuan,SUN Hong-Wei,LI Fan,YANG Shu-Ke,LU Xing-Bo,ZHAO Lei

Acta Agron Sin. 2013, 39(08): 1501-1506. doi:10.3724/SP.J.1006.2013.01501

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Plasmid molecule based reference material has been shown to be a good alternative as the calibrator for genetically modified organisms (GMOs) identification and quantification. In this study, primers and probe for qualitative and quantitative PCR detection for phytase transgenic maize were designed, and a flexible plasmid pPZ containing phyA2 (243 bp) and zSSIIb (178 bp) sequences, was developed. Primers and plasmid were specifically tested through qualitative PCRs. Results showed that the primers and pPZ plasmid were very specific for phytase transgenic maize since there were no other PCR products amplified using different GMOs and primers except the specific main bands. Four different levels of genetically modified (GM) matrix samples (3.0%, 1.0%, 0.5%, and 0.1%) were detected by real-time PCR when plasmid pPZ and phytase transgenic maize genomic DNA were used as quantification standards, respectively. t-test showed the slop, linearity (R²) and quantification of the two standards for phyA2 and zSSIIb were not significantly different. The results indicated that the pPZ plasmid can be used as standard for phytase transgenic maize detection.

Effects of Different Planting Densities on Sugar Accumulation and Activities of Sucrose Synthase and Sucrose Phosphate Synthase of Sweet Sorghum bicolor (L.) Moench

CHEN Wei-Wei,Zaituniguli?KUERBAN,TU Zhen-Dong,YE Kai

Acta Agron Sin. 2013, 39(08): 1507-1513. doi:10.3724/SP.J.1006.2013.01507

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