Table of Content

12 September 2010, Volume 36 Issue 09

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REVIEW

Crop Molecular Breeding in China:Current Status and Perspectives

LI Yu, WANG Jian-Kang, QIU Li-Juan, MA You-Zhi, LI Xin-Hai, WAN Jian-Min

Acta Agron Sin. 2010, 36(09):  1425-1430.  doi:10.3724/SP.J.1006.2010.01425

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With some technological breakthroughs such as sequencing and microarray in the recent years, genomics, transcriptomics, proteomics, metalomics and phenomics have made a great progress in the world. Theories and technologies of crop breeding have also been revolutionarized considerably. Traditional crop breeding is based on phenotypic selection, which is often called “empirical breeding” with poor predictability, long breeding cycle and low breeding efficiency. Modern crop molecular breeding including marker-assisted breeding, transgenic breeding and molecular design breeding has become an important direction in the field of plant breeding. It is based on the combination of genotypic selection and phenotypic selection and thus target genes/alleles can be directly selected and pyramided. Therefore, the efficiency of molecular breeding can be improved and the breeding duration can be shortened. The paper defines the concept of mole

Discussion on the Aspects of High-Yielding Breeding in Rice

GU Ming-Hong

Acta Agron Sin. 2010, 36(09):  1431-1439.  doi:10.3724/SP.J.1006.2010.01431

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In last 60 years, great success on rice production was achieved via improved cultivation technique, utilization of chemical fertilizer, variety improvement and so on. In the aspect related to development of high-yielding rice varieties, the successes can be summarized as three points: (1) development of semi-dwarf varieties of indica rice with the gene of sd-1 in late 1950s and early 1960s; (2) development of elect-panicle varieties of japonica rice with the gene of qEP9-1 in 1960s; (3) development of hybrid rice with the gene of CMS of WA, BT, HL, etc. in 1970s. Generally speaking, rice yield is composed of three components: the panicle number of unit area, the filled grain number per panicle and the grain size (usually measured by the weight of 1000 rice grains). In order to develop super-high-yielding-variety in rice, the key point is to explore new resources of the genes related to plant type, tillering ability, panicle size, grain size, insect and disease resistance, grain filling ability, and so on. Such gene resources usually can be obtained from different subspecies, i.e. indica and japonica. Some important genes also can be obtained from other species for which biological approach is essential including gene cloning and development of molecular makers for the genes. In recent years, lots of target genes related to the characteristics mentioned above have been cloned, such as Sd1, Gn1a, Ga20x-2, Gs3, Bt, EPSPS, qPEP9-1, On the other side, new breeding techniques such as transgenic approach and molecular assisted selection (MAS) to pyramid target genes (or gene combinations) have need to be accepted and to be joined with conventional breeding techniques. With reviewing the development for high-yielding variety achieved in last century, several points need to be noticed and discussed: (1) Tillering. The tillering ability of rice plays an important role in regulating population density related to the efficiency of photosynthesis . The panicle number of unit area also relates to the tillering ability of the varieties. For high and the stabe yield, medium or even higher than medium tillering ability is necessary for the elite varieties. (2) Panicle size is usually measured by the number of filled grains per panicle. Extensive variation on panicle size can be found in different rice varieties. The heterosis of hybrid rice mainly shows the enlargement of panicle size. For developing high-yielding varieties, more attention needs to be paid on enlarging the panicle size. (3) Grain size: Grain size is one of the most important factors influencing yield potential in rice. The range of grain size measured by 1000-grain weight is 23–29 g in commercial varieties and 15–70 g in rice germplasm. In general, the larger the grain size, the poorer the grain quality. From the point of view of balance between grain yield and grain quality, a medium-large grain size is most favorite for high-yielding varieties.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Osmotic Stress Tolerance Improvement of Arabidopsis Plants Ectopically Expressing Peanut AhNCED1 Gene

WAN Xiao-Rong, MO Ai-Qiong, GUO Xiao-Jian, YANG Miao-Xian, YU Shi-Yuan, CAO Jin-Ping

Acta Agron Sin. 2010, 36(09):  1440-1449.  doi:10.3724/SP.J.1006.2010.01440

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The phytohormone abscisic acid (ABA) is a key regulator of seed development, root growth, stomatal aperture in higher plants and it is also involved in adaptation of plants to various stresses. The oxidative cleavage of cis-epoxycarotenoids catalyzed by nine-cis-epoxycarotenoid dioxygenase (NCED) is considered to be the rate-limiting step in ABA biosynthesis in higher plants. The AhNCED1 gene plays a vital role in the regulation of ABA biosynthesis in peanut plants in response to drought stress. Two binary vectors, p35S::ORF and pAtNCED3p::ORF, were established which harbored the AhNCED1 gene, respectively, driven by the CaMV 35S promoter originated from pCAMBIA1301 and the AtNCED3 gene promoter from wild type Arabidopsis. Wild type and 129B08/nced3 mutant Arabidopsis plants were separately transformed with Agrobacterium harboring p35S::ORF or pAtNCED3p::ORF vectors, generating 35S::ORF-WT and A3p::ORF-B08 transgenic plants, respectively, after hygromycin screening and PCR detection. The stable expression of AhNCED1 gene in Arabidopsis plants was confirmed by duplex RT-PCR performance. Wild type, 129B08/nced3 mutant and transgenic Arabidopsis plants were subsequently tested for sensitivity to exogenous ABA and tolerance to osmotic stress. The results showed that the ABA sensitivity of 129B08/nced3 mutant declined, and that of Arabidopsis plants ectopically expressing the AhNCED1 gene increased. Under sorbitol stress, the relative germination rate of 129B08/nced3 mutant seeds was far lower than that of wild type seeds; however, the relative germination rate of A3p::ORF-B08 transgenic seeds was close to that of wild type seeds, significantly higher than that of 129B08/nced3 mutant seeds. The relative germination rate of 35S::ORF-WT transgenic seeds was higher than that of wild type seeds at the treatment of 300 mmol L^–1 sorbitol. Under 300 mmol L^–1 sorbitol stress, leaf of 129B08/nced3 mutant plants was highly chlorotic, and root formation and seedling growth were severely inhibited. In contrast, at this concentration of sorbitol, leaf of A3p::ORF-B08 transgenic seedlings was only slightly chlorotic, just similar to those of wild-type plants; the growth of 35S::ORF-WT transgenic seedlings was nearly not affected. Germination assay and phenotypic evaluation revealed that 129B08/nced3 mutant was hypersensitive to the nonionic osmotic stress induced by sorbitol, and that ectopic expression of peanut AhNCED1 gene reverted the hypersensitivity of 129B08/nced3 mutant Arabidopsis to sorbitol and conferred enhanced osmotic stress tolerance of transgenic Arabidopsis plants. These observations and an improved understanding of the roles of AhNCED1 gene in stresses adaptation could provide the basis for engineering greater stress tolerance in crops.

Genetic Differences in Homoeologous Group 1 of Seven Types of Winter Wheat Aimengniu

CUI Fa,Chun-Hua, BAO Yi-Guang, ZONG Hao, WANG Yu-Hai, WANG Qiang-Zhuan, DU Bin, MA Hang-Yuan, WANG Hong-Gang

Acta Agron Sin. 2010, 36(09):  1450-1456.  doi:10.3724/SP.J.1006.2010.01450

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Aimengniu (Hereafter AMN), cultivated by Shandong Agricultural University, is a renowned Chinese winter wheat germplasm. Knowing better its genetic component is of great value and necessity for its in-depth utilization and study. Purpose of this study is to reveal the genetic differences in detail among seven AMN-derived types. Both molecular markers and genomic in situ hybridization were used to identify translocation between 1B and 1R in seven AMN-derived types. PCR results of primers specific for 1R and 1B detected the presence of both 1RS and 1BL chromatin and absence of 1BS and 1RL in AMNII and AMNIV to VII, while AMNI and AMNIII contained common 1B chromatin. Genomic in situ hybridization confirmed the replacement of chromosome arm 1BS by 1RS in AMNII and AMNIV to VII, and a typical common wheat karyotype was contained in AMNI and AMNIII. In addition, genetic differences among seven AMN-derived types in homoeologous group 1 were detected by 138 polymorphic markers, and genotypic information for each and every one of seven AMN-derived types were represented. Specific segments of AMNV were detected by 3 markers, Xwmc336-Xmag1884 (1A)and Xgwm124 (1B), originating from Neuzucht and Aifeng3 respectively. The results above revealed that genetic differences exist among seven sister lines of germplasm AMN in homoeologous group 1, which will facilitate its further utilization and study.

Detection of Consensus Genomic Region of QTLs Relevant to Drought-Tolerance in Maize by QTL Meta-Analysis and Bioinformatics Approach

LI Wen-Juan, LIU Zhi-Zhai, SHI Yun-Su, SONG Yan-Chun, WANG Tian-Yu, XU Chen-Wu, LI Yu

Acta Agron Sin. 2010, 36(09):  1457-1467.  doi:10.3724/SP.J.1006.2010.01457

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Mapping consensus genomic regions for drought-tolerance is of great importance in the molecular breeding of maize. The present research integrated informations of the published QTLs relevant to drought-tolerance mapped in the environment of water stress. On the basis of the high-density linkage map of IBM2 2008 Neighbors, a total of 79 Meta-QTLs (MQTLs) were screened out through the methods of “overview” and meta-analysis, and the bioinformatic analysis indicated that 43 of these MQTLs (54.43%) contained the information of genes conferring drought tolerance. By integrating the genetic map and the physical map of maize via Genome Brower in maize genome database (http://www.maizegdb.org/), we estimated the physical map distance of MQTLs and analyzed the function of these candidate drought tolerance-related genomic regions based on the maize genome sequence information from the maize sequence database (http://www.maizesequence.org/). The results showed that these regions contained abundant sequences of transcription factors of MYB, bZIP and DREB, and a number of functional genes of LEA family.

Genetic Analysis in Terms of Major-Minor Locus Group Constitutions of Yield in Hybrid Soybean

YANG Jia-Yin, HE Jian-Bo, GUAN Rong-Zhan, YANG Shou-Ping, GAI Jun-Yi

Acta Agron Sin. 2010, 36(09):  1468-1475.  doi:10.3724/SP.J.1006.2010.01468

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The analysis of major-minor locus groups of diallel crosses based on major gene plus polygene mixed inheritance model provides a way to explore the genetic structure of hybrids among a group of materials. Eight soybean parental materials, seven from Huang-Huai region in China and one from the US with maturity group II–IV were used to develop a set of 36 diallel crosses (including 28 F₁ crosses and eight parents) according to the Griffing II pattern. The materials were tested in 2003-2005. From the analysis of major-minor locus groups of the 36 materials, the results showed that six major locus groups plus minor locus groups were detected to explain 75.98% and 10.81% of the phenotypic yield variation, respectively. Which indicated that major locus groups were the major source of genetic variation among the materials with their additive effects (a_J) of 140.10, 259.65, 1.95, 151.35, –32.70, and 45.00 kg ha^–1 and dominance effects (d_J) of 177.15, 314.25, 105.75, 75.90, 242.85, and 171.00 kg ha^–1, respectively, while the minor locus groups were a supplement source in the genetic system. The genetic constitutions of the hybrids were composed of heterozygous dominance effects of major locus groups, homozygous additive effects of major locus groups, heterozygous dominance effects of minor locus groups and homozygous additive effects of minor locus groups, with their relative importance in a descending order. The dissection of the relative importance of the genetic effects of major-minor locus groups helps to explain the genetic characteristics of the hybrids among the parents and provides the genetic basis for further mining the genetic potential of parental materials in the improvement of hybrids.

Identification, Inheritance and QTL Mapping of Root and Shoot Traits in Soybean Variety PI471938 with Tolerance to Wilting

LV Cai-Xia, Guo-Jian-Qiu, WANG Ying, LENG Jian-Tian, YANG Guang-Ming, HOU Wen-Sheng, WU Cun-Xiang, HAN Tian-Fu

Acta Agron Sin. 2010, 36(09):  1476-1483.  doi:10.3724/SP.J.1006.2010.01476

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PI471938, introduced from the US, is a soybean [Glycine max (L.) Merr.] variety with tolerance to wilting. In order to know and use this germplasm, the shoot and root traits of PI471938 and two other varieties (Dare and Fengshouhuang) were investigated under either routine irrigation or drought stress conditions in this study. The crosses were made and segregating populations were analyzed for the inheritance of root and shoot traits by using the major gene and polygene mixed inheritance models. The results showed that the dry root weight, root volume and tap root length of PI471938 were significantly higher than those of Dare and Fengshouhuang under both routine irrigation and drought stress conditions, indicating that large root system especially the deep rooting is one of the major reasons for PI471938 to be tolerant to wilting. Both plant height and shoot dry weight of the parents and progenies were positively correlated with root dry weight and volume, which made it possible to use these shoot traits to indirectly select the root traits. In the F₂ population of the cross Dare×PI416937, root dry weight was found to be mainly controlled by minor-effect polygenes under both routine irrigation and drought stress conditions. The root volume was controlled by polygenes under routine irrigation but by two pairs of additive-dominance-epistasis major genes plus additive-dominance polygenes under drought stress, and the heritability of major genes was as high as 54.63%. Under drought stress, the root dry weight and root volume in the segregating populations of the cross Fengshouhuang×PI471938 were mainly controlled by polygenes. By using the F₂ population derived from Dare × PI471938 grown under drought condition, SSR mapping was conducted and five major-effect QTLs conferring the plant height, root dry weight, shoot/root ratio and tap root length were located on three linkage groups, which could explain 16.07%–38.44% of the total phenotypic variation.

Construction of ihpRNA Expression Vectorof MsLEA3-1 Gene from Medicago sativa L. and Genetic Transformation in Tobacco

BAI Yong-Qin, KANG Jun-Mei, SUN Yan, YANG Qing-Chuan, LI Yan

Acta Agron Sin. 2010, 36(09):  1484-1489.  doi:10.3724/SP.J.1006.2010.01484

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During long-term evolution, plant has developed various physiological functions and bio-chemical mechanisms to respond the diverse stresses in different environments. Plant cell accumulates a series of proteins to reduce cell dehydration in the period of water shortage, of all proteins, late embriogenesis abundant LEA protein has been paid attention, which is one of the hot topics in plant stress physiology. In the paper, an RNAi expression vector harboring MsLEA3-1 gene fragment from Medicago sativa L. was constructed. On the basis of the sequence of Medicago sativa LEA protein (MsLEA3-1) gene (GenBank accession number: EU665182), two pairs of specific primers containing different enzyme sites were designed. With the template of PMD-LEA plasmid constructed, positive-sense strand and antisense strand were obtained, which were separately inserted into the expression vector pART27. The RNAi vector pART-F-R containing a hairpin structure was confirmed by the digestion of restriction enzymes. pART-F-R was transformed into tobacco by Agrobacterium mediated transformation system. PCR testing showed that 16 transgenic plants were obtained.

Screening Wheat cultivars with Genetic Similarity Using Molecular Markers

WANG Li-Xin, LI Hong-Bo, LIAO Qin, QIU Jun, CHANG Li-Fang, LIU Li-Hua, REN Li-Ping, GAO Xin-Huan, ZHAO Chang-Ping

Acta Agron Sin. 2010, 36(09):  1490-1497.  doi:10.3724/SP.J.1006.2010.01490

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Cultivars with similar traits are often found in the national winter wheat (Triticum aestivum L.) regional trials. Molecular markers have been introduced to identify such cultivars efficiently and accurately in screening wheat cultivars with genetic similarity. In this study, 681 wheat cultivars and lines were assessed using 105 molecular markers, including 63 genome-SSRs, 21 EST-SSRs, and 21 AFLP-SCARs. These markers were classified into core primer (21 pairs), first-grade standby primer (29 pairs), and second-grade standby primer (55 pairs). The 681 cultivars and lines consisted of 134 released cultivars and 547 lines evaluated in the national winter wheat regional trials from 2005 to 2009. Cultivars were primarily screened with the core primers, and those with similar fingerprint in 19-21 loci were further tested with the first-grade standby primers, and only the confirmed similar cultivars (GS > 0.90) were conduced the final detection by the second-grade standby primers. Finally, the cultivars with total GS value (at least 100 loci) higher than 0.95 were considered as similar ones. These similar cultivars were continuously identified on the basis of main agronomic traits. The results showed that 95% of the similar cultivars detected by molecular markers had identical or highly similar agronomic traits, and only two pairs of cultivars with GS > 0.95 had distinct performances in agronomic traits. Thus, the laboratory identification had the accordance with the field test by 95%, suggesting that these molecular markers are effective in bulk screening similar cultivars in wheat regional trials.

QTL Analysis of Fatty acids Contents in Soybean

MIAO Xin-Fen, ZHU Ming-Xi, XU Wen-Ping, DING Jun-Jie, YU Feng-Yao, YU Yong-Mei, DU Sheng-Wei, LIU Chun-Yan, CHEN Qiang-Shan, HU Guo-Hua

Acta Agron Sin. 2010, 36(09):  1498-1505.  doi:10.3724/SP.J.1006.2010.01498

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Soybean, Glycine max (L.) Merr., is one of the main plant oil sources. Most researches have focused on the improvement of oil content. However, improving fatty acid composition is the main aspect of soybean breeding now. This study aimed at mapping QTLs conferring fatty acids contents in soybean on the genetic map which had been constructed in our lab to provide a reference of soybean oil quality breeding. Five kinds of fatty acid contents of 154 F₁₄ and F₁₅ lines devisedqSt-B1-1, qSt-B1-2, qSt-D1a-1 and qSt-C2-1;three for related with oleic acid content, i.e. qOle-B2-1, qOle-G-1, and qOle-H-1; two for related with linoleic acid content, i.e. qLin-C2-1 and qLin-H-1, and four for linolenic acid content, i.e. qLino-B1-1,qLino-C2-1, qLino-D1b-1, and qLino-J-1. These stable QTLs pave a way for specific fatty acid contents breeding by marker-assisted selection. The number of main-effect QTLs with large effect conferring the contents of fatty acids appeared not as many as expected, it may also subject to a number of the micro-effect genes which failed to detect. from a cross of Charleston (♀) × Dongnong 594 (♂) were measured by GC at three locations in two years. The QTLs of fatty acids contents were analyzed with method of composite interval mapping (CIM) by Win QTL Cartographer 2.5. In total, 47 related QTLs distributed on the 13 linkage groups were obtained. Seventeen QTLs were detected in different years or different sites, including two for palmitic acid content, i.e. qPal-C2-2 and qPal-A1-1; four for stearic acid content, i.e.

Genetic Analysis and Gene Mapping of a Long Empty Glumes Mutant in Rice (Oryza sativa L.)

CHEN Dai-Bo, ZHAN Xiao-Ding, WU Chao, SHEN Xi-Hong, WU Wei-Ming, GAO Zhi-Qiang, CHENG Shi-Hua, CAO Li-Yong

Acta Agron Sin. 2010, 36(09):  1506-1511.  doi:10.3724/SP.J.1006.2010.01506

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Flowerdevelopment plays an important role in the life cycle of plant. However, the molecular mechanism of floral organ development has not been clear in rice (Oryza sativa L.). The mutants with abnormal flower organ were important materials for researching the flower development. In this study, a spontaneous mutant named Osleg, with two long empty glumes, was discovered from special rice cultivar Buxuenuo. Using scanning electron micrograph, we observed that the abaxial surface of the mutant Oslegrich in trichomes was rough and some tubercles were arranged in parallel, which has the similar structure to the epidermic cells of the lemma. The results suggested that the mutant traits could be evolved from the two lemmas during the evolution of Oryza. To mapping the gene OsLEG, we used mutant Osleg and 9311 as parents to structure F₂ population. On the basis of the field observation, the ratio of normal empty glumes to long empty glumes was 4302:1485, fitting the 3:1 ratio [χ²(0.246)< χ²_0.05(3.84)]. Genetic analysis showed that the mutant character was controlled by a single recessive gene. Ultimately using the published SSR markers and designed some STS makers, the OsLEG was mapped to a 207-kb region between the STS markers LC15 and LC25 on the short arm of chromosome 7 across two BAC clones. With in this region, there were forty-six predicted genes in the rice database [TIGR release 5(RAP2 build 4.0)]. None of them was related directly to glumes in rice. But, one encoded F-box protein had connection with floral development and could be related to the OsLEG to a certain extent. Those studies will pave a way for the OsLEG cloning and study on the molecular genetic mechanisms of the floral organ in monocot.

Quality Improvement of Long-te-fu Male Sterile Lines with Antisense Wx Gene and Associated Application in Rice Breeding

WANG Xin-Qi, YAN Li-Qing, LU You-Lin, CHEN Ge-Zhi

Acta Agron Sin. 2010, 36(09):  1512-1518.  doi:10.3724/SP.J.1006.2010.01512

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In this study, we have generated the Long-te-fu new maintain lines B (wxLB1, wxLB2) with the low amylose content (AC) in seeds of these lines by trans-antisense Wx gene, and obtained the corresponding new male sterile lines of Xin-long-bao A (wxLA1, wxLA2) by transferring breeding. The agronomic traits, amylose content, gel consistency (GC) and the RVA profile eigenvalue of hybrid offspring by the new sterile lines and the original male sterile lines crossed with restorers respectively were tested, the results showed that the amylose content and grain weight were extremely significant lower than the respective control, the gel consistency (GC) and breakdown viscosity (BDV) were higher than the respective control obviously, and reached the extremely significant level. And the cold viscosity (CPV), setback (SBV), peak time (PeT), pasting temperature (PaT) and consistence (CSV) were significant or extremely significant lower than the respective control. The analysis of variation source on gel consistency and RVA eigenvalue of hybrid offspring indicated that starch GC and the RVA eigenvalue mainly affected by the female parent and both reached to the extremely significant level. The integrative results showed that the improvement quality of the male sterile lines of Long-te-fu was an effective way to meliorate the starch physico-chemical and cooking quality of hybrid in indica rice.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

The Impacts of Climate Changes on Rice Production in the Middle and Lower Reaches of the Yangtze River

YANG Shen-Bin, SHEN Shuang-He, ZHAO Xiao-Yan, ZHAO Yan-Xia, XU Jin-Long, WANG Zhu-Yu, LIU Juan, ZHANG Wei-Wei

Acta Agron Sin. 2010, 36(09):  1519-1528.  doi:10.3724/SP.J.1006.2010.01519

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Increasing atmospheric greenhouse gas concentration is expected to induce significant climate change over the next century, but the impacts on society remain highly uncertain. This paper aimed to assess the potential impacts of climate change on rice crop (Oryza sativa L.) production in the middle and lower reaches of the Yangtze River, where is one of the most important food production regions in China. Data taken from the PRECIS regional climate model were used as the baseline (1961–1990) and future (2021–2050) periods under IPCC SRES A2 and B2 scenario conditions, and were used as input of the rice model ORYZA2000. Simulations were performed with and without considering the enhanced CO₂-fertilization effects to evaluate the response of rice crop to raised temperature and CO₂ concentration, respectively. The results indicated that the rice growth duration would be shortened and yield would be declined significantly with raising temperature future when CO₂-fertilization effects was not considered. The rice growth duration would be shortened by 4.5 d and yield would be reduced by 15.2% under A2 scenario in 2021–2050 periods compared with the baseline weather while they would be 3.4 d shortened and 15% reduced respectively under B2 scenario in the same period. The areas where rice yield reduced more than 20% concentrated on most regions of Anhui, Hubei and Hunan provinces. The significance of the enhanced CO₂-fertilization effect to rice crop was found under the simulated future elevated CO₂ concentrations (2021-2050) for both A2 and B2 scenarios. But it was still not enough to offset the negative effects of warming for single crop rice and early rice, except for the late rice that the contribution of CO₂-fertilization effect on rice yield was greater. With considering CO₂-fertilization effect, the rice yields declined by 5.1% and 5.8% under A2 and B2 scenarios, respectively. The areas with a serious yield reduction decreased and the average yield reduction were lessened remarkably. Meanwhile, the areas with an increase in rice yields were founded in some parts of Jiangxi and Zhejiang provinces, although the yield increase might be less than 10%. In addition, the yield stability, defined as the ratio of standard deviation to average yield at each grid across each province, would be increased in 2021–2050 periods when CO₂-fertilization effect was considered, indicating that the CO₂-fertilization effect may reduce the future yield variability. However, there were still many uncertainties in this study. The possible impact of water stress under future climate was not considered, due to the automatic irrigation pattern selected. The soil parameters used as input to the ORYZA2000 might increase the uncertainties for assessing the impacts of climate change on rice yield. Finally, the overall results were compared with those in other studies, in which CERES-Rice was employed and a good agreement was obtained, indicating that the rice model ORYZA2000 can be well applied in assessing the impact of climate change on rice crop in China.

Monitoring Canopy Leaf Nitrogen Concentration Based on Leaf Hyperspectral Indices in Rice

TIAN Yong-Chao, YANG Jie, TAO Xia, CAO Wei-Xing, SHU Yan

Acta Agron Sin. 2010, 36(09):  1529-1537.  doi:10.3724/SP.J.1006.2010.01529

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The objectives of this study were to analyze the relationships between canopy leaf nitrogen concentration (LNC) and leaf spectral reflectance characteristics of different leaf positions, and to establish useful method for nondestructive and quick assessment of canopy LNC in rice (Oryza sativa L.). Four field experiments were conducted with different N rates and rice cultivars across three growing seasons at different eco-sites, and time-course measurements were taken on leaf hyperspectral reflectance of 350–2 500 nm and LNC at different leaf positions over growth stages. Quantitative relationships and monitoring models of canopy LNC to leaf hyperspectral indices were established by extracting sensitive bands and developing proper spectral indices. The results indicated that the performance of leaf hyperspectral indices were different with varied leaf positions for monitoring canopy LNC, the best single leaf position was the second leaf from the top (L₂), the third leaf from the top followed (L₃), and the averaged spectra of L₂ and L₃ (L₂₃) was the optimum leaf spectra combination which contributed to improving the sensitivity to canopy LNC. The simple ratio spectral indices (SR [R_λ1, R_λ2]) combined green reflectance around 560 nm and red-edge reflectance around 705 nm to near infrared region (NIR) could effectively estimate canopy LNC in rice. New green and red-edge narrow band SRs as SR (R₇₈₀, R₅₈₀) and SR (R₇₈₀, R₇₀₄) performed the best, with the coefficients of determination (R²) respectively as 0.887 and 0.884, and RMSE respectively as 0.216 and 0.235. When the widths of green, red-edge and NIR bands were expanded to 100, 20, and 10 nm respectively, the newly developed broad band SRs as SR [AR_(750–850), AR_(568–588)] and SR [AR_(750–850), AR_(699–709)] were also closely related to canopy LNC, with the coefficients of determination (R²) respectively as 0.886 and 0.883, and RMSE respectively as 0.218 and 0.237 at L₂₃ level.

Analysis of Heat Resistance for Cultivars from North China Winter Wheat Region by Yield and Quality Traits

HAN Li-Ming, ZHANG Yong, PENG Hui-Ru, QIAO Wen-Chen, HE Ming-Qi, WANG Hong-Gang, QU Yan-Ying, HE Zhong-Hu

Acta Agron Sin. 2010, 36(09):  1538-1546.  doi:10.3724/SP.J.1006.2010.01538

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Selection of heat-resistance cultivars is an important approach for coping climate changes as well as ensuring stable production. Fifty-three wheat (Triticum aestivum L.) cultivars and advanced lines from the North China Winter Wheat Region, planted in five locations including Beijing, Shijiazhuang, Hengshui, Anyang, and Tai’an in 2008-2009 wheat season, were used to analyze the effect of heat stress on yield nd quality traits. The result indicated that thousand-kernel weight (TKW) can be used as a simple criterion for heat-resistance selection; Nongda 189, CA0518, and Jingdong 8 performed high yield and high TKW under both normal and heat-stress treatments, and were characterized with high resistance to heat stress; Hengguan 33 and CA0736 performed high yield but medium TKW in all environments, and were characterized with good resistance to heat stress; Nongda 211, Shimai 15, Jimai 22, Nongda 3432, and Shannong 2149 performed high yield and high TKW in normal environments, but low yield and low TKW in heat stress environments, and were characterized with poor resistance to heat stress. The 53 cultivars and lines were classified into five groups including strong, medium strong, medium, medium weak, and weak gluten strength based on Mixograph Midline peak time and peak integral. Under heat stress environment, the grain protein content and hardness were increased while the Mixograph midline peak value, timex value, and timex width were decreased. The Mixograph peak time and midline peak integral for materials with medium weak and weak gluten strength were increased while they were decreased for materials with strong, medium strong, and medium gluten strength.

Population Characteristics and Formation Mechanism for Super-High- Yielding Hybrid Japonica Rice (13.5 t hm^-2)

ZHANG Hong-Cheng, WU Gui-Cheng, LI De-Jian, XIAO Yue-Cheng, GONG Jin-Long, LI Jie, DAI Qi-Gen, HE Zhong-Yang, XU Ke, GAO Hui, WEI Hai-Yan, SHA An-Qi, ZHOU You-Tan, WANG Bao-Jin, WU Ai-Guo

Acta Agron Sin. 2010, 36(09):  1547-1558.  doi:10.3724/SP.J.1006.2010.01547

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Population characteristics of super-high-yielding hybrid japonica rice (13.5 t ha^-1) were studied and its formation mechanism was explored using Yongyou 8 as material in Xinghua and Jiangyan. Results showed that population of 13.5 t ha^-1 had more spikelets per panicle and total spikelets than population of 12.0 t ha^-1. There was no significant difference in panicles, filled-grain percentage and 1000-grain weight between populations of 13.5 t ha^-1 and 12.0 t ha^-1. Population of 13.5 t ha^-1 exhibited fewer tillers at the early growth stage and achieved excepted number of stems and tillers at critical leaf-age for productive tillers, whose max number of stems and tillers was at jointing stage and was about 1.3 times of excepted number. Then, the number of population stems and tillers began to decrease stably, which achieved expected number again. At last, ratio of productive tillers to total tillers of 13.5 t ha^-1 population was more than 75%, which was higher than that of population of 12.0 t ha^-1.The leaf area index of 13.5 t ha^-1 population was lower than that of 12.0 t ha^-1 population at the early growth stage, and the max leaf area index was about 8.5 at booting, which decreased stably and was above 4.0 at maturity. The photosynthetic potential of population with 13.5 t ha^-1 was small at early stage and larger at middle and late stages, as compared with population with 12.0 t ha^-1. The total photosynthetic potential was above 6.75×10⁶ m² d ha^-1, of which most than 45.0% was from heading to maturity. The dry matter accumulation was smaller compared with population with 12.0 t ha^-1 before jointing, and the weight of it was above 60 kg ha^-1 at heading, which was significantly higher than that of population with 12.0 t ha^-1. The total weight of dry matter was above 23.25 t ha^-1, of which above 9.75 t ha^-1 was accumulated from heading to maturity. Formation mechanism of super-high yielding population (13.5 t ha^-1) was that: population quality was enhanced at critical leaf-age for productive tillers through cultivating strong seedlings, germinating low positiontillers and achieved expected number of stems and tillers in time, which formed the biological foundation for high quality population at middle stage; in order to form high photosynthetic efficiency of population structure with strong lodging-resistance and large population spikeletes at heading, suitable number of strong stems and large panicles was cultivated through establishing suitable dynamic and size of population; in order to enlarge sink-filling and keep strength of stems and sheaths, dry matter accumulation was enriched after heading through photosynthetic system smooth and steady fade away.

Effects of Soybean and Cotton Growth on Soil Respiration

YAN Jing-Jing, YANG Lan-Fang, LONG Jing

Acta Agron Sin. 2010, 36(09):  1559-1567.  doi:10.3724/SP.J.1006.2010.01559

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Soil respiration is an important factor in carbon cycle in ecosystem, which influences the concentration of CO₂ in atmosphere. To understand effects on soil respiration in the leguminous and non-leguminous crops, we conducted a pot experiment planted soybean (Glycine max) and cotton (Gossypium spp), and the soil respiration rate during crop growing season was sampled by static closed chamber method and analyzed by gas chromatography. The results showed that seasonal changes of soil respiration rate in cropped soil were in accord with crop growing and there were significant correlations of quadratic function between soil respiration rates and growing days of crops. While the seasonal changes of soil respiration rate in bare soils were not significant and their correlations to days after sowing were weak. The maximum soil respiration rate in soybean planted soil was 2.4 times as high as and appeared earlier than that in cotton planted soil. In the soil planted soybean, the respiration rate for growing stages was seedling <branching <ripening <flowering-podding <filling stages, the soil respiration during filling and flowering-podding stages contributed 82% of the total soil respiration, but the days of the growing stages accounted for only 38.7% of the entire growth period, while in cotton planted soil, that was seedling <boll opening <budding <flowering and boll forming stages, soil respiration during budding, flowering and boll forming stages contributed 77.8% of the total soil respiration, but the days of the growing stages accounted for only 44.7% of entire growth period. The total soil respiration in soybean and cotton planted soil was 11.5 and 4.9 times as high as that in its corresponding bare soil. The total respiration, the average soil respiration rate, the total rhizosphere respiration, and the average rhizosphere respiration rate in soybean planted soil were 1.77, 2.34, 2.03 and 2.68 times as high as those in cotton planted soil, respectively. The contribution of rhizosphere respiration to soil respiration during whole growing period was 91.3%, ranging from 3.2% to 95.8% in soybean planted soil, and 79.6%, ranging from 21.8% to 88.0% in cotton planted soil. The exponential correlation between soil respiration rates and air temperatures was significant in growing plants soil, but not in bare soils. The N fertilizer had no significant effect on bare soil respiration. In summary, in the system of soil-crops, crop types and their growing stages are the main factors affected soil respiration, rhizosphere respiration is the main component of soil respiration, and by reason of symbiotic nitrogen fixation, soil respiration and the contribution of rhizosphere respiration were significantly higher in growing soybean soil than in growing cotton soil.

Fertility Responses to Drought Injury at Booting Stage of Rice Maintainers and Remedy Effects of Water Complement

TAO Long-Xin, FU Guan-Fu, SONG Jian, XIONG Jie, LE Ming-Kai, WANG Xi

Acta Agron Sin. 2010, 36(09):  1568-1577.  doi:10.3724/SP.J.1006.2010.01568

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Drought tolerance traits of 14 widely used Chinese rice maintainers were evaluated at booting stage by using both soil moisture meter and drying soil methods. According to drought stress index, the maintainers were classified as four classes, i.e. drought-insensitive, drought-resistant, drought-friability and drought-sensitive. Typical drought-insensitive maintainers K22-B, Jin 23-B and typical drought-sensitive maintainers Zhenshan 97-B, Zhong9-B were selected to suffer drought treatments. The results indicated that secondary panicles were more sensitive than primary panicles, and inferior grains were more sensitive than superior grains to drought stress in both drought-insensitive and drought-sensitive maintainers. These drought-tolerant varieties showed an apical dominance in rice panicles. Drought tolerances at three growth stages corresponding to pollen-mother-cell-meiosis, pollen-forming and pollen-filling stages were also compared, showing that pollen-filling stage was most sensitive to drought stress while pollen-mother-cell-meiosis stage was most insensitive to drought stress. Drought-injury at booting stage was ameliorated obviously with water supplement remedy, especially in the inferior grains of drought-insensitive maintainers. Percentage of partially filled grains other than that of abortive grains decreased obviously. It indicates that drought-caused abortion to rice grains is irreversible.

Effect of in-Season Nitrogen Management on Grain Yield and Nitrogen Use Efficiency in Wheat

XIE You-Liang, HUANG Yu-Fang, LIU Chun-Sheng, QU Ri-Tao, SONG Hai-Yan

Acta Agron Sin. 2010, 36(09):  1578-1584.  doi:10.3724/SP.J.1006.2010.01578

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Heavy nitrogen (N) fertilization is traditionally accepted by farmers in high-yielding wheat (Triticum aestivum L.) production. This fertilization strategy not only results in low N use efficiency and environmental pollution but also restricts to achieve high yield potentials of wheat cultivars. Site-specific N management is based on an in-season assessment of nitrate nitrogen (NO₃^--N) in soil and the required N quantity of wheat. Although the optimal N application rate during wheat growth period has been widely studied, including in-season N fertilization management, there is no an applicable fertilization scheme based on NO₃^--N monitoring for wheat fields with yield higher than 7500 kg ha^-1. In this study, four locations from typical high-yielding regions in Tai’an and Yanzhou of Shangdong province, China were selected as experimental sites, and local wheat cultivars were planted for treatments of in-season optimized N management (OPT) and farmer’s traditional fertilization (FR) under two growing seasons. According to yield target of 7 500 kg ha^-1, the N supply amount in OPT treatment was defined as pure N of 150 kg ha^-1 from sowing to jointing and 210 kg ha^-1 from jointing to maturity. A total of 125.1–155.5 kg ha^-1 and 125.9–164.4 kg ha^-1of N fertilizer were used in 2004 and 2005 year, respectively. In FR treatments, approximately 267.8 kg ha^-1 of N was applied, which was higher than that of OPT treatment by 38.61%–53.29%. Grain yield of OPT treatment was higher than that of FR treatment by 0.87%–10.44% with an average of 5.82%. Compared with FR treatment, OPT treatment had higher levels of several indices of N utilization. For instance, N uptake efficiency increased by 36.67%–85.69%, N recovery efficiency increased by 58.49%–267.69%, N agronomy efficiency increased by 34.16%–410.58%, and N partial factor productivity increased by 74.23%–124.87%. The value/cost ratio in OPT treatment was larger than that in FR treatment by 78.50%–112.09%. These results suggested that in-season N management strategy based on soil nitrate N test may reduce N application rate, increase N use efficiency, grain yield, and value/cost ratio in wheat.

RESEARCH ACTIVITIES

Classification and Evolution Analysis for Vigna Subgenus Ceratotropis Based on SSR Markers and ITS Sequences

MA Yan-Ling, CHENG Xu-Zhen, WANG Li-Xia, WANG Su-Hua, ZHAO Dan

Acta Agron Sin. 2010, 36(09):  1585-1595.  doi:10.3724/SP.J.1006.2010.01585

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Ninety-three materials in subgenus Ceratotropis, two landraces ofsubgenus Vigna and one accession of Glycine soja from various regions of China were analyzed by using simple sequence repeat (SSR) makers and sequencing nrDNA internal transcribed spacer (ITS) for the genetic evaluation. Twenty-sevenspecific SSR primers were selected by screening 74 azuki bean primers and 14 blackgram primers that distributed in 11 linkage groups and five mungbean primers in linkage group 9 with the average polymorphic information content (PIC) value 0.4914. In UPGMA cluster analysis, 95 materials excluding HAI_103 (G. soja) were divided into Group I (including section Ceratotropis and three “transitional” materials) and Group II (section Angulares). And the transferability of 23 primers from azuki bean reached 88%. As for ITS analysis, Kimura-2-parameter distance was calculated based on ITS sequences of 28 representing materials. The shortest distance was found between V. minima and V. umbellata with 0–0.005 and V. radiata was the most intra-specific divergent. Phylogenetic trees constructed by maximum parsimony (MP) and neighbor-joining (NJ) methods with MEGA 4.0 showed that 28 materials were divided into three groups. This result was consistent with the classification results by phenotypes and SSR makers. Therefore, it is anticipated that more information for classification of subgenus Ceratotropis can be provided by these two molecular methods and also a system for evaluation combined by morphological characteristics can be established.

Difference of Endogenous Hormones in Leaves between Main Stem and Tillers and Its Effect on Spike Formation in Large Spike Winter Wheat Cultivar LanKao Aizao 8 under Different Plant Densities

XU Li-Na, FENG Wei, SHENG Kun, ZHU Yun-Ji, MA Dong-Yun, GUO Tian-Cai

Acta Agron Sin. 2010, 36(09):  1596-1604.  doi:10.3724/SP.J.1006.2010.01596

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Contents of indoleacetic acid (IAA), zeatin riboside (ZR), and abscisic acid (ABA) were determined in the first fully expanded leaves of the first and the second tillers, and the main stem of Lankao Aizao 8 under different planting densities. The contents of IAA and ZR were higher in the main stem than in tillers, and the content of ABA was higher in tillers than in the main stem. The time of initiated increasing for content differences between the main stem and tillers was since early jointing stage for IAA and ZR and 6 to 12 d later for ABA. These differences on hormone contents enhanced with the growing of planting density, leading to senescence of tillers ultimately. Compare with single hormone content, the balance of endogeneous hormones was more important for the formation of spike in tillers. The leaf ZR/ABA value and tiller/stem ratio for IAA/ABA and ZR/ABA made the judgment for the critical period of tiller senescence and development advanced to double-ridge telophase, and 6 to 22 d earlier than that based on single hormone content.

Cloning and Activity Analysis of Zea mays ZmPR4 Promoter in Wheat Immature Embryonic Cali

WANG Ai-Yun, ZHUANG Hong-Chao, ZHANG Zeng-Yan, ZHANG Xue-Wen, DU Li-Pu, YE Xin-Guo

Acta Agron Sin. 2010, 36(09):  1605-1609.  doi:10.3724/SP.J.1006.2010.01605

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The ZmPR4 promoter was cloned from genomic DNA of maize inbred line B37 through specific PCR amplification. The promoter cloned had the same sequence as the fragment registered in GenBank under the accession number of AJ969166. Expression vectors driven by ZmPR4 promoter or Ubiquitin promoterwere constructed, which harbor GUS gene. The vectors were bombarded into wheat immature embryogenic calli. Histochemical assays of GUS activity, the ZmPR4 promoter was obviously expressed in wheat immature embryonic calli, but the expression activity was lower than that of Ubi Promoter. The ZmPR4 promoter could be induced by infection of Rhizoctonia cerealis. PCR assay confirmed the expression of GUS gene driven by ZmPR4 promoter. These results suggest that ZmPR4promoter has a use potential in molecular breeding of resistance in wheat.

Agronomic and Quality Traits of a Wheat-Psathyrostachys huashanica 1Ns Disomic Addition Line

zhAO Ji-Xin, WU Jun, CHENG Xue-Ni, DONG Jian, CHEN Xin-Hong, LIU Shu-Hui, DU Wan-Li, PANG Yu-Hui, YANG Qun-Hui, JI Wan-Quan, FU Jie

Acta Agron Sin. 2010, 36(09):  1610-1614.  doi:10.3724/SP.J.1006.2010.01610

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The 1Ns disomic addition line H9021-28-5 is the hybrid between common wheat (Triticum aestivum L.) and Psathyrostachys huashanica. The agronomic traits, processing quality, and mineral element contents of H9021-28-5 were investigated and measured. Compared with the wheat parent 7182, H9021-28-5 appeared significantly lower plant height, smaller numbers of tiller and spikelet, fewer grains per spike, and lower seed-setting ratio. However, the resistance to stripe rust was improved. The processing quality test showed that the sedimentation value, dough stability time, degree of softening, and extension area of H9021-28-5 were significantly improved than those of its parent 7182. The contents of Mg, Cu, Zn, and Mo in H9021-28-5 grains were significantly higher than those in 7182 grains. The results suggested that P. huashanica 1Ns chromosome might have a positive effect on some agronomic traits, flour processing properties, and contents of a few microelements.