Table of Content

12 January 2011, Volume 37 Issue 01

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REVIEW

New Gene Discovery of Crops in China: Status, Challenging, and Perspective

QIU Li-Juan, GUO Yong, LI Yu, WANG Xiao-Bei, ZHOU Guo-An, LIU Zhang-Xiong, ZHOU Shi-Rong, LI Xin-Hai, MA Wei-Zhi, WANG Jian-Kang, WAN Jian-Min

Acta Agron Sin. 2011, 37(01):  1-17.  doi:10.3724/SP.J.1006.2011.00001

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Gene discovery is the basis of molecular breeding in crops. The progress of gene discovery study of major crops such as rice, wheat, maize, soybean, cotton and oilseed rape in China during the past ten years was analyzed and reviewed in this paper. Gene discovery of crops in China has also made a series of breakthroughs: (1) A number of distinctive gene discovery materials were created, such as core germplasm based on crop genetic diversity, genetic population based on excellent genetic resources, mutants derived from artificial mutation, and so on. (2) Technology and methods of gene discovery were developed, especially the integration of various gene discovery technologies and improvement of biometric algorithm of gene/QTLs, and therefore the efficiency of gene discovery was improved. (3) Mapping markers and genes related to agronomic traits of crops has become a common method for genetic studies. A number of genes/QTLs associated with disease resistance, stress tolerance, quality, nutrient efficiency and yield have been mapped, of which more than 500 genes have been fine mapping. (4) Gene cloning and functional study in crops especially in rice become more and more important in the world. More than 300 genes have been cloned in the main crops, among which more than 70 genes have been functional validated in crops. With the development of genome sequence technology, gene discovery of crops become more and more efficient, large-scale and practical. However, the quality and quantity of crop gene discovery is still far from meeting the needs of molecular breeding of crops and the overall level of gene discovery has still fallen behind developed countries in the world. The development of gene discovery in different crops is uneven, the number of genes discovered is relatively limited and discovered genes with great value is still scare. Focused on the problems of gene discovery in China and the challenges of biotechnology companies in the worldwide, the strategy of crops gene discovery in China was proposed in this paper, including improvement of the efficiency of gene discovery, enhancement of gene cloning and the value of important genes, and the orientation of the development needs of biotechnology industry.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Pathogenic Races and Virulence Gene Structure of Magnaporthe oryzae Population and Rice Breeding Strategy for Blast Resistance in Heilongjiang Province

LEI Cai-Lin, ZHANG Guo-Min, CHENG Zhi-Jun, MA Jun-Tao, WANG Jiu-Lin, XIN Ai-Hua, CHEN Peng, XIAO Jia-Lei, ZHANG Xin, LIU Ying-Xue, GUO Xiu-Peng

Acta Agron Sin. 2011, 37(01):  18-27.  doi:10.3724/SP.J.1006.2011.00018

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The rice blast became more severe in Heilongjiang province during the past few years, causing a large loss of rice yield. A total of 173 Magnaporthe oryzae (M. oryzae) isolates, collected from different rice-cropping districts of the province in 2006, were tested for their pathogenicity against 9 Japanese and 7 Chinese differential varieties (DVs) together with 31 rice monogenic lines (MLs) with different blast resistance genes and 12 local leading cultivars. Out of these 173 isolates, 55 Japanese races (pathotypes) were identified by using the Japanese DVs, and the predominant races were 017, 077, 037, 377, and 047, accounting for 42.29% of all the tested isolates. The comparison of differential ability between Japanese and Chinese DVs testified that the former one was much more suitable for M. oryzae pathotyping in Heilongjiang province. Among 12 leading cultivars tested, only Longjing 14 and Longdun 104 still kept good resistance to blast disease. The resistance gene Pi9 showed broadest resistance spectrum (on average 94.80%) to all the blast isolates tested, and was of the highest utilization value in rice blast resistance breeding. The resistance genes Pi-z5(CA) Pi-z5(R), Pi-ta2(R), Pi-ta2(P), Pi-12(t), and Pi20(t) also showed high utilization values due to their resistance spectra of around 70%. The most effective breeding strategy for blast resistance should be as follows: 1) to utilize rationally Longjing 14, Longdun 104 and Pi9 as resistance donors, and pyramid one to several more broad-spectrum resistance genes into elite leading cultivars by means of marker-assisted selection; 2) to strengthen the monitoring of predominant virulent races and their temporal and spatial variation; and 3) to explore new resistance resources extensively and transfer the new broad-spectrum resistance genes into leading cultivars purposefully.

Isolation, Chromosome Assignment, and Expression Assay of Nitrite Reductase Gene and Regulatory Sequence in Wheat

SHE Mao-Yun, CHEN Duo-Duo, FENG Chen, DU Li-Pu, YE Xing-Guo

Acta Agron Sin. 2011, 37(01):  28-39.  doi:10.3724/SP.J.1006.2011.00028

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Nitrite reductase is wildly involved in N metabolism in plants and has shown excellent relevance to regeneration potential in the tissue culture of rice (Oryza sativa L.). In this study, in silico and inverse PCR techniques were employed to isolate nitrite reductase encoded gene and its regulatory sequences from wheat (Triticum aestivum L.). This gene was predicted to contain four exons and three introns. The gDNA and cDNA sequences were 2 881 bp and 1 830 bp in length, respectively, and they were both submitted to GenBank under the accession numbers FJ555239 and FJ527909. Its deduced encoding protein product was approximately 65.7 kD, sharing high (more than 60%) identity with other nitrite reductase genes deposited in the NCBI database, especially with those from other monocot cereal crops (more than 80%). The 5′ flanking region was isolated and extended to -2 924 bp (counting from the start code: ATG) through inverse PCR. After induced by 1 mmol L^-1 IPTG, a protein of ca. 70 kD was obtained in prokaryotic expression vector pET-28a, including a histidine tag of ca. 3.8 kD. The highest expression of gene in wheat seedlings was induced by 30 mmol L^-1 KNO₃ for 1 h. Measurement on nitrite reductase activity showed the enzyme activity increased following the treatment time extension at 5-d intervals under the above same condition. According to the result of AS-PCR analysis, at least one copy of the gene existed on chromosome 6A and 6B each in common wheat. The study provides a basis for functional determination of wheat nitrite reductase gene in subsequent research.

Structure and Expression Analysis of Two Novel Genes Encoding β-glucanase in Cotton

DONG Jia, CA Cai-Peng, WANG Li-Ke, ZHAO Liang, ZHANG Tian-Zhen, GUO Wang-Zhen

Acta Agron Sin. 2011, 37(01):  40-47.  doi:10.3724/SP.J.1006.2011.00040

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The β-glucanase is a type of enzyme degrading β-glucan. Cloning and expression analysis of genes encoding β-glucanase can provide information in both gene resources and breeding utilization for improvement of cotton fiber quality. The two novel genes encoding β-glucanase, designated as GhEG (GenBank accession No: HM462003) and GhGLU (GenBank accession No: HM462004), were obtained by sillico cloning and cDNA library screening, respectively. GhEG contained an open reading frame of 1 581 bp that encoded a polypeptide of 526 amino acids, and GhGLU contained an open reading frame of 1 410 bp that encoded a polypeptide of 469 amino acids. The genome sequence indicated that GhEG has five introns and six exons, while GhGLU has no intron and only one exon. The two genes all had one copy in diploid cotton species G. herbaceum and G. raimondii and two copies in tetraploid cotton species G. hirsutum acc. TM-1 and G. barbadense cv. Hai 7124, respectively. One of GhEG or GhGLU homoelogs in tetraploid was located on chromosome 19 and chromosome 4 by developing SNP marker, respectively. Q-PCR expression analysis showed that GhEG was expressed specifically in fiber elongation and had obvious difference between TM-1 and Hai7124 at the fiber elongation period of 15 DPA and 20 DPA, almost no transcripts were detected in root, stem and leaf. GhGLU was expressed in all tissues, dominantly in root, at fiber initiation and fiber late elongation phase, with obvious difference between TM-1 and Hai7124.

Analysis of Loci and Alleles Associated with Hybrid Yield in Soybean

YANG Jia-Yin, HE Jian-Bei, WANG Jin-She, GUAN Rong-Zhan, GAI Jun-Yi

Acta Agron Sin. 2011, 37(01):  48-57.  doi:10.3724/SP.J.1006.2011.00048

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Single marker regression analysis is a effective way to detect differences among genotypes associated with marker alleles in quantitative traits. Eight soybean parental materials, seven from Huang-Huai region in China and one from US with maturity group II–IV, were used to develop a set of diallel crosses according to Griffing’s Method II, including the eight parents and their twenty-eight crosses. The molecular data of 300 SSR markers on eight parental materials were obtained and analyzed for association between SSR markers and hybrid yield using the single marker regression analysis. The hybrid crosses were dissected into their allele constitution and the effects of alleles and genotypic values of single locus were estimated. The results showed that 38 SSR loci located on 17 linkage groups were identified to associate with hybrid yield in the diallel crosses with more loci on linkage groups D1a, M, etc., and eight of the 38 loci were located within a region of ±5 cM apart from a known QTL identified from family-based linkage (FBL) mapping in the literature. Each of the loci explained 11.95%–30.20% of the phenotypic variance of hybrid yield. The allele pairs of the hybrids were composed of four parts, i.e. positive dominant heterozygous loci, positive additive homozygous loci, negative additive homozygous loci and dominant heterozygous loci, with their relative importance in a descending order. Among the 38 loci associated with hybrid yield, nine elite loci such as Satt449, Satt233 and Satt631 and nine elite alleles such as Satt449–A311, Satt233–A217 and Satt631–A152 were identified. Meanwhile, nine heterozygous allele pairs such as Satt449–A291/311, Satt233–A202/207 and Satt631–A152/180 were detected. These results will provide some relevant information for understanding the genetic basis of heterosis and lay a foundation for hybrid soybean breeding by design.

Analysis of Sequence Polymorphism of ZmRCA1 in Maize

TAN Xian-Jie, SONG Yan-Chun, SHI Yun-Su, CHENG Wei-Dong, WU Zi-Kai, WANG Tian-Yu, LI Yu

Acta Agron Sin. 2011, 37(01):  58-66.  doi:10.3724/SP.J.1006.2011.00058

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Rubisco is a pivotal enzyme that initiates the first step of carbon fixation and photorespiration in plant photosynthesis. Rubisco accounts for up to half of the soluble protein in the leaves of plants. Nevertheless the catalytic rate of Rubisco iscomparatively low. Rubisco activity is regulated mainly by Rubisco activase, which serves as a molecular chaperone. By activating and regulating Rubisco, RCA potentially influences the efficiency of carbon assimilation in plants. Thereby, RCA has identified a possible target gene for improve production in crops breeding.To investigate polymorphism of ZmRCA1, sequened and analyzed the genomic sequences of ZmRCA1 from a minicore set of 95 maize inbreds lines. Totally 22 SNPs and 8 InDels were identified in a 1 680 bp sequence alignment. There were five SNPs and one InDel which generated amino acid sequence variation. A total of 27 haplotypes were identified with 13 polymorphic loci which the frequency was 0.1 or more. Approximately 90% haplotypes could be distinctly distinguished by six polymorphic loci. The ZmRCA1 gene was highly conserved, with the genic similarity of 97.9% and the amino acid sequence similarity of 99.8%. Neutrality tests showed that no purifying selection occurred in ZmRCA1.

Primary Infection Suppression of Blumeria graminis f. sp. Tritici and Host Cell Responses Regulated by Pm21 Gene in Wheat

ZHANG Zhen, LIU Xin-Hong, CUI Hong-Cui, WANG Hua-Zhong

Acta Agron Sin. 2011, 37(01):  67-73.  doi:10.3724/SP.J.1006.2011.00067

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Pm21 is a wide-spectrum resistance gene to powdery mildew (Blumeria graminis f. sp. tritici, Bgt) in wheat (Triticum aestivum L.), which originates from Haynaldia villosa. To reveal the mechanism of Pm21-mediated Bgt resistance in wheat at early infection stage, we carried out the cytological observations using wheat line 92R137, carrying Pm21 gene and presenting immunity (but with visible spots on leaves) to Bgt after artificial inoculation with the prevalent Bgt race 15. Chinese Spring (CS) was used as the susceptible control. In wheat–Bgt interaction sites on leaves, papillae formed at a similar time in challenged epidermal cells in both 92R137 and CS. However, the papillae were larger and more compact and persisted in longer time in 92R137 than in CS, resulting in effectively blocking the penetration of Bgt. Accumulation of H₂O₂ was observed in the papillae of 92R137 by DAB staining. Appressorium malformation occurred in 92R137, which was probably caused by the failure of multiple penetration attempts of Bgt. For the small number of Bgt that successfully penetrated the epidermal cells of 92R137, haustorium-dependent hypersensitive reactions were induced to suppress further development of haustoria and secondary hyphae, arresting onset of powdery mildew. Therefore, the major mechanism of Pm21-mediated Bgt resistance involves challenged host cell wall reinforcement and hypersensitive reaction.

Transferability Analysis of Cassava EST-SSR and Genomic-SSR Markers in Jatropha and Rubber Tree

WEN Meng-Fu, CHEN Xin, WANG Hai-Yan, LU Cheng, WANG Wen-Quan

Acta Agron Sin. 2011, 37(01):  74-78.  doi:10.3724/SP.J.1006.2011.00074

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Euphorbiaceae family includes abundant economic species, such as rubber tree, cassava, castor bean and Jatropha. Cassava (Manihot esculenta Crantz) ranks in the sixth food crop in the world. In China, cassava is also an important tropical economic crop. The genomic-SSRs derived from cassava genome, and EST-SSRs derived from expressed sequence tags (ESTs). In this study, the transferability of 419 pairs of EST-SSR primer and 182 pairs of genomic-SSR primer from cassava was tested in five Jatropha lines and two rubber tree lines. The result showed that the transferability rate of cassava EST-SSR in Jatropha and rubber tree was 55.85% and 38.90%, and the transferability rate of cassava genomic-SSR in Jatropha and rubber tree was 37.36% and 26.37%, respectively. The transferability EST-SSR was higher for cssava than for genomic-SSR. Meanwhile, the transferability of cassava EST-SSR and genomic-SSR was higher in Jatropha than in rubber tree. These results suggested that the cassava SSR can be used for comparative mapping, gene tagging and QTL mapping among cassava, Jatropha and rubber tree.

Cloning, Prokaryotic Expression, and Functional Testing of a γ-Gliadin Gene from Wheat Cultivar Shaan 253

WANG Ming-Xia, GAO Xiang, CHEN Qi-Jiao, DONG Jian, ZHAO Wan-Chun, LI Yan-Liang, LI Min

Acta Agron Sin. 2011, 37(01):  79-86.  doi:10.3724/SP.J.1006.2011.00079

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The γ-gliadin gene (GenBank accession number GQ857626) was isolated from a wheat (Triticum aestivum) cultivar with a hight quality Shaan 253, using inductuion a set of genome specific primers. The deduced amino acid sequence of GQ857626 exhibited an additional cysteine residue in the region II of mature γ-gliadin subunits compared to the previous report. A prokaryotic expression vector was constructed to express GQ857626 in the host bacterium Escherichia coli Rosetta-gami B (DE3). The SDS-PAGE and Western blot analysis confirmed that the fusion protein was expressed by induction of 0.1 mmol L^-1 isopropyl-β-D-thiogalactoside (IPTG), and its actual molecular weight was about 50 kD nearly equal to the predicted. After separation and purification using HisTrap HP affinity chromatography, the function of fusion protein was tested by means of micro 4 g farinograph. When the subunit of GQ857626 was integrated into the control flour through oxidation-reduction reaction, many important farinograph parameters changed drastically, such as development time, dough stabilizing time, degree of softening. Although the gluten strength of the control flour could be improved in some degree, the subunit of GQ857626 showed a negative effect on the rheological properties of wheat flour.

Development of Exon-Targeted Intron-Exon Splicing Conjunction (ET-ISJ) Marker and Establishment of Upland Cotton Genetic Map

LIN Gang, ZHANG Jian, ZHANG Ke, TENG Zhong-Hua, ZHANG Zheng-Sheng

Acta Agron Sin. 2011, 37(01):  87-94.  doi:10.3724/SP.J.1006.2011.00087

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Cotton is the leading fiber crop in the world, and upland cotton contributes over 95% of cotton production. The genetic map of upland cotton is far from saturated, so it is necessary to develop new markers for it. ET-ISJ (exon targeted intron-exon splice conjunctions) maker primers were designed according to the conserved intron-exon splicing junction sequences. A total of 1 280 ET-ISJ primer combinations were used to screen polymorphism between upland cotton cultivar Yumian 1 and T586, and 69 of which showed polymorphism, accounting for 5.4% of total primer combinations. The 69 polymorphic ET-ISJ primer combinations were used to detect (Yumian 1 × T586) F_2:7 recombinant inbred line population, and 70 ET-ISJ loci were obtained. Linkage analysis was conducted on 70 ET-ISJ loci, 523 SSR, 59 IT-ISJ, 29 SRAP and 8 morphological loci, and a linkage map including 59 linkage groups and 673 loci (68 ET-ISJ, 510 SSR, 58 IT-ISJ, 29 SRAP and 8 morphological loci) was established. The linkage map covered 3 216.7 cM, accounting for 72.3% of cotton genome, with an average interval of 4.8 cM between two markers. Sixty-eight ET-ISJ loci were located on 20 chromosomes.The present study demonstrated that ET-ISJ markers are stable, relatively-high polymorphic, and able to be effectively applied in genetic map construction of cotton and other plant’s.

Identification of Fiber Length-Related Genes Using Cotton Oligonucleotide Microarrays

LI Long-Yun, XU Wen-Wen, ZHAI Hong-Hong, HUANG Shuang-Ling, LI Xin-Li, ZHANG Hong-Wei, ZHANG Jin-Fa

Acta Agron Sin. 2011, 37(01):  95-104.  doi:10.3724/SP.J.1006.2011.00095

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Gossypium barbadense L. is known for its superior fiber quality including long fiber and their quantitative trait loci (QTL) have been reported. However, little is known about the molecular genetic basis of fiber quality traits. The objective of the present study was to identify differentially expressed genes in the rapid fiber elongation stage (10 days post-anthesis, 10 DPA) using a comparative microarray analysis between two backcross inbred lines (BIL) with contrasting fiber lengths. The two BIL lines, NMGA-062 (33.03 mm) and NMGA-140 (25.87 mm), were selected based on a 3-year field trial in four environments.  The Affymetrix Cotton GeneChip was then used to perform a transcriptome analysis of 24 029 transcripts in developing fibers (10 DPA). Among the transcripts 7 282 (30.31%) showed a significant differential expression (DE) and 3 993 (16.62%) showed 2-fold or higher levels of expression changes between the two BIL lines. Through quantitative RT-PCR analyses on different plant organs and developing fibers of 10 DPA, eight selected DE genes, including Ghi.10655.1.S1_s_at, ACO1, ARF1, SAHH, TUA6,TUA7, β-tub1, and β-tub10, all displayed similar results to theses of the microarray analysis. This indicated that the comparative microarray results were biologically reproducible. Quantitative RT-PCR analyses were also performed at five fiber development stages from 5 to 25 DPA on ARF1, β-tub1, and β-tub10. The results indicated that they were all highly expressed in a period of fast fiber elongation and primary cell wall synthesis (at 10–15 DPA), implicating their roles in fiber elongation. This study represents the first investigation using a microarray analysis to compare differential gene expressions between near-isogenic lines with contrasting fiber quality. It provided a list of putative candidate genes for further studies in identifying genes responsible for fiber traits and developing molecular markers for marker-assisted breeding.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of Different Fertilizers on Functional Diversities of Microbial Flora in Rhizospheric Soil of Monoculture Tobacco

YANG Yu-Gong, CHEN Dong-Mei, JIN Yan, WANG Hai-Bin, DUAN Yu-Qi, GUO Xu-Kuai, HE Hai-Bin, LIN Wen-Xiong

Acta Agron Sin. 2011, 37(01):  105-111.  doi:10.3724/SP.J.1006.2011.00105

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Tobacco is an intolerant continuous cropping crop. Continuous cropping obstacles restrict sustainable development of tobacco production, which are the most important issues in agricultural production that need to be solved urgently. In this study, tobacco was consecutively planted for twelve years in the same soil and the rhizospheric soil was sampled to investigate the changes in the functional diversities of microbial flora after different fertilizer treatments. The results showed that the autotoxic allelopathic potential was maximum for the monoculture soil treated with traditional compound fertilizer, and minimum for the soil treated with farmyard manure. BIOLOG analysis found that the traditional compound fertilizer was conducive to the growth of the microbial flora feeding on amino acids and amine as carbon sources. The commercial organic fertilizer was favorable to the growth of the microbial flora using carboxylic acids as a carbon source, and farmyard manure was good for the growth of the microbial flora feeding on carbohydrate, fatty acids and phenolic acids as carbon sources. Principal component analysis indicated that the first two components related to carbon sources accounted for 74.37% and 25.63% of the data variation, respectively. The carbon source of carbohydrate, fatty acids and phenolic acids made a mainly contribution to the separation of two principal components. Correlation analysis indicated that the autotoxic allelopathic potential of tobacco rhizospheric soil was positively correlated with the AWCD value of microbial flora feeding on carbohydrate and phenolic acids as carbon sources, and negatively correlated with that of the microbial flora using the carbon source of fatty acids. In addition, for the growth of microbial flora in monoculture soil, farmyard manure was the best, commercial organic fertilizer showed the medium effect, and traditional compound fertilizer was the worst.

Alleviation of Drought Stress Inhibition on Photosynthesis by Over Expression of PEPC Gene in Rice

ZHOU Bao-Yuan, DING Zai-Song, ZHAO Meng

Acta Agron Sin. 2011, 37(01):  112-118.  doi:10.3724/SP.J.1006.2011.00112

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Introducingenzymes involved in photosynthesis of C₄ plants into rice is supposed to enhance the photosynthesis and crop productivity. However, only a few researches showed that the photosynthesis and crop productivity has been improved by introducing phosphoenolpyruvate carboxylase (PEPC) gene into rice. In the present research, the photosynthesis in 42 lines of PEPC gene overexpressed rice was investigated. The average photosynthetic rate (P_n) of transgenic rice lines was almost the same as that of the wild type (control) in paddy field, while much higher in upland field. Only a few transgenic lines showed higher P_n in paddy field and most of them showed higher P_n in upland field. Similar results were found in the water controlled experiment. Two transgenic rice lines with different relative activities of PEPC (10 and 25 fold) were selected to study their photosynthesis under different water potentials (0, -20, and -40 kPa). In both lines, P_n was similar with that in the wild type under normal condition (0 kPa) and much higher under drought conditions (-20 and -40 kPa). In both experiments, the transgenic lines had higher P_n under drought conditions, with a much slower decreasing rate than the wild type. Therefore, the present results suggested that the overexpressed PEPC could not improve the photosynthetic rate of transgenic rice plants. But the photosynthetic rate of transgenic rices declined slowly under drought condition. So it is supposed that PEPC might be involved in drought resistance to decrease the inhibition of drought stress on photosynthesis in rice.

Agronomic Traits and Photosynthetic Characteristics of Chlorophyll-Deficient Wheat Mutant Induced by Spaceflight Environment

ZHAO Hong-Bing, GUO Hui-Jun, ZHO Lin-Shu, GU Jia-Yu, ZHAO Shi-Rong, LI Jun-Hui, LIU Lu-Xiang

Acta Agron Sin. 2011, 37(01):  119-126.  doi:10.3724/SP.J.1006.2011.00119

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Chlorophyll deficiency mutants are ideal materials to study photosynthetic mechanism, pathways of chlorophyll biosynthesis and degradation, and genes related to photosynthesis. The chlorophyll-deficient wheat (Triticum aestivum L.) mutant Mt135, induced by space mutagenesis, was investigated on main agronomic traits and photosynthesis characteristics with a comparison to its wild type. The leaf color of the Mt135 showed albino, stripe, and green phenotypes. The albino plants with entire albino leaves died at seedling stage, while plants with green-and-white striped leaves usually matured 5–7 d later than the wild type, and the plant height, spike length, grains and grain weight per plant, and 1000-grain weight were lower. The green plants were not significantly different from the wild type. Preliminary genetic analysis showed that the inheritance model of Mt135 was nucleo-cytoplasmic interaction. When exposed to photosynthetic active radiation (PAR) of 110 μmol m^-2 s^-1, the green tissue of striped plants (S-G) and the wild plant had no significant difference on the value of maximum photosystem II quantum yield, but the potential activity of photosystem II was significantly lower in the S-G plants than in the wild plant. The changes of the photochemical quenching, non-photochemical quenching, effective quantum yield, regulated non-photochemical energy dissipation, and non-regulated energy dissipation were different at various growth stages. In addition, the differences of the electron transport rate, photochemical quenching, and effective quantum yield between S-G plant and wild plant varied under different PAR conditions. The white tissue of striped plant and the albino plant completely lose the photosynthetic function. As a result, the photosynthesis of Mt135 was greatly restricted. High photosynthetic active radiation had tremendous impact on the mutant at elongation stage and relatively weak impact at heading stage. The changes of photosynthetic function of striped plant are in accordance with the reduction of their plant height, spike length, and yield related traits.

Effect of Nitrogen Rate on Vertical Distribution Characteristics of Leaf-Type in Wheat with Different Plant Types

LI Guo-Qiang, TANG Liang, ZHANG Wen-Yu, CAO Wei-Xing, ZHU Yan

Acta Agron Sin. 2011, 37(01):  127-137.  doi:10.3724/SP.J.1006.2011.00127

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The objective of this study was to elucidate the vertical distribution characteristics of leaf using wheat (Triticum aestivum L.) cultivars in compact-high, compact-short, intermediate, and loose plant types with three nitrogen rates in two growing seasons. The leaf-type characteristics at the stages of stem elongation, flowering and grain-filling, and the vertical distribution characteristics of leaf and light within canopy at flowering were measured. Significant differences were observed among genotypes for leaf-type characteristics, and the regulating effects of nitrogen rate varied with leaf-type traits and growth stages. Single leaf area changed in a double-peak curve from canopy base to top. A gradually decreasing tendency with increasing canopy height was found in angle between stem and leaf (ABSL). The maximum leaf area index was located at 0.60 relative canopy height. Light transmission rate increased from the base to top of canopy, and presented a good fitness to quadratic polynomial curve. Single leaf area increased with increasing nitrogen rate, with greater increments in Yangmai 12 and Huaimai 17 than in Ningmai 9 and Aikang 58. The ABSL enhanced with the increasing nitrogen rate. The nitrogen regulation effects on ABSL of Ningmai 9, Huaimai 17, and Yangmai 12 were stronger at canopy base than at canopy top, but Aikang 58 showed a reverse pattern. With the increase of nitrogen rate, leaf area index accumulation at different relative canopy heights increased, while light transmission decreased. The smaller decline of light transmission in Ningmai 9 and Aikang 58 was observed than those in Yangmai 12 and Huaimai 17 when more nitrogen was applicated. The transmittance rate decreased in an exponential pattern with increasing leaf area index accumulation. The grain yield ranked in the order of treatments supplied 150 (N150), 225 (N225) and 75 (N75) kg ha-1. Nitrogen fertilization increased remarkably spike number and harvest index, excluding 1000-grain weight. The grain number per spike was the highest in the N225 treatment, follwded by the N75 treatment. Four wheat cultivars with different plant types differed markedly in grain yield, spike number, grain number per spike, and harvest index. The grain yields were ranked as Aikang 58 > Ningmai 9 > Yangmai 12 > Huaimai 17. These results may provide a technical basis for optimizing nitrogen application to wheat cultivars with different plant types.

Effects of Limited Supplemental Irrigation on Potato in the Semiarid Areas of Middle Gansu Province

QIN Shu-Hao, ZHANG Dun-Lian, WANG Di, XIAO Hong-Lang, PU Yu-Lin

Acta Agron Sin. 2011, 37(01):  138-145.  doi:10.3724/SP.J.1006.2011.00138

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Water supply scarcity is the main limiting factor for sustainable agriculture development in semiarid areas on the Western Loess Plateau. Because of imbalance for rainfall distribution, yield and water use efficiency (WUE) of potato, one of the dominant crops in middle Gansu province, are relatively low. To optimize supplemental irrigation system using limited catchment rainfall for rain-fed potato in the area, field experiments were carried out in 2008–2009 to determine evapotranspiration, WUE, yield, yield traits and quality of rain-fed potato under different supplemental irrigation amounts and timings. The results showed thatWUE of potato increased significantly in the supplemental irrigation treatment of 45 mm, and decreased with increasing of irrigation amount. WUE and irrigating water use efficiency (IWUE) of potato were higher with supplemental irrigation at the seedling than the tuber expanding stage. WUE and IWUE were the highest under the 45 mm of irrigation at the seedling stage.Yield, rates of bigger tuber and middle tuber in rain-fed potato were increased, and small tuber rates were decreased by supplemental irrigation. Big tuber rates were increased by supplemental irrigation at the seedling stage, while medium tuber rates were increased by supplemental irrigation at the tuber expanding period. Potato numbers per plant were decreased, but tuber yield per plant was increased by supplemental irrigation. With increasing of irrigation amount, the yield of potato was not increased significantly, but green tuber rate and blet tuber rate were increased significantly. Starch content of potato was reduced, while protein content of tuber was increased by supplemental irrigation. Supplemental irrigation of 45 mm at seedling is optimal irrigation system for rain-fed potato in the area.

Changes of Safe Dates for Full Heading in Japonica Rice over Past 50 Years in Jiangsu Province

ZHANG Zu-Jian, ZHANG Hong-Xi, YANG Jian-Chang, SONG Yun-Sheng, ZHAO Bu-Hong, JI Hong-Juan, ZHU Qiang-Sen

Acta Agron Sin. 2011, 37(01):  146-151.  doi:10.3724/SP.J.1006.2011.00146

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Determining the safe dates of full heading of rice is very important for arranging sowing and transplanting dates. In this study, the daily average temperatures from May to November during the 50 years (1958–2007) in four regions from north to south in Jiangsu Province (Ganyu, Huai’an, Yangzhou, and Wuxian city) were analyzed. According to the normal indices of temperatures for the safe dates of full heading in japonica rice cultivars with weaker and stronger cold tolerance, safe dates of full heading were obtained for the 50 years from 1958 to 2007, the first 25 years, and the second 25 years. The guarantee rate for the safe dates was 50%, 80%, and 90% respectively. It was observed that the safe dates of full heading during the second 25 years were three to four days later than those during the first 25 years. Variation in the safe dates of full heading was greater for the second 25 years than for the first 25 years. The safe dates of full heading at the four regions from north to south were 18th September, 20th September, 24th September and 28th September, respectively, and were four to six days later than those currently used in these regions. As the global whether is warming, these results could be utilized as references for the production in different rice-growing areas. More experiments should be conducted to observe cold tolerance of rice cultivars during heading and flowering, and to obtain the safe dates of full heading for major varieties, so that more exact sowing and transplanting dates could be got in japonica rice.

Effect of In-Season Nitrogen Management Strategy on Maize Grain Yield and Nitrogen Use Efficiency

YE You-Liang, HUANG Yu-Fang, LIU Chun-Sheng, QU Ri-Tao, SONG Hai-Yan, CUI Zhen-Ling

Acta Agron Sin. 2011, 37(01):  152-157.  doi:10.3724/SP.J.1006.2011.00152

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In order to improve maize yield and nitrogen use efficiency cooperatively, in-season nitrogen management strategy based on soil nitrate nitrogen test was conducted for three years in four fields at Tai’an and Yanzhou city of Shandong province. The results showed that compared with farmers traditional fertilization, maize grain yields of optimized nitrogen management were increased by 2.73%–14.22%, averaged 7.90%, nitrogen rates were reduced by 36.80%–53.85%, averaged 44.75%, nitrogen uptake efficiencies were increased by 13.68%–115.91%, nitrogen recovery efficiencies were increased by 44.26%–377.89%, nitrogen agronomy efficiencies were increased by 54.31%–271.31%, nitrogen partial factor productivities were increased by 53.38%–141.23%, value cost ratios were increased by 37.35%–93.18%. It suggested that in-season nitrogen management strategy based on soil nitrate nitrogen test could reduce maize nitrogen rate, increase nitrogen use efficiency, improve grain yield and value cost ratio.

Moisture Variation and Model Verification of Wheat and Maize Seeds under Different Storage Conditions

WANG Jing, LI Xiao-Li, JIANG Peng, TIAN Feng-Long, HOU Wen-Qian, SUN Qiang-Quan

Acta Agron Sin. 2011, 37(01):  158-164.  doi:10.3724/SP.J.1006.2011.00158

Abstract ( 2350 )   PDF (342KB) ( 1384 )   Save

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Seed equilibrium moisture is an important indicator for evaluating the dynamic changes of seed moisture absorption or moisture desorption. The laws of the seed moisture absorption or moisture desorption under different storage conditions were studied using two maize (Zea mays L.) cultivars and two wheat (Triticum aestivum L.) cultivars with different initial moisture contents (IMC). Simulated models were established accordingly for each cultivar and verified with independent data. The moisture desorption was observed in 8.0% IMC maize seeds under the conditions of 15°C and RH < 18.8%, 25°C and RH < 48.1%, 40°C and RH < 48.1%; or in 13.5% and 18.0% IMC seeds under the conditions of 15°C and RH < 48.1%, 25°C and RH < 48.1%, 40°C and RH < 48.1%; and moisture absorption was observed under other storage conditions. Wheat seeds stored under 15°C, 25°C, and 40°C showed moisture desorption when RH ≤ 18. 8% for 8.0% IMC seeds or RH ≤ 48.1% for 18.0% IMC seeds; the 13.5% IMC seeds stored under the conditions of 25°C and RH < 18.8%, 25°C and RH < 18.8%, 40°C and RH < 18.8% showed moisture desorption; and wheat seeds stored under other storage conditions presentedmoisture absorption. The safe water contents (SWCs) of wheat seed were 13% under 15°C and RH = 53.0%, 11% under 25°C and RH = 48.0%, and 9% under 40°C and RH = 43.0%. The SWCs of maize seed were 14% under 15°C and RH = 55.0%, 12% under 25°C and RH = 50.0%, and 9% under 40°C and RH = 40.0%. The equilibrium moisture contents (EMCs) of wheat seed were higher than the corresponding SWCs under the same condition of 15°C and RH > 50.0%, 25°C and RH > 50.0%, 40°C and RH > 48.0%, and the equilibrium moisture contents (EMCs) of maize seed were higher than the corresponding SWCs under the same condition of 15°C and RH > 50.0%, 25°C and RH > 50.0%, 40°C and RH > 47.0%. The predictive models of equilibrium time (d) for seeds were simulated on the basis of IMC (x), RH (y), and temperature (z). The equations were as follows: d = 35.34 + 4.32x - 0.28y - 0.35z -0.031xy - 0.012xz - 0.0011yz + 0.003y² for maize cultivar Zhengdan 958, d = 39.76 + 2.35x - 0.39y - 0.27z - 0.022xy - 0.014xz - 0.0057yz + 0.008y² for maize cultivar Nongda 108, d = 25.69 + 7.65x - 0.27y - 0.89z - 0.12xy - 0.07xz - 0.007yz + 0.006y²+ 0.04z² for wheat cultivar Shannong 15, and d = 46.67 + 0.39x - 0.28y - 1.72z - 0.006yz + 0.006y²+ 0.017z² for wheat cultivar Tainong 18. The predictive values based on these models were highly consistent with the tested values, indicating the good applicabilities of these models.

RESEARCH ACTIVITIES

Preliminary Localization of Five Qualitative Traits in Kenaf Genetic Linkage Map

CHEN Mei-Xia, QI Jian-Min, WEI Cheng-Lin, XIE Zeng-Rong, LIN Pei-Qing, LAN Tao, TAO Ai-Fen, CHEN Tao

Acta Agron Sin. 2011, 37(01):  165-169.  doi:10.3724/SP.J.1006.2011.00165

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With the genetic linkage map construction for kenaf and quantitative trait loci mapping, it is possible to perform marker-assisted selection to improve kenaf agronomical important traits at molecular level. In this investigation, using a population with 162 F_2:3 individuals from the cross between Alian kenaf (from Egypt) and Fuhong 992 (from Fujian agriculture and forestry university) with high quality and disease resistance, on the basis of the linkage map we had finished, we finally mapped five qualitative trait genes for leaf petiole color, leaf shape, dimension of corolla, corolla shape, stem color at late stage. Analysis using the Mapmaker/Exp 3.0 software showed that there were close linkage relation between the gene of stem color at late stage and leaf petiole color gene, with a genetic distance of 2.8 cM, which were mapped on the linkage group 5. Also linkage existed between dimension of corolla and corolla shape, with a genetic distance of 14.7 cM, which were mapped on the linkage group 6. The genetic distance between leaf shape and dimension of corolla, corolla shape, were 38.2 cM and 23.5 cM, respectively. They were mapped on the linkage group 6, but their linkage relation still requires further research. The results had certain practical significance and by molecular marker-assisted selection were useful for the research of kenaf genetics and the breeding.

Allelopathy and Weed-Suppression of Oryza longistaminata under Water-Nitrogen Interactions in the Field

ZHANG Fu-Dou, XU Gao-Feng, LI Tian-Lin, tAO Da-Yun, XU Peng, ZHANG Yu-Hua

Acta Agron Sin. 2011, 37(01):  170-176.  doi:10.3724/SP.J.1006.2011.00170

Abstract ( 2341 )   PDF (398KB) ( 1582 )   Save

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Under different irrigation and nitrogen levels, wild rice (Oryza longistaminata) with allelopathic potential, and Oryza sativa (RD23) without allelopathic potential and their F₁ (RD23 × O. longistaminata) were used to study their allelopathy and weed-suppression effects to barnyard grass. During 20–50 days after transplanting, four kinds of irrigation managements, and three levels of nitrogen were conducted in the field. In bioassay, the allelopathic effect of extracting solution from rice leaves on barnyard grass germination was observed. The results showed that O. longistaminata gave the strongest allellopathy under the conditions of deficiency water and low nitrogen, the inhibition rates for the root length and dry weight of barnyard grass were 69.3% and 74.6%, and decreased with elongating submerging time and increasing nitrogen. The density and biomass of barnyard grass were investigated after growing together with rice 30 days in the field.Wild rice showed the best weed-suppression effects under the alternation of wet and dry in the field. After dry cultivating for wild rice, irrigation could significantly improve its control effect on barnyard grass. Furthermore, interactive effects between irrigation and nitrogen were significant on the allelopathy and weed-suppression in the field for wild rice and the F₁.

Effects of Exogenous Nitric Oxide Donor SNP on Lipid Peroxidation Caused by Selenium in Rice Seedlings

XIAO Qiang, YANG Shu, ZHENG Hai-Lei

Acta Agron Sin. 2011, 37(01):  177-181.  doi:10.3724/SP.J.1006.2011.00177

Abstract ( 2093 )   PDF (266KB) ( 1419 )   Save

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Nitric oxide (NO) is a bioactive molecule that has been suggested to act as a signaling molecular in plants. It induces germination, affects plant growth and development, and promotes plant cell death. NO is also involved in plant response to heat, salinity, ultraviolet-B, and heavy metal stresses. It is known that some effects of NO may relate to the regulation of reactive oxygen species (ROS) metabolism by means of affecting activities of catalase (CAT) with hemachrome iron, and/or guaiacol peroxidase (GPX) with none-hemachrome iron. However, whether NO regulates lipid peroxidation in rice seedlings induced by selenium is not yet understood. In this article, we reported some regulative  effects of exogenous nitric oxide donor SNP on oxidative stresses induced by selenium in rice seedlings. The contents of chlorophyll, H₂O₂, TBARS and the activities of GPX, superoxide dismutase (SOD), CAT and ascorbate peroxidase (APX) in rice seedlings treated with a varying concentrations of seleniumand 1 μmol L^-1SNP were investigated. The results showed that the content of chlorophyll increased by treatment with SNP in 0.2 μmol L^-1Na₂SeO₃ group. SNP alleviated significantlythe lipid peroxidation in rice seedlings via promoting GPX, APX and CAT activities in rice leaf. In 20 μmol L^-1Na₂SeO₃ treated rice seedlings, SNPalleviated significantlyTBARScontent and the increase of H₂O₂ content that resulted from high selenium stress via promoting GPX, especially APX and CAT activities. Taken together, our results suggested that NO regulates lipid peroxidation caused by selenium in rice seedlings.

Effects of Soil Moisture after Anthesis on Isozymes of Glutamine Synthetase, Grain Yield, and Protein Content in Winter Wheat Yumai 34

XIONG Shu-Ping, WANG Xiao-Chun, MA Xin-Ming, ZHAO Peng, WANG Lu, CHENG Zhen-Yun

Acta Agron Sin. 2011, 37(01):  182-189.  doi:10.3724/SP.J.1006.2011.00182

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In a two-year experiment, the strong-gluten wheat cultivar, Yumai 34, were planted with three treatments, i.e., 40% (40%FC), 60% (60%FC), and 80% (80%FC) of field water holding capacity. The activities of GS and GS isozymes and the soluble protein contents in flag leaf and grain were measured after anthesis. The results showed that GS activity in flag leaf was more than higher than that in grain, and decreased gradually after anthesis. Isozymes GS1, GS2, and GSx were identified in flag leaf, of which GS2 had the highest activity. Only GS1 was observed in grain. The effects of water treatment on activities of GS and GS isozymes both ranked as 60%FC>80%FC>40%FC, and was largest for GS2 in flag leaf. The content of soluble protein in flag leaf ranked as 60%FC>80%FC>40%FC at early stage of grain filling and as 80%FC>60%FC>40%FC afterwards. The content of soluble protein in grain ranked as 80%FC>60%FC>40%FC. In the 60%FC treatment, the content of soluble protein in flag leaf was positively correlated with the activities of GS and GS2 in flag leaf. The highest grain yield and protein content were observed in the 60%FC treatment, indicating that 60% of field water holding capacity was the optimal soil moisture for Yumai 34 growth after anthesis.