Table of Content

12 June 2012, Volume 38 Issue 06

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Association Analysis of Agronomic Traits and Resistance to Aspergillus flavus in the ICRISAT Peanut Mini-Core Collection

HUANG Li,REN Xiao-Ping,ZHANG Xiao-Jie,CHEN Yu-Ning,JIANG Hui-Fang

Acta Agron Sin. 2012, 38(06):  935-946.  doi:10.3724/SP.J.1006.2012.00935

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Yield is an important trait in peanut breeding, which is strongly influenced by environments and complex genetic factors. Association mapping, based on natural population and linkage disequilibrium (LD), has been successfully used for exploring the genetic basis of complex traits in crops. In this study, we introduced a set of peanut mini-core collection of 146 varieties from International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), which were phenotyped for agronomic traits and resistance to Aspergillus flavus and genotyped by using 26 SSR primers containing 120 loci in the population. Based on the analyses of linkage disequilibrium, population structure and kinship, we performed the genome-wide association mapping. Distribution of LD suggested that the average of the total R² was 0.185, indicating a relative low level of LD between the SSR loci. One hundred sixty-four varieties were grouped into two subgroups by population structure analysis corresponding to Arachis hypogaea ssp. fastigiata and Arachis hypogaea spp. hypogaea, respectively, which was consistent with botanical classification and results of analysis of genetic differentiation. A total of 39 loci were identified to be associated with ten agronomic traits, with 1.50%~20.34% of phenotypic variation explained. A total of 16 loci were associated with Aspergillus flavus infection index and aflatoxin amount, with 5.23%~17.19% of explained phenotypic variation. Of which, 13 common loci were associated with both agronomic traits and resistance to Aspergillus flavus. Furthermore, 63 alleles with increasing effect, 47 alleles with decreasing effect and the varieties carrying them were identified for ten agronomic and two resistance-related traits. This study demonstrates that association mapping is effective to explore genetic basis of important traits in peanut and assist to peanut breeding.

Genetic Dissection of Photosynthetic Pigment Content in Cotton Interspecific Chromosome Segment Introgression Lines

WANG Peng,ZHANG Tian-Zhen

Acta Agron Sin. 2012, 38(06):  947-953.  doi:10.3724/SP.J.1006.2012.00947

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Photosynthesis provides an important foundation for cotton yield and fiber quality. Photosynthetic pigments play an important role in absorption, transfer, and transition of photo energy. In this study, quantitative trait loci (QTLs) mapping was conducted for leaf photosynthetic pigment content using interspecific chromosome segment introgression lines (CSIL). Forty four QTLs (LOD >3) for chlorophyll-a content, chlorophyll-b content, carotenoid content, chlorophyll-a/b ratio value and total chlorophyll content were detected in CSIL population by QTLIciMapping 3.0. Among them, fifteen QTLs were detected in two years. Forty four QTLs were located on fifteen chromosomes including A1(chr.1), A8(chr.8), A9(chr.9), A11(chr.11), A13(chr.13), D1(chr.15), D3(chr.17), D5(chr.19), D6(chr.25), D7(chr.16), D8(chr.24), D9(chr.23), D10(chr.20), D11(chr.21), and D12(chr.26) with the explained phenotypic variation of 1.25%–5.59%. QTLs (qCa-D1-1, qCb-D1-1, qCx.c-D1-1, and qTC-D1-1) influencing chlorophyll-a content, chlorophyll-b content, carotenoid content and total chlorophyll content were located near NAU3714 on chr.D1. It may make a breakthrough in increasing cotton yield through the breeding for high photosynthetic efficiency using the chromosome segment near NAU3714 with modified backcrossing pyramiding breeding (MBPB) technique.

enetic Contribution of Lumai 14 to Novel Wheat Varieties Developed in Shandong Province

GE Hong-Mei,LI Yu-Gang,WANG Rui-Ying,LI Zhen-Qing,WANG Sheng-Jian,GAO Jun-Ling,ZHANG Xue-Yong

Acta Agron Sin. 2012, 38(06):  954-961.  doi:10.3724/SP.J.1006.2012.00954

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Lumai 14 is a semi-dwarf high-yield wheat variety developed in the mid of 1980s, which is also a backbone parent of more than 30 wheat varieties released in China. This study aimed to understand the genetic contribution of Lumai 14 to its derivate varieties and lines at the genomic level. Using 350 SSR markers covering the whole wheat genome, the alleles of Lumai 14 were screened in six Lumai 14 derivants and Yannong 15 (another parent of Qingfeng series). A total of 662 alleles were obtained on the 350 loci, and each locus had 1–5 alleles with an average of 1.9 alleles. The polymorphism information content (PIC) was 0.21. In the UPGMA dendrogram, Jimai 22 and Lumai 14 were clustered together firstly, and further grouped with Qingfeng series. Lumai 20 showed relative large genetic distance to the backbone parent. The derivants of Lumai 14 shared common loci with their parents with percentages of 67.1% (235/350) for Jimai 22, 60.0% (210/350) for Jimai 20, 65.4% (229/350) for Qingfeng 1, and 70.6% (247/350) for Qingnong 2. Most of these loci were assembled on 21 chromosomes, and some of them, such as regions gwm304–barc360–gwm415–barc1 on chromosome 5A and barc196–gdm127–barc123 on chromosome 6D, were shared in six Lumai 14 derivants. In Jimai 22, alleles inherited from Lumai 14 varied among chromosomes, and chromosomes 3A, 4A, 7A, 2B, 4B, 7B, 1D, 3D, and 4D contained more than 70% of Lumai 14 alleles, whereas chromosome 3B showed the lowest percentage of 46%. These alleles from Lumai 14 were mainly distributed in several regions on each chromosome, which proved to harbor genes/QTLs for important traits in QTL analysis and association analysis. Therefore, we conclude that the elite background of Lumai 14 contributed greatly to Jimai 22. In breeding practices, background selection should be highly considered besides the transmission of elite target genes.

Exploring Elite Alleles for Chlorophyll Content of Flag Leaf in Natural Population of Wheat by Association Analysis

LI Wei-Yu,ZHANG Bin,ZHANG Jia-Nan,CHANG Xiao-Ping,LI Run-Zhi,JING Rui-Lian

Acta Agron Sin. 2012, 38(06):  962-970.  doi:10.3724/SP.J.1006.2012.00962

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Elite alleles associated with chlorophyll content of flag leaf in a natural population of winter wheat (Triticum aestivum L.) consisting of 262 accessions were measured at flowering and grain-filling stages under both rainfed and well-watered conditions in two experimental locations in Beijing, China. A total of 169 SSR markers distributed on the 21 chromosomes of wheat were employed to detect the genetic diversity and genetic structure of the population. Association analysis between SSR loci and chlorophyll content trait was performed using TASSEL MLM (mixed linear model) program. The phenotypic allele effect was estimated through comparing the average phenotypic value over accessions with that of “null allele”. A total of 2048 alleles were identified on the 169 SSR loci, and each locus had 2–37 alleles with an average of 12. The polymorphism information contents (PICs) of the SSR loci ranged from 0.008 to 0.936 with an average of 0.628. Forty markers were found to be significantly associated with chlorophyll content (P<0.001) on 22 loci, of which 11 markers showed repeated associations, particularly, loci Xwmc419-1B and Xgwm501-2B had associations for three times. The alleles on loci Xcfa2123-7A, Xgwm232-1D, and Xgwm429-2B exhibited more than 4.0 of phenotypic effect value.

Isolation of GsGST19 from Glycine soja and Analysis of Saline-Alkaline Tolerance for Transgenic Medicago sativa

WANG Zhen-Yu,CAI Hua,BAI Xi,JI Wei,LI Yong,WEI Zheng-Wei,ZHU Yan-Ming

Acta Agron Sin. 2012, 38(06):  971-979.  doi:10.3724/SP.J.1006.2012.00971

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Alfalfa (Medicago sativa L.) is one of the most important leguminous forage crops worldwide. Saline-alkaline stress significantly limits the productivity of alfalfa due to its adverse effects on growth, formation of nodules, and symbiotic nitrogen-fixation capacity, and resulting in the formation of reactive oxygen species (ROS). To protectplants from the toxicity ofreactiveoxygen, aerobic organisms are equipped with an array of defense mechanisms, including one based on glutathione S-transferases (GSTs). Glutathione S-transferases (GSTs) are ubiquitous enzymes that play a key role in stress tolerance and cellular detoxification. The GST gene GsGST19 isolated fromwild type soybean(Glycine soja) under saline-alkaline stress was transformed into alfalfa (Medicago sativa L.). Transgenic alfalfa plants showed 0.52–0.49 times higher levels of GST activity than wild type plants. Transgenic alfalfa grew well in the conditions of 100 mmol L^–1 NaHCO₃, while wild type plants exhibited discoloration and stunted growth, or even death. There were significantly changes in malondialdehyde content and relative membrane permeability caused by saline-alkaline stress in non-transgenic lines compared to transgenic lines (P<0.05). Moreover, compared with non-transgenic, transgenic alfalfa had higher levels of chlorophyll content and root activity under saline-alkali stress conditions. The results indicated that the gene GsGST19 could enhanceresistance to saline-alkaline in alfalfa.

Cloning and Functional Analysis of Magnaporthe oryzae-Induced Promoter OsQ16p in Rice

WANG Guang,WU Zhi-Dan,ZHANG Lei,LIU Feng-Quan,SHAO Min

Acta Agron Sin. 2012, 38(06):  980-987.  doi:10.3724/SP.J.1006.2012.00980

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The qRT-PCR analysis showed that, in Nipponbare (Oryza sativa L. ssp japonica), the expressionof OsQ16 gene was induced by Magnaporthe grisea. The 1 299 bp-fragment of 5'-end of OsQ16 gene, named as OsQ16p,was amplified by PCR from Nipponbare. The plasmids pBIQ16p was constructed by replacing the CaMV35S promoter of pBI121 with the OsQ16p, and transformed into Nipponbare through Agrobacterium-mediated transformation. The analysis of GUS activity and qRT-PCR showed that gus gene could express in transgenic plants and callui. The expression of gus gene in transgenic plants was obviously enhanced by M. grisea. After treatment with the resistance-related signaling molecules SA and MeJA, the GUS activities in transgenic plants were increased by 3.1- and 3.5-fold, respectively. It suggested that M. grisea, SA and MeJA were inductive factors of OsQ16p promoter.

Fine Mapping of Drought Tolerance QTL on Chromosome 2 in Rice

NIE Yuan-Yuan,ZOU Gui-Hua,LI Yao,LIU Guo-Lan,CAI Yao-Hui,MAO Ling-Hua,YAN Long-An,LIU Hong-Yan,LUO Li-Jun

Acta Agron Sin. 2012, 38(06):  988-995.  doi:10.3724/SP.J.1006.2012.00988

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In rice breeding research, drought tolerance (DT) is one of the most important target traits for variety improvement under ever-increasing severe drought situation in the whole world. Identification of the physiological character and grain yield QTLs directly related to DT will provide useful marker information for developing with DT rice variety via marker-assisted selection (MAS). The 87 introgression lines (ILs) selected from 269 advanced backcross introgression population derived from Zhenshan97B/IRAT109 in the Zhenshan97B background were planted in drought facilities for mapping QTLs affecting physiological characters and grain yield under irrigation and drought stress conditions. Twenty QTLs affecting leaf water potential (LWP), canopy temperature (CT), basal culm thickness (BCT), 100-grain weight (HGW), spikelets number per panicle (SN) and spikelets density were identified, which could be grouped into three types based on their behaviors. Type I included seven QTLs which were detected under both conditions; type II consisted of four QTLs which were mapped only in the control condition; and type III consisted of two QTLs which were induced by drought and detected only under the stress. The seven QTLs detected under both environments and the two QTLs detected under drought stress could directly contribute to DT and be used in rice breeding for DT by MAS.

Genomic Variation in F₁ Hybrid and Amphidiploid between Aegilops tauschii and Secale cereale

LI Suo-Ping,ZHANG Da-Le,WANG Xiu-E,QI Zeng-Jun,LIU Da-Jun

Acta Agron Sin. 2012, 38(06):  996-1002.  doi:10.3724/SP.J.1006.2012.00996

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Synthetic amphidiploids play an important role in genetic study and plant breeding. To understand the molecular mechanism of fertility improvement and cytological stability in amphidiploid, we analyzed the fertility, genomic variation, and cytology of the F₁ hybrid and S₁ to S₄ amphidiploid progenies from the cross between Aegilops tauschii and Secale cereale by means of microscopic observation and molecular markers (ALFP and MASP). The percentage of plants with chromosome number of 2n = 28 increased from 57.1% to 92.5% in the amphidiploid progenies. The bivalent in pollen mother cells (PMCs) at meiosis I stage increased from 11.70 to 12.25 averagely, and the mean rate of seed setting was enhanced from 24.5% to 51.3% in the amphidiploid progenies (2n=28). Genomic variation in the F₁ hybrid and the amphidiploids was detected using AFLP markers digested by EcoRI/Mse I (E-M) and Pst I/Mse I (P-M), which could primarily amplify repetitive and low-copy sequences, respectively. The results showed that the genomic variation occurred mainly in F₁ hybrid with dominant form of sequence elimination. The loss percentages in F₁ plants were 70.00% at E-M locus and 52.95% at P-M locus for the Ae. tauschii banding pattern and 96.88% at E-M locus and 81.64% at P-M locus for the S. cereale banding pattern. The result of MSAP analysis showed that the cytosine methylation alterations, mainly methylated, only occurred in the F₁ hybrids and the S₁ amphidiploids. In S₂ to S₄ amphidiploids, no methylation was observed.

Microsatellite Markers Linked to Stem Rust Resistance Gene Sr33 in Wheat

HAN Jian-Dong,LI Wei-Hua,CAO Yuan-Yin,GONG Zhi-Yuan,YAO Qiang

Acta Agron Sin. 2012, 38(06):  1003-1008.  doi:10.3724/SP.J.1006.2012.01003

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Gene Sr33 confers resistance not only toUg99, but also to most Puccinia graminis f.sp. tritici races in China. A mapping population, consisting of 161 F₂ plants and F_2:3 families derived from the crossbetween susceptible wheat cultivar “McNair701” and a Tetra Canthatch/Triticum tauschii line carrying single Sr geneSr33, were inoculated with chinese prevalent race 34MKG to locate this resistance gene using microsatellite markers. A total of 57 microsatellite markers covering chromosome 1D were used in bulked segregation analysis (BSA) based on resistance identification at seedlings stage. Two codominant markers, Xbarc152 and Xcfd15, were obtained, which were located at both sides of Sr33. The genetic distances of Xbarc152 and Xcfd15 to the target gene were 2.4 cM and 2.1 cM respectively. These closely linked markers can be used in marker-assisted selection of wheat breeding against stem rust disease.

Characterization of Interaction between Wheat Roots with Different Resistance and Heterodera filipjevi

CUI Lei,GAO Xiu,WANG Xiao-Ming,JIAN Heng,TANG Wen-Hua,LI Hong-Lian,LI Hong-Jie

Acta Agron Sin. 2012, 38(06):  1009-1017.  doi:10.3724/SP.J.1006.2012.01009

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Heterodera filipjevi is a newly identified pathogenic species of cereal cyst nematode that invades wheat (Triticum aestivum L.) in central China. A two-year field test (2009–2011) conducted in Xuchang County, Henan Province, China, where H. filipjevi has severely damaged wheat for several years, demonstrated that the wheat-rye (Secale cereale L.) chromosome substitution line 6R(6D) (carrying gene CreR for resistance to Heterodera spp.) was highly resistant (HR) to the nematode. The wheat cultivar Taikong 6 was moderately resistant (MR) and its parental cultivar Yumai 49 was highly susceptible (HS). Attraction of H. filipjevi juveniles to root tips of wheats differed in resistance to H. filipjevi was studied using Pluronic F-127 gel as a medium. Although root tips from wheat cultivars with different resistance were able to attract juveniles of nematode alone, the number of juveniles around the root tip from line 6R(6D) was obviously less than that from Taikong 6 (MR) and Yumai 49 (HS) when they were challenged together concurrently by H. filipjevi. The juveniles were capable to penetrate into wheat roots regardless of their resistance as revealed by acid fuschin-sodium hypochlorite staining of infected roots. However, significantly smaller number of nematodes in the roots of 6R(6D) and Taikong 6 were observed compared to those of Yumai 49 at later stage of wheat-H. filipjevi interaction. These findings demonstrate that some of the H. filipjevi juveniles are not able to continue to reproduce themselves although they can penetrate the roots of resistant wheat cultivars 6R(6D) and Taikong 6. The results from this study provide experimental evidence on mechanism of host resistance to H. filipjevi.

Diversity of SSR Marker in 175 Wheat Varieties from Huang-Huai Winter Wheat Region and Its Association with Plant Height and Yield Related Traits

WU Yu-Guo,WU Cheng-Lai,QIN Bao-Ping,WANG Zhen-Lin,HUANG Wei,YANG Min,YIN Yan-Ping

Acta Agron Sin. 2012, 38(06):  1018-1028.  doi:10.3724/SP.J.1006.2012.01018

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To make advances in wheat breeding, it is important to study germplasm diversity of Huang-huai winter wheat, and identify SSR markers associated with important agronomic traits, including plant heightand yield related traits. In this study, we selected 175 historical winter wheat varieties planted in Huang-Huai winter wheatarea and 108 pairs of SSR markers evenly distributed on the chromosomes of wheat to reveal the genetic diversity. A total of 448 alleles of loci were detected in the experimental varieties. The average alleles per locus were 4.15, which varied from 2 to 14. Thepolymorphism information content (PIC) value ranged from 0.075 to 0.869, with an average of 0.560. Cluster analysis showed that most of the varieties with the common parents, bred by the same breeders and planted in the same area were clustered together. A total of 23 were markers significantly (P<0.01) associated with plant height and yield related traits, among which threewere very significantly(P<0.001) associated with the traits.The markerswmc128 (1B) and wmc236 (3B) could explain 10.5% and 8.0% of variation in the number of spikelets(P<0.001), respectively.And, Xgwm129 (2B) was significantly (P<0.001) associated with 1000- kernel weight, whose phenotypic variation explaining rate was as high as 19.3%.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Genetic Diversity of Agronomic Traits and Association Analysis with SRAP Markers in Flue-Cured Tobacco (Nicotiana tabacum) Varieties from Home and Abroad

ZHANG Ji-Shun,WANG Ren-Gang,YANG Chun-Yuan,WU Chun,SHI Yue-Wei,WANG Zhi-Hong,WANG Yi,REN Xue-Liang

Acta Agron Sin. 2012, 38(06):  1029-1041.  doi:10.3724/SP.J.1006.2012.01029

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To assess the genetic diversity of flue-cured tobacco germplasm, developing the elite gene resources, we selected 258 flue-cured tobacco varieties from home and abroad to investigate 13 agronomic traits in two locations with different environments. The genetic diversity and population structure were analyzed with 597 SRAP markers produced by 16 primer combinations. Different association models were tested and the most effective model was chosen for the population to make the association analysis between agronomic traits and SRAP markers. The results revealed that abundant phenotypic and genetic diversity existed in the flue-cured tobacco germplasm accessions. Flue-cured tobaccos from China showed less diversity than those from other countries. The accessions could be divided into seven subpopulations and the classification result was significantly correlation with geographic origins and hereditary relationship. Population structure within exotic varieties was multiplex. MIM_Q+K and MIM_PCA+K were effective models for association analysis between agronomic traits and SRAP markers. A total of 18 markers were found to be significantly associated (–log P>2, P<0.01) with six agronomic traits. Among them, markers associated with plant height (me1/em9-16, me1/em9-36, me4/em9-1), leaf number (me1/em2-14, me7/em5-34), bottom leaf width (me6/em2-6) and lumbar leaf length (me2/em6-15) were stably detected in different environments. This study provides evidence for identification of elite flue-cured tobacco germplasm, prediction of candidate gene and marker-assisted selection.

Effects of Exogenous Spermidine on Physiological Regulatory of Maize after Waterlogging Stress

ENG Shan-Shan,WANG Qun,ZHANG Yong-En,LI Chao-Hai,LIU Tian-Xue,ZHAO Long-Fei,LIU Huai-Pan

Acta Agron Sin. 2012, 38(06):  1042-1050.  doi:10.3724/SP.J.1006.2012.01042

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Apot experiment with two maize varieties DH662 and XD20 was conducted to studythe regulatory effects of exogenous spermidine on photosynthesis and physiological characteristics and yield of maize after waterlogging stress. The results showed that the average yield of DH662 and XD20 was increased by 12.9% and 10.8% after topdressing exogenous spermidine. The effect of waterlogging in different growth stages on maize was different. The treatment at seedling to jointing stage showed more influence on the two varieties. And the effects of exogenous spermidine was best at seedling to jointing stage. The topdressing of exogenous spermidinecould improve the utilization efficiency of light energy in different growth stages, and P_n, G_s, L_s, F_v/F_m, Φ_PSII, q_P of leaves, but reduce C_i and q_N. The activities of SOD and CAT in DH662 were increased significantly by 14.5% and 19.9%, while those in XD20 were increased significantly by 4.6% and 18.2% as compared with the waterlogging treatment. And the average activity of IDH and SDH in both the two cultivars was increased by 26.1% and 19.6%, while the activity of APX was not increased significantly. The exogenous spermidine could repress the cell membrane oxidation. The average root activity in DH662 and XD20 was increased by 12.9% and MDA content was decreased by 23.9%. Therefore, the topdressing of exogenous spermidine improves the physiological functions of leaves and roots, resulting in lower yield losses caused by waterlogging, but the sensitivity of different varities and different growth stages to Spd was different.

Effect of Tillage Mode on Diurnal Variations of Water Potential and Chlorophyll Fluorescence Characteristics of Flag Leaf after Anthesis and Water Use Efficiency in Wheat

CHU Peng-Fei,YU Zhen-Wen,WANG Dong,ZHANG Yong-Li,SHI Yu

Acta Agron Sin. 2012, 38(06):  1051-1061.  doi:10.3724/SP.J.1006.2012.01051

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Water resource shortage has become the urgent problem limiting wheat (Triticum aestivum L.) production in Yellow-Huaihe-Haihe Rivers Plain of China. A crucial target of wheat production is to develop water-saving agriculture to reduce irrigation water and increase the water use efficiency (WUE). The objective of this study was to understand the effects of tillage practices on soil moisture content, water potential and consumption in plants, diurnal variation of chlorophyll fluorescence characteristic in flag leaf after anthesis, and grain yield in wheat under flexible irrigation conditions. A high-yielding wheat cultivar, Jimai 22, was continuously planted in the same plot across two growing seasons from 2007 to 2009. Five tillage modes were established with flexible irrigation after measuring soil moisture, which were strip rotary tillage (SR), strip rotary tillage after subsoiling (SRS), rotary tillage (R), rotary tillage after subsoiling (RS), and plowing tillage (P). The moisture contents of soil layers within 0–200 cm were measured at sowing, jointing, and anthesis stages. In the 2008–2009 growing season, the diurnal variation of water potential and chlorophyll fluorescence characteristic in flag leaf were measured at 22 d and 24 d after anthesis. The SRS and RS treatments had the lowest moisture content in different soil layers of 60–200 cm below surface. The result indicated that subsoiling had the effect to promote water absorption of wheat in deep soil layers. From anthesis to maturity, the water consumption of SRS treatment exhibited the highest amount and ratio from soil and the lowest ratio from precipitation and irrigation. Compared with SR treatment, SRS treatment had higher water potential from 6:00 to 18:00 and larger values of F_v/F_m and Φ_PSII of flag leaf from 8:00 to 14:00. Clearly, subsoiling was favorable to keep high physiological activity from mid to late filling stage. The positive effect of subsoiling was confirmed by the comparison between RS and R treatments. Among the five tillage treatments, SRS produced the highest grain yield of 9 516.48 kg ha⁻¹ in 2007–2008 growing season and 8 957.92 kg ha⁻¹ in 2008–2009 growing season. The yield level of RS had no significant difference from that of SRS treatment. In contrast, SR and R treatments showed the lowest yields in all treatments. As for WUE, the ranking sequence of treatments was SRS > RS > P > SR or R. Therefore, we recommend SRS as the best tillage practice for high yield and water saving in wheat producing areas with similar ecological conditions to the experiment.

Effects of Partial Root Zone Irrigation on Leaf Photosynthetic Curves and Chlorophyll Fluorescence Parameters in Naked Oat

LIN Ye-Chun,ZENG Zhao-Hai,REN Chang-Zhong,LI Zhi-Jian,GUO Lai-Chun,YANG Xue-Chao,WANG Chun-Long,QIAN Xin,HU Yue-Gao

Acta Agron Sin. 2012, 38(06):  1062-1070.  doi:10.3724/SP.J.1006.2012.01062

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The objective of this study was to provide experimental evidence for photosynthetic mechanism under drought stress and practical technique of water-saving irrigation in naked oat (Avena nuda L.). In a pot experiment with instrument to control root zone irrigation and water amount, the effects on relative chlorophyll content (SPAD), photosynthetic curves, and chlorophyll fluorescence parameters were compared among irrigation models of alternative partial root zone irrigation (APRI), fixed partial root zone irrigation (FPRI), and conventional total root zone irrigation (CTRI). Compared to CTRI, partial root zone irrigation, including APRI and FPRI treatments, decreased leaf SPAD, net photosynthetic rate (P_n), and carboxylation efficiency (CE); however, APRI had no obvious effects on reducing initial quantum efficiency (α), maximum photochemical efficiency (F_v/F_m), actual photochemical efficiency of PSII (Ф_PSII), apparent electron transport rate (ETR), and photochemical quenching coefficient (q_P). The leaf SPAD of APRI was significantly enhanced compared to that of FPRI (P<0.05), and the maximum net photosynthetic rate (P_max), α, light saturation point (LSP), light use efficiency (LUE), C_i/C_a, CE, CO₂ saturation point (C_i,sat), F_o, F_m, Ф_PSII, ETR, q_P, and NPQ were all higher in APRI than in FPRI. The reduction of P_n in partial root zone irrigation treatments resulted from stomatal factors, and structural damage of photosynthetic system II (PSII) was found in FPRI treatment. Clearly, partial root zone irrigation can improve the tolerance ability of naked oat against drought stress; particularly, APRI has the effect to maintain higher P_n than FPRI.

Effect of Interaction of Waterlogging and High Temperature after Anthesis on Photosynthetic Characteristics of Flag Leaf and Yield in Winter Wheat

WU Jin-Dong,LI Jin-Cai,WEI Feng-Zhen,ZHANG Yi,WU Wen-Ming

Acta Agron Sin. 2012, 38(06):  1071-1079.  doi:10.3724/SP.J.1006.2012.01071

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Waterlogging and high temperature are main stress factors during late growing period of winter wheat (Triticum aestivum L.) in Yangtze Valley region of China. To understand the effect of interaction of waterlogging and high temperature on photosynthetic characteristics and grain yield of wheat, we carried out a pot experiment, using the variety of Yannong 19, in continuous growing seasons from 2009 to 2011. At grain-forming (5–8 d after anthesis) and milking (15–18 d after anthesis) stages, waterlogging (1 cm of surface water layer), high temperature (35±2°C of daytime/25±2°C of nighttime), and waterlogging + high temperature stresses were imposed to wheat plants, separately. Waterlogging, high temperature, and both stresses showed significantly effects on photosynthetic characteristics of flag leaf and yield reducing photosynthetic rate (P_n), chlorophyll content (SPAD reading), stomatal conductance (G_s), and transpiration rate (T_r); enhancing intercellular CO₂ concentration (C_i); and declining grain number per spike, 1000-grain weight, and grain yield. However, in the case, spike number per pot was not affected significantly. Thus, the effects of waterlogging and high temperature on P_n did not result from stomata factor of flag leaf. The average relative injury rates (RIR) of yield were 37.7% for waterlogging + high temperature treatment, 21.1% for waterlogging treatment, and 17.6% for high temperature treatment. Stress showed higher RIR at grain forming stage (30.8%) than at milking stage (20.1%). There was significant interaction between waterlogging and high temperature, and grain-forming stage was more sensitive to the interaction than milking stage.

Characteristics of Accumulation, Transition and Distribution of Assimilate in Summer Maize Varieties with Different Plant Height

LI Li-Li,ZHANG Ji-Wang,DONG Shu-Ting,LIU Peng,ZHAO Bin,YANG Jin-Sheng

Acta Agron Sin. 2012, 38(06):  1080-1087.  doi:10.3724/SP.J.1006.2012.01080

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Three types of summer maize varieties, low-plant height cultivar Denghai 661 (DH661), medium-plant height cultivar Chaoshi 3 (CS3), high-plant height varieties Ludan 981 (LD981) and Xianyu 335 (XY335) were need in this study. The results showed that the difference of dry matter accumulation for different varieties was mainly manifested after flowering stage. Along with the increase of the plant height, dry matter accumulation after flowering stage reduced. The carbon distribution rate in lower part of stem in low-plant height cultivar was lower than that in the high-plant height varieties. The experiment using tracer of isotope ¹³C showed that the leaves in different parts of plant in different varieties had different contributions to grain yield. With the decrease of the plant height, the dry matter transition of middle and bottom leaves was increased, and that of top leaves was decreased. The relative contribution of upper leaves in high-plant height varieties to grains was higher than that in low-plant height cultivar that of lower leaves in high-plant height varieties was lower. There were differences in the contribution to grain yield of different parts of leaves before or after flowering. For the dry matter transition, the top leaves of LD981 and XY335, as well as the middle leaves of DH661 were the highest.

Effects of Nitrogen Fertilization on Chlorophyll Fluorescence Parameters of Flag Leaf and Grain Filling in Winter Wheat Suffered Waterlogging at Booting Stage

WU Wen-Ming,CHEN Hong-Jian,LI Jin-Cai,WANG Shi-Ji,WEI Feng-Zhen,ZHOU Xiang-Hong

Acta Agron Sin. 2012, 38(06):  1088-1096.  doi:10.3724/SP.J.1006.2012.01088

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Waterlogging has great influence on yield of winter wheat in some areas of China. Nitrogen (N) application is believed to be able to improve photosynthesis of flag leaf and increase final yield. To understand the response of chlorophyll fluorescence parameters of wheat flag leaf to waterlogging stress at booting stage and the effect of N fertilization, we carried out a field experiment from Autumn of 2008 to Summer of 2010 using winter wheat cultivar “Wanmai 54”. The waterlogging stress was imposed for 7 d at booting stage. Four N treatments were designed for waterlogging stress and the control (normal watering) of which N application rate was 240 kg ha^{-1 in all treatments but with different proportions at land preparation, jointing, and booting stages. The results showed that the maximum chlorophyllcontent of flag leaves occurred at the booting stage. Under normal watering condition, F}_v/F_m, F_v/F_o, and q_p showed “high-low” variation, and the maximum values were observed between May 3 and May 11. However, under waterlogging stress at booting stage, F_v/F_m, F_v/F_o, and q_p showed “low-high-low” curve. Compared to control treatment, waterlogging at booting stage significantly decreased F_v/F_m, F_v/F_o, q_p, and Φ_PSII (P<0.05), and NPQ significantly increased (P<0.05). With the delay of N fertilization, F_v/F_m, F_v/F_o, q_p, and Φ_PSII increased significantly compared to the forward N fertilization treatments. Postpone of N supply improved photosynthetic capacity by increasing photosynthetic pigment contents, and enhancing photosynthetic efficiency under water deficit. The chlorophyllcontent was positively correlated with F_v/F_m, q_p, and Φ_PSII, (P<0.05), but negatively correlated relationship with NPQ (P<0.01). From the chlorophyll fluorescence rapid light curves, we found that, compared to normal watering, waterlogging stress at booting stage significantly decreased the maximal relative electron transport rate(ETR_max), initial slope (α), and half saturation point of light intensity (E_k). Postpone of N fertilizer application alleviated the photodamage to PSΙΙ caused by water stress, and the compensation effect of late N fertilization occurred earlier than that of early N fertilization, which resulted in longer filling period, higher mean filling rate, and ultimately increased 1000-grain weight

Effects of Nitrogen Fertilizer Management on Yield and Nitrogen Use Efficiency of Eryou 498 in Triangle-Planted System of Rice Intensification

YANG Zhi-Yuan,HU Rong,SUN Yong-Jian,XU Hui,XU Yuan-Ming,MA Jun

Acta Agron Sin. 2012, 38(06):  1097-1106.  doi:10.3724/SP.J.1006.2012.01097

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Hybrid rice Eryou 498 was used to investigate the effects of nitrogen (N) fertilizer management on leaf area, photosynthetic rate in productive phase, and also dry-matter accumulation and its transportation in triangle-planted system of rice intensification (TSRI) with appropriate seedling age and density. At the same time, the effects of dry-matter accumulation before anthesis and its transportation and dry-matter accumulation after anthesis on yield formation were also studied to explore a N fertilizer management which could both increase yield and reduce the waste of N. The results showed that in TSRI N fertilizer management had significant effects on leaf area index (LAI) and photosynthetic rate except the LAI in waxy ripening stage; with the increase of N rate and postponing N application, net photosynthetic rate in flag leaf in full heading stage and waxy ripe stage increased significantly; LAI in productive phase exhibited a parabola mostly with the increase of N rate and postponing N application. In TSRI, N rate and ratio of application both enlarged total glumes to increase yield. At the same time, N rate enlarged 1000-grain weight and ratio of application improved seed-setting rate to increase yield respectively. In TSRI, dry-matter accumulation before anthesis, dry-matter of transportation, and transportation rate of dry-matter had significantly positive correlation with yield respectively. The treatment which N rate was 150 kg ha^-1 and panicle fertilizer was 30% of the whole N fertilizer enlarged dry-matter accumulation before anthesis and dry-matter of transportation significantly to reach maximum yield. It also improved N agronomy efficiency and N physiology efficiency significantly, so it was the best combination which could both increase yield and reduce the waste of N fertilizer to the maximum degree.

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Effect of Nitrogen Application Level on Nitrogen Use Efficiency in Wheat and Soil Nitrate-N Content under Bed Planting Condition

FENG Bo,KONG Ling-An,ZHANG Bin,SI Ji-Sheng,LI Sheng-Dong,WANG Fa-Hong

Acta Agron Sin. 2012, 38(06):  1107-1114.  doi:10.3724/SP.J.1006.2012.01107

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The variation of nitrate-N content in soil was observed in winter wheat under bed planting, and the N use efficiency and yield were compared between cultivation patterns of bed planting and flat planting. The amount of N accumulation in wheat plant, N harvest index, and grain yield of wheat were increased with the increase of N application rate, but the N use efficiency and the soil N contribution tended to decrease. At low N application rate (0–66 kg ha^-1), the possibility of nitrate-N leaching was declined with no massive accumulation at 0–100 cm soil layer. At high N application rate (165–264 kg ha^-1), the content of nitrate-N in 60–100 cm soil layer increased and began to move down in the soil. Cultivation pattern had an effect on N use efficiency, of which bed planting showed higher N use efficiency and wheat yield than flat planting. In flat planting pattern, nitrate-N was mostly accumulated in soil of 60–80 cm depth, which was shallower than that in flat planting (80–100 cm).Cultivation pattern had larger effect on N use efficiency than N application rate; whereas, N application had larger effect on N harvest index, grain yield, and harvest index than cultivation pattern. Under the experimental condition, high N use efficiency and N harvest index were observed in N application treatment of 165 kg ha^-1, and the N use efficiency of wheat was significantly higher in bed planting (45.32–47.25%) than in flat planting (35.75–36.41%). The highest grain yields were 8 078.31 kg ha^{-1 in flat planting and 8 212.27 kg ha-1 in bed planting, which were both obtained in N application treatment of 264 kg ha-1}.

Effect of Stresses on Leaf Cuticular Wax Accumulation and Its Relationship to Expression of OsGL1-Homologous Genes in Rice

ZHOU Ling-Yan,JIANG Da-Gang,LI Jing,ZHOU Hai,CAO Wei-Wei,ZHUANG Chu-Xiong

Acta Agron Sin. 2012, 38(06):  1115-1120.  doi:10.3724/SP.J.1006.2012.01115

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The outermost surfaces of land plants are covered with a cuticular wax layer which plays a very critical role in defense against biotic and abiotic stresses. GLOSSY1 (GL1) is a wax biosynthesis related gene and OsGL1 is a homologous gene of GL1. In this study, we discussed the leaf cuticular wax accumulation and the relationship between the leaf cuticular wax accumulation and the expression of OsGL1 in rice treated with stresses, including 200 mmol L^-1 NaCl, 12% PEG, 1.0% H₂O₂, high temperature and low temperature in their seedling stages. The scanning electron microscopy and the cuticular wax content analysis showed that the cuticular wax accumulation on leaves significantly increased under 12% PEG, 1.0% H₂O₂ and low temperature treatments. However, the cuticular wax accumulation on leaves declined slightly under NaCl and high temperature treatments. Results of RT-PCR analysis suggested that the expression of OsGL1 under stresses was associated with the accumulation of cuticular wax on leaves.

Effects of Winter Ryegrass Planting on Soil Heavy Metal Content and Accumulation and Distribution in Different Organs of Late Rice in Six Paddy Soils

TANG Hai-Ming,TANG Wen-Guang,XIAO Xiao-Ping,LUO Zun-Chang,ZHANG Fan,WANG Ke,YANG Guang-Li

Acta Agron Sin. 2012, 38(06):  1121-1126.  doi:10.3724/SP.J.1006.2012.01121

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Investigation of the effects of winter ryegrass planting on soil heavy metal content and its accumulation and distribution in different organs of late rice in double-rice cropping paddy field with different paddy soil types will play an important role on rice quality safety and environmental security assessment of paddy field. Based on seven years long-term located experiments in paddy fields, we analyzed the effects of winter ryegrass planting on soil heavy metal content and its accumulation and distribution in rice in double-rice cropping paddy field with different paddy soil types including granitic sandy soil (GSS), grey clayey soil (GCS), purple clayey soil (PCS), red yellow clayey soil (RCS), yellow clayey soil (YCS) and alluvial sandy soil (ASS). The results showed that the Cd content in GCS was significantly higher than that in other treatments, while the Pd content in YCS was significantly higher than that in other treatments. RCS had the highest Hg content with 0.029 mgkg^-1, and the highest As contents with 29.5 mgkg^-1 in YCS. The contents of Cd, Pb and As in late rice showed an order as root > stem and leaves > brown rice. Cd contents in root, stem and leaves, and brown rice planting in RCS were significantly higher than those in other treatments. And the highest Pb and As contents in root of rice planting in YCS was 33.0 and 119.5 mgkg^-1, respectively. Meanwhile, the Hg and As contents in rice stem and leaveswere significantly higher in ASS than in other soil types. Our results clearly demonstrated that the heavy metal content of brown rice was decreased, and the quality of late rice was ultimately improved under YCS condition.

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Expression of Potassium Metabolism-Related Gene in Tobacco

XIA Kai,XU Shuang-Hong,WANG Xiang,DAI Lin-Jian,LI Peng-Fei,LUO Jian-Xing,QI Shao-Wu,YANG Qiong,ZHOU Qing-Ming

Acta Agron Sin. 2012, 38(06):  1127-1134.  doi:10.3724/SP.J.1006.2012.01127

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The quality of flue-cured tobacco in production is currently limited by low potassium level in leaf. A simple and effective way to alleviate the supply of potassium in soil is screening the potassium-enriched flue-cured tobacco types. In the experiment, the tobacco seedlings were cultured in nutrient solution, and then replanted in sand soil. To investigate the potassium metabolism related gene’s expression and kinetic parameters of potassium uptake and utilization with six different lines including five potassium-enriched genotypes of K2, K3, K5, K7, and K9 and a conventional genotype of K326. The results showed that the tobacco lines K2, K7, and K9 were typical potassium-enriched genotypes, TORK1 and NtTPK1 out of 12 genes performed high expression. The ability of potassium absorption of K3, K5, K9, K7, and K2 was significantly stronger than that of K326. The potassium absorption abilities of potassium -enriched types of K9, K2, K7, K3, and K5 were stronger but their use efficiencies were lower than these of K326 in high potassium environment, and higher in low potassium environment, especially for the genotypes K2, K7, and K9.

Relationships and Genetic Diversity of Colored-Grain Wheat Detected by SSR Markers

HUANG Wei,YANG Min,QIN Bao-Ping,WANG Zhen-Lin,WU Yu-Guo,SUN Lan-Zhen,YIN Yan-Ping

Acta Agron Sin. 2012, 38(06):  1135-1139.  doi:10.3724/SP.J.1006.2012.01135

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To reveal the relationship and genetic diversity of colored-grain wheat, we analyzed 18 varieties (lines) with red, purple, blue, and black seed coats using 305 polymorphic SSR markers. A total of 1084 alleles were detected with 3.6 alleles per locus. The allele numbers in seven homoeologous groups (HG) were aligned as HG3>HG2>HG1>HG4>HG5>HG7>HG6 in red and purple wheat and HG3>HG2>HG1 and HG 4>HG5>HG7>HG6 in black and blue wheat. The polymorphic information content (PIC) values in the seven homoeologous groups were similar, which were 0.525–0.543 in red and purple wheat and 0.517–0.545 in black and blue wheat. Among the 18 colored-grain varieties (lines), genetic difference was significant (P = 0.0001), and the genetic similarity coefficients ranged from 0.41 to 0.76. According to UPGMA analysis, the 18 varieties (lines) were classified into six groups, which were in relation to variety kindred and geographic distance.