Table of Content

12 December 2013, Volume 39 Issue 12

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Molecular Mapping of Powdery Mildew Resistance Gene pmCH83 in a Putative Wheat–Thinopyrum intermedium Cryptic Introgression Line

SUN Cui-Hua,HOU Li-Yuan,GUO Hui-Juan,ZHANG Xiao-Jun,JIA Ju-Qing,LI Xin,ZHAN Hai-Xian,CHANG Zhi-Jian

Acta Agron Sin. 2013, 39(12):  2107-2114.  doi:10.3724/SP.J.1006.2013.02107

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Wheat introgression line CH09W83 is immune or highly resistant to wheat powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) pathotypes E09, E20, E21, E23, E26, Bg1, and Bg2 at seedling stage in China. This line was derived from the cross between wheat–Thinopyrum intermedium line TAI7047 (resistant) and wheat cultivar Jintai 170 (susceptible). To identify the Bgt resistance gene(s) in CH09W83, we developed segregating populations (F₂, F_2:3, and BC₁) by crossing/backcrossing CH09W83 with susceptible wheat parents. The result of genetic analysis showed that the adult resistance to Bgt E09 in CH09W83 was controlled by a single recessive gene, which was tentatively designated as pmCH83. Using the F₂ population of Taichang 29 (susceptible) ´ CH09W83 and 658 pairs of SSR primers, four codominant SSR markers, i.e., Xgwm193, Xgwm251, Xwmc652, and Xgpw7272, were identified to be linked with pmCH83 according to bulked segregant analysis, and the genetic distances between the target gene and flanking markers were 4.3 cM to Xgwm251 and 3.8 cM to Xwmc652. Using Chinese Spring nullitetrasomic and ditelosomic lines, pmCH83 was located on chromosomal arm 4BL of wheat. In combination with evidence of bivalent pairing at metaphase I and GISH, CH09W83 is probably a cryptic wheat–Th. intermedium translocation. Based on pedigree analysis and linkage map, we deduced that pmCH83 is a novel Bgt resistance gene originating from Th. intermedium.

Database Mining, Bioinformatics, Cloning and Expression Analyses of D Subfamily bZIP Genes in Maize

YANG Yan-Ge,Lü Wei-Tao,SUN Dong-Mei,LING Yi,DENG Xin

Acta Agron Sin. 2013, 39(12):  2115-2122.  doi:10.3724/SP.J.1006.2013.02115

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Basic leucine zipper (bZIP) is unique transcription factor family among eukaryotes, playing important roles in gene expression and regulation in higher plants. Here we reported the finding of 25 full length cDNA sequences encoding D subfamily of bZIP factors in maize from a database mining on whole genome level. The analysis of bioinformatics, chromosome distribution and classification of Possible Groups of Orthologous (PoGO) suggested the existence of diverse alternative splicing in some of these genes, which was supported by the sequencing results of the cloned cDNAs. The expression pattern of three representative genes in response to ABA and drought stress were examined by quantitative RT-PCR, and the results revealed different regulations of ABA on the expression of these genes. Our results suggest that D subfamily of bZIP genes in maize might involve in ABA signal pathway.

Gene Differential Expression of a Green-revertible Albino and High-tillering Dwarf Mutant hfa-1 by Using Rice Microarray

GUO Tao,HUANG Yong-Xiang,LUO Wen-Long,HUANG Xuan,WANG Hui,CHEN Zhi-Qiang,LIU Yong-Zhu

Acta Agron Sin. 2013, 39(12):  2123-2134.  doi:10.3724/SP.J.1006.2013.02123

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Phenotype of the hfa-1 mutant characterized by green-revertible albino and high-tillering dwarf is controlled by a single recessive nuclear gene hw-1(t), which encodes a chloroplast protein containing the mitochondrial alternative oxidase (AOX) structure and involves in the electron transport chain of chloroplast respiratory regulating biosynthesis of carotenoid and carotenoid-related secondary metabolic pathways. In this study, expression analysis of genes involved in carotenoid biosynthesis and carotenoid-related plant hormones biosynthesis andgene-expression profiling were conducted before and after the turning-green of hfa-1 mutant. the results displayed that expression levels of genes involved in carotenoid biosynthesis and carotenoid-related plant hormones (GA, ABA and SL) biosynthesis were decreased in the albino leaves of hfa-1, suggesting that mutation of hw-1(t) inhibits the biosynthesis of carotenoid and has an impact on carotenoid-related secondary metabolic pathways. Gene expression profiling and functional classification showed that genes related to physiological processes in response to photoeynthesis, endogenous stimulus and stress were differently expressed in hfa-1 before and after its turning-green. Expression of genes encoding proteins related to the electron transport complex Cytb6/f were up-regulated significantly, indicating that Cytb6/f would provide some compensation in electron transport and redox of plastoquinone in the hfa-1 mutant.

Characteristics of PP2C Gene Family in Foxtail Millet (Setaria italica)

MIN Dong-Hong,XUE Fei-Yang,MA Ya-Nan,CHEN Ming,XU Zhao-Shi,LI Lian-Cheng,DIAO Xian-Min,JIA Guan-Qing,MA You-Zhi

Acta Agron Sin. 2013, 39(12):  2135-2144.  doi:10.3724/SP.J.1006.2013.02135

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PP2Cs are a group of monomeric serine/threonine protein phosphatases, which play an important role in regulation of hormone signaling pathways such as abscisic acid (ABA), jasmonic acid (JA) and salicylic acid (SA) in eukaryotes. In this study, we identified 80 candidate PP2C genes from foxtail millet genome via sequence alignment, and cluster analysis showed that PP2Cs in foxtail millet were divided into 12 subfamilies (subfamily A, B, C, D, E1, E2, F1, F2, G, H, I, and J). Foxtail millet and Arabidopsis share A, B, C, D, E1, E2, F1, F2, G, H, and I, while subfamily J is only in foxtail millet and subfamily L is only in Arabidopsis. Ten members of subfamily A in foxtail millet were named as SiPP2CA1–10, and gene expression profiles showed that the expression of these genes was induced by ABA, drought, high salt, cold and low nitrogen stresses. Among them, SiPP2CA6 and SiPP2CA8 showed high expression level in all treatments. Promoter analysis identified a variety of cis-acting elements involved in stress responses in promoter region of members in subfamily A, and a specific element responding to low nitrogen stress in SiPP2CA5, SiPP2CA6, SiPP2CA7, and SiPP2CA8. Further study demonstrated that SiPP2CA8mainly expressed in root, and its expression remained at high level under low nitrogen stress. Subcellular localization showed that SiPP2CA8 waslocalized in cytomembrane, cytoplasm and nucleus. Bimolecular fluorescence complementation (BiFC) assay demonstrated that SiPP2CA8 interacted with an ABA receptor like protein, SiRCAR3 (gene locus Si018317m.g), in cytomembrane, cytoplasm and nucleus. These results suggested that SiPP2CA8 may participate in ABA signaling pathway in foxtail millet.

Classification of Glutamine Synthetase Gene and Preliminary Functional Analysis of the Nodule-Predominantly Expressed Gene GmGS1β2 in Soybean

WANG Xiao-Bo,TENG Wan,HE Xue,TONG Yi-Ping

Acta Agron Sin. 2013, 39(12):  2145-2153.  doi:10.3724/SP.J.1006.2013.02145

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The purpose of this study was to analyze the evolution, classification and tissue expression specificity of soybean cytosolic glutamine synthetase genes. Glutamine synthetase (GS) proteins from 12 species were downloaded from phytozome database, and used for phylogenetic analysis. The GSs were divided into two groups, cytosolic glutamine synthetase (GS1) and plastidic glutamine synthetase (GS2) based on the maximum likelihood of MEGA 5.10 software. The GS1 group was further divided into five subgroups, including three dicotyledons subgroups (I, II, and III), lower plants subgroup (IV) and monocotyledons subgroup (V). All GSs in subgroup II were mainly derived from leguminous plants including four GmGS1 proteins (GmGS1β1/2 and GmGS1γ1/2) in soybean. Real-time RT-PCR analysis of GmGS1 genes indicated that soybean GS duplicated genes had the same tissue specificity of expression, while the four subgroup II GmGS1 genes presented higher expression level in soybean nodules than in other tissues. Among the six GmGS1 genes, GmGS1β2 located on chromosome 18 had the highest expression level and predominantly expressed in developing nodules. GmGS1β2 was then ligated into pGEX4T-1 vector and transformed into BL21 (DE3) for prokaryotic expression. GmGS1β2 recombinant protein was purified by 4B-Beads and tested for GS activity by spectrophotometer. Prokaryotic expression result showed that the molecular weight of GmGS1β2 was 39 kD, which is consistent with previous theoretical prediction. Catalyzing reaction showed that the recombinant protein had glutamine synthetase activity, which means GmGS1β2 encoded a functional GmGS1β2 glutamine synthetase. These results provide useful information for further functional research of GS1 proteins involved in nitrogen assimilation in soybean nodule.

Genetic Diversity and Linkage Disequilibrium Analysis in Barley

LAI Yong,MENG Ya-Xiong,WANG Jin,FAN Gui-Qiang,SI Er-Jing,WANG Peng-Xi,LI Bao-Chun,MA Xiao-Le,YANG Ke,SHANG Xu-Wu,WANG Hua-Jun

Acta Agron Sin. 2013, 39(12):  2154-2161.  doi:10.3724/SP.J.1006.2013.02154

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The objective of this study was to provide a suitable evaluation for introduced germplasm resources and useful information for associate analysis and parental combinations in barley (Hordeum valgare L.). A total of 192 alleles were detected by 64 SSR markers on chromosomes 1H to 7H in 221 barley accessions with 2–7 alleles per locus. The allelic frequency ranged from 0.0090 to 0.9729, with the mean of 0.3333. The gene diversity was from 0.0528 to 0.7807, averagely 0.4813. The polymorphism information content (PIC) value ranged from 0.0514 to 0.7464 with the mean of 0.4113. The genetic similarity of the 221 accessions ranged from 0.4844 to 0.9792 with the mean of 0.7023. All accessions were clustered into two major groups and seven subgroups. Most landraces or developed varieties fell into the same major group. Genetic structure analysis revealed two subpopulations of these accessions, with consistence to the clustering analysis. Genetic distance between the two subpopulations was 0.3358, and the second subpopulation had richer diversity than the first one. There was linkage disequilibrium (LD) among linked loci and unlinked loci pairs, and 830 out of 2016 loci pairs (41.2%) had significant LD (P < 0.01) with D′ average value of 0.4. The LD level of developed variety was higher than that of landraces. Target traits of developed varieties were mainly distributed on chromosomes 2H, 4H, 6H, and 7H.

Cloning and Expression Analysis of Abscisic Acid Signal Transduction Key Enzyme Gene SoSnRK2.1 from Sugarcane

TAN Qin-Liang,LI Chang-Ning,YANG Li-Tao,LI Yang-Rui

Acta Agron Sin. 2013, 39(12):  2162-2170.  doi:10.3724/SP.J.1006.2013.02162

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Sucrose non-fermenting 1-related protein kinase (SnRK) is the key enzyme of ABA signal transduction pathways, which plays an important role in plant development under adversity environments. Reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) were applied to clone SoSnRK2.1. The cDNA full length of SoSnRK2.1 gene is 1385 bp, containing a 1002 bp complete open reading frame. The amino acids sequence analysis indicated that SoSnRK2.1 gene encodes 333 amino acids, sharing high homology with other species, especially gramineous of Zea mays and Oryza sativa. We constructed the gene prokaryotic expression vector pET-SoSnRK2.1, and obtained the protein of 38 kD induced by IPTG, which was consistent with the theoretical value. The result of Real time qPCR analysis showed that SoSnRK2.1 gene expression was basically up-regulated under different stresses of ABA, PEG+ABA, PEG, NaCl, cold, and H₂O₂.It indicated that SoSnRK2.1 gene takes part in regulations of drought, highsalt, low temperature or other stress process, which may play an important role in adaptation of plants to adverse stresses.

Resistance Grading Method and Evaluation in Wheat Varieties to Orange Wheat Blossom Midge, Sitodiplosis mosellana (Diptera: Cecidomyidae) in China

WU Yu-Qing,DUAN Ai-Ju,ZHANG Zi-Qi,LIU Chang-Ying,LIU Shun-Tong,JIANG Yue-Li,MIAO Jin,DUAN Yun,GONG Zhong-Jun,LI Tong

Acta Agron Sin. 2013, 39(12):  2171-2176.  doi:10.3724/SP.J.1006.2013.02171

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To simplify the method of identifying resistance in winter wheat varieties to orange wheat blossom midge,Sitodiplosis mosellana (Diptera: Cecidomyidae), we compared the traditional method for resistance assessment and a resistance grading method based on percentage of infested spike (ISP) in field experiments carried out in Luoyang, Henan Province, China from 2008 to 2012, using 236–417 wheat varieties each year. The correlation analysis showed that yield loss was highly associated with ISP. Under high density of insect population, the ISP grading method was more effective in identifying the resistance to the insect than the traditional method, and the resistance to S. mosellana was divided into five levels, namely immune (ISP = 0), highly resistant (0 < ISP < 20), moderately resistant (20 £ ISP < 40), Medium (40 £ ISP < 60), susceptible (60 £ ISP < 80), and highly susceptible (ISP ≥ 80). Using ISP grading method, resistance to S. mosellana was evaluated in 25 commercial wheat varieties with growing area larger than 2´10⁵ hectares. All varieties of winter wheat were susceptible or highly susceptible to S. mosellana, but Jingmai 66, was highly resistant. This result indicates not only the possibility of replacement of the traditional resistance evaluation method by the new simple and high-efficient grading method, but also the risk of S. mosellana burst due to extreme shortage of resistant resource in Chinese wheat varieties.

Overexpression of a Stress Induced Maize NAC Transcription Factor Gene, ZmSNAC1, Improved Drought and Salt Tolerance in Arabidopsis

LU Min,ZHANG Deng-Feng,SHI Yun-Su,SONG Yan-Chun,LI Yu,WANG Tian-Yu

Acta Agron Sin. 2013, 39(12):  2177-2182.  doi:10.3724/SP.J.1006.2013.02177

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NAC proteins, which are important regulatory factors, have received much attention for their biological functions in abiotic stress adaptations and tolerances, as well as in the plant metabolic processes under biotic stress and in development. Previously, we isolated a stress-induced NAC gene, designed as ZmSNAC1, from the maize inbred line “CN165” and found that overexpression of ZmSNAC1 led to enhanced tolerance to dehydration at seedling stage. In this study, the functions of ZmSNAC1 were further characterized under drought and salt stresses at reproductive stage. The results indicate that overexpression of ZmSNAC1 inArabidopsis conferred enhanced drought and salt tolerances, showing an improved survival percentage and physiological changes, such as the reduced electrolyte leakage and higher chlorophyll content in transgenic plants. These results indicated that ZmSNAC1 may function as a positive regulator in multiple pathways of signal transduction under abiotic stresses and have potential utilization in transgenic breeding for improving stress tolerance in crops.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Characteristics of Senescence and Antioxidant Enzyme Activities in Leaves at Different Plant Parts of Summer Maize with the Super-high Yielding Potential after Anthesis

WANG Yong-Jun,YANG Jin-Sheng,YUAN Cui-Ping,LIU Jing-Guo,LI Deng-Hai,DONG Shu-Ting

Acta Agron Sin. 2013, 39(12):  2183-2191.  doi:10.3724/SP.J.1006.2013.02183

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Grain yield improvement of maize (Zea mays L.) has been evidently associated with delayed leaf senescence during the grain-filling period after anthesis. The object of this study was to explore senescence characteristics and antioxidant enzyme activities after flowering in different position leaves of summer maize with high yield record for providing references of regulating the leaf senescence and achieving the higher yield in China. A field experiment planted Denghai 661, a new hybrid with high-yielding potential, was carried out to compare the experiment of maize with high yield record (EHYR) and the maize grown in conventional farmers’ field (MCFF) in individual level from 2005 to 2007. And the parameters related to the leaf senescence, such as leaf area (LA), LA reduction, net photosynthetic rate (P_n), soluble protein content, activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and malondialdehyde (MDA) content, were determined in this research. The grain yield of EHYR was 2.18 times greater than that of MCFF, reaching 19 349 kg ha^-1. The rapid senescence time of EHYR leaves and MCFF leaves were found at 30 and 50 days after anthesis, respectively. Therefore, the leaf senescence of EHYR was 20 days earlier than that of MCFF. At the rapid senescence stage, the leaf area reduction of EHYR was 5.7% lower than that of MCFF. During the later period of leaf senescence, the net photosynthetic rate was higher in top and middle leaves than in bottom leaves. Furthermore, the soluble protein content in leaves of EHYR was higher than that of MCFF, but the MDA content was on the contrary. At 20 days after anthesis, the SOD activities in top and middle leaves of EHYR were higher than those of MCFF, while the SOD, POD, and CAT activities in bottom leaves of EHYR were higher than those of MCFF. On the contrary, the POD and CAT activities in middle leaves of MCFF were higher than those of EHYR. Results of both correlation analysis and path analysis indicated that the leaf reduction was negatively correlated with the CAT activity significantly in EHYR, also with the SOD and POD activities significantly in MCFF, and the direct effects were higher than the indirect effects of SOD, POD, and CAT in both EHYR and MCFF. Compared with MCFF treatment, besides higher SOD and POD activities, EHYR had higher CAT activities and soluble protein content resulting in declined lipid peroxidation during grain-filling period, which caused delayed leaf senescence and leaf senescence degree. There were obvious differences at 20 days post-anthesis in maize leaf senescence physiologically. Between EHYR and MCFF suggesting that the 20–30 days after anthesis is a critical period, and all the related agronomy measures should be recommended to be taken before this phase in maize production.

Canopy Physiology and Characteristics of Yield Components during Reproductive Stage in Soybean Hybrids

ZHANG Wei,ZHAO Jing,QIU Qiang,WANG Shu-Ming,ZHANG Chun-Bao,YAN Xiao-Yan,ZHAO Li Mei,ZHANG Ming-Hao, ZHANG Wei-Long, and FAN Hui-Mei

Acta Agron Sin. 2013, 39(12):  2192-2200.  doi:10.3724/SP.J.1006.2013.02192

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Utilization ofsoybean hybrid is an effective way to increase soybean yield. We used two soybean hybrids (HybSoy-1 and HybSoy-2) and two conventional varieties (CV) with the same maturity (Jiyu 72 and Jilin 30) as materials to explore physiological characters of canopy, traits of yield and yield components, and the physiological mechanism of increasing yield in soybean hybrid at reproductive stage. The result showed that, from 2010 to 2011, compared with CV, the yields of soybean hybrids were increased by 13.9% and 16.7%. Leaf chlorophyll contents at late growth stages, photosynthetic rates at R2 (full bloom)–R7 (beginning maturity) and leaf area indices (LAI) at R2–R4 (full pod) were all significantly higher than those of CV; the maximum LAI of HybSoy-1 and HybSoy-2 in 2010 were 8.09 and 8.30, far more than those of CV, and LAI at late growth stages were not decreased sharply. Biomasses of all varieties reached a peak at R6 stage, while those of soybean hybrids at R2–R7 were higher than those of conventional varieties with significant difference between them at P<0.05 and P<0.01; the means and maximum accumulation rates of biomasses were 0.06 g d^–1 and 0.20 g d^–1 more than those of conventional varieties, respectively; and the days of speeding up or slowing down dry matter accumulation rate were ahead of 3.09 days and 5.85 days than those of CV, respectively, so premature advantage of dry matter accumulation was also obvious. As for yield components, there was no significant difference between hybrids and conventional soybean varieties on 100-seed weight, grain weight and pod weight of main stem, but grain weight and pod weight of branch in soybean hybrids were significantly higher than those in conventional varieties. There was no significant difference in the ratio of grain weight to biomass and the ratio of grain weight to stem weight between soybean hybrids and conventional soybean varieties. All results showed that the yields of soybean hybrids mainly depend on the strong canopy, high speed of dry matter accumulation, and higher biomass.

Characteristics of Super-high Yield Population in Yongyou Series of Hybrid Rice

WEI Huan-He,JIANG Yuan-Hua,ZHAO Ke,XU Jun-Wei,ZHANG Hong-Cheng,DAI Qi-Gen,HUO Zhong-Yang,XU Ke,WEI Hai-Yan,ZHENG Fei

Acta Agron Sin. 2013, 39(12):  2201-2210.  doi:10.3724/SP.J.1006.2013.02201

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A field experiment was conducted using the representative indica-japonica hybrid rice Yongyou 11, Yongyou 12, Yongyou 13, Yongyou 15, Yongyou 17 to compare between super-high and high yield populations formed by the regulation of cultivation measures. The results showed that the spikelets of the super-high yield population was higher than that of high yield population, with difference very significant, but the seed-setting rate and 1000-grain weight of the super-high yield population were lower than those of high yield population. The average spikeletsper panicle was significantly higher than that of high yield population, meanwhile the number of the primary and secondary branches and total grains were higher than those of high yield population, showing a significant or very significant difference. The dry matter accumulation of the super-high yield population was a little lower than that of the high yield population at the jointing stage, but higher at heading and maturity stages. From the critical leaf-age for productive tillers to jointing stage, the super-high yield population had a steady growth with less ineffective tillers and lower peak number of tillers after jointing stage, the super-high yield population had a steady decline in number of tillers and had higher productive tillers rate, leaf area index, photosynthetic potential and dry matter accumulation, compared with the high yield population. The super-high yield population had higher culm diameter and culm wall thickness in the basal first, second and third internodes, as well as higher bender moment and anti-broken strength, and lower lodging index than the high yield population.

Characteristics of Water Use and Dry Matter Accumulation and Distribution in Different High-yielding Wheat Cultivars under Supplemental Irrigation Based on Soil Moisture

GAO Chun-Hua,YU Zhen-Wen,SHI Yu,ZHANG Yong-Li,ZHAO Jun-Ye

Acta Agron Sin. 2013, 39(12):  2211-2219.  doi:10.3724/SP.J.1006.2013.02211

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Water shortage is a serious problem threatening sustainable agricultural development in the North China Plain, where winter wheat (Triticum aestivum L.) is the largest water-consuming crop. The objective of this study was to guide wheat production in this area by selecting high water efficient cultivar and improving irrigation regime. In a two-year field experiment from autumn of 2007 to summer of 2009, irrigation quantum was controlled based on testing soil moisture (SM) in 0–140 cm depth, which was designed in low (SM of 65% at jointing and 55–60% at anthesis stage), medium (SM of 75% at jointing and 65–70% at anthesis stage), and high (SM of 75% at jointing and 75% at anthesis stage) levels. Water use efficiency (WUE), dry matter accumulation and distribution in wheat plant, and grain yield were tested and compared among 14 commercial cultivars. Based on grain yield and WUE, the 14 cultivars were clustered into three groups, namely, super-high yield and high WUE group (I), super-high yield and medium WUE group (II), and high yield and low WUE group (III). One representative cultivar was selected from each group to compare the amount and proportion of water consumption during sowing–jointing, jointing–anthesis, and anthesis–maturity periods. Shannong 15 from group I had significantly lower water consumption from sowing to jointing than Jimai 22 from group II and Yannong 21 from group III, and significantly higher water consumption from jointing to anthesis. However, water consumption amount and proportion had no significant differences among the three cultivars from anthesis to maturity. Under medium SM condition, soil water consumption in Shannong 15 was significantly higher than that in Jimai 22 and Yannong 21, but such advantage in Shannong 15 disappeared under high SM condition. Under medium and high SM conditions, translocation amount and ratio of dry matter accumulated before anthesis and its contribution to grain were significantly higher in Shannong 15 than in Jimai 22 and Yannong 21. Among the three cultivars, harvest index was the highest in Shannong 15, the medium in Jimai 22, and the lowest in Yannong 21.

Ultrastructure of Synergid in Its Degenerative Process in Sugar Beet (Beta vulgaris)

LI Wei,SHEN Jia-Heng,GUO De-Dong

Acta Agron Sin. 2013, 39(12):  2220-2227.  doi:10.3724/SP.J.1006.2013.02220

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Anexperiment was conducted by using TEM to study the degenerative process of synergid in sugar beet, so as to provide more information for reproductive biology of angiosperm. The results were as follows: two synergids were similar in flower bud stage with large number of organelles. Both of them had developed filiform apparatus (FA) at micropyle end and lacked cell wall at chalazal end, showing obvious polarity. Then electron density in one synergid increased. On the other hand, vacuole membrane disappeared, membrane of mitochondrium, plastid and nuclear became illegible, which suggested cell degeneration began. But endoplasmic reticulum and Golgi bodies were still active. Complete degeneration of this synergid occurred before pollination. Number of organelles including mitochondrium, plastids and ribosomes gradually increased in the other synergid (persistent synergid). Mitochondria contained many tubular cristae and obvious DNA fibril. Plastids were irregular in shape and usually contained starch gains and thylakoid membranes. The metabolism of persistent synergid gradually enhanced until fertilization (about 13 h after pollination). It began to degenerate when zygote had alveolate cell wall at the chalazal end and endosperm occurred, while complete degeneration and disappearance of FA took place at late stage of zygote. The results indicated that degeneration of one synergid in sugar beet must be triggered by other stimulation than pollination and pollen tube growth. As a transfer cell, persistent synergid may absorb and transport nutrition for the development of embryo sac.

Effects of Single-seed Sowing on Root Growth, Root-shoot Ratio and Yield in Peanut (Arachis hypogaca L.)

FENG Ye, GUO Feng,LI Bao-Long,MENG Jing-Jing,LI Xin-Guo,WAN Shu-Bo

Acta Agron Sin. 2013, 39(12):  2228-2237.  doi:10.3724/SP.J.1006.2013.02228

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Peanut cultivar Huayu 22 was used to study the differences between single-seed sowing and double-seed sowing modes on root growth, root and shoot relationship, and yield under corresponding planting density. The two single-seed sowing treatments were 195 000 holes per hectare (S1) and 225 000 holes per hectare (S2), respectively with the double-seed sowing (150 000 holes per hectare) as control. During the growth period, dry weights, length, volume and absorption area of the root under three treatments increased and reached the maximum at 40–50 days after flowering, and then decreased. The average root diameter decreased and reached the minimum at 50–60 days after flowering, and then increased. The dry weight of aboveground part and pod increased while the root-shoot ratio decreased continuously. S1 and S2 treatments could improve dry weight of the seedlings, the length, the volume, the absorption area of the roots and the root-shoot ratio, and reduce average root diameter during the whole growth period, especially at the late growth period. Additionally, S1 treatment saved 35% sowing seeds and improved peanut yield by 7.98–8.38%. These results indicated that single-seed sowing could improve peanut yield through guaranteeing relatively stronger root growth predominance, regulating root-shoot ratio, and increasing the productivity potential for each seedling.

Dynamic Characteristics of Matter Population in Two Super Hybrid Rice Cultivars

JI Hong-Ting,FENG Yue-Hua,HE Teng-Bing,LI Yun,WU Biao,WANG Xiao-Yan

Acta Agron Sin. 2013, 39(12):  2238-2246.  doi:10.3724/SP.J.1006.2013.02238

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In order to find foundations of high-yield cultivation in super hybrid rice (SHR), we modeled on dynamics of population indexes. A field experiment with two super hybrid cultivars (Zhunliangyou 527, Q you 6) and Control (II you 838) was conducted in 2011 and 2012, and dry matter accumulation (DMA) and leaf area index (LAI) were measured. The dynamic equations of DMA and relative leaf area index (RLAI) were established and the dynamic characteristics of crop growth rate (CGR), relative growth rate (RGR), leaf area duration (LAD), net assimilation rate (NAR), and Specific leaf area (LAR) were analyzed based on the equations. The DMA and its proportion to the total biomass at rapid growth stage were significantly higher than those of Control. In the process of time after transplanting, the tendency of CGR was expressed in a single peak curve, and CGR of two SHR was higher than that of Control in rapid growth stage. The RGR of Zhunliangyou 527 was higher than that of control from 23 d after transplanting to mature period. As compared with the RGR of Control, the RGR of Q you 6 was lower before 43 d after transplanting, higher from 43 d to 113 d after transplanting , and not much difference from 113 d after transplanting to maturity . A significant correlation was observed between gross LAD and LAD at rapid growth stage, and also between gross LAD and duration of LAI at rapid growth stage. Compared with Control, the RGR of SHR showed faster increasing and decreasing, and its peak value was higher. A single peak curve was available for the dynamic changes of NAR with its most high value from 43 d to 53 d after transplanting. The LAR of two SHR decreased fast from 23 d to 43 d after transplanting, moderately from 73 d to mature stage, and slowly from 43 d to 73 d after transplanting stage. The LAR of two SHR was higher in rapid growth stage than that of Control.

RESEARCH NOTES

Stable Production of Wheat Haploid and Doubled Haploid by Wheat × Maize Cross

CHEN Xin-Min,WANG Feng-Ju,LI Si-Min,ZHANG Wen-Xiang

Acta Agron Sin. 2013, 39(12):  2247-2252.  doi:10.3724/SP.J.1006.2013.02247

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One of the most effective ways to produce wheat haploid is the method of crossing wheat with maize. However, the problem of unstable frequencies in haploid and doubled haploid production affects its application. In this study, 13 F₁ wheat hybrids crossed with maize to explore the effects of wheat growth condition, hormone treatment, culture medium, and strong seedling treatment on production of haploid and doubled haploid. The frequency of embryo formation was 23.9% and the number of embryos per spike was 6.8 for the wheat plants grown in filed and then detached before pollination and hydroponically cultured after pollination. The efficiency of this method was three times higher than that of the method with plants transplanted into pot after green recovering in early spring and then grown in the unheated greenhouse condition. Embryo formation frequencies were obviously different among wheat crosses. There was no significant difference in the frequency of embryo formation between treatments of dipping spike with Dicamba (21.5%) and 2,4-D (21.1%). However, wheat cross had significant effect on embryo formation. The mean frequency of embryo germination on B5 medium was 82.0%, ranging from 70.9% to 88.3%, whereas averaged frequency of embryo germination was 76.6% on 1/2 MS medium, ranging from 70.0% to 86.0%. There was no significant difference between the two culture media in embryo germination. The efficiency of doubled haploid production for the seedlings treated with culture medium and transplanted into pot was 67.6% and 8.6%, respectively. Most of seedlings transplanted into pot had no tiller and grew weakly, this is the reason for low frequency of survival plant and very low frequency of doubling after colchicine treatment.

Effects of Artificial Shaded-Humid Environment on Growth Characteristics in Different Maize Inbred Lines

YAN Qing-Jiu,HUO Shi-Ping*,ZHANG Fang-Kui,ZHANG Xing-Duan,ZHANG Jian,XIANG Zhen-Fan,YU Zhi-Jiang,FENG Yun-Chao

Acta Agron Sin. 2013, 39(12):  2253-2261.  doi:10.3724/SP.J.1006.2013.02253

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Light deficiency and high humidity are important limiting factors resulting in stunted plant, lower production and poorer grain quality of maize (Zea mays L.) in southwest China. It could be an effective way for solving this problem to group with new maize hybrids by evaluating and selecting maize breeding materials with tolerance to shaded-humid environment. During 2011–2012, thirty maize inbred lines were tested and compared under the natural environment and the artificial by simulated shaded-humid environment at the same time. The results showed that the relative humidity of air increased significantly, theillumination intensity and photon decreased very significantly, but the air temperature changed little under the shaded-humid environment，resulting in that the effective functional leaves, tassel branches, plant height, ear height, 100-kernel weight, individual kernel weight, stem diameter, ear diameter, ear length and kernel number per row of inbred lines reduced; the interval from anthesis to silking (ASI) prolonged, the 7th leaf length, 7th leaf length-width ratio and sheath blight index became bigger, with highly significant differences  between two environments. The tested traits varied significantly among different inbred lines also, but not among different years. The results of principal component analysis indicated that the contribution ratio of accumulated variance of the seven main components reached 85.08%. According to the evaluating values (D), which computed by the comprehensive index values and subordinative function values, the thirty inbred lines could be divided into three groups with strong, middle and less tolerance to shaded-humid environment respectively.The stepwise regression analysis showed that the characters influencing the comprehensive values (D) significantly were the 7th leaf length, number of tassel branches and individual kernel weight. The correlation coefficient of linear regression equation was 0.896^**, which suggested that we could identify and select maize breeding materials with tolerance to shaded-humid environment based on these character indices.

Effects of Nitrogen and Potassium Fertilizers Application on Annual Yield and Economic Effect in Rotation of Rice and Wheat

GUO Jiu-Xin,FENG Xu-Meng,HU Xiang-Yu,TIAN Guang-Li,WANG Wei,CHEN Jian,LIU Tian,SAIYIDING Hasanjan,GUO Shi-Wei

Acta Agron Sin. 2013, 39(12):  2262-2271.  doi:10.3724/SP.J.1006.2013.02262

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To evaluate the effects of different potassium (K) fertilizer application methods with optimal and high nitrogen (N) fertilizer rates on the annual yield and the economic effect of rice and wheat rotation. We conducted a field experiment with rice-wheat rotation in 2010–2011 at Institute of Agriculture Science Research at Rugao County, Jiangsu Province. The rice cultivar “Zhendao 11” (a normal japonica variety) and the wheat cultivar “Yangmai 16” (a spring mid-gluten variety) were used to determine the yield and its components, the N, K concentrations and accumulations , and N, K₂O use efficiencies in individual organs at maturity stage. The results showed that application of K fertilizer could improve the annual grain yield of rice and wheat due to the increase of effective panicles, the number of grains per panicle and ripened grains. The annual grain yield of rice and wheat was significantly different among different treatments of K₂O fertilizer application, and application of K could increase the K₂O fertilizer use efficiency and the economic effect. The highest partial factor productivity (PFP), agronomic efficiency (AE), the recovery efficiency (RE) and the economic effect of the K₂O fertilizer were all obtained in the treatment applying 150 kg ha^-1 in soil and 16.2 kg ha^-1 by foliar spray ( K_S150+K_F16.2). The high N rate significantly enhanced the yield of rice resulting fromimproving crop N nutrition level. But the annual grain yield of rice and wheat was not significantly different between treatment of the different N rates, and the high N fertilizer rate could result in optimal N fertilizer use efficiency and economic effect. Combined with the soil environment, economic effect, and fertilizer resource management, these results suggested that optimal N rate should be 200 kg ha^-1 for rice and 180 kg ha^-1 for wheat, and the optimal K₂O application regime should be 90 kg ha^-1 in soil plus 9.7 kg ha^-1 by foliar spray (K_S90+K_F9.7) for rice and 60 kg ha^-1 in soil plus 6.5 kg ha^-1 by foliar spray (K_S60+K_F6.5) for wheat in the experiment area.