Table of Content

12 March 2009, Volume 35 Issue 3

Previous Issue    Next Issue

REPORT

Advances in Molecular Biology Study of Plant Organ Abscission

WANG Xiang;CHEN Xiao-Bo;LI Ai-Li;MAO Long

Acta Agron Sin. 2009, 35(3):  381-387.  doi:10.3724/SP.J.1006.2009.00381

Abstract ( 2729 )   PDF (245KB) ( 3382 )   Save

References | Related Articles | Metrics

Organ abscission is a ubiquitous phenomenon in the plant kingdom. Abscission occurs at specific sites called abscission zones (AZs). The development and functionating of AZs are complex and precise processes which involve many genes. Degradation of cell wall and middle lamella at AZs causes cell separation and leads to shedding of distal organs. Seed-shattering is one of the most important traits in crop cultivation and breeding and is a typical case of organ shedding. Domestication of non-shattering crop lines is one of the greatest achievements of human civilization, but untill recently its molecular mechanisms started to be revealed. This review focuses on the advances in the molecular biology study of abscission zone development and organ shedding in Arabidopsis, rice and tomato. The paper provides a brief perspective for the future research in this important arena.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Analysis of QTLs for Resistance to Small Brown Planthopper(Laodelphax striatellus Fallen)in Rice(Oryza sativa L.) Using an F₂ Population from a Cross between Mudgo and Wuyujing 3

DUAN Can-Xing;CHENG Zhi-Jun;LEI Cai-Lin;ZHAI Hu-Qu;WAN Jian-Min

Acta Agron Sin. 2009, 35(3):  388-394.  doi:10.3724/SP.J.1006.2009.00388

Abstract ( 2148 )   PDF (417KB) ( 1472 )   Save

References | Related Articles | Metrics

The small brown planthopper (SBPH), Laodelphax striatellus Fallén (Homoptera: Delphacide), is an economically important pest in rice (Oryza sativa L.) and distributes widely in China. It not only causes direct damage by sucking plant sap but also transmits several viral diseases such as Rice stripe virus(RSV) and Rice black-streaked dwarf virus(RBSDV). which often cause major yield losses.. Host resistance has been recoqnized as one of the most economic and effective measures in controlling SBPH. Mudgo is one of indica rice cultivars with high resistance to SBPH, expressing strong antixenosis and antibiosis against SBPH. A genetic linkage map was constructed with an F₂ population, derived from a cross between Mudgo and a japonics cultivar Wuyujing 3 for mapping QTLs associated with resistance to SBPH. The linkage map comprised 104 SSR and 3 Indel markers and covered 1 409.9 cM of rice genome with an average marker interval of 13.2 cM. One hundred and seventy-seven plants of F_2:3 families were identified for resistance to SBPH by way of the modified seedbox screening test. QTL analysis of SBPH resistance was conducted using composite interval mapping implemented in Windows QTL Cartographer 2.5 software. A total of three QTLs, Qsbph2b, Qsbph3d, and Qsbph12a,conferring resistance to SBPH were detected on chromosomes 2, 3, and 12, locating in the regions of RM5791–RM29, RM3199–RM5442, and I12-17–RM3331, with LOD scores of 3.25, 3.11, and 6.82, respectively. The resistant alleles of Qsbph2b, Qsbph3d, and Qsbph12a, were all from Mudgo and could explain 17.3%, 15.6%, and 35.8% of total phenotypic variance, respectively. Qsbph12a linked tightly to the markers RM3331 and I12-17 has a potential value in breeding for SBPH resistance by rapid marker-assisted selection.

Construction of Genetic Linkage Map in Peanut(Arachis hypogaea L.) Cultivars

HONG Yan-Bin;LIANG Xuan-Qiang;CHEN Xiao-Ping;LIU Hai-Yan;ZHOU Gui-Yuan;LI Shao-Xiong;WEN Shi-Jie

Acta Agron Sin. 2009, 35(3):  395-402.  doi:10.3724/SP.J.1006.2009.00395

Abstract ( 2183 )   PDF (482KB) ( 2446 )   Save

References | Related Articles | Metrics

Molecular genetic map is a fundamental organizational tool for genomic research. However, a comprehensive genetic linkage map for peanut cultivars has not yet been developed due to extremely low levels of DNA polymorphisms in cultivated peanut. In this study, 184 recombinant inbred lines (RIL), derived from a cross between two Spanish type peanut cultivars (Yueyou 13 × Fu95-5), were used as mapping population. A total of 652 pairs of genomic-SSR primers and 392 pairs of EST-SSR primers were used to detect the polymorphisms between the parental cultivars. Of them, 121 SSR primer pairs amplified 123 segregating loci and were selected to analyze the RIL population. A genetic linkage map consisting of 108 SSR loci (102 genomic-SSR and 6 EST-SSR) in 20 linkage groups and covers 568 cM with an average distance of 6.45 cM of intermaker was constructed. By comparing the SSR genetic map of Arachis (A. duranensis × A. stenosperma) with AA genome, 11 linkage groups in the linkage map constructed in this study were confirmed to have homology with 6 linkage groups of wild peanut species.

Characterization of Overexpressed Bx7 Gene(Bx7^OE) in Chinese and CIMMYT Wheats by STS Markers

REN Yan;LIANG Dan;ZHANG Ping-Ping;HE Zhong-Hu;CHEN Jing;FU Ti-Hua;XIA Xian-Chun

Acta Agron Sin. 2009, 35(3):  403-411.  doi:10.3724/SP.J.1006.2009.00403

Abstract ( 2214 )   PDF (280KB) ( 1527 )   Save

References | Related Articles | Metrics

Over-expression of the high molecular weight glutenin subunit (HMW-GS) Bx7 is highly associated with dough strength of wheat (Triticum aestivum L.) flour. A total of 163 Chinese and CIMMYT wheat cultivars and advanced lines were tested by two STS markers and RP-HPLC to understand the presence of HMW-GS gene Bx7^OE The results indicated that the markers TaBAC1215C06-F517/R964 and TaBAC1215C06-F24671/R25515 could amplify a 447 bp and a 844 bp PCR fragments, respectively, in the lines with Bx7^OE, whereas no PCR products were detected in the lines without Bx7^OE. Of the 163 cultivars and lines, specific PCR fragments were amplified in 11 genotypes by the two markers, indicating the presence of Bx7^OE in these lines, with a frequency of 6.7%. The results obtained by RP-HPLC were consistent with those revealed by STS markers. These two STS markers could be used to detect the presence of Bx7^OE gene in wheat cultivars.

An Efficient Method of Cotton DNA Fibers Preparation for FISH

PENG Ren-Hai;SONG Guo-Li;LIU Fang;LI Shao-Hui;WANG Chun-Ying;ZHANG Xiang-Di;WANG Yu-Hong;WANG Kun-Bo

Acta Agron Sin. 2009, 35(3):  412-417.  doi:10.3724/SP.J.1006.2009.00412

Abstract ( 2282 )   PDF (248KB) ( 1560 )   Save

References | Related Articles | Metrics

Fluorescence in situ hybridization (FISH) has become the most important technique applied in molecular cytogenetics, especially in developing physical maps in plants. As a key technique, FISH on cotton DNA fibers stretched has not been reported yet, possibly owning to the difficulty in their DNA fiber preparation as well as the existence of thick cytoplasm and hard cell walls. Here we present a method of highly efficient preparation of stretched DNA fibers in cotton. Cotton cotyledons germinated in dark moisture chamber for one week were chopped with a sharp sterile scalpel in a Petri dish that contained ice-cold nucleus isolation buffer(MgSO₄ 10 mmol L^-1, KCl 5 mmol L^-1, HEPES 0.5 mmol L^-1, DTT 1 mg mL^-1, Triton X-100 0.25%, PVP40 2%) followed by sequential filtration through 100, 50, and 30 µm nylon meshes. Nuclei were obtained by centrifuging the filtrates at 16 000 g for 1 min. Mixture of nucleus lysis buffer(0.5% SDS, 5 mmol L^-1 EDTA, 100 mmol L^-1 Tris, pH7.0) and nuclei was incubated on the slide for 9 min, DNA fibers obtained by dragging and stretching with a clean slide edge from the end to another end on the liquid surface. After incubated at 60℃ overnight, the slides were pretreated with DNase-free RNase and then rinsedin 2×SSC. The probes and DNA fibers were denatured separately, and hybridization mixture was incubated on the slide overnight, followed by post-hybridization rinses in 2×SSC, 1×4T. The slides were blocked with 5% BSA and covered with antibody for 1h. After rinsed with 1×TNT the slides were counterstained with 4', 6-diamidino-2-2phenylin-dole (DAPI) and followed by rinsing in 1×PBS. After mounting the slides with Vectashield mounting medium the hybridization signals were observed under a fluorescence microscope. Images were captured by a charge-coupled device (CCD) system and brought together to make the plate using Adobe Photoshop 7.0 software. The results indicated that it was easier to release nuclei from cells in nucleus isolation buffer by chopping cotyledon, and slowly and smoothly dragging the nuclei solution with a slide edge from the end to another end on slide treated with poly-L-lysine. Highly stretched and intact DNA fibers were obtained. This method is very simple and rapid, which takes only 30 min to finish the entire process, and it is also safe because poisonous mercaptoethanol is replaced by dithiothreitol. The linear or near-linear stretches of beads on-a-string signals with cotton genomic DNA and 45S rDNA as probes showed that the DNA fibers were suitable for FISH.

Proteome Analysis on Resistance to Phytophora Root Rot in Soybean

QIU Hong-Mei;LIU Chun-Yan;ZHANG Dai-Jun;XIN Xiu-Jun;WANG Jia-Lin;WANG Jing;SHAN Da-Peng;HU Gu-Hua;CHEN Qing-Shan

Acta Agron Sin. 2009, 35(3):  418-423.  doi:10.3724/SP.J.1006.2009.00418

Abstract ( 2048 )   PDF (412KB) ( 1356 )   Save

References | Related Articles | Metrics

Phytophthora root rot caused by Phytophthora sojae is a serious soil-borne fungi disease endangeringsoybean production and bringing huge economic losses. The objective of this study was to survey and identify the proteins associated with resistance, using soybean cultivar Suinong 10 by two-dimensional gel electrophoresis and mass spectrometry technology.Nineteen differentially expressed proteins were obtained, of twelve which presented up-regulated, six were down-regulated, and one was special protein. Ten protein spots including eight with up-regulated expression, one with down-regulated expression, and one with specially expression were investigated by biological mass spectrometry. The results showed that eight functional proteins were identified, three of which involved inmetabolism, consisting of the ribolose-1,5-phosphate carboxylase large subunit and its precursor, succinyl coenzyme A, three of which were related to signal transduction, encompassing kinase receptor like protein, oxidoreductase, and cysteamine ammonia acid oxidoreductase, one of which participated in transport of metabolites in cells, i.e. clothing zeta-3 protein subunits, one of which was concerned with the jasmonic acid-mediated resistance, including F-box protein. The results provide useful information for studying the molecular mechanism of resistance to Phytophthora root rot.

Genetic Behaviour of Thinopyrum intermedium Chromosome 2Ai-2 in Different  Wheat Chromosome Substitution Backgrounds of Group 2

ZHANG Yue;LIN Zhi-Shan;CAO Bao-Jiu;GUO Yi-Qiang;WANG Mei-Jiao;YE Xing-Guo;XIN Zhi-Yong;XU Qiong-Fang;GUO Shi-Hua

Acta Agron Sin. 2009, 35(3):  424-431.  doi:10.3724/SP.J.1006.2009.00424

Abstract ( 1874 )   PDF (389KB) ( 1145 )   Save

References | Related Articles | Metrics

Thinopyron intermedium is one of the important gene sources for high resistances to barley yellow dwarf virus, stripe rust as well as tolerances to cold and drought in wheat (Triticum aestivum L.) breeding. Several wheat–Th. intermedium addition lines, substitution lines, and translocation lines have been developed as breeding materials, including the 2Ai-2 substitution lines with high resistances to the GPV and GAV strains of barley yellow dwarf virus. The aim of this study was to provide cytogenetical evidence on the behavour of 2Ai-2 chromosome of Th. intermedium in different wheat chromosome substitution backgrounds. Five wheat–alien disomic (or ditelosomic) substitution lines were crossed with common wheat variety Chinese Spring to generate the BC₁ and F₂ populations, and the two populations were detected using EST-PCR markers specific to 2Ai-2 chromosome and genomic in situ hybridization (GISH). In the F₂ generation, plants with 2Ai-2 accounted for 83.1% and 82.4% in offsprings of the 2Ai-2 (2B) substitution lines N420 and N439, respectively, which were higher thantheexpected ratio of 75%; whereas, the observed ratios in offsprings of the 2Ai-2 (2D) substitution lines N431 and N452 were 67.6% and 53.8%, respectively, which were lower than the expected value. Especially, the observed value in the hybrids of N452 was significantly different from the expected value (P < 0.01), inferring that the alien chromosome or fragment might be preferentially transmitted into F₂ generation in 2Ai-2 (2B) substitution lines through the corresponding gametes. On the contrary, the transmission ratio of the alien chromosome or fragment was low in 2D-subsititution background. It was concluded that the effect of different substitution background on the transfer of the 2Ai-2 chromosome was different. In addition, in both 2B and 2D subsititution backgrounds, the transmission ratio of the alien chromosome or fragment was obviously higher through male gametes than female gametes. Furthermore, many plants with 2Ai-2 in F₂ and BC₁ were detected using 2Ai-2-specific EST-PCR markers in a limited region, but not in other region, indicating that the alien chromosome was unstable when it was transmitting from hybrid to subsequent generations. From the results, it was inferred that most chromosome variances occurred near centromere. Compared with the short arm, the long arm of the alien chromosome was lost more often in the next generations. The F₂ plants with 2AS-substitution background (N530) were very few when detected with 2Ai-2S-specific EST-PCR marker(s).The difference between observed and expected values was significant (P < 0.01), suggesting that the alien telosome might be lost freguently. Structure variationoftelosome 2Ai-2S was also observed inthe offsprings with2AS-substitution background. GISH results confirmed that the EST-PCR markers can be used effectively in tracing the alien chromosome in wheat background.

Mapping of a Novel Anthracnose Resistance Gene Using SSR Markers in Common Bean(Phaseolus vulgaris L.)

WANG Kun;WANG Xiao-Ming;ZHU Zhen-Dong;ZHAO Xiao-Yan;WANG Shu-Min

Acta Agron Sin. 2009, 35(3):  432-437.  doi:10.3724/SP.J.1006.2009.00432

Abstract ( 1912 )   PDF (518KB) ( 1569 )   Save

References | Related Articles | Metrics

Anthracnose (Colletotrichum lindemuthianum) is one of the most important diseases of common bean throughout the world. Resistant cultivars utilization is the most economic, effective and environment harmless method to control this disease. However, disease resistance in the host is unsustainable due to the high variability of anthracnose. So it is necessary to explore the new resistance genes persistently. Among the 11 reported resistant loci, 10 of them originated from Mesoamerican gene pool and only one locus named Co-1 from Andean gene pool. The objective of this study was to identify the new Andean gene resistant to anthracnose in the Chinese common bean landraces. 108 F₂ plants derived from a cross between common bean Red flower (R) and common bean Jing (S) were inoculated with anthracnose race 81. The resistant individuals grew well without obvious disease symptoms but the susceptible plants have many disease spots on the leaves and stems, and then died gradually. The segregation ratio of resistant to susceptible plants in F₂ population was 3:1 based on chi-square test, indicating that the resistance of Red flowercommon bean to anthracnose race 81 was controlled by a single dominant gene, named as Co-F2533 temporarily. Four SSR markers were detected on B6 linkage group of common bean that linked to the resistance gene Co-F2533 with the distance of 6.6, 18.4, 20.9, and 30.9 cM respectively. The position of the resistance gene and the markers on the chromosome were as follows: Clon1429, Co-F2533, BM170, BMD37, and Clon410. A linkage map was constructedwith Mapdraw V2.1. Since the absent of anthracnose resistance genes on B6 linkage group, it is proposed that Co-F2533 is a novel anthracnose resistance gene in Chinese resistant landrace Red flower from Andean gene pool, which will be useful in the anthracnose resistance breeding for common bean.

Identification System of Resistance to Whitefly in Soybean

XU Ran;LI Wei;WANG Cai-Jie;ZHANG Li-Feng;DAI Hai-Ying;XIANG Han

Acta Agron Sin. 2009, 35(3):  438-444.  doi:10.3724/SP.J.1006.2009.00438

Abstract ( 2027 )   PDF (257KB) ( 1184 )   Save

References | Related Articles | Metrics

Whitefly (Bemisia tabaci Genn.) is an agricultural pests with wide occurrence, severe harm, strong virulence in soybean around the world, so it is an effective way to breed resistant soybean varieties to whitefly. The objective of this study was to establish an identification system of whitefly on soybean using 419 foreign and Chinese soybean germplasm in Jinan and Guanxian in 2004 and 2007. The relationship between different resistance indices was comprehensively analyzed. The results showed that the resistances to whitefly determined by the mean of whitefly nympha per leaflet (MWPL) was significantly different at different locations and in different years, but relatively consistent for the most varieties. Four varieties with high resistance including Huapidou, Dongxuan 1, Hedou 12 and Henghe, and four varieties with high susceptibility consisting Qihuang 26, Ludou 10, Ludou 12 and Qihuang 28 were screened as the standard varieties. The resistant criterion was made as follows: when MWPL <(a+d), the resistance of soybean variety was high resistant; ≥(a+d)~<(a+3d) was resistant; ≥(a+3d)~<(a+5d)was medium; ≥(a+5d)~ <(a+7d)was susceptible; and ≥(a+7d)was high susceptible. Meanwhile the results revealed that top leaves were suitable for the resistance identification of determinate soybean varieties, and middle leaves for that of semi-determinate and in-determinate soybean varieties.

Influence of Inhibitors of Nucleic Acid Synthesis and Protein Synthesis on Glutamine Synthetase Gene Expression Induced by Nitrogen in Sugar Beet (Beta vulgaris L.)

CHEN Sheng-Yong;HOU Jing;LI Cai-Feng;MA Feng-Ming;YIN Chun-Jie; HUANG Zhao-Feng

Acta Agron Sin. 2009, 35(3):  445-451.  doi:10.3724/SP.J.1006.2009.00445

Abstract ( 1656 )   PDF (539KB) ( 1529 )   Save

References | Related Articles | Metrics

Glutamine synthetase (GS, EC6.3.1.2) families are the key enzymes involving in nitrogen assimilation in the higher plants as well as a core elements for nitrogen use efficiency and nitrogen recycle. The objective of this study was to reveal the effect of actinomycin D (AMD) and cycloheximide (CHM) on GS gene expression and its activities induced by nitrogen in sugar beet. GS activity in sugar beet was determined under the treatment of AMD and CHM. Gene transcripts of cytosolic glutamine synthetase (GS1) and plastidic glutamine synthetase (GS2) were detected by semi-quantitative PCR. And e?ciency of GSmRNA synthesis from each sample was estimated by quantitative PCR of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The results showed that the GS activities increased slightly under the low concentration treatment of AMD for 2–6 hours, but decreased with treatment of all concentrations. The transcript level of GS1mRNA and GS2mRNA decreased with the increase of AMD concentration treated for more than 9 h. GS activities decreased fast with the increase of CHM concentrations treated for more than 9 h. There was no significant difference between GS1mRNA and GS2mRNA expressions in the treatments with all CHM concentrations for more than 9 hours.

Isolation and Identification of Differentially Expressed Gene in Sugarcane Infected by Ustilago scitaminea

QUE You-Xiong,YANG Zhi-Xia,XU Li-Ping,CHEN Ru-Kai

Acta Agron Sin. 2009, 35(3):  452-458.  doi:10.3724/SP.J.1006.2009.00452

Abstract ( 2581 )   PDF (225KB) ( 1589 )   Save

Related Articles | Metrics

Sugarcanesmut, caused by Ustilago scitaminea Syd., is a most severe fungal disease resulting in heavy economic losses in sugarcane production. The best way to control the disease is to breed resistant varieties. The objective of this study was to survey the molecular mechanism of sugarcane smut resistance. Twosugarcane varieties infected by smut, consisting of NCo376 with high resistance and F134 with susceptibility, were detected to reveal the differential expression of genes regulating resistance to smut with twelve anchored primers and eight random primers via DDRT-PCR. Seven differentially expressed polymorphic fregments were obtained by coloning, sequencing and semi-quantitative RT-PCR validation. The results of Blast in GenBank showed that they shared high homology (52%–97%) with cytochrome C oxidase (CCO) gene, ribosomal protein gene, NAD-dependent malic enzyme gene, aminotransferase gene, binding protein gene and retrotransposon, respectively. The results of semi-quantitative RT-PCR indicated that while CCO gene expression was regulated by U.sticaminea and salicylic acid (SA), its expression was independent on H₂O_2. Besides, CCO gene expressed in root, stalk and leaf of sugarcane at a relatively low level. From described above, it was inferred that the synthesisof phytoalexin induced by CCO inhibited the pathogen after infection. The results provided useful information for further understanding the molecular mechanism of sugarcane-smut interaction.

Sampling Strategy for an Applied Core Collection of Gaozhou Wild Rice(Oryza rufipogon Griff.)in Guangdong Province of China

CHEN Yu,PAN Da-Jian,YANG Qing-Wen,LIU Bin,FAN Zhi-Lan,CHEN Jian-You,LI Chen

Acta Agron Sin. 2009, 35(3):  459-466.  doi:10.3724/SP.J.1006.2009.00459

Abstract ( 2037 )   PDF (327KB) ( 1218 )   Save

Related Articles | Metrics

There is abundant genetic diversity for the wild rice (Oryza rufipogon Griff.) in Gaozhou of Guangdong in China. They are the precious resources for rice genetic improvement. Two hundred and seventeen materials of Gaozhou wild rice were used for this study. An optimal sampling scale of 20% was determined by combining population classification with systematic cluster selection and confirmed by multiple comparisons. Finally, forty three materials were selected as the applied core collection. The analysis of parameters, such as ratio of phenotype retained, variance of phenotype, Shanno-wavear index and coefficient of variation indicated that the applied core collection well represented the total population in genetic diversity and range of variation. The SSR assay with 34 pairs of SSR primers for this core collection showed that the average number of alleles was 6.879, the average genetic diversity index was up to 0.655, gene heterozygosity was 0.558, and 76.7% of materials tested were different in genotypes. This study has laid down a good foundation for effective study and utilization of Gaozhou wild rice.

Genetic Diversity of Wild Rice and Cultivated Rice

DUAN Shi-Hua;LI Shao-Qing;LI Shao-Bo;ZHU Ying-Guo

Acta Agron Sin. 2009, 35(3):  467-474.  doi:10.3724/SP.J.1006.2009.00467

Abstract ( 2106 )   PDF (426KB) ( 1775 )   Save

Related Articles | Metrics

To evaluate the genetic diversity and variation of common wild rice and Asian cultivated rice, 55 accessions of common wild rice (32 O. rufipogon and 23 O. nivara) and 25 cultivars of Asian cultivated rice (14 indica and 11 japonica) collected worldwide were analyzed by 56 SSR primer pairs. The polymorphic loci percentage was 98.68% and 298 polymorphic loci were detected. A comparison of the polymorphic loci percentage and Nei’s genetic diversity (h) indicated that the genetic diversity of common wild rice was obviously higher than that of Asian cultivated rice. The UPGMA cluster analysis revealed that there was a close relationship between O. rufipogon and O. nivara, but distinct genetic differentiation was detected between them, supporting the piont of view that they are two independent species. The results indicated that the indica-japonica differentiation was not very apparent in many wild rice whereas it was obvious in Asian cultivated rice. According to the cluster analysis, there was a closer consanguineous relationship between Asian cultivated rice and O. rufipogon, which supported the diphyletic origin hypotheses.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Difference and Its Mechanism in Tolerance to Low-Potassium between Liaomian 18 and NuCOTN99B at Seedling Stage

HUA Han-Bai;LI Zhao-Hu;TIAN Xiao-Li

Acta Agron Sin. 2009, 35(3):  475-482.  doi:10.3724/SP.J.1006.2009.00475

Abstract ( 2198 )   PDF (375KB) ( 1223 )   Save

References | Related Articles | Metrics

Exploiting the genetic diversity of cotton in tolerance to low-potassium (K) is desired for sustainable production. The objective of the present study was to compare the variation in tolerance to low-K between Liaomian 18, a non- insect-resistant cotton cultivar, and NuCOTN99B, a transgenic insect-resistant cotton cultivar from American, hydroponically grown in growth chamber and to elucidate the underlying mechanisms controlling that. When K application was sufficient (2.5 mmol L^-1), there was no significant difference in dry matter yield between the two cultivars at seedling-stage. However, Liaomian 18 produced 170% more dry matter than NuCOTN99B under low K (0.03 mmol L^-1) growing condition, suggesting that Liaomian 18 is K-efficiency with higher tolerance to low-K and NuCOTN99B is K-inefficiency. It was observed that K uptake amount per unit root dry weight, per unit root length and per unit root surface area in Liaomian 18 was similar to or lower than that in NuCOTN99B, implying that the K uptake ability concerning physiological aspect of Liaomian 18 was not superior. Furthermore, the ratio of K accumulation in leaf to that in whole plant was 57.7% for Liaomian 18, and 67.6% for NuCOTN99B, which suggested that the K translocation efficiency in Liaomian18 was ineffective, when compared to NuCOTN99B. Nevertheless, Liaomian 18 had a large root system; its root length, root surface area and root volume were equal to 3.4-, 3.8-, and 4.2-fold of those of NuCOTN99B, respectively. Moreover, the index of K utilization (dry matter produced per unit of K concentration) in Liaomian 18 was 147% higher than that in NuCOTN99B. Therefore, the high tolerance to low-K of Liaomian 18 possibly depended on its large root system and efficient internal K utilization instead of its K uptake ability per unit of root dry weight/length/surface area and K translocation efficiency in plant. Because there were no significant differences in osmotic potential as well as relative water content in leaf between Liaomian 18 and NuCOTN99B, it was concluded that the difference in internal K utilization efficiency between the two cultivars was not related to the biophysical function of potassium (regulation of turgor pressure and osmotic potential), but likely related to the biochemical function of potassium (promotion of photosynthesis, phloem loading and protein synthesis etc.).

Proteome Analysis of Relieving Effect of gibberellin on the Inhibition of rice Seed Germination by Salt stress

WEN Fu-Ping;ZHANG Tan;ZHANG Zhao-Hui;PAN Ying-Hong

Acta Agron Sin. 2009, 35(3):  483-489.  doi:10.3724/SP.J.1006.2009.00483

Abstract ( 2840 )   PDF (722KB) ( 2196 )   Save

References | Related Articles | Metrics

Salinity stress is a major abiotic stress to most plant including rice. It has been reported that gibberellic acid (GA₃) can exert a natural beneficial effect on salt stressed rice. In this paper, the effect of salt stress on rice (Oryza sativa L. cv.Nipponbare) seed germination and the effect of GA₃ on salt-stressed rice were investigated. A proteomic approach was employed to further understand the relieving effect of gibberellin on the inhibition of rice seed germination by salt stress. The 5-day-old rice seedlings were treated with H₂O (control), 5 g L^-1 NaCl (treated group I), and 5 g L^-1 NaCl + 100 μmol L^-1 GA₃ (treated group II) for 48 h respectively. The proteins extracted from buds were separated by two-dimensional gel electrophoresis (2-DE) and analyzed with Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS). The results showed that the seed germination of Nipponbare was inhibited by salt stress significantly (see Table 1), while GA₃ could reduce the inhibition significantly (see Table 2). Four protein spots showed differential expression in 2-DE. Three of these proteins were down-regulated (spots 1–3) and one protein disappeared (spots 4) under salt stress. Expression levels of these proteins were recovered partly when treated with GA₃ and NaCl at the same time (see Fig. 1 and Fig. 2). Two protein spots were identified as isoflavone reductase-like protein and phosphoglucomutase (see Table 3). These differential expression proteins may play important role in the mechanism of the relieving effect of gibberellin on the inhibition of rice germination by salt stress.

Ultrastructure of Megagametophyte during the Development Period in Suger Beet(Beta vulgaris L.)

LI Wei;SHEN Jia-Heng;Guo De-Dong;SHANG Ya-Jia;LU Jun-Ping;DING Chang-Hong

Acta Agron Sin. 2009, 35(3):  490-498.  doi:10.3724/SP.J.1006.2009.000490

Abstract ( 1825 )   PDF (3456KB) ( 985 )   Save

References | Related Articles | Metrics

The experiment was conducted by using TEM in order to provide more information for reproductive biology of angiosperm and relative research on sugar beet. The results were as follows: the megagametophyte development type is Polygonum-type. Functional megaspore was rich in ribosomes, and mitochondrium and plastid were increased in number by division. Embryo sac elongated at 1-nucleate stage by fusion of small vacuoles. Nucleus with obvious nucleolus and carnassial nuclear membrane got larger at later stage. Organelle numbers increased and wall ingrowths occurred at the micropylar end. Embryo sac expanded rapidly at 2-nucleate stage due to the formation of central vacuole and the increase of organelles. Starch grains occurred and organelles increased continually at 4-nucleate stage. Eight-nucleate stage was so short that cellularization took place rapidly to form a 7 cell-8 nuclei embryo sac. At early stage of cellularization, all cells were separated by primary wall with many plasmodesmata in it. Abundant rough endoplasmic reticulum stretched along the wall with Golgi bodies and vesicles near it. At late stage of cellularization, egg, and synergids were polarized, large amount of vesicles fused with membrane to join the formation of cell wall and filiform apparatus. Wall ingrowths occurred in central cell at micropylar region near embryo sac wall. In conclusion, embryo sac enlarges gradually with the increase of organelles during megagametophyte development in sugar beet. All the ultrastructural characteristics suggest there is a high level of metabolism in megagametophyte development. Plasmodesmata in the chalazal end wall as a site for symplastic transportation between nucellar cells and embryo sac only appear in functional megaspore and 1-nucleate embryo sac at early stage. Ingrowths at the micropylar end of embryo sac from late stage of 1-nucleate to cellularization enlarge the surface of membrane greatly so as to enhance non-symplastic transportation.

Crystalline Structure and Pasting Properties of Starch in Eight Waxy Corn Cultivars Grown in Spring and Autumn

LU Da-Lei;WANG De-Cheng;ZHAO Jiu-Ran;LU Wei-Ping

Acta Agron Sin. 2009, 35(3):  499-505.  doi:10.3724/SP.J.1006.2009.00499

Abstract ( 2063 )   PDF (372KB) ( 1639 )   Save

References | Related Articles | Metrics

X-ray diffraction technique is widely used in the study of crystal characteristics of starch granule. Waxy corn (Zea mays L.) has a higher crystallinity and better pasting properties than other kinds of corn, which is of good value in industry. The pasting properties of corn are affected by genotypes and growing conditions, and even regulated by the cultivation to some extent. Currently, there is rare knowledge on the differences of starch in waxy corn cultivars grown in different seasons. In this study, starch isolated from eight Chinese waxy corn cultivars grown in spring and autumn, were evaluated for crystalline structure and pasting properties using the X-ray Diffraction and Rapid Visco Analyzer, respectively. All starch samples showed a typical A-type diffraction pattern, indicating the growing season had no effect on it. However, the growing season significantly influenced the starch crystallinity and pasting properties. Starch from autumn-sown plant, compared with that from spring-sown plant, showed higher values in crystallinity, peak intensities (2θ = 15°, 17°, 18°, 20°, and 23°, respectively), peak viscosity, trough viscosity, final viscosity, and breakdown. The setback of starch of waxy corn was low, and that grown in autumn was significantly lower than that in spring. The crystallinity, peak intensity, and pasting characteristics were significantly different among the eight waxy corn cultivars. The crystallinity was positively correlated with the peak viscosity (r = 0.72, P < 0.01), breakdown (r = 0.85, P < 0.01), trough viscosity (r = 0.52, P < 0.05), pasting temperature (r = 0.55, P < 0.05), and negatively correlated to setback (r = -0.49, P < 0.05). The differences of pasting properties between growing seasons were mainly caused by the changed of crystallinity and peak intensity of starch in waxy corn.

Physiological Parameters of Super-High Yielding Soybean Cultivar Zhonghuang 35

WEI Jian-Jun,LUO Geng-Tong,ZHANG Li,WANG Xiao-Guang,DONG Zuan

Acta Agron Sin. 2009, 35(3):  506-511.  doi:10.3724/SP.J.1006.2009.00506

Abstract ( 1901 )   PDF (284KB) ( 1283 )   Save

Related Articles | Metrics

The objective of this study was to explore the mechanism of high yield via analyzing related parameters. Soybean cultivars, Zhonghuang 35 and Xindadou 1 (CK) were grown in a randomized block design with three replications in 2006 and 2007. The physiological and ecological parameters associated with yield were determined. The results showed that for Zhonghuang 35 and Xindadou 1, the highest leaf area index reached 4.31 and 3.64, respectively, the green duration of leaf weight (LAI > 3) was 50 d and 36 d, total leaf area duration (LAD) at growing season was 2 766 375 and 2 385 645 m² d hm^-2, and the harvest index (ratio of seed weight to total plant dry weight) was 37.9% and 33.7%, respectively. Compared with Xindadou 1, the duration of maximum LAI of Zhonghuang 35 was long, the total LAD at growing season and the photosynthetic rate at the late stage were high. The theoretical yields of the two cultivars were 5 521.5 kg ha^-1and 4 666.5 kg ha^-1. Zhonghuang 35 showed good adaptability to the farmland ecology of the Xinjiang oasis, and gave a seed yield of 5 577 kg ha^-1.

Effect of High Temperature during Heading and Early Grain Filling on Grain Yield of Indica Rice Cultivars Differing in Heat-Tolerance and Its Physiological Mechanism

CAO Yun-Ying,DUAN Hua,YANG Li-Nian,WANG Zhi-Qing,LIU Li-Jun,YANG Jian-Chang

Acta Agron Sin. 2009, 35(3):  512-521.  doi:10.3724/SP.J.1006.2009.00512

Abstract ( 2412 )   PDF (677KB) ( 1561 )   Save

Related Articles | Metrics

Heading/flowering and early grain filling are the most stress-sensitive periods in rice growth and development. However, little is known how heat-stress during these periods affects the yield formation. This study investigated pollen development, yield components, and some physiological parameters under high temperature treatments during heading and early grain filling. Four indica rice cultivars, Shuanggui 1 and T219 (heat-sensitive), Huanghuazhan and T226 (heat-tolerant), were pot-grown and subjected to high temperature treatments (the mean temperature during the day > 33℃) during heading/flowering (0–10 d after heading) and early grain filling (11–20 d after heading), and the natural temperature (the mean temperature during the day < 30℃) was taken as the control. The results showed that the high temperature treatment significantly reduced pollen and spikelet fertility rate in heat-sensitive cultivars, and not in heat-tolerant cultivars compared with the control. Seed-setting rate was significantly decreased under the high temperature for heat-sensitive cultivars, leading to a significant reduction in grain yield, with a more reduction under the treatment during heading than during early grain filling. It was less affected for heat-tolerant cultivars. The heat-stress treatment significantly increased activities of enzymes involved in antioxidant system in leaves for the heat-tolerant cultivars, while it much less affected for heat-sensitive cultivars. The high temperature significantly reduced ATPase activity in grains for the heat-sensitive cultivars, and the result was reversed for the heat-tolerant ones. The high temperature increased leaf-temperature and malonyldialdehyde content in leaves，and reduced root activity and the photosynthetic rate of the flag leaf for both kinds of cultivars, butthe increase or reduction was less for heat-tolerant cultivars than for heat-sensitive cultivars. These results suggested that lower leaf-temperature, higher root activity, higher ATPase activity in grains, and higher photosynthetic rate and activities of antioxidant enzymes in leaves would be important physiological traits leading to a higher grain yield for a heat-tolerant rice cultivar.

Comparison of Photosynthetic Characteristics in Soybean Cultivars with Different Phosphorus Efficiencies

AO Xue;XIE Fu-Ti;LIU JIng-Qi;ZHANG Hui-Jun

Acta Agron Sin. 2009, 35(3):  522-529.  doi:10.3724/SP.J.1006.2009.00522

Abstract ( 2133 )   PDF (308KB) ( 1365 )   Save

References | Related Articles | Metrics

Soybean is sensitive to phosphorus deficiency in whole growth stage. Phosphorus plays an important role in photosynthesis. Our objective is to compare the difference of photosynthetic characteristics in soybean cultivars with different phosphorus efficiencies under different phosphorus levels in Shenyang during 2006–2007. The results showed that the soybean cultivars with high phosphorus efficiency had higher seed yields and higher seed phosphorus efficiency at each of the three phosphorus levels. Under phosphate deficiency condition, the cultivars with high phosphorus efficiency had a higher photosynthesis and CO₂ assimilation capacity, as well as higher soluble protein content, lower stomatae restriction and higher yield. The contents of chlorophyll, soluble protein, net photosynthetic rate, stomatal conductance and mesophyll conductance all reached the peak at the podding stage, and then descended. Growth rate, Leaf area duration (LAD) and net assimilation rate showed a rapid increase during the podding and grain- filling stages. The soybean cultivars with high phosphorus efficiency had higher net photosynthetic rate and growth indices at both the single plant and population levels, and had a small response to the change of phosphorus concentration. The main reason was that the phosphorus in the plants could be balanced by more absorption of phosphorus under low phosphorus situation, which could ensure a stronger photosynthesis.

Effect of Nitric Oxide on Ions Absorption in Excised Root Tips of wheat Seedlings under Drought Stress

ZHAO Li-Qun;LIU YU-Liang;SUN Bao-Teng;WANG Cai-Qin

Acta Agron Sin. 2009, 35(3):  530-534.  doi:10.3724/SP.J.1006.2009.00530

Abstract ( 2066 )   PDF (448KB) ( 1213 )   Save

References | Related Articles | Metrics

Longchun 8139 is a wheat (Triticum aestivum L.) cultivar grown in Dingsxi in Northwest China, which has stably tolerance characteristics to drought stress in morphology, physiology, and genetics. To explain the protection mechanism of nitric oxide to plants under drought stress, Longchun 8139 and two drought-sensitive cultivars Ganmai 8 and Dingxi 24 were used for testing the adaptation to drought stress. The excised root tips (2±0.02 cm) from the seedlings were treated with 20% polyethylene glycol (PEG)-6000 to simulate drought stress. In addition, the NO content in root tips was adjusted with 0.2 mmol L^-1sodium nitroprusside (SNP, as NO donor), and 0.3 mmol L^-1 N^ω-nitro-L-arginine (LNNA, a NO synthase inhibitor), and 0.4 mmol L^-1 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (PTIO, a specific NO scavenger) adding in culture medium. In the root tips of Longchun 8139, the activity of NO synthase and NO content increased remarkably, the chloride (Cl^-) content decreased, whereas, the contents of calcium (Ca²⁺) and potassium (K⁺) increased, simultaneously, the activity of plasma membrane H⁺-ATPase was activated under drought stress. However, in the root tips of Ganmai 8 and Dingxi 24, the changing patterns of the parameters above were opposite. When applying SNP, changes of the contents of Ca²⁺ and K⁺, as well as the activity of plasma membrane H⁺-ATPase were observed similar to those induced by PEG in drought-tolerant cultivar, Longchun 8139. These changes in response to drought stress could be counteracted, such as, the promotion of Cl^- content, the reductions of Ca²⁺ and K⁺ content, and the decrease of activity of plasma membrane H⁺-ATPase, if LNNA and PTIO were added in the culture medium. As to Na⁺ content, no obvious variations were observed among all treatments. The results indicate that NO acts as the second messenger in inducing drought resistance through influencing ions absorption, which is dependent on the increased activity of plasma membrane H⁺-ATPase.

Potassium Accumulation and Root Physiological Characteristics of Potassium-Enriched Flue-Cured Tobacco Genotvpes

YANG Tie-Zhao;YANG Zhi-Xiao;NIE Hong-Zi;ZHANG Xiao-Quan;LIU You-Jie;SHANG Xiao-Ying;REN Zhou-Ying;FAN Jin-Hua

Acta Agron Sin. 2009, 35(3):  535-540.  doi:10.3724/SP.J.1006.2009.00535

Abstract ( 1941 )   PDF (226KB) ( 1610 )   Save

References | Related Articles | Metrics

Highquality of flue-cured tobacco in production in China is currently limited by low potassium content in leaf. It is necessary to screen the potassium-enriched flue-cured tobacco genotypes for alleviating the shortage of available potassium in soil. However, there is no standard procedure for such screening. Three different genotypes of flue-cured tobacco including one potassium-enriched cultivar Nongda 202 and two common cultivars of Jingyehuang and NC89 were surveyed in potassium accumulation and root physiology with a hydroponic culture at normal K level (3 mmol L^-1). The results showed that the potassium accumulation of root and stalk among three cultivars were not significantly different, whereas, the leaf potassium concentration of Nongda 202 was significantly higher than that of Jingyehuang and NC89. The indices of root physiology consisting of root vigor and total root vigor,excreted H⁺, CEC, soluable protein content, ATPase activity in Nongda 202 were significantly higher than those in Jingyehuang and NC89, but there were no significant differences in those except root vigor and H⁺ excretion between Jingyehuang and NC89. Compared with Jingyehuang and NC89 in the K⁺ dynamic uptake parameters of root, Nongda 202 had higher V_max and lower K_m, C_min at seeding stage, but higher V_max, K_m and C_min at vigorous growing stage, indicating that the potassium absorption velocity of Nongda 202 was higher, but its tolerance to low potassium was weaker at vigorous growing stage. In conclusion, the potassium accumulation capability of leaves is strong, the physiological activity is vigorous and the potassium absorption rate of roots are high in potassium-enriched flue-cured tobacco genotype.

RESEARCH NOTES

Cloning and characterization of the NAC-Like Gene AhNAC2 and AhNAC3 in Peanut

LIU Xu;LI Ling

Acta Agron Sin. 2009, 35(3):  541-545.  doi:10.3724/SP.J.1006.2009.00541

Abstract ( 1921 )   PDF (686KB) ( 2159 )   Save

References | Related Articles | Metrics

NAC transcription factors existed differentially in plant are the new transcription regulatory factors with multiple biological functions. Two NAC-like genes from peanut were cloned by RT-PCR and RACE methods, named AhNAC2 and AhNAC3 (GenBank accession No. EU755023 and EU755022), which contain an ORF of 1 050 bp and 1 008 bp and encode 349 and 335 amino acids, respectively. Gene sequence analysis showed that the putative protein of both two genes contained conserved NAC domain and highly different C terminal which is the typical characteristics of NAC transcription factors. Meanwhile, the transcription levels of the two genes were investigated by semi-quantitative RT-PCR, and the result showed that the expressions of AhNAC2 and AhNAC3 genes were enhanced by ABA, GA₃, water stress, and cold stress respectively. Furthermore, the two genes expressed constitutively in peanut tissues, and their expression patterns were different in various tissues. In conclusion, AhNAC2 and AhNAC3 genes isolated from peanut were new members of NAC transcription factor family, their comparison to RD26 (AT4G27410) reveals a high amino acid homology. We suggested that they play key roles in ABA signal transduction and drought response in peanut.

Preliminary Study on the Plant Type Characteristics of Double Cropping Rice in Middle and Lower Reaches of Changjiang River

ZENG Yong-Jun;SHI Qing-Hua;PAN Xiao-Hua;HAN Tao

Acta Agron Sin. 2009, 35(3):  546-551.  doi:10.3724/SP.J.1006.2009.00546

Abstract ( 1893 )   PDF (175KB) ( 1230 )   Save

References | Related Articles | Metrics

Plant characteristics of 19 combinations of early rice and 16 combinations of late rice were studied by variance methods. Results showed that high yield rice combination had large sink, high potential yield and powerful ability in dry matter accumulation and N uptake, and high grain weight for early rice and more grain number for late rice. Basic physiologic characteristics of high yielding rice combination were as follows: 110–115 d of growth duration, 95–105 cm of height, long top internode, long length and big drop-angle of the second and third leaves of top, long spike, large number of the first and second panicle-branches, 100–130 spikelets per panicle, 27–29 g of 1000-grain weight, and over 2.5 g for the weight per panicle for early rice; 120–125 d of growth duration, 100–110 cm of height, long top internode, stout stem, medium length and small drop-angle of the top leaves, long spike, large number of the panicle-branches especially of the second panicle-branches, high density of the grain, 120–150 spikelets per panicle, 25–27 g of 1000-grain weight, and about 3.0 g for the weight per panicle for late rice.

Characteristics of Components for Cotton Single Boll Weight in Different Ecological Regions

ZHAO Rui-Hai;HAN Chun-Li;GOU Ling;LEI Jun;ZHANG Wang-Feng

Acta Agron Sin. 2009, 35(3):  552-559.  doi:10.3724/SP.J.1006.2009.00530

Abstract ( 1942 )   PDF (337KB) ( 1106 )   Save

References | Related Articles | Metrics

Cotton production plays an extremely important role in the local economy, and the income from cotton is one of the major finance for farmers in Xinjiang. The cotton production of Xinjiang that is the biggest cotton production base in China has been rapidly developed since 1990s, and the sowing area, yield per hectare and total yield of cotton all rank first in China. The objective of this study was to analyse the cotton single boll weight and its components, and explore the mechanism of getting a higher single boll weight. Thesame cotton cultivars bred in different eco-regions were planted in northern Xinjiang (Shihezi), southern Xinjiang (Kuerle) and Huanghuaihai cotton region (Nangong) at the different sowing dates. The cotton boll of the fruit branch was labeled in different growth stages and the cotton single boll weight and its components were determined after the labeled cotton boll opened and harvested. The results showed that cotton boll weight grown in southern Xinjiang was the highest among three cotton eco-regions. The components of single boll weight except linter weight and lint gross weight were higher in southern Xinjiang than in the other cotton eco-regions. There were positive correlations between single boll weight, fiber weight per boll, lint gross weight per seed, lint weight per seed and their components. The components of single boll weight except lint percentage and seed number per boll of early-middle-maturing cultivars bred in Huanghuaihai cotton region were higher than those of early-maturing cultivars bred in northern Xinjiang. The components of cotton single boll weight in Xinjiang were higher than those in Huanghuaihai cotton region. Besides climatic-ecologic factors, these results above may indicate the major reason of causing higher single boll weight in Xinjiang, especially in southern Xinjiang.

Physiological and Biochemical Responses to Drought during filling Stage in Stay Green Sorghum B35

HUANG Rui-Dong;SUN Lu;XIAO Mu-Ji;ZHOU Yu-Fei

Acta Agron Sin. 2009, 35(3):  560-565.  doi:10.3724/SP.J.1006.2009.00560

Abstract ( 1878 )   PDF (172KB) ( 1451 )   Save

References | Related Articles | Metrics

Effects of drought on a typical stay green sorghum line B35 were investigated through analyzing the physiological and biochemical characteristics of sorghum plants with the treatments of weekly drought stress starting on the 10th day and the 30th day after anthesis respectively in pot experiment. Compared with CK, the stay green sorghum B35 showed higher chlorophyll content (SPAD value), photosynthetic rate and nitrogen content in leaf, stem and grain. Under the condition of drought stress, the increments of electrical conductivity rate, malondialdehyde content in B35 were less than those in CK, the increments of proline contents and decrements of leaf water potential in B35 were more than those in CK. The activities of superoxide dismutase (SOD) and peroxydase (POD) of B35 were higher than those of CK. We suggested that the stay green sorghum line could perform the physiological autoregulation effectively at the aspects of photosynthesis, nitrogen accumulation, cell membrane permeability of leaf, osmoregulation ability and activities of protective enzymes to adapt the drought.

Genome-Wide Analysis of NBS-Encoding disease Resistance Genes in Maize Inbred Line B73

WANG Jie-Ming;JIANG Hai-Yang;ZHAO Yang;XIANG Yan;ZHU Su-Wen;CHENG Bei-Jiu

Acta Agron Sin. 2009, 35(3):  566-570.  doi:10.3724/SP.J.1006.2009.00566

Abstract ( 2673 )   PDF (252KB) ( 2695 )   Save

References | Related Articles | Metrics

Nucleotide-binding site (NBS) disease resistance gene is a largest category in plant disease resistance genes, which is a focus in recent studies on molecular breeding of plant disease resistance. Using maize (Zea mays L.) inbred line B73, the complete set of disease resistance candidate genes that encode NBS was identified in the genome. The putative NBS genes were characterized with respect to structural diversity, phylogenetic relationships and so on. One hundred and sixty-five NBS-coding sequences were identified into two types: nonregular (12) and regular NBS genes (153). The amount of NBS genesis much smaller in maize than in japonica rice (Oryza sativa L.). The 153 regular NBS genes were categorized into eight classes, including CC-NBS-LRR, CC-NBS, NBS, NBS-NBS, NBS-LRR, NBS-NBS-LRR, NBS-X, and X-NBS, according to N-terminal motif and leucine-rich repeat (LRR) domains motif. The 165 NBS genes showed two remarkable branches in the phylogenetic tree, differing from the radiation structure in japonica rice. Gene duplication event was observed based on gene family analysis of the NBS disease-resistance genes in maize; however, the ratio of gene duplication was smaller than that in rice. This might be one of the reasons for less NBS disease-resistance genes in maize than in rice.