Table of Content

12 April 2009, Volume 35 Issue 4

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REVIEW

Establishment, Representative Testing and Research Progress of Soybean Core Collection and Mini Core Collection

QIU Li-Juan,LI Ying-Hui,GUAN Rong-Xia,LIU Zhang-Xiong,WANG Li-Xia,CHANG Ru-Zhen

Acta Agron Sin. 2009, 35(4):  571-579.  doi:10.3724/SP.J.1006.2009.00571

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China has the most soybean germplasm in the world, but only about 1% of them have been used in soybean breeding program, which results in narrow genetic base for developing varieties. This exiguous use of germplasm is due to lack of reliable information on traits with economic importance, which requires replicated multilocational evaluations to identify useful parents. In order to accelerate evaluation and utilization of germplasm, the projects of ‘Establishment of soybean core collection’ (1998–2003) and ‘Gene diversity of mini core collection in soybean’ (2004–2008) were carried out by the continuous supporting from National Basic Research Program (973 project) in case of large germplasm collections has been evaluated properly on the basis of the guideline from core collections. In this paper, the development of core (2–5% of entire collection) and mini-core (10% of core or 1% of entire collection) is introduced. Meanwhile, the complement of the core or mini-core collections is carried out in order to broaden their representative from national wide into international soybean accessions. For testing the representatives of the core collection, four parameters including SSR loci, sample components, sampling ratio and low frequency allele are analyzed, and then confirmed by the random sampling test. The core and mini-core collections have been used in identifying elite traits and developing new lines, in which the approaches have been introduced that based on core and mini-core collections. The further utilization of core and mini-core collections related to genetic diversity and utilization method of collections is discussed, it is pointed that core collections are basic materials for new trait identification, novel gene mining, germplasm enhancement and new variety development. It has been proved that systematic study and use of soybean germplasm will improve the research of the soybean germplam from conservation into wider use.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Quantitative Trait Loci Analysis of Responses to Nitrogen and Phosphorus Deficiency in Rice Chromosomal Segment Substitution Lines

WANG Yu,SUN Yong-Jian,CHEN Deng-Ying,YU Si-Bin

Acta Agron Sin. 2009, 35(4):  580-587.  doi:10.3724/SP.J.1006.2009.00580

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Tolerance to low nitrogen and low phosphorus conditions is a highly desired characteristic for sustainable crop production. In this study, a set of 125 chromosome segment substitution lines (CSSL), each containing a single or few introgression segments from a japonica cv. Nipponbare with the genetic background of an indica cv. 9311, were evaluated using augmented design under the field experiment with normal, low nitrogen (N0), and low phosphorus (P0) conditions. The grain yield and panicle number per plant were measured for each CSSL, and their relative values based on N0 or P0 and normal conditions were considered as the measurement for tolerance to low soil nutrient. The results showed that both the N0 and P0 conditions had strong negative effect on yield and panicle number, and there were different responses among the CSSLs to the stresses, and the relative traits had a significant negative correlation with the traits under the normal condition. 9311 showed better tolerance to low nutrient conditions than Nipponbare. A total of 38 chromosomal regions or quantitative trait loci (QTLs) all with negative allelic effects from Nipponbare were detected for the measured traits under the nitrogen and the phosphorus stresses, of those 26 QTLs were for the yield and panicle number, 12 QTLs for the relative traits. Five chromosomal regions were identified in common under both the stresses, while most QTLs (81%) were specifically detected only in low nitrogen or phosphorus condition. Such different QTLs suggest that the responses to limiting nitrogen and phosphorus conditions are regulated by different sets of genes in rice. Most QTLs for the relative traits were co-localized with those for the yield and the panicle number under either nitrogen or phosphorus stresses, indicating that the tolerance QTLs may be involved in nitrogen and phosphorus uptake or assimilation pathway in rice.

MSAP Analysis of Epigenetic Changes in Cotton(Gossypium hirsutum L.) under Salt Stress

LI Xue-Lin,LIN Zhong-Xu,NIE Yi-Chun,GUO Xiao-Ping,ZHANG Xian-Long

Acta Agron Sin. 2009, 35(4):  588-596.  doi:10.3724/SP.J.1006.2009.00588

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Salinity is one of the important limiting factors in plant production worldwide. The objectives of the study were to assess the effect of salt stress on the plant growth and to determine if DNA can be methylated in cotton plants (Gossypium hirsutum) by methylation-sensitive amplified polymorphism (MSAP) technique. The results showed that 100 mmol L^-1 NaCl obviously promoted plant height and root length of cotton seedlings, but 200 mmol L^-1 NaCl significantly inhibited plant growth; 100–200 mmol L^-1 NaCl inhibited the number of lateral root considerably. The analysis of MSAP showed that the level of global DNA methylation decreased from 41.2% to 34.5% as the salt concentrations increased; there was a significantly negative correlation (r = –0.986) between NaCl concentrations and the level of DNA methylation in cotton roots. Under stresses of 100, 150 and 200 mmol L^-1 NaCl, methylation and demethylation of DNA were 6.4%, 7.6%, 11.3% and 12.7%, 11.1%, 8.2%, respectively. In addition, the analyses of sequences and RT-PCR showed that expressions of genes homologous to MSAP fragments in roots were different between control and treated plants under salt stress, suggesting that these genes would play an important role in the cotton adaptation of salt stress.

Marker-assisted Selection for Stv-bⁱ Gene Controlling Resistance to Rice Stripe Disease

CHEN Feng,ZHOU Ji-Hua,ZHANG Shi-Yong,YAN Chang-Jie,ZHU Wen-Yin,SUN Ya-Wei,YUAN Shou-Jiang,YANG Lian-Qun

Acta Agron Sin. 2009, 35(4):  597-601.  doi:10.3724/SP.J.1006.2009.00597

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Rice stripe disease is one of the most serious viral diseases in Huang-Huai and Yangtze River japonica cultivating area in China, and has caused severe loss in rice production. The pathogen is rice stripe virus (RSV) and transmitted by the small brown plant-hopper, Laodelphax striatellus Fallen. Moreover, rice stripe disease is difficult to assess by the way of artificial inoculation, and easily affected by natural conditions, thereby marker-assisted selection using molecular markers closely linked to disease-resistant gene to improve the efficiency of resistance breeding programs is of great significance. At present, Stv-bⁱ is a widely utilized resistant gene for stripe virus disease in rice breeding that came from indica variety Modan, and Stv-bⁱ has been fine mapped on chromosome 11. In this study, eight molecular markers, including three SSR (Simple Sequence Repeat) and five STS (Sequence-tagged Sites), closely linked to Stv-bⁱ, were developed and displayed polymorphic between Shengdao 13 and Zhendao 88. Among them, three markers, H21, H11-8 and H11-12 were subsequently used for marker-assisted selection. The individual seedlings of three compound breeding populations, F30718 (Shengdao 13/Zhendao 88), F50701 (Wuyou 34/T022//Shengdao 806), and F60702 (V6/T022//Zhendao 88) were genotyped with molecular markers H21, H11-8 and H11-12. The lines from these populations checked by marker-assisted selection to rice strip disease were also investigated under field conditions at next generation. The consistency between field performance and the marker genotype in the three compound breeding populations was 99.3%, 87.7%, and 91.8%, respectively. The results indicated that these molecular markers can be applied for marker-assisted selection in the improvement of resistance to RSV.

Establishment and Identification of a Normalized Full-length cDNA Library of CCRI36

WU Dong,LIU Jun-Jie,YU Shu-Xun,FAN Shu-Li,SONG Mei-Zhen

Acta Agron Sin. 2009, 35(4):  602-607.  doi:10.3724/SP.J.1006.2009.00602

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Short season cotton (SSC) breeding plays an important role in solving the competition for more growing area between cotton and food crops. To explore the premature mechanism of SSC, to clone genes that have a close relation with premature flowering, and to speed process of premature cultivar breeding, we established a normalized full-length cDNA library using the flower and bud of CCRI 36 by DSN (duplex-specific nuclease)-normalization method combined with SMART (switching mechanism at 5' end of RNA transcript) technique. The titer of un-amplified cDNA library was about 1.7×10⁶ cfu mL^-1. The average size of cDNA inserts was 1 200 bp with a recombination rate of 100%. The abundance of transcripts Histon3 and UBQ7 decreased obviously in normalized cDNA library comparing with that in non-normalized samples detected by Virtual Northern Blot. Meanwhile, protein genes associated with flower development were obtained on the basis of the positive signal of cDNA library by PCR. These results indicated that the normalized full-length cDNA library has been established successfully, which is convenient for further study on the molecular mechanism and gene cloning of flower development.

Evaluation of Resistance of a Novel Rice Germplasm YSBR1 to Sheath Blight

ZUO Shi-Min,WANG Zi-Bin,CHEN Xi-Jun,GU Fang,ZHANG Ya-Fang,CHEN Zong-Xiang,PAN Xue-Biao

Acta Agron Sin. 2009, 35(4):  608-614.  doi:10.3724/SP.J.1006.2009.00608

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A novel rice line YSBR1 with resistance to sheath blight (SB) was identified from the progenies of a cross between varieties of japonica and indica. The resistance of YSBR1 to SB was evaluated with multiple replications in the field and greenhouse and inhibition rate of embryo root growth by SB-toxin was investigated also. The results indicated that the resistance of YSBR1 to SB was significantly higher than that of other germplasms tested, and was stable and reliable; the average SB disease score of YSBR1 was 2.39±0.23 and reached “resistant” grade based on a “0–9” SB disease rating system. Line YSBR1 has an appropriate growth period duration and an improved plant type, with semi-dwarf plant (102±4.32 cm), slightly rolled and erect leaves. These results suggested that line YSBR1 has potentially high value for study on genetics and can be useful for improvement of resistance to SB in rice breeding.

SSR Analysis of Funo Wheat and Its Derivatives

SI Qing-Lin,LIU Xin-Lun,LIU Zhi-Kui,WANG Chang-You,JI Wan-Quan

Acta Agron Sin. 2009, 35(4):  615-619.  doi:10.3724/SP.J.1006.2009.00615

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Funo is one of the most important backbone parents in China, and many wheat (Triticum aestivum L.) varieties are derived from it. Funo and 8 parents of the first generation of Funo were analyzed using 247 simple sequence repeat (SSR) markers that covered the entire wheat genome to disclose the inheritance of genes in Funo on genome level and provide theoretical basis on development of backbone parent in wheat. Specific DNA fragments were detected using three SSR markers, Xwmc398, Xgwm400, and Xgwm268. The specific fragments were 178 and 151 bp for Xwmc398, 180 and 149 bp for Xgwm400, and 191 bp for Xgwm268. A total of 255 derivatives of Funo including 54, 124, 36, 33, 5, and 3 varieties respectively from the first to the sixth generations and 5 selected strains of Funo were analyzed using the specific primers. The specific bands of Xwmc398 were observed in all the five selected strains of Funo, whereas, only in Anxuan 2 for Xgwm400 and in Yangmai 1 for Xgwm268,. In the 255 varieties derived from Funo, the inheritable rates of specific bands for Xwmc398 were 52.8%, 38.4%, 16.7%, 0.0%, 0.0%, and 0.0% from the first to the sixth generations, respectively, with an average rate of 32.2%. For Xgwm400, the rates were 32.1%, 19.2%, 41.7%, 33.3%, 20.0%, and 0.0%, with an average of 26.7%. For Xgwm268, the rates were 22.6, 34.4, 11.1, 12.1, 0.0, and 0.0%, respectively, with an average of 24.7%. Xwmc398 had the highest inheritable rate in the Funo-derivative varieties and the most stable inheritance in Funo-selective varieties.

Heterosis,Combining Ability and Their Genetic Basis of Yield among Key Parental Materials of soybean in Huang-Huai Valleys

YANG Jia-Yin,GAI Jun-Yi

Acta Agron Sin. 2009, 35(4):  620-630.  doi:10.3724/SP.J.1006.2009.00620

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In recent years, breeding for hybrid cultivars of soybean [Glycine max (L.) Merr.] for utiliazation of heterosis has been paid great attention, but there are few reports published on the fundamental aspects regarding the heterosis in soybeans.. In fact, for a real utilization of hybrid soybean, the important prerequisite is high heterosis. Therefore, a fundamental effort in hybrid breeding is the choice of parents and identification of superior hybrid combinations. In the paper, heterosis and combining ability were determined using eight key parental materials, including seven from Huang-Huai region and one from US as well as their 28 F₁ diallel crosses in Huaian, Jiangsu, China from 2003 to 2005, and relationships between F₁ performance and its pedigree-based and SSR-based genetic distances were investigated. The results showed that there were heterobeltiosis in yield among parents in Huang-Huai region with average heterobeltiosis of 20.39%, and a big difference among hybridized combinations with a range from –5.34% to 76.88%. We screened combinations, among them, Yudou 22 × Jindou 27, Huaidou 4 × Jindou 27, and Youbian 30 × Meng 9024 had the heterobeltiosis in yield of 76.88%, 29.90%, and 34.42%, respectively. Among those parents used above, Youbian 30 and Jindou 27 were the elite. Heterosis of pods per plant and seeds per plant were relatively in accord with yield heterosis. Yield heterosis in parents was related to general combining ability(GCA) and specific combining ability(SCA). One of parents has high GCA or both have high GCA and high SCA in high-yield combinations. Parents-based cluster and SSR-based cluster analysis revealed that genetic relationships for eight parents were basically consistent, and eight parents were grouped into two groups, one including six varieties from middle and south of Huang-Huai region, the other consisting of one from Shanxi and one from America. Therefore, certain genetic distanceis require for a cross with high heterosis and high yield, but genetic distance is not an only determinant factor for high-yield heterosis.

Isolation and Characterization of NBS-LRR Resistance Gene Analogs from Sugarcane

QUE You-Xiong,XU Li-Ping,LIN Jian-Wei,CHEN Ru-Kai

Acta Agron Sin. 2009, 35(4):  631-639.  doi:10.3724/SP.J.1006.2009.00631

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The large group of plant disease resistance (R) genes that share similar structures possesss a predicted nucleotide-binding site (NBS) domain. NBS domains of this class of R genes show highly conserved amino acid motifs, which makes it possible to isolate resistance gene analogs (RGAs) by PCR with degenerate primers. According to the conserved motifs in the NBS regions of the three typical NBS-LRR type resistance genes (RPS2, N, and L6), five degenerate and one non-degenerate primers were designed to correspond to the P-loop motif in the sense direction, while nine degenerate plus one non-degenerate primers were made corresponding to the HD motif in the anti-sense direction. Then, the homologous PCR was used to amplify NBS sequences from genomic DNA and cDNA using sugarcane variety NCo376 with smut resistance. In all, eleven RGAs were obtained, five from DNA (EF059973, EF059974, EF059975, EF059976, and EF059977) and six from cDNA (EF155648, EF155649, EF155650, EF155651, EF155652, and EF155653). Sequence analysis showed that RGAs comprised the conserved domains P-loop, Kinase-2a, Kinase-3a and HD, which was conserved in NBS-LRR type disease resistance gene. Cluster analysis showed that eleven RGAs and RPS2 and XA1 were clustered into one group, and N and L6 were divided into another group. Further, amino acid sequences showed that their last amino acid in alignment was residue W in LLVLDDV(W/D) motif, which is typical to non-TIR-NBS-LRR type gene. It was suggested that only non-TIR-NBS-LRR but not TIR-NBS-LRR type resistance genes existed in sugarcane genome. One RGA termed PIC (EF059974) was selected randomly for function validation through Real-time PCR. The result showed that expression of PIC gene could to some extent be influenced by U.scitaminea, SA and H₂O₂, and had the characteristics of constitutive expression and tissue-specific. The RGA cloned in this experiment may provide the shortcut for cloning of sugarcane disease resistance gene.

Molecular Analyses on Rs-AFP2 Transgenic Wheat Plants and Their Resistance to Rhizoctonia cerealis

LU Yan,ZHANG Zeng-Yan,REN Li-Juan,LIU Bao-Ye,LIAO Yong,XU Hui-Jun,DU Li-Pu,MA Hong-Xiang,REN Zheng-Long,JING Jin-Xue,XIN Zhi-Yong

Acta Agron Sin. 2009, 35(4):  640-646.  doi:10.3724/SP.J.1006.2009.00640

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In this study, the gene encoding Rs-AFP2, a small cyteine-rich antifungal protein from radish, was evidenced to be transformed into a wheat (Triticum aestivum L.) cultivar Yangmai 12 via bombardment of biolistic particle and PCR detection. To evaluate if expression of Rs-AFP2 enhances the transgenic wheat resistance to Rhizoctonia cerealis, a major pathogen of wheat sharp eyespot, the transgenic wheat plants from T₁ to T₄ generations were subjected to R. cerealis inoculation and the disease resistance rating, and PCR, PCR-Southern, Southern blotting, and RT-PCR/Q-RT-PCR analyses for the Rs-AFP2 transgene. Results showed that Rs-AFP2 gene was integrated as a single copy into the susceptible receptor wheat cultivar Yangmai 12, inherited from T₁ to T₄, and expressed in the wheat background. The transgenic wheat plants expressing Rs-AFP2 showed enhanced resistance to R. cerealis and unchanged agronomic traits compared with nontransgenic Yangmai 12. In the transgenic wheat plants, the express level of Rs-AFP2 was associated with the disease resistance degree. These results suggested that Rs-AFP2 gene can be useful for improving wheat resistance to R. cerealis.

Characterization of Xinjiang Local and Intoduced Wheat Germplasm for High Molecular Weight Glutenin Subunits and Quality-Related Genes with Molecular Markers

LI Jing,HE Zhong-Hu,XIA Xian-Chun,WU Xin-Yuan,LI Dong,CAO Jun-Mei

Acta Agron Sin. 2009, 35(4):  647-661.  doi:10.3724/SP.J.1006.2009.00647

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High molecular weight glutenin subunits (HMW-GS), 1B·1R translocation, polyphenol oxidase (PPO) activities, and yellow pigment content are mostly correlated with the processing quality of common wheat (Triticum aestivum L.). An accurate and fast characterization of these genes is of great importance in the improvement of wheat quality. In this study, a total of 321 wheat genotypes, including 100 Xinjiang local wheat cultivars, 130 introductions from other provinces of China and 91 introductions from other countries, were analyzed by SDS-PAGE method. In addition, the functional markers of Dx5, Bx7, By8, By9,1B·1R, PPO16, PPO18, PPO29, and YP7A were used to detect their allelic variations. Twenty-one subunit combinations were found according to the SDS-PAGE data, 3 types at Glu-A1 locus with Null as a major subunit, 10 types at Glu-B1 locus with Bx7+By8 and Bx7+By9 as major subunits, and 8 types at Glu-D1 locus with Dx2+Dy12 and Dx5+Dy10 as major subunits. The frequencies of the Dx5, Bx7, By8, and Bx9 subunits revealed by functional markers were 38.3%, 85.7%, 38.9%, and 42.7%, respectively, with 97.2%, 98.4%, 93.4%, and 97.2% of consistency with SDS-PAGE results, respectively. Eighty-six genotypes had 1B·1R translocations, with 22.0% in Xinjiang local cultivars, 31.5% in the introductions from other provinces of China, and 25.0% in those from other countries, respectively. The frequencies of Psy-A1b detected by YP7A marker were 9.0%, 10.8%, and 5.4% among three group genotypes, respectively. The PPO18 marker for the Ppo-A1 locus yielded Ppo-A1b allele with frequencies of 38.0%, 43.8%, and 45.7% among three group genotypes, respectively. The Ppo-D1a allele frequencies were 48.0%, 66.9%, and 40.2% among three group genotypes, respectively, according to the PPO16 and PPO29 markers at Ppo-D1 locus. However, only 74 genotypes contained Ppo-A1b and Ppo-D1a alleles at both loci, accounting for 23.0% of the genotypes. The functional markers applied in this study were repeatable, accurate and stable, and can be effectively used in wheat quality breeding.

Fertility Alternation of Thermo-photo-sensitive Genic Male Sterile Wheat Line C412S and Expression of Fertility Related APRT Gene

ZHANG Jian-Kui;DONG Jing;ZONG Xue-Feng;YU Guo-Dong;DAI Xiu-Mei;RUAN Ren-Wu

Acta Agron Sin. 2009, 35(4):  662-671.  doi:10.3724/SP.J.1006.2009.00662

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C412S is a novel type of thermo-photo-sensitive genic male sterile (TGMS) wheat (Triticum aestivum L.) line, which is derived from the cross between TGMS line C49S and normal wheat line C412. To understand the fertility alternation of C412S, the courses of pollen mother cell (PMC) meiosis and microsporogenesis were observed using smear and squash microscopic techniques. Moreover, the expression characteristics of adenine phosphoribosyl-transferase gene (APRT) in young spikes were detected under sterile and fertile conditions using quantitative RT-PCR. When adjusting the environmental temperature and photoperiod at the formation and development stages of male sexual cell through series seeding dates, C412S showed continuous changes of fertility from complete sterility to high sterility, semi-sterility, lowe sterility, and normal fertility. C412S in normal PMC meiosis, however, showed a peak pollen abortion at later mononucleate stage of microsporogenesis, which mostly belonged to spherical abortion type. From PMC formation stage to mature pollen stage, C412S was sensitive in fertility, especially from PMC formation stage to PMC meiosis stage. Compared with C412 (control), C412S only had several base variations in a few loci of APRT1 gene, and the deducted amino acid sequences of C412S and C412 were completely identical. The RT-PCR analysis showed that the transcription level of APRT gene in the young spikes of sterile C412S plants was lower than that of fertile C412S plants from PMC formation stage to mono-nucleate microspore stage. Therefore, the transcription level of APRT gene in young spikes is probably related to the fertility alternation in TGMS wheat.

Cloning and Prokaryotic Expression of a Low Molecular Weight Glutenin Gene from Wheat Variety"Shaan 253"

WU Dan,GAO Xiang,YU Xu,DONG Jian,ZHAO Wan-Chun,CHEN Qi-Jiao,PANG Hong-Xi,LI Zhe-Qing

Acta Agron Sin. 2009, 35(4):  672-678.  doi:10.3724/SP.J.1006.2009.00672

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Low-molecular-weight glutenin subunits (LMW-GS) play an important role in the determination of flour viscoelastic properties in wheat (Triticum aestivum L.). LMW-GS has large polymorphism and variation in molecular size, thus, it is difficult to be isolated using one-dimensional electrophoresis. Shaan 253 is a wheat variety with characteristics of high yield and early maturity, especially, with elite high-molecular-weight glutenin subunits, such as 5+10 on 1D, 14+15 and 20 on 1B, and 1 on 1A. The purpose of this study was to understand the contribution of LMW-GS to the processing quality in Shaan 253. Using a pair of specific primers of LMW-GS and pMD19-T vector, one DNA fragment of 1 498 bp (GenBank accession No. FJ172533) was obtained from Shaan 253. The fragment contained the complete coding sequence of 912 bp and encoded 304 amino acid residues. According to sequence analysis, this gene was involved in Glu-D3 loci, and had high similarities to other known LMW-GS genes with the highest identity of 99.34%. Deduced amino acid sequence showed there were typical features of LMW-m type in N-terminal region, which was confirmed by the phylogenetic analysis. The expression vector of pET32a-GluD3-S253 was constructed and transformed into the host bacteria Escherichia coli Rosetta-gami B (DE3). The expression product was testified using SDS-PAGE and Western-blot, indicating that the fusion protein was successfully expressed.

Comparative Study on Genetic Diversity of Wild Rice(Oryza rufipogon Griff.)in China and Three Countries in Southeast Asia

SUN Xi-Ping,YANG Qing-Wen

Acta Agron Sin. 2009, 35(4):  679-684.  doi:10.3724/SP.J.1006.2009.00679

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Simple sequence repeat (SSR) analysis was performed to assess the genetic diversity of Oryza rufipogon Griff. using 10 representative populations from China, 2 populations from Vietnam, 1 population from Laos and 2 populations from Cambodia. A total of 282 individuals were screened using 24 different SSR primers. Relationship among populations was analyzed based on the UPGMA cluster method. The results were as follows: (i) Two hundred and eighty nine alleles were detected at 24 microsatellites loci; the average number of alleles (A) was 12; the average effective number of alleles (Ae) was 7; the expected heterozygosity (He) was 0.812; the observed heterozygosity (Ho) was 0.543; the Shannon’ index (I) was 1.99, which meant that the detected populations from 4 countries were rich of genetic diversity. (ii) The populations from China had the most abundant genetic diversity with I of 1.92, while those from Laos, Vietnam and Cambodia were with I of 1.69, 1.47, and 1.45 respectively. (iii) Populations from Laos and Cambodia had the closest relationship, while populations from Vietnam, Laos and Cambodia had the closer relationships to each other than to those from China. (iv) Compared with the other populations in China, these from Wuxuan and Hezhou had the closer relationships to these from Southeast countries.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of Wheat-Residue Application and Site-Specific Nitrogen Management on Growth and Development in Direct-Seeding Rice

XU Guo-Wei,TAN Gui-Lu,WANG Zhi-Qin,LIU Li-Jun,YANG Jian-Chang

Acta Agron Sin. 2009, 35(4):  685-694.  doi:10.3724/SP.J.1006.2009.00685

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The annual total amount of crop residue straw exceeds billion tons in China. However, about 45–60% of them are burnt or discarded, which not only wastes organic fertilizer source, but also pollutes the environment. Meanwhile, heavy use of nitrogen fertilizer has become a serious problem in rice production. The objective of this study was to investigate the effects of wheat straw incorporation to soil and site-specific nitrogen management (SSNM) on the growth and development in direct-seeding rice. A mid-season japonica rice cultivar Yangjing 9538 was directly sown in field with three nitrogen (N) fertilizer treatments, no N application, farmers’ fertilizer-N practice (FFP), and SSNM based on chlorophyll meter (SPAD) readings. The results showed that, compared with FFP, SSNM reduced N application by 30.0–31.3% and increased grain yield by 7.61%, on average. The grain yield in the wheat residue-incorporated treatment was 2.65%, on average, higher than that in the residue-removed treatment. In comparison with those under the residue removal and FFP, the number of stems and tillers, leaf area index, and biomass accumulation were less or lower under the residue incorporation and SSNM during the early growth period, but showed no significant difference at heading and thereafter. The residue incorporation increased the content of organic acid in leaves and the difference in temperature and relative humidity between day and night. Both the residue incorporation and SSNM increased the percentage of productive tillers, photosynthetic rate of the flag leaves, root activity, and ATPase activity during grain filling. The results suggest that both the residue incorporation and SSNM benefit the photosynthetic production of direct-seeding rice during the later growth period and an increase in the production efficiency.Reasons for the characteristics of the grain yield, growth and development under the residue incorporation and SSNM were discussed.

Distribution of Al³⁺ in Subcellular Structure of Root Tips Cells and Aluminum Tolerance in soybean

YU Hui-Na,LIU Peng,XU Gen-Di,CAI Miao-Zhen

Acta Agron Sin. 2009, 35(4):  695-703.  doi:10.3724/SP.J.1006.2009.00695

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Aluminum(Al) toxicity is a major limiting factor for yield and quality in crop production in acid soil. Micromolar concentrations of Al³⁺ may inhibit root elongation and consequently influence water and nutrient uptake, resulting in poor plant growth. The microanalysis of the elements was conducted on Zhechun 3 by using Transmission Electron Microscope (TEM) and Energy Dispersive X-ray (EDS) to examine the distribution of Al³⁺ in root tips and Al resistance of soybean. We found that Al³⁺ stresses resulted in irregularly thickened cell wall, increased number of mitochondria, expanded nuclear membrane, and densified precipitates of vacuole. Under the highest Al³⁺ concentration, the mitochondria and other organelles disappeared but cell wall. We detected Al in cell wall, mitochondria and electron-dense precipitates of vacuole of root tip cell under the 10 mg L^-1Al³⁺ stresses by EDS. With the increase of external Al³⁺ concentration treated, the weight and atomic percentage of Al in the organelles increased. The Al³⁺ was found in nuclei when the external Al³⁺ was over 60 mg L^-1. And there was no Al³⁺ in mitochondrion under 60 mg L^-1 and 90 mg L^-1Al³⁺ treatments and electron-dense precipitates of vacuole under the 90 mg L^-1 Al³⁺ stresses. The 14 days Al³⁺ stresses significantly inhibited the growth of root system. The content of Al³⁺ in cell wall was most significantly impacted by the external Al³⁺ concentration. The atomic number of P / Al in cell wall and mitochondria decreased with increased Al³⁺ content. EDS can be used to determine the subcellular location of Al³⁺. As the treatment concentrations of Al³⁺ increased, Al³⁺ primarily accumulated in the cell wall, gradually gathered in part of the organelles and nuclei. The Al³⁺ concentrations also decreased from out layer to insider in the cell.

Effect of Potassium Application Rates on Nitrogen Absorption and Utilization of Different Types of Rice

WANG Qiang-Sheng,ZHEN Ruo-Hong,DING Yan-Feng,ZHU Yan,WANG Shao-Hua,CAO Wei-Xing

Acta Agron Sin. 2009, 35(4):  704-710.  doi:10.3724/SP.J.1006.2009.00704

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Potassium, nitrogen and their interaction play important roles in plant growth, development and yield of rice. Appropriate potassium can stimulate nitrogen accumulation and translocation in rice. In order to identify plant nitrogen absorption, distribution and utilization characteristics of rice under potassium supply, a field experiment was conducted with four potassium rates (0, 90, 180, 270 kg ha^-1K₂O) using conventional japonica cultivars (Wuyunjing 7 and Wuxiangjing 14) and hybrid japonica cultivars (86 you 8, Siyou 422) from 2004 to 2005 on Experimental Farm of Nanjing Agricultural University, Jiangsu province, China. Potassium application increased rice yield (4.56-14.77%) and nitrogen accumulation during growth stages, with the maximum from elongation stage to heading stage, but nitrogen uptake ratio decreased. Potassium application enhanced nitrogen transport amount and percentage after anthesis, as well as nitrogen accumulation in different rice organs, nitrogen distribution percentage in leaves and panicles, whereas declined nitrogen distribution percentage in culm and sheath. Nitrogen absorption from fertilizer, basic nitrogen recovery efficiency before elongation stage, nitrogen recovery efficiency during the whole growing stage, and nitrogen harvest index were raised significantly, but plant nitrogen productivity was opposite. Grain yield, nitrogen accumulation, nitrogen translocation amount and percentage after anthesis, and nitrogen distribution in different rice organs amounted to the maximum at K₂O application rate of 180 kg ha^-1, as well as nitrogen absorption from fertilizer, basic nitrogen recovery efficiency before elongation stage, nitrogen recovery efficiency during the whole growing stage. However, nitrogen absorption percentage from elongation stage to heading stage, nitrogen distribution percentage in culm and sheath, plant nitrogen productivity decreased to the minimum. The yield and nitrogen recovery efficiency of conventional japonica cultivars were higher than those of hybrid japonica cultivars.

Ecologic Difference of Isoflavones Content in Soybean Seeds in Heilongjiang Province

ZHANG Da-Yong,LI Wen-Bin

Acta Agron Sin. 2009, 35(4):  711-717.  doi:10.3724/SP.J.1006.2009.00711

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Isoflavones in soybean is paid widely and extensively attention due to its function in physical health care. As important secondary metabolic compounds in soybean seeds, isoflavones content have been reported to be easily impacted by environment. To survey the difference of isoflavones content in soybean seeds in different environment in Heilongjiang, which is main area to plant soybean in China, four cultivars were planted at five locations from 2005 to 2007. There were significant difference in total and individual isoflavones contents among years, locations, genotypes and genotypes × locations. The mean contents of total isoflavones and individual hydrolyzing isoflavones were significantly higher in 2006 than those in the other two years. And, total and individual isoflavone contents were significantly positively correlated with latitude of the locations at the 0.01 probability levels. As a whole, there are predominant production regions for isoflavones of soybean seeds in Heilongjiang province, so it was feasible to categorize the production regions based on soybean isoflavone in Heilongjiang province.

Effect of Potassium Deficiency on Root Growth of Cotton(Gossipium hirsutum L.)Seedlings and Its Physiological Mechanisms Involved

ZHANG Zhi-Yong,WANG Qing-Lian,LI Zhao-Hu,DUAN Liu-Sheng,TIAN Xiao-Li

Acta Agron Sin. 2009, 35(4):  718-723.  doi:10.3724/SP.J.1006.2009.00718

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Premature senescence caused by potassium (K) deficiency has been an important limiting factor in cotton production in China, and K uptake ability of plant from media has a close correlation with root growth and development. In the present study, cotton cultivar NuCOTN99B was sowed in sand in growth chamber, uniform cotton seedlings were transferred to 1/2-strength modified Hoagland’s solution with low (0.05 mmol L^-1) or moderate (0.50 mmol L^-1) K⁺ at 4 d after germination to investigate the effect of K levels on the root system indicators, endogenous free indole acetic acid (IAA) content and ethylene amount released from the cotton seedlings root. The results showed that the lateral root formation of seedlings grown in low K solution for four days was significantly inhibited by about 20%. After 10 d treatment, root elongation was also significantly reduced. Furthermore, we found that the reduction of lateral root was mainly resulted from short length of branched root zone, and there was no change in the density of lateral root under lower K. In addition, root system was classified into fine roots (0.05–0.20 mm), middle roots (0.25–0.45 mm), and coarse roots (> 0.45 mm) according to root diameter. Total root length and total root surface area of cotton seedlings grown in low K media for four days reduced by about 60%, and the fine root was inhibited severely, the coarse roots moderately, and the middle roots slightly. For example, the root length, root surface area and root volume of fine roots grown in low-K media for 4 and 10 d were only approximately 10% and 25% of those in moderate-K media, respectively. Additionally, only fine roots were constantly inhibited by low-K during treatment period in terms of the ratios of different diameter’s roots to total roots, which resulted in the fact that the magnitude of K deficiency in cotton seedling was higher than that of inhibition of root growth, because the uptake activity in fine roots is higher than those in middle and coarse roots. For example, the accumulated K of seedlings grown in low-K solution for 4 d and 10 d were 25% and 16% of that grown in moderate-K solution, respectively; whereas the total root length and total root surface area were 35.7–38.0% (4 d) and 47.7–50.6% (10 d). As expected, the endogenous free indole acetic acid (IAA) content in roots grown in low-K media was reduced by 50%, whereas the amount of ethylene release had nearly six-fold increase, which might provide an explanation to some extent for the inhibition of lateral root formation and root elongation by potassium deficiency.

Photosynthesis and Related Physiological characteristics Affected by Exogenous Glucose in Wheat Seedlings under Water Stress

HU Meng-Yun;Li Hui;ZHANG Ying-Jun;LIU Qian

Acta Agron Sin. 2009, 35(4):  724-732.  doi:10.3724/SP.J.1006.2009.00724

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Drought, one of the main adverse environmental factors, obviously affects plant growth and development. Previous studies have shown one of the plant mechanisms conferred stress tolerance is the rapid accumulation of soluble sugar (glucose, fructose and sucrose) during water stress. A large number of stress responsive genes have been reported to be induced by glucose, indicating the role of sugars in environmental responses. Although it has already been shown that sugars act as signaling molecules in plants to modulate growth, development, and stress responses, little is known about the mechanisms by which plants respond to them under water stress. To investigate the regulational relation between glucose and drought resistance in wheat, the effects of exogenous glucose on growth and photosynthesis in wheat (Triticum aestivum L.) seedlings under water stress were studied. Wheat seedlings were treated with Hoagland solution (T0), 15% PEG-6000 (T1), 15% PEG-6000+100 μmol L⁻¹ Glc (T2), and 15% PEG-6000+300 μmol L⁻¹Glc (T3), respectively. Effects of exogenous glucose on the leaf water potential and relative water content, photosynthesis, photosynthetic pigmentcontent, soluble sugar and proline content in leaves, as well as growth of seedlings and roots were analyzed. The leaf water potential and leaf photosynthesis decreased significantly, and the growth of seedlings was inhibited when the plants were subjected to water stress. However, the leaf water potential, photosynthetic pigments content increased in T2 and T3 treatments. Simultaneously, the net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), and water use efficiency (WUE) in leaf increased. However, the but transpiration rate (T_r) decreased when the seedlings were treated with exogenous glucose under water stress and rewatered after water stress. Moreover,the levels of proline and soluble sugar in leaves increased by glucose treatment under water stress. Exogenous glucose treatment increased the number of lateral roots, and the length of adventitious roots, and the plant dry matter increased by 14.32–40.39% compared to the drought treatment alone. These results indicate that exogenous glucose may improve drought resistance by increasing roots growth and photosynthesis in leaves under water stress.

Physiological Response to 1,2,4-Trichlorobenzene Stress of Different Rice Genotypes in seedlings

ZHANG Guo-Liang,CHEN Wen-Jun,QIU Li-Min,SUN Guo-Rong,DAI Qi-Gen,ZHANG Hong-Cheng

Acta Agron Sin. 2009, 35(4):  733-740.  doi:10.3724/SP.J.1006.2009.00733

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1,2,4-Trichlorobenzene (TCB) has pervaded in industrial and agricultural production. Because of a series of problems due to its longevity and amassment, TCB has been added into the environmental pollutant list. In order to know how TCB affects the rice seed germination, seedling growth and its physiological characteristics, the seed germination, seedling biomass, soluble protein, and malnodialdehyde (MDA) contents, as well as activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in leaves and roots of seedlings treated with TCB were investigated in a sand culture experiment using rice cultivars, Xiangjing 20-18 (TCB tolerant genotype)and Siyang 1382(TCB sensitive genotype). The results indicated that TCB had little effect on the seed germination rate and index, however caused the significant reduction of seedling biomass, withXiangjing 20-18 being more affected than Siyang 1382. With TCB stress degree strengthening, soluble protein content of Xiangjing 20-18 leaves and roots presented anincreasing tendency, while that of Siyang 1382 leaves decreased significantly, and that of its roots decreased too under treatment of high TCB concentration. O₂^? producing velocity of leaves in two genotypes decreased firstly, then increased with increasing TCB concentration. That of Xiangjing 20-18 roots presented thesame tendency, and significantly higher than the control at TCB ≥0.6 mmol kg^-1, while that of Siyang 1382 roots had no significant difference with that of the control. SOD activity of Xiangjing 20-18 leaves increased, and that of roots increased significantly. After TCB ≥0.2 mmol kg^-1, SOD activity of Xiangjing 20-18 leaves was significantly higher than that of the control, that of Siyang 1382 leaves and roots was not significantly different with that of the control. POD activity of Xiangjing 20-18 leaves increased firstly, then decreased, and that of roots was significantly higher than the control, while that of Siyang 1382 leaves and roots decreased significantly. CAT activity of Xiangjing 20-18 leaves was higher or significantly higher than that of the control, and that of Siyang 1382 was contrary to the result of Xiangjing 20-18. MDA content of leaves decreased firstly, then increased, being significantly higher than that of the control at high TCB concentration, and that of roots increased significantly in two genotype. In conclusion, lower reduction of seedling biomass, high protein content of leaves and roots, the better active oxygen’s elimination ability and lower MDA content in plants would be considered as the physiological traits in TCB-tolerant genotypes of rice.

RESEARCH NOTES

QTL Mapping of Resistance to Silk Cut in Maize

WEI Xin,LI Li-Hua,WANG Zhen-Hua,SONG Rui,ZENG Xing,ZHANG Zhi-Ming,PAN Guang-Tang

Acta Agron Sin. 2009, 35(4):  741-744.  doi:10.3724/SP.J.1006.2009.00741

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Using 115 SSR markers and the F₂ population consisting of 348 lines derived from the cross between maize (Zea mays L.) inbred lines R08 and Es40, a genetic linkage map associated with the resistance to silk cut was constructed. The genetic linkage map covered 2 178.6 cM of maize genome with an average mapping distance of 18.9 cM. Using the composite interval mapping (CIM) method, 12 QTLs controlling the resistance to silk cut were detected on chromosomes 1, 2, 4, 5, and 7. These QTLs explained phenotypic variances ranging from 4.22% to 37.95%. Among them, two major QTLs on chromosomes 1 and 3, which explained more than 30% of phenotypic variances, had dominance effect, whereas, the other 10 QTLs had partial dominance effect or additive effect.

Effects of Plant Population Density on Fractal Dimension of Corn Based on Image Processing

LIANG Shu-Min,YANG Jin-Zhong,LI Na-Na,Hao Jian-Ping,DU Tian-qing,CUI Fu-Zhu,CHENG Li-Juan

Acta Agron Sin. 2009, 35(4):  745-748.  doi:10.3724/SP.J.1006.2009.00745

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Using fractal analysis method and image process, for corn cultivar Qiangsheng 49 was analyzed the effects of plant population density on fractal dimension (FD) of plant skeletal images. When the population density increased from 2.4 to 7.8 plants per square meters by 1.2 increment, the FD value decreased gradually from 1.192 to 1.163. Under all population density conditions, the FD values increased till early kernel filling and then decreased. The FD value was correlated with plant height, photosynthetic leaf sources and biomass to some extents. FD can be used widely in describing corn plant architecture as a new meaningful indicator.

Comparison on Gene Expression and Microstructure of Tobacco Leaves at Maturity Stage in Different Types of Soil in southern Anhui Province,China

QIU Li-You,LI Fu-Xin,ZU Chao-Long,MA Chen-Xin,YANG Chao,FENG Yun,LIU Guo-Shun

Acta Agron Sin. 2009, 35(4):  749-754.  doi:10.3724/SP.J.1006.2009.00749

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Yunyan 97(Nicotiana tabacum) was planted in four types of soil including coarse sandy soil, coarse sandy mud, powder sandy soil, and rice soil (CK), in the south of Anhui. The gene expression profile and cell construction of tobacco leaves at maturity stage were explored using cDNA microarray and microscopical technique. Comparing tobacco leaves grown in coarse sandy soil to rice soil, up-regulated genes were mainly for cell multiplication, growth, development, and oxidation stress, while genes in photosynthesis, protein and phospholipids synthesis were down-regulated. Specifically up-regulated genes involved in auxin transport, polysaccharide synthesis, and responsible for protein and amino acid degradation in tobacco leaves cultivated in coarse sandy mud briefly compared with rice soil. Compared to rice soil, up-regulated genes of tobacco leaves in powder sandy soil principally dealt with drought stressand degrading cellulose, pectin, starch, and protein. The microscopic and ultramicroscopic structure of the tobacco leaves revealed that tobacco leaves in powder sandy soil and rice soil grew badly. On the contrary, coarse sandy mud and especially coarse sandysoil produced well grown leaves. The results should conduce to unveil the mechanism of burnt-sweet sensation formation in tobacco leaves cultivated in the south of Anhui Province.

Inheritance Effect of Protein Content in Maize Kernels and Its Relation to Yield

LI Hao-Chuan,LIU Yi-Bao,CHENG Rong-Xia,SUN Xi-Zeng,WANG Ya,TANG Ji-Hua,LIU Zong-Hua

Acta Agron Sin. 2009, 35(4):  755-760.  doi:10.3724/SP.J.1006.2009.00755

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Fourteen maize (Zea mays L.) inbred lines selected from five basic populations were crossed with 5 elite inbred lines from different heterotic groups, and the 70 combinations according to NCII design were evaluated at three locations in 2005 and 2006. The protein content in kernels was analyzed using the Near Infrared Reflectance Spectroscopy (NIRS) method. Among the female populations, male lines, and their hybrids, significant variances on protein content in kernels were observed. Two basic populations of female parents, “8822” and “M”, had higher levels of protein content than other female populations, and they could essentially promote the protein content of their hybrids when they crossed with elite male parents Pb (Mo17) or Pa (Ye 478). The majority (94.29%) of the genotype variance (V_G) for protein content in kernels was from additive variance (V_A). However, the broad sense heritability and narrow sense heritability were both in low levels, which were 35.83% and 33.94%, respectively. This indicated that the environmental factors had obvious effects on this trait. The grain yield has no significant correlation with protein content in kernels (r = 0.053, P > 0.05). Therefore, it is feasible to promote the maize yield and protein content in kernels simultaneously through pyramiding elite genes.