Table of Content

12 May 2010, Volume 36 Issue 05

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Genetic Analysis and Fine-Mapping of Gws Gene Using green-white-stripe Rice Mutant

XU Feng-Hua,CHENG Zhi-Jun,WANG Jiu-Lin,WU Zi-Ming,SUN Wei,ZHANG Xin,WANG Jie

Acta Agron Sin. 2010, 36(05):  713-720.  doi:10.3724/SP.J.1006.2010.00713

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Fine mapping and cloning of genes for leaf color mutation are of great importance in the study of chlorophyll biosynthesis and the structure, function, genetics and development of chloroplast in plant. A temperature-sensitive green-white-stripe leaf mutant gws was isolated from a rice T-DNA insertion mutant pool. Genetic analysis showed that the mutation was generated in tissue culture, rather than by T-DNA insertion, and it was controlled by a recessive nuclear gene. Linkage analysis of stripe plants with homologous recessive genes in an F₂ population from the cross of gws × PA 64 indicated that Gws was flanked by the SSR markers of RM19680 and RM136 on Chromosome6, with genetic distances of 1.1 cM and 3.6 cM, respectively. The gene was further delimited by the newly developed markers InDel 15 and InDel 16 into a 73 kb region. A total of 13 genes, including 3 candidate leaf color genes, were found at this interval. Sequence alignments of these candidate genes between the wild-type and mutant revealed at least two bases deletion in the exon of LOC Os06g14620 (ribonucleoside-diphosphate reductase small chain), resulting in a frame-shift mutation and a premature stop codon. The same gene mutation caused by similar green-white-stripe (St1-Stripe 1) was documented previously. A slightly different phenotypes were observed between the mutants st1 and gws. In st1 plants, chlorotic leaves with a few longitudinal green stripes were observed until the fourth or fifth leaf blade mergence and the phenotype was later than that in gws emerged from second leaf seedling.

Molecular Tagging of a Stripe Rust Resistance Gene in a Triticum durum– Aegilops squarrosa Synthetic Wheat CI191

REN Qiang,LIU Hui-Juan,CHEN Yang,XU Shi-Chang,HE Ming-Zhao,XIN Zhi-Yong,ZHANG Ze

Acta Agron Sin. 2010, 36(05):  721-727.  doi:10.3724/SP.J.1006.2010.00721

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Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most serious fungal diseases in wheat worldwide. To diversify the resistance resources, a resistance synthetic wheat CI191 (CPI/GEDIZ/3/GOO//JO69/CRA/ 4/AE.SQ629) has been mined from 94 accessions of Triticum durum-Aegilops squarrosa synthetic wheat introduced from CYMMT. CI191 show highly resistant to six Pst races prevailing in Chinese, such as CY28, CY29, CY30, CY31, CY32, and CY-Su11-4. Based on the responses of CI191 nd 24 wheat materials possessing known stripe rust resistance genes to 22 Pst races, we postulated CI191 was different from all the known resistant genes. According to analysis of inherited mode, the resistance gene in CI191 was controlled by a single dominate gene, tentatively designated YrC191. Using the cross between CI191 and Mingxian 169 (a sensitive wheat cultivar to Pst races), the F₂ segregation population and the bulked segregant pools were established to screen the the simple sequence repeat (SSR) markers linked to YrC191. Seven SSR markers were found to be linked with YrC191 in the alignment of Xwmc419-YrC191/ Xbarc240-Xbarc8-Xcfd65/Xbarc187/Xgwm18/Xgwm11. YrC191 was cosegrated withthe marker Xbarc240, flanked by the closest linked markers Xbarc8 and Xwmc419 with the relative genetic distances of 1.6 cM and 3.1 cM, respectively. Using Chinese Spring nullisomic-tetrasomics and ditelosomic lines of homoeologous group 1, Xcfd65, Xgwm18, Xgwm11, Xbarc187, and Xwmc419 markers were physically mapped on the chromosome arm 1BS, and YrC191 was also located on 1BS. Four SSR markers linked tightly with YrC191 and 1 sequence tagged site (STS) marker for Yr26 could discriminate YrC191 from the other resistant genes on 1BS, such as Yr24, Yr26, Yr10, Yr15, YrCH42, and YrC142. The resusltes suggested that YrC191 may be a novel resistance gene to Pst.

Effect of PUL Allelic Variation on Rice Cooking and Eating Quality

YAN Chang-Jie,FANG Yu-Wei,LI Min,PENG Jun-Cheng,LIU Qiao-Quan,TANG Shu-Zhu,GU Mi

Acta Agron Sin. 2010, 36(05):  728-735.  doi:10.3724/SP.J.1006.2010.00728

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In order to investigate the genetic effect of allelic variation of PUL gene on rice cooking and eating quality, two sets of near-isogenic lines for PUL gene were successfully developed, using an indica variety Guichao 2 and a japonica glutinous variety Suyunuo to make a cross, and then the backcrossing for several generations with two parents, respectively. For each generation, the target plants were selected under the help of the gene specific STS marker on PUL gene. Furthermore, the cooking and eating quality was measured in two sets of NIL as well as their parents. The results indicated that, the NILs did not alter significantly with respect to amylose content, gel consistency and the starch crystalline structure when compared to their recurrent parents; in the contrast, the significant differences were observed between NILs and their recurrent parents with respect to starch paste viscosity and starch thermal property. Hence, it can be concluded that PUL gene plays an important role in determining rice grain cooking and eating quality. Functional differentiation occurred in PUL locus between indica variety Guichao 2 and japonica variety Suyunuo. The gene specific molecular markers on PUL gene developed on the basis of genomic sequence diversity could be directly applied in rice breeding for quality.

Genetic Analysis of Major Loci Groups of Pre-frost Lint Yield in Upland Cotton

Ainijiang,ZHU Xin-Xia,GUAN Rong-Zhan,WAN Ying,ZHANG Tian-Zhen

Acta Agron Sin. 2010, 36(05):  736-743.  doi:10.3724/SP.J.1006.2010.00736

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Early-maturity is closely related to yield and quality of cotton. Cotton growing season in the north of China, especially in the early-maturing cotton area, is short. So early-maturity has decisive significance for the improvement of yield and quality of cotton in this specific area. In the special ecological environment of northern Xinjiang cotton growing region and the Yellow River growing region with wheat-cotton interplanting, improving the pre-frost lint yield primarily depends on the early-maturing cotton varieties with, shorter growth period and more pre-frost boll numbers. In the early-maturing Upland cotton area, pre-frost lint yield largely determines the proportion of high-quality cotton. However, research on molecular breeding for cotton earliness is still lacking at home and abroad. The early-, mid- and late-maturing materials with large genetic differences were used as parents in this study. The genotypes and the relative genetic effects of major loci groups based on Quantitative Trait Loci (QTL) detection system were first adopted to estimate the magnitude of heterosis for pre-frost lint yield, and to analyze the relationship between favourable loci groups and heterosis. According to Griffing’s P(P–1)/2 Incomplete Diallel Cross design, fifteen combinations were made by six cotton varieties from different origins. The results showed that the phenotypic variations explained by major loci groups (G), G×E, environment (E) and minor loci group were 36.79%, 33.46%, 10.37%, and 3.27%, respectively. The pre-frost lint yield was controlled by five isolated major gene loci groups with additive effects of 5.99^{**, –1.26**, –0.92**, –0.75, and 3.01; and dominant effects of 2.55**, 4.16**, 7.95**, 5.32**, and –7.71**, respectively. Mid-parent heterosis of lint yield for major loci groups ranged from 15.55 to 133.56%, with an average of 63.34%, whereas high-parent heterosis ranged from 15.39% to 93.82%, with an average of 44.56%. Pre-frost lint yield heterosis was mainly determined by the gene heterozygosity of major loci groups. The hybrid combination, P2×P5, had highest favorable loci aggregation and surpassed all hybrid combinations in this study in pre-frost lint yield. This shows that genes related to pre-frost lint yield exist in the early- and mid-maturing parents. On the basis of parent materials genotypic estimation, with this method, genotypes aggregating favorable loci can be identified, or the donor with unfavorable locus can be changed to achieve the strong heterotic combinations. Combined with molecular design breeding, conventional cultivars with excellent comprehensive characteristics including high-quality; resistance to insect pests, disease, stress; and other properties can be developed with enhanced breeding efficiency.}

EST-SSR Genetic Diversity and Population Structure of Tea Landraces and Developed Cultivars (Lines) in Zhejiang Province, China

QIAO Ting-Ting,MA Chun-Lei,ZHOU Yan-Hua,YAO Ming-Zhe,LIU Rao,CHEN Liang

Acta Agron Sin. 2010, 36(05):  744-753.  doi:10.3724/SP.J.1006.2010.00801

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Tea [Camellia sinensis (L.) O. Kuntze] has long history in production and consumption in Zhejiang Province, China. Improvement of tea, therefore, is of great importance and a good understanding of the genetic diversity and population structure of tea germplasm is a prerequisite to the improvement. In spite of great advances on the use of molecular markers in tea, achievement is still gotton very slowly compared with in other cereal crops and woody species. Expressed sequence tag derived simple sequence repeat (EST-SSR) is a less costly alternative way of developing new markers for genetic diversity analysis, functional markers development and marker assisted breeding of tea plant. A total of 4 833 ESTs generated from a cDNA library of tea young root were subjected to SSR mining using DNAstar 5.0 software, 577 EST-SSRs were identified and 416 primer pairs were designed by Primer premier 5.0. After the determination of annealing temperatures and polymorphism of all the primers, 64 core primers were selected and used for genetic diversity and population structure analyses of tea landraces and improved cultivars in Zhejiang province. All selected primers were polymorphic and 232 alleles were amplified, with 3.6 alleles per primer pair on an average. Each primer pair identified 2 to 13 genotypes, with an average of 4.3. The mean of polymorphism information content (PIC) was 0.44, ranging from 0.02 to 0.84. Observed heterozygosity (H_o) was 0.44, while expected heterozygosity (H_e) was 0.48. The level of genetic diversity among landraces was slightly higher than that among improved cultivars and breedinglines. There were 226 alleles amplified in 22 landraces with 14 of them that were special. In the thirty-seven improved cultivars, however, two hundred and eighteen alleles were amplified but only six were special. The PIC of the landrace groups varied from 0.24 to 0.36, in which Juyan Qunti was the highest and Huiming Qunti was the lowest. Deqing Qunti was closest to Juyan Qunti in genetic relationship, but farthest from Huiming Qunti. The genetic diversity of tea cultivars from Hangzhou was the highest with PIC of 0.41, while those from Lishui recorded the lowest PICof 0.24. Population structure revealed by software Structure 2.2 and UPGMA cluster analysis showed that landraces and improved cultivars were relatively independent. The improved cultivars were further clustered into smaller groups according to their pedigree. Hybrid offspring from Fuding Dabaicha and Yunnan Dayezhong from different breeding organizations fell into similar group.

Mining Elite Alleles for Seed Vigor Traits in Two Populations of Japonica Rice (Oryza sativa L.) in Taihu Lake Region

WANG Yang,GUO Yuan,HONG De-Lin

Acta Agron Sin. 2010, 36(05):  754-763.  doi:10.3724/SP.J.1006.2010.00754

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Direct seeding in rice (Oryza sativa L.) is a labor-saving, high efficient and water-saving cultivation pattern. Lower temperature stress is the main factor affecting seedling establishment in direct seeding rice field. Breeding rice cultivars with high seed vigor is one of the ways to improve seedling establishment. In order to provide genetic information and breeding materials for breeding cultivars suitable to direct sowing in japonica rice, we conducted this research. Root length, shoot height, and dry weight of seedlings germinated for 7 days on the sloped board were investigated in a natural population composed of 94 varieties from Taihu Lake Region and a recombinant inbred line (RIL) population derived from a cross between Xiushui 79 and C Bao in japonica rice (Oryza sativa L.). QTL analysis of seed vigor was performed by using General Linear Model program in Tassel software for the natural population and Composite Internal Mapping program in Win QTL Cartographer 2.5 software for the RIL population. Elite alleles and their carrier materials were determined on the basis of the result of QTL analysis. The results obtained were as follows: (1) In the natural population, eleven SSR marker loci associated with seed vigor were detected. Forty-two elite alleles for seed vigor traits were detected in the natural population. Among them, 17 associated with root length, 13 with shoot height and 12 with dry weight. Diantun 502 xuanzao, Yangdao 6, Kaiqing, Xianhui 429 and C Bao were carrier materials for the elite alleles of seed vigor. (2) In the RIL population, nine QTLs, including two for root length, four for shoot height and three for dry weight, were detected. All the elite alleles came from C Bao except RM525-143 bp, which associated with dry weight and came from Xiushui 79. (3) In both populations, SSR marker locus associated with root length was detected on chromosome 1, SSR marker loci associated with shoot height were detected on chromosomes 2, 8 and 11, and SSR marker locus associated with dry weight was detected on chromosome 2. More or better elite alleles were detected in the natural population than in the RIL population.

Mutagenic Effects of Different Factors in Spaceflight Environment of Shijian-8 Satellite in Wheat

GUO Hui-Jun,JIN Wen-Kui,ZHAO Lin-Shu,ZHAO Shi-Rong,ZHAO Hong-Bing,LIU Lu-Xiang*

Acta Agron Sin. 2010, 36(05):  764-770.  doi:10.3724/SP.J.1006.2010.00764

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Space environment mainly consisted of cosmic rays and microgravity is a kind of complicated mutagen, and has been used for plant mutation induction and breeding. In the recoverable satellite Shijian-8 that was launched for breeding purpose on September 9, 2006, seeds of three wheat (Triticum aestivum L.) cultivars, Lunxuan 987, Xinmai 18, and Zhoumai 18, were loaded. In the 1×g centrifuge, 300 seeds of each variety were treated with space cosmic rays (CR-E), and in the lead screen container and the satellite capsule, 500 seeds of each cultivar were treated with microgravity (Mg-E) and comprehensive factors of space environment (SPc-E), respectively. The treated seeds were germinated at room temperature and transplanted in the field after vernalization, the inhibition effects of the three treatments were evaluated and the mutagenic effects on wheat were compared. In the SPc-E treatment, growth of seedlings was significantly inhabited in the first generation (SP₁) of Lunxuan 987 and Xinmai 18, whereas no significant effect was observed in the seedling growth of Zhoumai 18. In the CR-E treatment, only the growth of Lunxuan 987 seedlings was significantly inhibited. The Mg-E treatment had no significant effect on seedling growth in all the three cultivars. No significant variations were detected in main agronomic traits in the SP₁ generation. In the SP₂ generation, there were obvious mutations in phenotypes of the three cultivars, such as plant height, spike length and thousand-grain weight. In Lunxuan 987 and Xinmai 18, the highest mutation frequency was observed in the SPc-E treatment, followed by the CR-E treatment, and the lowest mutation frequency in the Mg-E treatment. A novel inheritable mutant of striated-albino leaf, with the frequency of 0.48%, appeared in the SP₂ population of Xinmai 18 under the SPc-E condition. Among the three treatments, comprehensive factors of space environment induced the most frequent mutations of wheat, indicating the synergistic effect between cosmic rays and microgravity, while the single effect of microgravity was much lower than that of cosmic rays.

Analysis of Plant Height Heterosis Based on QTL Mapping in Wheat

LI Zhuo-Kun,XIE Quan-Gang,ZHU Zhan-Ling,LIU Jin-Liang,HAN Shu-Xiao,TIAN Bin,YUAN

Acta Agron Sin. 2010, 36(05):  771-778.  doi:10.3724/SP.J.1006.2010.00771

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Plant height (PH) is an important indicator for plant type, population size, biomass, and resistance to lodging. Besides, it is also associated with grain yield in cereal crops. Thus, it is a constant focus in genetics and heterosis of wheat (Triticum aestivum L.). This study aimed at studying the molecular genetic basis of plant height heterosis in wheat. From a set of doubled haploid (DH) lines derived from Huapei 3 × Yumai 57, an “immortalized F₂” population was constructed with 168 single crosses. The DH lines, IF₂ population, and the parents were evaluated for plant height in three environments, i.e., in Tai’an, Shandong Province, in 2007 and 2008 cropping seasons and in Jiyuan, Henan Province, in 2008 cropping season. Based on the genetic map of quantitative trait locus (QTL) constructed in our previous study, we analyzed the heterosis of PH of wheat using the composite interval mapping method. A total of three additive QTLs, two dominance QTLs, four pairs of epistatic QTLs (including additive × additive, additive × dominance, dominance × additive, dominance × dominance), and 20 heterotic loci were detected for PH in the three environments. Two QTLs, Qph2D and Qph4D, were detected on chromosomes 2D and 4D with minor interaction of additive by environment. In addition, several other heterotic loci for PH were also identified on chromosome 2D at very close regions with similar marker intervals. Of them, QTLs Qph2D-2 and Qph2D-7 explained the variance of PH by 29.77% and 55.77%, respectively. Another QTL associated with PH heterosis, Qph7D-2, was mapped in the marker interval between Xwmc273.2 and Xcfd175 on chromosome 7D in the three environments. The results indicated that a few QTLs on chromosomes 2D, 4D, and 7D play an important role in PH heterosis in wheat. These loci have potential use for the improvement of PH in wheat breeding assisted with molecular markers.

Cloning and Expression Analysis of TaPhyB3 in Triticum aestivum

LI Zhuang,MA Yan-Bin,CA Ying-Fan,TUN Suo-Wei,XIAO Yang,MENG Fan-Hua,FU Feng-Ling,HUANG Yu-Bi,YANG Jian-Beng

Acta Agron Sin. 2010, 36(05):  779-787.  doi:10.3724/SP.J.1006.2010.00779

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As an important regulator in growth, development, and metabolic activities of plant, light is perceived by a variety of photoreceptors that control developmental processes, such as germination, photomorphogenesis, flowering, and senescence. Phytochromes play a pivotal role in plant adaptability to ambient environment. AtPhyB has been found to be involved in the response to red light. At present, PhyB genes have been cloned in various plants, and the expression patterns and functions of the gene family have been studied in Arabidopsis thaliana, rice (Oryza sativa L.), and maize (Zea mays L.), but not in wheat (Triticum aestivum L.). The objectives of this study were to clone the full length of PhyB and study its structure and expression under different lights. The full-length cDNA sequence of PhyB, encoding the apoproteinof phytochrome B, was cloned from wheat cultivar Chinese Spring. This gene is located on chromosome 4D and designated TaPhyB3. This gene possesses four extrons and three introns and the open reading frame TaPhyB3 is 3 501 bases in length, which encodes predicted protein of 1 166 amino acids. The conserved domains of PhyB gene family, i.e., DAF-DOMAIN, PHYTOCHROME REGION, PAS-A DOMAIN, PAS-B DOMAIN, HISTIDINE RELATED DOMAIN 1, and HISTIDINE RELATED DOMAIN 2, were also observed in the predicted protein sequence. The alignment analysis of amino acid sequence showed that TaPhyB3 shared 93% or 90% identity with the PHYBs of rice or maize, respectively, but only 73% with that of Arabidopsis. After treated with continuous darkness, far-red, red, blue, and white lights for 7 d, young seedlings of Chinese Spring were sampled for TaPhyB3 expression analysis using real-time reverse transcription polymerase chain reaction (RT-PCR). TaPhyB3 expression levels in the wheat seedlings under far-red, red, blue, and white lights were 2.2, 7.7, 7.4, and 37.3 times as high as that in seedlings under darkness. When exposed to white light for 90 d, the TaPhyB3 expression was detected in root, stem, leaf, and spike. However, the gene was mainly expressed in above-ground organs of wheat seedling, and TaPhyB3 expression level in leaf was 11.4 times as high as that in root. The expression level of TaPhyB3 is speculated to positively correlate with the degree of the seedling photomorphogenesis.

Transgenic of Ramie with Synthetic CryIA+CpTI Gene by Agrobacterium tumefaciens-Mediated

MA Xiong-Feng, YU Chun-Meng, TANG Shou-Wei, GUO San-Dui, ZHANG Dui, WANG Yan-Zhou, SHU Ai-Guo, SHU Si-Yuan, XIONG He-Beng

Acta Agron Sin. 2010, 36(05):  788-793.  doi:10.3724/SP.J.1006.2010.00788

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Ramie [Boehmeria nivea L. (Guad.)] is a perennial herbaceous plant of the urticaceae family. Ramie affected by many insect pests above and below the ground during the growing season. The pests damage has become an important factor affecting ramie yield and quality in China. Application of chemical insecticides not only is less effective and costly, but also causes environmental pollution. Development of a genetic transformation system to introduce desired genes (e.g. toxin genes) into ramie could improve its agromonic traits such as resistance to insects. The study was conducted to transfer CryIA gene and CpTI gene into the ramie variety Zhongzhu 1. The CryIA gene encodes Bt toxin protein from Bacillus thuringiensis toxinof Vitis pseudoreticulata; while, the CpTI gene encodes a cowpea trypsin inhibitor produced by Vigna unguiculata. Synthesized CryIA geneand CpTI gene were inserted into plant expression vectorpGBI4ABC whichcarried high efficient bivalent insect resistant genes. With high frequency of adventitious shoot induction and plant regeneration, ramie hypocotyls of the variety Zhongzhu 1 were transformed with Agrobacterium tumefaciens strain LB4404 harboring the plant expression vector pGBI4ABC, and then shoot buds formed from calli induced from hypocotyls were selected with the mixed solution of 50 mg L^–1 Kanamycin and 300 mg L^–1 Cefotaxime. The result showed that 32 Kanamycin-resistant plants were obtained, and therein 26 plants were positive in PCR test, indicating that 80% of the Kanamycin-resistant plants contain CryIA gene and CpTI gene. Southern blot and GUS analysis also verified that the foreign genes of CryIA and CpTI were successfully integrated into the genome of the transgenic plants and expressed.

FAE1 Sequence Characteristics and Its Relationship with Erucic Acid Content in Brassica juncea

XU Ai-Xia,HUANG Zhen, MA Chao-Zhi, XIAO En-Shi,ZHANG Xiu-Sen,TU Jin-Xing,FU Ting

Acta Agron Sin. 2010, 36(05):  794-800.  doi:10.3724/SP.J.1006.2010.00794

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Low erucic acid content, which may result from the differential mutation of the fatty acid elongation 1 (FAE1) gene, is a major breeding target in canola quality improvement. We cloned the FAE1 genes in six Brassica juncea varieties (with high, intermediate and low contents of erucic acid), and their sibling species: two B. rapa (with high erucic acid and low contents of erucic acid) and one B. nigra varieties by using the method of homologous sequencing. The results showed that the sequences of FAE1 genes in nine varieties were 1 522 bp without introns, and all encoded a protein of 507 amino acids. There were two FAE1 gene sequences (BjFAEBjFAE1.1 and BjFAE1.2) in B. juncea, and only one FAE1 gene sequence was in B. rapa (BrFAE1) and B. nigra (BnFAE1), respectively. BjFAE1.1 was corresponding to the BrFAE1 of B. rapa; and BjFAE1.2 was corresponding to BnFAE1 of B. nigra. There were 71 nucleotide variations and the different HindIII restriction sites (No. 1415 and No. 1144) and 15 amino acid variations in protein construction between BjFAE1.1 and BjFAE1.2. The FAE1 gene sequences comparison analysis showed that there were two SNPs (No. 968 and No. 1265) in BjFAE1.1, two SNPs (No. 49 and No. 237) in BjFAE1.2, three of the four SNPs (No. 49, No. 968, and No. 1265) resulted in differences in the amino acid level. The No. 323 amino acid in BjFAE1.1 gene was changed (Thr → Ile) duo to the change of the No. 968 base (C→T)), which could explain the decrease of erucic acid content in B. juncea and B. rapa. The point mutation at the No. 1265 base (T→C) resulted in the change at No. 422 amino acid (Phe→Ser), which could partially explained partly explained the variations from high erucic acid to low erucic acid in Brassica juncea, but no difference was found in No. 1265 in B. rapa varieties with high and low erucic acid content. The mutation at No. 49 base (T→C) resulted in No.17 amino acid change (Phe→Leu), which could explained the variations from intermediate erucic acid to high erucic acid (erucic acid) in B. juncea. We compared the FAE1 gene sequences of the low erucic acid yellow mustard mutant called 1278-3 from northern Shaanxi and the varieties with low erucic acid from foreign countries, the results showed that their difference was only in No.1265 base.

Analysis of Characteristics and Heterosis ofThree-Line Parents in Hybrid Japonica Rice

ZHANG Hong-Gen,KONG Xian-Wang,ZHU Zheng-Bin,TANG Shu-Zhu,YI Chuan-Deng,GU Ming-H

Acta Agron Sin. 2010, 36(05):  801-809.  doi:10.3724/SP.J.1006.2010.00801

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Sixteen representative varieties each for BT-type cytoplasmic-nucleic male sterility (CMS) lines, maintainers and restorers were collected respectively, and 229 hybrid combinations were developed in this study. Then the correlations between parents and progenies were analysed on the all traits. The main results are as follows: (1) Compared with the maintainers, the restorers had higher plant height, thicker stalk and bigger panicle. The latent storage capacity of the maintainers and restorers was about 30 gram on an average, and the restorers had less tillers, lower seed setting rate and lower 1000-grain weigh, resulting in the lower yield per plant. The chalkiness degree of restorers was higher than that of maintainers, while the amylose content of restorers was significantly lower than that of maintainers. (2) The mid-parent heterosis of hybrid japonica rice was strong, while the over-parent heterosisof most characters was weak excepting the competitive advantage of growth vigor. The panicles of hybrid japonica rice were big, showing the positive heterosis, but the seed setting rate had a negative heterosis, which was the main limiting factor on the yield heterosis of hybrid japonica rice. (3) Analysis of the correlation between parents and their progenies indicated that the correlation between the character values of F₁ combinations and this mid-parent valueswas the best. Comparatively, the correlations between CMS lines and F₁ in heading date and total spikelets per panicle were significant, while the correlations of restorers and F₁ in plant height, filled grains per panicle, seed setting rate, yield per plant and quality characters were significant.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Quantitative Analysis on Root Morphological Characteristics Based on Image Analysis Method in Rice

GU Dong-Xiang,TANG Liang,CAO Wei-Xing,ZHU Yan

Acta Agron Sin. 2010, 36(05):  810-817.  doi:10.3724/SP.J.1006.2010.00810

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The objective of this study was to quantitatively analyze the change patterns of rice root morphological characteristics based on image analysis method in pot experiments with different nitrogen rates, water regimes, and rice cultivars in different years. WinRhizo software (WR) was used as the root image analysis tool, and two modes of LM and T200 were used to measure the root diameter and adventitious root length under two ranges of root diameter as 0–0.30 mm and 0.25–1.80 mm, respectively. The measurement results from WR were compared with those from Image-Pro Plus 6.0 software (IP). Then, the diameter ranges of different types of root were determined. On the basis of the dataset from WR, the statistical analysis were performed on rice root morphological characteristic indices, including dry weight, total volume, total surface area, total adventitious root length and number per plant at different growth stages. The results were as follows: (1) The average NRMSEs between WR (LM and T200) and IP for root diameters were 5.44% and 10.95%. (2) The diameter range of fine lateral root was circumscribed within 0.03–0.10 mm for all the experiments, coarse lateral and adventitious root were circumscribed within 0.10-0.30 and 0.30-1.40 mm for V1 (Nipponbare) and V2 (Wuxiangjing 14), but 0.10–0.25 and 0.25–1.65 mm for V3 (Yangdao 6). Following this method, the NRMSEs for adventitious root length measured by WR and IP were 10.78%–12.01%. (3) All indices increased rapidly in the growth process and reached or approached the maximum at heading, then increased slowly or decreased after heading. There were significant differences between treatments with different nitrogen rates from tillering to maturing on all indices. Increasing nitrogen rate accelerated the growth of roots, and especially enhanced the proportion of adventitious roots. Properly control of irrigation could promote the growth of roots and increase the proportion of lateral roots. All indices of V3 were significantly higher than these of other cultivars, and there were no significant differences between V1 and V2. The results indicated that it was feasible to measure morphological indices of different types of rice root by WR with different modes, and the methods used in this paper have a good accuracy and reliability. These results could provide a support for the quantitative analysis on root morphology of rice or other crops.

Regularity of Carotenoids and Anthocyanins Accumulation in Various Genotypes of Maize Kernel

CUI Li-Na,GAO Rong-Qi,SUN Ai-Qing,DONG Shu-Ting,ZHANG Hua-Yong

Acta Agron Sin. 2010, 36(05):  818-825.  doi:10.3724/SP.J.1006.2010.00818

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Colourful maize (Zea mays L.) kernel contains a huge amount of pigments such as carotenoids and anthocyanins, which is the main origin of natural pigments. Many studies focused on the extraction method and pigments characteristics, but the accumulation regulations of maize pigments have not been clear yet. Four maize varieties with different colours such as Zinuoxiang (purple), Xixingchinuo 1 (red), Xixingheinuo 1 (black), and Tebao 2 (yellow) were used to study the composition, distribution and accumulation regularity of maize pigments by bare-handed sections and spectrophotometry. The results showed that the pigments of Xixingchinuo 1 consisted of carotenoids and anthocyanins. The anthocyanins mainly existed in seed capsule, which appeared firstly at the top of embryo nearby the style vestige, and then extended around. The dorsum of maize kernels contained higher anthocyanins contents than the abdomen. The carotenoids mainly existed in embryo and endosperm, which first appeared at the top of kernels, and then extended around with the time. Carotenoids were the predominant pigments in Tebao 2, and their distribution and accumulation regularities were consistent with those in Xixingchinuo 1. The pigments of Zinuoxiang and Xixingheinuo 1 were mainly anthocyanins, which predominantly existed in aleurone layer of maize kernels. The anthocyanins appeared at the top of kernels firstly, the absorption peak of pigments of maize kernels (except in Zinuoxiang) decreased after an initial increase with the grain-filling time. At the early stage of grain-filling, the pigment contents of maize kernels in the different parts of maize spike showed the following regulations: the upper > the middle > the basal. While at the late stage of grain-filling, the pigments contents of middle part of kernels of maize spike were much higher than those of other two parts.

Diversity of Microbial Community of Paddy Soil Types in Double-Rice Cropping System

BU Hong-Zhen,WANG Li-Hong,XIAO Xiao-Ping,YANG Guang-Li,HU Yue-Gao,ZENG Zhao-Hai

Acta Agron Sin. 2010, 36(05):  826-832.  doi:10.3724/SP.J.1006.2010.00826

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Soil microbial communities play a central role in global biogeochemical cycle and soil organic transformation, according to the effect on the soil fertility and soil health. The objective of this study was to use phospholipid fatty acid (PLFA) profiles to characterize and identify microbial community structure among six paddy soil types. The results indicated that total twenty one PLFA (phospholipid fatty acid) profiles were detected among the six soil types, purple type had the highest content of fatty acid, with the value of 107.05 ng g^-1, and the lowest one was in river type whose value was 59.75 ng g^-1. The amounts of Gram-positive bacteria, Gram-negative bacteria, fungi were different among the six soil types, and the ratio between of them was also different. Principal component analyses of whole soil were conducted to determine microbial community structure of the 21 PLFAs detected in the six soil types, the main two principal components explained 76.7% of the total variance. All unsaturated PLFAs except C16:0 were highly expressed in the first principal component, the OH fatty acid were expressed in the second principal component.

Effect of Intracellular Calcium Stores on Hypersensitive Reaction Induced by Wheat Leaf Rust Fungus

ZHANG Bei,YAN Ai-Hua,LIU Gang,LIU Meng,HOU Chun-Yan,WANG Dong-Mei

Acta Agron Sin. 2010, 36(05):  833-839.  doi:10.3724/SP.J.1006.2010.00833

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With injecting drugs to affect intracellular calcium stores and calcium channel in Wheat (Triticum aestivum) leaves, we investigated hypersensitive reaction (HR) changes in wheat leaves invaded by leaf rust (Puccinia triticina). The results showed that the intracellular calcium chelators (BAPTA-AM) could obviously reduce the area of dying cells caused by HR. The higher the concentration was, the smaller the area of dying cell was. While intracellular calcium activator (caffeine) was injected into wheat leaves, HR could also be detected. The HR area increased with caffeine concentration. Calcium channel blockers (heparin, RR, and 8-Br-cADPR) were separately injected into wheat leaves before inoculation. The results showed that there was a concentration-depended effect on HR with herapin, and no obviously effect with RR and 8-Br-cADPR. Therefore, we deduced that intracellular calcium might involve in the formation of calcium signal transduction through IP₃ pathway during infection of wheat leaf rust fungus.

Evaluation of SPAD and Dualex for In-Season Corn Nitrogen Status Estimation

YU Huan,WU Hua-Song,WANG Zhi-Jie

Acta Agron Sin. 2010, 36(05):  840-847.  doi:10.3724/SP.J.1006.2010.00840

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Nitrogen (N) is one of the most important nutrients influencing both yield and grain quality, and N supply is one of the few production factors that can be controlled and which is known to effectively influence crop performance. Both SPAD reading and Dualex reading are shown to be highly correlated with leaf N concentration, and crop N status can be assessed through the SPAD reading and Dualex reading. The purpose of this study was to evaluate the suitable N rate at topdressing time. In order to evaluate the N application rates on SPAD reading and Dualex reading of corn after silking, corn field experiment was conducted with application of 45 kg N ha^-1 at sowing and planting density of 79 000 plants ha^-1 in 2008 on the L’Acadie experimental farm (Quebec, Canada). Topdressing N was performed with 0, 34, 68, 101, 135, 169 and 203 kg N ha^-1 at jointing stage. N-saturated reference plots with topdressing of 180 kg N ha^-1 at 10 days after sowing, besides 45 kg N ha^-1 at sowing, was established. With increasing topdressing N rates, SPAD reading, aboveground dry biomass and corn grain yield increased, and Dualex reading decreased. The SPAD-NSI of topdressing N treatments with 101, 135, 169 and 203 kg N ha^-1 was always higher than 0.95 at all samplings dates. The Dualex-NSI of topdressing N treatments with 101 kg N ha^-1 was higher than 0.95 from 18 d to 46 d; the Dualex-NSI of topdressing N treatments with 135, 169 and 203 kg N ha^-1 was also higher than 0.95 at all samplings dates. SPAD reading, Dualex reading, SPAD-NSI and Dualex-NSI were strongly correlated with topdressing N rates. The maximum yield was reached when topdressing N was 101 or 135 kg N ha^-1 at jointing stage. When maximum yield was reached, any additional N was no significant effect on SPAD reading, Dualex reading, aboveground dry biomass and corn grain yield. Topdressing N rate of 101 or 135 kg N ha^-1 was enough for corn growth after silking and getting maximum grain yield. There was no significant difference between splitting the N into two applications and N-saturated application on grain yield; however, splitting the N into two applications significantly decreased the total N application rate and growers’ inputs. In the present study, the suitable topdressing N rate was 101 or 135 kg N ha^-1 with 45 kg N ha^-1 at sowing. SPAD and Dualex could be integrated to evaluate in-season N status of corn.

Comparison of Multiplication of Endosperm Cell and Physiological Activity in Developing Kernels among Normal Corn, Glutinous Corn and Pop Corn

ZUO Zhen-Peng, WANG Jing, DONG Lu-Hao, MA Deng-Chao, SUN Qing-Quan, DONG Shu-Ting

Acta Agronomica Sinica. 2010, 36(05):  848-855.  doi:10.3724/SP.J.1006.2010.00848

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The multiplication of endosperm cell and the physiological characteristics in developing kernels were investigated among normal corn, glutinouscorn and pop corn in this study. The number of endosperm cell, the traits of carbohydrate accumulation, the change of hormone content and the activities of enzymes related to starch corn, the process of kernel endosperm cell proliferation was earlier than that of the dry matter increase; the number of kernel endosperm cells reached the maximum at 24, 18, 13 days after pollination, while kernel weight at 45, 40, 30 d respectively. In the process of starch accumulation, the total content of starch of glutinous corn was higher than that of normal corn and pop corn at the same period, especially at 30 d after pollination and the difference was obvious, and that between normal corn and pop corn was not distinct; the difference of the speed of kernel starch accumulation among different types was mainly manifested in two aspects faster or slower and earlier or later for accumulation. The maximum of glutinous corn starch accumulation rate was 1.61, 1.34 times higher than that of normal corn and pop corn. The maximum rate of starch accumulation of glutinous corn appeared at 10 d after pollination, while that of normal corn and pop corn at 20 d after pollination. The number of endosperm cell was significantly correlated with the filling rate of kernel in normal corn at the 0.01 probability level, and in glutinous corn at 0.05 level, while not significantly correlated in pop corn. In kernel-filling period, the content of ZR was higher in normal corn than in glutinous corn and pop corn at the same period, moreover, in the glutinous corn than in pop corn. The differences among the three typesin the content of IAA, ABA, and GA₃ were exactly opposite to those of ZR_. The difference of SS activity among the three quality types was not significant, but in later kernel-filling stage, the SS activity declined slowly in normal corn and fast in pop corn fast. The average activity of SSS and synthesis were compared in different types of corn. The results showed that for normal, glutinous and popADPG-PPase of glutinous corn was significantly higher than that of normal corn and pop corn in the kernel-filling period. The average activity of GBSS of pop corn was higher than that of normal corn and glutinous corn. The activity of GBSS for pop corn kernel was the highest one in the three corn types.

Effect of Increasing K Application Rate on Partial Physiological & Biochemical Parameters and Occurrence of Black Shank and Black Root Rot in Tobacco Variety Hongda

ZUO Li-Juan,ZHAO Zheng-Xiong,YANG Huan-Wen,DUAN Feng-Yun,WANG De-Xun,XU Fa-Hua

Acta Agron Sin. 2010, 36(05):  856-862.  doi:10.3724/SP.J.1006.2010.00856

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Flue-cured tobacco production plays an important role for the most farmers in Yunnan province. However, farmers are not willing to plant Hongdavariety, partly because the tobacco seedlings are much susceptible to black shank and black root rot even when fertilized with the same ratio of potassium as for the resistant varieties such as K326 and Yun 85. In addition to the genetic difference in resistance, whether potassium application rate recommended for Hongda variety in the production is sufficient to enhance its resistance to diease is not clear. Therefore, three potassium application rates, including 187.5 (CK, recommended in the production), 262.5 and 337.5 kg K₂O ha^–1, were designed to compare the tobacco seedlings’ resistance to black shank and black root rot in field experiment. The leaves were sampled from healthy tobacco plants (Nicotiana tabacum L. var. Hongda) at 33, 41, 62, 69, 76 days after transplanting (DAT), and some physiological-biochemical parameters such as contents of nitrogen, protein, free amino acid, soluble sugar, phenol and flavonoid were determined. Meanwhile, the severity of black shank and black root rot on tobacco plants was recorded in the field at 10-day interval from 24 DAT to 114 DAT. The results showed that the contents of N, protein and free amino acid reduced, the contents of flavonoid, phenol and soluble sugar in leaf increased when potassium application rate was raised. In addition, decreased severity of black shank and black root rot was observed with increasing potassium rate at 44, 54, 64, 74, 84, 94, 104 and 114 DAT. There was significant difference between the two treatments with K₂O application rate at 337.5 and 187.5 kg ha^–1 respectively in the parameters mentioned above. However, the leaf yield and economic value reached the peak when potassium was applied at 262.5 kg K₂O ha^–1. Compared with those of the control, the leaf yield and economic value increased by 4.49% and 18.27% respectively in the treatment with potassium application rate at 262.5 kg K₂O ha^–1, while by 1.55% and 12.34% respectively in the treatment with K₂O rate at 337.5 kg ha^–1. It suggested that potassium application rate recommended in the production of Nicotiana tabacum L.variety Hongda is inadequate, therefore a relatively higher potassium application rate, i.e. 262.5 kg K₂O ha^–1 in the experiment, should be preferred to decrease the severity of black shank and black root rot.

Mechanism of Tolerance to Drought in Sugarcane Plant Enhanced by Foliage Dressing of Abscisic Acid under Water Stress

LI Chang-Ning,Manoj Kumar SRIVASTAVA,NONG Qian,LI Yang-Rui

Acta Agron Sin. 2010, 36(05):  863-870.  doi:10.3724/SP.J.1006.2010.00863

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Drought is a major limiting factor for sugarcane growth. Abscisic acid (ABA) regulates much important plant physiological and biochemical processes, and induces tolerance to different stresses including drought. Understanding the mechanism of tolerance to drought in sugarcane plant with foliage dressing of ABA under water stress would facilitate breeding and field management for improving drought resistance. Thus, an experiment was set up to investigate the interrelationship between drought induced ABA biosynthesis and antioxidative defense system, and to confer the farther role of foliar application of ABA in imparting drought tolerance to the sugarcane plant. The treatments were: T1 (drought), T2 (drought + foliar application of 15 µmol L^–1 ABA) and C (control, normal irrigation) using a drought tolerant cultivar ROC22. The results showed that drought treatment (T1) enhanced the ABA concentration in leaf that was significantly higher in combined treatment (T2), suggesting the ABA biosynthesis was triggered in leaf by the ABA application. Both T1 and T2 resulted in an increase in proline, H₂O₂ and MDA contents while the exogenous ABA alleviated the increase in MDA content. ABA application decreased the degradation of chlorophyll, and counteracted, at least in part, the decrease in maximal PSII efficiency (F_v/F_m) and quantum efficiency of PSII (Φ_PSII). Overproduction of H₂O₂ in T1 was followed by increasing activities of CAT, GPX, GR, and APX, which was further improved by the ABA treatment (T2). A decrease in H₂O₂ level with increasing stress in T2 showed that ABA highly induced antioxidative defense system which was found to be vanished progressively in T1. The results clearly suggest that the tolerant cultivar showed an enhanced protective system against drought conditions, and the foliar application of ABA further improved its tolerance by triggering the over expression of antioxidative defense system.

RESEARCH NOTES

Effects of Panting Density on Photosynthetic Characteristics and Changes of Carbon and Nitrogen in Leaf of Different Corn Hybrids

CHEN Chuan-Yong, HOU Hai-Peng, LI Qiang, ZHU Ping, ZHANG Zhen-Yong, DONG Zhi-Qiang,

Acta Agronomica Sinica. 2010, 36(05):  871-878. 

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The main objective of this research was to analyse the effects of plant population on the dynamic changes of photosynthetic characteristics, soluble sugar content, carbon and nitrogen in corn leaf (Zea mays L.). Field experiments were conducted in Gongzhuling, Jilin province. Three corn hybrids were cultivated at 60 000, 75 000, 90 000, and 105 000 plants ha^-1. Treatments were arranged in a split-plot design with three replicates. Plant density was the main-plot and hybrids were the subplot. The chlorophyll content, photosynthetic characteristics, contents of carbon and nitrogen in corn leaf were measured at different stages, especially after silking. The results indicated thatthe chlorophyll content, the photosynthetic rate in grain filling stage, soluble sugar content, leaf total nitrogen decreased in all hybrids with the increase of plant density. It showed that transmission rate reduced, the leaf senescence accelerated, physical activity declined as plant density intensified. During the growth period, chlorophyll content was changed in a single peak curve, with the peak at grain filling. The peaks of carbon-nitrogen ratio appeared at silking and ripening respectively. The chlorophyll content, photosynthetic rate, soluble sugar content, ratio of carbon to nitrogen in corn leaf indicated a quadratic relationship with increasing days after silking. Total nitrogen in corn leaf decreased linearly in all hybrids as days after silking increased. High plant density had great effect on carbon metabolism. The chlorophyll content had no or little effect on the photosynthetic rate after silking. The results showed the dynamic changes of photosynthetic characteristics, contents of carbon and nitrogen were different as plant density intensified. The tolerance to planting density is Xianyu 335>Zhengdan 958>Jidan 209.

Genotypic Variation in Ammonia Volatilization Rate of Rice Shoots and Its Relationship with Nitrogen Use Efficiency

CHEN Ming-Xia, HUANG Jian-Liang, CUI Ke-Hui, NIE Li-Xiao, PENG Shao-Bing

Acta Agronomica Sinica. 2010, 36(05):  879-884.  doi:10.3724/SP.J.1006.2010.00879

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Gaseous nitrogen losses from rice plant tissues may be closely related to nitrogen use efficiency (NUE), the research on which may provide a theoretical supplement in nitrogen nutrition and a technical parameter for higher NUE genotype screening. Pot experiments under solution culture with four nitrogen concentrations of 0, 20, 40, and 80 mg N L^-1 respectively, were carried out to assess the correlation between ammonia volatilization rate (AVR) from booting stage to milking stage and NUE of different rice varieties including higher NUE type of Yangdao 6 and BG34-8, lower NUE type of Wuyujing 3 and Zhenshan 97B. The results showed that the peak AVR of Yangdao 6 and Wuyujing 3 was 11.0 and 10.4 mg N h^-1 pot^-1 respectively at panicle initiation stage, the peak AVR of BG34-8 and Zhenshan 97B was 22.5 and 23.4 mg N h^-1 pot^-1 respectively at booting stage. The AVR increased with the nitrogen concentration increasing in the culture solutions for a given genotype, the range of increase was larger in lower-NUE varieties Zhenshan 97B and Wuyujing 3 than in higher-NUE varieties Yangdao 6 and BG34-8. There were significantly negative correlations between AVR and aboveground nitrogen accumulation (r = -0.6768^**), NUE in grain production (r= -0.6158^*), fertilizer-N agronomic efficiency (r = -0.6667^**), and fertilizer-N physiological efficiency (r= -0.8353^**), when all the tested genotypes were cultured in higher nitrogen concentration of solution (80 mg N L^-1). The general conclusion of the research is that there are significant genotypic differences in AVR, and the higher-NUE genotypes have lower AVR than the lower-NUE genotypes. Hence, lower AVR under higher nitrogen concentration of culture could be an effective parameter for higher-NUE genotype screening.