Table of Content

12 April 2015, Volume 41 Issue 04

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Identification of Powdery Mildew Resistance Gene in Pea Line X9002

WANG Zhong-Yi,FU Hai-Ning,SUN Su-Li,DUAN Can-Xin,WU Xiao-Fei,YANG Xiao-Ming,ZHU Zhen-Dong

Acta Agron Sin. 2015, 41(04):  515-523.  doi:10.3724/SP.J.1006.2015.00515

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Powdery mildew is one of the major diseases in pea, causing severe economic loss worldwide. Planting resistant cultivars is the most effective, economical and eco-friendly method for controlling the disease. So far, two recessive resistance genes (er1, er2) and one dominant resistance gene (Er3) have been identified in pea, and er1 has been utilized in breeding programs worldwide. Gene er1 is a member of MLO gene family, and er1 resistance is caused by the loss of function at a PsMLO1 locus in pea. X9002 with resistance to powdery mildew is an afila pea line bred by Gansu Academy of Agricultural Sciences. Here, we identified the powdery mildew resistance gene in X9002, and developed molecular marker for the gene selection. Genetic analysis for powdery mildew resistance showed that X9002 carries a recessive resistance gene. The resistance gene was mapped in a region carrying er1 locus on the pea linkage group VI using SSR markers, and was linked to SSR marker AD60 and gene marker c5DNAmet. PsMLO1 sequence analysis revealed that X9002 carries an insertion of unknown size and identity. The same mutation also existed in pea cultivars Stratagem and Franklin carrying er1-2 allele, indicating that the resistance gene is er1-2 in X9002. A functional marker PsMLO1-650 for er1-2 was developed, and the marker was a coupling-phase marker that was detected only in susceptible plants. PsMLO1-650 can be used effectively in marker-assisted selection.

Enhancing Expression and Accumulation of Foreign Proteins by Using the Signal Peptide of Glutelin GluA-2 in Endosperm of Transgenic Rice

WANG Hong-Mei,ZHANG Chang-Quan,LI Qian-Feng,SUN Samuel Sing-Min,LIU Qiao-Quan,XU Ming-Liang

Acta Agron Sin. 2015, 41(04):  524-530.  doi:10.3724/SP.J.1006.2015.00524

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It is one of the key important techniques to enhance the expression of foreign proteins in target tissue/organ of transgenic plants. Glutelin is the major component of storage proteins in rice seeds, and its expression was tightly temporal and tissuespecific, which is controlled by several mechanisms. To further reveal the function of the Glutelin signal peptide on expression of target gene, in present study, we isolated the promoter and signal peptide-coding sequences of the glutelin GluA-2 gene, and fused them transcriptionally to the GUS coding sequences. Beside, the construct without the GluA-2 signal peptide-coding sequences was also generated as a control. Both constructs with the GUS chimeric genes, named as p13GSG and p13GG, were introduced into the same rice variety by Agrobacterium-mediated transformation. More than twenty independent transgenic lines were generated for each construct, and the integration of the GUS chimeric gene was confirmed by PCR technique. The results from Northern blot analysis showed that, after fusing the GluA-2 signal peptide coding sequences between the GluA-2 promoter and the GUS coding sequence, the transcription of GUS chimeric gene could be dramatically increased. Then, Western blot was carried out by using the GUS-specific antibody, and the results obviously revealed that the accumulation of foreign proteins was significantly
enhanced in the endosperm of transgenic rice with the signal peptide. However, there was no or very low GUS activity in the endosperm of transgenic rice plants with the signal peptide. These results were very useful to improve the grain quality of rice via genetic engineering, especially produce foreign proteins in the seeds of rice as bioreactor.

Phenolic Acid Synthesis of Allelopathic Rice Regulated by OsMYB and Its Weed Inhibition

SHEN Li-Hua,LI Bi-Liang,REN Yong-Jie,LI Cheng-Xun,ZHONG Yong-Jia,FANG Chang-Xun,LIN Wen-Xiong

Acta Agron Sin. 2015, 41(04):  531-538.  doi:10.3724/SP.J.1006.2015.00531

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Regulation of gene expression is a vital process in the formation of rice allelopathy. In this study, allelopathic rice PI312777 (Oryza sativa L.) was modified by RNA interference (RNAi) and overexpression(OE) technologies to inhibit or enhance gene expression of OsMYB (CT829537) in PI312777 respectively. The results showed that up-regulation of phenolic synthesis related genes was found in CT829537-OE transgenic PI312777 co-cultured with barnyardgrass (BYG), compared with that in wild type. However, the reverse was true in the CT829537-RNAi transgenic PI312777. Up-regulation of the gene expression in CT829537-OE transgenic PI312777 increased phenolic acids contents in rice root and root exudates, which led to enhance allelopathic inhibition on barnyardgrass. In contrast, decreases of phenolic acids contents and weed inhibition were found in CT829537-RNAi transgenic PI312777. These results implied that CT829537 is responsible for regulating phenolic synthesis in allelopathic rice PI312777 and then enhances allelopathic inhibition on weeds.

Cloning and Expression Analysis of Ghkinesin13 Subfamily Genes in Gossypium hirsutum

ZHAO Lan-Jie,XUE Fei,ZHU Shou-Hong,LI Yan-Jun,LIU Yong-Chang,SUN Jie

Acta Agron Sin. 2015, 41(04):  539-547.  doi:10.3724/SP.J.1006.2015.00539

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Kinesin family belongs to a class of motor proteins. Kinesins can move along microtubule filaments by using the energy released from ATP hydrolysis, and play key roles during cell formation and cell elongation. Using the protein sequence of Atkinesin13A as a probe, seven genes with high sequence homology were obtained from a genome database of Gossypium raimondii diploid cotton with Blast alignment. These sequences were used to design primers, and then seven genes were isolated from upland cotton fiberusing RT-PCR. Based on the homology level of the seven genes with Atkinesin13A and Atkinesin13B, we designated them as GhKIS13A1, GhKIS13A2, GhKIS13A3, GhKIS13B1, GhKIS13B2, GhKIS13B3, and GhKIS13B4 respectively. Bioinformatic analysis showed that seven proteins contained typical KISC domains including the central motor, ATP-binding sites and microtubule binding sites. Multiple sequence alignment and phylogenetic tree analysis revealed that seven genes can be divided into Kinesin13A and Kinesin13B. The qPCR showed that the seven Ghkinesin13 subfamily genes expressed in all tissues of cotton, but showed different expression patterns. Of the seven genes, only GhKIS13A4 was preferentially expressed in fibers, suggesting that it may play an important role in cotton fiber development. This study can provide a foundation for studying the functions of Ghkinesin13 subfamily genes in fiber development.

Influence of Canopy Temperature (CT)During Grain-Filling Period onYield and Effects of Several CT-Associated SSR Loci

ZHANG Dong-Ling,ZHANG Hong-Na,HAO Chen-Yang,WANG Lan-Fen，LI Tian,ZHANG Xue-Yong*

Acta Agron Sin. 2015, 41(04):  548-556.  doi:10.3724/SP.J.1006.2015.00548

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The canopy temperature (CT) during wheat growing period, especially after flowering, has a major impact on plant senescence, grain weight and quality. In this study, the relationship between CT and yield was analyzed using selected introgression lines derived from more than 60 accessions of Chinese wheat mini core collection crossed and backcrossed by four wheat varieties. The CT was negatively correlated with thousand-kernel weight and kernel yield, and positively correlated with spike number per plant. The correlation coefficientgradually became larger in the process of time. Lower CT during later grain-fillingprotected chlorophyll and photosynthesis,increasing thousand-kernel weight (TKW) and yield. Among the 44 loci associated with grain number (GN) and TKW detected previously, nine werealso associated with CT. Favored alleles were detected onsix loci. The CTs of varieties containing favored alleles were lower than those of varieties containing other alleles. Obvious additive effect was found among favored alleles affecting CT. Several favored alleles showed pleiotropic genetic effects, such as decreasing CT, increasing chlorophyll content and kernel weight.

Cold Hardiness and Its Relationship with the VRN1 Genotypes in Wheat Varieties in the Yellow-Huai-Hai River Valley Region of China

YOU Guang-Xia,SUN Guo-Zhong,ZHANG Xiu-Ying,XIAO Shi-He

Acta Agron Sin. 2015, 41(04):  557-564.  doi:10.3724/SP.J.1006.2015.00557

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Winter freezing injury is one of the major natural disasters in wheat production. The effect of VRN1 genes on cold hardness was analyzed with phenotypic data and the allelic variations of VRN-A1, VRN-B1, VRN-D1 in 71 wheat varieties grown in Yellow-Huai-Hai River Valley region. The results indicated that the cold hardiness of wheat was correlated with other stress tolerances, and strong cold hardiness was found in most varieties showing good salinity tolerance, drought tolerance or water-saving feature in production and the National Variety Regional Trial. VRN1 is a critical locus in the genetic network of wheat cold hardiness. The presence of the dominant gene VRN1 was often accompanied with a significant decrease in cold hardiness, and weak cold hardiness was usually detected in the varieties with two or three VRN1 genes. Coexistence of recessive genes vrn-A1, vrn-B1, and vrn-D1 was found to be an indispensable prerequisite for strong cold hardiness. Therefore, the vrn-A1vrn-B1vrn-D1 genotype is suggested in wheat production and variety improvement in the northern part of Yellow-Huai-Hai River Valley region of China.

Cloning of BnADH3 Gene from Brassica napus L. and Submergence Tolerance of BnADH3 Transgenic Arabidopsis

Lü Yan-Yan,FU San-Xiong,CHEN Song,ZHANG Wei,QI Cun-Kou*

Acta Agron Sin. 2015, 41(04):  565-573.  doi:10.3724/SP.J.1006.2015.00565

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BnADH3 gene was highly homologous to BoADH3 from Brassica oleracea and AtADH3 from Arabidopsis, with the BnADH3  expression was induced by submergence and the up-regulation occurred since 6-hour post treatment. The BnADH3 transgenic Arabidopsis was obtained and the transgenic seedBnADH3 gene was cloned from submergence-tolerant line WR-4 of Brassica napus L. using RT-PCR technique. The full-length open reading frame is 1137 bp, encoding 379 amino acids. Homology analysis showed that BnADH3 gene was highly homologous to BoADH3 from Brassica oleracea and AtADH3 from Arabidopsis, with the 96% and 91% similarity, respectively. Quantitative RT-PCR assay was carried out to compare BnADH3 expression between the submergence-tolerant line WR-4 and the submergence-susceptible line WR-24. The result showed that the BnADH3  expression was induced by submergence and the up-regulation occurred since 6-hour post treatment. The BnADH3 transgenic Arabidopsis was obtained and the transgenic seedlings were exposed to three-day submergence stress. Overexpression of BnADH3 resulted in higher ADH activity in leaf and root of transgenic Arabidopsis compared to that of the wild type. The four- and six-week seedlings of T₂ generation showed higher tolerance to submergence stress after three-day submergence treatment and most T₂ seedlings were recovered with normal growth when the stress was relieved for three days. However, the wild-type seedlings withered until death. After five-day submergence, the survival ratios were 26.7% for the wild type, 80.0% for transgenic line ADH33, and 66.7% for transgenic line ADH44.

Genetic Composition and Its Transmissibility Analysis of Wheat Candidate Backbone Parent Kenong 9204

ZHAO Chun-Hua,FAN Xiao-Li,WANG Wei-Lian,ZHANG Wei,HAN Jie,CHEN Mei,JI Jun,CUI Fa, LI Jun-Ming

Acta Agron Sin. 2015, 41(04):  574-584.  doi:10.3724/SP.J.1006.2015.00574

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Kenong 9204 (KN9204), a wheat cultivar with high yield potential and high nitrogen use efficiency (NUE), has a diverse genetic basis containing genetic materials of Jimai 38, Xiaoyan 5, Mianyang 75-18, Xiaoyan 693, and Aifeng 3. In this study, the genotypic map of KN9204 was released, which embraced 221 PCR-derived markers and 89 DArT markers. On chromosome 2DL, the region of Xmag3596–Xmag4089 harbored QTLs for increasing thousand-kernel weight and grain nitrogen content. On chromosome 4BL, Xcnl10 was close to the QTLs for increasingkernel number per spike and decreasing plant height and spike exsertion. On chromosome 6BS, Xcnl113 and Xwmc756 were closely linked with QTLs for decreasing plant height, spike exsertion and peduncle length. These markers had the transmissibility of 100% in the derivatives. The transmissibility of KN9204 elite genotypes was analyzed by known associated markers. The percentages of marker transmissibility from KN9204 to its derivates were 71.6% for one locus associated with kernel number per spike, 100.0% for four loci associated with thousand-kernel weight and 100.0% for three out of four loci associated with root traits. The high transmissibility of KN9204 genotypes on these loci might attribute to the excellent agronomictraits of KN9204. The important chromosomal regions harboring QTLs for elite agronomic traits are deduced to be the genetic basis of KN9204 serving as a candidate backbone parent.

Functional Analysis and Mapping of Gene P2SA2 Involved in Hypocotyl Phototropism of Arabidopsis thaliana

ZHAO Qing-Ping,ZHAO Xiang,MU Shi-Chao,XIAO Hui-Li,ZHANG Xiao

Acta Agron Sin. 2015, 41(04):  585-592.  doi:10.3724/SP.J.1006.2015.00585

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PHOT1 functions at both low and high-intensity blue light to mediate phototropic responses, but PHOT2 functions only at high-intensity blue light. The functional redundancy of PHOT1 and PHOT2 on high-intensity blue light-induced phototropic curvature of hypocotyls in Arabidopsis thaliana, restricts the understanding of the mechanism of PHOT2 signal transduction. Therefore, in order to avoid the interference of PHOT1, Arabidopsis phot1 mutant was selected as material for screening high blue light insensitive mutants by the EMS mutation, and we successfully screened and cloned the gene P2SA2 (phototropin2 signaling associated 2). The gene P2SA2 turned out to be the allelic of NPH3 (Nonphototropic hypocotyl 3). The mutation of gene P2SA2 could result in that Arabidopsis thaliana lost the phototropism to unilateral high intensity blue light. Transgenic plants of p2sa2 35S::P2SA2 restored hypocotyl phototropism to high intensity blue light. These findings will open new perspectives about the screening and functional identification of PHOT2 downstream genes in response to high blue light, and provide the theoretical basis to uncover hypocotyl bending mechanism regulated by PHOT2.

Cloning and Functional Identification of Promoter Region of GhWRKY64Induced by Multi-stresses in Cotton (Gossypium hirsutum)

DU Hao,DING Lin-Yun,HE Man-Lin,CAI Cai-Ping,GUO Wang-Zhen*

Acta Agron Sin. 2015, 41(04):  593-600. 

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WRKY proteins are members of a transcription factor family with Zinc-finger structure in higher plant, which play diverse roles in plant responses to stresses and in various physiological processes.A 1064bp promoter sequence of GhWRKY64 was isolated from Gossypium hirsutum acc. TM-1, and its regulatory elements and functional characterization were further analyzed. Bioinformatics analysis showed that there were 18 putative tissue-speci?c or stress-induced regulatory motifs corresponding to known cis-elements in eukaryotic genes, including six ROOTMOTIFTAPOX1 of root-specific regulatory elements, two W-boxes, four CACTFTPPCA1mesophyll-specific regulatory elements, four OSE2ROOTNODULE of pathogenic bacteria-induced elements, and two GTIGMSCAM4 of salt regulatory elements. Further, pGhWRKY64 promoter region was fused to a β-glucuronidase(GUS) reporter gene as pBIW64:GUS constructed for investigation of important regions controlling gene expression, and 12 transgenic tobacco plants were obtained by Agrobacterium-mediated leaf-disc transformation method. Further, pBIW64-5 line with the highest GUS expression was selected for different tissues/organs expression and induced expression analyses. Histochemical staining in seedlings stage of the transgenic tobacco plants showed that the full-length promoter directed ef?cient expression of the reporter gene in the root and leaf, however, no GUS activity was detected in non-transgenic control.When transgenic tobacco plants growed at the flowering stage,GUS activity in root, leaf and petiole was detected, especially in root and root tip with heavier staining than those in other tissues, but no GUS activity was detected in stem and flower tissues. After treatment with Verticilliumdahliae, pBIW64:GUS showed greater induction and stronger GUS activity than those in untreated transgenic tobacco plants. Taken together, pGhWRKY64 promoter with 1064bp iselite regulatory element for preferential accumulation of foreign genes in root and leaf tissues and stress responses, which will be used for transgenic research in cottonVerticillium dahliae-resistant breeding.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Responses of the Stomatal Traits and Gas Exchange of Maize Leaves to Climate Warming

ZHENG Yun-Pu,XU Ming,WANG Jian-Shu,QIU Shuai,WANG He-Xin

Acta Agron Sin. 2015, 41(04):  601-612.  doi:10.3724/SP.J.1006.2015.00601

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Stomata are the pores on leaf surfaces controlling gas exchanges, mainly CO₂ and water vapor, between the atmosphere and plants, and thus regulate carbon and water cycles in various ecosystems. This study investigated the effects of experimental warming on the stomatal frequency, stomatal aperture size and shape, and stomatal distribution pattern, and their relationships with the leaf gas exchange rates of maize (Zea may L.) leaves through a field manipulative warming experiment with infrared heaters in a typical agriculture ecosystem in the North China Plain. Our results showed that experimental warming had little effect on stomatal density, but increased stomatal index by 12% (P<0.05) due to the reduction in the number of epidermal cells under the warming treatment. Warming also decreased stomatal aperture length by 18% (P<0.01) and increased stomatal aperture width 26% (P<0.01). As a result, experimental warming increased the average stomatal aperture area by 31% (P<0.01) and stomatal aperture circumference by 13% (P<0.05), and resulted in a more regular stomatal distribution on both the adaxial and abaxial surfaces in leaves with an increased average nearest neighbor distance between stomata. In addition, experimental warming also affacted the gas exchange of maize leaves. Experimental warming significantly increased net photosynthetic rate (P_n), stomatal conductance (G_s), and transpiration rate (T_r) by 52% (P<0.05), 163% (P<0.001), and 81% (P<0.05), respectively. Meanwhile, experimental warming decreased the leaf dark respiration(R_d) by 24% (P<0.01), but had no significant effects on intercellular CO₂ concentration (C_i) and water use efficiency (WUE; P>0.05). In conclusion, the experimental warming may affect the gas exchange of maize leaves through the changes of the stomatal traits including stomatal frequency, stomatal aperture size and shape, and stomatal distribution on leaves.

Genetic Improvement of Root Growth and Its Relationship with Grain Yield of Wheat Cultivars in the Middle-Lower Yangtze River

TIAN Zhong-Wei,FAN Yong-Hui,YIN Mei,WANG Fang-Rui,CAI Jian,JIANG Dong,DAI Ting-Bo*

Acta Agron Sin. 2015, 41(04):  613-622.  doi:10.3724/SP.J.1006.2015.00613

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Exploring the characteristics of root growth, root physiology and their relationships to grain yield in wheat cultivars released in different decades will facilitate the development of new wheat cultivars, with stable and high yields and low nitrogen fertilizer input. Four wheat cultivars Nanda 2419, Yangmai 1, Yangmai 158, and Yangmai 16, which were bred or widely planted in the Middle-Lower Yangtze River Basin after 1950, were used in field and pot experiments in 2010–2011 with three nitrogen rates (pure N 0, 225, and 300 kg ha^-1). The results showed that, grain yield was improved with the genetic improvement in wheat breeding and the sensitivity of modern cultivars to N was greater as compared with early released cultivars. The root dry matter accumulation (DMA) and growth rate from jointing to anthesis of modern cultivars were higher than these of early released cultivars. The root length, root surface area, root volume and density of root weight in 0–60 cm soil layer were enhanced with the genetic improvement in wheat breeding, while no change was found in proportion of root distribution. The root activity, MDA concentration and SOD activity in modern cultivars were improved significantly. Higher N application increased root growth and physiological performance, with larger effects in modern cultivars, indicating that the response to N and high-N tolerance were promoted with genetic improvement in wheat breeding. In addition, these were significantly positive relations of grain yield with total root length, root surface area, root biomass and density of root weight in 0–60 cm soil layer. Therefore, higher contact area of the roots with soil and high-N adaptability, enhanced root physiological activity and N assimilation capacity, and delayed senescence of root system should be the important characteristics in cultivar evolution in the Middle-Lower Yangtze River,which are the main purpose getting in high-yield and high efficiency cultivation in this region.

Effects of Subsoiling-Seeding on Root Physiological Indices, Water-Saving and Yield-Increasing Behaviors in Summer Maize (Zea mays L.) in Haihe Lowland Plain

YIN Bao-Zhong,ZHEN Wen-Chao,FENG Yue

Acta Agron Sin. 2015, 41(04):  623-632.  doi:10.3724/SP.J.1006.2015.00623

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The study was carried out in Shenzhou Experimental Station, Arid Farming Research Institute, Hebei Academy of Agricultural and Forestry Sciences in 2012–2013. The maize variety Zhengdan 958 was used in this experiment with two treatments including sub-soiling seeding (SRT) and no-tillage seeding(NT). From seedling emergence to maturity, the root morphology, physiological parameters and microstructure, canopy photosynthetic characteristics, and leaf area index were regularly measured. At maturity, the yields and the water use efficiency and water storage in 2 m soil layer were investigated. The results showed that SRT increased the root dry mass, surface area, length and active absoiling area ratio in 0–60 cm soil layer, with the increase of 30.5%, 24.6%, 29.7%, and 56.3%,respectively, in comparison with NT. In addition, SRT also increased the proline content, nitrate reductase activity and activity of roots compared with NT in this soil layer, with the increase of 140%, 37%, and 36.5%, respectively. The total root bleeding sap in SRT increased by 15.2% compared with NT in the whole growth stage. In 0–40 cm soil layer, the hydraulic conductivity in single root and the roots per plant around whole growth stage in SRT increased by 15.8% and 17% respectively, in comparison with NT. In SRT, the diameter of stele vessel was increased, cell walls of pericycle and stele parenchyma were thickened, and the number of pith cells were increased, but its section area ratio in stale decreased compared with NT. Moreover, the numbers and diameter of xylem vessel in SRT increased, but the cortical thickness in roots decreased. In 0–20cm soil layer, although the middle cortical cells of root in SRT were larger than those of NT, but there number was only 86.2% of NT. SRT also increased the LAI and photosynthetic rate. The grain-filling rate in SRT treatment was also increased, with 5% higher than in NT. In two growth seasons, compared with NT, the spike kernels, 1000-grain weight, and yield in SRT treatment were increased by 2.4%, 3.9% and 8.2%, respectively, whereas the water consumption was reduced by 9.1%, the water use efficiency was increased by 14.4%, and the water storage amount in 2 m soil layer was increased by 31.7%.

Effect of Straw Returning and Reduced Tillage on Interspecific Competition and Complementation in Wheat/Maize Intercropping System

IN Wen**, ZHAO Cai**,YU Ai-Zhong, CHAI Qiang*, HU Fa-Long,FENG Fu-Xue

Acta Agron Sin. 2015, 41(04):  633-641.  doi:10.3724/SP.J.1006.2015.00633

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Conservation tillage has the advantages of enhancing water use efficiency and reducing water/energy consumption simultaneously in common cropping systems. However, this technique has not been well studied and practiced in intercropping system. A field experiment was conducted in 2011 and 2012 growing seasons to investigate the effects of different straw returning ways on crop yields, and interspecific competitiveness and complementation in wheat/maize intercropping system. Three wheat straw returning treatments were designed, which were no-tillage with 25 cm straw standing (NTSS), no-tillage with 25 cm straw covering (NTS), and tillage with 25 cm straw incorporation (TIS). Conventional tillage (CT) was used as the control. In the intercropping system, the land use efficiency (LER) of reduced tillage treatments under straw returning condition increased compared with that of CT, showing the intercropping superiority (LER>1). Simultaneously, the competitiveness of wheat with maize in the whole wheat growing duration decreased in treatments NTSS, NTS and TIS by 37–54%, 108–141%, and 22–24%, respectively. Compared with monocropping maize, intercropping maize had higher rates of relative growth with the increased percentages of 54–59% in NTSS, 66–71% in NTS, 61–63% in TIS and 71–78% in CT. Clearly, NTS showed the most effect on maize growth after wheat harvest. In the intercropping system, the total yields of both crops were 6–10% (2011) and 4–12% (2012) higher in the straw returning treatments than in CT. NTS exhibited the most significant effect on enhancing yield. A quadratic relationship was observed between the total yield of intercropping system and the competitivenessof wheatversus maize, and high yields of both crops were obtained when the competitiveness ranged from 0.24 to 0.27. Our results showed that straw returning in combination with reduced tillage is feasible to regulate the interspecific competitiveness in wheat/maize intercropping system, and NTS treatment is recommended.

Effects of Row Spacing on Crop Biomass, Root Morphology and Yield in Maize-Soybean Relay Strip Intercropping System

YANG Feng,LOU Ying,LIAO Dun-Ping,GAO Ren-Cai,YONG Tai-Wen,WANG Xiao-Chun,LIU Wei-Guo,YANG Wen-Yu

Acta Agron Sin. 2015, 41(04):  642-650.  doi:10.3724/SP.J.1006.2015.00642

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Spatial patterns of cropping directly affect crop growth and yields in intercropping systems. A two year field experiment was conducted in 2012−2013 to analyze the effects of different row spacing patterns in maize and soybean relay strip intercropping system at 2:2 maize-to-soybean on crop biomass, root morphology and yield. The treatments were six row spacing patterns including four maize planting patterns with the control of sole cropping of maize and soybean. The maize planting patterns were compound of wide row and narrow row lying: “180+20” cm, “160+40” cm, “140+60” cm, and “120+80” cm. Soybean was planted in the wide rows before the reproductive stage of maize. The row spacing of the sole cropping of maize and soybean was 70 cm. The biomass, total root length, root surface area and root volume of intercropped soybean increased from V3 to R2, and decreased with increasing the maize narrow-row spacing. The above- and below-ground biomass of intercropped maize increased from tasseling to maturity stages, whereas opposite results were found in root volume. In addition, the intercropped maize biomass and root volume increased with increasing maize narrow-row spacing. The yields of maize and soybean in intercropping condition were lower than those in monoculture. Yield of intercropped maize increased with increasing the maize narrow-row spacing, with an average of two year maximum values of 6181 kg ha^-1. Contrary trends were observed in intercropped soybean, with an average maximum yield of 1434 kg ha^-1. Crop grain yield was related to effective plants and grain numbers per plant in maize-soybean relay strip intercropping system. Total intercropping yields were higher than sole cropping yields of maize and soybean, and the land equivalent ratio (LER) of the intercropping system was above 1.3. The maximum LER appeared in “60+40” cm treatment, which was 1.59 and 1.61 in 2012 and 2013, respectively. Similar results were found in economic benefit, the average of maximum value in both years was 19.3 thousand Yuan per hectare. Therefore, optimum row spacing pattern plays an important role in improving crop growth and increasing yield in maize-soybean relay strip intercropping system.

RESEARCH NOTES

Molecular Identification of Leaf Rust Resistance Gene in Wheat Line 5R625

QIN Jin-Yan,LI Zai-Feng,YAN Xiao-Cui,SU Ji-Hua,YAO Zhan-Jun,LIU Da-Qun

Acta Agron Sin. 2015, 41(04):  651-657.  doi:10.3724/SP.J.1006.2015.00651

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Wheat line 5R625 shows high resistance to all of Puccinia triticinapathotypes at seedling and adult plant stages, but its resistance mechanism is unclear. In this study, the resistance gene(s) were postulated by artificially inoculating 15 P. triticinapathotypes at the seedling stage and comparing infection types with those of 36 wheat lines with known Lr genes. The result showed that 5R625 might carry Lr9, Lr19, Lr24, Lr28, Lr39, Lr47, Lr51,and Lr53. Further genetic analysis to confirm the resistance gene(s) was carried out using the populations of F_l, F₂, and F_2:3 derived from the cross between 5R625 and Zhengzhou 5389 (susceptible control). A single dominant gene was found responsible for the resistance at seedling and adult plant stages. This gene was mapped on 3DL chromosome with molecular markers using the F_2:3 lines. The linkage map contained five closely linked markers, including STS marker 24-16 and SCAR marker OP-J09 that have proved to be cosegregated with Lr24. Therefore, the leaf rust resistance gene in 5R625is most likely Lr24.

Establishment of 20 Sorghum Hybrids Fingerprints Using SSR Fluorescent Marker

WANG Rui,ZHANG Fu-Yao,CHENG Qing-Jun,TIAN Cheng-Hua,LING Liang

Acta Agron Sin. 2015, 41(04):  658-665.  doi:10.3724/SP.J.1006.2015.00658

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To establish a standard technical system for purity and authenticity identification of sorghum seeds,it is necessary to construct a DNA fingerprinting database of major sorghum hybrids. The fluorescent marker detection of simple sequence repeat (SSR) was used to establish SSR fingerprints of 20 sorghum hybrids that are popularized in medium and late-maturing areas in China since heterosis has been utilized. Thirty-six pairs of SSR primers were screened and 235 alleles were amplified with the set of primers. The number of alleles per locus ranged from two to twelve with an average of seven. The range of gene diversity and polymorphism information content (PIC) at 36 SSR loci of 20 hybrids were 0.3490–0.8813 and 0.3144–0.8696, with an average of 0.6976 and 0.6571, respectively. Among 36 SSR primers, two primer pairs with high polymorphism were identified as the specific primers for distinguishing the all 20 sorghum hybrids, resulting in the fingerprints for the 20 sorghum hybrids. The presented data and technology provides an important basis for hybrids identification in sorghum.

Secretion of Citrate from Root Apices and Expression of SGA1 in Soybean under AlCl3 Stress

YANG Lie-Geng,YANG Shu,ZHANG Yong-Xian,TANG Jian,LI Xiao-Feng

Acta Agron Sin. 2015, 41(04):  666-670.  doi:10.3724/SP.J.1006.2015.00666

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The effects of Al³⁺ on the secretion of organic acids from root apices and the expression of SGAI gene were investigated by hydroponics to elucidate the characteritics of organic acid secretion and Al³⁺ stress signal transduction pathway which mediates the secretion of organic acids in soybean Guangzhou 2. The results showed that soybean root apices (in vivo) secreted citrate under Al³⁺ stress. The secretion of citrate increased with the increase of Al³⁺ concentrations (25, 50 µmol L^–1 AlCl₃) and the prolongation (2–12 hours) of treatment with Al³⁺. Citrate was secreted from root apices by pattern II in soybean. The secretion rate was very low within initial four hours after Al³⁺ treatment but remarkably elevated thereafter. A gap of time between the secretion and Al³⁺ treatment reached to about six hours. On the other hand when cholera toxin, an inhibitor of heterotrimeric G-protein, was added to Al³⁺solution, the amount of citrate secreted decreased by 38.7%. RT-PCR analysis results indicated that Al³⁺ induced SGA1 expression. In general, the expression level was elevated with the prolongation of treatment with Al³⁺ (0.5 to 12 hours). Moreover, Al³⁺ induced expression of SGA1 sooner than the secretion of citrate. These results imply that Al³⁺ induces  the secretion of citrate from root apices and SGA1 expression in the soybean, and heterotrimeric G proteins may act as a switch of Al³⁺ stress signal to be involved in the regulation of citrate secretion from root apices under Al³⁺ stress.