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Most Cited The Crop Journal Articles

The most cited articles published since 2014, extracted from Scopus.

QTL IciMapping: Integrated software for genetic linkage map construction and quantitative trait locus mapping in biparental populations

Volume 3, Issue 3, June 2015, Pages 269-283
Lei Meng | Huihui Li | Luyan Zhang | Jiankang Wang

© 2015 Crop Science Society of China and Institute of Crop Science, CAAS QTL IciMapping is freely available public software capable of building high-density linkage maps and mapping quantitative trait loci (QTL) in biparental populations. Eight functionalities are integrated in this software package: (1) BIN: binning of redundant markers; (2) MAP: construction of linkage maps in biparental populations; (3) CMP: consensus map construction from multiple linkage maps sharing common markers; (4) SDL: mapping of segregation distortion loci; (5) BIP: mapping of additive, dominant, and digenic epistasis genes; (6) MET: QTL-by-environment interaction analysis; (7) CSL: mapping of additive and digenic epistasis genes with chromosome segment substitution lines; and (8) NAM: QTL mapping in NAM populations. Input files can be arranged in plain text, MS Excel 2003, or MS Excel 2007 formats. Output files have the same prefix name as the input but with different extensions. As examples, there are two output files in BIN, one for summarizing the identified bin groups and deleted markers in each bin, and the other for using the MAP functionality. Eight output files are generated by MAP, including summary of the completed linkage maps, Mendelian ratio test of individual markers, estimates of recombination frequencies, LOD scores, and genetic distances, and the input files for using the BIP, SDL, and MET functionalities. More than 30 output files are generated by BIP, including results at all scanning positions, identified QTL, permutation tests, and detection powers for up to six mapping methods. Three supplementary tools have also been developed to display completed genetic linkage maps, to estimate recombination frequency between two loci, and to perform analysis of variance for multi-environmental trials.

From leaf to whole-plant water use efficiency (WUE) in complex canopies: Limitations of leaf WUE as a selection target

Volume 3, Issue 3, June 2015, Pages 220-228
Hipólito Medrano | Magdalena Tomás | Sebastià Martorell | Jaume Flexas | Esther Hernández | Joan Rosselló | Alicia Pou | José Mariano Escalona | Josefina Bota

© 2015 Crop Science Society of China and Institute of Crop Science, CAAS Plant water use efficiency (WUE) is becoming a key issue in semiarid areas, where crop production relies on the use of large volumes of water. Improving WUE is necessary for securing environmental sustainability of food production in these areas. Given that climate change predictions include increases in temperature and drought in semiarid regions, improving crop WUE is mandatory for global food production. WUE is commonly measured at the leaf level, because portable equipment for measuring leaf gas exchange rates facilitates the simultaneous measurement of photosynthesis and transpiration. However, when those measurements are compared with daily integrals or whole-plant estimates of WUE, the two sometimes do not agree. Scaling up from single-leaf to whole-plant WUE was tested in grapevines in different experiments by comparison of daily integrals of instantaneous water use efficiency [ratio between CO2assimilation (AN) and transpiration (E); AN/E] with midday AN/E measurements, showing a low correlation, being worse with increasing water stress. We sought to evaluate the importance of spatial and temporal variation in carbon and water balances at the leaf and plant levels. The leaf position (governing average light interception) in the canopy showed a marked effect on instantaneous and daily integrals of leaf WUE. Night transpiration and respiration rates were also evaluated, as well as respiration contributions to total carbon balance. Two main components were identified as filling the gap between leaf and whole plant WUE: the large effect of leaf position on daily carbon gain and water loss and the large flux of carbon losses by dark respiration. These results show that WUE evaluation among genotypes or treatments needs to be revised.

Phytohormones and their metabolic engineering for abiotic stress tolerance in crop plants

Volume 4, Issue 3, June 2016, Pages 162-176
Shabir H. Wani | Vinay Kumar | Varsha Shriram | Saroj Kumar Sah

© 2016 Crop Science Society of China and Institute of Crop Science, CAAS Abiotic stresses including drought, salinity, heat, cold, flooding, and ultraviolet radiation causes crop losses worldwide. In recent times, preventing these crop losses and producing more food and feed to meet the demands of ever-increasing human populations have gained unprecedented importance. However, the proportion of agricultural lands facing multiple abiotic stresses is expected only to rise under a changing global climate fueled by anthropogenic activities. Identifying the mechanisms developed and deployed by plants to counteract abiotic stresses and maintain their growth and survival under harsh conditions thus holds great significance. Recent investigations have shown that phytohormones, including the classical auxins, cytokinins, ethylene, and gibberellins, and newer members including brassinosteroids, jasmonates, and strigolactones may prove to be important metabolic engineering targets for producing abiotic stress-tolerant crop plants. In this review, we summarize and critically assess the roles that phytohormones play in plant growth and development and abiotic stress tolerance, besides their engineering for conferring abiotic stress tolerance in transgenic crops. We also describe recent successes in identifying the roles of phytohormones under stressful conditions. We conclude by describing the recent progress and future prospects including limitations and challenges of phytohormone engineering for inducing abiotic stress tolerance in crop plants.

Magnesium deficiency in plants: An urgent problem

Volume 4, Issue 2, April 2016, Pages 83-91
Wanli Guo | Wanli Guo | Hussain Nazim | Zongsuo Liang | Zongsuo Liang | Dongfeng Yang | Dongfeng Yang

© 2015 Crop Science Society of China and Institute of Crop Science, CAAS Although magnesium (Mg) is one of the most important nutrients, involved in many enzyme activities and the structural stabilization of tissues, its importance as a macronutrient ion has been overlooked in recent decades by botanists and agriculturists, who did not regard Mg deficiency (MGD) in plants as a severe health problem. However, recent studies have shown, surprisingly, that Mg contents in historical cereal seeds have markedly declined over time, and two thirds of people surveyed in developed countries received less than their minimum daily Mg requirement. Thus, the mechanisms of response to MGD and ways to increase Mg contents in plants are two urgent practical problems. In this review, we discuss several aspects of MGD in plants, including phenotypic and physiological changes, cell Mg2 +homeostasis control by Mg2 +transporters, MGD signaling, interactions between Mg2 +and other ions, and roles of Mg2 +in plant secondary metabolism. Our aim is to improve understanding of the influence of MGD on plant growth and development and to advance crop breeding for Mg enrichment.

Anatomical and chemical characteristics associated with lodging resistance in wheat

Volume 1, Issue 1, October 2013, Pages 43-49
Eryan Kong | Dongcheng Liu | Xiaoli Guo | Wenlong Yang | Jiazhu Sun | Xin Li | Kehui Zhan | Dangqun Cui | Jinxing Lin | Aimin Zhang | Aimin Zhang

© 2013 China Agricultural University Anatomical and chemical characteristics of stems affect lodging in wheat (Triticum aestivum L.) cultivars. Traits associated with lodging resistance, such as plant height, stem strength, culm wall thickness, pith diameter, and stem diameter, were extensively investigated in earlier studies. However, the solid stem trait was rarely considered. In this study, we measured a range of anatomical and chemical characteristics on solid and hollow stemmed wheat cultivars. Significant correlations were detected between resistance to lodging and several anatomical features, including width of mechanical tissue, weight of low internodes, and width of stem walls. Morphological features that gave the best indication of improved lodging resistance were increased stem width, width of mechanical tissue layer, and stem density. Multiple linear regression analysis showed that 99% of the variation in lodging resistance could be explained by the width of the mechanical tissue layer, suggesting that solid stemmed wheat has several anatomical features for increasing resistance to lodging. In addition, microsatellite markers GWM247 and GWM340 were linked to a single solid stem QTL on chromosome 3BL in a population derived from the cross Xinongshixin (solid stem)/Line 3159 (hollow stem). These markers should be valuable in breeding wheat for solid stem.

CRISPR/Cas9: A powerful tool for crop genome editing

Volume 4, Issue 2, April 2016, Pages 75-82
Gaoyuan Song | Meiling Jia | Kai Chen | Xingchen Kong | Bushra Khattak | Chuanxiao Xie | Aili Li | Long Mao

© 2016 Crop Science Society of China and Institute of Crop Science, CAAS The CRISPR/Cas9 technology is evolved from a type II bacterial immune system and represents a new generation of targeted genome editing technology that can be applied to nearly all organisms. Site-specific modification is achieved by a single guide RNA (usually about 20 nucleotides) that is complementary to a target gene or locus and is anchored by a protospacer-adjacent motif. Cas9 nuclease then cleaves the targeted DNA to generate double-strand breaks (DSBs), which are subsequently repaired by non-homologous end joining (NHEJ) or homology-directed repair (HDR) mechanisms. NHEJ may introduce indels that cause frame shift mutations and hence the disruption of gene functions. When combined with double or multiplex guide RNA design, NHEJ may also introduce targeted chromosome deletions, whereas HDR can be engineered for target gene correction, gene replacement, and gene knock-in. In this review, we briefly survey the history of the CRISPR/Cas9 system invention and its genome-editing mechanism. We also describe the most recent innovation of the CRISPR/Cas9 technology, particularly the broad applications of modified Cas9 variants, and discuss the potential of this system for targeted genome editing and modification for crop improvement.

Effect of subsoil tillage depth on nutrient accumulation, root distribution, and grain yield in spring maize

Volume 2, Issue 5, October 2014, Pages 297-307
Hongguang Cai | Wei Ma | Xiuzhi Zhang | Jieqing Ping | Xiaogong Yan | Jianzhao Liu | Jingchao Yuan | Lichun Wang | Jun Ren

© 2014 Crop Science Society of China and Institute of Crop Sciences, CAAS A four-year field experiment was conducted to investigate the effect of subsoiling depth on root morphology, nitrogen (N), phosphorus (P), and potassium (K) uptake, and grain yield of spring maize. The results indicated that subsoil tillage promoted root development, increased nutrient accumulation, and increased yield. Compared with conventional soil management (CK), root length, root surface area, and root dry weight at 0–80 cm soil depth under subsoil tillage to 30 cm (T1) and subsoil tillage to 50 cm (T2) were significantly increased, especially the proportions of roots in deeper soil. Root length, surface area, and dry weight differed significantly among three treatments in the order of T2 > T1 > CK at the 12-leaf and early filling stages. The range of variation of root diameter in different soil layers in T2 treatment was the smallest, suggesting that roots were more likely to grow downwards with deeper subsoil tillage in soil. The accumulation of N, P, and K in subsoil tillage treatment was significantly increased, but the proportions of kernel and straw were different. In a comparison of T1 with T2, the grain accumulated more N and P, while K accumulation in kernel and straw varied in different years. Grain yield and biomass were increased by 12.8% and 14.6% on average in subsoil tillage treatments compared to conventional soil treatment. Although no significant differences between different subsoil tillage depths were observed for nutrient accumulation and grain yield, lodging resistance of plants was significantly improved in subsoil tillage to 50 cm, a characteristic that favors a high and stable yield under extreme environments.

Molecular approaches unravel the mechanism of acid soil tolerance in plants

Volume 1, Issue 2, December 2013, Pages 91-104
Miao Bian | Miao Bian | Miao Bian | Meixue Zhou | Dongfa Sun | Chengdao Li

© 2013 Acid soil is a worldwide problem to plant production. Acid toxicity is mainly caused by a lack of essential nutrients in the soil and excessive toxic metals in the plant root zone. Of the toxic metals, aluminum (Al) is the most prevalent and most toxic. Plant species have evolved to variable levels of tolerance to aluminum enabling breeding of high Al-tolerant cultivars. Physiological and molecular approaches have revealed some mechanisms of Al toxicity in higher plants. Mechanisms of plant tolerance to Al stress include: 1) exclusion of Al from the root tips, and 2) absorbance, but tolerance of Al in root cells. Organic acid exudation to chelate Al is a feature shared by many higher plants. The future challenge for Al tolerance studies is the identification of novel tolerance mechanisms and the combination of different mechanisms to achieve higher tolerance. Molecular approaches have led to significant progress in explaining mechanisms and detection of genes responsible for Al tolerance. Gene-specific molecular markers offer better options for marker-assisted selection in breeding programs than linked marker strategies. This paper mainly focuses on recent progress in the use of molecular approaches in Al tolerance research.

Total phenolic, flavonoid content, and antioxidant activity of flour, noodles, and steamed bread made from different colored wheat grains by three milling methods

Volume 3, Issue 4, August 2015, Pages 328-334
Yaoguang Li | Dongyun Ma | Dongyun Ma | Dexiang Sun | Chenyang Wang | Chenyang Wang | Jian Zhang | Yingxin Xie | Tiancai Guo | Tiancai Guo

© 2015 Crop Science Society of China and Institute of Crop Science, CAAS The objective of this study was to evaluate the effects of wheat variety, food processing, and milling method on antioxidant properties. Black wheat variety Heibaoshi 1 had the highest total phenolic content (659.8 μg gallic acid equivalents g− 1), total flavonoid content (319.3 μg rutin equivalents g− 1), and antioxidant activity, whereas light purple wheat variety Shandongzimai 1 had the lowest total flavonoid content (236.2 μg rutin equivalents g− 1) and antioxidant activity. Whole wheat flour and partially debranned grain flour had significantly higher total phenolic contents, total flavonoid contents, and antioxidant activity than refined flour (P < 0.05). Compared with flour, total phenolic contents, total flavonoid contents and antioxidant activity decreased in noodles and steamed bread, whereas noodles had slightly higher total phenolic and flavonoid content than steamed bread. Antioxidant activities (by ferric reducing ability of plasma assay) of steamed bread made from whole wheat flour, partially debranned grain flour, and refined flour were 23.5%, 21.1%, and 31.6% lower, respectively, than the corresponding values of flour. These results suggested that black whole wheat flour and partially debranned grain flour are beneficial to human health.

Genome-wide analysis of the WRKY transcription factor gene family in Gossypium raimondii and the expression of orthologs in cultivated tetraploid cotton

Volume 2, Issues 2-3, April 2014, Pages 87-101
Caiping Cai | Erli Niu | Hao Du | Liang Zhao | Yue Feng | Wangzhen Guo

© 2014 Crop Science Society of China and Institute of Crop Sciences, CAAS WRKY proteins are members of a family of transcription factors in higher plants that function in plant responses to various physiological processes. We identified 120 candidate WRKY genes from Gossypium raimondii with corresponding expressed sequence tags in at least one of four cotton species, Gossypium hirsutum, Gossypium barbadense, Gossypium arboreum, and G. raimondii. These WRKY members were anchored on 13 chromosomes in G. raimondii with uneven distribution. Phylogenetic analysis showed that WRKY candidate genes can be classified into three groups, with 20 members in group I, 88 in group II, and 12 in group III. The 88 genes in group II were further classified into five subgroups, groups IIa–e, containing 7, 16, 37, 15, and 13 members, respectively. We characterized diversity in amino acid residues in the WRKY domain and/or other zinc finger motif regions in the WRKY proteins. The expression patterns of WRKY genes revealed their important roles in diverse functions in cotton developmental stages of vegetative and reproductive growth and stress response. Structural and expression analyses show that WRKY proteins are a class of important regulators of growth and development and play key roles in response to stresses in cotton.

Estimation of biomass in wheat using random forest regression algorithm and remote sensing data

Volume 4, Issue 3, June 2016, Pages 212-219
Li'ai Wang | Xudong Zhou | Xinkai Zhu | Zhaodi Dong | Wenshan Guo

© 2016 Wheat biomass can be estimated using appropriate spectral vegetation indices. However, the accuracy of estimation should be further improved for on-farm crop management. Previous studies focused on developing vegetation indices, however limited research exists on modeling algorithms. The emerging Random Forest (RF) machine-learning algorithm is regarded as one of the most precise prediction methods for regression modeling. The objectives of this study were to (1) investigate the applicability of the RF regression algorithm for remotely estimating wheat biomass, (2) test the performance of the RF regression model, and (3) compare the performance of the RF algorithm with support vector regression (SVR) and artificial neural network (ANN) machine-learning algorithms for wheat biomass estimation. Single HJ-CCD images of wheat from test sites in Jiangsu province were obtained during the jointing, booting, and anthesis stages of growth. Fifteen vegetation indices were calculated based on these images. In-situ wheat above-ground dry biomass was measured during the HJ-CCD data acquisition. The results showed that the RF model produced more accurate estimates of wheat biomass than the SVR and ANN models at each stage, and its robustness is as good as SVR but better than ANN. The RF algorithm provides a useful exploratory and predictive tool for estimating wheat biomass on a large scale in Southern China.

Induced defense responses in rice plants against small brown planthopper infestation

Volume 2, Issue 1, February 2014, Pages 55-62
Canxing Duan | Jiaojiao Yu | Jianyu Bai | Zhendong Zhu | Xiaoming Wang

© 2013 Crop Science Society of China and Institute of Crop Sciences, CAAS The small brown planthopper (SBPH), Laodelphax striatellus Fallén (Homoptera: Delphacidae), is a serious pest of rice (Oryza sativa L.) in China. To understand the mechanisms of rice resistance to SBPH, defense response genes and related defense enzymes were examined in resistant and susceptible rice varieties in response to SBPH infestation. The salicylic acid (SA) synthesis-related genes phenylalanine ammonia-lyase (PAL), NPR1, EDS1 and PAD4 were induced rapidly and to a much higher level in the resistant variety Kasalath than in the susceptible cultivar Wuyujing 3 in response to SBPH infestation. The expression level of PAL in the Kasalath rice at 12 h post-infestation (hpi) increased 7.52-fold compared with the un-infested control, and the expression level in Kasalath was 49.63, 87.18, 57.36 and 75.06 times greater than that in Wuyujing 3 at 24, 36, 48 and 72 hpi, respectively. However, the transcriptional levels of the jasmonic acid (JA) synthesis-related genes LOX and AOS2 in resistant Kasalath were significantly lower than in susceptible Wuyujing 3 at 24, 36, 48 and 72 hpi. The activities of the defense enzymes PAL, peroxidase (POD), and polyphenol oxidase (PPO) increased remarkably in Kasalath in response to SBPH infestation, and were closely correlated with the PAL gene transcript level. Our results indicated that the SA signaling pathway was activated in the resistant Kasalath rice variety in response to SBPH infestation and that the gene PAL played a considerable role in the resistance to SBPH.

Resistance to Aspergillus flavus in maize and peanut: Molecular biology, breeding, environmental stress, and future perspectives

Volume 3, Issue 3, June 2015, Pages 229-237
Jake C. Fountain | Pawan Khera | Pawan Khera | Liming Yang | Brian T. Scully | Robert D. Lee | Zhi Yuan Chen | Pawan Khera | Spurthi N. Nayak | Liming Yang | Liming Yang | Rajeev K. Varshney | Baozhu Guo | Robert C. Kemerait

© 2015 The colonization of maize (Zea mays L.) and peanut (Arachis hypogaea L.) by the fungal pathogen Aspergillus flavus results in the contamination of kernels with carcinogenic mycotoxins known as aflatoxins leading to economic losses and potential health threats to humans. The regulation of aflatoxin biosynthesis in various Aspergillus spp. has been extensively studied, and has been shown to be related to oxidative stress responses. Given that environmental stresses such as drought and heat stress result in the accumulation of reactive oxygen species (ROS) within host plant tissues, host-derived ROS may play an important role in cross-kingdom communication between host plants and A. flavus. Recent technological advances in plant breeding have provided the tools necessary to study and apply knowledge derived from metabolomic, proteomic, and transcriptomic studies in the context of productive breeding populations. Here, we review the current understanding of the potential roles of environmental stress, ROS, and aflatoxin in the interaction between A. flavus and its host plants, and the current status in molecular breeding and marker discovery for resistance to A. flavus colonization and aflatoxin contamination in maize and peanut. We will also propose future directions and a working model for continuing research efforts linking environmental stress tolerance and aflatoxin contamination resistance in maize and peanut.

The impacts of conservation agriculture on crop yield in China depend on specific practices, crops and cropping regions

Volume 2, Issue 5, October 2014, Pages 289-296
Chengyan Zheng | Chengyan Zheng | Yu Jiang | Changqing Chen | Yanni Sun | Jinfei Feng | Jinfei Feng | Aixing Deng | Aixing Deng | Zhenwei Song | Zhenwei Song | Weijian Zhang | Weijian Zhang | Weijian Zhang

© 2014 Crop Science Society of China and Institute of Crop Sciences, CAAS For smooth and wide application of conservation agriculture (CA), remaining uncertainties about its impacts on crop yield need to be reduced. Based on previous field experiments in China, a meta-analysis was performed to quantify the actual impacts of CA practices (NT: no/reduced-tillage only, CTSR: conventional tillage with straw retention, NTSR: NT with straw retention) on crop yields as compared to conventional tillage without straw retention (CT). Although CA practices increased crop yield by 4.6% on average, there were large variations in their impacts. For each CA practice, CTSR and NTSR significantly increased crop yield by 4.9% and 6.3%, respectively, compared to CT. However, no significant effect was found for NT. Among ecological areas, significant positive effects of CA practices were found in areas with an annual precipitation below 600 mm. Similar effects were found in areas with annual mean air temperature above 5 °C. For cropping regions, CA increased crop yield by 6.4% and 5.5% compared to CT in Northwest and South China, respectively, whereas no significant effects were found in the North China and Northeast China regions. Among crops, the positive effects of CA practices were significantly higher in maize (7.5%) and rice (4.1%) than in wheat (2.9%). NT likely decreased wheat yield. Our results indicate that there are great differences in the impacts of CA practices on crop yield, owing to regional variation in climate and crop types. CA will most likely increase maize yield but reduce wheat yield. It is strongly recommended to apply CA with crop straw retention in maize cropping areas and seasons with a warm and dry climate pattern.

Identification and fine mapping of two blast resistance genes in rice cultivar 93-11

Volume 1, Issue 1, October 2013, Pages 2-14
Cailin Lei | Kun Hao | Yilong Yang | Jian Ma | Shuai Wang | Jiulin Wang | Zhijun Cheng | Shasha Zhao | Xin Zhang | Xiuping Guo | Chunming Wang | Jianmin Wan | Jianmin Wan

© 2013 China Agricultural University Rice blast, caused by Magnaporthe oryzae, is a major disease of rice almost worldwide. The Chinese indica cultivar 93-11 is resistant to numerous isolates of the blast fungus in China, and can be used as broad-spectrum resistance resource, particularly in japonica rice breeding programs. In this study, we identified and mapped two blast resistance genes, Pi60(t) and Pi61(t), in cv. 93-11 using F2and F3populations derived from a cross between the susceptible cv. Lijiangxintuanheigu (LTH) and resistant cv. 93-11 and inoculated with M. oryzae isolates from different geographic origins. Pi60(t) was delimited to a 274 kb region on the short arm of chromosome 11, flanked by InDel markers K1-4 and E12 and cosegregated with InDel markers B1 and Y10. Pi61(t) was mapped to a 200 kb region on the short arm (near the centromere) of chromosome 12, flanked by InDel markers M2 and S29 and cosegregating with InDel marker M9. In the 274 kb region of Pi60(t), 93-11 contains six NBS-LRR genes including the two Pia/PiCO39 alleles (BGIOSGA034263 and BGIOSGA035032) which are quite close to the two Pia/PiCO39 alleles (SasRGA4 and SasRGA5) in Sasanishiki and CO39, with only nine amino acids differing in the protein sequences of BGIOSGA035032 and SasRGA5. In the 200 kb region of Pi61(t), 93-11 contains four NBS-LRR genes, all of which show high identities in protein sequence with their corresponding NBS-LRR alleles in susceptible cv. Nipponbare. Comparison of the response spectra and physical positions between the target genes and other R genes in the same chromosome regions indicated that Pi60(t) could be Pia/PiCO39 or its allele, whereas Pi61(t) appears to be different from Pita, Pita-2, Pi19(t), Pi39(t) and Pi42(t) in the same R gene cluster. DNA markers tightly linked to Pi60(t) and Pi61(t) will enable marker-assisted breeding and map-based cloning.

SSR genetic linkage map construction of pea (Pisum sativum L.) based on Chinese native varieties

Volume 2, Issues 2-3, April 2014, Pages 170-174
Xuelian Sun | Xuelian Sun | Tao Yang | Tao Yang | Junjie Hao | Xiaoyan Zhang | Rebecca Ford | Junye Jiang | Junye Jiang | Fang Wang | Fang Wang | Jianping Guan | Jianping Guan | Xuxiao Zong | Xuxiao Zong

© 2014 Crop Science Society of China and Institute of Crop Sciences, CAAS Simple sequence repeat (SSR) markers have previously been applied to linkage mapping of the pea (Pisum sativum L.) genome. However, the transferability of existing loci to the molecularly distinct Chinese winter pea gene pool was limited. A novel set of pea SSR markers was accordingly developed. Together with existing SSR sequences, the genome of the G0003973 (winter hardy) × G0005527 (cold sensitive) cross was mapped using 190 F2individuals. In total, 157 SSR markers were placed in 11 linkage groups with an average interval of 9.7 cM and total coverage of 1518 cM. The novel markers and genetic linkage map will be useful for marker-assisted pea breeding.

Rank correlation among different statistical models in ranking of winter wheat genotypes

Volume 2, Issues 2-3, April 2014, Pages 154-163
Mozaffar Roostaei | Reza Mohammadi | Ahmed Amri

© 2014 Crop Science Society of China and Institute of Crop Sciences, CAAS Several statistical methods have been developed for analyzing genotype × environment (GE) interactions in crop breeding programs to identify genotypes with high yield and stability performances. Four statistical methods, including joint regression analysis (JRA), additive mean effects and multiplicative interaction (AMMI) analysis, genotype plus GE interaction (GGE) biplot analysis, and yield–stability (YSi) statistic were used to evaluate GE interaction in 20 winter wheat genotypes grown in 24 environments in Iran. The main objective was to evaluate the rank correlations among the four statistical methods in genotype rankings for yield, stability and yield–stability. Three kinds of genotypic ranks (yield ranks, stability ranks, and yield–stability ranks) were determined with each method. The results indicated the presence of GE interaction, suggesting the need for stability analysis. With respect to yield, the genotype rankings by the GGE biplot and AMMI analysis were significantly correlated (P < 0.01). For stability ranking, the rank correlations ranged from 0.53 (GGE–YSi; P < 0.05) to 0.97 (JRA–YSi; P < 0.01). AMMI distance (AMMID) was highly correlated (P < 0.01) with variance of regression deviation (S2di) in JRA (r = 0.83) and Shukla stability variance (σ2) in YSi (r = 0.86), indicating that these stability indices can be used interchangeably. No correlation was found between yield ranks and stability ranks (AMMID, S2di, σ2, and GGE stability index), indicating that they measure static stability and accordingly could be used if selection is based primarily on stability. For yield–stability, rank correlation coefficients among the statistical methods varied from 0.64 (JRA–YSi; P < 0.01) to 0.89 (AMMI–YSi; P < 0.01), indicating that AMMI and YSi were closely associated in the genotype ranking for integrating yield with stability performance. Based on the results, it can be concluded that YSi was closely correlated with (i) JRA in ranking genotypes for stability and (ii) AMMI for integrating yield and stability.

Rapeseed research and production in China

Volume 5, Issue 2, April 2017, Pages 127-135
Qiong Hu | Wei Hua | Yan Yin | Xuekun Zhang | Lijiang Liu | Jiaqin Shi | Yongguo Zhao | Lu Qin | Chang Chen | Hanzhong Wang

© 2016 Rapeseed (Brassica napus L.) is the largest oilseed crop in China and accounts for about 20% of world production. For the last 10 years, the production, planting area, and yield of rapeseed have been stable, with improvement of seed quality and especially seed oil content. China is among the leading countries in rapeseed genomic research internationally, having jointly with other countries accomplished the whole genome sequencing of rapeseed and its two parental species, Brassica oleracea and Brassica rapa. Progress on functional genomics including the identification of QTL governing important agronomic traits such as yield, seed oil content, fertility regulation, disease and insect resistance, abiotic stress, nutrition use efficiency, and pod shattering resistance has been achieved. As a consequence, molecular markers have been developed and used in breeding programs. During 2005–2014, 215 rapeseed varieties were registered nationally, including 210 winter- and 5 spring-type varieties. Mechanization across the whole process of rapeseed production was investigated and operating instructions for all relevant techniques were published. Modern techniques for rapeseed field management such as high-density planting, controlled-release fertilizer, and biocontrol of disease and pests combined with precision tools such as drones have been developed and are being adopted in China. With the application of advanced breeding and production technologies, in the near future, the oil yield and quality of rapeseed varieties will be greatly increased, and more varieties with desirable traits, especially early maturation, high yield, high resistance to biotic and abiotic stress, and suitability for mechanized harvesting will be developed. Application of modern technologies on the mechanized management of rapeseed will greatly increase grower profit.

Moderate wetting and drying increases rice yield and reduces water use, grain arsenic level, and methane emission

Volume 5, Issue 2, April 2017, Pages 151-158
Jianchang Yang | Qun Zhou | Jianhua Zhang

© 2016 Crop Science Society of China and Institute of Crop Science, CAAS To meet the major challenge of increasing rice production to feed a growing population under increasing water scarcity, many water-saving regimes have been introduced in irrigated rice, such as an aerobic rice system, non-flooded mulching cultivation, and alternate wetting and drying (AWD). These regimes could substantially enhance water use efficiency (WUE) by reducing irrigation water. However, such enhancements greatly compromise grain yield. Recent work has shown that moderate AWD, in which photosynthesis is not severely inhibited and plants can rehydrate overnight during the soil drying period, or plants are rewatered at a soil water potential of − 10 to − 15 kPa, or midday leaf potential is approximately − 0.60 to − 0.80 MPa, or the water table is maintained at 10 to 15 cm below the soil surface, could increase not only WUE but also grain yield. Increases in grain yield WUE under moderate AWD are due mainly to reduced redundant vegetative growth; improved canopy structure and root growth; elevated hormonal levels, in particular increases in abscisic acid levels during soil drying and cytokinin levels during rewatering; and enhanced carbon remobilization from vegetative tissues to grain. Moderate AWD could also improve rice quality, including reductions in grain arsenic accumulation, and reduce methane emissions from paddies. Adoption of moderate AWD with an appropriate nitrogen application rate may exert a synergistic effect on grain yield and result in higher WUE and nitrogen use efficiency. Further research is needed to understand root–soil interaction and evaluate the long-term effects of moderate AWD on sustainable agriculture.

Genetic dissection of tetraploid cotton resistant to Verticillium wilt using interspecific chromosome segment introgression lines

Volume 2, Issue 5, October 2014, Pages 278-288
Peng Wang | Zhiyuan Ning | Ling Lin | Hong Chen | Hongxian Mei | Jun Zhao | Bingliang Liu | Xin Zhang | Wangzhen Guo | Tianzhen Zhang

© 2014 Crop Science Society of China and Institute of Crop Sciences, CAAS Verticillium wilt (caused by the pathogen Verticillium dahliae) is of high concern for cotton producers and consumers. The major strategy for controlling this disease is the development of resistant cotton (Gossypium spp.) cultivars. We used interspecific chromosome segment introgression lines (CSILs) to identify quantitative trait loci (QTL) associated with resistance to Verticillium wilt in cotton grown in greenhouse and inoculated with three defoliating V. dahliae isolates. A total of 42 QTL, including 23 with resistance-increasing and 19 with resistance-decreasing, influenced host resistance against the three isolates. These QTL were identified and mapped on 18 chromosomes (chromosomes A1, A3, A4, A5, A7, A8, A9, A12, A13, D1, D2, D3, D4, D5, D7, D8, D11, and D12), with LOD values ranging from 3.00 to 9.29. Among the positive QTL with resistance-increasing effect, 21 conferred resistance to only one V. dahliae isolate, suggesting that resistance to V. dahliae conferred by most QTL is pathogen isolate-specific. The At subgenome of cotton had greater effect on resistance to Verticillium wilt than the Dt subgenome. We conclude that pyramiding different resistant QTL could be used to breed cotton cultivars with broad-spectrum resistance to Verticillium wilt.

Enhanced tolerance to drought in transgenic rice plants overexpressing C4photosynthesis enzymes

Volume 1, Issue 2, December 2013, Pages 105-114
Jun Fei Gu | Ming Qiu | Jian Chang Yang

© 2013 Crop Science Society of China and Institute of Crop Sciences, CAAS Maize-specific pyruvate orthophosphate dikinase (PPDK) was overexpressed in rice independently or in combination with the maize C4-specific phosphoenolpyruvate carboxylase (PCK). The wild-type (WT) cultivar Kitaake and transgenic plants were evaluated in independent field and tank experiments. Three soil moisture treatments, well-watered (WW), moderate drought (MD) and severe drought (SD), were imposed from 9 d post-anthesis till maturity. Leaf physiological and biochemical traits, root activities, biomass, grain yield, and yield components in the untransformed WT and two transgenic rice lines (PPDK and PCK) were systematically studied. Compared with the WT, both transgenic rice lines showed increased leaf photosynthetic rate: by 20%–40% under WW, by 45%–60% under MD, and by 80%–120% under SD. The transgenic plants produced 16.1%, 20.2% and 20.0% higher grain yields than WT under the WW, MD and SD treatments, respectively. Under the same soil moisture treatments, activities of phosphoenolpyruvate carboxylase (PEPC) and carbonic anhydrase (CA) in transgenic plants were 3–5-fold higher than those in WT plants. Compared with ribulose-1,5-bisphosphate carboxylase, activities of PEPC and CA were less reduced under both MD and SD treatments. The transgenic plants also showed higher leaf water content, stomatal conductance, transpiration efficiency, and root oxidation activity and a stronger active oxygen scavenging system than the WT under all soil moisture treatments, especially MD and SD. The results suggest that drought tolerance is greatly enhanced in transgenic rice plants overexpressing C4photosynthesis enzymes. This study was performed under natural conditions and normal planting density to evaluate yield advantages on a field basis. It may open a new avenue to drought-tolerance breeding via overexpression of C4enzymes in rice.

Grain quality changes and responses to nitrogen fertilizer of japonica rice cultivars released in the Yangtze River Basin from the 1950s to 2000s

Volume 3, Issue 4, August 2015, Pages 285-297
Junfei Gu | Jing Chen | Lu Chen | Zhiqin Wang | Hao Zhang | Jianchang Yang

© 2015 Crop Science Society of China and Institute of Crop Science, CAAS While the yield potential of rice has increased but little is known about the impact of breeding on grain quality, especially under different levels of N availability. In order to investigate the integrated effects of breeding and N levels on rice quality 12 japonica rice cultivars bred in the past 60 years in the Yangtze River Basin were used with three levels of N: 0 kg N ha− 1, 240 kg N ha− 1, and 360 kg N ha− 1. During the period, milling quality (brown rice percentage, milled rice percentage, and head rice percentage), appearance quality (chalky kernels percentage, chalky size, and chalkiness), and eating and cooking quality (amylose content, gel consistency, peak viscosity, breakdown, and setback) were significantly improved, but the nutritive value of the grain has declined due to a reduction in protein content. Micronutrients, such as Cu, Mg, and S contents, were decreased, and Fe, Mn, Zn, Na, Ca, K, P, B contents were increased. These changes in grain quality imply that simultaneous improvements in grain yield and grain quality are possible through selection. Overall, application of N fertilizer decreased grain quality, especially in terms of eating and cooking quality. Under higher N levels, higher protein content was the main reason for deterioration of grain quality, although lower amylose content might contribute to improving starch pasting properties. These results suggest that further improvement in grain quality will depend on both breeding and cultivation practices, especially in regard to nitrogen and water management.

Differences between soybean genotypes in physiological response to sequential soil drying and rewetting

Volume 2, Issue 6, December 2014, Pages 366-380
Md Mokter Hossain | Xueyi Liu | Xusheng Qi | Hon Ming Lam | Jianhua Zhang

© 2014 Crop Science Society of China and Institute of Crop Sciences, CAAS Soybean genotypes show diverse physiological responses to drought, but specific physiological traits that can be used to evaluate drought tolerance have not been identified. In the present study we investigated physiological traits of soybean genotypes under progressive soil drying and rewetting, using a treatment mimicking field conditions. After a preliminary study with eight soybean genotypes, two drought-tolerant genotypes and one susceptible genotype were grown in the greenhouse and subjected to water restriction. Leaf expansion rate, gas exchange, water relation parameters, total chlorophyll (Chl), proline contents of leaves, and root xylem pH were monitored in a time course, and plant growth and root traits were measured at the end of the stress cycle. Drought-tolerant genotypes maintained higher leaf expansion rate, net photosynthetic rate (Pn), Chl content, instantaneous water use efficiency (WUEi), % relative water content (RWC), water potential (ψw), and turgor potential (ψp) during progressive soil drying and subsequent rewetting than the susceptible genotypes. By contrast, stomatal conductance (gs) and transpiration rate (Tr) of tolerant genotypes declined faster owing to dehydration and recovered more sharply after rehydration than the same parameters in susceptible ones. Water stress caused a significant increase in leaf proline level and root xylem sap pH of both genotypes but tolerant genotypes recovered to pre-stress levels more quickly after rehydration. Tolerant genotypes also produced longer roots with higher dry mass than susceptible genotypes. We conclude that rapid perception and adjustment in response to soil drying and rewetting as well as the maintenance of relatively high Pn, %RWC, and root growth constitute the mechanisms by which drought-tolerant soybean genotypes cope with water stress.

Yield and tillering response of super hybrid rice Liangyoupeijiu to tillage and establishment methods

Volume 2, Issue 1, February 2014, Pages 79-86
M. A. Badshah | Tu Naimei | Yingbin Zou | M. Ibrahim | Ke Wang

© 2013 Tillering is an important agronomic trait for rice grain production. To evaluate yield and tillering response, Liangyoupeijiu (super hybrid rice) was grown in Hunan, China during 2011–2012 under different methods of tillage (conventional and no-tillage system) and crop establishment methods (transplanting at a spacing of 20 cm × 20 cm with one seedling per hill and direct seeding at a seeding rate of 22.5 kg ha− 1). Our results revealed that, at maximum tillering (Max.) and at maturity (MA) stages, direct seeding (DS) resulted in 22% more tillers than transplanting (TP) irrespective of tillage system. Tiller mortality reached a peak between panicle initiation (PI) and booting (BT) stages, and was 16% higher under conventional tillage (CT) than under no-tillage (NT). Transplanting required 29% more time for the completion of tillering and less for DS. Tillering rate was 43% higher in DS than TP under either CT or NT. There was a positive correlation between panicle number per m2and maximum tiller number per m2, but not panicle-bearing tiller rate. The panicle bearing tiller rate was higher under DS than TP and higher under NT than CT. Tiller dry weight gradually increased up to heading (HD) stage, and was 14% higher under TP than DS. Leaf area (cm2 tiller− 1) gradually increased from Max. to HD stage and then decreased by 34% in conventional tillage transplanting (CTTP) and 45% in no-tillage transplanting (NTTP) from 12DAH–24DAH (days after heading), but was similar (35%) under DS under either CT or NT. Grain yield was higher under CTTP owing to the larger sink size (heavier panicle, more spikelets in per cm length of panicle) than under DS.

Mapping and validation of a dominant salt tolerance gene in the cultivated soybean (Glycine max) variety Tiefeng 8

Volume 2, Issue 6, December 2014, Pages 358-365
Rongxia Guan | Jiangang Chen | Jinghan Jiang | Guangyu Liu | Ying Liu | Lei Tian | Lili Yu | Ruzhen Chang | Li juan Qiu

© 2014 Crop Science Society of China and Institute of Crop Sciences, CAAS Salt is an abiotic stress factor that strongly affects soybean growth and production. A single dominant gene has been shown to confer salt tolerance in the soybean cultivar Tiefeng 8. The objective of the present study was to genetically map the salt-tolerance gene in an F2:3population and a recombinant inbred line (RIL) population derived from a cross between two cultivated soybeans, Tiefeng 8 (tolerant) and 85-140 (sensitive). The F2:3families and RILs were treated with 200 mmol L− 1NaCl to evaluate salt tolerance. The F2:3population showed 1 (42 tolerant): 2 (132 segregating): 1 (65 sensitive) segregation, indicating a single dominant gene for salt tolerance in Tiefeng 8. A sequence-characterized amplified region (SCAR) marker from a previously identified random amplified polymorphic DNA (RAPD) marker and four insertion/deletion polymorphism (InDel) markers were developed within the mapping region. Using these markers along with SSR markers, the salt-tolerance gene was mapped within 209 kb flanked by SCAR marker QS08064 and SSR marker Barcsoyssr_3_1301 on chromosome 3. Three markers that cosegregated with the salt tolerance gene and SCAR marker QS08064 were used to genotype 35 tolerant and 23 sensitive soybean accessions. These markers showed selection efficiencies of 76.2% to 94.2%. The results indicate that these markers will be useful for marker-assisted breeding and facilitating map-based cloning of the salt tolerance gene in soybean.

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