Scientia Agricultura Sinica

QTL Mapping of Protein and Related Functional Components Content in Barley Grains

YANG XiaoMeng, DU Juan, ZENG YaWen, PU XiaoYing, YANG ShuMing, YANG Tao, WANG LuXiang, YANG I JiaZhen

Scientia Agricultura Sinica. 2017, 50(2): 205-215. doi:10.3864/j.issn.0578-1752.2017.02.001

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【Objective】The objective of this study is to identify the QTLs controlling protein content, total flavonoids content, gamma-aminobutyric acid (GABA) content in barley grains and analyze their correlation, which could be a theoretical basis for genetic modification, gene cloning and molecular assisted breeding of the functional barley. 【Method】Based on two-year experiment data, a barley SSR genetic linkage map constructed by a total of 193 RIL population derived from the cross between Ziguangmangluoerleng (female parent) and Schooner (male parent) and the Inclusive Composite Interval Mapping(ICIM) method was used to identify the QTLs of protein, total flavonoids and GABA content. The correlations among the contents of three components were also analyzed. 【Result】 The two parents and RIL population have significant differences in protein, total flavonoids, and GABA content, showed continuous variation and normal distribution, which are suitable for QTL mapping. The map covered 2224.29cM with a mean density of 16.48cM per locus, including 7 linkage groups and 135 marker loci. A total of 20 QTLs for protein content, total flavonoids content, GABA content were detected. Nine QTL for protein content were localized on chromosomes 1H, 2H, 4H, 6H and 7H. It explained phenotypic variation range from 4.11% to 18.86%, 3 major QTL were localized on 6H and 7H, which explained 13.30%, 15.45% and 18.86% phenotypic variance. Two of the same QTL loci were found that localized on 4H BMAG0740-BMAG0808 and 6H Ebmac0806-GBM1270 based on two-year experiment. Seven QTL for total flavonoids content were localized on chromosomes 2H, 5H, 6H and 7H. It explained phenotypic variation range from 6.06% to 29.01%, 5 major QTL were localized on 2H, 6H and 7H, which explained 10.38%, 15.27%, 17.55%, 24.17% and 29.01% phenotypic variance. One of the same QTL loci was found that localized on 7H EBmatc0016-Bmag0206 based on two-year experiment. Four QTL for GABA content were localized on chromosome 4H, 5H, 6H and 7H. It explained phenotypic variation range from 5.44% to 14.87%, the highest phenotypic variance was 14.87%, which localized on 7H. QTLs controlling protein content and total flavonoids content were mapped and mainly localized on 2H, 6H and 7H, QTLs controlling protein content and GABA content were mainly localized on 4H, 6H and 7H, QTLs controlling total flavonoids content and GABA content were mainly localized on 5H, 6H and 7H. So QTLs for three components were mainly localized on 6H and 7H, especially on the 6H Ebmac0806-GBM1270 interval, and they all affected protein, total flavonoids and GABA content, the contribution rates of additive effects were the same, and there was a significantly correlation. The correlation analysis showed that the significantly positive correlations were existed among protein, total flavonoids and GABA content. 【Conclusion】the correlations of protein content, total flavonoids content, GABA content are consistent with the correlations of QTLs controlling those components. It revealed the close genetic relationship between protein and functional components.

Elite Alleles-Based Molecular Detection for Verticillium Wilt Resistance in Cotton

ZHAO YunLei, WANG HongMei, CHEN Wei, GONG HaiYan, SANG XiaoHui, CUI YanLi, ZHAO Pei

Scientia Agricultura Sinica. 2017, 50(2): 216-227. doi:10.3864/j.issn.0578-1752.2017.02.002

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【Objective】Detecting Verticillium wilt resistance in cotton by using molecular markers of elite alleles of Verticillium wilt resistance contributes to fast identification of disease resistance and direct selection of disease resistance genotypes, thus resolving the problems of time-consuming and poor efficiency in selection of disease resistance. 【Method】In this study, Verticillium wilt resistance of 125 elite cotton lines was estimated by using a disease nursery and greenhouse screening method, respectively. Elite alleles related to Verticillium wilt resistance were obtained from the earlier publication of the authors and the phenotypic effect of each elite allele was calculated. The number and the sum of effective value of elite alleles in each cotton line were used to study the possibility of elite alleles-based molecular detection for Verticillium wilt resistance. 【Result】Results of the study showed that widespread variation of Verticillium wilt resistance was observed in upland cotton. The range of relative disease index of Verticillium wilt resistance identified in field disease nursery and in greenhouse was 10.10-76.6 and 17.01-72.63, respectively. A total of 40 elite alleles were obtained and the effective values of each allele was in the range of -8.20--0.39. The number of elite alleles in each lines was in the range of 1-24. The sum of effective values of elite alleles in each line were in the range of -92.37--0.86. Correlation analysis showed that the sum of effective values of elite alleles had a significant positive correlation with relative disease index of Verticillium wilt resistance, and the correlation coefficient in field disease nursery and in greenhouse was 0.616 and 0.566, the number of elite alleles in each line had a significant negative correlation with relative disease index of Verticillium wilt resistance, and the correlation coefficient in field disease nursery and in greenhouse was -0.618 and -0.535, respectively. 【Conclusion】It was concluded that there is a significant correlation between the number of elite alleles, the sum of effective value of elite alleles and relative disease index of Verticillium wilt resistance, implying the accumulation of different elite alleles in one line can improve the disease resistance. The sum of effective value of elite alleles and the number of elite alleles in a cotton line can reflect the disease resistance, thus realizing the molecular identification of disease resistance in cotton.

Genome Wide Association Analysis of Silique Length in Brassica napus L.

ZHOU QingHong, ZHOU Can, ZHENG Wei, FU DongHui

Scientia Agricultura Sinica. 2017, 50(2): 228-239. doi:10.3864/j.issn.0578-1752.2017.02.003

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【Objective】The objective of this study is to detect the SNP loci and determine related candidate genes affecting the silique length of B. napus significantly to reveal its genetic basis and molecular mechanism, and lay a foundation for the marker assisted selection in high yield breeding of B. napus. 【Method】In this study, the phenotype of silique length was investigated at two environments (JXAU of Nanchang and JXIRS of Jinxian) with 300 accessions of B. napus, combining with the 201,817 SNPs developed from specific locus amplified fragment sequencing (SLAF-seq) technology, the genome-wide association analysis was proceeded to detect the SNP loci affecting the silique length significantly, and the regions were scanned with 100 kb apart from the loci of SNP associated dramatically with silique length based on linkage disequilibrium analysis, and finally the candidate genes were predicted with relation to silique length by BLAST analysis.【Result】The variation ranges of silique length in the two places were 46.35-107.07 mm and 39.41-101.35 mm, respectively, which both showed extensive phenotypic variation in two environments. In addition, a total of 121 SNP loci in JXAU correlatively with silique length were excavated by general linear model (GLM), which distributed on A04, A06, A08, A09, C02, C03, C06 and C09 chromosomes, and the largest number of SNPs (83) was on A09 chromosome. Otherwise, 22 SNPs in JXIRS with 1 on C09 and 21 on A09 were detected, and there were 20 consensus SNPs under two environments. Besides, 5 SNPs in JXAU and 3 SNPs (P＜4.96E-07) in JXIRS all distributed on A09 chromosome were detected respectively using the mixed linear model (MLM), three of which were consistent in two environments. There were 40 candidate genes screened in the candidate regions with 100 kb apart from the positions of SNPs associated significantly with silique length, functional analyses showed that these genes involved in regulation of carbohydrate transportation and synthesis, flower and seed development, signal transduction and etc., which might result in the variation of silique length through affecting the growth and development of silique in B. napus. 【Conclusion】The SNP loci and candidate genes related closely with silique length of B. napus were detected in this study, thus providing a theoretical basis for the seed yield regulatory network of B. napus and molecular assisted selection of high-yield breeding of rapeseed.

Analysis of Moisture State and Transverse Relaxation Characteristics of Grains During the Growth Process of Rice

SHAO XiaoLong, WANG Nan, SHI XiaoZhuan, SHEN Fei, SONG Wei, ZHANG Qiang

Scientia Agricultura Sinica. 2017, 50(2): 240-249. doi:10.3864/j.issn.0578-1752.2017.02.004

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【Objective】This paper is mainly to observe the changes of moisture state of grains during the growth process of rice after heading by LF-NMR, and investigate the effects of accumulation of starch and protein on the moisture state of kernels, which provides reference for formation regularity of rice qualities.【Method】The spikes of “Yueguang” organic rice were sampled at intervals for 63 days after heading (DAH), The 100-grain weight, hardness, moisture content, starch content and protein content were measured, separately, which were used to compare the changes of whole qualities of grains at different growth periods of rice after heading. The transverse relaxation parameters determined by LF-NMR were adopted to qualitatively and quantitatively analyze the moisture dynamics of grains. What’s more, the internal relationships between the formation process of rice qualities and moisture state of grains were discussed.【Result】Both the 100-grain weight and starch content for “Yueguang” organic rice increased most quickly within 7-14 DAH, and they were highly significantly and positively correlated with each other (P＜0.01). Hardness was highly significantly and positively correlated with starch content and protein content, respectively (P＜0.01), and negatively correlated with moisture content (P＜0.01). Within 7-56 DAH, moisture content exponentially declined from 57.16% to 22.39%. With showing an S-shaped growth curve, starch content increased to 50.47 g/100g wet-basis within 42 DAH. Protein content linearly increased to the peak value of 6.56 g/100g wet-basis within 7-49 DAH. On the whole, the whole qualities of rice grains had been formed within 49 DAH. The inversion spectrum of LF-NMR data showed that part of water in the grains moved towards the direction of high mobility within 7 DAH. Within 7-21 DAH, when inversion curves of LF-NMR data gradually moved towards the left, T_2b peak representing for “bound water" with least mobility occurred, followed by the differentiation phenomenon of T₂₂ peak representing for capillary water. Four kinds of transverse relaxation times including T_2b, T₂₁, T₂₂ and T₂₃, gradually decreased with growth periods, which indicated that whole proton degree of freedom in the kernels dropped obviously. The peak ratio of “bound water” was more than peak ratio summation of capillary water and free water at 21 DAH. The moisture content and transverse relaxation parameters (T_2b, T₂₁, T₂₂, T₂₃, A_2b, A₂₂ and A₂₃) of grains varied with growth periods highly significantly (P＜0.01), which were also highly significantly (P＜0.01) related to the accumulation of starch and protein. With endosperm cells filled with starch granules, most of water molecules in the grains were mainly surrounded by starch granules and formed hydrogen bonds with hydrophilic groups of starch, which resulted in the migration of moisture state towards the direction of “bound water”. According to principal component analysis of transverse relaxation signals, there were significant differences among the moisture state of rice grains for different growth periods within 42 DAH, followed by keeping steady.【Conclusion】It was found that during the grain-filling process of rice, the moisture state of grains was significantly related to the accumulation of starch and protein. The ratio of “bound water” gradually increased, and the ratios of capillary water and free water significantly decreased in the grains. LF-NMR can be adopted to effectively analyze the whole moisture dynamic changes of grains at different growth periods of rice after heading.

Effects of Alkaline Stress on Metabonomic Responses of Wheat (Triticum aestivum Linn) Leaves

GUO Rui, ZHOU Ji, YANG Fan, LI Feng

Scientia Agricultura Sinica. 2017, 50(2): 250-259. doi:10.3864/j.issn.0578-1752.2017.02.005

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【Objective】 A pot experiment was conducted to investigate the alkaline stress in ion balance and metabolic profiles of wheat, to determine the physiological adaptive mechanisms of wheat in tolerance to alkali stress. 【Method】 In a pot experiment with control and alkaline stress (NaHCO₃﹕Na₂CO₃=1﹕1), the growth and photosynthetic characters, ion and 73 key metabolites of wheat were studied. 【Result】The results showed that when alkaline stress intensity exceeded the capacity of wheat adjustment, Na⁺ accumulation in cells in a high-pH environment resulted in damage of the photosynthetic system, reduced photosynthetic pigments, inhibited the activity of photosystem II, and reduced high stomatal conductance and net photosynthetic rate. Alkaline stress caused massive influx of Na⁺, a decrease of inorganic negative charge and pH value homeostasis, thus resulting ionic unbalance and leading to a series of strain metabolic response. In addition, 73 metabolites were detected in different alkaline stress treatments according to GC-MS analysis, and these metabolites were sugars/polyols, organic acids, amino acids and others. Compared with the control sample, the response of 25 and 48 metabolites in moderate and severe alkaline stress treatments remarkably changed, respectively, in leaves of wheat seedlings. The results of one-way ANOVA analysis indicated that the changes of metabolites were more significant under high alkaline stress than that under moderate alkaline stress. The results revealed that alkaline stress caused an significant decrease in levels of 5 and 6 metabolites, which are involved in TCA cycle and glycolysis; it also caused amino acids (glutamate, alanine, γ-aminobutyric acid, aspartic acid) and sugars/ploys (fructose, sucrose, talose, myo-inositol) decreased dramatically. Meanwhile, alkaline stress induced organic acids accumulation in wheat, and it maybe a passive adaptive response to alkaline stress, and organic acids kept ionic balance and pH homeostasis. 【Conclusion】 The results suggested that alkaline stress caused systems alterations in metabolic networks including TCA cycle, glycolysis, calvin cycle, shikimic path way, metabolism of plasma membrane,GS/GOGAT cycle and GABA path way, implying alkaline stress not only had side effect on synthesis of sugars, amino acids, fats and proteins, but also inhibited the translation between C and N, thus resulted in nutrients deficiency and caused decrease of plant growth and development.

Effects of Drought Stress on Wheat Endosperm Starch Structure and Physicochemical Properties of Different Varieties

SONG XiaoJun, ZHANG Min, WU XuePing, ZHAO Cheng, SHI Jian, ZHANG YuChun, LIU XiWei, CAI RuiGuo

Scientia Agricultura Sinica. 2017, 50(2): 260-271. doi:10.3864/j.issn.0578-1752.2017.02.006

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【Objective】The objective of this experiment is to study the effects of drought stress on the composition, granule size distribution, pasting properties and crystal properties of wheat endosperm of different varieties, and reveal the intrinsic relationship between the structure and physicochemical properties of wheat starch. 【Method】The wheat cultivars Jingdong8(JD8), Henong825(HN825), Jimai585(JM585) and Nongda211(ND211) were used as the test materials, and irrigated and rainfed treatments were designed in research of the effects of drought stress on wheat endosperm starch structure and physicochemical properties. 【Result】Drought stress significantly inhibited the accumulation of starch in wheat endosperm, but it had no significant effect on the Am/Ap ratio of wheat starch. The granule volume, surface area and number distribution of wheat endosperm showed a bimodal curve. The effect of drought stress on starch grain size distribution of wheat endosperm was different due to the difference of genotype and grain size, in which it had a great influence on the surface area and the number distribution of starch granule size ＜5 μm. Drought stress didn’t change the crystal type of wheat endosperm starch, but significantly increased the crystallinity of starch, and the effects of drought stress on intensity of X-ray diffraction peak were different due to different cultivars and diffraction angles. Drought stress significantly increased trough viscosity and pasting temperature of starch, prolonged the pasting time, while significantly reduced the peak viscosity and breakdown, and there was a genotypic difference in final viscosity and setback. Correlation analysis showed a that the wheat endosperm starch crystallinity showed significant negative correlation with total starch and Am content, and a significant positive correlation with Ap content. The total starch content showed a significant positive correlation with peak viscosity. The Am content showed a significant positive correlation with peak viscosity and breakdown, and a negative correlation with the pasting temperature. The correlation between the Ap content and pasting parameters was not significant, while the Am/Ap ratio of wheat starch showed a significant negative correlation with the pasting time. The volume of ＜5 μm and ＜10 μm starch granule, respectively, showed a significant and an extreme significant negative correlation with final viscosity and setback, but the starch granule with diameter ＞15 μm was positively correlated with final viscosity and setback. The correlation between granule volume distribution and crystallinity of wheat was not significant. Wheat starch peak viscosity and breakdown, respectively, showed an extremely significant and significant negative correlation with crystallinity, but there was a significant positive correlation between the pasting temperature and crystallinity. 【Conclusion】Drought stress changed the wheat endosperm starch composition, granule size distribution, crystallinity and pasting parameters. There were significant correlations between wheat endosperm starch structure and physicochemical properties, indicating that the effects of drought stress on the structure of wheat starch, indirectly affected the physicochemical properties, therefore, the cultivation conditions could be adjusted to achieve the purpose of quality wheat production.

Analysis of Wheat Leaf Rust Resistance Genes in 30 Important Wheat Cultivars

YAN XiaoCui, LI ZaiFeng, YANG HuaLi, ZHANG HuanHuan, GEBREWAHID Takele Weldu, YAO ZhanJun, LIU DaQun, ZHOU Yue

Scientia Agricultura Sinica. 2017, 50(2): 272-285. doi:10.3864/j.issn.0578-1752.2017.02.007

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【Objective】Leaf rust is an important wheat disease and it has a great influence on wheat yield. Breeding durable resistant cultivars can economically and effectively control the disease. The objective of this study is to identify leaf rust resistance genes in 30 wheat cultivars from China by gene postulation, molecular marker-assisted selection, adult plant resistance identification and pedigree analysis.【Method】The cultivars were tested for seedling responses in the greenhouse to 18 Puccinia triticina pathotypes (PHGQ, THJT, PHJT, KHJS, PHJS, THTT?, KHHT, FHRT, FHJQ, PHTT, THTT?, PHTT, FHTR, FHHT?, FHHT?, TGGT, FHTT, FGMT) and to a mixed pathotypes (FHRT, THTT, THJT) for slow leaf rusting resistance in the field in 2014-2015 and 2015-2016 cropping seasons in Zhoukou, Henan Province and Baoding, Hebei Province. CIMMYT line SAAR, with typical slow rusting resistance and Zhengzhou 5389, a highly susceptible line were used as slow rusting and susceptible checks, respectively. Differential sets containing 36 near-isogenic lines (NILs) in a background of Thatcher with known leaf rust resistance genes were used to compare the infection types of the cultivars at seedling stage. The software IBM SPSS Statistics 19.0 was used for analysis of variance (ANOVA) and for determining least standard deviations (LSDs) for comparing the FDS (the final diseases severity) among the wheat cultivars. Cultivars which were susceptible to the mixed pathotypes and had lower or non-significantly higher values of FDS than those of the slow rusting check in field trials were considered to be slow rusting cultivars.【Result】Gene postulation combined with pedigree analysis, and markers detection results showed that four cultivars, viz. Een 5, Emai 14, Shaan 229, and Xinong 979 contained Lr1; 10 cultivars (Een 1, Een 5, Een 6, Guinong 16, Shaan 225, Shaan 354, Shaan 715, Shaanhe 6, Shaanmai 509 and Shaannong 7859) carried Lr26, two cultivars (Shaan 225 and Xiaoyan 81) contained slow rust resistance gene Lr46 by molecular marker detection; three varieties (Xinong 979, Shaan 229, and Guinong 16) might contain Lr13. All cultivars didn’t carry resistance genes, viz. Lr9, Lr10, Lr19, Lr20, Lr24, and Lr34. Based on the leaf rust resistance phenotype data in the field through four environments, a total of 18 cultivars showed slow rusting resistance. The variance analysis results showed that the genotypes-years interactions and the genotypes-locations were highly significant differences but genotypes-replicates interaction was not significant. At the same time, highly significant differences were found for wheat genotypes and environment (seasons and locations) for FDS in the field trials, but its effect on variation was much less than the genotypic differences. Therefore, these suggested that the expression of wheat leaf rust resistance was mainly influenced by genotypes and environments.【Conclusion】Four resistance genes, viz. Lr1, Lr26, Lr13, and Lr46 were found in 14 wheat cultivars among 30 released winter wheat cultivars in China, but known leaf resistance genes could not be detected in other 16 cultivars. A total of 18 cultivars might carry slow rust resistance genes according to the field resistance data. All slow rusting materials may contain unknown plant leaf rust resistance genes, which need further genetic identification.

The Influence of Redroot Pigweed (Amaranthus retroflexus) Density on Cotton (Gossypium hirsutum)

LI ShuYing, ZHU JiaBao, LU XianYong, YE SiHong, MA Yan, MA XiaoYan, CHENG FuRu

Scientia Agricultura Sinica. 2017, 50(2): 286-298. doi:10.3864/j.issn.0578-1752.2017.02.008

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【Objective】Amaranthus retroflexus is one of the worst agricultural weeds in the world, and it is a major weed in cotton belt along Changjiang River in Anhui Province. Cotton is very sensitive to the competition of weeds. The objective of this study is to clarify the interference impact of A. retroflexus in cotton field, and to provide useful information for weed control programs. 【Method】Field additive series experiments were conducted to evaluate the influence of 8 A. retroflexus densities on growth, yields and yield components, fiber properties of cotton with full-season interference of A. retroflexus during 2013-2015 in Anqing test plot of Anhui Province, with cotton density no changing. The weed densities employed were 0 (the check), 0.125, 0.25, 0.5, 1, 2, 4 and 8 plants/m of row. 【Result】With the increase of weed density, plant height and stem diameter of A. retroflexus gradually decreased, and the plant stem diameter reduced obviously by 12.0%-18.6% at the density of 1 plant/m of row (2013 and 2014) and 0.5 plant/m of row (2015) than that at the density of 0.125 plant/m of row, respectively. The plant height reduced significantly by 24.2% at the density of 0.5 plant/m of row than that at the density of 0.125 plant/m only in 2015. The per unit area biomass of A. retroflexus increased from 1 156.9 kg·hm^-2 at density of 0.125 plant/m of row to 7 524.0 kg·hm^-2 at the density of 8 plants/m of row over the average of three years. Intraspecific competition among A. retroflexus plants was observed at the higher weed densities. With the increasing interference between A. retroflexus and cotton, A. retroflexus remained taller and thicker than cotton after 52-83 DAE and 18-70 DAE, respectively. At the maturity stage of cotton, the plant stem height of A. retroflexus was 35.6-128.2 cm higher than that of cotton, and the plant stem diameter of A. retroflexus was 9.9-24.8 mm thicker than that of cotton. A. retroflexus had more obvious advantages than cotton in plant height and biomass. The interference of A. retroflexus density had no significant influence on cotton height, but cotton stem diameter reduced obviously at higher weed densities. With the increasing of weed density, per plant bolls, fruit-branch numbers, single boll weight of cotton reduced significantly; and lint percentage of cotton also decreased to some extent. Bolls, fruit-branch number per plant and single boll weight reduced by 20.81%-84.98%, 4.63%-69.18% and 3.04%-20.36% at the density of 1 plant/m of row, respectively; and lint percentage reduced by about 1.54% at this density. The interference of A. retroflexus affected significantly on seed cotton yield at the density of 0.125 plant/m of row (2013) and 0.25 plant/m of row (2014 and 2015), respectively, and the seed cotton yield reduced by 14.0%-33.7% at these densities. The relationship between cotton yield loss rate and the density of A. retroflexus was described by the hyperbolic regression model, which estimated that a density of 0.2-2.8 weed plant/m of row would result in 50% seed cotton yield loss from the maximum yield. Boll and fruit-branch numbers per plant of cotton were reduced obviously at the density of 0.125-0.5 plant/m of row of A. retroflexus after 91 DAE. In some year, the fiber length, Micronaire and fiber strength of cotton fiber significantly decreased with increase of weedy densities.【Conclusion】 The full-season interference of A. retroflexus had no significant influences on plant height, and obvious impacts on plant stem diameter of cotton and A. retroflexus in cotton belt along Changjiang River in Anhui Province. With the increase of interference time between A. retroflexus and cotton, A. retroflexus surpassed cotton in plant height and stem diameter. It was concluded that A. retroflexus had competitive advantages over cotton in plant height and biomass and A. retroflexus should be controlled at its seedling stage critically. Intraspecific competition among A. retroflexus plants was enhanced with increasing weedy density. The biomass of A. retroflexus is easily affected by environmental conditions. The per unit area biomass of A. retroflexus increased with increase of weed density, and the impact on cotton development and yields were enhanced obviously. The cotton yields were reduced by the interference of A. retroflexus through decreasing boll numbers per plant and single boll weight of cotton. It was inferred that a density of 0.011-0.090 plant/m of row of A. retroflexus would result in a 5% seed cotton yield loss from the maximum yield.

Effect of Precipitation Patterns and Different Phosphorus Nutrition Levels on Winter Wheat Yield

HU YuTong, HAO MingDe, FU Wei, ZHAO Jing, WANG Zhe

Scientia Agricultura Sinica. 2017, 50(2): 299-309. doi:10.3864/j.issn.0578-1752.2017.02.009

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【Objective】Water and fertilisation are the main two factors limiting wheat production in arid and semiarid regions of the Loess Plateau. The effects of precipitation patterns and phosphorus nutrition levels on wheat yield under long-term fertilizer field experiment were studied. The result will provide a theoretical basis for improving wheat yield with a reasonable phosphorus level with different precipitation patterns in the semiarid regions.【Method】Growth years precipitation were divided into dry years, normal years and wet years based on 30 years long-term fertilizer field experiment on the semiarid Loess Plateau in China. Effects of precipitation patterns and phosphorus nutrition levels on the winter wheat yield, yield component and phosphorus contribution rate (PCR) were deeply studied on the semiarid Loess Plateau.【Result】Wheat yield, 1000-grain weight, grains per spike and spike numbers in the dry years were lower than the normal years, higher in the wet years than the normal years. pCR in the dry years was higher than the normal years, lower in the wet years than the normal years. Wheat yield, 1000-grain weight and grains per spike in the dry, normal, wet and 30 years planting showed a trend of increase first and fall later with the adding of phosphorus. Spike numbers were increased first and fall later in the dry years, presented a rise perpendicularly in the normal years, wet years and 30 years planting. PCR was increased first and fall later in the dry years, presented a rise perpendicularly in the normal years, linear decrease in the wet years. The correlation coefficient between the yield and yield components showed that different precipitation patterns mainly through affecting the spike numbers to influence the yield. The partial regression coefficient among spike numbers and dry, normal, wet years and 30 years planting was 0.713, 0.294, 0.692 and 0.643, respectively.【Conclusion】Phosphorus nutrition levels and precipitation patterns could significantly impact the wheat yield. The yield in the 125-137 kg·hm^-2 phosphorus treatment was the best in different precipitation patterns. The yield in the 131 kg·hm^-2 phosphorus treatment was the best with the 30 years continuous planting. Precipitation patterns and phosphorus nutrition levels mainly through regulating the spike numbers of wheat yield components to influence the yields.

Effect of Residual Plastic Film on Soil Nutrient Contents and Microbial Characteristics in the Farmland

ZHANG Dan, LIU HongBin, MA ZhongMing, TANG WenXue, WEI Tao, YANG HuDe, LI JunGai, WANG HongYuan

Scientia Agricultura Sinica. 2017, 50(2): 310-319. doi:10.3864/j.issn.0578-1752.2017.02.010

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【Objective】 The purpose of this study was to explore the effect of residual plastic film on soil fertility and soil microbial characteristics, clarify the risk threshold of residual plastic film in the field and promote effective control and management of residual plastic film pollution in China.【Method】Five residual plastic film gradients were designed in representative farmlands in Zhangye county of Gansu province from 2011 to 2015, including 0 (CK), 150 kg·hm^-2 (T1), 300 kg·hm^-2 (T2), 450 kg·hm^-2 (T3) and 600 kg·hm^-2 (T4). After crop harvesting in 2015, soil physical and chemical properties, microbial biomass carbon and nitrogen, enzyme activity and microbial abundance were monitored.【Result】The amount of residual plastic film had a great effect on soil water content, organic matter (SOM), total nitrogen (TN), ammonium (NH₄⁺-N), nitrate nitrogen(NO₃^--N) and available phosphorus (Olsen-P), in which the soil water content was significantly increased with increasing residual plastic film in field, however the SOM, TN, NO₃^--N and Olsen-P were declined, the NH₄⁺-N was increased and then decreased with the increase of residual plastic film. In the lower residual plastic film treatment, the soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were improved because of soil water content increased compared with CK, however, they were significantly reduced in the high residual plastic film treatments (T3 and T4) (P<0.05). In addition, the soil microbial community abundance (AWCD, richness, Shannon, Simpson and McIntosh) of CK and T1 were significantly higher than that of T3 and T4 (P<0.05). The variation trend between soil enzyme activity and residual plastic film was similar to MBC and MBN, and the activities of α-1,4-glucosidase (AG), β-1,4-glucosidase (BG), Cellobiohydrolase (CBH), β-1,4-xylosidase (BXYL) and β-1,4-N-acetyl-glucosaminidase (NAG) were high in the treatments of 300-450 kg·hm^-2of residual plastic film, however, they were significantly decreased when the residual in the treatment with plastic film at 600 kg·hm^-2.【Conclusion】In the treatment with lower residual plastic film, the soil microbial activity was improved though increasing soil water content, whereas the soil microbial biomass carbon, microbial biomass nitrogen, microbial community abundance and soil enzyme activity were significantly decreased if the residual plastic film higher than 450 kg·hm^-2. Moreover, the soil organic matter, total nitrogen, ammonium nitrogen, nitrate nitrogen and Olsen-P all reduced with long-term effect of high residual plastic film, and caused soil fertility degradation. It was concluded that management of the residual plastic film should be strengthened in order to reduce the risk of soil degradation, especially in the regions with serious residual plastic film pollution.

Genetic and Phylogenetic Relationships Among Citrus and Its Close and Distant Relatives Based on COS Marker

WANG Jiong, GONG GuiZhi, PENG ZhuChun, LI YiBing, WANG YanJie, HONG QiBin

Scientia Agricultura Sinica. 2017, 50(2): 320-331. doi:10.3864/j.issn.0578-1752.2017.02.011

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【Objective】To reveal genetic diversity and phylogenetic relationships of Citrus and its close and distant relatives with newly developed conserved ortholog sequence (COS) Marker.【Method】According to the published C. sinensis and C. clementina genomic sequencing information, COS Markers were developed and screened. Polymorphic markers were used to amplify and detect Citrus and its close and distant relatives. Structure, Power Marker and GenAlEx were used to analyze the relevant data.【Result】A total of 60 COS primers were designed, and 25 primer pairs distributed in different linkage groups were selected based on clear and good DNA polymorphic bands. In 45 samples from Citrus and its relatives, 25 COS markers produced 584 bands, with an average of about 23.36 bands per marker, and genetic diversity ranged from 0.26 to 0.88, with an average of 0.49; PIC value was between 0.26 and 0.87, with an average of 0.48. When K = 9, a clear genetic structure relationship of citrus and its relatives were revealed. They were divided into C. reticulata group, C. grandis group, C. medica group, Papeda group, Fortunella group, P. trifoliate and Eremocitrus and M. australis group, Z. bungeanum group, Clausena lansium and Atalantia buxifolia and Murraya paniculata group as well as C. indica and C. mangshanensis hybrid groups. This result was globally consistent with that in the UPGMA clustering analysis. UPGMA clustering analysis revealed that COS Marker could effectively distinguish Citrus from its close and distant germplasm resources. At higher taxonomy level, Citrus was first separated from P. trifoliate, Eremocitrus, M. australis, Z. bungeanum, Clausena lansium, Atalantia buxifolia and Murraya paniculata; In Citrus, C. medica and Papeda group were first clustered, and then they were clustered with C. reticulata and C. grandis and other plants of Citrus. In C. reticulata group, Daoxian yeju and Cenxi suanju and other half wild C. reticulata were clearly distinguished from ponkan and the rest cultivated C. reticulata, but C. mangshanensis and C. indica were not in the group.【Conclusion】COS primers based on Citrus genomic information could get effective amplification and distinguish Citrus from its close and distant relatives effectively. The genetic makeup of C. mangshanensis and C. indica were heterozygous and different from C. reticulata, so they may not be the most primitive types of C. reticulata.

Progress in Research of Detection, Risk Assessment and Control of the Mycotoxins in Fruits and Fruit Products

LI ZhiXia, NIE JiYun, YAN Zhen, ZHANG XiaoNan, GUAN DiKai, SHEN YouMing, CHENG Yang

Scientia Agricultura Sinica. 2017, 50(2): 332-347. doi:10.3864/j.issn.0578-1752.2017.02.012

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Fungi are major pathogens to fruit spoilage in the production, storage and transportation, and also are responsible for significant financial losses. In addition to their ability to cause fruit spoilage, some fungi may produce mycotoxins with potential harm to human health. Mycotoxins are a diverse group of toxic secondary metabolites produced by filamentous fungi under appropriate conditions. Followed by pesticide and heavy metal, the mycotoxins are considered as another important risk factor which can directly affect the quality and safety of fruits and fruit products. Numerous studies show that the mycotoxins can cause DNA damage and are harmful to human and animal health even at low concentrations. They caused liver, kidneys and gastrointestinal tract lesions or may be carcinogenic, teratogenic and mutagenic. Therefore, it is important to investigate the occurrence, accurate detection, risk assessment and control technology of mycotoxins in fruit and fruit products. The most common mycotoxins associated with fruits are patulin (PAT), aflatoxins (AF), alternaria toxins and ochratoxin A (OTA) which are respectively classified into 3, 1, 2B and 2B carcinogen by the International Agency for Research on Cancer (IARC). Usually, equipments with high standard configurations are needed for mycotoxin detection due to the extremely low concentrations in fruits and their products. Currently the main detection methods for mycotoxins include thin-layer chromatography, high performance liquid chromatography and mass spectrometry, gas chromatography and mass spectrometry, capillary electrophoresis technology, and so on. However, because of the different chemical structure and properties of special mycotoxin, it is incapable to use a standard method for the simultaneous quantitative determination of all mycotoxins. Therefore, it is a research hotspot to screen accurate, efficient and rapid detection methods for mycotoxins. To date, a total of 80 countries and regions have set the mycotoxin limits in fruits and fruit products to protect the health of consumers. It is to be regretted that there were no regulations for Alternaria toxins yet. Risk assessment results based on toxicological data in many countries were shown that dietary intakes of the mycotoxins from fruits and their products were very low in most cases and may not threaten the human health. Although the mycotoxins in fruits and their products could be prevented and degraded by chemical, physical or biological methods, there has not been an effective technology to complete detoxification in infected products. Hence, it is crucial to prevent mycotoxin production in fruits rather than remove. This review summarized the main mycotoxin types, occurrence, toxicities, detection methods, limit standards, risk assessments and control technologies in fruit and fruit products. And finally, the future research directions of fruit mycotoxins were prospected in order to provide a reference for researchers in this field.

Volatile Components of Main Indica Rice Cultivars from Hunan Province

SONG Wei, HU WanJun, XU ZongJi, LIU Bing, FAN Yan, NI Yang, YANG HuiPing

Scientia Agricultura Sinica. 2017, 50(2): 348-361. doi:10.3864/j.issn.0578-1752.2017.02.013

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【Objective】The volatile components of different indica rice varieties from Hunan province were investigated and compared to explore the possibility that using volatile compounds as indicators for characterization and differentiation of varieties, also for providing a reference for rice storage, processing and quality control.【Method】The head space-solid phase microextraction method was used to extract the volatile components from twelve varieties of indica rice and the extracted volatile substances were analyzed by gas chromatography-mass spectrometry method. The principal component analysis was adopted to analyze their flavors.【Result】A total of 265 volatile components were detected, 125 kinds of substances were screened according to the quality of not less than 80, including 56 kinds of hydrocarbons, 12 kinds of alcohols, 13 kinds of aldehydes, 14 kinds of ketones, 19 kinds of eaters, and 11 kinds of heterocylic compounds. The average percentage contribution of alkanes, olefin, aromatic hydrocarbons, alcohols, aldehydes, ketones, eaters and heterocylic compounds to the total were 26.907%, 8.417%, 7.308%, 5.810%, 9.628%, 18.626%, 13.926% and 6.819%, respectively. The coefficient of variation was 19.98%, 38.22%, 34.67%, 41.12%, 28.57%, 38.81%, 20.13% and 34.33%, respectively. High levels of 6, 10, 14-trimethyl-2-pentadecanone were detected in all species. Some varieties have unique substances, and Kauri-15-ene only existed in Zhuliangyou 819 and Zaoyou, Tezao has a special bisabolene. Isophytol, tetrahydrofurfuryl lavender alcohol and citronellol existed only in Zhuliangyou819, Tezao and Zaoyou respectively. Only Zaoxian87 contained high levels of dihydroxyacetophenone. Benzoicacid ester of silicon occurred only in Zaoyou, chloroformate n-nonyl ester was only detected in Zhongzao 39, and chloroformate n-octyl phthalate was detected only in Zhuliangyou 819 and Zaoxain 51-4. The results of principal component analysis showed that olefin, alkanes, aldehydes and heterocylic substances were the main influencing factors. The contribution rate was 35.878%, 19.267%, 18.727% and 13.596%, respectively, and the cumulative contribution rate was 87.467%. Samples (Xiangai45, Xiangzao32, Zaoxian87, Zaoxian89, Zaoxian51-4, Zhuliangyou 819, Tezao, Zhongzao39, Zaoyou) were distinguished except Zhuliangyou402, Tanliangyou83 and Zaoxian24 according to olefin. Zaoxian 87, Zaoxian89 and Zaoxian51-4 could be identified by alkanes. Zhuliangyou 819 and Zaoixan 51-4 were distinguished through aldehydes. Zaoxian 51-4 and Zaoxian 24 were identified in accordance with heterocyclic substance.【Conclusion】There are significant differences in volatile compositions and concentrations among 12 varieties of indica rice. Principal component analysis can identify specific substances and distinct paddy varieties.

Effects of Different Drying Methods on the Nutrition and Physical Properties of Momordica charantia

DENG YuanYuan, TANG Qin, ZHANG RuiFen, ZHANG Yan, WEI ZhenCheng, LIU Lei, MA YongXuan, ZHANG MingWei

Scientia Agricultura Sinica. 2017, 50(2): 362-371. doi:10.3864/j.issn.0578-1752.2017.02.014

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【Objective】The objective of this study is to provide a theoretical basis for choose the optimal industrial production mode of drying process of Momordica charantiaL.by studying the effect of different drying methods on nutrition, antioxidant and physical properties. 【Method】Nutrition components (polysaccharide, Vc, total phenolics, total flavonoid, carotenoid ), oxygen radical absorbance capacity (ORAC), sensory evaluation (color and hardness) and microstructure were taken as evaluation indices. Vacuum freeze drying (VFD), sun drying (SD), heat pump drying (HPD), heat air drying (HAD), microwave drying (MD) and vacuum heat drying (VHD) were adopted to dry M. charantia, and then the effects of six drying methods on texture quality and related physicochemical indices during processing were studied. 【Result】For effects of different drying methods on nutritional ingredient and antioxidant, except for VFD, M. charantia processed by other methods had the same extract ratio of polysaccharide. M. charantia dried by HPD had the highest contents of polysaccharide of 29.22 mg·g^-1 DW, while MD presented the lowest contents of 16.91 mg·g^-1 DW. The contents of Vc, total phenolics, flavonoid, carotenoid and ORAC of different drying methods on M. charantia were reduced after processing. M. charantia dried by HPD had the highest contents of Vc (84.81 mg·100 g^-1), while MD contained the lowest (6.64 mg·100 g^-1). HAD had the highest contents of total phenolic and total flavonoid (32.04 mg GAE·g^-1 and 7.44 mg CE·g^-1, respectively), while VFD contained the lowest (14.14 mg GAE·g^-1 and 0.36 mg CE·g^-1, respectively). HPD had the highest contents of carotenoid (0.86 mg·g^-1 DW), while SD contained the lowest (0.11 mg·g^-1 DW). The highest ORAC was obtained from HPD, MD and VHD (226.44, 224.66 and 244.10 μmol TE·g^-1, respectively), while the lowest was 113.23μmol TE·g^-1, which observed in VFD. As forsense and physical properties, browning degree caused by thermal processing, but VFD presented the lowest browning degree. M. charantia dried by HPD had the highest contents of chlorophyll-a and chlorophyll-b, while SD contained the lowest. SD had the highest hardness, while VFD presented the lowest. As for microstructure, HAD, HPD and SD caused more shrinkage, and MD caused damage to structure, while VFD and VHD effectively retained the myosin integrity of M. charantia slices. 【Conclusion】The results indicated that there were significant differences in nutrition and physical properties of M. charantia among different drying methods. The best nutrition and antioxidant activity were found in HPD and HAD. The bright color and good texture profile were found inVFD. M. charantia dried by SD and MD had the poor quality.

Relaxed Effect of Caulis Lonicerae Extraction on Contraction of Intestinal Smooth Muscle of Rabbit in Vitro and Its Mechanism

WANG Hui, ZHANG HaiJuan, LI ZhiDong

Scientia Agricultura Sinica. 2017, 50(2): 372-379. doi:10.3864/j.issn.0578-1752.2017.02.015

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【Objective】Excessive gastrointestinal smooth muscle contraction cause abdominal pain and diarrhea diseases in clinical. Recently, Ca²⁺ channel blocker nifedipine and anticholinergic atropine are widely employed in the treatment of gastrointestinal excessive contraction. However, nifedipine has a potent negative inotropic and dromotropic effects with dose increase after long-term administration, and atropine has severe side-effects which highly limited its clinical utilization. Therefore, it is important to develop natural medicines with high activity, low toxicity and no residue. In this research, the effects of Caulis lonicerae extraction on spontaneous smooth muscle contractions in isolated rabbit small intestine were investigated and the possible mechanism was explored.【Method】The in vitro intestine movement experiment, was conducted and the BL-420E biologic function analysis system was employed. The influences of C. lonicerae extraction on spontaneous contractions of the rabbit intestinal smooth muscle were measured. The effects of C. lonicerae extraction on spasmodic muscle contractions were measured by using acetylcholine (ACh), histamine (HA) and BaCl₂. The mechanism of C. lonicerae extraction was studied by using inositol 1,4,5-trisphosphate (IP₃) receptor antagonist (heparin, HP), ryanodine receptor antagonist (ruthenium red, RR) and a nitric oxide synthase (NOS) inhibitor (Nitro-L-arginine methyl ester, L-NAME).【Result】The results showed that the extraction of Caulis lonicerae extraction dose-dependently inhibited the spontaneous contraction of intestinal smooth muscle. Caulis lonicerae extraction, at the concentration of 7.5 g·L^-1, showed highly inhibition effects on the frequency of spontaneous contractions (P< 0.05). Meanwhile, at the concentration of 5 g·L^-1, significantly inhibition effects on the amplitude of spontaneous contractions (P < 0.05) were detected. ACh, HA and BaCl₂ significantly induced the amplitude of smooth muscle contractions, and C. lonicerae extraction notably inhibited the muscle contractions induced by ACh, HA and BaCl₂ (P < 0.05 or P < 0.01). IP₃ receptor antagonist heparin could strengthen the relaxed effects of C. lonicerae extraction on intestinal smooth muscle, but ryanodine receptor antagonist ruthenium red had no effect on the relaxation of C. lonicerae extraction. L-NAME inhibited the relaxation of C. lonicerae extraction (P < 0.01).【Conclusion】The extraction of C. lonicerae inhibited the frequency and amplitude of intestinal smooth muscle contractions of rabbits in vitro. The mechanism may be related to the increase of NO concentration in intestinal smooth muscle, and the inhibiting intracellular Ca²⁺ released via IP₃ of sarcoplasmic reticulum.

Regulatory Role of Noncoding RNAs During Spermatogenesis

CHEN Rui, YU Shuai, CHEN XiaoXu, DU Jian, ZHU ZhenDong, PAN ChuanYing, ZENG WenXian

Scientia Agricultura Sinica. 2017, 50(2): 380-390. doi:10.3864/j.issn.0578-1752.2017.02.016

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Spermatogenesis starts with spermatogonial stem cells (SSCs), which possess the ability of self-renewal and differentiation. SSCs are capable of differentiation to form Asingle (As) spermatogonia, Apaired (Apr) spermatogonia, Aaligned (Aal) spermatogonia, A1-A4 spermatogonia, intermediate spermatogonia, and B spermatogonia. Type B spermatogonia divide forming the primary spermatocytes, which undergo a long meiosis time to form secondary spermatocytes. Then secondary spermatocytes go through meiosis II to produce round spermatids, which will undergo a series of processes called spermiogenesis containing morphological changes, replacement histone by protamine, nuclear condensation and formation of flagellum. Finally, the mature spermatozoa are released into the lumen. This process requires precise and highly ordered regulation of gene expression at both the transcriptional and posttranscriptional levels. Recent advances in research have revealed that several types of noncoding RNAs (ncRNAs), including microRNAs (miRNAs), Piwi-interacting RNAs (piRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs) and endogenous small-interfering RNAs (endo-siRNAs), are essential for spermatogenesis. These ncRNAs are expressed in a cell-specific and step-specific manner to participate in the control of spermatogenesis. MiRNAs are a class of endogenous non coding single stranded RNA molecules of about 21-25 nt that widely exist in various kinds of organisms, its formation needs at least two RNA enzymes such as Drosha and Dicer, which can also degrade target mRNA or inhibit target mRNA translation, have an important regulatory role in maintaining the stemness, self-renewal of SSCs, regulating differentiation, and involved germ cell meiosis and spermatogenesis. piRNAs are a large class of small RNAs that are 24-32 nt in length found in 2006, which could execute the biological function through interactions with Piwi proteins without Dicer enzyme, also silence transposons and retroposons at the epigenetic and posttranscriptional levels, maintain the genomic stability and integrity of germ cell, regulate cell proliferation, meiosis and spermatogenesis. LncRNAs are one of ncRNAs longer than 200 nt, their production process and structure are similar to the mRNA. Different sources of lncRNAs could regulate the stemness, differentiation of SSCs, and modulate germ cell apoptosis in a transcriptional and posttranscriptional manner. Some lncRNAs could also regulate the expression of miRNAs thus regulate the process of spermatogenesis. CircRNAs, differs from the traditional linear RNA, is a new type of RNA, which is conserved in different species, and specifically expressed in different tissues and developmental stages. Its formation processing mode is related to its sequence, the same gene locus could produce a variety of circRNAs through selective cyclization. Studies indicated that circRNAs can be combined with miRNAs to regulate spermatogenesis. Compared with other ncRNAs, the biogenesis of endo-siRNAs is simple, and has the same effect as miRNAs, which plays an important role in spermatogenesis and male reproduction. Therefore, this review summarized the regulatory role of ncRNAs during spermatogenesis, which provided insight into the further research on ncRNAs during spermatogenesis.

Effect of Water Stress on Development and H₂O and CO₂ Exchange in Leaves of Tomato Grafted with Different Drought Resistant Rootstocks

ZHANG ZhiHuan, HAN Min, ZHANG Yi, WANG Yun, LIU CanYu, CAO BiLi, XU Kun

Scientia Agricultura Sinica. 2017, 50(2): 391-398. doi:10.3864/j.issn.0578-1752.2017.02.017

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【Objective】The threat of drought is a main meteorological factor of agricultural production and rational use of the crops of drought resistant germplasm resources is an important element of biological water saving. This paper aims to study the effect of water stress on the growth and development, water potential and gas exchange parameters of tomato leaves grafted with 2 different drought resistance rootstocks and to investigate the feasibility of biological water saving of tomato via grafting on drought resistant rootstocks.【Method】The experimental was designed by the split plot, the main plot was a grafting treatment composed of the ungrafted tomato of ‘Jinpeng 1’(J), the grafted tomato of ‘606’ (J/T) with drought-tolerant rootstock and‘112’ (J/S) with drought-sensitive rootstock, and the subplot was a soil moisture treatment composed of 80%, 60% and 40% soil relative water content. Pot weighing method was adopted to control soil moisture of tomato. At the flourishing period of tomato plant, the expand functional leaves pigment, water potential and water-gas exchange parameters were determined and the instantaneous water use efficiency was calculated, simultaneously, the yield and fruit quality of tomato in different treatments were analyzed.【Result】The results showed that the yield of grafted tomato was significantly higher than the ungrafted tomato and the yields of J/T and J/S were 17.50% and 11.00% higher than J. Simultaneously, the vertical diameter, transverse diameter, firmness, content of vitamin C and lycopene of tomato fruit of J/T were significantly higher than J and J/S. The content of tomato leave pigments, photosynthetic rate, leaf water potential, transpiration rate and water use efficiency of J/T and J/S with different drought resistance were also significantly higher than J, and at 13:00 the water use efficiency of grafted treatment J/T and J/S were higher than ungrafted J by 15.16% and 7.52%, J/T was also significantly higher than J/S. The yield of tomato showed a significant difference under different soil moisture contents which showed an order of 80%＞60%＞40%, while the fruit quality indicators such as soluble solid, soluble protein, vitamin C and lycopene are contrary to the yield. With drought stress increased, the yield increase of grafted tomatoes was even more obvious. And J/T outperformed J/S, and the yield was 7.47%, 4.71% higher than ungrafted J, respectively, under the condition of the soil relative water content of 80%, and under the condition of 40% of water content, the yield increase rate was up to 38.04% and 22.35%. The contents of tomato leave pigments, photosynthetic rate, leaf water potential and transpiration rate were decreased as the water stress increased. The water use efficiency in 60% soil moisture treatment was higher than that in 40% and 80% soil moisture treatments. 【Conclusion】 Results of the experiment demonstrated that when tomato grafted with drought-tolerant rootstock ‘606’, its fruit yield was higher, fruit quality was better and the photosynthetic rate and water use efficiency were also higher, and especially prominent under water stress conditions. It was concluded that the possible way to realize biological water saving to a certain extent for tomato is grafting with drought-tolerant rootstock.

Spatial-Temporal Distribution of Double Cropping Rice’s Yield Gap in Hunan Province

GUO ErJing, YANG XiaoGuang, WANG XiaoYu, ZHANG TianYi, HUANG WanHua, LIU ZiQi, TAO Li

Scientia Agricultura Sinica. 2017, 50(2): 399-412. doi:10.3864/j.issn.0578-1752.2017.02.018

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【Objective】 Hunan is one of the main regions of double cropping rice in China, and the total rice yield was the highest in the country in 2014. This study characterized the spatial and temporal variations of the potential and reported statistical yields as well as their gaps of the early and late rice in the double cropping rice areas of Hunan province. 【Method】The historical weather (1981-2010), soil, crop growth and statistical yield data of Hunan province were collected and used to parameterize the rice model ORYZA v3 through the standardized calibration and validation processes. The performance of the model with parameters of rice cultivars was evaluated with satisfied decision coefficient (R²), D-index, root mean square error (RMSE), normalized root mean square error (NRMSE), mean absolute error (MAE) between simulated and observed values. The verified model was used to compute the potential yields in each area in the period from 1981 to 2010, and then the temporal and spatial variations of the potential yields and their gaps (in both absolute and relative value) to actual yields were characterized by using ArcGIS. 【Result】The ORYZA v3 estimations highly agree with observations in the rice development phenology and yields for both of the early and late rice in Hunan province. The verified model could be used in the study of rice potential yields in Hunan province. The spatial distribution of potential yields of early and late rice were both higher in north area than in the south area. High potential yields appeared in Wugang and Shaoyang while low-yielding area was located in hilly south area. Within the study area, the inter-year variation of the potential yields of double cropping rice was slightly higher in the eastern region than that in the western region while the stability of the early rice was higher than that of the late rice. The potential yield of double cropping rice in Hunan province presented a decreasing tendency from north to south and also from 1981 to 2010, especially more significant for the late rice. The biggest yield gap of the double cropping rice appeared in the north areas and the actual yield could be increased furthermore. The yield gaps were smaller in the south area than the north, and they were relatively larger in the late rice than in the early rice, indicating that late rice yield could be improved more in this area. During the period from 1981 to 2010, the yield gaps of double cropping rice in Hunan province decreased gradually. The reduction was more obvious in the late rice than that in the early rice.【Conclusion】The potential yields of double-cropping rice decreased as the average temperature increased under the background of climate change. Meanwhile, the actual production increased continuously due to varieties improvement, technology optimization and increase of inputs. Thus yield gaps between early rice and late rice both decreased during the study period excepted a few stations like Daoxian and Yuanjiang. The yield gaps of the early rice were generally higher than those of late rice with the lower reduction rates over the period from 1981 to 2010. The positive effect of increasing sunshine hours in the growing season of early rice could partially compensate the negative effect of temperature rise. Additionally, the yield gaps of the early rice presented an increasing trend in more areas than those in the late rice. Generally, the actual yield of early rice has a larger gap to close in the future in the double cropping rice area of Hunan province.

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