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Mapping winter rapeseed in South China using Sentinel-2 data based on a novel separability index

TAO Jian-bin, ZHANG Xin-yue, WU Qi-fan, WANG Yun

2023, 22 (6): 1645-1657. DOI: 10.1016/j.jia.2022.10.008

Abstract （230） PDF in ScienceDirect

Large-scale crop mapping using remote sensing data is of great significance for agricultural production, food security and the sustainable development of human societies. Winter rapeseed is an important oil crop in China that is mainly distributed in the Yangtze River Valley. Traditional winter rapeseed mapping practices are insufficient since they only use the spectral characteristics during the critical phenological period of winter rapeseed, which are usually limited to a small region and cannot meet the needs of large-scale applications. In this study, a novel phenology-based winter rapeseed index (PWRI) was proposed to map winter rapeseed in the Yangtze River Valley. PWRI expands the date window for distinguishing winter rapeseed and winter wheat, and it has good separability throughout the flowering period of winter rapeseed. PWRI also improves the separability of winter rapeseed and winter wheat, which traditionally have been two easily confused winter crops. A PWRI-based method was applied to the Middle Reaches of the Yangtze River Valley to map winter rapeseed on the Google Earth Engine platform. Time series composited Sentinel-2 data were used to map winter rapeseed with 10 m resolution. The mapping achieved a good result with overall accuracy and kappa coefficients exceeding 92% and 0.85, respectively. The PWRI-based method provides a new solution for high spatial resolution winter rapeseed mapping at a large scale.

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The effects of co-utilizing green manure and rice straw on soil aggregates and soil carbon stability in a paddy soil in southern China

ZHANG Zi-han, NIE Jun, LIANG Hai, WEI Cui-lan, WANG Yun, LIAO Yu-lin, LU Yan-hong, ZHOU Guo-peng, GAO Song-juan, CAO Wei-dong

2023, 22 (5): 1529-1545. DOI: 10.1016/j.jia.2022.09.025

Abstract （260） PDF in ScienceDirect

The co-utilization of green manure (GM) and rice straw (RS) in paddy fields has been widely applied as an effective practice in southern China. However, its effects on soil aggregate and soil organic carbon (SOC) stability remain unclear. In the present study, the effect of GM, RS, and co-utilization of GM and RS on particle size distribution of soil aggregates and SOC density fractions were measured in a field experiment. The experiment included six treatments, i.e., winter fallow (WF) without RS return (Ctrl), WF with 50% RS return (1/2RS), WF with 100% RS return (RS), GM without RS return (GM), GM with 50% RS return (GM1/2RS) and GM with 100% RS return (GMRS). The results showed that the proportion of small macro-aggregates (0.25–2 mm) and the mean weight diameter (MWD) of aggregates in the GMRS treatment was greater (by 18.9 and 3.41%, respectively) than in the RS treatment, while the proportion of silt+clay particles (<0.053 mm) was lower (by 14.4%). The concentration of SOC in microaggregates (0.053–0.25 mm) and silt+clay particles was higher in the GMRS treatment than in GM and RS treatments individually. The concentration and proportion of free light organic carbon (fLOC) in aggregates of various particle sizes and bulk soil was greater in the GMRS treatment than the RS treatment, whereas the concentration and proportion of mineral-associated organic carbon in small macroaggregates, microaggregates, and bulk was lower in the GMRS treatment than in the RS treatment. The proportion of intra-aggregate particulate organic carbon (iPOC) was greater in the GMRS treatment than in GM treatment. The GMRS treatment had strong positive effects on iPOC in small macroaggregates, suggesting that SOC was transferred from fLOC to iPOC. In conclusion, co-utilizing green manure and rice straw cultivated the SOC pool by increasing the concentration of fLOC and improved soil carbon stability by promoting the sequestration of organic carbon in iPOC as a form of physical protection.

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Effects of erect panicle genotype and environment interactions on rice yield and yield components

WANG Yuan-zheng, Olusegun IDOWU, WANG Yun, HOMMA Koki, NAKAZAKI Tetsuya, ZHENG Wen-jing, XU Zheng-jin, SHIRAIWA Tatsuhiko

2023, 22 (3): 716-726. DOI: 10.1016/j.jia.2022.08.013

Abstract （241） PDF in ScienceDirect

The dense and erect panicle (EP) genotype conferred by DEP1 has been widely used in the breeding of high-yield Chinese japonica rice varieties. However, the breeding value of the EP genotype has rarely been determined at the plant population level. Therefore, the effects of the interaction of EP genotype and the environment at different locations and times on rice yield and its various components were investigated in this study. Two sets of near-isogenic lines (NILs) of EP and non-EP (NEP) genotypes with Liaojing 5 (LG5) and Akitakomachi (AKI) backgrounds were grown in the field in 2016 and 2017 in Shenyang, China, and Kyoto, Japan. In 2018, these sets were grown only in Kyoto, Japan. The average yields of the EP and NEP genotypes were 6.67 and 6.13 t ha⁻¹ for the AKI background, and 6.66 and 6.58 t ha⁻¹ for the LG5 background, respectively. The EP genotype positively affected panicle number (PN) and grain number per square meter (GNPM), mostly resulting in a positive effect on harvest index (HI). In contrast, the EP genotype exerted a negative effect on thousand-grain weight (KGW). The ratio of the performance of the EP genotype relative to the NEP genotype in terms of yield and total biomass correlated positively with mean daily solar radiation during a 40-day period around heading. These results indicate that the effectiveness of the EP genotype depends on the availability of solar radiation, and the effect of this genotype is consistently positive for sink formation, conditional in terms of source capacity, and positive in a high-radiation environment.

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QTL analysis of early flowering of female flowers in zucchini (Cucurbita pepo L.)

QU Shu-ping, YANG Dan, YU Hai-yang, CHEN Fang-yuan, WANG Ke-xin, DING Wen-qi, XU Wen-long, WANG Yun-li

2023, 22 (11): 3321-3330. DOI: 10.1016/j.jia.2022.09.009

Abstract （188） PDF in ScienceDirect

Early flowering promotes early maturity, production, and the capacity to counteract biotic and abiotic stresses, making it an important agronomic trait in zucchini. The present study demonstrated that the zucchini inbred line ‘19’ consistently flowered early, taking significantly fewer days to bloom the first female flower (DFF) than the inbred line ‘113’. Genetic analysis revealed that DFF, an inheritable quantitative trait, is controlled by multiple genes. Based on the strategy of quantitative trait locus (QTL) sequencing (QTL-seq) combined with linkage analysis, three QTLs for DFF were identified on chromosomes 4, 11, and 20. This study used additional F₂ populations grown under different environmental conditions for QTL mapping analysis of DFF with insertion/deletion (InDel) markers to validate these results. Using the composite interval mapping (CIM) method of R/qtl software, we only identified one major locus under all environmental conditions, located in a 117-kb candidate region on chromosome 20. Based on gene annotation, gene sequence alignment, and qRT-PCR analysis, we found that the Cp4.1LG20g08050 gene encoding a RING finger protein may be a candidate gene for the opposite regulation of early flowering in zucchini. In summary, these results lay a foundation for a better understanding of early flowering and improving early flowering-based breeding strategies in zucchini.

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Overexpression of the MADS-box gene SlMBP21 alters leaf morphology and affects reproductive development in tomato

WANG Yun-shu, GUO Peng-yu, ZHANG Jian-ling, XIE Qiao-li, SHEN Hui, HU Zong-li, CHEN Guo-ping

2021, 20 (12): 3170-3185. DOI: 10.1016/S2095-3119(21)63638-9

Abstract （230） PDF in ScienceDirect

Fruit yield is the most important horticultural trait of tomato. SlMBP21, a SEPALLATA subclass MADS-box gene has been reported to have functions in regulating pedicel abscission zone identity and development and controlling sepal size in tomato. However, we generated transgenic tomato plants which overexpress SlMBP21 and found the transformants displayed curly leaves, abnormally shaped flowers with twisted and opened stamens, reduced yield parameters, and small and light seeds. Our studies on the gain-of-function phenotype and gene expression level showed that its novel aspects played important roles in determining leaf morphology, flower and inflorescence architecture, and seed size, as well as the fruit yield. Overexpression of SlMBP21 in tomato resulted in curly leaves with fewer leaflets due to the regulation of the critical leaf polarity genes that cause an imbalance between the midvein adaxial–abaxial cell growth. Defects in the architecture of flowers and inflorescences resulted in reduced fruit set. Furthermore, we demonstrated that SlMBP21 plays its role through inhibiting the expression of the genes involved in the determination of seed development in tomato and SlMBP21 protein can interact with other MADS-box protein (SlAGL11, TAGL1 and SlMBP3) to control seed size. Thus, these results suggest that overexpression of SlMBP21 causes multiple types of damage to plant growth and development, especially fruit yield, in tomato.

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Metabolic responses to combined water deficit and salt stress in maize primary roots

LI Peng-cheng, YANG Xiao-yi, WANG Hou-miao, PAN Ting, YANG Ji-yuan, WANG Yun-yun, XU Yang, YANG Ze-feng, XU Chen-wu

2021, 20 (1): 109-119. DOI: 10.1016/S2095-3119(20)63242-7

Abstract （143） PDF in ScienceDirect

Soil water deficit and salt stress are major limiting factors of plant growth and agricultural productivity. The primary root is the first organ to perceive the stress signals for drought and salt stress. In this study, maize plant subjected to drought, salt and combined stresses displayed a significantly reduced primary root length relative to the control plants. GC-MS was used to determine changes in the metabolites of the primary root of maize in response to salt, drought and combined stresses. A total of 86 metabolites were measured, including 29 amino acids and amines, 21 organic acids, four fatty acids, six phosphoric acids, 10 sugars, 10 polyols, and six others. Among these, 53 metabolites with a significant change under different stresses were identified in the primary root, and the content of most metabolites showed down-accumulation. A total of four and 18 metabolites showed significant up- and down-accumulation to all three treatments, respectively. The levels of several compatible solutes, including sugars and polyols, were increased to help maintain the osmotic balance. The levels of metabolites involved in the TCA cycle, including citric acid, ketoglutaric acid, fumaric acid, and malic acid, were reduced in the primary root. The contents of metabolites in the shikimate pathway, such as quinic acid and shikimic acid, were significantly decreased. This study reveals the complex metabolic responses of the primary root to combined drought and salt stresses and extends our understanding of the mechanisms involved in root responses to abiotic tolerance in maize.

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Effects of subsoiling depth, period interval and combined tillage practice on soil properties and yield in the Huang-Huai-Hai Plain, China

WANG Yun-xia, CHEN Shu-ping, ZHANG Dong-xing, YANG Li, CUI Tao, JING Hui-rong, LI Yu-huan

2020, 19 (6): 1596-1608. DOI: 10.1016/S2095-3119(19)62681-X

Abstract （160） PDF in ScienceDirect

Compaction layers are widely distributed in the Huang-Huai-Hai Plain, China, which restrict root growth and reduce yields. The adoption of subsoiling has been recommended to disrupt compacted soil layers and create a reasonable soil structure for crop development. In this paper, the effects of subsoiling depth (30, 35 and 40 cm), period interval (2 or 3 years) and combined pre-sowing tillage practice (rotary cultivation or ploughing) on soil condition improvement was studied on a tidal soil in the Huang-Huai-Hai Plain. Seven tillage patterns were designed by combining different subsoiling depths, period intervals and pre-sowing. The evaluation indicators for soil condition improvement were as follows: thickness of the plough layer and hard pan, soil bulk density, cone index, soil three-phase R values, alkali nitrogen content, crop yield, and economic benefits. The results showed that subsoiling can significantly improve the soil structure and physical properties. In all subsoiling treatments, the depth of 35 or 40 cm at a 2-year interval was the most significant. The thickness of the plough layer increased from 13.67 cm before the test to 21.54–23.45 cm in 2018. The thickness of the hard pan decreased from 17.68 cm before the test to 12.09–12.76 cm in 2018, a decrease of about 40.07%. However, the subsoiling combined pre-sowing tillage practice, that is, rotary cultivation or ploughing, was not significant for soil structure and physical properties. For all subsoiling treatments, the soil bulk density, cone index and soil three-phase R values of the 15–25 cm soil layer were significantly lower compared to single rotary cultivation. Subsoiling was observed to increase the soil alkaline nitrogen and water contents. The tillage patterns that had subsoiling at the depth of 35–40 cm at a 2-year interval combined with rotary cultivation had the highest alkali nitrogen and water contents, which increased by 31.08–34.23% compared with that of the single rotary cultivation. Subsoiling can significantly increase the yield both of wheat and corn, as well as the economic benefits. The treatment of subsoiling at the depth of 35 cm at an interval of 2 years combined with rotary cultivation had the highest annual yield and economic benefits. For this treatment, the annual yield and economic benefits increased by 14.55 and 62.87% in 2018, respectively. In conclusion, the tillage patterns that involved subsoiling at a depth of 35 cm at a 2-year interval along with rotary cultivation are suitable for the Huang-Huai-Hai Plain.

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Exploiting push-pull strategy to combat the tea green leafhopper based on volatiles of Lavandula angustifolia and Flemingia macrophylla

HAN Shan-jie, WANG Meng-xin, WANG Yan-su, WANG Yun-gang, CUI Lin, HAN Bao-yu

2020, 19 (1): 193-203. DOI: 10.1016/S2095-3119(19)62778-4

Abstract （181） PDF in ScienceDirect

Thirteen volatile compounds were identified from Flemingia macrophylla plants. Eight major components significantly attracted the tea green leafhoppers, Empoasca flavescens F. Based on their relative abundances, following synthetic blends were made for field experiments: 1) eight-component-attractant blend included Z-3-hexen-1-ol, Z-3-hexenyl acetate, Z-ocimene, MeSA, Z-3-hexenyl butyrate, dodecane, hexadecane and nonanal at 10, 10, 1, 11, 2, 6, 2 and 4 mg mL^–1 in n-hexane, respectively; 2) four-component-attractant blend #1 contained hexadecane, Z-3-hexenyl acetate, Z-3-hexen-1-ol and nonanal at 2, 10, 10 and 4 mg mL^–1 in n-hexane, respectively; 3) four-component-attractant blend #2 contained hexadecane, Z-3-hexenyl acetate, Z-3-hexen-1-ol and MeSA at 2, 10, 10 and 11 mg mL^–1 in n-hexane, respectively. Thymol and 1-methoxy-4-methyl-2-(1-methylethyl)-benzene, identified from Lavandula angustifolia aeration samples, significantly repelled the leafhopper as strong repellents when tested alone or in combination at 10 mg mL^–1. For field bioassays, each attractant lure was attached to a bud green sticky board hung from a bamboo stick at above tea plant level for catching the leafhoppers, whereas the repellent dispenser was tied to a tea branch inside tea clump for pushing the leafhoppers away from tea clumps. The results showed that the eight-component-attractant blend caught similar numbers of the leafhopper as did the four-component-attractant blend #1 at about 53–79 leafhoppers/trap/day, which were significantly higher than those on the hexane-control bud green sticky boards. Average leafhopper catches from un-baited sticky boards were about 51–73 leafhoppers/trap/day when pushed by the repellents placed inside tea plants, with the two-component-repellent blend being more effective than their single components. When the two-component-repellent blend was further tested with the three attractant blends in a push-pull fashion, average trap catches ranged from 62 to 92 leafhoppers/trap/day. Control efficacy on the leafhoppers within the push-pull zones increased progressively from day 1 (43%) to day 5 (73%). This push-pull approach might have a great potential as a green control strategy for combating the tea green leafhoppers.

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The effects of aeration and irrigation regimes on soil CO₂ and N₂O emissions in a greenhouse tomato production system

CHEN Hui, HOU Hui-jing, WANG Xiao-yun, ZHU Yan, Qaisar Saddique, WANG Yun-fei, CAI Huan-jie

2018, 17 (2): 449-460. DOI: 10.1016/S2095-3119(17)61761-1

Abstract （818） PDF in ScienceDirect

Aerated irrigation has been proven to increase crop production and quality, but studies on its environmental impacts are sparse. The effects of aeration and irrigation regimes on soil CO₂ and N₂O emissions in two consecutive greenhouse tomato rotation cycles in Northwest China were studied via the static closed chamber and gas chromatography technique. Four treatments, aerated deficit irrigation (AI1), non-aerated deficit irrigation (CK1), aerated full irrigation (AI2) and non-aerated full irrigation (CK2), were performed. The results showed that the tomato yield under aeration of each irrigation regime increased by 18.8% on average compared to non-aeration, and the difference was significant under full irrigation (P<0.05). Full irrigation significantly increased the tomato yield by 23.9% on average in comparison to deficit irrigation. Moreover, aeration increased the cumulative CO₂ emissions compared to non-aeration, and treatment effects were significant in the autumn-winter season (P<0.05). A slight increase of CO₂ emissions in the two seasons was observed under full irrigation (P>0.05). There was no significant difference between aeration and non-aeration in soil N₂O emissions in the spring-summer season, whereas aeration enhanced N₂O emissions significantly in the autumn-winter season. Furthermore, full irrigation over the two seasons greatly increased soil N₂O emissions compared to the deficit irrigation treatment (P<0.05). Correlation analysis indicated that soil temperature was the primary factor influencing CO₂ fluxes. Soil temperature, soil moisture and NO₃^– were the primary factors influencing N₂O fluxes. Irrigation coupled with particular soil aeration practices may allow for a balance between crop production yield and greenhouse gas mitigation in greenhouse vegetable fields.

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Effects of neutral salt and alkali on ion distributions in the roots, shoots, and leaves of two alfalfa cultivars with differing degrees of salt tolerance

WANG Xiao-shan, REN Hai-long, WEI Zen-wu, WANG Yun-wen, REN Wei-bo

2017, 16 (08): 1800-1807. DOI: 10.1016/S2095-3119(16)61522-8

Abstract （604） PDF in ScienceDirect

The effects of neutral salt and alkali on the ion distribution were investigated in two alfalfa (Medicago sativa L.) cultivars, including Zhongmu 1, a high salt-tolerant cultivar, and Algonquin, a low salt-tolerant cultivar. The alkali stress expressed more serious growth inhibition than the neutral salt stress at the same Na+ concentration. Compared with Algonquin, Zhongmu 1 did not exhibit a higher alkali tolerance under the Na₂CO₃-NaHCO₃ treatment with the low Na+ concentration (50 mmol L^–1). The alkali increased the accumulation of Na⁺, Ca²⁺, and Mg²⁺ in the root and changed the Ca²⁺ and Mg²⁺ balance in the entire alfalfa plant. The salt and alkali stresses decreased the K+ and Fe³⁺ contents of the roots and leaves, the root Mn²⁺ content, and the shoot Zn²⁺ content, but they increased the Fe³⁺ accumulation of the shoots, the shoot and leaf Cu²⁺ contents, and the leaf Zn²⁺ content in both alfalfa cultivars. Based on the results obtained under the conditions of this experiment, we found that the salt and alkali stresses reduced the plant growth in both alfalfa cultivars, while the alkali caused a stronger stress than the neutral salt in alfalfa. Thus, we conclude that under hydroponic conditions, the deleterious effects of the alkali on plants are due to the distribution change of some trophic ion balance in the roots, shoots, and leaves of the plants by causing of Na+, CO₃^2–, and/or HCO₃^– stresses.

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Effects of CO₂ enrichment and spikelet removal on rice quality under open-air field conditions

JING Li-quan, WU Yan-zhen, ZHUANG Shi-teng, WANG Yun-xia, ZHU Jian-guo, WANG Yu-long, YANG Lian-xin

2016, 15 (9): 2012-2022. DOI: 10.1016/S2095-3119(15)61245-X

Abstract （1368） PDF in ScienceDirect

The increase of atmospheric carbon dioxide (CO₂) concentration adversely affect several quality traits of rice grains, but the biochemical mechanism remains unclear. The objectives of this study were to determine how changes in the source-sink relationship affected rice quality. Source-sink manipulation was achieved by free-air CO₂ enrichment from tillering to maturity and partial removal of spikelet at anthesis using a japonica rice cultivar Wuyunjing 23. Enrichment with CO₂ decreased the head rice percentage and protein concentration of milled rice, but increased the grain chalkiness. In contrast, spikelet removal resulted in a dramatic increase in the head rice percentage and protein concentration, and much less grain chalkiness. Neither CO₂ enrichment nor spikelet removal affected the starch content, but the distribution of starch granule size showed distinct treatment effects. On average, spikelet removal decreased the percentage of starch granules of diameter >10 and 5–10 μm by 23.6 and 5.6%, respectively, and increased those with a diameter of 2–5 and <2 μm by 4.6 and 3.3%, respectively. In contrast, CO₂ elevation showed an opposite response: increasing the proportion of large starch granules (>5 μm) and decreasing that of <5 μm. The starch pasting properties were affected by spikelet removal much more than by CO₂ elevation. These results indicated that the protein concentration and starch granule size played a role in chalkiness formation under these experimental conditions.

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Intercropping of rice varieties increases the efficiency of blast control through reduced disease occurrence and variability

HAN Guang-yu, LANG Jie, SUN Yan, WANG Yun-yue, ZHU You-yong, LU Bao-rong

2016, 15 (4): 795-802. DOI: 10.1016/S2095-3119(15)61055-3

Abstract （1683） PDF in ScienceDirect

Creating a crop-heterogeneous system by intraspecific mixtures of different rice varieties can substantially reduce blast diseases. Such variety mixtures provide an ecological approach for effective disease control, maintaining high yields with the minimum fungicide applications. Whether such an approach is universally applicable for random rice variety combinations and what is the variation pattern of the diseases under intercropping still remains unclear. We conducted two-year large-scale field experiments involving 47 rice varieties/lines and 98 variety-combinations to compare the occurrence of rice blast in monoculture and intercropping plots at multiple sites. In the experiments, the plant height of the selected traditional varieties was about 30 cm taller, and their life cycle was 10 days longer, than that of the improved rice varieties. The monoculture included either traditional or modern rice varieties grown in separate plots. The intercropping included both traditional and modern rice varieties planted together in the same plots. Results from the field experiments under natural disease conditions demonstrated significant reduction for rice blast disease in intercropping plots, compared with that in monoculture plots. For traditional varieties, the average blast incidence reduced from ~26% in monoculture to ~10% in intercropping, and the disease severity reduced from ~17 in monoculture to ~5 in intercropping. For modern varieties, the average blast incidence reduced from ~19% in monoculture to ~10% in intercropping, and the severity from ~10 in monoculture to ~4 in intercropping. Traditional rice varieties (~72%) had a much greater increase in the efficiency of disease control than modern varieties (~60%). In addition, substantially lower values of variance in the blast incidence and severity was detected among the variety combinations in intercropping plots than in monoculture plots. Based on these results, we conclude that the intercropping or mixture of rice varieties greatly reduces the occurrence and variation of rice blast disease in particular variety combinations, which makes the intercropping system more stable and consistent for disease suppression on a large scale of rice cultivation.

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Contribution of ear photosynthesis to grain yield under rainfed and irrigation conditions for winter wheat cultivars released in the past 30 years in North China Plain

WANG Yun-qi, XI Wen-xing, WANG Zhi-min, WANG Bin, XU Xue-xin, HAN Mei-kun, ZHOU Shun-li, ZHANG Ying-hua

2016, 15 (10): 2247-2256. DOI: 10.1016/S2095-3119(16)61408-9

Abstract （1673）

To understand the contribution of ear photosynthesis to grain yield and its response to water supply in the improvement of winter wheat, 15 cultivars released from 1980 to 2012 in North China Plain (NCP) were planted under rainfed and irrigated conditions from 2011 to 2013, and the ear photosynthesis was tested by ear shading. During the past 30 years, grain yield significantly increased, the flag leaf area slightly increased under irrigated condition but decreased significantly under rainfed condition, the ratio of grain weight:leaf area significantly increased, and the contribution of ear photosynthesis to grain yield changed from 33.6 to 64.5% and from 32.2 to 57.2% under rainfed and irrigated conditions, respectively. Grain yield, yield components, and ratio of grain weight:leaf area were positively related with contribution of ear photosynthesis. The increase in grain yield in winter wheat was related with improvement in ear photosynthesis contribution in NCP, especially under rainfed condition.

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Empirical study on optimal reinsurance for crop insurance in China from an insurer’s perspective

ZHOU Xian-hua, WANG Yun-bo, ZHANG Hua-dong, WANG Ke

2015, 14 (10): 2121-2133. DOI: 10.1016/S2095-3119(14)60998-9

Abstract （1360） PDF in ScienceDirect

This study investigates the optimal reinsurance for crop insurance in China in an insurer’s perspective using the data from Inner Mongolia, Jilin, and Liaoning, China. On the basis of the loss ratio distributions modeled by AnHua Crop Risk Evaluation System, we use the empirical model developed by Tan and Weng (2014) to study the optimal reinsurance design for crop insurance in China. We find that, when the primary insurer’s loss function, the principle of the reinsurance premium calculation, and the risk measure are given, the level of risk tolerance of the primary insurer, the safety loading coefficient of the reinsurer, and the constraint on reinsurance premium budget affect the optimal reinsurance design. When a strict constraint on reinsurance premium budget is implemented, which often occurs in reality, the limited stop loss reinsurance is optimal, consistent with the common practice in reality. This study provides suggestions for decision making regarding the crop reinsurance in China. It also provides empirical evidence for the literature on optimal reinsurance from the insurance market of China. This evidence undoubtedly has an important practical significance for the development of China’s crop insurance.

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Responses of Plant Community and Soil Properties to Inter-Annual Precipitation Variability and Grazing Durations in a Desert Steppe in Inner Mongolia

WANG Zhen, YUN Xiang-jun, WEI Zhi-jun, Michael P Schellenberg, WANG Yun-feng, YANGXia , HOU Xiang-yang

2014, 13 (6): 1171-1182. DOI: 10.1016/S2095-3119(13)60660-7

Abstract （1791） PDF in ScienceDirect

Grazing can dramatically affect arid grassland communities that are very vulnerable to environmental changes due to its relatively short and sparse ground coverage, low biomass, sandy soil and inter-annual precipitation found in the desert steppe. The study investigates the effects of different grazing durations on vegetation and soil properties of a desert steppe community. The experiment was conducted in Xisu Banner in Inner Mongolia with five treatments: CG (continuous grazing), 40UG (40 d ungrazed), 50UG (50 d ungrazed), 60UG (60 d ungrazed) and UG (ungrazed). The biomass of both shrub and annual-biennial plant communities were significantly decreased by CG. Continuous grazing and 40UG significantly reduced the ANPP (aboveground net primary productivity) by the end of the three year study. 60UG treatment increased soil organic carbon (OC), total nitrogen concentration (TN) and total phosphorus concentration (TP) concentrations and 50UG increased the TN and total phosphorus concentration (TK) concentrations, whereas CG, 40UG and 50UG decreased soil OC, TP and available phosphorus concentration (AP) concentrations. The perennial plant species of the desert steppe were generally tolerant for grazing. The annual-biennial plant species had large variability in ANPP because of the inter-annual precipitation. Our results highlight that inter-annual precipitation variations could strongly modify the community responses to grazing in arid ecosystems.

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GmPHR1, a Novel Homolog of the AtPHR1 Transcription Factor, Plays a Role in Plant Tolerance to Phosphate Starvation

LI Xi-huan, WANG Yun-jie, WU Bing, KONG You-bin, LI Wen-long, CHANG Wen-suo , ZHANG Cai-ying

2014, 13 (12): 2584-2593. DOI: 10.1016/S2095-3119(14)60775-9

Abstract （1900） PDF in ScienceDirect

GmPHR1 from soybean (Glycine max) was isolated and characterized. This novel homolog of the AtPHR1 transcription factor confers tolerance to inorganic phosphate (Pi)-starvation. The gene is 2751 bp long, with an 819-bp open reading frame and five introns. Analysis of transcription activity in yeast revealed that the full-length GmPHR1 and its C-terminal activate the reporter genes for His, Ade and Ura, suggesting that the C-terminal peptide functions as a transcriptional activator. Quantitative real-time PCR indicated that patterns of GmPHR1 expression differed. For example, under low-Pi stress, this gene was quickly induced in the tolerant JD11 after 0.5 h, with expression then decreasing slowly before peaking at 12-24 h. By contrast, induction in the sensitive Niumaohuang (NMH) was slow, peaking at 6 h before decreasing quickly at 9 h. GmPHR1 showed sub-cellular localization in the nuclei of onion epidermal cells and Arabidopsis roots. Growth parameters in wild-type (WT) Arabidopsis plants as well as in overexpression (OE) transgenic lines were examined. Under low-Pi conditions, values for shoot, root and whole-plant dry weights, root to shoot ratios, and lengths of primary roots were significantly greater in OE lines than in the WT. These data demonstrate that GmPHR1 has an important role in conferring tolerance to phosphate starvation.

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Genetic Analysis of Cold Tolerance at Seedling Stage and Heat Tolerance atAnthesis in Rice (Oryza sativa L.)

CHENG Li-rui, Veronica Uzokwe, WANG Yun, ZHU Linghua

2012, 12 (3): 359-367. DOI: 10.1016/S1671-2927(00)8553

Abstract （1980） PDF in ScienceDirect

A set of 240 introgression lines derived from the advanced backcross population of a cross between a japonica cultivar,Xiushui 09, and an indica breeding line, IR2061, was developed to dissect QTLs affecting cold tolerance (CT) at seedlingstage and heat tolerance (HT) at anthesis. Survival rate of seedlings (SRS) and spikelet fertility (SF), the index traits of CTand HT, showed significant differences between the two parents under stresses. A total of four QTLs (qSRS1, qSRS7,qSRS11a and qSRS11b) for CT were identified on chromosomes 1, 7, 11, and the Xiushui 09 alleles increased SRS at all lociexcept qSRS7. Four QTLs for SF were identified on chromosomes 4, 5, 6, and 11. These QTLs could be classified into twomajor types based on their behaviors under normal and stress conditions. The first was QTL expressed only under normalcondition; and the second QTL was apparently stress induced and only expressed under stress. Among them, two QTLs(qSF4 and qSF6) which reduced the trait difference between heat stress and normal conditions must have contributed toHT because of their obvious contribution to trait stability, and the IR2061 allele at the qSF6 and the Xiushui 09 allele at the qSF4improved HT, respectively. No similar QTL was found between CT at seedling stage and HT at anthesis. Therefore, it ispossible to breed a new variety with CT and HT by pyramiding the favorable CT- and HT-improved alleles at above locifrom Xiushui 09 and IR2061, respectively, through marker-assisted selection (MAS).

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