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In the context of frequent food crises, Angola needs to improve the efficiency of agricultural production to meet the rigid domestic demand for food consumption. China has accumulated experience and technology in agricultural production over the years, it is a strategic partner for Angola, and Angola has a prominent place in the destination of Chinese investments. Therefore, agricultural cooperation between China and Angola based on mutual benefits will not only help Angola solve the problem of self-sufficiency in food but also provide a broad space for Chinese agricultural technology to “go global”, thereby providing reliable domestic food security solutions. Through the SWOT method, this study analysed Angola’s agricultural development prospects and the current situation of China and Angola’s agricultural cooperation to build a SWOT matrix and formulate reliable agricultural cooperation development strategies for promoting agricultural cooperation between China and Angola.

Planting green manure is an effective way to improve the agricultural environment and the quality of cultivated land in China. However, deviation from green manure planting willingness and behavior (DWB) becomes a serious obstacle to the promotion of green manure planting technology. For economic farmers, whether to plant green manure is a rational choice made after weighing up family endowments. In addition, ecological cognition plays a moderating role in the “willingness-behavior” transformation process of farmers’ green manure planting on the basis of family endowments. We selected four counties in which to conduct a questionnaire survey in Gansu and carried out interviews with 375 farmers. Based on the survey data, our study identified determinants that influence farmers’ DWB and examined the moderating effect of ecological cognition. In our paper, results show that the probability of farmers’ DWB is 41.87%. Farmers’ DWB is not only negatively affected by social network information and ecological compensation (eco-compensation) and positively influenced by the scale of cultivated land, but also restricted by human capital endowment characteristics such as age and education. In addition, ecological cognition played a significant moderating effect on farmers’ DWB. Farmers with high ecological cognition were more aware and capable of promoting green manure planting intentions into practice. Furthermore, different groups of farmers had different characteristics of DWB. The findings are useful and helpful in better understand the influencing factors of farmers’ DWB for policy makers and managers and can provide some effective support for policies designed to encourage farmers to adopt more sustainable green manure.

Bread wheat expanded its habitat from a core area of the Fertile Crescent to global environments within ~10,000 years. The genetic mechanisms of this remarkable evolutionary success are not well understood. By whole-genome sequencing of populations from 25 subspecies within the genera Triticum and Aegilops, we identified composite introgression from wild populations contributing to a substantial portion (4-32%) of the bread wheat genome, which increased the genetic diversity of bread wheat and allowed its divergent adaptation. Meanwhile, convergent adaptation to human selection showed 2- to 16-fold enrichment relative to random expectation-a certain set of genes were repeatedly selected in Triticum species despite their drastic differences in ploidy levels and growing zones, indicating the important role of evolutionary constraints in shaping the adaptive landscape of bread wheat. These results showed the genetic necessities of wheat as a global crop and provided new perspectives on transferring adaptive success across species for crop improvement.

BackgroundStructural variations (SVs) pervade the genome and contribute substantially to the phenotypic diversity of species. However, most SVs were ineffectively assayed because of the complexity of plant genomes and the limitations of sequencing technologies. Recent advancement of third-generation sequencing technologies, particularly the PacBio high-fidelity (HiFi) sequencing, which generates both long and highly accurate reads, offers an unprecedented opportunity to characterize SVs and reveal their functionality. Since HiFi sequencing is new, it is crucial to evaluate HiFi reads in SV detection before applying the technology at scale.ResultsWe sequenced wheat genomes using HiFi, then conducted a comprehensive evaluation of SV detection using mainstream long-read aligners and SV callers. The results showed the accuracy of SV discovery depends more on aligners rather than callers. For aligners, pbmm2 and NGMLR provided the most accurate results while detecting deletion and insertion, respectively. Likewise, cuteSV and SVIM achieved the best performance across all SV callers. We demonstrated that the combination of the aligners and callers mentioned above is optimal for SV detection. Furthermore, we evaluated the impact of sequencing depth on the accuracy of SV detection. The results showed that low-coverage HiFi sequencing is capable of generating high-quality SV genotyping.ConclusionsThis study provides a robust benchmark of SV discovery with HiFi reads, showing the remarkable potential of long-read sequencing to investigate structural variations in plant genomes. The high accuracy SV discovery from low-coverage HiFi sequencing indicates that skim HiFi sequencing is an ideal approach to study structural variations at the population level.

In China, returning wheat straw to the field (RWSF) is the most popular way of utilizing wheat straw. RWSF can not only improve soil quality, but also help to control agricultural pollution from wheat straw burning. However, the increased production cost caused by RWSF reduces farmers' enthusiasm to adopt this approach. This study estimated farmers' willingness to accept compensation (WTA) for RWSF by using the contingent valuation method (CVM), and identified determinants that influence farmers' WTA by using an ordered choice model (OCM). It aimed to determine how much compensation should be given to farmers for encouraging them to adopt RWSF and which factors affect their WTA. The results showed that, currently, the increased cost caused by adopting RWSF was 743 RMB/ha, and which was fully burdened by farmers. Although more than 90% of the surveyed farmers adopted RWSF, only 3.8% of these farmers were willing to adopt RWSF voluntarily without any compensation. The farmers' WTA of adopting RWSF was 479 RMB/ha, and it was much higher than the current subsidy rate of 300 RMB/ha in Jiangsu, which could not effectively encourage farmers to adopt RWSF voluntarily. Farmers' WTA is not only positively affected by the increasing production cost caused by RWSF and negatively influenced by the benefits resulting from RWSF, but also restricted by social-economic characteristics such as age, education, income etc. It is costly for the Chinese government to subsidize all the farmers adopting RWSF, letting farmers to become aware of the long-term environmental value of RWSF is an effective measure to motivate them to protect environment responsibly by adopting RWSF. These findings are useful in improving the current provincial subsidy policies or designing new subsidy policies nationwide for RWSF, and helpful in encouraging famers more sustainably adopting RWSF and promoting cleaner wheat production.

Nowadays, there is a growing interest in pro-environmental foods produced by pro-environmental practices. However, consumers’ payment motivations towards such foods are currently poorly understood. This manuscript provided a critical investigation of Chinese consumers’ intention to pay a premium (ITPP) for rice grown with green manure as crop fertilizer (GMR). One focus was the establishment of an explanatory structural research framework that includes effects of environmental behavior spillover (EBS) and public information induction (PII), another focus was to analyze the impacts of the selected structural elements on ITPP by introducing education as a moderator. Results suggest that consumers’ ITPP can be largely influenced by PII, therefore, for GMR marketers and policy makers, measures should be developed to widen consumers’ access to public information related to GMR and to improve their capacity of screening effective information. EBS, when ITPP remains low, emerged as a pivotal predictor of consumers’ ITPP. This observation provides us with the enlightenment that breeding consumers’ daily environmental behaviors is highly valued to inspire their payment intention in the early stages of GMR market development. Another finding is that, with the introduction of the educational variable, the influence coefficients of EBS and PII on ITPP increased from 0.42 and 0.53 to 0.61 and 0.66, respectively, which means that it is possible to boost consumers’ payment intention by improving their educational attainment. This study contributes to the existing literature by providing empirical evidence for the GMR industrial upgrading strategy and have significant implications for the environmental governance of the agricultural sector.

Reticulate evolution through the interchanging of genetic components across organisms can impact significantly on the fitness and adaptation of species. Bread wheat (Triticum aestivum subsp. aestivum) is one of the most important crops in the world. Allopolyploid speciation, frequent hybridization, extensive introgression, and occasional horizontal gene transfer (HGT) have been shaping a typical paradigm of reticulate evolution in bread wheat and its wild relatives, which is likely to have a substantial influence on phenotypic traits and environmental adaptability of bread wheat. In this review, we outlined the evolutionary history of bread wheat and its wild relatives with a highlight on the interspecific hybridization events, demonstrating the reticulate relationship between species/subspecies in the genera Triticum and Aegilops. Furthermore, we discussed the genetic mechanisms and evolutionary significance underlying the introgression of bread wheat and its wild relatives. An in-depth understanding of the evolutionary process of Triticum species should be beneficial to future genetic study and breeding of bread wheat.

Currently, the Chinese government is promoting the transformation of clean energy in rural areas to reduce the consumption of coal to cope with the smog. It is mainly based on “coal to gas”. The development of biomass resources in agricultural areas is an alternative means of energy supply. In order to improve rural energy structure, we propose to upgrade “coal to gas” to “coal to biomass” derived from centralized biogas production (CBP) and straw-briquetting fuel (SBF). This study deals with the question of financing such projects. The public–private partnership (PPP) model is seen as a response that can mobilize social capital to finance investments in these new modes of production and energy supply in rural areas. Based on an analysis of the strengths, weaknesses, opportunities and threats (SWOT) of the two projects considered above, an analytic hierarchy process (AHP) was carried out with the assistance of experts in order to clarify the strategic choices which are more suitable for investors. First, we built a PPP strategic-decision model. The decision model was divided into four strategies (pioneering strategy, struggling strategy, conservative strategy and striving strategy) and two development intensities (conservative and proactive). We used this method to construct a SWOT–AHP model of the PPP strategy for CBP and SBF based on the investigation from the experts. The strategic-decision model identified that a pioneering strategy based on opportunity type is promised for SBF, while a more aggressive type strategy in struggling strategy is essential for the CBP. In order to encourage investors to adopt a positive and optimistic attitude towards the two projects, the public authorities have a role of guidance to ensure the mobilization of the social capital necessary for the construction of the projects.

Bread wheat expanded its habitats from a small core area of the Fertile Crescent to global environments within ∼10,000 years. Genetic mechanisms of this remarkable evolutionary success are not well understood. By whole-genome sequencing of populations from 25 subspecies within generaTriticumandAegilops, we identified composite introgression from these wild populations contributing 13%∼36% of the bread wheat genome, which tremendously increased the genetic diversity of bread wheat and allowed its divergent adaptation. Meanwhile, convergent adaption to human selection showed 2- to 16-fold enrichment relative to random expectation inTriticumspecies despite their drastic differences in ploidy levels and growing zones, indicating the vital importance of adaptive constraints in the success of bread wheat. These results showed the genetic necessities of wheat as a global crop and provided new perspectives on leveraging adaptation success across species for crop improvement.

Urban air pollution generated from straw open burning after the harvest seasons in China has been one of the significant problems interfering with the city's proper functioning. This paper applied contingent valuation in a face to face survey to assess the individual willingness of urban residents in Henan, China to pay for corn straw burning ban to policy makers. Such assessments are important for policy makers to determine the investment and policy instruments for regulating environmental impacts of straw open burning. To investigate the determinants of the stated willingness to pay (WtP) a sample of 1890 urban residents in Henan, China was selected. The study used Tobit model. About 62% of respondents stated that they were willing to pay. The expected WtP was about 76.72 Chinese Yuan (RMB) per person per year for the total respondents and 142.70 RMB per person per year for observations with positive WtP bids. Aggregate value was between 3.41 and 3.90 billion RMB indicating that corn straw burning ban is of considerable economic value to Henan. Results from the study show that the experience of environmental protection, expenditure on protecting health from air pollution, influence of straw burning on respondent's health, life, work, household income, education, job place, and family size were significant variables explaining WtP. The results of the study will be useful for policy makers when making up their mind how much funds should be invested and what kinds of policy instruments could be suitable for banning straw burning. (C) 2018 Published by Elsevier Ltd.

Environmental impacts of milk production are depending on the production efficiency of livestock and cropland. A mode of integrated maize silage planting and dairy breeding system (IPBS) has been widely promoted in China, as a promising way to recycle manure, reduce chemical fertilizer consumption and improve soil quality. However, quantitative environmental impacts and mitigation potential of this system remains unclear. In this study, based on life cycle assessment (LCA), environmental performance of non-IPBS and IPBS were compared: non-IPBS only involved dairy cow breeding, whereas maize silage planting was incorporated in IPBS. Results indicated that, although 60% of the surveyed dairy farms adopted IPBS, the self-sufficiency rate of maize silage was 57%. Compared with non-IPBS, IPBS had apparent potential in reducing global warming potential (−14%), acidification potential (−10%), eutrophication potential (−18%), non-renewable energy use (−10%), water use (−8%) and land use (−13%). It is estimated that, in China, 81% of dairy farms could adopt IPBS, resulting in a reduction of approximately 21% in greenhouse gas (GHG) emissions to compared with current situation, but the premise is that 2.0 million ha cropland should be applied for maize silage cultivation. Interestingly, environmental performance of IPBS was affected by the self-sufficiency rate of maize silage and restricted by milk yield and maize silage yield. Thus, mitigation of environmental impacts of milk production could be realized by combining a short-term strategy of increasing maize silage planting area in dairy farms and a long-term plan for technological improvements in the yield of crop and milk.

This study investigated smallholder farmers' adoption preferences for cropping patterns of cover crops, duration of adoption, and supplementing technical support to reduce agrochemicals regarding sustainable farm management (SFM). A discrete choice experiment was conducted in the Hexi Corridor (D1) and the west Loess Plateau (D2) in northwest China. The results show that farmers in D1 preferred intercropping and rotating cover crops to the current single cropping system, while farmers in D2 prioritized intercropping over rotation and least preferred planting cover crops in marginal land in the double-cropping system. Farmers in both sites preferred 1 or 3 years of adoption over 5 years. Additionally, farmers in D2 preferred technical assistance to reduce the high proportion of agrochemicals. The results indicate that younger farmers with higher annual household incomes were most likely to opt out in D1. In D2, more agricultural labor inputs and raising livestock had positive effects on the adoption of the package. Moreover, farmers who cultivated cash crops were more reluctant to move away from the current cropping system. This study highlights the uses of cover crop intercropping and rotation combining with technical assistance in different agriculturally intensive cropping systems that may be useful in guiding site-specific policy.

The size of the top three leaves of rice plants is strongly associated with yield; thus, it is important to consider quantitative traits representing leaf size (e.g., length and width) when breeding novel rice varieties. It is challenging to measure such traits on a large scale in the field, and little is known about the genetic factors that determine the size of the top three leaves. In the present study, a population of recombinant inbred lines (RILs) and reciprocal single chromosomal segment substitution lines (SSSLs) derived from the progeny of a japonica Asominori × indica IR24 cross were grown under four diverse environmental conditions. Six morphological traits associated with leaf size were measured, namely length and flag leaf, length and flag, second and third leaves. In the RIL population, 49 QTLs were identified that clustered in 30 genomic region. Twenty-three of these QTLs were confirmed in the SSSL population. A comparison with previously reported genes/QTLs revealed eight novel genomic regions that contained uncharacterized ORFs associated with leaf size. The QTLs identified in this study can be used for marker-assisted breeding and for fine mapping of novel genetic elements controlling leaf size in rice.

Rice production holds a significant position in the Thai economy. Although it is the world's largest rice exporter, Thailand&rsquo, s increase in rice production is the result of an expansion in the cultivation area rather than an increase in yield per unit area. The present study was designed to estimate the technical efficiency and its governing factors for certified organic rice-growing farms in Yasothon Province, Thailand. A data envelopment model was employed to assess the technical efficiency of 328 farmer groups. The data revealed that the average technical efficiency was 23% and 28% under constant returns to scale (CRS) and variable returns to scale (VRS) specifications, respectively. Farmers can reduce the use of machinery, fertilizer, seed, and labor as input factors by about 80.1%, 25.62%, 24.72%, and 19.15%, respectively, while still achieving the same level of output. Multiple regression analysis was applied to estimate factors that affect the pure technical efficiency score (PTES) in the test regions. Results show that household size, farm size, water source, market accessibility, health symptoms, income, and labor were highly related to the TES and the amount of organic rice production. The regression coefficients of the predictors show that the income was the best predictor of the PTES at a significance level of p &lt, 0.05. It is concluded that the farmers can potentially increase their yields by up to 72%&ndash, 77% under current management practices.

The influence of instrumental variables on farmers ‘perceptions using rotation fallow as sustainable agriculture practices had been the aim of our research. By using simultaneous equations models, this study tried to understand the relationship between green manure farmer’s perceptions on using rotation-fallow and planting green manure in Guangxi Province, south of China. The results showed that subsidizing green manure farmers based on standard subsidy by the unit of green manure sown area; the training on the green manure planting technology or the demonstration preaching; the green manure farmers preference for the kinds of subsidy (funds, seeds, and mechanical services) were the mostly great drivers of the program of restoring planting green manure in the study area. These incentives measures must be enhanced as priority to restore definitely green manure planting. However, the findings of the study showed that the total income of the 2017 year, the area of an agricultural field of household and the household members (16–65 years old), providing labor in the agricultural field, have some influences on planting green manure and on farmer’s perceptions on using rotation-fallow as sustainable agriculture practices. Brief, the unobserved factors which influenced the endogenous factors play an important role to enhance widely the impact of farmers’ perceptions on planting green manure.

For the sake of reducing the application of chemical fertilizers (CF) and achieve the goal of Zero Growth of CF until 2020, Chinese government released the “Action Plan for Organic-Substitute-Chemical-Fertilizer (OSCF) for Fruits, Vegetables and Tea” and initially performed it in 100 pilot counties from 2017. Each pilot county rewarded 10 million CNY as subsidy to substitute CF with organic fertilizers (OF). This study examines the effects of the OSCF policy using survey data of 281 greenhouse vegetable farmers in the Shandong province of China. The Difference-in-Difference (DID) method is employed to get the net effects of the policy on the utilization of replacing CF. The results show that the OSCF policy helps to significantly reduce the application of CF and increase OF’s utilization for vegetable farmers, and on average CF drops 111.5 kg/ha while OF increases 346.36 kg/ha for the sampling farmers. Additional analysis reveals that the effects of the policy are heterogeneous across the cost of CF and household-level characteristics. The results provide evidences for further enhancing the policy effects.

In recent years, residue-to-energy utilization has become an important energy source that can alleviate the reliability of fossil fuel, and agricultural residue (AR) transportation has great potential for optimization in the AR supply chain. However, various methods presented make their correct implementation difficult for sustainable optimization. Therefore, four key issues of the AR transportation for bioenergy production have been thoroughly reviewed: (i) distribution of AR in cropland, (ii) estimation of transportation distance, (iii) variability of vehicle arrangements, and (iv) (de)centralized transportation patterns. This review has several findings. To begin with, land cover classification method with remote sensing technology is suggested to locate the distribution of AR, thereby being helpful for facilitates decision-making optimization. Second, electronic navigator applications (Google Maps or Baidu Maps) are recommended for transportation distance estimation, and the implementation of manipulating Baidu Maps with R is provided. Third, the vehicle selection bias would bring estimation gaps, so a vehicle database is required to satisfy the local needs. And finally, transportation distance, the requirement of AR pretreatments and brokers’ participation can affect the decision of (de)centralized transportation patterns. The findings and technical details discussed are especially useful for researchers and bioenergy project investors who intend to reduce the AR transportation cost in the future, especially for developing counties.

The Green Manure Planting Program (GMP), which is a typical case of payment for farmland ecosystem services, has come into play on conserving paddy fields in China. This paper analyses farmers’ willingness to accept (WTA) for adopting GMP by employing the contingent valuation method (CVM) and Double-hurdle (D-H) model on the basis of a sample data set containing information on 1217 farmers in five provinces in southern paddy fields region (SPF) of China. The results show that farmers’ WTA for adopting GMP was 3323 CNY/ha per year, which is much higher than the current compensation standards (com-standards) in the study region. This result explains why the current policy does invalidly stimulate farmers for adopting GMP. Farmers’ WTA is not only influenced by the cost-benefit effect of GMP adoption, but also impacted by their perceived environmental value in improving the quality of paddy fields as well as the demographic and socioeconomic information such as farmers’ age, political identities, income and paddy field area. It is costly if the government compensates all farmers who adopt GMP, letting farmers aware of more environmental value of GMP and maximally promoting the transformation of these environmental values into economic benefits is an effective measure to encourage them to adopt GMP.The results of this study can guide policy makers in determining the budget for GMP compensation and designing systematic compensation mechanism hence improve the sustainability of paddy fields conservation.

In the highest soil erosion regions of arid and semiarid northwest China, water resource deficits and farmland misuse have further exacerbated soil degradation. Therefore, understanding how farmers in diverse agroclimatic zones perceive and respond to different conservation practices is important to the implementation of sustainable agriculture practices (SAPs). To this end, this study uses a best&ndash, worst scaling approach to examine the adoption preferences for nine SAPs among grain and cash crop farmers and investigates the influence of farm and climatic characteristics on adoption preferences based on a face to face survey of 554 households in Gansu province, which is classified as an arid and semiarid area in northwest China. Both grain and cash crop farmers had stronger preferences for the practices of using organic instead of chemical fertilizers and of improving irrigation practices. In addition, while cash crop farmers also had strong preferences for cover crop-related practices, they preferred long-term fallows least. Household income, livestock, and precipitation influence the potential perceived importance of SAPs. The different perceived importance of these practices suggests new possible combinations or packages for a sustainable agriculture program during the cropping structure adjustment in Gansu.

The size of the top three leaves of rice plants is strongly associated with yield; thus, it is important to consider quantitative traits representing leaf size (e.g., length and width) when breeding novel rice varieties. It is challenging to measure such traits on a large scale in the field, and little is known about the genetic factors that determine the size of the top three leaves. In the present study, a population of recombinant inbred lines (RILs) and reciprocal single chromosomal segment substitution lines (SSSLs) derived from the progeny of a japonica Asominori × indica IR24 cross were grown under four diverse environmental conditions. Six morphological traits associated with leaf size were measured, namely length and flag leaf, length and flag, second and third leaves. In the RIL population, 49 QTLs were identified that clustered in 30 genomic region. Twenty-three of these QTLs were confirmed in the SSSL population. A comparison with previously reported genes/QTLs revealed eight novel genomic regions that contained uncharacterized ORFs associated with leaf size. The QTLs identified in this study can be used for marker-assisted breeding and for fine mapping of novel genetic elements controlling leaf size in rice.

Urban households account for most of the milk consumption in China, but their consumption is hampered by safety concerns. Using survey data collected in Beijing and Harbin in 2010, this paper simultaneously analyses urban households' milk consumption using a multiple linear model and their willingness-to-pay for milk safety using an ordered choice model. The results of this study show that as income increases, urban households consume more milk and are willing to pay a higher premium for milk safety. Modern food marketing channels play a positive role in stimulating milk consumption and building consumers' confidence in milk safety. The growth in the elderly population influences milk consumption positively, but their demand for milk safety is negatively affected by higher price. The combined analysis of households' demand for milk quantity and safety may be useful to the Chinese government in promoting the development of the domestic milk industry and to dairy firms in exploring the milk market in China.

Planting green manure in fallow croplands in winter can bring various economic and environmental benefits, including increased food production, carbon capture and sequestration, soil retention, sandstorm prevention, water retention, and provision of habitat for biodiversity. However, the increased production cost of planting green manure reduces farmers&rsquo, willingness to adopt this approach, which is unfavorable for its sustainability. This research aims to investigate the influence of instrumental variables on farmers&rsquo, perceptions of sustainable agriculture practices, especially the use of rotation fallow, and tries to understand the relationship between farmers&rsquo, perceptions of using rotation fallow and planting green manure under incentive measures adopted by local authorities in Guangxi Province, China. Using simultaneous equation models, the results show that subsidies and planting training were the most important drivers for restoring green manure planting in the target region. These incentive measures could be further enhanced as a priority to restore green manure planting. The study also finds that socioeconomic factors such as farmer&rsquo, s income, area of farmland, and labor for agricultural production have a certain influence on planting green manure planting and on farmers&rsquo, perceptions of using rotation fallow as a form of sustainable agriculture practice.

Key message This article used seven characters from the 2D image analysis to dissect the genetic architecture underlying rice grain shape in onejaponica × indicapopulation consisting of 215 recombinant inbred lines. Abstract Two-dimensional (2D) digital image analysis is efficient for investigating the rice grain shape characters in large genetic and breeding populations. In this study, we used 2D image analysis to investigate seven characters, i.e., grain length (GL), grain width (GW), length-to-width ratio (LW), grain area (GA), grain circumference (GC), grain diameter (GD), and grain roundness (GR), in one japonica × indica genetic population consisting of 215 recombinant inbred lines. GL and GW can be recorded manually as well, and have been extensively used together with LW (i.e., GL/GW) in genetic studies on grain shape. GC and GA can be hardly measured manually, and have not been used together with GD and GR. Results indicated that the seven characters could be precisely measured by 2D image analysis, genotype by environment interaction was low, and heritability was high. Each character was controlled by a few major stable genes and multiple minor additive genes. A total of 51 QTL were detected for the seven characters across four diverse environments, 22 from GL, GW, and LW, the three traditional characters, and 29 from the other four characters. The 51 QTL were clustered in eighteen marker intervals. Comparing with previous studies and analyzing the stability of identified QTL, we found six non-reported marker intervals, one each on chromosomes 2 and 3, and two each on chromosomes 6 and 8. The newly identified loci and the large-scale phenotyping system would greatly improve our knowledge about the genetic architecture and the future rice breeding on grain shape. Electronic supplementary material The online version of this article (doi:10.1007/s00122-015-2560-7) contains supplementary material, which is available to authorized users.