The causes and impacts for heat stress in spring maize during grain filling in the North China Plain——A review

High-temperature stress(HTS) at the grain-filling stage in spring maize(Zea mays L.) is the main obstacle to increasing productivity in the North China Plain(NCP). To solve this problem, the physiological mechanisms of HTS, and its causes and impacts, must be understood. The HTS threshold of the duration and rate in grain filling, photosynthetic characteristics(e.g., the thermal stability of thylakoid membrane, chlorophyll and electron transfer, photosynthetic carbon assimilation), water status(e.g., leaf water potential, turgor and leaf relative water content) and signal transduction in maize are reviewed. The HTS threshold for spring maize is highly desirable to be appraised to prevent damages by unfavorable temperatures during grain filling in this region. HTS has negative impacts on maize photosynthesis by damaging the stability of the thylakoid membrane structure and degrading chlorophyll, which reduces light energy absorption, transfer and photosynthetic carbon assimilation. In addition, photosynthesis can be deleteriously affected due to inhibited root growth under HTS in which plants decrease their water-absorbing capacity, leaf water potential, turgor, leaf relative water content, and stomatal conductance. Inhibited photosynthesis decrease the supply of photosynthates to the grain, leading to falling of kernel weight and even grain yield. However, maize does not respond passively to HTS. The plant transduces the abscisic acid(ABA) signal to express heat shock proteins(HSPs), which are molecular chaperones that participate in protein refolding and degradation caused by HTS. HSPs stabilize target protein configurations and indirectly improve thylakoid membrane structure stability, light energy absorption and passing, electron transport, and fixed carbon assimilation, leading to improved photosynthesis. ABA also induces stomatal closure to maintain a good water status for photosynthesis. Based on understanding of such mechanisms, strategies for alleviating HTS at the grain-filling stage in spring maize are summarized. Eight strategies have the potential to improve the ability of spring maize to avoid or tolerate HTS in this study, e.g., adjusting sowing date to avoidHTS, breeding heat-tolerance varieties, and tillage methods, optimizing irrigation, heat acclimation, regulating chemicals, nutritional management, and planting geometric design to tolerate HTS. Based on the single technology breakthrough, a comprehensive integrated technical system is needed to improve heat tolerance and increase the spring maize yield in the NCP.     

China's meat and grain imports during 2000–2012 and beyond: A comparative perspective

This paper provides a review on China's meat trade for the 2000–2012 period and discusses its future development, with reference to China's grain trade. With marginal decreases in meat exports and slight increases in their imports, China's net imports of major meat products(including pork, beef, mutton and poultry but excluding meat offal) were just below 1 million tons in 2012, dwarfed by China's net imports of grains which reached 66.7 million tons in the same year. This slow growth in meat trade seems to contradict earlier expectations on increasing meat demand and imports, based upon projected shifts in consumption patterns driven by rapid per capita income growth. Several plausible explanations of this paradoxical trade pattern are offered, including mass imports of feed grains, persistent(but shrinking) gaps between Chinese and international meat prices, tariff barriers, and non-tariff measures. In the near future China may not be able to maintain such a lower profile on the world meat markets, as per capita income is projected to continue to rise and domestic production cost advantages erode due to rising labor costs. A model-based projection exercise indicates that under plausible assumptions China's meat imports may rise sharply by 2030.     

QTL for grain yield and yield parameters in winter wheat(Triticum aestivum L.)

Field trials with a set of 108 doubled haploid lines(DHs) derived from a cross between the Chinese winter wheat cvs.CA9613 and H1488 were run at Beijing(China).Phenotypic data were recorded for major agronomic yield traits,i.e.grain weight per ear,grain number per ear and thousand grain weight(Tgw) in two field trials at Beijing.Based on the phenotypic data and a genetic map comprising 168 SSR markers,an analysis of quantitative trait loci(QTL) was carried out for yield and yield parameters using the composite interval mapping(CIM) approach.A total of 14 QTL were detected for these traits across two environments.Four of these QTL located on chromosomes 1A and 2B,respectively,exhibited pleiotropic effects.Loci showing pleiotropic effects will be very useful for understanding the homeologous relationships of QTL and designing an appropriate marker-assisted selection programme by multi-trait selection in order to accumulate("pyramide") favorable alleles at different loci.     

An economic and viable approach to improve wheat quality in Qinghai–Tibetan Plateau,China

Wheat flour products are the main dietary component of the Qinghai–Tibetan Plateau(QTP) population in China.However, the high altitude restricts the local wheat quality and quantity, and the applied nitrogen rate is higher than the optimal rate for wheat planting. In this study, we considered whether reducing the amount of nitrogen fertilizer and introducing the superior varieties from the North China Plain(NCP) are viable ways to increase the wheat quality and quantity in the QTP. Three and fou...     

Significance of β-glucan in barley grain during breeding for brewing and nutritional properties

A method is given for determining the content of ??-glucan in grain of barley varieties, and polymorphism of the species in this trait, including collection and breeding accessions, is shown. Within the breeding nurseries of Kazakhstan, the ??-glucan content varies from 2.6 to 6.2% in spring and from 2.2 to 5.7% in winter barley grain, increasing under dry-farming conditions. For brewing purposes, accessions with a value of this index lower than 4%, some of which displayed relative stability across reseedings, are singled out. The need for purposeful breeding for the given trait, for which it is necessary to introduce it into the selection scheme, and use of identification methods are substantiated.     

A joint use of emergy evaluation,carbon footprint and economic analysis for sustainability assessment of grain system in China during 2000–2015

The rapid growth of grain yield in China accelerates a discussion on whether the grain system in China is sustainable. To answer the question, a comprehensive assessment from economic and environmental points is necessary. This study jointly used economic analysis(ECA), emergy evaluation(EME) and carbon footprint(CF) to analyze the environmental and economic sustainability of the grain production system in China based on the national statistical data during 2000–2015. Results showed that the costs of maize, wheat, rice and soybean had increased by 252-346% from 2000 to 2015, causing the lower profit of grain system in recent years. The situation resulted in a serious problem on economic sustainability of grain system in China. Meanwhile, the emergy sustainability index(ESI) of maize, wheat, rice and soybean systems were increasing during 2000–2015, and the CF on unit yield of the crops had been reduced by 10-30% in the study period. The results reflected the improved environmental sustainability of grain system in China during 2000–2015. Nevertheless, the emergy flow of industrial inputs for the crops were increased by 4-22% in the study period, and the CF from the inputs presented a growth rate of 16-23% as well during the same period. The results implied that the grain system in China was relying more on fossil-based inputs. Finally, according to the key points of cost, emergy and CF, we suggest that improving labor efficiency, advanced agricultural practices and optimizing cropping pattern will be effective ways to further improve the economic and environmental sustainability of grain system in China.     

Effects of long-term straw incorporation on nematode community composition and metabolic footprint in a rice–wheat cropping system

Soil nematode communities can provide valuable information about the structure and functions of soil food webs, and are sensitive to agricultural practices, including short-term straw incorporation. However, currently, such effects under longterm straw incorporation conditions at different fertility levels are largely unknown. Thus, we conducted a 13-year ongoing experiment to evaluate the effects of long-term straw incorporation on the structure and functions of the soil food web in low and high fertility soils through analyzing its effects on nematode communities, food web indices and metabolic footprints. Four treatments were included: straw removal(–S) under non-fertilized(–NPK) or fertilized(+NPK) conditions; and straw incorporation(+S) under –NPK or +NPK conditions. Soil samples from a 0–20 cm depth layer were collected when wheat and rice were harvested. Compared with straw removal, straw incorporation increased the abundances of total nematodes, bacterivores, plant-parasites and omnivores-predators, as well the relative abundances of omnivores-predators with increases of 73.06, 89.29, 95.31, 238.98, and 114.61% in –NPK soils and 16.23, 2.23, 19.01, 141.38, and 90.23% in +NPK soils, respectively. Regardless of sampling times and fertilization effects, straw incorporation increased the diversity and community stability of nematodes, as indicated by the Shannon-Weaver diversity index and maturity index. Enrichment and structure index did not show significant responses to straw incorporation, but a slight increase was observed in the structure index. The analysis of nematode metabolic footprints showed that straw incorporation increased the plant-parasite footprint and structure footprint by 97.27 and 305.39% in –NPK soils and by 11.29 and 149.56% in +NPK soils, but did not significantly influence enrichment, bacterivore and fungivore footprints. In conclusion, long-term straw incorporation, particularly under a low fertility level, favored the soil nematodes and regulated the soil food web mainly via a top-down effect.     

Effects of plant density and mepiquat chloride application on cotton boll setting in wheat–cotton double cropping system

Sowing cotton directly after harvesting wheat in the Yangtze River Valley of China requires early mature of cotton without yield reduction. Boll-setting period synchronisation and more yield bolls distributed at the upper and middle canopy layers are also required for harvesting. The objective of this study is to quantify the individual and interaction effects of plant density and plant growth regulator mepiquat chloride(MC) on temporal and spatial distributions of yield bolls, as well as yield and yield components. During the 2013–2016 cotton growing seasons, the experiments were conducted on a shortseason cotton cultivar CRRI50 at Yangzhou University, China. Various combinations of plant density(12.0, 13.5 and 15.0 plants m~(–2)) and MC dose(180, 270 and 360 g ha~(–1)) were applied on cotton plants. The combination of 13.5 plants m~(–2) and 270 g ha~(–1) MC resulted in the greatest boll number per unit area, the highest daily boll setting number and more than 90% of bolls positioned within 45–80 cm above the ground. In conclusion, appropriate MC dose in combination of high plant density could synchronize boll-setting period and retain more bolls at the upper and middle canopy layers without yield reduction in the system of direct-seeded cotton after wheat harvest, and thus overcome the labor-intensive problem in current transplanting cropping system.     

From “Food from Nowhere” to “Food from Here:” changing producer–consumer relations in Austria

The notion of a “third food regime” implies simultaneous processes of further global concentration and integration and at the same time resistance through new emerging producer–consumer relations. This paper examines these processes by looking at Austria over the last 30 years. While direct producer–consumer cooperatives established at an early point, today forms of community supported agriculture (CSA) are rare. This paper explains this by identifying a shift of the entire food system from “food from nowhere” to “food from here.” The account follows the early emergence of alternative food networks through the political appeal to consumer patriotism in connection with Austria joining the EU, to a sustained positioning of retail chains with regional and national food products. The paper argues that this satisfies the needs of a large proportion of consumers and discourages the emergence of new food initiatives. The paper follows the development of different approaches and their transformations until today. Thus a picture evolves of changing, and partly progressing consumer–producer relations in response to wider societal and political transformation processes. The results explain why the movement towards CSA is currently weak in Austria, but demonstrate at the same time how alternative food networks may contribute to a transformation of the food system.     

Interactions between phosphorus availability and microbes in a wheat–maize double cropping system: A reduced fertilization scheme

Mechanisms controlling phosphorus(P) availability and the roles of microorganisms in the efficient utilization of soil P in the wheat–maize double cropping system are poorly understood. In the present study, we conducted a pot experiment for four consecutive wheat–maize seasons(2016–2018) using calcareous soils with high(30.36 mg kg^–1) and low(9.78 mg kg^–1) initial Olsen-P content to evaluate the effects of conventional P fertilizer application to both wheat and maize(Pwm) ...     

Spatial and temporal changes of paddy rice ecosystem services in China during the period 1980–2014

The ecological systems services or multi-functionality of paddy rice cultivation are critical to the functioning of the Earth's life-support system. We estimated the ecosystem services value (ESV) of paddy rice during 1980–2014 across China. The results indicated that the ESV of the paddy field in China showed an upward trend during this period. The share of ESV on CO₂ sequestration was the highest, followed by ESV on temperature cooling and greenhouse gas (GHG) emission. The yield-scaled ESVs of Zones II (southern rice–upland crops rotation regions) and III (southern double rice production regions) were similar and significantly higher than the ESVs of Zones I (northeastern single rice production regions) and IV (Southwest rice–upland crops rotation regions). Between 1980 and 2014, the ESV of each region increased to varying degrees, except for the ESVs of Guangxi, Zhejiang, Fujian, and Guangdong. Such effects suggest the existence of a significant spatial–temporal variation in the total amount, structure, and density of ESV of paddy fields in China, which can further guide the development of future options for the adaptation of healthy rice production in China.     

Effect of long-term fertilization on the nitrogen status of leached chernozem and the nitrogen balance in a grain–beet crop rotation

It has been revealed that the 70-year-long application of fertilizers to a sugar beet crop rotation in the forest-steppe of the Central Chernozemic Zone has significantly affected the nitrogen status of leached chernozem and increased the content of mineral nitrogen and the mobility of nitrogen compounds. High application rates of mineral fertilizers create a positive nitrogen balance in the crop rotation and could minimize the losses of total nitrogen in the future.     

Use of two-stage dough mixing process in improving water distribution of dough and qualities of bread made from wheat–potato flour

The two-stage dough mixing process was innovated to improve the qualities of bread made from potato flour (PF) and wheat flour at a ratio of 1:1 (w/w). The final dough was first prepared from wheat flour before being added with PF. The effects of the method on enhancing the dough qualities were verified, and the distribution of water in gluten-gelatinized starch matrix of the doughs was investigated. We observed that the bread qualities were improved, as reflected by the increase of specific volume from 2.26 to 2.96 mL g^–1 and the decrease of crumb hardness from 417.93 to 255.57 g. The results from rheofermentometric measurements showed that the dough mixed using the developed mixing method had higher maximum dough height value, time of dough porosity appearance, and gas retention coefficient, as well as enhanced gluten matrix formation compared to that mixed by the traditional mixing method. The results from low-field nuclear magnetic resonance confirmed that the competitive water absorption between gluten and gelatinized starch could restrict the formation of gluten network in the dough mixed using the traditional mixing process. Using the novel mixing method, gluten could be sufficiently hydrated in stage 1, which could then weaken the competitive water absorption caused by gelatinized starch in stage 2; this could also be indicated by the greater mobility of proton in PF and better development of gluten network during mixing.     

Estimating daily actual evapotranspiration of a rice–wheat rotation system in typical farmland in the Huai River Basin using a two-step model and two one-step models

The objective of this study is to evaluate the performance of three models for estimating daily evapotranspiration(ET) by employing flux observation data from three years(2007, 2008 and 2009) during the growing seasons of winter wheat and rice crops cultivated in a farmland ecosystem(Shouxian County) located in the Huai River Basin(HRB), China. The first model is a two-step model(PM-K_c); the other two are one-step models(e.g., Rana-Katerji(R-K) and advection-aridity(AA)). The results showed that the energy closure degrees of eddy covariance(EC) data during winter wheat and rice-growing seasons were reasonable in the HRB, with values ranging from 0.84 to 0.91 and R2 of approximately 0.80. Daily ET of winter wheat showed a slow decreasing trend followed by a rapid increase, while that of rice presented a decreasing trend after an increase. After calibrating the crop coefficient(K_c), the PM–K_c model performed better than the model using the K_c recommended by the Food and Agricultural Organization(FAO). The calibrated key parameters of the R-K model and AA model showed better universality. After calibration, the simulation performance of the PM-K_c model was satisfactory. Both the R-K model and AA model underestimated the daily ET of winter wheat and rice. Compared with that of the R-K model, the simulation result of the AA model was better, especially in the simulation of daily ET of rice. Overall, this research highlighted the consistency of the PM-K_c model to estimate the water demand for rice and wheat crops in the HRB and in similar climatic regions in the world.     

Genome-wide characterization and expression analysis of WRKY family genes during development and resistance to Colletotrichum fructicola in cultivated strawberry (Fragaria×ananassa Duch.)

Based on the recently published whole-genome sequence of cultivated strawberry ’Camarosa’, in this study, 222FaWRKY genes were identified in the ’Camarosa’ genome. Phylogenetic analysis showed that the 222 FaWRKY candidate genes were classified into three groups, of which 41 were in group Ⅰ, 142 were in group Ⅱ, and 39 were in group Ⅲ. The 222 FaWRKY genes were evenly distributed among the seven chromosomes. The exon–intron structures and motifs of the WRKY genes had evolutionary diversity in di...     

Drip irrigation incorporating water conservation measures: Effects on soil water–nitrogen utilization,root traits and grain production of spring maize in semi-arid areas

The Northeast Plain is the largest maize production area in China, and drip irrigation has recently been proposed to cope with the effects of frequent droughts and to improve water use efficiency (WUE). In order to develop an efficient and environmentally friendly irrigation system, drip irrigation experiments were conducted in 2016–2018 incorporating different soil water conservation measures as follows: (1) drip irrigation under plastic film mulch (PI), (2) drip irrigation under biodegradable film mulch (BI), (3) drip irrigation incorporating straw returning (SI), and (4) drip irrigation with the tape buried at a shallow soil depth (OI); with furrow irrigation (FI) used as the control. The results showed that PI and BI gave the highest maize yield, as well as the highest WUE and nitrogen use efficiency (NUE) because of the higher root length density (RLD) and better heat conditions during the vegetative stage. But compared with BI, PI consumed more soil water in the 20–60 and 60–100 cm soil layers, and accelerated the progress of root and leaf senescence due to a larger root system in the top 0–20 cm soil layer and a higher soil temperature during the reproductive stage. SI was effective in improving soil water and nitrate contents, and promoted RLD in deeper soil layers, thereby maintaining higher physiological activity during the reproductive stage. FI resulted in higher nitrate levels in the deep 60–100 cm soil layer, which increased the risk of nitrogen losses by leaching compared with the drip irrigation treatments. RLD in the 0–20 cm soil layer was highly positively correlated with yield, WUE and NUE (P<0.001), but it was negatively correlated with root nitrogen use efficiency (NRE) (P<0.05), and the correlation was weaker in deeper soil layers. We concluded that BI had advantages in water–nitrogen utilization and yield stability response to drought stress, and thus is recommended for environmentally friendly and sustainable maize production in Northeast China.