China’s grain security is a global issue. In this paper, grain production and consumption in China from 1981 to 2011 are analyzed empirically, and the physical limitations and strategic options for future sustainable grain production are discussed. China’s population is estimated to reach 1.4 billion in 2020 and to peak at about1.43 billion around 2030. With rapid urbanization, grain consumption per capita for food and feed will decrease slightly, and the total grain demand will increase to 525.4 Mt in 2020 and 546.3 Mt in 2030, accounting for increments of 31.9 and 52.8 Mt, respectively from a base of 493.6 Mt, the average of 2009–2011 production. Increased industrial use is the dominant factor, which will drive increase in grain demand in the future. Increase in grain production over the period 1981–2011 occurred mainly as a result of increases in yield per unit area but the significant increase in maize has been due to both cultivated area and yield. Limited arable land, declining area of cultivated grain and water shortage in the North China Plain are the most critical resources limiting further grain production, while the impacts of growing urbanization, rural aging and climate change are less significant. In order to ensure future grain security in China, the following strategic options must be adopted: optimizing existing population policy, strictly protecting cultivated land and ensuring conservation of grain crop areas, raising the ratio of agricultural use to other uses of water in the North China Plain, adjusting grain self-sufficiency ratio, reducing pressure on resources and increasing investments in agriculture and in developing agricultural technologies.

Coronatine (COR) is a structural and functional analogue of jasmonic acid that might be employed in agriculture to elicit plant resistance against various aggressors. However, the yield of COR is low both in chemosynthesis and biosynthesis, so broad investigation of COR is difficult. Coronatine combines two distinct components: coronafacic acid (CFA) and coronamic acid (CMA). Synthesis of both CMA and CFA is involved in l-isoleucine metabolism, so the objective of this work was to investigate if COR production can be improved by regulating amino acid biosynthesis in P. syringae pv. glycinea. Inhibition of dihydrodipicolinate synthase was achieved by removing the dapA gene via homologous recombination, which resulted in a COR yield by the dapA− mutant of about 1.5-fold greater than the wild strain. Thus, regulation of amino acid metabolism is a feasible way to increase COR production, which could be a more effective method than adding substrates into culture medium.

Brassinolide (BR) is a relatively new plant growth regulator. To test whether BR could be used to increase tolerance to water deficits in soybean, the effects of BR application on photosynthesis, assimilate distribution, antioxidant enzymes and seed yield were studied. BR at 0.1 mg l−1 was foliar applied at the beginning of bloom. Two levels of soil moisture (80% field capacity for well-watered control and 35% for drought-stressed treatment) were applied at pod initiation. BR treatment increased biomass accumulation and seed yield for both treatments. Drought stress inhibited translocation of assimilated 14C from the labeled leaf, but BR increased the translocation for both treatments. Drought stress depressed chlorophyll content and assimilation rate (A), while chlorophyll content and A of BR-treated plants were greater than that of drought-stressed plants. BR treatment increased maximum quantum yield of PS II, the activity of ribulose-1,5-bisphosphate carboxylase, and the leaf water potential of drought-stressed plants. Treatment with BR also increased the concentration of soluble sugars and proline, and the activities of peroxidase and superoxide dismutase of soybean leaves when drought-stressed. However, it decreased the malondialdehyde concentration and electrical conductivity of leaves under drought stress. This study show that BR can be used as a plant growth regulator to enhance drought tolerance and minimize the yield loss of soybean caused by water deficits.

Drought is a major environmental stress factor that affects growth and development of plants. Abscisic acid (ABA), osmotically active compounds, and synthesis of specific proteins, such as proteins that scavenge oxygen radicals, are crucial for plants to adapt to water deficit. LOS5/ABA3 (LOS5) encodes molybdenum-cofactor sulfurase, which is a key regulator of ABA biosynthesis. We overexpressed LOS5 in tobacco using Agrobacterium-mediated transformation. Detached leaves of LOS5-overexpressing seedlings showed lower transpirational water loss than that of nontransgenic seedlings in the same period under normal conditions. When subjected to water-deficit stress, transgenic plants showed less wilting, maintained higher water content and better cellular membrane integrity, accumulated higher quantities of ABA and proline, and exhibited higher activities of antioxidant enzymes, i.e., superoxide dismutase, catalase, peroxidase and ascorbate peroxidase, as compared with control plants. Furthermore, LOS5-overexpressing plants treated with 30% polyethylene glycol showed similar performance in cellular membrane protection, ABA and proline accumulation, and activities of catalase and peroxidase to those under drought stress. Thus, overexpression of LOS5 in transgenic tobacco can enhance drought tolerance.Highlights• Generation of transgenic tobacco overexpressing the Arabidopsis LOS5/ABA3 gene. • Overexpression of the transgene is driven by the super promoter. • Higher quantities of ABA and proline were accumulated in transgenic plants under water-deficit conditions.

•Later planting generated a better plant habit for mechanical cotton harvesting, without yield loss and late maturity.•Higher density produced a better plant habit for mechanical cotton harvesting, with stable yield and maturity.•Later planting combined with higher density is recommended for cotton management aiming to realize mechanical harvesting.Previous studies have indicated that mechanical cotton harvesting requires a compact plant habit without fiber yield and quality reduction. The objective of this study was to determine the effects of planting date and plant density on plant habit, yield, early maturity, and fiber quality of cotton in the Yellow River valley region of China, and thus to identify the appropriate planting date and plant density suitable for its mechanical harvesting. Field experiments were conducted in 2013 and 2014 in Hejian, Hebei Province, using a split-plot design with planting date as the main plot and plant density as the subplot. The results indicated that moderately late planting in late April or early May (P2) was appropriate for mechanical harvesting of cotton as relative to P1 (local traditional planting date, 10 d earlier than P2) and P3 (10 d later than P2). P2 showed a 2.4–5.7 cm greater height to the first fruiting branch (from the bottom) and a 4.7–11.3 cm higher lowest boll (harvestable boll nearest to the ground) compared with P1, which is helpful for decreasing yield loss and reducing intake of residual plastic mulch. In addition, P2 produced slightly greater yield than P1 and P3, and the percentage of open bolls in late September for P2 was similar to that of P1 and greater than for P3, suggesting a low risk of late maturity. For plant density, 8.9 plants m−2 (D2) was appropriate for mechanical harvesting compared with 6.6 plants m−2 (D1), the local traditional density for manual harvesting, and 12.3 plants m−2 (D3). D2 showed a 2.5 cm greater height to the first fruiting branch and a 4.2 cm higher lowest boll, and exhibited 2.9–3.6 and 2.6–3.9 cm shorter lengths of lower and middle fruiting branches than D1, respectively. This type of compact plant habit is conducive to efficient mechanical harvesting. Moreover, D2 produced a similar yield to D1 for both the rainy 2013 and the dry 2014, indicating yield stability. Although D3 had a more suitable plant habit for mechanical cotton harvesting, its yield level and maturity varied across years. There were no significant interactions between planting date and plant density in the majority of tested traits. The results will contribute to the development of integrated cotton management for upcoming mechanical harvesting in the Yellow River valley region of China.

Timing of harvest is critical for mechanical picking in cotton production, especially in those regions with double cropping system. Appropriate and safe harvest aids will improve timing and facilitate harvest of cotton in the double cropping system. Three defoliants (dimethipin, thidiazuron, and thidiazuron-diuron) and one boll opener (ethephon) were included in this research. They were evaluated for their effects on defoliation, boll opening, seedcotton yield, seed quality, and fiber quality of field grown cotton when used alone or as a mixture in 2009 and 2010. Defoliation and/or boll opening were increased by all three defoliants and ethephon, especially by mixtures of a defoliant and ethephon. First harvest of seedcotton was significantly increased with defoliant-ethephon mixtures. No significant adverse effects were observed on boll weight, lint percentage, seed quality, and fiber properties. It was estimated that tank mixes of ethephon and one of the three defoliants can improve the adjusted gross revenue. Boll opening can be used as an alternative indicator for the adjusted gross revenue, because, it was linearly and positively correlated with the relative adjusted gross revenue and convenient in measurements. Wheat seedling growth was not affected by thidiazuron, whereas its seedling emergence, root dry weight, relative water content, and electrolyte leakage were adversely affected by dimethipin and thidiazuron-diuron when concentration was above 340 and 100 g (a.i.) ha−1, respectively. 90% defoliation and 80% boll opening were observed with the high rate of thidiazuron-ethephon mixture, but no adverse effects on winter wheat. The results suggested that tank mixes of ethephon with thidiazuron can be used effectively and safely in the cotton-winter wheat double cropping system to improve yield without adverse effects on seed quality and fiber quality.

•Translocation and accumulation of mepiquat chloride (MC) controls plant internode elongation.•MC inhibited cell elongation by downregulating GhEXP and GhXTH2.•MC decreased endogenous GA accumulation through suppressing the GA biosynthetic and metabolic genes.The growth regulator mepiquat chloride (MC) is globally used in cotton (Gossypium hirsutum L.) canopy manipulation to avoid excess growth and yield loss. However, little information is available as to whether the modification of plant architecture by MC is related to alterations in gibberellic acid (GA) metabolism and signaling. Here, the role of GA metabolism and signaling was investigated in cotton seedlings treated with MC. The MC significantly decreased endogenous GA3 and GA4 levels in the elongating internode, which inhibited cell elongation by downregulating GhEXP and GhXTH2, and then reducing plant height. Biosynthetic and metabolic genes of GA were markedly suppressed within 2–10 d of MC treatment, which also downregulated the expression of DELLA-like genes. A remarkable feedback regulation was observed at the early stage of MC treatment when GA biosynthetic and metabolic genes expression was evidently upregulated. Mepiquat chloride action was controlled by temporal translocation and spatial accumulation which regulated GA biosynthesis and signal expression for maintaining GA homeostasis. The results suggested that MC application could reduce endogenous GA levels in cotton through controlled GA biosynthetic and metabolic genes expression, which might inhibit cell elongation, thereby shortening the internode and reducing plant height.

The plant steroid hormones, brassinosteroids (BRs), play important roles in plant growth, development, and responses to environmental stresses. BRs signal through receptors localized to the plasma membrane and other signaling components to regulate the BES1/BZR1 family of transcription factors, which modulates the expression of thousands of genes. How BES1/BZR1 and their interacting proteins function to regulate the large number of genes are not completely understood. Here we report that histone lysine methyltransferase SDG8, implicated in histone 3 lysine 36 di- and trimethylation (H3K36me2 and me3), is involved in BR-regulated gene expression. BES1 interacts with SDG8, directly or indirectly through IWS1, a transcription elongation factor involved in BR-regulated gene expression. The knockout mutant sdg8 displays a reduced growth phenotype with compromised BR responses. Global gene expression studies demonstrated that, while BR regulates about 5000 genes in wild-type plants, the hormone regulates fewer than 700 genes in sdg8 mutant. In addition, more than half of BR-regulated genes are differentially affected in sdg8 mutant. A Chromatin Immunoprecipitation (ChIP) experiment showed that H3K36me3 is reduced in BR-regulated genes in the sdg8 mutant. Based on these results, we propose that SDG8 plays an essential role in mediating BR-regulated gene expression. Our results thus reveal a major mechanism by which histone modifications dictate hormonal regulation of gene expression.

This study investigated whether uniconazole confers drought tolerance to soybean and if such tolerance is correlated with changes in photosynthesis, hormones and antioxidant system of leaves. Soybean plants were foliar treated with uniconazole at 50 mg L−1 at the beginning of bloom and then exposed to water deficit stress at pod initiation for 7 d. Uniconazole promoted biomass accumulation and seed yield under both water conditions. Plants treated with uniconazole showed higher leaf water potential only in water-stressed condition. Water stress decreased the chlorophyll content and photosynthetic rate, but those of uniconazole-treated plants were higher than the stressed control. Uniconazole increased the maximum quantum yield of photosystemand ribulose-1,5-bisphosphate carboxylase/oxygenase activity of water-stressed plants. Water stress decreased partitioning of assimilated 14C from labeled leaf to the other parts of the plant. In contrast, uniconazole enhanced translocation of assimilated 14C from labeled leaves to the other parts, except stems, regardless of water treatment. Uniconazole-treated plants contained less GA3, GA4 and ABA under well-watered condition than untreated plants, while the IAA and zeatin levels were increased substantially under both water conditions, and ABA concentration was also increased under water stressed condition. Under water-stressed conditions, uniconazole increased the content of proline and soluble sugars, and the activities of superoxide dismutase and peroxidase in soybean leaves but not the malondialdehyde content or electrical conductivity. These results suggest that uniconazole-induced tolerance to water deficit stress in soybean was related to the changes of photosynthesis, hormones and antioxidant system of leaves.

Crop productivity is greatly affected by soil salinity, so improvement in salinity tolerance of crops is a major objective of many studies. We overexpressed the Arabidopsis thaliana SOS1 gene, which encodes a plasma membrane Na+/H+ antiporter, in tobacco (Nicotiana tabacum cv. Xanthi-nc). Compared with nontransgenic plants, seeds from transgenic tobacco had better germination under 120 mM (mmol L−1) NaCl stress; chlorophyll loss in the transgenic seedlings treated with 360 mM NaCl was less; transgenic tobacco showed superior growth after irrigation with NaCl solutions; and transgenic seedlings with 150 mM NaCl stress accumulated less Na+ and more K+. In addition, roots of SOS1-overexpressing seedlings lost less K+ instantaneously in response to 50 mM NaCl than control plants. These results showed that the A. thaliana SOS1 gene potentially can improve the salt tolerance of other plant species.

•Plant growth regulator mepiquat chloride (MC) applied at early stages improved cotton quality without loss of yield.•Negative effects of increasing plant density could be partially compensated by positive effects of MC.•Effects of MC and plant density on cotton lint yield were additive.The growth regulator mepiquat chloride (MC) is used in cotton production across the globe to control plant growth and maximize yield and quality of cotton. With the conversion from hand picking to mechanical harvesting in China, plant densities are increased, and more compact plants are required, leading to the need to reconsider MC application schedules. Experiments were carried out in 2009 and 2010 to identify optimal use schedules of MC at four plant densities: 3.0, 4.5, 6.0 and 7.5 plants m−2. Eleven MC schedules were compared with respect to their effect on cotton yield and quality. Application of MC at squaring stage or at both squaring and flowering stages significantly improved cotton quality parameters: fiber length (by 1.7%) and fiber strength (by 2.8%) at all tested plant densities without significant loss of yields. However, average lint yield of all MC treatments over all densities and years was decreased by 4.6% due to a decrease in boll density and lint percentage which was only partly offset by an increase in boll weight. No effects on yield were also observed if MC applications were started at flowering stage, but such later starting application schedules only slightly improved fiber quality. The results suggest that use of MC at squaring or at both squaring and flowering stages is a viable strategy to improve cotton architecture, productivity and quality at high plant density in mechanized cotton production in the Yellow River cotton growing region in China.