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Methyl jasmonate (MeJA) and its free-acid form, jasmonic acid (JA) are naturally occurring plant growth regulators widely distributed in higher plants. In order to improve the sensitivity for the analysis of MeJA at low levels in small amounts of plant samples, a monoclonal antibody (MAb) (designated as MAb 3E5D7C4B6) against MeJA was derived from a JA-bovine serum albumin (BSA) conjugate as an immunogen. The antibody belongs to the IgG1 subclass with a κ type light chain and has a dissociation constant of approximately 6.07 × 10−9 M. MAb3E5D7C4B6 is very specific to MeJA. It was used to develop a direct competitive enzyme-linked immunosorbent assay (dcELISA), conventional and simplified indirect competitive ELISAs (icELISA). JA was derivatized into MeJA for the ELISA analysis. The IC50 value and detection range for MeJA were, respectively, 34 and 4–257 ng/mL by the conventional icELISA, 21 and 3–226 ng/mL by the simplified icELISA and 5.0 and 0.7–97.0 ng/mL by the dcELISA. The dcELISA was more sensitive than either the conventional or simplified icELISA. The assays were used to measure the content of jasmonates as MeJA in tobacco leaves under drought stress or inoculated with tobacco mosaic virus and tomato leaves inoculated with tomato mosaic virus or Lirioinyza sativae Blanchard as compared with the corresponding healthy leaves. The increased jasmonates content indicated its role in response to the drought stress and pathogens. [ABSTRACT FROM AUTHOR]

Global agriculture is facing multiple challenges to meet the food demands, optimize resource utilization, and mitigate the climate change. A field study, combined with the life cycle assessment (LCA), was conducted to select the effective and sustainable cropping systems in northwestern China. The study compared four maize‐based intercropping and corresponding monoculture systems on crop yield, evapotranspiration (ET), water use efficiency (WUE), profitability, and carbon footprint (CF). Maize/wheat intercropping had the highest energy yield (532.5 GJ/ha, on average) and maize equivalent energy yield (MEEY) (522.3 G/ha, on average), followed by those from the maize/rape intercropping system, and the lowest by the sole potato system. The WUE of maize equivalent energy yield (WUEMEEY) was the highest (1.06 GJ ha−1 mm−1) for sole rape system, followed by those for the maize/wheat and maize/rape intercropping systems. Maize/potato intercropping had the highest benefit: cost ratio at 3.30, followed by those for the maize/wheat intercropping (2.58), sole potato (2.57), and maize/rape intercropping (2.53). Lower CF and higher net ecosystem economic budget (NEEB) were observed in maize‐based intercropping systems. The maize/wheat intercropping system had the lowest CF per maize equivalent energy yield (CFm) (10.7 kg CO2‐eq GJ−1 year−1), and the maize/potato intercropping system had the lowest CF per unit economic output (CFe) (0.14 kg CO2‐eq US$−1 year−1), and the highest NEEB (7,352.8 US$/ha). The data presented indicate that maize‐based intercropping system may be a viable practice for the synthesized goals of higher productivity and profitability while lesser environmental footprint in a water‐scarce region of northwest China. [ABSTRACT FROM AUTHOR]

Elevated atmospheric CO2 (eCO2) generally increases carbon input in rice paddy soils and stimulates the growth of methane‐producing microorganisms. Therefore, eCO2 is widely expected to increase methane (CH4) emissions from rice agriculture, a major source of anthropogenic CH4. Agricultural practices strongly affect CH4 emissions from rice paddies as well, but whether these practices modulate effects of eCO2 is unclear. Here we show, by combining a series of experiments and meta‐analyses, that whereas eCO2 strongly increased CH4 emissions from paddies without straw incorporation, it tended to reduce CH4 emissions from paddy soils with straw incorporation. Our experiments also identified the microbial processes underlying these results: eCO2 increased methane‐consuming microorganisms more strongly in soils with straw incorporation than in soils without straw, with the opposite pattern for methane‐producing microorganisms. Accounting for the interaction between CO2 and straw management, we estimate that eCO2 increases global CH4 emissions from rice paddies by 3.7%, an order of magnitude lower than previous estimates. Our results suggest that the effect of eCO2 on CH4 emissions from rice paddies is smaller than previously thought and underline the need for judicious agricultural management to curb future CH4 emissions. [ABSTRACT FROM AUTHOR]

Rice is a staple food for nearly half of the world's population, but rice paddies constitute a major source of anthropogenic CH4 emissions. Root exudates from growing rice plants are an important substrate for methane‐producing microorganisms. Therefore, breeding efforts optimizing rice plant photosynthate allocation to grains, i.e., increasing harvest index (HI), are widely expected to reduce CH4 emissions with higher yield. Here we show, by combining a series of experiments, meta‐analyses and an expert survey, that the potential of CH4 mitigation from rice paddies through HI improvement is in fact small. Whereas HI improvement reduced CH4 emissions under continuously flooded (CF) irrigation, it did not affect CH4 emissions in systems with intermittent irrigation (II). We estimate that future plant breeding efforts aimed at HI improvement to the theoretical maximum value will reduce CH4 emissions in CF systems by 4.4%. However, CF systems currently make up only a small fraction of the total rice growing area (i.e., 27% of the Chinese rice paddy area). Thus, to achieve substantial CH4 mitigation from rice agriculture, alternative plant breeding strategies may be needed, along with alternative management. Breeding efforts optimizing photosynthate allocation to grains, i.e., increasing harvest index (HI), are widely expected to reduce CH4 emissions from rice cultivation. Here we show, by combining a series of experiments, meta‐analyses, and an expert assessment, that the potential of CH4 mitigation from rice paddies through HI improvement is actually small. We estimate that future HI improvement will reduce CH4 emissions in continuously flooded systems (CF) by 4.4% at most. Furthermore, HI improvement did not affect CH4 emissions in systems with intermittent irrigation (II); these systems make up a large part of the China's rice growing area and are becoming increasingly popular. [ABSTRACT FROM AUTHOR]

Breeding high-yielding rice cultivars through increasing biomass is a key strategy to meet rising global food demands. Yet, increasing rice growth can stimulate methane ( CH4) emissions, exacerbating global climate change, as rice cultivation is a major source of this powerful greenhouse gas. Here, we show in a series of experiments that high-yielding rice cultivars actually reduce CH4 emissions from typical paddy soils. Averaged across 33 rice cultivars, a biomass increase of 10% resulted in a 10.3% decrease in CH4 emissions in a soil with a high carbon (C) content. Compared to a low-yielding cultivar, a high-yielding cultivar significantly increased root porosity and the abundance of methane-consuming microorganisms, suggesting that the larger and more porous root systems of high-yielding cultivars facilitated CH4 oxidation by promoting O2 transport to soils. Our results were further supported by a meta-analysis, showing that high-yielding rice cultivars strongly decrease CH4 emissions from paddy soils with high organic C contents. Based on our results, increasing rice biomass by 10% could reduce annual CH4 emissions from Chinese rice agriculture by 7.1%. Our findings suggest that modern rice breeding strategies for high-yielding cultivars can substantially mitigate paddy CH4 emission in China and other rice growing regions. [ABSTRACT FROM AUTHOR]