In China, the abuse of chemical nitrogen (N) fertilizer results in decreasing N use efficiency (NUE), wasting resources and causing serious environmental problems.  Cereal-legume intercropping is widely used to enhance crop yield and improve resource use efficiency, especially in Southwest China.  To optimize N utilization and increase grain yield, we conducted a two-year field experiment with single-factor randomized block designs of a maize-soybean intercropping system (IMS).  Three N rates, NN (no nitrogen application), LN (lower N application: 270 kg N ha^–1), and CN (conventional N application: 330 kg N ha^–1), and three topdressing distances of LN (LND), e.g., 15 cm (LND1), 30 cm (LND2) and 45 cm (LND3) from maize rows were evaluated.  At the beginning seed stage (R5), the leghemoglobin content and nitrogenase activity of LND3 were 1.86 mg plant^–1 and 0.14 mL h^–1 plant^–1, and those of LND1 and LND2 were increased by 31.4 and 24.5%, 6.4 and 32.9% compared with LND3, respectively.  The ureide content and N accumulation of soybean organs in LND1 and LND2 were higher than those of LND3.  The N uptake, NUE and N agronomy efficiency (NAE) of IMS under CN were 308.3 kg ha^–1, 28.5%, and 5.7 kg grain kg^–1 N, respectively; however, those of LN were significantly increased by 12.4, 72.5, and 51.6% compared with CN, respectively.  The total yield in LND1 and LND2 was increased by 12.3 and 8.3% compared with CN, respectively.  Those results suggested that LN with distances of 15–30 cm from the topdressing strip to the maize row was optimal in maize-soybean intercropping.  Lower N input with an optimized fertilization location for IMS increased N fixation and N use efficiency without decreasing grain yield.

Botryosphaeriaceae species are important causal agents of blueberry stem blight worldwide. Blueberry stem blight has become an important disease, potentially affecting the quality and production of blueberries in China. It is difficult and time-consuming to identify at the species level using morphological methods. The aim of this study was to develop polymerase chain reaction (PCR) assays for the diagnosis and early detection of latent infections of blueberry stems by Botryosphaeria spp. Species-specific primers, based on the ribosomal DNA internal transcribed spacer region and β-tubulin gene, were designed and selected for use in PCR assays. Three primer pairs, Lt347-F/R for Lasiodiplodia theobromae, Np304-F/R for Neofusicoccum parvum and FaF/Bt2b for Botryosphaeria dothidea, successfully amplified specific PCR fragments of different sizes on pure cultures or from blueberry stems inoculated and naturally infected blueberry plants with three pathogens, respectively. These primers did not amplify any PCR fragments from other blueberry stem disease-associated pathogens, such as Phomopsis spp. and Pestalotiopsis spp. This PCR protocol could detect as low as 100 pg to 1 ng of purified fungal DNA. This PCR-based protocol could be used for the diagnosis and detection of these pathogens from pure cultures or from infected blueberry plants.

Mung bean (Vigna radiata L.) has the potential to establish symbiosis with rhizobia, and symbiotic association of soil micro flora may facilitate the photosynthesis and plant growth response to elevated [CO2]. Mung bean was grown at either ambient CO2 400 μmol mol–1 or [CO2] ((550±17) μmol mol–1) under free air carbon dioxide enrichment (FACE) experimental facility in North China. Elevated [CO2] increased net photosynthetic rate (Pn), water use efficiency (WUE) and the non-photochemical quenching (NPQ) of upper most fully-expanded leaves, but decreased stomatal conductance (Gs), intrinsic efficiency of PSII (Fv´/Fm´), quantum yield of PSII (ΦPSII) and proportion of open PSII reaction centers (qP). At elevated [CO2], the decrease of Fv´/Fm´, ΦPSII, qP at the bloom stage were smaller than that at the pod stage. On the other hand, Pn was increased at elevated [CO2] by 18.7 and 7.4% at full bloom (R2) and pod maturity stages (R4), respectively. From these findings, we concluded that as a legume despite greater nutrient supply to the carbon assimilation at elevated [CO2], photosynthetic capacity of mung bean was still suppressed under elevated [CO2] particularly at pod maturity stage but plant biomass and yield was increased by 11.6 and 14.2%, respectively. Further, these findings suggest that even under higher nutrient acquisition systems such as legumes, nutrient assimilation does not match carbon assimilation under elevated [CO2] and leads photosynthesis down-regulation to elevated [CO2].