基因工程菌枯草芽孢杆菌GEB3产生的脂肽类抗生素及其生物活性研究

 利用MALDI TOF MS技术 ,鉴定了将lpaB3基因转入枯草芽孢杆菌Bacillussubtilis 168菌株所构建的工程菌GEB3产生的脂肽类抗生素种类。结果表明 ,GEB3仅产生表面活性素 (surfactin) 1种脂肽类抗生素。经LC MS分析 ,GEB3产生由 13、14和 15个碳原子的脂肪酸链构成的标准表面活性素变异体 (standardsurfactinisoforms)。生物活性检测表明 ,该工程菌产生的脂肽类抗生素表面活性素具有抑制小麦纹枯病菌和稻瘟病菌菌丝生长的作用     

QTL mapping of improving forage maize starch degradability in European elite maize germplasm

Improving maize starch content is of great importance for both forage and grain yield. In this study, 13 starch degradability traits were analysed including percentage of the seedling area, floury endosperm, hard endosperm of total grain area, percentage of the floury endosperm surface and vitreousness ratio surface hard: floury endosperm surface, etc. We mapped quantitative trait loci (QTL) in a biparental population of 309 doubled haploid lines based on field phenotyping at two locations. A genetic linkage map was constructed using 168 SSR (simple sequence repeat) markers, which covered 1508 cM of the maize genome, with an average distance of 9.0 cM. Close phenotypic and genotypic correlations were found for all traits, and were all statistically significant (p = 0.01) at two locations. Major QTL for more than two traits were detected, especially in two regions in bins 4.05–4.06 and 7.04–7.05, associated with 13 and 9 traits, respectively. This study contributes to marker‐assisted breeding and also to fine mapping candidate genes associated with maize starch degradability.     

Seed flavonoids and anthocyanins as markers of enhanced plant defence in nodulated cowpea (Vigna unguiculata L. Walp.)

Insect pests are a major constraint to cowpea production in Africa. Therefore the aim of this study was to identify cowpea material that exhibit greater pest resistance and grain yield for evaluation by farmers. About 45 cowpea genotypes were assayed for flavonoids and anthocyanins with the objective of quantifying the levels of these phenolics in seed extracts as markers for effective plant defence. The results revealed significant differences in the concentration of flavonoids and anthocyanins in seed extract. Farmer varieties such as Sanzie, Bensogla and Omondaw exhibited much higher levels of phenolics compared with improved genotypes like ITH98-46, TVu1509 and IT93K-452-1. When planted in the field in Ghana and Tanzania, the genotypes that had high concentrations of flavonoids and anthocyanins in seed extracts (e.g. Bensogla, Omondaw and IT86D-2075) showed relatively lower infestation by thrips, pod-sucking bugs, aphids and alcidodes. Providing minimum protection with insecticide spray further showed that, genotypes with low infestation by thrips and pod-sucking bugs produced more grain yield without spraying, an indication of their natural resistance to these insect pests. Furthermore, farmer-selected varieties such as Sanzie, Bensogla, and Omondaw produced more grain yield without protection than their improved counterparts. These results showed that the higher the concentration of flavonoids and anthocyanins in cowpea seed extracts, the lower the insect pest incidence on seedlings raised from those seeds. Correlation analysis further confirmed a direct relationship between high flavonoids/anthocyanins in seed extracts and enhanced insect pest.     

Broomrape management in faba bean

Broomrapes (Orobanche spp. and Phelipanche spp.) are weedy root parasites that represent a major constraint for faba bean (Vicia faba) cultivation in the Mediterranean area. Control methods are being developed that comprise techniques ranging from agronomical practices to precision farming, including chemical and biological control, genetic and induced resistance, modelling, and probably nanotechnology in a nearby future. However, the main concern is that to date, no single method of control provides complete protection against these parasites. For that reason, an integrated approach is needed in which a variety of such techniques are combined, in order to maintain parasite populations below threshold levels of damage.     

Use of thermography for high throughput phenotyping of tropical maize adaptation in water stress

In this study the suitability of thermal imaging for phenotyping was investigated as part of a breeding experiment carried out by the International Maize and Wheat Improvement Centre (CIMMYT) at Tlaltizapán experimental station in Mexico. Different subtropical maize genotypes with two replications were screened with respect to their tolerance to water stress. Thermal images of the canopy of 92 different maize genotypes were acquired on two different days in the time interval between anthesis and blister stages (grain filling 1), whereby each picture contained five plots of different genotypes and canopy temperatures calculated for each plot. Significantly, lower canopy temperatures were found in well-watered genotypes compared with water-stressed genotypes. Furthermore significant differences (p < 0.001) between genotypes under water stress were detected using thermal images. A close correlation (p < 0.01–0.001) between canopy temperature or modified Crop water stress index with NDVI and SPAD values was obtained. It may be concluded that genotypes better adapted to drought conditions exhibited lower temperatures.Thermography is a potentially promising method to accelerate the screening process and thereby enhance phenotyping for drought adaptation in maize.     

Nano-mechanical transduction of polymer micro-cantilevers to detect bio-molecular interactions

Using variothermal polymer micro-injection molding, disposable arrays of eight polymer micro-cantilevers each 500 μm long, 100 μm wide and 25 μm thick were fabricated. The present study took advantage of an easy flow grade polypropylene. After gold coating for optical read-out and asymmetrical sensitization, the arrays were introduced into the Cantisens(?) Research system to perform mechanical and functional testing. We demonstrate that polypropylene cantilevers can be used as biosensors for medical purposes in the same manner as the established silicon ones to detect single-stranded DNA sequences and metal ions in real-time. A differential signal of 7 nm was detected for the hybridization of 1 μM complementary DNA sequences. For 100 nM copper ions the differential signal was found to be (36 ± 5) nm. Nano-mechanical sensing of medically relevant, nanometer-size species is essential for fast and efficient diagnosis.     

Adapting the pair-correlation function for analysing the spatial distribution of canopy gaps

Forestry around the world has been experiencing a paradigm shift towards more nature-oriented forest management leading foresters to emulate natural disturbances by their silvicultural treatments. Important characteristics of all disturbances are their size, severity, temporal and spatial distribution. This study focuses on the spatial distribution of gaps in the forest canopy which are typically caused by small-scale, low intensity disturbances.     

A comparison of different 15N application techniques to study the N net rhizodeposition in the plant‐soil system

The suitability of three ¹⁵N application methods (¹⁵NH₃ fumigation, split‐root technique, ¹⁵N pre‐cultivation) for the estimation of N net rhizodeposition (NRD) of wheat plants into soil has been tested and compared under similar conditions and at the same developmental stage. The results were as follows: 1. The use of the ¹⁵N tracer technique allows the detection of the net N release by roots under soil conditions. NRD was considerable and can be estimated to be at least 15 kg N ha⁻¹ a⁻¹. 2. All three methods applied are practicable under non‐sterile experimental conditions. The distribution of applied ¹⁵N in the system and NRD can be balanced totally only by using the ¹⁵NH₃ fumigation and the ¹⁵N pre‐cultivation methods. The split‐root technique leads to an overestimation of NRD. 3. The split‐root technique allows a qualitative separation of the NRD under nearly undisturbed conditions. With the ¹⁵N precultivation, a higher ¹⁵N‐labelling can be achieved for long‐term balance studies. 4. Despite the required high ¹⁵N abundance, the ¹⁵NH₃ fumigation method works best to evaluate the influence of microbes on NRD and to quantify the gaseous ¹⁵N release.     

Release of carbon and nitrogen compounds by plant roots and their possible ecological importance+

The root-borne C- and N-flux in the plant/soil system was studied by determining the ¹⁴C- or ¹⁵N-balances in pot trials with soil as a substrate (¹⁴CO₂- or ¹⁵NH₃-application to the shoots, comparison of sterile and nonsterile treatments for quantification of root-borne substances). The following results were obtained: 1. The amount of (primary) root-borne carbon compounds released into soil was (besides root respiration) 11—20% of net-CO₂-assimilation or 13—32% of the ¹⁴C incorporated into the plants (= 1 t C · ha^—1). 5—6% of ¹⁵N assimilated by the plants were released as root-borne N compounds (= 15 kg N · ha^—1). 2. A considerable portion of the root-borne C (about 6% = 600 kg C · ha^—1) was found in the rooted soil zone at the end of the experiments (rhizodeposition). 3. (Primary) root-borne C and N compounds found in immediate vicinity of the roots (about 60—80%) were mainly water soluble, whereas most of the C and N compounds found in a greater distance were water insoluble. The water soluble exudates consisted mainly of neutral (carbohydrates) and acid fractions (organic acids). The basic fraction (amino acids) made up a small portion only. 4. The root-borne C and N compounds influenced the nutrient balance of soil and plant directly and/or indirectly via microbes (depending on species, variety and nutritional status of plants). 5. Microbes stimulated the release of C- and N-compounds, but rapidly respired 65—85% of the root-borne C-compounds, thereby putting a burden on the C-budget of the “host” plant. 6. It could be shown by the example of hup⁺ Rhizobium meliloti strains (tested by ³H₂-incorporation) and the wheat-Serratia-association, that energy efficient microbenplant systems can improve plant performance.