Agronomic Assessment of Nitrogen Use Efficiency in Spring Wheat and Interrelations with Leaf Greenness Under Field Conditions

Four spring wheat genotypes (Triticum aestivum L.) were grown without (N0 = 0 kg N ha^?1) and under ample (N1 = 250 kg ha^?1) nitrogen (N) fertilizer in field experiments in two seasons. The aim was to assess genotypic variation in N use efficiency (NUE) components and N-related indices during grain filling thus to identify superior wheat genotypes. Leaf chlorophyll (SPAD) readings at crucial growth stages were employed to help differentiate genotypes. Interrelations between yield and N-related indices with SPAD, where also assessed to explain possible pathways of improving NUE early in the growing season. Results showed that genotypic effects on NUE were mostly evident in 2000, a year with drier preanthesis and wetter postanthesis than the normal periods. ‘Toronit’ almost always had the highest biomass yield (BY) and grain yield (GY). Except in 1999 under N0, ‘L94491? showed the highest % grain N concentration (GNC). Genotypes affected SPAD at almost all stages and N fertilization delayed leaf senescence for all genotypes and growth seasons. Correlations between SPAD at different growth stages and GY, N biomass yield at maturity (NBYM) and GNC were significant (P≤ 0.001), positive and strong/very strong (>r = 0.7). N translocation efficiency (NTE) was inversely related to PANU (~r = ? 0.77, P≤ 0.001), suggesting that N after anthesis is being preferentially transported to the ears to meet the N demand of the growing grains. It is concluded that there is still a large potential for increased NUE by improved N recirculation, use of fast and inexpensive crop N monitoring tools and high yielding, N uptake efficient genotypes.

Abbreviations: NUE, Nitrogen use efficiency; SPAD, Minolta SPAD-502 chlorophyll meter, NHI, nitrogen harvest index; HI, Harvest index; NTE, N translocation efficiency from vegetative plant parts to grain; DMTE, dry matter translocation efficiency; CPAY, contribution of pre-anthesis assimilates to yield; PANU, Post-anthesis N uptake, d.a.s., days after sowing, N0, zero (0) kg ha^?1 applied N fertilizer, N1, 250 kg ha^?1 applied N fertilizer.     

Bathymetric distribution of demersal fish in the Aegean and Ionian Seas based on generalized additive modeling

Good knowledge of the spatial distribution of fish is critical to stock assessment and successful fisheries management. Depth is often the main gradient along which faunal changes occur when analyzing shelf and upper slope assemblages, and thus knowledge of the bathymetric distribution of fish species is of great importance. The depth distribution of 16 fish species (Chelidonichthys lucernus, Helicolenus dactylopterus, Hoplostethus mediterraneus, Lepidorhombus boscii, Lophius budegassa, Merlangius merlangus, Merluccius merluccius, Micromesistius poutassou, Mullus barbatus, Mullus surmuletus, Pagellus erythrinus, Peristedion cataphractum, Phycis blennoides, Serranus cabrilla, Trigla lyra, and Trisopterus minutus) of the Aegean and the Ionian Seas was evaluated by analyzing experimental bottom trawl data, using generalized additive modeling (GAM) techniques. A variety of bathymetric distribution patterns was observed. The main bathymetric zone of each species was defined based on the modeled relative density. Specifically, the lower and upper limits of the main bathymetric zone of each species were defined as the depths where the estimated relative density of the species becomes less than 1% of the maximum. This definition is proposed as a better and more informative alternative than reporting the minimum and maximum depths of encounter.     

Economic efficiency analysis and fleet capacity assessment in Mediterranean fisheries

With fisheries resources being overexploited during the last decades, the matching of fleet capacity to resource conservation levels is urgently required. Data Envelopment Analysis was implemented to estimate and assess capacity utilization and efficiency for the first time in the eastern Mediterranean. The purse-seine fleet segments were found to operate below their capacity output level indicating the existence of overcapacity. The 24–40 m segment was evidenced to be more efficient than the 12–24 m fleet segment. Results suggested that purse-seiners could have increased their output by 89% (12–24 m) and 48% (24–40 m) providing current stock status and unrestricted access to resources. Fishing vessels may potentially improve their earnings by approximately 20% by increasing variable inputs. In data poor environments, such as the Mediterranean Sea, the simple DEA models applied in this study provide a useful approach to capacity and efficiency assessment. The quantitative measures of excess and overcapacity obtained, may contribute valuable information in balancing the productive capacity of the stock with the harvesting capacity of the fleet.     

Pyrithiobac reduces control of green foxtail (Setaria viridis) and bristly foxtail (Setaria verticillata) by propaquizafop

Experiments were conducted to evaluate potential interactions between propaquizafop and pyrithiobac applied in mixture or in sequential applications on green foxtail (Setaria viridis) and bristly foxtail (Setaria verticillata). The effect of propaquizafop application rate and the effect of ammonium sulphate were also evaluated. Propaquizafop (75–150 g ai/ha) applied alone at the five- to six-leaf growth stage provided 86–99% control of green foxtail and 92–100% control of bristly foxtail. Mixtures of propaquizafop with pyrithiobac applied at the same growth stage provided lower control of green foxtail and bristly foxtail by 27–33% and 17–22%, respectively, compared with propaquizafop applied alone. Increased rates of propaquizafop in the mixtures or the addition of ammonium sulphate did not eliminate the observed reduced control of both species with the mixture of pyrithiobac. Sequential applications where pyrithiobac was applied three days or one day before the application of propaquizafop also showed lower control of both species compared with propaquizafop applied alone. However, sequential applications where pyrithiobac was applied three days or one day after the application of propaquizafop showed more effective control of both species compared with the mixture and equal control to that achieved with propaquizafop applied alone.     

Application and fate of Cyromazine in a closed-cycle hydroponic cultivation of bean (Phaseolus vulgaris L.)

The fate of cyromazine applied via the nutrient solution (20, 40, and 60 mg of active ingredient per plant) in a closed-cycle soilless cultivation of bean with zero discharge of effluents was traced in both the recycled drainage solution and the plant tissues for 99 days. The insecticide was applied once, 15 days after planting (16 days prior to the first harvest). In addition to cyromazine, the residues of melamine, its metabolite, in the drainage solution and plant tissues were also regularly determined during the 99 days. The two higher application doses induced toxicity symptoms on the leaves of the bean plant. The maximum cyromazine levels were measured 8 days after application in the drainage solution (17-46 mg l(-1)), 16 days in the roots (1.1-2.4 mg kg(-1) fresh weight [f. wt.]) and the vegetative shoot (4.5-9.5 mg kg(-1) f. wt.), and 24 days after application in the pods (2.6-4.1 mg kg(-1) f. wt.). However, the cyromazine residues in pods were clearly below the maximum acceptable levels for bean. The half-life of cyromazine in the drainage solution ranged from 16 to 19 days for the three doses. The melamine residues in the drainage solution and in the roots reached a concentration peak 16 days after cyromazine application, whereas in the vegetative shoot and the pods they were constantly increasing over the 99 days after application. Nevertheless, the melamine residues were constantly much lower than those of cyromazine, although on the last sampling day (99) they tended toward convergence. Cyromazine proved to be highly persistent, as indicated by the remarkably high residues measured in both the drainage solution and the plant tissues, even 99 days after application. Nevertheless, the application of cyromazine via the nutrient solution to beans grown in closed-cycle hydroponic systems at doses not exceeding 20 mg per plant seems to be safe with respect to both phytotoxicity and residue levels in the edible pods.     

Synthesis of haptens and development of an immunoassay for the olive fruit fly pheromone

An enzyme-linked immunosorbent assay (ELISA) for the olive fruit fly pheromone, Bactrocera oleae Gmelin, was developed. The assay uses polyclonal antibodies, raised in rabbits, against (+/-)-beta-[3-(1,7-dioxaspiro[5.5]undecane)]propionic acid, 2 (hapten I), conjugated to the KLH (keyhole limpet hemocyanin) by the carbodiimide method. A second hapten, (+/-)-delta-[3-(1,7-dioxaspiro[5.5]undecane)]butylamine, 3 (hapten II), after conjugation to a biotin moiety, was used for indirect immobilization onto ELISA microwells precoated with the glycoprotein avidin. The developed ELISA method measures the synthetic olive fruit fly pheromone in concentrations ranging between 0.08 and 10 microg/mL and shows great promise for practical applications for pheromone detection in environmental and biological samples. The results obtained strongly indicate that this technique, to our knowledge the first insect pheromone enzyme-linked immunosorbent assay so far reported, is a fast, sensitive, inexpensive, and highly convenient method for the analysis of a volatile and low molecular weight compound such as 1,7-dioxaspiro[5.5]undecane, 1.