Efficient selection of potato heterokaryons by flow cytometric sorting and the regeneration of hybrid plants

Drought is one of the important factors limiting crop production in arid and semi-arid regions. Four drought resistance criteria, consisting of canopy temperature, stomatal resistance, transpiring area and rate of water loss by excised-leaves were examined in two experiments conducted in optimum and stress moisture conditions in 1995. A randomized complete block design with four replications and six genotypes was used for each experiment. Under optimum moisture conditions, there was a significant difference in canopy temperature at midday between drought resistant and drought sensitive genotypes. A significant linear relationship was also obtained between this criterion and yield reduction ratio as determined by Y_r = 1-(Y_s/Y_p) (Y_s and Y_p = yield under stress and non-stress conditions, respectively), at the ear emergence stage. The only significant difference between cultivars in respect to stomatal resistance in stress conditions was that of adaxial leaf surface in ear emergence stage. No significant linear relationship was obtained between transpiring area and yield reduction ratio. Cultivars differed in respect to rate of water loss (RWL) and initial water content (IWC) in ear emergence and grain filling in stress environment only. Ultimately, three criteria namely canopy temperature, stomatal resistance and RWL, in explicated conditions were recognized as benificial drought resistance indicators. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spent brewer's yeast as a replacement for fishmeal in diets for giant freshwater prawn (Macrobrachium rosenbergii), reared in either clear water or a biofloc environment

A 90‐day feeding experiment was conducted in order to test spent brewer's yeast as a replacement for fishmeal in diets for giant freshwater prawn (Macrobrachium rosenbergii) reared in either a recirculating aquaculture system (RAS) or a biofloc system. Triplicate groups, each of 20 prawn (6.7 ± 0.03 g), were randomly assigned to 24 identical tanks. Twelve tanks were connected to the RAS, and the other 12 tanks were connected to the biofloc system which were initially supplemented with Bacillus subtilis, molasses and blood meal to achieve a C:N ratio of 20:1. Four iso‐nitrogenous (350 g/kg) and iso‐energetic (19 MJ/kg) diets where 0%, 20%, 40% and 60% of fishmeal protein was replaced by spent brewer's yeast. Neither growth nor survival was affected (p > 0.05) by increasing levels of brewer's yeast. The exception, being fish given 60% replacement with brewer's yeast, reared in biofloc, which displayed a higher (p < 0.05) growth than fish given 40% replacement, reared in clear water. The feed conversion ratio of prawn reared in the biofloc environment was lower than in the clear water. We concluded that spent brewer's yeast represents a possible 60% substitute for fishmeal in giant freshwater prawn diets, especially for prawn reared in a biofloc environment.     

No negative sublethal effects of two insecticides on prey capture and development of a spider

Laboratory experiments were used to analyse the effect of two insecticides, dimethoate and cypermethrin, on prey capture, feeding and rate of development of the wolf spider Pardosa amentata. Though partly lethal doses (LD₅₀ and LD₁₀) were applied and a high proportion of surviving spiders suffered paralysis for one to two days, which could be fatal under field conditions, no negative effects on other investigated biological characteristics (including development and predation rates) of the surviving individuals were observed. With very low doses of cypermethrin, killing rate and feeding of females in the period between the final moult and egg-sac deposition were increased compared to untreated controls. This is the first evidence of enhanced performance due to an insecticide in a spider. The possibility of insecticide stimulation of predator population recovery after eradication by spraying is discussed. © 1998 SCI.     

Interactive Effects of Different Temperatures and Salinities on Growth,Feed Conversion Efficiency,and Blood Physiology in Juvenile Spotted Wolffish,Anarhichas minor Olafsen

The aim of this study was to investigate the effects of different salinities and temperatures and their possible interactive effect on growth performance, feeding parameters, and blood physiology in juvenile spotted wolffish, Anarhichas minor, reared at different temperature (7 and 10 C) and salinity (15, 25, and 34‰) combinations. There was a significant interactive effect between temperature and salinity on growth, as a growth‐enhancing effect was seen at intermediate and full salinities at higher temperature, whereas the reciprocal trend was seen at lower temperature. Mean total feed consumption, daily feeding rate, and feed conversion efficiency were all highest at the intermediate salinity at 10 C, whereas at 7 C, the feeding parameters were highest at low and intermediate salinities. Blood plasma sodium content was lowest at 15‰, whereas the opposite trend was seen in partial pressure of CO₂ and bicarbonate in blood where the highest concentrations were seen at 15‰. This study demonstrates that spotted wolffish has a high osmoregulatory and acclimatory capacity. In an aquaculture context, growth of juvenile spotted wolffish can be improved by rearing the species at high temperature and intermediate salinity combinations at least in a limited period of the juvenile phase.     

Some visual aspects of planting design and silviculture across contemporary forest management paradigms – Perspectives for urban afforestation

There is a pan-European interest in increasing the amount of woodland cover, particularly in areas close to urban populations. However, in the enthusiasm for planting trees, is enough forethought given to visual aspects of woodland stand interiors? This paper conceptualises and assesses visual aspects of planting designs and silvicultural principles across three contemporary forest management paradigms: the commercial, the nature-based, and the urban paradigm. Planting design models and silvicultural treatments were conceptualised from a review combined with case studies. Using profile diagrams, we made visual representations of planting design and stand development, as basis for ‘expert’ assessment of four visual criteria: scale, diversity, naturalness and visual accessibility. The assessment was done for the young stage (0–25 years) and the mature stage (50–90 years) separately, using a qualitative three-step scale: limited, medium, and extended. Seven different planting design models were identified. Three of these originate from the urban paradigm: the seed source model, the density gradient model, and the habitat model. Another three originate from the nature-based paradigm: the natural succession model, the nature-based shortcut model, and the direct approach model. Only one model originates from the commercial paradigm: the monoculture model. The assessment showed that visual aspects vary considerably between planting designs and silvicultural systems. The monoculture model offers the splendour of the mature pillar hall with free views and movements, however, necessitating an obvious plantation stage in its youth. In contrast, models utilising succession and variation in species, age and tree spacing offers an extended experience of diversity and naturalness – even in the young stages. These visual qualities are discussed in relation to future perspectives for urban afforestation across urban woodland zones.     

Genetic selection indices for Swedish trotter broodmaresIndex de sélection pour les juments de trotteur suédoisGenetische selektionsindices für schwedische traber-zuchtstuten

Studbook performance records for 2734 Swedish standardbred trotter broodmares have been analysed. Transformation of most variables was necessary in order to approach normality of the records. The heritability for the traits varied between 0.10 and 0.68, the lowest value for transformed “number of starts” and highest for transformed “earnings per start”. Genetic correlations were very high or high between all traits except for transformed “number of starts”. Transformed “earnings” was found to be genetically almost identical with transformed “best life-time racing time”, but more suitable for selection purposes. Several selection indices were constructed and their use in mass-selection and for adjusting for non-random distribution of dam genotypes when progeny-testing stallions is discussed.