Interspecific hybridisation and genome size analysis in <Emphasis Type="Italic">Buddleja</Emphasis>

Interspecific hybrids Buddleja davidii × Buddleja weyeriana, Buddleja weyeriana × Buddleja davidii and Buddleja davidii × Buddleja lindleyana were generated using in vitro embryo rescue 10–11 weeks after manual pollination. The morphological variation within the F1 populations was limited. The F1 progeny of B. davidii × B. lindleyana was almost sterile and no F2 generation was obtained. From the other hybrids, F2 generations were made by self pollinations and back crosses. Hybrid nature of all F1 and F2 seedlings was confirmed by AFLP. Chromosome counting and genome size measurement for B. weyeriana (F2 selection of (diploid) B. globosa × (tetraploid) B. davidii) revealed a higher chromosome number (76 chromosomes) and genome size than expected, indicating 2n-gametes formation occurred during meiosis of B. globosa. The F1 hybrids B. weyeriana × B. davidii (76 chromosomes) had an intermediate genome size compared with the genome size of the parent plants, proving their hybrid nature. However, the F1 and F2 hybrids of B. davidii × B. weyeriana all had 76 chromosomes but had a lower genome size than expected, suggesting the occurrence of chromosome rearrangements in the genome of the hybrids. B. lindleyana had 38 chromosomes, while the F1 hybrids of B. davidii × B. lindleyana had 76 chromosomes. Also genome size measurements revealed that the F1 seedlings B. davidii × B. lindleyana had higher genome sizes than expected. Both the results of chromosome counting and genome size measurement indicate that 2n-gametes formation took place during meiosis of B. lindleyana.     

Journeys through aroma space: a novel approach towards the selection of aroma‐enriched strawberry cultivars in breeding programmes

Consumers often criticize the sensory quality of modern strawberry cultivars. Therefore, a new and fast workflow for cultivar selection was developed to aid in the development of cultivars with enhanced aroma. This workflow consists of Headspace (HS) solid‐phase microextraction (SPME) fast GC‐MS used for high‐throughput aroma analysis of parents and hybrids. For data analysis, a chemometrical workflow was created. With a principal component analysis (PCA), the aroma similarity between the samples and a target aroma was evaluated. In order to know how the aroma profiles of the parents and hybrids are situated towards this target aroma, the Euclidean distances were calculated. These were then further used for a partial least‐squares (PLS) regression analysis to determine which aroma compounds are responsible for the observed distance to the target. By using this new approach, hybrids showing aroma profiles similar to the target aroma can be identified as most suitable candidates for further breeding cycles. Besides being time‐saving, the suggested workflow introduces aroma analysis as an integral part of breeding programmes. It prevents losing the coherence within the aroma profile and subsequently the loss of important information.     

Comment on "Global convergence in the temperature sensitivity of respiration at ecosystem level"

Mahecha et al. (Reports, 13 August 2010, p. 838) estimated the temperature sensitivity of ecosystem respiration (Q(10)) and showed that temperature sensitivity and its site-to-site variability are lower than previously reported. We demonstrate that their Q(10) value of 1.4 is an underestimate if interpreted as the averaged sensitivities of all ecosystem components, because fast temperature fluctuations penetrate poorly into the soil.     

Subset selection in plant breeding practive

Summary Selection decisions in variety testing should partly be based on statistical motives. Useful tools for this are subset selection procedures. These procedures can also be used when the performed experiment has an incomplete block design or when a series of regional trials is studied. Various selection rules serve different selection goals, but they all need so-called selection constants. Often, these constants have to be approximated by computer simulation. For this simulation, and also for the execution of the selection rules, software has been developed and is available. Some practical adjustments and modifications of subset selection in plant breeding practice are proposed. Finally, a case study of selection in sugar beet is presented.     

Mapping of Acid Deposition Effects and Calculation of Corrosion Costs on Zinc in China

Corrosion damage to materials including objects of cultural heritage due to acid deposition has been shown to cause large costs in several studies in Europe and in the United States. So far no similar extensive studies have been performed in developing countries. The World Bank has therefore initiated and financed a study of the corrosion costs in China based on available data in the literature and obtained through contacts and visits to several institutes and organisations in China. An initial assessment of the corrosion costs in China due to acidifying pollutants has been performed using a model originally developed and applied in Europe, which has been adapted to conditions in China. Here, the model is described using zinc as an example. In the calculation of corrosion costs it is assumed that the stock of materials at risk can be allocated to census data, which enables a separate calculation of the cost for each province in China. The significant differences in corrosion attack is illustrated for zinc with a corrosion map of China based on environmental data and a dose-response function adapted for Chinese conditions including the dry and wet acid deposition effects as separate terms.     

The stone and boulder content of Swedish forest soils

Stone and boulder content has a strong influence on many soil processes and is a crucial factor to take into account when estimating element pools. In this paper we present the results of a large scale inventory of the stone and boulder content of forest soils, which employed a surface penetration method (Viro's method) in 1943 plots across Sweden. The volume of stones and boulders was 43.4%, on average, although it was 47.6% for the most common soil type on glacial till parent material. The variation was spatially correlated and there were regional patterns, which were related to bedrock composition and Quaternary development. A stoniness function was developed for the upper 30 cm of the mineral soil and this was used to translate the penetration depths into stone and boulder content. The function was based on a reference data set of 200 soil pits. A relationship was found between stone and boulder content and surface boulder frequency, but the strength of the relationship varied regionally. In some regions surface boulders may provide an indicator of stone and boulder content in the soil.     

Litter impair spruce seedling emergence in beech forests: a litter manipulation experiment

European beech Fagus sylvatica and Norway spruce Picea abies are economically and ecologically important forest trees in large parts of Europe. Today, the beech forest reaches its northern distribution limit in south-eastern Norway and it is expected to expand northwards due to climate warming. This expansion will likely result in fundamental ecosystem changes. To increase our knowledge about the competitive balance between spruce and beech, we have investigated how beech and spruce litter affect spruce seedling emergence, growth and uptake of C and N. We did this in a seed-sowing experiment that included litter layer removal as well as reciprocal transplantations of litter layers between spruce and beech forests. Our results show that spruce seedling emergence was significantly impaired by both litter layer types, and especially so by the beech litter layer in the beech forest. The low seedling emergence in beech forests is concurrent with their lower light availability.     

Optimal timing of early genetic selection for sawn timber traits in <Emphasis Type="Italic">Picea abies</Emphasis>

In breeding Norway spruce, selection for improved growth and survival is performed at age 10–15 years in order to optimize genetic gain per year. We investigated whether a selection based on wood traits such as density and grain angle, measured under bark in the field at the same age would be informative enough with respect to structural quality traits of sawn boards. To achieve this objective, a sawing study was conducted on the butt logs of 401 trees from a 34-year-old Norway spruce progeny trial situated in southern Sweden. Stem discs were excised from the top of the logs and radial profile data of grain angle, and wood density was recorded for specific annual rings. The sawn and dried boards were assessed for structural traits such as twist, board density, bending stiffness (static modulus of elasticity, sMoE) and bending strength (modulus of rupture, MoR). Additive genetic correlations (r_a) between single annual ring density measurements and board density, sMoE and MoR were consistently strong (r_a>?0.7) for annual rings 5–13. Genetic correlations of similar magnitude between grain angle and board twist were estimated for all investigated annual rings (from 2 to around 26 under bark). Consequently, it was found that indirect selection for wood density and grain angle at the tree age 10–16 years would result in more genetic gain per year than selection at later ages. This makes it feasible to perform simultaneous selection of progeny in the field for both growth and wood traits at similar ages.