Dense Stellar Populations: Initial Conditions

This chapter is based on four lectures given at the Cambridge N-body school "Cambody". The material covered includes the IMF, the 6D structure of dense clusters, residual gas expulsion and the initial binary population. It is aimed at those needing to initialise stellar populations for a variety of purposes (N-body experiments, stellar population synthesis).Comment: 85 pages. To appear in The Cambridge N-body Lectures, Sverre Aarseth, Christopher Tout, Rosemary Mardling (eds), Lecture Notes in Physics Series, Springer Verla

A genetic analysis of aluminium tolerance in cereals

Aluminium (Al) toxicity is a major threat to agricultural production world wide wherever acid soil exists. Wheat and barley, the major food and feed crops, are severely affected and this necessitates investigations that could help to improve the yield by utilising the available genetic diversity for Al tolerance with the aid of several molecular platforms. We investigated the quantitative trait loci (QTL) conferring tolerance to Al toxicity in three different mapping populations of wheat and barley.Using a set of D genome (Ae. tauschii) introgression lines, a major Al tolerance locus was assigned to chromosome arm 4DL, explaining 31% of the phenotypic variation displayed by the population. A second major QTL was mapped to chromosome arm 3BL using a set of doubled haploid progeny lines. This major QTL, QaltCS.ipk-3B, originated from ‘Chinese Spring’ accounted for 49% of the variation in the population. The inheritance for Al tolerance in barley was dissected based on a genetic map constructed with genic markers. QTLs were identified on chromosomes 2H, 3H and 4H. A sequence homology search was used to derive the putative function of the genes linked to the QTL, in order to identify potential candidate genes for Al tolerance. Some of these candidates are implicated in stress/defence responses, in particular, stress signal transduction, transcription regulation factors and cell metabolism

Molecular tools for genebank management and evaluation

Molecular markers were developed for many species and enabled us to use them for the characterisation of genebank collections. We used the marker technology (microsatellites) for studying the genetic integrity of the self pollinating species wheat (Triticum aestivum L.) and the open pollinating species rye (Secale cereale L.). The study became possible, because at IPK both the ex situ collection, consisting of seeds from the most recent regeneration and a herbarium collection is maintained. In the herbarium collection from each accession samples of grains and complete spikes are deposited as vouchers when they are grown initially. For the wheat accessions investigated the comparison of the DNA fingerprints showed a high degree of idendity. No contamination due to foreign pollen or incorrect handling during the multiplication cycles was discovered. For the open pollinating species rye, however, major changes in allele frequencies were detected. Overall, nearly 50% of the alleles discovered in the original sample were not found in the material present in the ex situ collection now. In some cases alleles were detected in the most recently propagated subpopulations that were not observed in the investigated plants of the original one. In addition to the integrity studies we are in process of utilizing molecular markers for a marker assisted screening of genebank collections. Salt tolerance of barley has been shown as a case study in the present article