No abstract

Maize (Zea mays L.) is particularly sensitive to chilling in the early growth stages. The objective of this study was to determine quantitative trait loci (QTL) for early plant vigour of maize grown under cool and moderately warm conditions in Central Europe. A population of 720 doubled haploid (DH) lines was derived from a cross between two dent inbred lines contrasting in early vigour and were genotyped with 188 SSR markers. The DH lines per se and their testcrosses with a flint line were evaluated in field experiments across 11 environments in 2001 and 2002. Plants were harvested after six to eight leaves had been fully developed to assess fresh matter yield as a criterion of early vigour. Seven QTL were detected for line performance and ten QTL for testcross performance, explaining 64 and 49% of the genetic variance. Six out of seven QTL detected in the lines per se were also significant in their testcrosses. Significant QTL x environment interaction was observed, but no relationship existed between the size of the QTL effects and the mean temperature in the individual environment. The correlation between fresh matter yield and days to silking was non-significant, indicating that differences in early plant vigour were not simply caused by maturity differences. For three additional chilling-related traits, leaf chlorosis, leaf purpling, and frost damage seven, six, and five QTL were detected, respectively. Three QTL for leaf chlorosis, two for leaf purpling, and two for frost damage co-localized with QTL for fresh matter yield. Results are considered as a reliable basis for further genetic, molecular, and physiological investigations.

No abstract

Genetic variation among Armillaria ostoyae isolates was studied by rDNA-restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) analysis. A total of 20 A. ostoyae isolates, mainly obtained from Picea spp. of different geographical origins, were examined. Southern hybridization of whole-cell DNAs digested with Avail and probed with biotin-labelled cloned rDNA from Saccharomyces carlsbergensis allowed the differentiation of five RFLP groups. UPGMA cluster analysis of RAPD profiles (138 scorable bands) generated by 10 decamer primers (OPA 01-OPA 10) grouped the isolates in subclusters at similarity levels between 40% and 96%, indicating high intraspecific genetic variability. Some isolates of different geographical origins subgrouped together, suggesting that similar mutational events have occurred independently and that genetic exchange and recombination occurs among the DNAs in natural populations. The potential role of historical and current spread of spruce plants on the genetic variation of A. ostoyae isolates in Europe is discussed. Using the primer pair ARM-1 and ARM-2, an Armillaria-s^eci^c ITS-DNA fragment of about 660 bp was obtained. No intraspecific RFLP of this amplicon could be revealed, indicating low genetic variability of this region.The established informative RFLP and RAPD markers and also the Armillaria-specific ITS-DNA fragment may be powerful tools for further epidemiological, phylogenetic and host-pathogen interaction studies with A. ostoyae.

Fusarium moniliforme Sheldon (syn. F. verticillioides (Sacc.) Nirenberg) and F. subglutinans (Wollenweber & Reinking) Nelson Toussoun & Marasas comb. nov., two anamorphs of the so‐called‘Gibberella fujikuroi species complex', are important maize pathogens. Together with F. proliferatum, F. culmorum, and F. graminearum (teleomorph: Gibberella zeae) they are involved in the stalk rot and ear rot disease of maize. All species produce secondary metabolites (mycotoxins) which are a potential health hazard for humans and animals that consume maize and maize products frequently. In this study the development of polymerase chain reaction (PCR) assays for an easy and sensitive identification of G. fujikuroi anamorphs in maize kernels are described. The primer pairs are based on sequences of randomly amplified polymorphic DNA (RAPD) fragments and are specific for F. moniliforme and F. subglutinans respectively. The PCR assays are independent of the high phenotypic variability of traits which may complicate classification by morphological characters. They detect approximately 100 to 200 fungal genomes in the presence of an excess of maize DNA. For the analysis of infected maize kernels a rapid and easy DNA extraction was used which does not introduce inhibitory substances into the PCR. Hence the assays enable an early identification and detection of the two pathogens in host tissue by plant breeders and plant health inspection services. The assays were successfully applied to identify field isolates from Poland and to detect the pathogens in maize ears of various hybrids in Germany.