The genus Helicotylenchus in the grassland biome of South Africa

The genus Helicotylenchus is widespread in South Africa with 25 of the 33 Helicotylenchus species in the grassland biome. With 23 species reported from uncultivated areas, 14 species from crop plants and 10 species from the grasses grown on sports fields, Helicotylenchus is ideally suited for a study on the impact of cultivation on nematode diversity.This paper was initially delivered at the Annual Congress of the Biological Sciences Division of the South African Academy for Science and Art, ARC-Plant Protection Research Institute, Roodeplaat, Pretoria, South Africa on 01 October 2010.http://www.satnt.ac.zaam2014ab201

Identification of Thinopyrum distichum chromosomes responsible for its salt tolerance

A Thinopyrum distichuml 4× rye (Secale cereale) hybrid with genomes J1dJ2dRR was pollinated with diploid rye and mostly yielded F1 offspring with 21 chromosomes (two complete rye genomes and seven Thinopyrum chromosomes). Apparently, the closely related homoeologous chromosomes of the J1d and J2d genomes regularly formed bivalents during megasporogenesis, and egg cells mostly received a random, yet balanced set of seven Thinopyrum chromosomes. F1 plants were tested for salt tolerance and a set of fifteen highly salt-tolerant F1 plants were selected and maintained as clones for several years. These were C-banded and the Thinopyrum chromosomes contained in each were determined. By comparing segregation patterns it was now possible to group the Thinopyrum chromosomes into seven homoeologous pairs. For each of four homoeologous pairs, one of its members occurred at a higher than expected frequency, implying that these chromosomes are expressed under salt stress conditions. The results could be confirmed by backcrossing two of the most tolerant F1 plants to diploid rye. While the critical chromosomes can be identified through C-banding, an attempt was made to also find a RFLP marker for each. RFLP probes, diagnostic for the group 2, 3, 4 and 5 homoeologues of wheat, detected polymorphisms on the respective critical Thinopyrum chromosomes. However, the preliminary allocation of the critical chromosomes to homoeology groups needs to be confirmed using more and varied markers.Articl

SCAR markers that specifically tag chromosomes 2D of wheat and 2J 1d of Thinopyrum distichum

A SCAR marker for Thinopyrum distichum chromosome 2J1d (involved in salt tolerance) also amplified a slightly larger fragment in chromosome 2D of common wheat and substituted hexaploid triticale. The Thinopyrum and wheat derived fragments were isolated and used to develop two new and highly specific markers for 2J1dL and 2DL, respectively. The chromosome 2J1dL marker is useful in attempts to introgress salt tolerance into cultivated wheat and triticale whereas the 2DL marker can be used for rapid identification of hexaploid triticales with the 2D(2R) chromosome substitution.Articl

Modification of the Aegilops neglecta - Common wheat Lr62/Yr42 translocation through allosyndetic pairing induction

The Lr62/Yr42 translocation comprises mostly allen chromatin and retains only the very distal end of wheat chromosome arm 6AL, including the telomere. The large amount of foreign chromatin prohibits commercial use of the resistance and an attempt was therefore made to exchange some of the introgressed chromatin for wheat chromatin. Plants heterozygous for the translocation, but lacking the Ph1 locus were testcrossed with Chinese Spring nullisomic 6A tetrasomic 6B or nullisomic 6A tetrasomic 6D plants. Resistant (Lr62) testcross F1 progeny were evaluated for the presence of three marker loci and the data used to do a three-point genetic mapping analysis. Forty one recombinants were identified and characterised with further markers. The data revealed that Lr62/Yr42 occurs towards the distal end of 6AS and that the 6AS telomeres of the wheat and translocation chromosomes were homoeologous. While the wheat (Chinese Spring ph1b mutant) and translocated chromosomes 6A shared sufficient homoeology to allow for regular allosyndetic recombination, there were also major structural differences between them, including a duplication (marked by Xgwm334) and translocation (marked by XsopwT). The duplicated region occurred on chromosome 6A of the CS ph1b mutant and probably resulted from its inherent genomic instability. The structural differences caused irregular meiotic pairing and complex segregation data that were difficult to interpret. It was, however, possible to explain the majority of recombination products in keeping with the expected low frequency of allosyndetic recombination, and to identify the most promising recombinants. These retained both Lr62 and Yr42 within a comparatively small region of foreign DNA at the 6AS telomere.Articl

Development of SCAR markers for a Thinopyrum distichum chromosome that appears to be involved in salt tolerance

Sixty-seven F1 plants from the backcross: Thinopyrum distichuml tetraploid 'Henoch' rye// diploid 'Henoch' rye were cloned, tested for salt tolerance (2-4 replications per genotype) and ranked. Sixty RAPD primers were tested on the parental lines. Nine of these produced Thinopyrum specific fragments and were applied to the whole population. Correlations between salt tolerance and presence of the Thinopyrum specific bands were mostly significant but small, as would be expected with a trait involving genes on several chromosomes. The nine markers were then also tested on a group of 15 B1F1 plants from the same cross in which C-banding has identified the Thinopyrum chromosomes. It appeared that OPK6 (± 1060 bp) and OPK17 (± 652 bp) polymorphisms co-segregated with a chromosome putatively identified as belonging to homoeologous group 2 and implied in salt tolerance in a different study. The diagnostic RAPD bands were cloned and sequenced and specific SCAR primers were designed. These amplified DNA sequences specific for chromosome IIJ1d that will be very useful in future introgression attempts.Articl

Transfer of rust resistance genes from Triticum species to common wheat

A programme aiming to transfer leaf rust resistance genes identified in a collection of wild Triticum species was initiated in 1993. In 2000, 25 promising backcross populations were available, 19 of which bred true for resistance. Seedlings of the above lines were tested with nine leaf rust, four stem rust and two stripe rust pathotypes endemic to South Africa. A subset of five lines in which resistance (derived from T. dicoccoides, T. sharonense, T. speltoides and T. peregrinum) appeared to be integrated on wheat chromosomes and six addition lines with added chromosomes from T. kotschyi, T. peregrinum, T. umbellulatum, T. macrochaetum and T. neglectum appeared to have wide spectrum resistances, and were retained. In several instances promising stem rust and/or stripe rust resistance genes were co-transferred with leaf rust resistance. The stripe rust resistance was also effective to four Australian pathotypes and appeared to be novel. Temporary gene designations were assigned to the resistance genes in four euploid derivatives.Articl

Transfer of rust resistance genes from Triticum species to common wheat

A programme aiming to transfer leaf rust resistance genes identified in a collection of wild Triticum species was initiated in 1993. In 2000, 25 promising backcross populations were available, 19 of which bred true for resistance. Seedlings of the above lines were tested with nine leaf rust, four stem rust and two stripe rust pathotypes endemic to South Africa. A subset of five lines in which resistance (derived from T. dicoccoides, T. sharonense, T. speltoides and T. peregrinum) appeared to be integrated on wheat chromosomes and six addition lines with added chromosomes from T. kotschyi, T. peregrinum, T. umbellulatum, T. macrochaetum and T. neglectum appeared to have wide spectrum resistances, and were retained. In several instances promising stem rust and/or stripe rust resistance genes were co-transferred with leaf rust resistance. The stripe rust resistance was also effective to four Australian pathotypes and appeared to be novel. Temporary gene designations were assigned to the resistance genes in four euploid derivatives.Articl

South African National Survey of Arachnida (SANSA): review of current knowledge, constraints and future needs for documenting spider diversity (Arachnida: Araneae)

Biodiversity is one of the most important concepts in contemporary biology, with a broad range of applications. In November 1995, South Africa ratified the Convention on Biological Diversity (CBD). Signatories are obligated to develop a strategic plan for the conservation and sustainable use of biodiversity. To meet the requirements of the CBD, the South African National Survey of Arachnida (SANSA) was initiated in 1997. This national project has several aims: to document and describe the arachnid fauna of South Africa; to consolidate all the available data on South African arachnids into one relational database and to make this biodiversity information available to science; and to address issues concerning their conservation and sustainable use. Extensive sampling took place and the SANSA database contains a wealth of biodiversity data that are used to provide answers to ecological questions. Presently 71 spider families, 471 genera and 2170 species are known from South Africa, representing approximately 4.8% of the world fauna. This paper presents the current state of spider biodiversity information and how it is managed. It demonstrates the importance of running a national inventory; emphasises the significance of using a good database application; and the importance of capacity development to improve the quality and integration of biodiversity information. Further, it shows the role SANSA has played in unifying and strengthening arachnid research, with the major thrust to discover the spider diversity in South Africa. We discuss the present status of knowledge, constraints to improving this, and the future directions for research. SANSA has provided the foundations for a more integrative approach to spider diversity research. Future research should build on this legacy by linking taxonomic diversity with that of functional diversity, predicting the response of this diversity to global change drivers. Functional approaches will link these studies to ecosystem processes. Global collaborative studies at several sites following standardised sampling protocols and focused research questions would add value to the SANSA collection and the importance of spiders for the health of ecosystems.SANBI, CIB, University of Vend