Sequencing the Major Mycosphaerella Pathogens of Wheat and Banana

Mycosphaerella is one of the largest genera of plant-pathogenic fungi with more than 1,000 named species, many of which are important pathogens causing leaf spotting diseases in a wide variety of crops including cereals, citrus, banana, eucalypts, soft fruits and horticultural crops. A few species of Mycosphaerella cause disease in humans and other vertebrates. An international project was initiated to sequence the genomes of M. graminicola and M. fijiensis, two of the most economically important pathogens of wheat and banana, respectively, along with 40,000 ESTs from M. fijiensis and the related maize pathogen Cercospora zeae-maydis. The 9x M. graminicola genome size is 39.8 Mb with chromosome sizes from 548 kb to 6 Mb and a complete circular mitochondrial genome of 43,947 bp. Our data indicate that M. graminicola has both the largest chromosome number and the smallest chromosome sizes recorded among filamentous ascomycetes. The Mycosphaerella Genomics Consortium, which was established in 2003, decided to use M. graminicola as the model to develop more genetic and genomic research on M. fijiensis. Since 2003, M. fijiensis EST sequencing has resulted in more than 30,000 ESTs, and the genome sequencing was recently finished at 7.8x. The genome size of M. fijiensis is 80% larger than that of M. graminicola. The completed mitochondrial sequence is more then twice as large, and the estimated nuclear genome size is approximately 72 Mb. The extension of the genome size of M. fijiensis seems to be mostly due to additional repeated sequences. The status of Mycosphaerella sequencing will have a significant effect on future studies aimed at the control of black leaf streak disease. The current status of both sequencing projects and other initiatives to exploit this information and to put it into a multidisciplinary approach focusing on sustainable management of the disease will be discusse

Het graanziekteonderzoek in Nederland: kaalslag in de polder (2)

Geschiedenis, verworvenheden en bedreiging van het nationale graanziekteonderzoek (roest in tarwe) in Nederland. Rubrieken in dit artikel: 1) Resistentieonderzoek; 2) Certificering en inputreductie; 3) Ziekteninventarisatie. Gegevens in bijgaande tabel: Incidentie van diverse graanziekten in Nederland (periode 1981-1983, 1994-2001

Mycosphaerella graminicola on wheat : genetic variation and histopathology

The research described in this thesis was focused on a comprehensive understanding of the generation and extent of genetic variation, and its effects on host cultivars in the wheat- Mycosphaerella graminicola pathosystem. Inoculation experiments were conducted in the seedling stage and adult plant stages under field conditions over several years. These experiments encompassed nearly 100 isolates of the pathogen tested on some 50 wheat cultivars. Parametric and non-parametric statistical analyses were employed on large data and very small data sets, and indicated that in all experiments cultivar x isolate interactions were significant. Pathogen isolates originating from bread wheat and durum wheat appeared to be adapted to their hosts, respectively. Molecular analysis of the interternally transcribed spacer regions of isolates from both forms, indicated that these were taxonomically closely related. The inoculation experiments indicated that specificity is an important characteristic of the pathosystem. After having determined the wide genetic variation in the pathosystem, experiments were conducted to elucidate the mating system of the pathogen. The results indicated a bipolar heterothallic mating system and RAPD analyses of progenies showed regular Mendelian inheritance. Furthermore it was shown that the pathogen is able to complete several generative cycles within a season. Hence, genetic recombination appears to be the driving force behind the determined vast genetic variation. Biochemical and histological experiments were conducted involving compatible and incompatible interactions with the host plant in order to elucidate the resistance mechanism of wheat to the pathogen

Identification of a new resistance gene to septoria tritici blotch in wheat

Door het screenen van lijnen en wilde verwanten van tarwe, is een nieuw resistentiegen tegen STB (Septoria tritici blotch) gevonden

Outstanding : the dispensable chromosomes of Mycosphaerella graminicola

Bijdrage aan de KNPV-voorjaarsvergaderin

A molecular diagnostic for tropical race 4 of the banana

This study analysed genomic variation of the translation elongation factor 1 (TEF-1) and the intergenic spacer region (IGS) of the nuclear ribosomal operon of Fusarium oxysporum f. sp. cubense (Foc) isolates, from different banana production areas, representing strains within the known races, comprising 20 vegetative compatibility groups

Agrobacterium-mediated transformation of Mycosphaerella fijiensis, the devastating Black Sigatoka pathogen of bananas

Mycosphaerella fijiensis, M. musicola en M. eumusae veroorzaken de Sigatoka-ziekte in banaan. Op dit moment is de toepassing van fungiciden de enige optie om deze ziekte te bestrijden. Het PRPB (Pesticide Reduction Program for Banana) investeert in de ontwikkeling van technieken voor de genotype- en fenotypebepaling van M. fijiensis. Hierbij wordt gebruikt gemaakt van ATMT (Agrobacterium tumefaciens-mediated transformation)

A Detection Method for Tropical Race 4 of the Banana Pathogen Fusarium oxysporum f. sp. cubense

Fusarium oxysporum f. sp. cubense (Foc) is the causal agent of Fusarium wilt, the devastating disease that ruined the ‘Gros Michel’ (AAA)-based banana production in the first half of the 20th century. The occurrence of a new variant in Southeast Asia that overcomes the resistance in Cavendish clones such as ‘Grand Naine’ (AAA) is a major concern to current banana production worldwide. The threat posed by this new variant, called tropical race 4 (TR4), may be overcome by the introduction of resistant cultivars. However, the identification of new resistant sources or breeding for resistance is a long-term effort. Currently, the only option to control the disease is to avoid or reduce the spread of the pathogen by eradication of infected plants and isolation of infested plantations. This requires sensitive and highly specific diagnostics that enable early detection of the pathogen. A two-locus database of DNA sequences, from over 800 different isolates from multiple formae speciales of F. oxysporum, was used to develop a molecular diagnostic tool that specifically detects isolates from the vegetative compatibility group (VCG) 01213, which encompasses the Foc TR4 genotype. This diagnostic tool was able to detect all Foc TR4 isolates tested, while none of the Foc isolates from 19 VCGs other than 01213 showed any reaction. In addition, the developed diagnostic tool was able to detect Foc TR4 when using DNA samples from different tissues of ‘Grand Naine’ plants inoculated with TR4 isolate

Identification and Validation of EST-Derived Molecular Markers, TRAP and VNTRs, for Banana Research

The advent of high-throughput sequencing technology has generated abundant information on DNA sequences for the genomes of many plant species. Expressed Sequence Tags (ESTs), which are unique DNA sequences derived from a cDNA library and therefore representing genes transcribed in specific tissues or at some stage of development, are one type of DNA sequences highly available today for many important crop species. Molecular markers are used for bridging DNA sequence information with particular phenotypes and are useful tools for genotyping germplasm collections and also for tagging genes involved in desirable agronomic traits. In this sense, there is always a strong demand for suitable marker techniques to better utilise existing sequence information. A transcriptome database from banana (Musa spp.), DATAMusa, containing 42,724 ESTs from 11 different cDNA libraries and encompassing approximately 24 Mb of DNA sequence, was used in this study for the design of primers to PCR-amplify two types of EST-derived molecular markers, Variable Nucleotide Tandem Repeat (VNTR) and Target Region Amplification Polymorphism (TRAP). These primers were then validated against a panel of 14 diploid Musa genotypes and produced 32 (VNTR) and 119 (TRAP) alleles. Used separately or together, both types of markers were able to discriminate Musa genotypes from different genome background (A or B genomes). The TRAP alleles identified were derived from only one EST, while the VNTR alleles were derived from 12 unigenes. Based on the results of this study, EST-derived markers can be an important source of polymorphism to be used in genetic diversity and gene discovery studies in banan