The aim of this review was to survey all fungal pathologists with an association with the journal Molecular Plant Pathology and ask them to nominate which fungal pathogens they would place in a 'Top 10' based on scientific/economic importance. The survey generated 495 votes from the international community, and resulted in the generation of a Top 10 fungal plant pathogen list for Molecular Plant Pathology. The Top 10 list includes, in rank order, (1) Magnaporthe oryzae; (2) Botrytis cinerea; (3) Puccinia spp.; (4) Fusarium graminearum; (5) Fusarium oxysporum; (6) Blumeria graminis; (7) Mycosphaerella graminicola; (8) Colletotrichum spp.; (9) Ustilago maydis; (10) Melampsora lini, with honourable mentions for fungi just missing out on the Top 10, including Phakopsora pachyrhizi and Rhizoctonia solani. This article presents a short resume of each fungus in the Top 10 list and its importance, with the intent of initiating discussion and debate amongst the plant mycology community, as well as laying down a bench-mark. It will be interesting to see in future years how perceptions change and what fungi will comprise any future Top 10.

/pdf/the-top-10-fungal-pathogens-in-molecular-plant-pathology-4nidxj1xqt.pdf

The Top 10 fungal pathogens in molecular plant pathology

1: Wheat Rusts and the Genetic Bases on Disease Resistance. Introduction. Biology of Pathogen and Host. Host:Pathogen Genetics. Methodologies in Wheat Rust Disease. A Coordinated Strategy for Rust Control. Conclusion. Guide to Gene Descriptions and Illustrations. 2: The Genes for Resistance to Leaf Rust in Wheat and Triticale. Catalogued Leaf Rust Resistance Genes. Temporarily Designated and Miscellaneous Leaf Rust Resistance Genes. 3: The Genes for Resistance to Stem Rust in Wheat and Triticale. Catalogued Leaf Rust Resistance Genes. Temporarily Designated and Miscellaneous Stem Rust Resistance Genes. 4: The Genes for Resistance to Stripe Rust in Wheat and Triticale. Catalogued Stripe Rust Resistance Genes. Temporarily Designated and Miscellaneous Stripe Rust Resistance Genes. References. Appendix I: Species Names Used in the Text, Genomic Formulae and Synonyms. Appendix II: Pathotypes and Accessions (Cultures) Used in Photography.

Wheat Rusts: An Atlas of Resistance Genes

Wild relatives of common wheat, Triticum aestivum, and related species are an important source of disease and pest resistance and several useful traits have been transferred from these species to wheat. C-banding and in situ hybridization analyses are powerful cytological techniques allowing the detection of alien chromatin in wheat. C-banding permits identification of the wheat and alien chromosomes involved in wheat-alien translocations, whereas genomic in situ hybridization analysis allows determination of their size and breakpoint positions. The present review summarizes the available data on wheat-alien transfers conferring resistance to diseases and pests. Ten of the 57 spontaneous and induced wheat-alien translocations were identified as whole arm translocations with the breakpoints within the centromeric regions. The majority of transfers (45) were identified as terminal translocations with distal alien segments translocated to wheat chromosome arms. Only two intercalary wheat-alien transloctions were identified, one induced by radiation treatment with a small segment of rye chromosome 6RL (H25) inserted into the long arm of wheat chromosome 4A, and the other probably induced by homoeologous recombination with a segment derived from the long arm of a group 7 Agropyron elongatum chromosome with Lr19 inserted into the long arm of 7D. The presented information should be useful for further directed chromosome engineering aimed at producing superior germplasm.

Characterization of wheat-alien translocations conferring resistance to diseases and pests: current status

/pdf/the-top-10-fungal-pathogens-in-molecular-plant-pathology-top-jklxbz8qv9.pdf

The Top 10 fungal pathogens in molecular plant pathology: Top 10 fungal pathogens

The development and use of molecular markers for the detection and exploitation of DNA polymorphism is one of the most significant developments in the field of molecular genetics. The presence of various types of molecular markers, and differences in their principles, methodologies, and applications require careful consideration in choosing one or more of such methods. No molecular markers are available yet that fulfill all requirements needed by researchers. According to the kind of study to be undertaken, one can choose among the variety of molecular techniques, each of which combines at least some desirable properties. This article provides detail review for 11 different molecular marker methods: restriction fragment length polymorphism (RFLP), random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), inter-simple sequence repeats (ISSRs), sequence characterized regions (SCARs), sequence tag sites (STSs), cleaved amplified polymorphic sequences (CAPS), microsatellites or simple sequence repeats (SSRs), expressed sequence tags (ESTs), single nucleotide polymorphisms (SNPs), and diversity arrays technology (DArT).

/pdf/an-overview-of-molecular-marker-methods-for-plants-3kkpaz7vq9.pdf

An overview of molecular marker methods for plants

Chromosome 7D of PI 294994 was indicated as carrying a single dominant gene for resistance to the Russian wheat aphid. The symbol Dn5 is proposed to designate the gene.

A monosomic analysis of Russian wheat aphid resistance in the common wheat PI 294994.

The cultivation of small grain cereals was introduced to South Africa by Dutch settlers in the 17th Century. According to historical records the first documented epidemic of wheat stem rust occurred in the south-western parts of the current Western Cape in 1726. Recurring stem and leaf rust epidemics were associated with expanding wheat production and became particularly severe in the winter-rainfall regions of the Western and Eastern Cape, as well as in the summer-rainfall regions of the Free State. The wheat stripe rust pathogen was first detected in South Africa in 1996. Due to susceptibility of cultivars at the time of this exotic introduction, stripe rust has caused significant losses in commercial wheat production over the past 10 years. Pathotype surveys of Puccinia graminis and P. triticina were initiated in the 1920s, but were discontinued until research on wheat stem rust was resumed in the 1960s. Recent evidence has shown that P. graminis f. sp. tritici continues to evolve. In addition, the annual number of wheat stem rust collections is increasing, emphasising the sustained threat of this damaging pathogen. A stem rust pathotype first detected in 2000, with newly acquired virulence for Sr8b and Sr38, currently constitutes more than 80% of all collections. Leaf and stem rust diseases also occur on barley, oat, triticale, and rye and are important production constraints in several regions. Some studies have described variability in these pathogens but long-term records of pathogenicity changes in barley and oat rust are not available. Cereal rust diseases have clearly played an important role in South African agriculture and many production regions remain favourable for rust development. Current expertise in cereal rusts covers most technologies necessary to study the respective host–pathogen systems. However, a general lack of capacity and fragmentation of research groups prevent a unified approach and remain a challenge for sustainable cereal rust control in South Africa. A national strategy for cereal rust control, with particular emphasis on pathogen and host resources, and breeding for resistance, is urgently needed.

Challenges for sustainable cereal rust control in South Africa

A stem rust resistance gene, originally derived from Triticum tauschii accession RL5289 and present in the germplasm line 87M66-2-1, is here designated Sr45. Sr45 was found to be closely linked to Sr33 (9 ± 1.9 map units) and the centromere (21 ± 3.4 map units) on chromosome arm 1DS. Sr45 is believed to be the same gene as SrX. The Russian wheat aphid resistance gene, Dn5, was loosely linked (32 ± 5 map units) to Ep-D1b, which occurs on a translocation derived from T. ventricosum, and to the cn?D1 locus (37 ± 6.3 map units) on chromosome arm 7DL. Dn5 derives from T. aestivum accession Pl294994 which was found to express two novel Ep-1 alleles (proposed designations Ep-A1d and Ep-D1e). A gene (here designated Dn7) for Russian wheat aphid resistance that was derived from the rye accession, Turkey 77', mapped 14.5 ± 3.9 map units from Lr26 on the 1BL.1RS translocation.

Association of a stem rust resistance gene (Sr45) and two Russian wheat aphid resistance genes (Dn5 and Dn7) with mapped structural loci in common wheat

An Aegilops peregrina (Hackel in J. Fraser) Maire & Weiller accession that showed resistance to mixed leaf rust (Puccinia triticina Eriks.) inoculum was crossed with, and backcrossed to, hexaploid wheat (Triticum aestivum L.). During backcrossing a chromosome segment containing a leaf rust resistance gene (here designated Lr59) was spontaneously translocated to wheat chromosome 1A. Meiotic, monosomic and microsatellite analyses suggested that the translocated segment replaced most of, or the complete, 1AL arm, and probably resulted from centromeric breaks and fusion. The translocation, of which hexaploid wheat line 0306 is the appropriate source material, provided seedling leaf rust resistance against a wide range of South African and Canadian pathotypes.

Wheat leaf rust resistance gene Lr59 derived from Aegilops peregrina

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 f...

G. F. Marais

Papers

A monosomic analysis of Russian wheat aphid resistance in the common wheat PI 294994.

Challenges for sustainable cereal rust control in South Africa

Association of a stem rust resistance gene (Sr45) and two Russian wheat aphid resistance genes (Dn5 and Dn7) with mapped structural loci in common wheat

Wheat leaf rust resistance gene Lr59 derived from Aegilops peregrina

Transfer of rust resistance genes from Triticum species to common wheat