SUMMARY
Alternaria species are mainly saprophytic fungi However, some species have acquired pathogenic capacities collectively causing disease over a broad host range This review summarizes the knowledge on pathogenic strategies employed by the fungus to plunder the host Furthermore, strategies employed by potential host plants in order to ward off an attack are discussed

Taxonomy:Alternaria spp kingdom Fungi, subkingdom Eumycotera, phylum Fungi Imperfecti (a non-phylogenetic or artificial phylum of fungi without known sexual stages whose members may or may not be related; taxonomy does not reflect relationships), form class Hypomycetes, Form order Moniliales, form family Dematiaceae, genus Alternaria Some species of Alternaria are the asexual anamorph of the ascomycete Pleospora while others are speculated to be anamorphs of Leptosphaeria

Host Range: Most Alternaria species are common saprophytes that derive energy as a result of cellulytic activity and are found in a variety of habitats as ubiquitous agents of decay Some species are plant pathogens that cause a range of economically important diseases like stem cancer, leaf blight or leaf spot on a large variety of crops Latent infections can occur and result in post-harvest diseases or damping-off in case of infected seed

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Alternaria spp.: from general saprophyte to specific parasite.

Summary. An overview of the evolution of knowledge on the nomenclature, classification, induction, occurrence, functions, and role of pathogenesis-related proteins (PRs) is presented, covering generally the last fifteen years. The recommendations for naming and defining PRs are introduced, and the criteria required for the inclusion of new families into PRs are considered. The revision of the previous view on PRs as inducible proteins is argumented, given their constitutive expression in various plant organs and in seeds. Newly-discovered members of PRs families are described, and recent information about functionality of PRs, substantiating their antimicrobial action, is discussed. The biochemical and structural properties, as well as the organ-, tissue-, and cell-localisation, the induction and regulation of PRs are briefly outlined. Recent data about the relevance of PRs to plant development and disease resistance are examined, and the plausible application of engineering of PRs genes for crop improvement is critically commented. The finding that PRs, considered before as plant-specific proteins, are also expressed in other organisms, suggests that these proteins share an evolutionary origin and possess activity essential to the functioning and survival of living organisms.

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Pathogenesis-related proteins: research progress in the last 15 years

We examined whether exogenously applied melatonin could improve resistance to Marssonina apple blotch (Diplocarpon mali) by apple [Malus prunifolia (Willd.) Borkh. cv. Donghongguo]. This serious disease leads to premature defoliation in the main regions of apple production. When plants were pretreated with melatonin, resistance was increased in the leaves. We investigated the potential roles for melatonin in modulating levels of hydrogen peroxide (H2O2), as well the activities of antioxidant enzymes and pathogenesis-related proteins during these plant-pathogen interactions. Pretreatment enabled plants to maintain intracellular H2O2 concentrations at steady-state levels and enhance the activities of plant defence-related enzymes, possibly improving disease resistance. Because melatonin is safe and beneficial to animals and humans, exogenous pretreatment might represent a promising cultivation strategy to protect plants against this pathogen infection.

Exogenous melatonin improves Malus resistance to Marssonina apple blotch

Considerable success has been obtained in the use of classical breeding to control economically important plant diseases, such as the coffee leaf rust and the coffee berry disease (CBD). There is a strong consensus that growing genetically resistant varieties is the most appropriate cost effective means of managing plant diseases and is one of the key components of crop improvement. It has also been recognized that a better knowledge of both, the pathogens and the plant defence mechanisms will allow the development of novel approaches to enhance the durability of resistance. After a brief description of concepts in the field of plant disease resistance, we attempt to give a view of the research progress on coffee leaf rust and CBD concerned with the pathogens infection and variability, coffee breeding for resistance and coffee resistance mechanisms.

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Coffee resistance to the main diseases: leaf rust and coffee berry disease

Alternaria solani causes diseases on foliage (early blight), basal stems of seedlings (collar rot), stems of adult plants (stem lesions), and fruits (fruit rot) of tomato. Early blight is the most destructive of these diseases and hence receives considerable attention in breeding. For over 60 years, breeding for early blight resistance has been practiced, but the development of cultivars with high levels of resistance has been hampered by the lack of sources of strong resistance in the cultivated tomato and by the quantitative expression and polygenic inheritance of the resistance. In some accessions of wild species, high levels of early blight resistance have been found, but breeding lines still have unfavorable horticultural traits from the donor parent. Recently, the first linkage maps with loci controlling early blight resistance have been developed based on interspecific crosses. These maps may facilitate marker-assisted selection. This overview presents the current knowledge about the A. solani–tomato complex with respect to its biology, genetics, and breeding.

Tomato early blight (Alternaria solani): the pathogen, genetics, and breeding for resistance

Constitutive hydrolytic enzymes are associated with polygenic resistance of tomato to Alternaria solani and may function as an elicitor release mechanism

Jianseng Qiu

Papers

Constitutive hydrolytic enzymes are associated with polygenic resistance of tomato to Alternaria solani and may function as an elicitor release mechanism