Abstract: The cultivation of wheat varieties resistant to Fusarium head blight (FHB) is recognized as one of the most important components to diminish losses due to this disease. Although there is no known immunity to this disease in wheat germplasm, considerable improvements in genetic resistance have been achieved by concentrated breeding efforts that have relied primarily upon repeated field and greenhouse-based screening. DNA markers are a relatively new technology that can be used to increase breeding progress, especially for traits such as FHB that are difficult to select for under field conditions and that are controlled by multiple genes. Marker-assisted selection (MAS) uses markers to select for particular DNA segments that are genetically linked to genes that provide incremental resistance to FHB. One particular gene, designated Fhb1, provides a 20–25% average reduction in FHB symptoms. This gene and its associated markers have been validated in numerous breeding programs and is widely used to more precisely breed for resistance. About a dozen other genes affecting FHB reaction have been identified, but they have smaller and more inconsistent effects compared with Fhb1. Nevertheless, breeders are discovering which of these markers can be combined with Fhb1 in their genetic backgrounds to enhance resistance. The establishment of the USDA-ARS Regional Small Grains Genotyping Centers and similar facilities around the world have increased the capacity for wheat breeders to utilize this powerful technology. More efficient DNA extraction technologies and marker platforms will allow breeders to more fully implement MAS in the future.
Abstract: Oligandrin, the elicitin-like protein produced by the mycoparasite Pythium oligandrum, crab shell chitosan and crude glucans, isolated from P. oligandrum cell walls were applied to decapitated tomato plants and evaluated for their potential to induce defence mechanisms in root tissues infected by Fusarium oxysporum f. sp. radicis-lycopersici. A significant decrease in disease incidence was monitored in oligandrin- and chitosan-treated plants as compared to water-treated plants whereas glucans from P. oligandrum cell walls failed to induce a resistance response. Ultrastructural investigations of the infected root tissues from water-treated (control) plants showed a rapid colonization of all tissues including the vascular stele. In root tissues from oligandrin-treated plants, restriction of fungal growth to the outer root tissues, decrease in pathogen viability and formation of aggregated deposits, which often accumulated at the surface of invading hyphae, were the most striking features of the reaction. In chitosan-treated plants, the main response was the formation of enlarged wall appositions at sites of attempted penetration. These wall appositions were found to vary greatly in their appearance from multi-textured to multi-layered structures and to contain large amounts of callose. The use of the WGA/ovomucoid-gold complex provided evidence that the wall-bound chitin component in Fusarium cells colonizing roots of oligandrin-treated tomato plants was not substantially altered even over cell walls of hyphae showing obvious signs of degradation. Evidence is provided in this study that oligandrin has the ability to induce systemic resistance in tomato. Exogenous, foliar applications of the fungal protein sensitize susceptible tomato plants to react more rapidly and more efficiently to F. o. f. sp. radicis-lycopersici attack, mainly through the massive accumulation of fungitoxic compounds at sites of attempted pathogen penetration. Although cell wall modifications do not represent the central core of the oligandrin-mediated host response in tomato, they are part of the multicomponent defence system elaborated to fend off Fusarium invasion.
Abstract: The coffee disease complex known as corky-root, composed of the root-knot nematode Meloidogyne arabicida and Fusarium oxysporum, causes serious damage to Coffea arabica in Costa Rica. Resistance to Meloidogyne arabicida alone and to the field population (M. arabicida, M. exigua, F. oxysporum) was evaluated under controlled and field conditions. The studied material consisted of subspontaneous-derived C. arabica accessions, C. canephora accessions, introgression lines derived from the interspecific Timor Hybrid (C. arabica×C. canephora) and F1 hybrids from crosses between subspontaneous-derived accessions and cultivars. Accessions resistant to M. arabicida and to the field population were identified at varying frequencies in the different groups of study materials. The results showed that resistance to corky-root is heritable and that genetic resistance to M. arabicida is an effective strategy against corky-root disease. By using C. canephora rootstocks, it was possible to substantially reduce mortality in the field and reduce by half the number of plants with corky-root symptoms. The results were used to define appropriate strategies for the sustainable management of coffee corky-root disease resistance.
Abstract: Twenty-two nitrate nonutilizing (nit) mutants were recovered from five wild-type isolates of Fusarium graminearum and fifty nit mutants were recovered from three JS399-19-resistant mutants of F. graminearum cultured on MMC medium. Some biological properties were compared between nit mutants and their parental isolates. The results showed that there were no significant differences in growth rate, cultural characters or pathogenicity between JS399-19-resistant nit mutants and their parental isolates. But the conidial production and the sexual reproduction ability changed to some extent. There was no cross resistance toward chlorate and JS399-19 in F. graminearum and the resistance could be stable through 20-time subcultures. Therefore, the nit could be used as a genetic marker for studying the genetics of JS399-19 resistance in F. graminearum, which was used to study JS399-19 resistance transferability in hyphal fusion. Resistance in JS399-19 could not be transferred by hyphal fusion or could be transferred with low chance between two compatible isolates, which would delay the development of JS399-19 resistance in the field.
Abstract: The in vitro activities of amphotericin B (AMB), itraconazole (ITC), voriconazole (VCZ) and terbinafine (TBF) alone and in the combinations AMB+VCZ, TBF+ITC and TBF+VCZ were evaluated against 29 clinical isolates of Fusarium spp. (15 Fusarium solani, 7 Fusarium oxysporum, 2 Fusarium decemcellulare, 2 Fusarium dimerum and 3 other Fusarium spp.). Minimum inhibitory concentrations were determined using the method of the Clinical and Laboratory Standards Institute and the interaction activity was calculated using the fractional inhibitory concentration index. The four antifungal drugs tested alone showed very limited activity against most of the isolates. In contrast, the combination TBF+VCZ showed synergy for 21 isolates. The combination AMB+VCZ showed synergism for only five strains. No interaction or antagonism was observed among the remaining strains. TBF+ITC showed no interaction for 18 strains. The in vitro antifungal activity of the drugs alone and in combination varied for different species. These results corroborate previous in vitro studies in which the combination TBF+VCZ showed synergy against Fusarium spp., although further studies are needed to elucidate its potential usefulness for therapy.
Abstract: A kaempferide triglycoside has been found as a constitutive component in an uninfected carnation (Dianthus caryophyllus) of the cultivar Novada. The chemical structure has been determined mainly by the use of spectroscopic methods, including 2D NMR experiments. It showed a strong activity in restricting fungal parasite development, which could contribute to the known ability of carnation cv. Novada to resist to Fusarium oxysporum f. sp. dianthi infection.
Abstract:Fusarium head blight (FHB) is a disease that causes major economic losses in wheat and barley production worldwide. Contamination of food with the trichothecene mycotoxin deoxynivalenol (DON) produced by Fusarium is a major health concern for humans and animals because trichothecenes are potent cytotoxins of eukaryotic cells. Trichothecene mycotoxins inhibit translation by targeting ribosomal protein L3 at the peptidyltransferase center. We previously showed that expression of an N-terminal fragment of yeast L3 (L3Δ) in transgenic tobacco plants reduced the toxicity of DON. Here, we produced transgenic wheat plants that express the same yeast L3 (L3Δ) fragment and evaluated their susceptibility to F. graminearum infection and their ability to accumulate DON. Following F. graminearum infection in greenhouse tests, two transgenic wheat lines expressing the highest levels of L3Δ showed reductions in disease severity and kernel DON levels, compared to non-transformed plants. In a field test, a transgenic wheat line with the highest L3Δ expression controlled by the maize Ubi1 promoter had significant reductions in visually scabby kernels and kernel DON levels. These results demonstrate that expression of a modified form of the ribosomal protein that is the target of DON can improve FHB resistance in wheat.
Abstract: Fumonisins, metabolites of Fusarium verticillioides (=F. moniliforme) and related fungi that occur naturally on corn, elicit various organ- and species-specific toxicities. However, immunologic effects of fumonisins are not well characterized. BALB/c mice were fed diets containing F. verticillioides culture material (CM) providing 50 (LD) or 150 (HD) ppm fumonisins (FB1+FB2) beginning 1 week before and continuing 5 weeks after challenge with the myotropic Brazil strain of T. cruzi. A control group (ZD) was fed a diet lacking CM. The LD and HD diets caused increases in tissue sphinganine/sphingosine ratios and minimum to mild hepatotoxicity, both of which are typically induced by fumonisins. Nitric oxide (NO) production by peritoneal macrophages from HD mice was significantly higher than by peritoneal macrophages from ZD mice on day 14 after challenge. NO production also was stimulated in macrophages from ZD mice, but the peak response did not occur until day 26 after challenge. Compared with ZD mice, LD and HD mice exhibited reduced parasitemia and decreased numbers of pseudocysts in cardiac muscle. Thus, the CM increased host resistance to T. cruzi by accelerating NO production by macrophages or otherwise enhancing the immune response. The findings provide additional evidence that fumonisins modulate immune function.
Abstract:Fusarium wilt (Fusarium oxysporum f. sp. ciceris (Padwick) Matuo and K. Sato) is one of the major yield limiting factors of chickpea (Cicer arietinum L.). For eco-friendly and sustainable management of the disease, 10 isolates belonging to three species of Trichoderma (Trichoderma viride, Trichoderma harzianum, and Trichoderma virens) were evaluated against four isolates of the pathogen representing four different races commonly prevalent in India. Dharwad (race 1), Kanpur (race 2), Ludhiana (race 3), and Delhi (race 4) isolates of F. oxysporum f. sp. ciceris were included in the study. The isolates of Trichoderma species were evaluated against the pathogen in dual culture and through production of volatile and non-volatile inhibitors. T. viride isolated from Ranchi followed by T. harzianum (Ranchi) and T. viride isolated from Delhi inhibited maximum mycelial growth of the pathogen. They also enhanced seed germination, root and shoot length, and decreased wilt incidence under green house condition. The isolates proved potential in vitro tests were evaluated along with other bioagents individually and in combination with carboxin under wilt sick field during 2002/03, 2003/04, and 2004/05 cropping season in randomized block design in three replications. Species of Trichoderma were found superior to Bacillus subtilis and Kalisena a commercial formulation of Aspergillus niger. The efficacy of Trichoderma species was enhanced in combination with carboxin. The integration of T. harzianum (106 spores/ml/10 g seed) and carboxin (2 g kg-1 seed) for seed treatment was the best which enhanced seed germination by 12.0–14.0% and grain yields by 42.6–72.9% and reduced wilt incidence (44.1–60.3%) during experimentations.
Abstract: Date palm (Phoenix dactylifera L.) is qualified as a tree of great ecological and socio-economical importance in desert oases. Unfortunately, it is being decimated, especially in Morocco and Algeria, by a fusariosis wilt called bayoud and caused by Fusarium oxysporum f. sp. albedinis (Fao). Controlling this disease requires the implementation of an integrated management program. Breeding for resistance is one of the most promising component strategies of this program. Few naturally resistant cultivars with a mediocre fruit quality (dates) are known. Conventional and non-conventional methods are under development and have to use the simplest and easiest methods to screen for resistant individuals. The use of pathogen toxins as selective agents at the tissue culture step might be a source of variability that can lead to the selection of individuals with suitable levels of resistance to the toxin and/or to the pathogen among the genetic material available. Foa produces toxins such as fusaric, succinic, 3-phenyl lactic acids and their derivatives, marasmins and peptidic toxins. These toxins can be used bulked or separately as selective agents. The aim of this contribution was to give a brief overview on toxins and their use as a mean to select resistant lines and to initiate a discussion about the potential use of this approach for the date palm–Foa pathosystem. This review does not pretend to be comprehensive or exhaustive and was prepared mainly to highlight the potential use of Foa toxins for selecting date palm individuals with a suitable resistance level to bayoud using toxin-based selective media.
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