Severe Fungal Diseases Research Articles

The role of silicon (Si) in increasing plant resistance against fungal diseases

Summary The use of silicon (Si) in agriculture has attracted a great deal of interest from researchers because of the numerous benefits of this element to plants. The use of silicon has decreased the intensity of several diseases in crops of great economic importance. In this study, the relationship between silicon nutrition and fungal disease development in plants was reviewed. The current review underlines the agricultural importance of silicon in crops, the potential for controlling fungal plant pathogens by silicon treatment, the different mechanisms of silicon-enhanced resistance, and the inhibitory effects of silicon on plant pathogenic fungi in vitro. By combining the data presented in this paper, a better comprehension of the relationship between silicon treatments, increasing plant resistance, and decreasing severity of fungal diseases could be achieved.

Development of a high-resolution melting marker for selecting Fusarium crown and root rot resistance in tomato.

Fusarium crown and root rot is a severe fungal disease of tomato caused by Fusarium oxysporum f. sp. radicis-lycopersici (FORL). In this study, the genomic location of the FORL-resistance locus was determined using a set of molecular markers on chromosome 9 and an F2 population derived from FORL-resistant inbred 'AV107-4' (Solanum lycopersicum) × susceptible 'L3708' (Solanum pimpinellifolium). Bioassay performed using Korean FORL strain KACC 40031 showed single dominant inheritance of FORL resistance in the F2 population. In all, 13 polymerase chain reaction-based markers encompassing approximately 3.6-72.0 Mb of chromosome 9 were developed based on the Tomato-EXPEN 2000 map and SolCAP Tomato single nucleotide polymorphism array analysis. These markers were genotyped on 345 F2 plants, and the FORL-resistance locus was found to be present on a pericentromeric region of suppressed chromosomal recombination in chromosome 9. The location of the FORL-resistance locus was further confirmed by testing these markers against diverse commercial tomato and stock cultivars resistant to FORL. A restriction fragment length polymorphism marker, PNU-D4, located at approximately 6.1 Mb of chromosome 9 showed the highest match with the resistance locus and was used for conducting high-resolution melting analysis for marker-assisted selection of FORL resistance.

Fine mapping of a dominantly inherited powdery mildew resistance major-effect QTL, Pm1.1, in cucumber identifies a 41.1 kb region containing two tandemly arrayed cysteine-rich receptor-like protein kinase genes.

A dominantly inherited major-effect QTL for powdery mildew resistance in cucumber was fine mapped. Two tandemly arrayed cysteine-rich receptor-like protein kinase genes were identified as the most possible candidates. Powdery mildew (PM) is one of the most severe fungal diseases of cucumber (Cucumis sativus L.) and other cucurbit crops, but the molecular genetic mechanisms of powdery mildew resistance in cucurbits are still poorly understood. In this study, through marker-assisted backcrossing with an elite cucumber inbred line, D8 (PM susceptible), we developed a single-segment substitution line, SSSL0.7, carrying 95 kb fragment from PM resistance donor, Jin5-508, that was defined by two microsatellite markers, SSR16472 and SSR16881. A segregating population with 3600 F2 plants was developed from the SSSL0.7 × D8 mating; segregation analysis confirmed a dominantly inherited major-effect QTL, Pm1.1 in cucumber chromosome 1 underlying PM resistance in SSSL0.7. New molecular markers were developed through exploring the next generation resequenced genomes of Jin5-508 and D8. Linkage analysis and QTL mapping in a subset of the F2 plants delimited the Pm1.1 locus into a 41.1 kb region, in which eight genes were predicted. Comparative gene expression analysis revealed that two concatenated genes, Csa1M064780 and Csa1M064790 encoding the same function of a cysteine-rich receptor-like protein kinase, were the most likely candidate genes. GFP fusion protein-aided subcellular localization indicated that both candidate genes were located in the plasma membrane, but Csa1M064780 was also found in the nucleus. This is the first report of dominantly inherited PM resistance in cucumber. Results of this study will provide new insights into understanding the phenotypic and genetic mechanisms of PM resistance in cucumber. This work should also facilitate marker-assisted selection in cucumber breeding for PM resistance.

Critical-point models to relate yield and disease intensity of the multiple pathosystem in rice leaf spots disease

ABSTRACT: The occurrence of leaf spots in irrigated rice can reduce the yield and compromise the quality of the grain. However it is unknown the economic damage threshold (EDT) that these spots cause the yield of crop. The objective of this study was to obtain damage functions for models of critical, to relate damage by simultaneous occurrence of blast, brown spot and scald spot with grain yield harvests in 2011/12 and 2012/2013, in Rio do Oeste, Santa Catarina State, Brazil. Gradient of diseases intensity was generated by number of applications and fungicides rates. Design was a randomized block with four replications and six treatments consisting of mixing fungicide applications of triazole (difenoconazole) and strobilurin (azoxystrobin). In 2011/12 and 2012/13 growing season were made two and three tests respectively with the same experiment. Before each application it was determined the incidence and severity of fungal diseases. The critical point models were obtained by linear regression between grain yield and incidence (I) and severity (S). In 2011/12 the functions were not significant at the beginning of tillering and 2012/2013 harvest resulted in R=13.404-92.98I and R=10.685-3.804S. Respectively in each harvest resulted in tillering (R=9.141-103.6I; R=7.605-1.538 and R=8.864-73.91I; R=7.202-77S), panicle initiation (R=9.432-188.5I; R=7.,038-1.466S and R=10.176-87.33I; R=8.258-533.55S), booting (R=7.044-71.78I; R=6.881-1.296S and R=9.993-71.74I; R=8.846-763.83S), flowering (R=7.447-82.29I; R=8.731-1.398S and R=8.347-54.36I; R=7.338-681.52S) and milky grain (R=10.143-80.5I; R=7.522-1.402S and R=8.661-60.063I; R=9.754-1.465S). The generated functions allow getting the damage coefficient for use in the calculation of EDT in multiple pathossystem leaf spots in irrigated rice.

Fungal infections in the ICU: advances in treatment and diagnosis.

The aim of this review is to give an update on the available diagnostic approaches and currently adopted therapeutic management of severe fungal diseases in the ICU setting. In order to reduce the clinical impact of life-threatening Candida infections, prompt diagnosis and appropriate treatment are strictly required. Preemptive strategies, mainly based on serological markers [i.e., (1-3)-β-D-glucan assay] are progressively replacing prophylactic and empirical approaches, limiting inadequate antifungal use. For the diagnosis of aspergillosis new algorithm has been recently validated, supported by the better knowledge of galactomannan antigen kinetic as a clinical marker. Echinocandins and voriconazole are the first choice drugs for the treatment of invasive Candida and Aspergillus infections, respectively. Although rare, other fungal infections (i.e., Pneumocystis jirovecii, Cryptococcus spp., and Mucorales spp.) may be responsible for life-threatening diseases in ICU patients, and early diagnosis and appropriate treatment are also important. Critically ill patients may frequently experience severe invasive fungal infections. Biomarkers-based diagnostic approaches give, at the same time, the possibility to early detect the ongoing infection and reduce inappropriate antifungal therapy in nonconfirmed cases. Potent and well tolerated drugs are now available for the treatment of proven cases but clinicians should carefully consider the risk of treatment failure and the availability of new monitoring and therapeutic tools.

Metabolic response of narrow leaf lupine (Lupinus angustifolius) plants to elicitation and infection with Colletotrichum lupini under field conditions

Lupine (Lupinus spp.) is one of the crop plants from the Fabaceae family cultivated on a moderate scale in Europe, Australia and South America; however, its cultivation suffers from a severe fungal disease anthracnose caused by Colletotrichum lupini fungus. The search for resistant plant genotypes as well as methods of plant immunization against such infections is of importance. Plant interaction with pathogenic microorganisms results in complex regulation of many biochemical and physiological processes. Activation of expression of defence genes that leads to the induction of bioactive secondary metabolites biosynthesis is among them. The aim of the presented work was to investigate changes in the isoflavonoids quantities as the reaction of narrow leaf lupine (Lupinus angustifolius) plants growing in the field conditions to infection with the pathogenic fungus (C. lupini) or treatment with its phytotoxic metabolites followed after 48 h with infection with the fungus. The metabolic profiling after field experiments revealed variety-specific changes of these compounds. Elicitation of plants with fungal phytotoxin prior to infection resulted in higher levels of prenylated isoflavones, especially phytoalexins luteone and wighteone and their various glycoconjugates in comparison to those observed in plants infected only with the fungal spores. The metabolomic analyses were supported by the transcriptomic view of genes involved in isoflavonoids biosynthesis. Infection of Lupinus angustifolius by Colletotrichum lupini combined with former elicitation of plants results in accumulation of prenylated isoflavonoids and change in the isoflavone prenyltransferase gene expression pattern.

Sesquiterpene volatile organic compounds (VOCs) are markers of elicitation by sulfated laminarine in grapevine.

Inducing resistance in plants by the application of elicitors of defense reactions is an attractive plant protection strategy, particularly for grapevine (Vitis vinifera), which is susceptible to severe fungal diseases. Although induced resistance (IR) can be successful under controlled conditions, in most cases, IR is not sufficiently effective for practical disease control under outdoor conditions. Progress in the application of IR requires a better understanding of grapevine defense mechanisms and the ability to monitor defense markers to identify factors, such as physiological and environmental factors, that can impact IR in the vineyard. Volatile organic compounds (VOCs) are well-known plant defense compounds that have received little or no attention to date in the case of grape-pathogen interactions. This prompted us to investigate whether an elicitor, the sulfated laminarin (PS3), actually induces the production of VOCs in grapevine. An online analysis (proton-transfer-reaction quadrupole mass spectrometry) of VOC emissions in dynamic cuvettes and passive sampling in gas-tight bags with solid-phase microextraction-GC-MS under greenhouse conditions showed that PS3 elicited the emission of VOCs. Some of them, such as (E,E)-α-farnesene, may be good candidates as biomarkers of elicitor-IR, whereas methyl salicylate appears to be a biomarker of downy mildew infection. A negative correlation between VOC emission and disease severity suggests a positive role of VOCs in grape defense against diseases.

Quick and Accurate Detection and Quantification of Magnaporthe oryzae in Rice Using Real-Time Quantitative Polymerase Chain Reaction.

Rice blast, caused by Magnaporthe oryzae, is one of the most severe fungal diseases in rice worldwide. In this study, we developed methods to quickly and accurately detect and quantify M. oryzae in the pure cultures of the fungus, rice plants, and rice seed by using SYBR Green I of the real-time quantitative polymerase chain reaction (qPCR). Results of absolute qPCR show that Magnaporthe oryzae can be detected at as low as 6.9 × 10-5 ng of genomic DNA. Results also show that all 10 varieties of rice seed examined in this study contain this fungus, indicating that M. oryzae is generally widespread in rice seed. We report the quantification of DNA of M. oryzae in rice leaves collected in the field, instead of in the lab, using relative qPCR by using rice actin gene as a housekeeping gene. Our results show great practical significance because we would know the potential fungal infection even before planting.

Luna Sensation 500 SC – nowy fungicyd do zwalczania chorób porzeczki czarnej

Summary American gooseberry mildew (Podosphaera mors-uvae), leaf spot (Drepanopeziza ribis) and white pine blister rust (Cronartium ribicola) are the most severe fungal diseases of black currant (Ribes nigrum). On commercial plantations control of these diseases is based mainly on the chemical method. However, the assortment of currently registered fungicides is limited to three products. The experiments, performed in 2010–2011 with new fungicide Luna Sensation 500 SC containing fluopyram and trifloxystrobin, showed its high effectiveness in control of black currant diseases. This fungicide applied at the doses of 0.6 and 0.8 l/ha very effectively controlled American gooseberry mildew (over 96%), leaf spot (over 88%) and white pine blister rust (over 82%). The effectiveness of Luna Sensation 500 SC was similar or higher than commonly used fungicides such as Score 250 EC and Signum 33 WG, thus it can be a suitable candidate recommended for efficient control of black currant fungal diseases, especially for anti resistant strategy.

Screening of culture conditions for pathogens of potato dry rot

Dry rot is a severe fungal disease during potato storage. Fusarium spp. is the pathogen causing severe rot of potato tubers, producing Fusarium toxins and contaminating food. The disease leads to a huge loss to China's potato industry. The present research optimized and screened the culture conditions of the major pathogens causing potato dry rot including Fusarium culmorum, Fusarium avenaceum, Fusarium sambucinum, Fusarium solani var. coeruleum, Fusarium trichothecioides, and Fusarium sporotrioides. The results showed that F. sambucinum and F. culmorum were sensitive to temperature and pH. F. sambucinum, F. trichothecioides, F. Solani var. coeruleum, and F. sporotrioides are favorable to the glucose-based culture while F. culmorum and F. avenaceum were to sucrose-based culture. Illumination stimulated the growth of F. sambucinum and F. sporotrioides but inhibited the growth of F. culmorum and F. avenaceum. It is concluded that the culture conditions are different with species of Fusarium and the understanding of the culture conditions is expected useful in research and the disease control.

Transcriptional profiling of the responses to infection by the false smut fungus Ustilaginoidea virens in resistant and susceptible rice varieties

Rice false smut is a severe fungal disease worldwide, but the mechanisms underlying resistance to the causal agent Ustilaginoidea virens in rice remain unknown. We performed RNA-Seq to investigate the transcriptional modulation in resistant and susceptible rice varieties for the responses to U. virens infection. In total, 1405 and 1066 differentially expressed genes (DEGs) were identified in resistant ‘IR28’ and susceptible ‘HXZ’ cultivars, respectively. Gene ontology (GO) enrichment analysis revealed a set of GO terms differentially enriched in the two rice varieties. Functional analysis of DEGs showed that a large number of genes encoding secondary metabolites, flavin-containing monooxygenases and peroxidases were differentially regulated. Classification analysis of DEGs revealed that brassinosteroids may have more important roles than salicylic acid and ethylene in response to U. virens infection; the crosstalk of other hormones such as auxin, gibberellins and jasmonates may also affect U. virens infection. Our results revealed that pattern recognition, cellular metabolic changes and hormone signalling constitute a comprehensive network to manipulate the responses of host rice plant to U. virens infection.

Role of Acute Graft-Versus-Host Disease in the Risk of Bacteremia and Invasive Fungal Disease after Allogeneic Hemopoietic Stem Cell Transplantation in Children. Results from a Single-Center Observational Study

Data on epidemiology of severe infectious complications, ie, bacteremia or invasive fungal disease (IFD), in children with acute graft-versus-host disease (aGVHD) after allogeneic hemopoietic stem cell transplantation (HSCT) are scarce. In a retrospective, single-center study, we analyzed the risk (hazard ratio [HR]) and the rate (episodes/1000 patients days at risk) of bacteremias and IFD in children receiving allogeneic HSCT, according to the type of donor (matched related [MRD] or alternative [AD]) and presence and grade of aGVHD. From 2000 to 2009, 198 children receiving 217 allogeneic HSCT developed 134 severe infectious episodes (103 bacteremias and 31 IFD). The type of donor (AD versus MRD) was the most important risk factor for the severe infections (P = .0052). In separate multivariable analysis for bacteremia and IFD, children receiving an AD HSCT had increased HR and rate of bacteremia compared with those receiving a MRD transplantation (P = .0171 and P = .0001, respectively), whereas the HR and the rate of IFD were significantly influenced by the grade of aGVHD (P = .0002 and P < .0001, respectively). Finally, infectious episodes occurred late after HSCT, especially in presence of severe aGVHD, and bacteremias were 3 to 6 times more frequent than IFD. These data may be important to design management strategies of infections in pediatric allogeneic HSCT.

Exoenzymes Activity and Biofilm Production in Candida Species Isolated from Various Clinical Specimens in Benha University Hospital, Egypt

Background: The frequency of severe systemic fungal diseases has increased in the last few decades. Aims: This study was done to speciate the candida isolates, to determine their antifungal susceptibility pattern and to detect biofilm formation and exoenzymes (phospholipase and proteinase) production. Place and Duration of Study: This is a Six-months Cross sectional study conducted in ICU and Microbiology & Immunology departments, Benha University, Egypt Methodology: The study was conducted on 75 Candida spp. isolated from various clinical samples of patients admitted in ICU. The Candida isolates were identified upto species level. Antifungal susceptibility testing was done by disc diffusion method. The biofilm formation was assessed by inoculating the isolates in conical polystyrene test tube containing Sabouraud’s dextrose broth supplemented with glucose. Proteinase activity was detected by using plates containing bovine serum albumin (BSA) agar. Phospholipase activity was detected by using egg yolk agar. Results: Seventy five Candida spp. were isolated from different clinical samples. C. Original Research Article British Microbiology Research Journal, 4(6): 654-667, 2014 655 albicans was isolated from 39(52%) samples. Non-albicans Candida (NAC) spp. were isolated from 36 (48%) clinical specimens. Forty one (54.7%) out of 75 Candida species isolates obtained from the clinical isolates produced biofilm. Out of 39 C. albicans isolates 20 (51.3%) produced biofilm, while out of 36 NAC species isolates 21 (58.3%) produced biofilm. The number of total proteinase positive isolates were 50 (66.7%). C. albicans was higher than that of the NAC isolates (29 [66.7%] versus 21 [58.3%]). Phospholipase positive isolates of C. albicans was higher than that of the NAC isolates (32[82.1%] versus 37[49.3%]). All isolates were susceptible to amphotericin B and ketoconazole. Resistance to fluconazole was found in 8 isolates (22.2%) of NAC spp. and 2 isolates (5.1%) of C. albicans isolates. Conclusion: The isolation of C. albicans were 39 (52%) in different clinical samples and isolation of NAC spp. were 36(48%). So NAC spp. is no longer overlooked as these organisms are emerging pathogens. The number of NAC producing proteinase, phospholipase and biofilm are more than the number of C. albicans producing these virulence factors. The C. albicans and NAC showed 100% susceptiblity to amphotericin B and ketokonazole while fluconazole showed resistance in 22.2% of NAC spp. and 5.1% of C. albicans isolates. All resistant Candida species to fluconazole were biofilm producers.

PEGylated Bile Acids for Use in Drug Delivery Systems: Enhanced Solubility and Bioavailability of Itraconazole

Itraconazole is a drug of choice for the treatment of severe fungal infections and parasitic diseases, but its use is limited by its low water solubility and varying bioavailability. New self-emulsifying drug delivery systems (SEDDS) based on PEGylated bile acids (BA-PEGs) were designed and prepared, where the number and length of PEG arms were varied to optimize the loading of itraconazole in the final drug formulation. The use of both BA-PEGs and oleic acid improved the solubilization and absorption of the drug, which was in a glassy state in the SEDDS prepared with the melting method. High loading efficiencies of itraconazole (up to 20%) and stable liquid formulations were obtained at neutral pH, and full dispersion of itraconazole was reached in 2 h in simulated intestinal fluid (pH 6.8). Aqueous emulsions consisting of spherical micelles with mean hydrodynamic diameters (Dh) of ca. 75-220 nm, as verified by transmission electron microscopy and dynamic light scattering, are expected to improve the intestinal absorption of the drug. The new SEDDS showed good cytocompatibility by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays of BA-PEGs with Caco-2 and RAW 264.2 cells, and a low degree of hemolysis of human erythrocytes. The SEDDS based on PEGylated bile acids provide a controlled release system with significant improvement of the bioavailability of itraconazole in rats, as demonstrated by the pharmacokinetic studies.

Genomic Prediction of Northern Corn Leaf Blight Resistance in Maize with Combined or Separated Training Sets for Heterotic Groups

Northern corn leaf blight (NCLB), a severe fungal disease causing yield losses worldwide, is most effectively controlled by resistant varieties. Genomic prediction could greatly aid resistance breeding efforts. However, the development of accurate prediction models requires large training sets of genotyped and phenotyped individuals. Maize hybrid breeding is based on distinct heterotic groups that maximize heterosis (the dent and flint groups in Central Europe). The resulting allocation of resources to parallel breeding programs challenges the establishment of sufficiently sized training sets within groups. Therefore, using training sets combining both heterotic groups might be a possibility of increasing training set sizes and thereby prediction accuracies. The objectives of our study were to assess the prospect of genomic prediction of NCLB resistance in maize and the benefit of a training set that combines two heterotic groups. Our data comprised 100 dent and 97 flint lines, phenotyped for NCLB resistance per se and genotyped with high-density single-nucleotide polymorphism marker data. A genomic BLUP model was used to predict genotypic values. Prediction accuracies reached a maximum of 0.706 (dent) and 0.690 (flint), and there was a strong positive response to increases in training set size. The use of combined training sets led to significantly greater prediction accuracies for both heterotic groups. Our results encourage the application of genomic prediction in NCLB-resistance breeding programs and the use of combined training sets.

Susceptibility of winter rape cultivars to fungal diseases and their response to fungicide application

The productivity of winter oilseed rape cultivars is limited by various pests and diseases. The aim of this study was to determine the differences in the susceptibility of Lithuanian-grown winter rape cultivars to main fungal diseases, their yield performance, and their response to the fungicide application. A 2-factorial field experiment was carried out at the Institute of Agriculture of the Lithuanian Research Centre for Agriculture and Forestry over 3 growing seasons (2007/08, 2008/09, and 2009/10). The influence of fungicide application and cultivar (15 cultivars during the first and second seasons, and 6 cultivars during the third season) on the incidence and severity of phoma stem canker, alternaria black spot, and sclerotinia stem rot, as well as on the seed yield and thousand-seed weight, was evaluated. Experimental findings indicated that the incidence and severity of fungal diseases varied considerably among the growing seasons. The incidence of basal phoma stem canker was significantly influenced by the cultivar during all 3 growing seasons; however, significant effect of the cultivar on the mean severity of basal canker was obtained only in 2009. Fungicide spray applications significantly decreased the incidence and severity of fungal diseases and significantly increased the seed yield of winter rape. Significant and positive yield response to the fungicide application was obtained for almost all tested cultivars during the first 2 seasons. Cultivars that were higher yielding without treatment (Insider, Sunday, Monalisa, Rally, and Titan) showed lower response to the fungicide application. The use of fungicides demonstrated the highest economic return from the cultivars Lirajet, Casino, Siska, Liprima, and Valesca.

Observation on Baseline Sensitivity of &amp;lt;i&amp;gt;Erysiphe necator&amp;lt;/i&amp;gt; Genetic Groups to Azoxystrobin

Powdery mildew, caused by Erysiph necator, is a common and severe fungal disease of grapevine all over the world. The disease costs millions of dollars to vine growers, due to intensive use of fungicides and yield losses. Recently in population of E. necator two genetic groups have been described, the two groups seem to occupy different temporal niches, with a temporal alternation that is clear-cut in vineyards intensively treated with chemical fungicides. QoI-STAR (Quinol Outside Inhibitors-Strobilurin Type of Action and Resistance) fungicides are widely used to control the disease, and generally carry a high risk of pathogen resistance development. To clarify the behaviors of the biotrophic fungus when treated with azoxystrobin as a representative of QoI-STAR, baseline sensitivity of laboratory isolates were determined. A leaf bioassay and the primers RSCBF1 and RSCBR2 designed on the highly conserved regions of cytb gene in fungi were used. Partial sequence of E. necator cytb gene were obtained. Attempts to obtain a laboratory mutant were not totally successful. The sensitivity to azoxystrobin (EC50) in isolates of genetic group B was significantly higher than in isolates of group A, to which all the isolates collected later in the season belonged. The higher sensitivity to azoxystrobin fungicides observed in group B isolates can be at the basis of their precocious disappearance in vineyards, and can have important implications for powdery mildew control strategies.

DAMP signaling in fungal infections and diseases

Fungal infections and diseases predominantly affect patients with deregulated immunity. Compelling experimental and clinical evidence indicate that severe fungal diseases belong to the spectrum of fungus-related inflammatory diseases. Some degree of inflammation is required for protection during the transitional response occurring temporally between the rapid innate and slower adaptive response. However, progressive inflammation worsens disease and ultimately prevents pathogen eradication. The challenge now is to elucidate cellular and molecular pathways distinguishing protective vs. pathogenic inflammation to fungi. In addition to fungal ligands of pattern recognition receptors (pathogen-associated molecular patterns, PAMPs), several host-encoded proteins, the damage-associated molecular patterns (DAMPs), are released during tissue injury and activate innate recognition receptors. DAMPs have been shown to regulate inflammation in fungal diseases. The DAMP/receptor for advanced glycation end-products axis integrated with the PAMP/Toll-like receptors axis in the generation of the inflammatory response in experimental and clinical fungal pneumonia. These emerging themes better accommodate fungal pathogenesis in the face of high-level inflammation seen in several clinical settings and point to DAMP targeting as a novel immunomodulatory strategy in fungal diseases.

Identification and Precise Mapping of Resistant QTLs of Cercospora Leaf Spot Resistance in Sugar Beet (Beta vulgaris L.).

The complex inheritance of resistance to Cercospora leaf spot (CLS), the most severe fungal foliar disease in sugar beet, was investigated by means of quantitative trait loci (QTL) analysis. Over a three year period, recombinant inbred lines (RILs) of sugar beet (Beta vulgaris L.), generated through a cross between lines resistant (‘NK-310mm-O’) and susceptible (‘NK-184mm-O’) to CLS, were field-tested for their resistance to the pathogen. Composite interval mapping (CIM) showed four QTL involved in CLS resistance to be consistently detected. Two resistant QTL (qcr1 on chromosome III, qcr4 on chromosome IX) bearing ‘NK-310mm-O’ derived alleles promoted resistance. Across 11 investigations, the qcr1 and qcr4 QTL explained approximately 10% and over 20%, respectively, of the variance in the resistance index. Two further QTL (qcr2 on chromosome IV, qcr3 on chromosome VI) bearing ‘NK-184mm-O’ derived alleles each explained about 10% of the variance. To identify the monogenic effect of the resistance, two QTL derived from ‘NK-310mm-O’ against the genetic background of ‘NK-184mm-O’, using molecular markers. The qcr1 and qcr4 were precisely mapped as single QTL, using progenies BC5F1 and BC2F1, respectively. The qcr1 that was located near e11m36-8 had CLS disease severity indices (DSI) about 15% lower than plants homozygous for the ‘NK-184mm-O’ genotype. As with qcr1, heterozygosis of the qcr4 that was located near e17m47-81 reduced DSI by about 45% compared to homozygosis. These two resistant QTL might be of particular value in marker-assisted selection (MAS) programs in CLS resistance progression.

Infection of the Sunagoke moss panels with fungal pathogens hampers sustainable greening in urban environments

Drought and heat tolerance of the Sunagoke moss ( Racomitrium japonicum) and the low thermal conductivity of the dry moss tissue offer novel greening and insulation possibilities of roofs and walls to mitigate the heat island phenomenon in urban environments. However, damage may appear in the moss panels under humid conditions in Japan. In this study we characterized fungi associated with the damaged areas of the Sunagoke moss panels. Fungi were identified by morphology and internal transcribed spacer (ITS) sequence analysis and tested for pathogenicity on R. japonicum (Grimmiaceae) and an unrelated moss species ( Physcomitrella patens; Funariaceae) under controlled conditions. Alternaria alternata, Fusarium avenaceum and Fusarium oxysporum caused severe necrosis and death, whereas Cladosporium oxysporum and Epicoccum nigrum caused milder discoloration or chlorosis in both moss species. The fungi pathogenic on moss were closely related to fungal pathogens described from cultivated vascular plants. Ammonium increased severity of fungal diseases in moss. This study demonstrated that fungi can cause economically significant diseases in cultivated moss and hamper commercial use of the moss panels unless appropriate control methods are developed. Use of a single moss clone to cover large surfaces and the air pollutants such as ammonium may increase the risk for fungal disease problems.