SUPPRESSION OF BULL’S EYE ROT OF APPLES AND GROWTH OF NEOFABRAEA PERENNANS BY SCALD CONTROL AGENTS DIPHENYLAMINE AND ETHOXYQUIN

1966 ◽  
Vol 46 (6) ◽  
pp. 633-638 ◽  
Author(s):  
L. E. Lopatecki ◽  
H. Burdon
Keyword(s):  
Propyl Gallate ◽  
Spore Germination ◽  
Potent Inhibitor ◽  
Hyphal Growth ◽  
Local Culture ◽  
Active Materials ◽  
Similar Reduction ◽  
Neofabraea Perennans ◽  
Bull's Eye

Postharvest dips of apples in diphenylamine or ethoxyquin, at concentrations that control storage scald, markedly reduced bull’s eye rot of fruit artificially inoculated with spores of Neofabraea perennans obtained from a local culture. Similar reduction in rot was obtained with the fungicide dodine, whereas the antioxidant propyl gallate was not effective.Comparative fungistatic tests indicated that dodine was a potent inhibitor of spore germination of N. perennans, and was only slightly less effective in suppressing hyphal growth. Diphenylamine inhibited hyphal growth to a greater extent than spore germination, while ethoxyquin inhibited hyphal growth only. Propyl gallate was essentially inactive in all tests. These data suggest that effectiveness of all three active materials against bull’s eye rot derives mainly from their ability to suppress hyphal growth.

scholarly journals Resistance to Boscalid Fungicide in Alternaria alternata Isolates from Pistachio in California

Plant Disease ◽  
2007 ◽  
Vol 91 (10) ◽  
pp. 1345-1350 ◽  
Author(s):  
Herve F. Avenot ◽  
Themis J. Michailides
Keyword(s):  
Spore Germination ◽  
Alternaria Alternata ◽  
Hyphal Growth ◽  
Conidial Germination ◽  
Prior History ◽  
In Vitro Tests ◽  
Fitness Parameters ◽  
History Of ◽  
The Mean

Boscalid is a new carboxamide fungicide recently introduced in a mixture with pyraclostrobin in the product Pristine for the control of Alternaria late blight of pistachio. In all, 108 isolates of Alternaria alternata were collected from pistachio orchards with (59 isolates) and without (49 isolates) prior exposure to boscalid. The sensitivity to boscalid was determined in conidial germination assays. The majority of isolates from two orchards without a prior history of boscalid usage had effective fungicide concentration to inhibit 50% of spore germination (EC50) values ranging from 0.089 to 3.435 μg/ml, and the mean EC50 was 1.515 μg/ml. Out of 59 isolates collected from an orchard with a history of boscalid usage, 52 isolates had EC50 values ranging from 0.055 to 4.222 μg/ml, and the mean EC50 was 1.214 μg/ml. However, in vitro tests for conidial germination and mycelial growth also revealed that seven A. alternata isolates, originating from the orchard exposed to boscalid were highly resistant (EC50 > 100 μg/ml) to this fungicide. Furthermore, in vitro tests showed no significant differences between wild-type and boscalid-resistant mutants in some fitness parameters such as spore germination, hyphal growth, sporulation, or virulence on pistachio leaves. Experiments on the stability of the boscalid-resistant phenotype showed no reduction of the resistance after the mutants were grown on fungicide-free medium. Preventative applications of a commercial formulation of boscalid (Endura) at a concentration which is effective against naturally sensitive isolates failed to control disease caused by the boscalid-resistant isolates in laboratory tests. To our knowledge, this is first report of field isolates of fungi resistant to boscalid.

Effect of the fumigant metham on Trichoderma spp.

1984 ◽  
Vol 30 (6) ◽  
pp. 739-745 ◽  
Author(s):  
J. A. Lewis ◽  
G. C. Papavizas
Keyword(s):  
Organic Matter ◽  
Natural Organic Matter ◽  
Active Ingredient ◽  
Spore Germination ◽  
Radial Growth ◽  
Hyphal Growth ◽  
Trichoderma Spp ◽  
Trichoderma Hamatum ◽  
Introduced Populations ◽  
Colony Forming Units

Radial growth of 34 isolates of Trichoderma hamatum, T. harzianum, and T. viride was inhibited (mean effective dose (ED50)) by as little as 1.3 μg of vapors (mostly methylisothiocyanate) per cubic centimeter of atmosphere from metham decomposing in soil suspensions. Isolates of T. hamatum were generally more sensitive than those of T. harzianum to the vapors. Spore germination was more sensitive than hyphal growth to vapors, and whereas the toxic volatiles were only fungistatic to growth, they were fungicidal to germination. As little as 0.5 μg/cm3 of vapors from decomposing metham in soil reduced germination of conidia of three isolates (TMP, Tm-1, and T-1-R4) more than 50% and in another three (T-1, Th-6, and Th-20) 90%. Exposure of spores to metham in solution (350 μg active ingredient/mL) for 1 h reduced survival more than 50% in eight isolates. When conidia of T. viride (T-1-R4) and T. harzianum (WT-6-24) were added (ca. 20 × 103 spores/g) to soil treated with a sublabel rate of metham (equivalent to 234 L/ha), the number of colony-forming units (CFU) of isolates introduced 4 days before, or at time of fumigation were significantly less than those in nonfumigated soil after 3 weeks of incubation. CFU of isolates introduced 4 days after fumigation were similar to those in nonfumigated soils. Over a 9-week period, introduced populations of T-1-R4 and WT-6-24 remained static in nonfumigated soils. Indigenous Trichoderma spp. appeared unaffected by the levels of metham used. Addition of bran or use of soils high in natural organic matter did not affect results.

scholarly journals Cdc42 Is Required for Proper Growth and Development in the Fungal Pathogen Colletotrichum trifolii

2006 ◽  
Vol 5 (1) ◽  
pp. 155-166 ◽  
Author(s):  
Changbin Chen ◽  
Young-sil Ha ◽  
Ji-young Min ◽  
Stephen D. Memmott ◽  
Martin B. Dickman
Keyword(s):  
Spore Germination ◽  
Fungal Pathogen ◽  
Hyphal Growth ◽  
Dominant Negative ◽  
Temperature Sensitive ◽  
Ras Signaling ◽  
Wild Type ◽  
Colletotrichum Trifolii ◽  
Downstream Effector ◽  
Wild Type Phenotype

ABSTRACT Cdc42 is a highly conserved small GTP-binding protein that is involved in regulating morphogenesis in eukaryotes. In this study, we isolated and characterized a highly conserved Cdc42 gene from Colletotrichum trifolii (CtCdc42), a fungal pathogen of alfalfa. CtCdc42 is, at least in part, functionally equivalent to Saccharomyces cerevisiae Cdc42p, since it restores the temperature-sensitive phenotype of a yeast Cdc42p mutant. Inhibition of CtCdc42 by expression of an antisense CtCdc42 or a dominant negative form of CtCdc42 (DN Cdc42) resulted in appressorium differentiation under noninductive conditions, suggesting that CtCdc42 negatively regulates pathogenic development in this fungus. We also examined the possible linkage between CtCdc42 and Ras signaling. Expression of a dominant active Cdc42 (DA Cdc42) in C. trifolii leads to aberrant hyphal growth under nutrient-limiting conditions. This phenotype was similar to that of our previously reported dominant active Ras (DA Ras) mutant. Also consistent with our observations of the DA Ras mutant, high levels of reactive oxygen species (ROS) were observed in the DA Cdc42 mutant, and proline restored the wild-type phenotype. Moreover, overexpression of DN Cdc42 resulted in a significant decrease in spore germination, virtually no hyphal branching, and earlier sporulation, again similar to what we observed in a dominant negative Ras (DN Ras) mutant strain. Interestingly, coexpression of DA Cdc42 with DN Ras resulted in germination rates close to wild-type levels, while coexpression of DN Cdc42 with the DA Ras mutant restored the wild-type phenotype. These data suggest that CtCdc42 is positioned as a downstream effector of CtRas to regulate spore germination and pathogenic development.

scholarly journals Effect of chitosan on hyphal growth and spore germination of plant pathogenic and biocontrol fungi

2007 ◽  
Vol 0 (0) ◽  
pp. 071010063119021-??? ◽  
Author(s):  
J. Palma-Guerrero ◽  
H.-B. Jansson ◽  
J. Salinas ◽  
L.V. Lopez-Llorca
Keyword(s):  
Spore Germination ◽  
Hyphal Growth ◽  
Biocontrol Fungi

scholarly journals Role of Phosphorylation in Fungal Spore Germination

1993 ◽  
Author(s):  
Martin B. Dickman ◽  
Oded Yarden
Keyword(s):  
Protein Kinase ◽  
Spore Germination ◽  
Plant Pathogens ◽  
Hyphal Growth ◽  
Fungal Spore ◽  
Tube Formation ◽  
Kinase Gene ◽  
Fungal Plant Pathogens ◽  
Dependent Protein ◽  
Protein Kinase Gene

Spore germination is a common and fundamental event in fungal development and in many instances an essential phase of fungal infection and dissemination. Spore germination is also critical for hyperparasites to function as biocontrol agents as well as in fermentation proceses. Our common objective is to understand the mechanisms which regulated spore germination and identify factors involved in pathogenicity related prepenetration development. Our approach is to exploit the overall similarity among filamentous fungi using both a plant pathogen (Colletotricum trifolii) and a model system that is genetically sophisticated (Neurospora crassa). The simulataneous use of two organisms has the advantage of the available tools in Neurospora to rapidly advance the functional analysis of genes involved in spore germination and development of an economically important fungal phytopathogen. Towards this we have isolated a protein kinase gene from C. trifolii (TB3) that is maximally expressed during the first hour of conidial germination and prior to any visible gene tube formation. Based on sequence similarities with other organisms, this gene is likely to be involved in the proliferative response in the fungus. In addition, TB3 was able to functionally complement a N. crassa mutant (COT-1). Pharmacological studies indicated the importance of calmodulin in both germination and appressorium differentiation. Using an antisense vector from N. crassa, direct inhibition of calmodulin results in prevention of differentiation as well as pathogenicity. Both cAMP dependent protein kinase (PKA) and protein kinase C (PKC) like genes have been cloned from C. trifolii. Biochemical inhibition of PKA prevents germination; biochemical inhibitors of PKC prevents appressorium differentiation. In order to analyze reversible phosphorylation as a regulatory mechanism, some ser.thr dephosphorylative events have also been analyzed. Type 2A and Type 2B (calcineurin) phosphatases have been identified and structurally and functionally analyzed in N. crassa during this project. Both phosphatases are essential for hyphal growth and maintenance of proper hyphal architecture. In addition, a first novel-type (PPT/PP5-like) ser/thr phosphatase has been identified in a filamentous fungus. The highly collaborative project has improved our understanding of a fundamental process in fungi, and has identified targets which can be used to develop new approaches for control of fungal plant pathogens as well as improve the performance of beneficial fungi in the field and in industry. In addition, the feasibility of molecular technology transfer in comparative mycology has been demonstrated.

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