Studies on the infection and parasitism course of sclerotia of Sclerotinia sclerotiorum by three different mycoparasites (original) (raw)
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Mycological Research, 2006
Mycoparasites Sclerotinia Sclerotium a b s t r a c t The gfp gene from the jellyfish Aequorea victoria, coding for the Green Fluorescent Protein (GFP), was used as a reporter gene to transform a Trichoderma virens strain I10, characterized as having a promising biocontrol activity against a large number of phytopathogenic fungi. On the basis of molecular and biological results, a stable GFP transformant was selected for further experiments. In order to evaluate the effects of GFP transformation on mycoparasitic ability of T. virens I10, sclerotia of Sclerotium rolfsii, Sclerotinia sclerotiorum and S. minor were inoculated with the T. virens strain I10 GFP transformant or the wild type strain. Statistical analysis of percentages of decayed sclerotia showed that the transformation of the antagonistic isolate with the GFP reporter gene did not modify mycoparasitic activity against sclerotia. Sclerotium colonization was followed by fluorescent microscopy revealing intracellular growth of the antagonist in the cortex (S. rolfsii) and inter-cellular growth in the medulla (S. rolfsii, and S. sclerotiorum). The uniformly distributed mycelium of T. virens just beneath the rind of sclerotia of both S. rolfsii and S. sclerotiorum suggests that the sclerotia became infected at numerous randomly distributed locations without any preferential point of entry. a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / m y c r e s m y c o l o g i c a l r e s e a r c h 1 1 0 ( 2 0 0 6 ) 179 -187
Mycological Research, 2005
The interactions between Pythium oligandrum hyphae and two types of sclerotia, i.e. the plano-convexoid sclerotium of Botrytis cinerea and the tuberoid sclerotium of Sclerotinia minor, were investigated by ultrastructural and cytochemical experiments. In the mycoparasitism of P. oligandrum, some differences in relation to sclerotium anatomy and the role of the rind layer in preventing invasion are documented. Both types of sclerotia showed neither alterations of the heavily melanised rind walls, nor direct rind wall penetration by P. oligandrum. This oomycete successfully entered B. cinerea sclerotia only through breaches at the junction of rind cells and corresponding to gaps in melanin deposits. On the other hand, none of these breaches was observed in the small sclerotia of S. minor, and P. oligandrum ingress in the sclerotia stopped at the inner rind layer. After the penetration of B. cinerea sclerotia by the mycoparasite, it extensively colonised the cortical and medulla areas by intercellular growth. The invaded tissues displayed pronounced alterations as well as some disorganisation of tissue in places. Colonisation was associated with severe chitin degradations of all host walls, which occurred even at some distance from P. oligandrum hyphae. The observation of wall thickenings in some P. oligandrum-hyphae suggests that the sclerotial cells constitute a harsh environment unsuitable for survival of the mycoparasite. These wall thickenings could be interpreted as P. oligandrum defence-like reactions.
IOBC/WPRS Bull, 2004
One hundred twenty-six isolates of Trichoderma spp., belonging to the fungal collection of the Department of Tree Science, Entomology and Plant Pathology "Giovanni Scaramuzzi", University of Pisa, were screened for their mycoparasitic ability against sclerotia of Sclerotium rolfsii and Sclerotinia sclerotiorum. Isolates belong to the Pachybasium, Longibrachiatum, and Trichoderma Sections and included THypocrea hunua and Trichoderma sp. An isolate of Clonostachys rosea was also tested. Some species were represented by only one strain. Mycoparasitic activity was expressed according to the percentage of decayed or infected sclerotia. Distribution of mycoparasitic ability according to the taxonomic position of Trichoderma spp. isolates was evaluated.
Parasitism of sclerotia of Sclerotium rolfsii by trichoderma harzianum
Soil Biology and Biochemistry, 1984
The ability of Trichotkrtrrtr hurziunutn isolate 203 to attack the soil-borne plant pathogen Sclerotiunl rol/,kii is apparently connected with the production by the isolates of chitinase and /I-( l.3)-glucanase inside the attacked sclerotia during parasitism.
Morphological and Patogenic Characterization of Sclerotinia sclerotiorum
Journal of Agricultural Science, 2019
White mold is a disease with a wide distribution worldwide. Temperatures between 18-23 °C and high humidity conditions favor the occurrence of the pathogen. For the control of the disease it is fundamental to understand the morphology and pathogenicity of the fungus. The objective of this study was to characterize the morphological and pathogenic characteristics of Sclerotinia sclerotiorum isolates from the state of Rio Grande do Sul. Sclerodes were disinfested, placed in the center of plates containing culture medium and incubated under controlled conditions. The evaluations were performed daily, during a period of 30 days, from the incubation of sclerotia. The experimental design was completely randomized, with four plaques per isolate, each plate one replicate. The characteristics evaluated for the mycelium characterization were: time required for the fungus to occupy the plate; density of the formed mycelium; coloration of the colonies and mycelial growth rate. Scleroderma a...
Soil Biology and Biochemistry, 1996
Hyphal interactions between the mycoparasite Trichoderma harzianum (BAFC Cult. No. 72) and the soilbome plant pathogenic fungus Sclerotinia sclerotiorum were investigated in dual culture and in sterilized soil, by light and scanning electron microscopy. In dual culture, T. harzianum hyphae grew towards and coiled around the S. sclerotiorurn hyphae. Dense coils of hyphae of T. harzianum and partial degradation of the Sclerotinia cell wall were observed in later stages of the parasitism. In sterile soil, conidia of T. harzianum germinated and the developing mycelium made contact with that of S. sclerotiorum, forming short branches and appressorium-like bodies which aided in holding and penetrating the host cell wall. An in vitro system was developed to test the ability of T. harzianum to control Sclerotinia wilt in cucumber and lettuce: coating seeds with T. harzianum conidia reduced the pre-and post-emergence effect of S. sclerotiorum in cucumber by 69 and SO%, respectively, and in lettuce by 46 and 72%, respectively. In the greenhouse, the disease caused by S. sclerotiorum in lettuce was reduced by treating seedlings with a peat-bran preparation of T. harzianum. Despite the non-significance of the reduction in disease, Trichoderma-treated lettuce seedlings were much more developed than controls. In sunflower, sgnificant reductions (in the range of 68 to 84%) in disease incidence were obtained by incorporating the peat-bran T. harzianum preparation into the seedling rooting mixture. Hyphal mycoparasitism, rather than sclerotial parasitism, is suggested to be the mechanism by which T. harzianutn controls S. xlerotiorum under these conditions.
The in vitro response of two Sclerotinia minor-, five S. sclerotiorum- and two Sclerotium cepivorum-isolates to 16 biological control agents and eight fungicides was evaluated. A split plot experimental design was used, with a factorial arrangement correction for each pathogen. Factor A corresponded to fungi isolates and Factor B to control agents. The comparison of means was carried out using a Tukey test (P<0.05), having 11 evaluations every 24 h of the Mycelial radial growth rates (Mrgr). In any case no effect was found, alone or in interactions with control agents. Dicloran, Benomyl, Tebuconazole and Cyprodinil- Fludioxonil inhibited the mycelial growth of all fungi with a final average of 1.0 Mrgr, and in greater proportion than biological agents (BA). The BA that propitiated the lesser mycelial growth towards S. minor were: Microorganisms (BPGPlus), Trichoderma sp. (Trichoderma), T. viride (Esporalis) and Bacillus subtillis (Serenade max); with isolates of S. sclerotiorum, Trichoderma sp. (Trichoderma), Trichoderma harzianum (Natucontrol), Microorganisms (BPG-Plus) and T. harzianum (Biotricho-H), with a Mrgr of 1.48, 1.56, 2.35 and 2.53, respectively. For S. cepivorum, the best management was obtained with Trichoderma sp. (Trichoderma), T. viride (Esporalis), T. harzianum (Natucontrol) and Microorganisms (BPG-plus), with a Mrgr of 1.03, 1.73, 2.55 and 2.70, respectively. In summary, Thichoderma sp. and Microorganisms were the most consistents in their ability to inhibit the three pathogens.
Pathogenicity variation and mycelia compatibility groups in Sclerotina sclerotiorum
Journal of Plant Protection Research, 2011
Population variability of S. sclerotiorum, the causal agent of Sclerotinia stalk rot of sunflower, was determined by mycelial compatibility grouping (MCG) and pathogenicity variation comparison. To study mycelial compatibility grouping and pathogenicity variability, isolates of S. sclerotiorum were collected from sunflower fields in East, West Azerbaijan and Ardebil provinces of Iran. Among 186 isolates tested, 26 MCGs were identified and 46% were represented by single isolates. There were differences among MCGs comparing mycelial growth rate, sclerotial production on PDA and aggressiveness cause disease. Significant differences were detected in number of sclerotia, dry weight of sclerotia, mycelial growth rate and aggressiveness among MCGs (p < 0.001) regardless of their geographic origins. There was generally a poor correlation (r = 0.21, p ≤ 0.05) between sclerotia weight and number of sclerotia produced on PDA and also to the mycelial growth rate at 24 (r = 0.35, p ≤ 0.05) and 48h (r = 0.39, p ≤ 0.05). Our studies in comparison of the detached leaf and cut-stem methods showed that the highest rank correlations (r = 0.78 p ≤ 0.01), while aggressiveness of two inoculation methods (stem and leaf detached) were not correlated to colony diameter growth or the other two factors. Variation in isolates aggressiveness may be important considerations in disease management systems.
Pathogenicity Variation and Mycelial Compatibility Groups in Sclerotinia Sclerotiorum
Journal of Plant Protection Research, 2011
Pathogenicity Variation and Mycelial Compatibility Groups inSclerotinia SclerotiorumPopulation variability ofS. sclerotiorum, the causal agent of Sclerotinia stalk rot of sunflower, was determined by mycelial compatibility grouping (MCG) and pathogenicity variation comparison. To study mycelial compatibility grouping and pathogenicity variability, isolates ofS. sclerotiorumwere collected from sunflower fields in East, West Azerbaijan and Ardebil provinces of Iran. Among 186 isolates tested, 26 MCGs were identified and 46% were represented by single isolates. There were differences among MCGs comparing mycelial growth rate, sclerotial production on PDA and aggressiveness cause disease. Significant differences were detected in number of sclerotia, dry weight of sclerotia, mycelial growth rate and aggressiveness among MCGs (p < 0.001) regardless of their geographic origins. There was generally a poor correlation (r = 0.21, p ≤ 0.05) between sclerotia weight and number of sclerotia p...
A method for selecting Trichoderma strains antagonistic against Sclerotinia minor
Microbiological Research, 1995
Thirty strains of T. hamatum, T. harzianum, T. koningii, T. longibrachiatum and T. viride were selected for in vitro mycoparasitic activity against Sclerotinia minor. High destruction of sclerotia (up to 70% in two weeks) was caused by antagonists only at 25°C, in autoclaved soil, because the optimum temperature for radial growth of Trichoderma strains (25 -30°C) was significantly higher than those of phytophatogenic fungus (20°C). The most active strains, which were selected also for competitive saprophytic ability could enhance the percentage of decayed sclerotia 5 -9 fold over the control even after 1 week under non sterile conditions. A silicon rubber fixation technique was developed for recovery of irregularly shaped S. minor sclerotia.