In vitro attachment of phylloplane yeasts to Botrytis cinerea, Rhizoctonia solani, and Sclerotinia homoeocarpa

2004 ◽  
Vol 50 (12) ◽  
pp. 1041-1048 ◽  
Author(s):  
Tom W Allen ◽  
Leon L Burpee ◽  
James W Buck
Keyword(s):  
Rhizoctonia Solani ◽  
Botrytis Cinerea ◽  
Rhodotorula Glutinis ◽  
Extracellular Polysaccharide ◽  
Phytopathogenic Fungi ◽  
Yeast Cells ◽  
Cryptococcus Laurentii ◽  
Sclerotinia Homoeocarpa ◽  
Phylloplane Yeasts

The ability of yeasts to attach to hyphae or conidia of phytopathogenic fungi has been speculated to contribute to biocontrol activity on plant surfaces. Attachment of phylloplane yeasts to Botrytis cinerea, Rhizoctonia solani, and Sclerotinia homoeocarpa was determined using in vitro attachment assays. Yeasts were incubated for 2 d on potato dextrose agar (PDA) prior to experimentation. A total of 292 yeasts cultured on PDA were screened for their ability to attach to conidia of B. cinerea; 260 isolates (89.1%) attached to conidia forming large aggregates of cells, and 22 isolates (7.5%) weakly attached to conidia with 1 or 2 yeast cells attached to a few conidia. Ten yeasts (3.4%), including 8 isolates of Cryptococcus laurentii, 1 isolate of Cryptococcus flavescens, and an unidentified species of Cryptococcus, failed to attach to conidia. All non-attaching yeasts produced copious extracellular polysaccharide (EPS) on PDA. Seventeen yeast isolates did not attach to hyphal fragments of B. cinerea, R. solani, and S. homoeocarpa after a 1 h incubation, but attachment was observed after 24 h. Culture medium, but not culture age, significantly affected the attachment of yeast cells to conidia of B. cinerea. The 10 yeast isolates that did not attach to conidia when grown on agar did attach to conidia (20%–57% of conidia with attached yeast cells) when cultured in liquid medium. Attachment of the biocontrol yeast Rhodotorula glutinis PM4 to conidia of B. cinerea was significantly greater at 1 × 107 yeast cells·mL–1 than at lower concentrations of yeast cells. The ability of yeast cells to attach to fungal conidia or hyphae appears to be a common phenotype among phylloplane yeasts.Key words: adhesion, biological control, Cryptococcus laurentii, Rhodotorula glutinis.

scholarly journals Effect of the Biocontrol Yeast Rhodotorula glutinis Strain LS11 on Patulin Accumulation in Stored Apples

2005 ◽  
Vol 95 (11) ◽  
pp. 1271-1278 ◽  
Author(s):  
Raffaello Castoria ◽  
Valeria Morena ◽  
Leonardo Caputo ◽  
Gianfranco Panfili ◽  
Filippo De Curtis ◽  
...  
Keyword(s):  
Rhodotorula Glutinis ◽  
Biocontrol Agents ◽  
Yeast Cells ◽  
Penicillium Expansum ◽  
Cryptococcus Laurentii ◽  
Fungicide Residues ◽  
Tlc Plates ◽  
Layer Chromatography

Contamination of apples (Malus domestica) and derived juices with fungicide residues and patulin produced by Penicillium expansum are major issues of food safety. Biocontrol agents represent an alternative or supplement to chemicals for disease control. Our data show that these microbes could also contribute to actively decreasing patulin accumulation in apples. Three biocontrol agents, Rhodotorula glutinis LS11, Cryptococcus laurentii LS28, and Aureobasidium pullulans LS30, were examined for their in vitro growth in the presence of patulin and for their capability to decrease mycotoxin recovery from the medium. Strain LS11 yielded the highest growth rates and the greatest decrease of toxin recoveries. Further, it caused the appearance of two major spots on thin-layer chromatography (TLC) plates, suggesting possible metabolization of the mycotoxin. In vivo, i.e., in the low percentage of LS11-pretreated apples infected by P. expansum, patulin accumulation was significantly lower than in nontreated infected fruits. Yeast cells survived and increased in infected apples and, in a model system emulating decaying apple, resulted in accelerated breakdown of patulin and the production of the same TLC spots as those detected in vitro. These data suggest that biocontrol yeast cells surviving in decaying apples could metabolize patulin and/or negatively affect its accumulation or synthesis. To our knowledge, this is the first report describing the effect of a biocontrol agent on patulin accumulation in vivo.

scholarly journals Combinations of Fungicides with Phylloplane Yeasts for Improved Control of Botrytis cinerea on Geranium Seedlings

2004 ◽  
Vol 94 (2) ◽  
pp. 196-202 ◽  
Author(s):  
J. W. Buck
Keyword(s):  
Disease Control ◽  
Botrytis Cinerea ◽  
Ornamental Plants ◽  
Rhodotorula Glutinis ◽  
Lesion Development ◽  
Biocontrol Efficacy ◽  
Highly Effective ◽  
Cell Densities ◽  
Phylloplane Yeasts

Control of Botrytis cinerea on geranium seedlings was evaluated in treatments with phylloplane yeasts in combination with 10 fungicides used to manage Botrytis blight of ornamental plants. Rhodotorula glutinis PM4 significantly reduced the development of lesions caused by B. cinerea on geranium cotyledons; however, yeast biocontrol efficacy was highly variable between trials. Treatment with the yeast in combination with azoxystrobin or trifloxystrobin at one tenth the labeled rate (7.5 μg a.i. ml-1) or the full labeled rate (7.5 μg a.i. ml-1) reduced lesion development, compared to treatment with the yeast or the fungicide alone. Vinclozolin at half the labeled rate or the full labeled rate (250 or 500 μg a.i. ml-1), in combination with R. glutinis PM4, significantly reduced the development of lesions caused by an isolate of B. cinerea resistant to vinclozolin. Copper hydroxide and iprodione at one-tenth the labeled rates, with or without yeast, were highly effective in limiting lesion development. Mancozeb did not increase the biocontrol efficacy of the yeast, and thiophanate-methyl negatively affected the yeast efficacy. Improved disease control was observed in treatments with vinclozolin at the labeled rate and R. glutinis PM4 at cell densities of 5 × 105 and 1 × 106 cells ml-1, but not 1 × 105 cells ml-1, on seedlings co-inoculated with B. cinerea in a suspension containing 1 × 105 conidia ml-1. Disease control improved in treatments with combinations of vinclozolin and eight other isolates of R. glutinis, two isolates of R. graminis, and two isolates of R. mucilaginosa. Biocontrol was not observed in treatments with two isolates of R. minuta. The combination of yeast and vinclozolin significantly reduced the germination of conidia of B. cinerea and the growth of R. glutinis PM4 in vitro. All combinations of R. glutinis PM4 with azoxystrobin, trifloxystrobin, or vinclozolin provided highly effective and consistent disease control not observed in treatments with the fungicides alone or the yeast alone.

Responses of 2 epiphytic yeasts to foliar infection by Rhizoctonia solani or mechanical wounding on the phylloplane of tall fescue

2009 ◽  
Vol 55 (10) ◽  
pp. 1160-1165 ◽  
Author(s):  
Shannon Nix ◽  
Leon L. Burpee ◽  
James W. Buck
Keyword(s):  
Rhizoctonia Solani ◽  
Tall Fescue ◽  
Festuca Arundinacea ◽  
Yeast Species ◽  
Leaf Tissue ◽  
Rhodotorula Glutinis ◽  
Cryptococcus Laurentii ◽  
Mechanical Wounding ◽  
Colony Forming Units ◽  
Phylloplane Yeasts

A growth-chamber experiment was conducted to determine how foliar disease or wounding affects the ability of 2 phylloplane yeasts ( Rhodotorula glutinis and Cryptococcus laurentii ) to colonize leaves of tall fescue ( Festuca arundinacea ). Yeasts were applied separately and together onto healthy leaves, leaves infected with Rhizoctonia solani (diseased), and mechanically bruised (wounded) leaves. In all 3 trials, the leaf disturbance treatment significantly affected the abundance of yeast on the phylloplane of tall fescue. Yeast abundance on the diseased or wounded leaves was significantly greater than on the nontreated, healthy leaves. In 2 of the 3 trials, the yeast species applied also had a significant affect on yeast abundance. Typically, R. glutinis was significantly more abundant than C. laurentii when applied individually, but not significantly greater than the total yeast colony-forming units of the co-inoculated treatment. When the 2 yeasts were co-inoculated onto the leaves, R. glutinis comprised 89.7%, 75.4%, and 67.6% of the recovered yeast colony-forming units on healthy, diseased, and wounded leaves, respectfully. Our data suggest that these 2 species of yeasts will differentially colonize compromised leaf tissue with disease or wounds favoring populations of R. glutinis over C. laurentii.

In vitro antagonism of Botrytis cinerea by phylloplane yeasts

2002 ◽  
Vol 80 (8) ◽  
pp. 885-891 ◽  
Author(s):  
James W Buck
Keyword(s):  
Botrytis Cinerea ◽  
Rhodosporidium Toruloides ◽  
Yeast Cells ◽  
Lesion Development ◽  
Nitrogen Base ◽  
Wide Range ◽  
Biocontrol Activity ◽  
Phylloplane Yeasts ◽  
Leaf Disks

The influence of inoculum and nutrient concentrations on the in vitro antagonism of Botrytis cinerea by phylloplane yeasts was investigated with detached leaf disk and conidial germination assays. Rhodosporidium toruloides Y-1091 significantly reduced lesion development after 96 h on geranium leaf disks when co-inoculated at 1 × 106 or 1 × 107 yeast cells/mL with B. cinerea conidia at 1 × 104 or 1 × 105 conidia/mL. No effect on lesion development was observed when yeast and fungus were co-inoculated at a 1:1 ratio. Biocontrol activity of R. toruloides was greatest in 20 mM glucose and 20-fold dilute yeast nitrogen base. Twenty-five phylloplane yeasts exhibited a wide range of biocontrol activity when screened for antagonism of B. cinerea on geranium leaf disks (1 × 106 yeast cells/mL, 1 × 105 conidia/mL). Lesion development was significantly reduced by yeasts initially identified as poor antagonists when inoculated at higher concentrations (5 × 106 or 1 × 107 yeast cells/mL) with B. cinerea. Both poor and good antagonists significantly reduced in vitro germination of B. cinerea conidia. The presence of B. cinerea conidia had a greater effect on the growth of two poor antagonists compared with two good antagonists on leaf disks. These data suggest that many phylloplane yeasts will antagonize B. cinerea under conditions of low nutrient availability and with high antagonist to pathogen ratios.Key words: yeast, biological control, competition, nutrients, germination, Rhodosporidium toruloides.

Role of chitinase and β-1,3-glucanase activities produced by a fluorescent pseudomonad and in vitro inhibition of Phytophthora capsici and Rhizoctonia solani

2007 ◽  
Vol 53 (2) ◽  
pp. 207-212 ◽  
Author(s):  
Naveen Kumar Arora ◽  
Min Jeong Kim ◽  
Sun Chul Kang ◽  
Dinesh Kumar Maheshwari
Keyword(s):  
Rhizoctonia Solani ◽  
Phytophthora Capsici ◽  
Phytopathogenic Fungi ◽  
Culture Technique ◽  
Dual Culture ◽  
Fluorescent Pseudomonad ◽  
Antifungal Metabolites ◽  
Fluorescent Pseudomonas

A study was conducted to investigate the possibility of involvement of chitinase and β-1,3-glucanase of an antagonistic fluorescent Pseudomonas in growth suppression of phytopathogenic fungi, Phytophthora capsici and Rhizoctonia solani . Fluorescent Pseudomonas isolates GRC3 and GRC4 were screened for their antifungal potential against phytopathogenic fungi by using dual culture technique both on solid and liquid media. The percent inhibition was calculated. Various parameters were monitored for optimization of enzyme activities by fluorescent Pseudomonas GRC3. The involvement of chitinases, β-1,3-glucanases, and antifungal metabolites of nonenzymatic nature was correlated with the inhibition of P. capsici and R. solani. The results provide evidence for antibiosis as a mechanism for antagonism. The study also confirms that multiple mechanisms are involved in suppressing phytopathogens as evidenced by the involvement of chitinase and β-1,3-glucanase in inhibition of R. solani but not P. capsici by isolate GRC3.

scholarly journals In vitro study of baseline sensitivity of important fungi against different fungicides

2012 ◽  
Vol 4 (2) ◽  
pp. 264-265 ◽  
Author(s):  
Sanjay Goswami ◽  
R. Kaur ◽  
Dipak T. Nagrale
Keyword(s):  
Botrytis Cinerea ◽  
Alternaria Alternata ◽  
In Vitro Study ◽  
Phytopathogenic Fungi ◽  
Plant Diseases ◽  
Baseline Sensitivity ◽  
Resistance Development ◽  
Gloeosporium Ampelophagum ◽  
Mic Value

Baseline sensitivity values of important phytopathogenic fungi were studied against fungicides. ED50, ED90 and MIC value of propiconazole for, Colletotrichum capsici, and Gloeosporium ampelophagum was in the range of 0.020-0.04 μg/ml. ED50 values of tebuconazole for Alternaria alternata was 30.0 μg/ml. Azoxystrobin was also tested for its ED50, ED90 and MIC values against Alternaria alternata, C. capsici, G. ampelophagum and Botrytis cinerea where the values were in the range of 0.019-50.0, 0.03-60.0 and 0.2-100.0 μg/ml respectively. Baseline sensitivity values are important for the management of plant diseases and resistance development.

scholarly journals Βιολογική αντιμετώπιση των ωχρατοξικογόνων μυκήτων Aspergillus niger και Aspergillus carbonarius στα σταφύλια με επιφυτικές ζύμες

2009 ◽  
Author(s):  
Μυρτώ-Αλεξάνδρα Δημακοπούλου-Κοντοσταύλου
Keyword(s):  
Aspergillus Niger ◽  
Botrytis Cinerea ◽  
Aureobasidium Pullulans ◽  
Cryptococcus Laurentii ◽  
Aspergillus Carbonarius ◽  
Aspergillus Sp

Η όξινη σήψη της αμπέλου οφείλεται σε ένα σύμπλοκο παθογόνων μικροοργανισμών, όπως βακτήρια και μύκητες, μεταξύ των οποίων συγκαταλέγονται μύκητες του γένους Aspergillus sp.. Οι κυριότεροι εξ αυτών είναι ο Aspergillus niger και ο Aspergillus carbonarius. Έχει αποδειχθεί ότι ο μύκητας Aspergillus carbonarius και δευτερευόντως ο Aspergillus niger ευθύνονται για την παραγωγή μεταξύ άλλων και της μυκοτοξίνης ωχρατοξίνη-Α. Η ωχρατοξίνη-Α έχει στον άνθρωπο δυσμενείς επιπτώσεις διότι προκαλεί καρκινογένεση, τερατογένεση, νεφροτοξικότητα, μείωση του ανοσοποιητικού συστήματος κ.α. Δεν αποδομείται στις υψηλές θερμοκρασίες και ανιχνεύεται πέρα των σταφυλιών στο γλεύκος και τον παραγόμενο οίνο. Στη παρούσα μελέτη έγινε προσπάθεια καταπολεμήσεως των δύο ωχρατοξικογόνων μυκήτων A. niger και του A. carbonarius με σκοπό την αντιμετώπιση της όξινης σήψεως και την ταυτόχρονη μείωση των επιπέδων της ωχρατοξίνης-Α. Ερευνητικά δεδομένα στη χώρα μας έχουν αποδείξει μείωση του πληθυσμού του Aspergillus carbonarius μετά τη χρήση του μυκητοκτόνου σκευάσματος Switch 25/37,5 που έχει έγκριση κυκλοφορίας στην χώρα μας για την αντιμετώπιση του μύκητα Botrytis cinerea στην άμπελο. Είναι γνωστό ότι διάφοροι επιφυτικοί μικροοργανισμοί, όπως βακτήρια ή μύκητες αντιμετωπίζουν παθογόνα κυρίως μετασυλλεκτικών ασθενειών τόσο σε πειραματικό όσο και σε εμπορικό επίπεδο. Λαμβάνοντας υπ’ όψιν τα ως άνω δεδομένα αυτά επιδιώχθηκε η διερεύνηση της υπάρξεως επιφυτικών ζυμών της αμπέλου ικανών να αντιμετωπίσουν την όξινη σήψη σε επίπεδα αντίστοιχα με εκείνα της χημικής καταπολεμήσεως και παράλληλα να μειώσουν/εξαλείψουν τη συσσώρευση ωχρατοξίνη-Α (ΟΤΑ) στο γλεύκος. Η συγκριτική μελέτη έγινε με το μυκητοκτόνο Switch, για το οποίο έχει ήδη αναφερθεί ότι μειώνει τους πληθυσμούς του Aspergillus carbonarius και εντάσσεται στα προγράμματα φυτοπροστασίας της αμπέλου για την καταπολέμηση της τεφράς σήψεως. Εκτός αυτού, σε ορισμένα από τα πειράματα αμπελώνα χρησιμοποιήθηκε και ένα σκεύασμα χαλκού με το σκεπτικό ότι η καλλιέργεια της αμπέλου δέχεται ψεκασμούς με χαλκούχα σκευάσματα. Από την εργασία μας διαπιστώθηκε, για πρώτη φορά διεθνώς ότι η εφαρμογή μιας επιφυτικής ζύμης μειώνει σε σημαντικό ποσοστό και αντίστοιχο της χημικής επεμβάσεως, τους πληθυσμούς του ωχρατοξικογόνου μύκητα Aspergillus carbonarius, όχι μόνο σε εργαστηριακό επίπεδο, αλλά και σε συνθήκες αμπελώνα και κυρίως ότι τούτο συνοδεύεται με σοβαρή μείωση των επιπέδων της ωχρατοξίνης-Α στο παραγόμενο γλεύκος. Το εργαστηριακό μέρος της μελέτης αυτής διεξήχθη στο Εργαστήριο Φυτοπαθολογίας του Γεωπονικού Πανεπιστημίου Αθηνών ενώ τα πειράματα αγρού σε πειραματικούς αμπελώνες σε Κορινθία και Ρόδο. Στη Κορινθία και συγκεκριμένα στην περιοχή της Νεμέας η διάρκεια των πειραμάτων στον αμπελώνα ήταν τριετής και στη Ρόδο στην περιοχή Φάνες τα πειράματα διήρκεσαν δύο έτη. Η μελέτη αυτή ακολούθησε τα εξής στάδια: α) απομόνωση επιφυτικών ζυμών από φύλλα αμπέλου, αξιολόγηση της ικανότητας τους να καταπολεμούν στο εργαστήριο σε μεμονωμένες ράγες σταφυλιού το μύκητα Aspergillus carbonarius και επιλογή των δύο αποτελεσματικότερων προς περαιτέρω πειραματισμό. β) έλεγχος της ευαισθησίας των συγκεκριμένων απομονώσεων ζυμών στο μυκητοκτόνο Switch 25/37,5 και συνεπώς την επιβίωσή τους μετά από επεμβάσεις του χημικού σκευάσματος, στον αγρό. γ) επεμβάσεις με τις ζύμες επί τρία συνεχή έτη σε αμπελώνα της περιοχής της Νεμέας και επί άλλα δύο σε δεύτερο αμπελώνα στη περιοχής «Φάνες» της νήσου Ρόδου, προς διερεύνηση της εκδηλώσεως ανάλογης αποτελεσματικότητας σε συνθήκες αγρού (διαφορετική καλλιεργούμενη ποικιλία, διαφορετικές κλιματολογικές συνθήκες, διαφορετικό σχήμα μορφώσεως των πρέμνων). δ) αξιολόγηση των ζυμών βάσει των ποσοστών: α) των βοτρύων με συμπτώματα όξινης σήψεως και β) των προσβεβλημένων ραγών με Aspergillus niger και Aspergillus carbonarius. ε) μελέτη in vitro της ευαισθησίας τυχαίων στελεχών Aspergillus sp. συλλεγέντων από τον αγρό στο μυκητοκτόνο Switch 25/37,5. ζ) μέτρηση της ωχρατοξίνης στο γλεύκος σταφυλιών που είχαν δεχθεί την επέμβαση ζύμης σε σύγκριση με εκείνο από σταφύλια που είχαν δεχθεί χημική επέμβαση. Από τα δεδομένα της διδακτορικής μου διατριβής παρέχεται η πληροφορία ότι οι αποτελεσματικές απομονώσεις ζυμών κατά του ωχρατοξικογόνου Aspergillus carbonarius στα σταφύλια δεν ανήκουν σε ένα συγκεκριμένο γένος καθότι η ταυτοποίηση έδειξε ότι η μία απομόνωση ανήκει στο είδος Cryptococcus laurentiì και η δεύτερη στο είδος Aureobasidium pullulans. Διαπιστώθηκε επίσης ότι οι περισσότερες επιφυτικές ζύμες είναι ανθεκτικές στα μυκητοκτόνα και κατά συνέπεια και οι υπάρχοντες φυσικοί πληθυσμοί τους στη φυλλόσφαιρα. Ενδεχομένως οι φυσικοί πληθυσμοί δεν ευρίσκονται πάντα στην απαραίτητη συγκέντρωση, για την βιολογική καταπολέμηση των Aspergillus sp.

Produktion pflanzlicher C6-Wundgase und ihre Wirkung auf einige phytopathogene Pilze / Production of C6-Wound Gases by Plants and the Effect on Some Phytopathogenic Fungi

1984 ◽  
Vol 39 (9-10) ◽  
pp. 1003-1007 ◽  
Author(s):  
Irene Urbasch
Keyword(s):  
Rhizoctonia Solani ◽  
Fusarium Oxysporum ◽  
Botrytis Cinerea ◽  
Phytopathogenic Fungi ◽  
Cladosporium Fulvum ◽  
Tomato Plants ◽  
Cyphomandra Betacea ◽  
Wild Tomato ◽  
Antifungal Properties ◽  
Tree Tomato

Abastract The production of C6-wound gases by cultivated and wild tomato plants (Lycopersicon esculenium Mill., L. hirsutum Humb. et Bonpl., L. peruvianum (L.) Mill., L. pimpinellifolium Mill., L. glandulosum C. H. Muller) and the tree tomato (Cyphomandra betacea (Cav.) Sendtn.) was investigated. The genuine mixture of compounds and the single compounds showed antifungal properties against the phytopathogenic fungi Botrytis cinerea Pers., Rhizoctonia solani Kühn, Fusarium oxysporum f. sp. lycopersici (Sacc.) Snyder & Hansen, Didymelia lycopersici Kleb, and Cladosporium fulvum Cooke.

scholarly journals Characterization of Botrytis cinerea from Table Grapes in Chile Using RAPD-PCR

Plant Disease ◽  
1999 ◽  
Vol 83 (12) ◽  
pp. 1090-1094 ◽  
Author(s):  
J. R. Thompson ◽  
B. A. Latorre
Keyword(s):  
Botrytis Cinerea ◽  
Rapd Analysis ◽  
Random Amplified Polymorphic Dna ◽  
Rhodotorula Glutinis ◽  
Test Sample ◽  
Vitis Vinifera L ◽  
Cryptococcus Laurentii ◽  
Similarity Coefficients ◽  
Table Grapes ◽  
Group I

Random amplified polymorphic DNA (RAPD) analysis was performed on 29 isolates of Botrytis cinerea Pers. ex Fr. isolated from table grapes (Vitis vinifera L.) and other crops in Chile with 29 decaprimers. No single primer was found to differentiate either the host or the geographical origin of each of the B. cinerea isolates tested. The DNA profiles obtained, particularly with primers OPA4 and OPA11, distinguished isolates of B. cinerea from other epiphyte fungi found on table grapes, including Alternaria alternata, Aspergillus niger, Cladosporium herbarum, Epiccocum nigrum, Rhizopus stolonifer, a Penicillium sp., and yeasts (Cryptococcus laurentii, Rhodotorula glutinis, and Saccharomyces cerevisiae). Regardless of host origin, primers OPA4 and OPA11 amplified a strong fragment of 1.2 kilobases (kb) and two fragments of 1.10 and 0.7 kb, respectively. These DNA fragments were obtained even when only one conidium of B. cinerea was in the test sample. Three main groups were clearly defined based on the genetic similarities found in additional RAPD analysis with 19 arbitrary decaprimers and 15 selected isolates of B. cinerea. The overall similarity coefficients (SC) between the groups obtained ranged from 0.326 to 0.891. Interestingly, all isolates from table grapes were included in group I (SC: 0.761 to 0.826), isolates from apple and tomato were in group II (SC: 0.739 to 0.848), while isolates from blueberry were either in group I (SC: 0.804) or III (SC: 0.673). Consequently, the genetic variability determined by RAPD analysis among these B. cinerea isolates suggested a possible host:pathogen relationship. However, further research is needed to clarify its pathological significance.

scholarly journals Effect of Pathogen Aggressiveness and Vinclozolin on Efficacy of Rhodotorula glutinis PM4 Against Botrytis cinerea on Geranium Leaf Disks and Seedlings

Plant Disease ◽  
2004 ◽  
Vol 88 (11) ◽  
pp. 1262-1268 ◽  
Author(s):  
J. W. Buck ◽  
S. N. Jeffers
Keyword(s):  
Botrytis Cinerea ◽  
Biological Control Agent ◽  
Rhodotorula Glutinis ◽  
Control Agent ◽  
Lesion Development ◽  
Biocontrol Efficacy ◽  
Lesion Diameter ◽  
Reduced Rate ◽  
Leaf Disks

Efficacy of the yeast Rhodotorula glutinis isolate PM4 as a biological control agent against 29 isolates of Botrytis cinerea obtained from greenhouse-grown ornamentals was assessed in vitro on geranium leaf disks. Isolates of B. cinerea varied in aggressiveness in the absence of either biological or chemical controls; diameters of lesions produced on leaf disks ranged from 0.8 to 12.3 mm. Efficacy of R. glutinis PM4 against the different isolates of B. cinerea varied greatly; lesion diameters ranged from 0.2 to 10.3 mm when the yeast was present. The yeast significantly reduced lesion development by 16 B. cinerea isolates in each of two replicate trials and by 9 isolates in one of the trials; however, 3 isolates were not inhibited by the yeast on geranium leaf disks. The yeast significantly reduced lesion development by B. cinerea isolate 01, used as a standard for comparison, in four of six trials. Fourteen of the B. cinerea isolates were inoculated onto geranium seedlings and produced a range of lesion sizes (2.9 to 16.4 mm), similar to that produced on leaf disks. Efficacy of the yeast in combination with a reduced rate (0.1×) of the fungicide vinclozolin (50 μg of active ingredient ml-1) was evaluated on geranium seedlings against 10 isolates of B. cinerea that were resistant to vinclozolin. Addition of vinclozolin to the yeast significantly reduced lesion diameter by five of the isolates compared with diameters of lesions produced in the presence of the yeast alone. Lesions produced by nine of the resistant isolates were 2.6 mm or smaller in both trials on plants treated with the mixture of yeast and vinclozolin. The effect of vinclozolin concentration (0 to 500 μg a.i. ml-1) on biocontrol efficacy of R. glutinis PM4 was evaluated using three resistant isolates of B. cinerea and geranium seedlings. Disease control was significantly better at higher concentrations of fungicide for two of the isolates. Linear regression of lesion diameter against vinclozolin concentration showed a significant effect on yeast biocontrol efficacy with B. cinerea isolate FL-2-b (y = 6.20 – 0.63x; r2= 0.74) and isolate BR-1 (y = 4.10 – 0.32x; r2 =0.28) but there was no significant effect with isolate GG-2-b. Overall, PM4 exhibited biocontrol activity on both geranium leaf disks and seedlings against a number of isolates of B. cinerea that varied in aggressiveness. Variability in biocontrol efficacy against isolates resistant to vinclozolin usually was reduced by the addition of vinclozolin.

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