Killer yeasts inhibit the growth of the phytopathogen Moniliophthora perniciosa, the causal agent of Witches' Broom disease (original) (raw)
Frontiers in Microbiology, 2021
Cacao plantations from South America have been afflicted with the severe fungal disease known as Witches’ Broom Disease (WBD), caused by the basidiomycete Moniliophthora perniciosa. Yeasts are increasingly recognized as good fungal biocides, although their application is still mostly restricted to the postharvest control of plant and fruit decay. Their possible utilization in the field, in a preharvest phase, is nevertheless promising, particularly if the strains are locally adapted and evolved and if they belong to species considered safe for man and the environment. In this work, a group of yeast strains originating from sugarcane-based fermentative processes in Brazil, the cacao-producing country where the disease is most severe, were tested for their ability to antagonize M. perniciosa in vitro. Wickerhamomyces anomalus LBCM1105 and Saccharomyces cerevisiae strains LBCM1112 from spontaneous fermentations used to produce cachaça, and PE2 widely used in Brazil in the industrial pr...
Frontiers in Microbiology, 2019
Plant diseases caused by fungal pathogens are responsible for major crop losses worldwide, with a significant socioeconomic impact on the life of millions of people who depend on agriculture-exclusive economy. This is the case of the Witches' Broom Disease (WBD) affecting cacao plant and fruit in South and Central America. The severity and extent of this disease is prospected to impact the growing global chocolate market in a few decades. WBD is caused by the basidiomycete fungus Moniliophthora perniciosa. The methods used to contain the fungus mainly rely on chemical fungicides, such as copper-based compounds or azoles. Not only are these highly ineffective, but also their utilization is increasingly restricted by the cacao industry, in part because it promotes fungal resistance, in part related to consumers' health concerns and environmental awareness. Therefore, the disease is being currently tentatively controlled through phytosanitary pruning, although the full removal of infected plant material is impossible and the fungus maintains persistent inoculum in the soil, or using an endophytic fungal parasite of Moniliophthora perniciosa which production is not sustainable. The growth of Moniliophthora perniciosa was reported as being antagonized in vitro by some yeasts, which suggests that they could be used as biological control agents, suppressing the fungus multiplication and containing its spread. Concurrently, some yeast-based products are used in the protection of fruits from postharvest fungal spoilage, and the extension of diverse food products shelf-life. These successful applications suggest that yeasts can be regarded a serious alternative also in the pre-harvest management of WBD and other fungal plant diseases. Yeasts' GRAS (Generally Recognized as Safe) nature adds to their appropriateness for field application, not raising major ecological concerns as do the present more aggressive
Interactions between killer yeasts and pathogenic fungi
FEMS Microbiology Letters, 1995
A total of 17 presumptive killer yeast strains were tested in vitro for growth inhibitory and killing activity against a range of fungal pathogens of agronomic, environmental and clinical significance. Several yeasts were identified which displayed significant activity against important pathogenic fungi. For example, isolates of the opportunistic human pathogen, Candida albicans, were generally very sensitive to Williopsis mrakii killer yeast activity, whilst killer strains of Succharomyces cerevisiae and Pichia anontala markedly inhibited the growth of certain wood decay basidiomycetes and plant pathogenic fungi. Results indicate that such yeasts, together with their killer toxins, may have potential as novel antimycotic biocontrol agents.
The occurrence of killer activity in yeasts isolated from natural habitats
Acta Biochimica Polonica, 2015
Yeast's ability to restrict the growth and kill other yeasts, fungi and bacteria has been known for over 50 years. Killer activity was detected in yeasts deposited in the world collections or isolated from natural habitats. In this study, isolates from the forest environment, leaves of fruit trees, flower petals, cereals and frozen fruit have been screened in terms of their killer activities. Killer activity was tested on strains belonging to six yeast species: Candida, Rhodotorula, Pichia, Pachysolen, Yarrowia, Trichosporon. The reference strains were Kluyveromyces lactis Y-6682 and Kluyveromyces marxinanus Y-8281, wellknown to be sensitive to yeast killer toxins. Among one hundred and two tested strains, 24 (23.5% of isolates) showed positive killer action, and 10 (9.8% of the isolates) a weak killer action against at least one sensitive reference strain. The highest killer activity was observed among isolates from forest soil and flowers.
Polish journal of microbiology / Polskie Towarzystwo Mikrobiologów = The Polish Society of Microbiologists, 2007
Twenty-five yeast cultures, mainly of human origin, belonging to four pathogenic yeast species--Candida albicans, Candida krusei, Candida parapsilosis, and Candida tropicalis were tested for their sensitivity to ten basidiomycetous and eleven ascomycetous yeast species isolated from the water and soil environments and from tree leaves. The best killer activity among basidiomycetous species was exhibited by Rhodotorula glutinis, and R. mucilaginosa. The other carotenoid producing species Cystofilobasidium capitatum, Sporobolomyces salmonicolor, and S. roseus were active only against about 40% of the tested strains and exhibited weak activity. The broadest killer activity among ascomycetous yeasts was shown by the strains Pichia anomala and Metschnikowia pulcherrima. The species Debaryomyces castellii, Debaryomyces hansenii, Hanseniaspora guilliermondii, Pichia membranifaciens, and Williopsis californica did not show any killer activity. The best killer activity exhibited the strains ...
Study of antagonistic yeasts isolated from some natural sources of West Bengal
Agriculture and Biology Journal of North America, 2013
An intensive survey was conducted and 196 samples were collected from different zones of 12 districts of West Bengal. The collected samples were various fruits (apple , green grapes. brown grapes , date fruits , jamun and fig) ,juices (date juice , toddy , cane juice) and milk. From these samples 588 yeast colonies were isolated .These yeasts were identified by conventional morphological, microscopical and biochemical testing methods. These colonies comprise of 23 genera and 38 species of yeasts. Out of 38 isolated & identified species, 26 are ascomycetous while 12 are basidiomycetous yeasts .Maximum number of species were found in Candida (5) and followed by Pichia(4), Rhodotorula(3) and Saccharomyces (2).The percent of occurrence , Berger-Parker dominance index of each species were calculated. All yeast species isolated were screened by dual culture plate method for their antagonistic property against Penicillium digitatum, causal pathogen of Penicillium rot of Citrus. Out of 38 species of yeasts,15 species were antagonistic to Penicillium digitatum. Candida famata gave maximum percent of radial inhibition (70.24 PIRG)followed by Pichia membranifaciens (68.21PIRG) and Rhodotorula mucilaginosa (60.56 PIRG).Therefore , these natural sources of West Bengal are good habitats of various yeast species including antagonistic yeasts and the antagonistic yeasts can be applied as biological control agents against post harvest Penicillium rot disease of Citrus
Journal of Industrial Microbiology and Biotechnology, 1999
The yeasts Rhodotorula glutinis (LS-11), Cryptococcus laurentii (LS-28), Candida famata (21-D) and Pichia guilliermondii (29-A) and the yeast-like fungus Aureobasidium pullulans (LS-30), previously selected and characterized for mechanisms of action and antagonistic activity against postharvest pathogens in small and large-scale experiments, were used in this study in order to assess interrelationships among the main factors (antagonist, host fruit and fungal pathogen) involved in biological control of postharvest diseases. The antagonists were evaluated for their inhibitory activity (IA) against six common postharvest fungal pathogens on six different host fruits. Artificially wounded fruits were first inoculated with the antagonist and 2 h later with the pathogen; subsequently they were kept at 20°C for 4-6 days. The IA of each antagonist was evaluated and data were submitted to factorial analysis of variance. The populations of antagonists were also monitored on wounded and unwounded fruits kept at 20°C for 7 days. Each factor examined (antagonist, host fruit and fungal pathogen) as well as their interactions significantly affected the IA. However, among the antagonists, isolates LS-28 and LS-30 were only slightly affected by both host and pathogen, showing a wide range of activity, whereas isolate LS-11 had a variable IA. All the antagonists rapidly colonized the wounds, while their population remained substantially unchanged on unwounded fruits. These results suggest that in order to select yeasts with a broad spectrum of action, more suitable for commercial development, it would be advantageous to perform preliminary assays against several pathogens and in particular on different fruit species.
Biological Control, 1996
Twenty-eight yeasts isolated from habitats other than apple were screened for their potential to protect wounds of Golden Delicious apples during storage from gray mold caused by Botrytis cinerea. All isolates reduced (P F 0.05) decay severity and 23 reduced decay incidence after 7 days at 22-24°C when applied at 5 3 10 6 CFU per wound 1-2 h earlier than 8 3 10 3 conidia of B. cinerea (P F 0.05). When selected isolates were tested at 5 3 10 5 CFU per wound on apples stored for 30 days at 4°C, Cryptococcus humicola NRRL Y1266, Filobasidium floriforme NRRL Y7454, and Rhodosporidium toruloides NRRL Y1091, previously unreported gray mold antagonists, reduced both incidence and decay severity as well as chlorothalonil and Sporobolomyces roseus FS-43-238, a reported biocontrol agent. Experiments at 22-24°C indicated that, with the exception of R. toruloides, protection generally required yeast inoculation into wounds before conidia. Nine yeasts protected wounds at 5 3 10 6 CFU per wound, whereas only three of nine were effective at 5 3 10 2 CFU per wound, a density calculated to be too low to preemptively carpet the wound, even though selected yeasts increased at least one log unit in the first 24 h following inoculation into wounds. In vitro utilization of 14 Clabeled sucrose by the yeasts was greater than that by the conidia after 12-48 h incubation, supporting nutrient competition as a mechanism of antagonism. Cellfree, dilute sucrose solutions that were preincubated with effective biocontrol yeasts for 24 h significantly inhibited conidium germination; however, a solution preincubated with a sucrose-utilizing but less effective yeast did not. Results suggest that nutrient competition may have played a significant role in biocontrol, but the contribution of preemptive physical exclusion and antifungal metabolites to a complex biocontrol process cannot be dismissed. r