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A molecular approach to biological control of mycotoxigenic fungi
Get PDFFood safety has become a worldwide priority in public health. Among the most important food threats, mycotoxin contamination in agricultural products represents a past, daily and incoming problem to solve. Mycotoxins are chemical compounds produced by a large variety of Fungi with very different hosts and climatic needs. In European countries, climatic conditions lead to the development of different mycotoxigenic fungi. Climate conditions of Mediterranean basin promote the development, among all, of Fusarium verticillioides in maize and Aspergillus carbonarius in grape, responsible for the production of fumonisins and ochratoxins respectively. Treatments with many synthetic chemical compounds have been proved to reduce the contamination levels but economical, ecological and nutritional aspects in public opinion, lead to attempt new strategies, as biological control. The state of art for mycotoxins production and regulation is very diversified according to the importance of economical threat, so while fumonisins are well studied, the knowledge on ochratoxins presents many gaps. In the present work, molecular approaches as enzymatic activity, Real-Time PCR and cDNA-AFLP have been used to provide useful knowledge and strategies to biological control of mycotoxigenic fungi. First, the ability of Trichoderma harzianum T22 to induce resistance in maize against Fusarium verticillioides was evaluated, pointing out the decrease of fumonisin accumulation in field trials. The second section improved the importance of reactive oxygen species for initiation and modulation of fumonisin biosynthesis in F. verticillioides supporting the hypothesis that plant stresses promote fumonisins accumulation in kernels. Finally, in the latter part, 119 differentially expressed sequences by Aspergillus carbonarius gave an important contribution to the understanding of OTA biosynthesis suggesting, according to the up- and down-regulation patterns, a possible model for OTA biosynthesis and regulation.La sicurezza alimentare è oggigiorno considerata una priorità a livello mondiale. Tra le principali minacce legate al settore alimentare, le micotossine rappresentano una problematica da contenere e risolvere. Le micotossine sono sostanze chimiche prodotte dal metabolismo secondario di alcuni funghi con ospiti e necessità climatiche molto diversi tra loro. Diverse condizioni climatiche portano alla sviluppo di funghi capaci di produrre diverse micotossine e per i paesi affacciati sul bacino mediterraneo, due tra i funghi micotossigeni più presenti risultano essere Fusarium verticillioides in mais e Aspergillus carbonarius sull’uva, responsabili dell’accumulo rispettivamente di fumonisine e ocratossina A. I trattamenti effettuati con composti chimici hanno dato prova di essere parzialmente efficaci nel ridurre i livelli di contaminazione, ciononostante i vari aspetti economici, ecologici e di salubrità dovrebbero condurre allo sviluppo di nuove strategie a basso impatto come il controllo biologico. Le conoscenze finora ottenute sulla produzione e la regolazione delle micotossine sono molto diversificate in base all’importanza economica che queste rivestono, mentre le fumonisine sono ben studiate, le informazioni riguardanti le ocratossine sono ancora lacunose. Nel presente lavoro diversi approcci molecolari quali studi di attività enzimatica, Real-Time PCR e cDNA-AFLP sono stati utilizzati per fornire elementi e strategie utili al controllo biologico dei funghi micotossigeni. Nella prima parte del presente lavoro è stata valutata la capacità di Trichoderma harzianum T22 di indurre resistenza in mais nei confronti di F. verticillioides evidenziando in particolar modo l’abbattimento del contenuto di fumonisine nella granella raccolta. La seconda parte è focalizzata sui cambiamenti indotti dalle specie reattive dell’ossigeno su F. verticillioides, confermando anche per questo fungo l’importanza dei ROS nell’attivazione e la modulazione della biosintesi delle fumonisine. Tali risultati supportano l’ipotesi che l’accumulo di fumonisine sia fortemente influenzato dalle situazioni di stress percepite dalla pianta. Infine, lo studio svolto sulle sequenze differentemente espresse di A. carbonarius rappresenta un importante contributo alla comprensione della pathway biosintetica suggerendo, in accordo con i diversi pattern di espressione, un possibile modello di regolazione e biosintesi dell’ocratossina A
Capacità di Trichoderma harzianum di indurre resistenza in mais limitando l’infezione da Fusarium verticillioides e l’accumulo di Fumonisine nella granella
No full textPlant stress and mycotoxin accumulation in maize
No full textThe 2012 crop year in north-east Italy was characterized by a strong heat-wave event, and areas influenced by this environmental condition presented an anomalous accumulation of mycotoxins in maize. Mycotoxins are secondary metabolites, harmful to human and animals, produced by pathogenic fungi that contaminate foodstuffs. Plants suffering by stress are characterized by lower crop yield and quality, increased fungal infection and in some cases by higher amounts of mycotoxins. In plant, heat-wave events and generally stress factors afflict physiological traits and are associated with oxidative stress. Since oxidative stress is fundamental also for activation of mycotoxin biosynthesis in fungi, stress conditions in plant and mycotoxin accumulation are often correlated. The present paper aims to report the influence of some stress factors in relation to mycotoxin accumulation providing further data to comprehension of stress management with particular emphasis to heat-wave related events
Trichoderma harzianum strains T22 and T39 induce in maize systemic resistance against Fusarium verticillioides
No full textTRICHODERMA HARZIANUM T22 INDUCES IN MAIZE SYSTEMIC RESISTANCE AGAINST FUSARIUM VERTICILLIOIDES
No full textFusarium verticillioides is one of the most common
plant pathogenic fungi affecting maize causing ear and
kernel rot. Nearly the totality of the fungal strains are able
to produce mycotoxins known as fumonisins at very different
levels. However, information on the ability of the
biocontrol fungus Trichoderma harzianum to induce systemic
resistance in maize against F. verticillioides is still
lacking. We now show that, upon root colonization by T.
harzianum, F. verticillioides consistently reduces maize disease
symptoms. The enhanced activation of SA- and JA/
ET-dependent defence responses indicates that resistance
in maize is caused by a better perception of the fungal
pathogen due to the effect of Trichoderma inocula. Seed
biopriming with T. harzianum could be a useful strategy to
control F. verticillioides infection and fumonisin accumulation
under field conditions
Trichoderma harzianum seed treatment controls Fusarium verticillioides colonization and fumonisin contamination in maize under field conditions
No full textIn northern Italy, the most frequently occurring class of mycotoxins in maize are fumonisins, mainly those produced by Fusarium verticillioides. Currently, good agricultural practices (GAPs) represent the best line of defense for controlling the contamination of maize by Fusarium-toxins. Annual fluctuations in weather conditions can strongly reduce the advantages conferred by GAPs, and thus integration with biological control strategies can be a sustainable way to achieve reliable control of Fusarium colonization and toxin contamination. Trichoderma harzianum is a good biocontrol agent against a wide range of plant pathogens, and previous studies have reported its ability to reduce F. verticillioides colonization under greenhouse conditions. Field trials were conducted in two locations to assess the effect of seed treatment with T. harzianum strain T22 on F. verticillioides kernel colonization and on fumonisin contamination under various natural conditions. An average reduction of 58% in fungal infestation and 53% in mycotoxin contamination was observed during our three-year experiments. This research suggests that seed biopriming with T. harzianum T22 can be a promising and environmentally friendly way to control F. verticillioides kernel colonization and fumonisin accumulation
Fusarium Toxins in Cereals: Occurrence, Legislation, Factors Promoting the Appearance and Their Management
Get PDFFusarium diseases of small grain cereals and maize cause significant yield losses worldwide. Fusarium infections result in reduced grain yield and contamination with mycotoxins, some of which have a notable impact on human and animal health. Regulations on maximum limits have been established in various countries to protect consumers from the harmful effects of these mycotoxins. Several factors are involved in Fusarium disease and mycotoxin occurrence and among them environmental factors and the agronomic practices have been shown to deeply affect mycotoxin contamination in the field. In the present review particular emphasis will be placed on how environmental conditions and stress factors for the crops can affect Fusarium infection and mycotoxin production, with the aim to provide useful knowledge to develop strategies to prevent mycotoxin accumulation in cereals
Effect of potential biocontrol agents selected among grapevine endophytes and commercial products on crown gall disease
No full textThe current strategies for the control of
Agrobacterium vitis crown gall in grape are generally
unsuccessful once the pathogen has established in
vineyards. Experimental trials were conducted to
evaluate the effectiveness of treatments based on nonpathogenic
endophytes isolated from asymptomatic
grapevines growing in vineyards with high incidence
of crown gall and on microorganisms isolated from
commercial products. Two-year in planta trials conducted
on rootstocks treated with endophytic isolates
showed the effectiveness of two bacterial endophytes,
both in the genus Curtobacterium, and one fungal
isolate in the genus Acremonium in reducing crown
gall development. For the commercial biological
control agents, Bacillus subtilis SR63 and Trichoderma
asperellum T1 were the most effective strains
against A. vitis, indicating commercial products could
be reserves to draw upon to identify useful biocontrol
agents. Based on the combination of data in this work,microorganisms, both endophytes and those formulated
in commercial products, were identified that can
potentially be exploited for the control of grapevine
crown gall disease
A cDNA-AFLP approach to study ochratoxin A production in Aspergillus carbonarius
No full textAspergillus carbonarius is responsible for the majority of mycotoxin contaminations in grapes and its derivatives. Most of A. carbonarius strains are ochratoxin A (OTA) producers, even though at very different levels. This broad variability was used to identify genes whose expression is linked with the ability of producing OTA. A cDNA-AFLP differential display screening was performed in two strains of A. carbonarius, antagonists for the ability of producing OTA, allowing the identification of 119 differentially expressed sequences putatively involved in the regulation of OTA biosynthesis. A likely connection was pointed out between the biosynthesis of the toxin, vegetative growth and sexual/asexual developmental progression, along with common signalling pathways involving G protein and Ca2+/calmodulin dependent phosphorylation and dephoshorylation cascades
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