20 research outputs found
A molecular approach to biological control of mycotoxigenic fungi
No full textFood 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
Fusarium Toxins in Cereals: Occurrence, Legislation, Factors Promoting the Appearance and Their Management
No full textFusarium 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
Capacità di Trichoderma harzianum di indurre resistenza in mais limitando l’infezione da Fusarium verticillioides e l’accumulo di Fumonisine nella granella
No full textPathogenic and Genetic Characterization of Fusarium verticillioides Strains Collected from Maize and Sorghum Kernels
No full textCommercial and sanitary qualities of cereals are important and contribute to the determination of the final application and destination of the grain and, thus, farmer profit. Although considered a minor crop in Italy, in the last years, the cultivation area of sorghum (Sorghum bicolor L. Moench) has been increasing and is often adjacent or subsequent to the most common maize (Zea mays L.) fields, with the risk of sharing mycotoxigenic fungi that are common to both cereals, such as Fusarium verticillioides. The present work aims to clarify if a fungal physiological characteristic such as fumonisin production and some plant growth parameters such as effects on germination, root and shoot development and on tissue necrosis may be common and shared among F. verticillioides strains belonging to maize and sorghum, especially if present on adjacent fields at the same time. Sorghum kernels are commonly less colonized and contaminated by F. verticillioides and fumonisins than maize, and, at least in part, this aspect could be explained by the higher frequency of low-producing strains obtained from sorghum compared to those obtained from maize. Moreover, although no clear pathogen specificity was found, the results relating to the parameters analyzed suggest a host preference by F. verticillioides isolated from maize that affects maize seedlings with greater severity as well as F. verticillioides strains from sorghum versus sorghum. Five microsatellite markers showed minor differences between the two sets of strains but could not reliably discriminate between hosts. The resulting data suggest that in adjacent maize and sorghum crops, the population of F. verticillioides selected during sorghum cultivation may not represent a particular mycotoxigenic or pathogenic issue for maize cultivation
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
Plant 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
Effect of Naturally Occurring Compounds on Fumonisin Production and fum Gene Expression in Fusarium verticillioides
No full textFusarium verticillioides, one of the most common pathogens in maize, is responsible for yield losses and reduced kernel quality due to contamination by fumonisins (FBs). Two F. verticillioides isolates that differed in their ability to produce FBs were treated with a selection of eight natural phenolic compounds with the aim of identifying those that were able to decrease toxin production at concentrations that had a limited effect on fungal growth. Among the tested compounds, ellagic acid and isoeugenol, which turned out to be the most effective molecules against fungal growth, were assayed at lower concentrations, while the first retained its ability to inhibit toxin production in vitro, the latter improved both the fungal growth and FB accumulation. The effect of the most effective phenolic compounds on FB accumulation was also tested on maize kernels to highlight the importance of appropriate dosages in order to avoid conditions that are able to promote mycotoxin biosynthesis. An expression analysis of genes involved in FB production allowed more detailed insights into the mechanisms underlying the inhibition of FBs by phenolic compounds. The expression of the fum gene was generally down-regulated by the treatments; however, some treatments in the low-producing F. verticillioides strain up-regulated fum gene expression without improving FB production. This study showed that although different phenolic compounds are effective for FB reduction, they can modulate biosynthesis at the transcription level in opposite manners depending on strain. In conclusion, on the basis of in vitro and in vivo screening, two out of the eight tested phenols (ellagic acid and carvacrol) appear to be promising alternative molecules for the control of FB occurrence in maize
