Fusarium verticillioides contamination patterns in Northern Italian maize during the growing season

Fusarium verticillioides, often found in maize kernels, is the major fungal colonizer of maize in Northern Italy. The fungus can cause plant diseases, or grow endophytically and synthetize mycotoxins. Ear rot caused by F. verticillioides may reduce crop yield. Fumonisins produced by the fungus may harm humans and animals. In order to gather information on contamination patterns of F. verticillioides under field conditions, the current study assessed the isolation frequency percentages (IFs) of the fungus during different growth stages (GS) of four maize hybrids (Arma, Costanza, Kubrick and Tucson) cultivated in Northern Italy. Fusarium verticillioides contamination was detected in all the examined plants and in maize crop residues, but IF levels varied depending on the GS. The fungus colonized all the residues of maize plant organs, and ear debris were the preferential survival sites. Fusarium verticillioides was the major fungal contaminant at GS 00, in all seed lots with the only exception of Tucson hybrid. At the seedling stage GS 13, a similar isolation pattern was observed, but with lower IFs than in the correspondent seedlings grown in aseptic conditions: roots and mesocotyls were more contaminated than leaves. In plants before silking (GS 53), F. verticillioides contamination was localized in the basal organs. At maturity (GS 89), however, a general increase of IFs was observed in all organs. Since glumes and husks were the most contaminated organs, silks can be considered the most important pathways for F. verticillioides infection. The present study analyzes the endemic presence of F. verticillioides in Northern Italian fields and suggests further research of resistance factors in silks and husks as to indicate possible mechanisms for reducing fungal contamination

Enhancement of a pentacyclic tyrosine kinase inhibitor production in Cladosporium cf. cladosporioides by Cladosporol

The binaphthyl derivative cladosporol A was supplied from 60 to 200 mg l 121 to shaken cultures of Cladosporium cf. cladosporioides. Compared to blank, fungal biomass was not affected by adding cladosporol till 100 mg l 121: it rather increased at higher ratios between 150 and 200 mg l 121. The production of the major pentacyclic metabolite 1, a cytokine production and tyrosine kinase inhibitor, was enhanced tenfold when cladosporol was supplied at the highest ratio (200 mg l 121) to shaken growing cultures of the fungus. The bioconversion of cladosporol to cladosporol D through reductive cleavage of the epoxide group was also observed. Interest in this kind of metabolites lies in their potential activity vs DNA topoisomerase I

Mating behavior of a Northern Italian population of Fusarium verticillioides associated with maize

Fusarium verticillioides, the most common causal organism of Fusarium stalk and ear rot of maize in Northern Italy, produces important mycotoxins such as fumonisins. Reproductive biology of F. verticillioides has been widely studied in numerous maize growing areas, but up to now no information is available on the mating behavior and genetic structure of this plant pathogen in Italy. Mating type and female fertility distribution and effective population number, N e, were assessed for a population of 181 F. verticillioides strains isolated from three fields located in Lombardia region (Northern Italy) during 2007-2008 maize growing season. The ratio of MAT-1:MAT-2 was significantly different from the theoretical 1:1 ratio expected in an idealized population in which individuals mate at random. The frequency of hermaphroditic strains was 20 % of the total population. N e for mating type was 89 % of the count (total population) and the N e for male or hermaphrodite status was 55 %. The number of isolates that can function as the female parent limited N e in the examined population. Under equilibrium cycle, assuming that female fertility has been lost due to selection and mutation rate during asexual reproduction, sexual reproduction needed to occur only once per 40 to 118 asexual generations to maintain this level of sexual fertility

A novel secondary metabolite from the Eucalyptus pathogen Mycosphaerella cryptica

The most abundant metabolite of the eucalyptus leaf spot pathogen Mycosphaerella cryptica was extracted from agar cultures. The structure of the compound was elucidated by detailed studies of NMR and MS data and by comparison with derivatives. The compound is a previously undescribed diphenylether structurally related to pannaric acid found in lichens. Culture extracts from another species of Mycosphaerella isolated from the same environment yielded 5-hydroxymethylfuran- 3-carboxylic acid, a furan acidic compound previously isolated from a basidiomycete fungus. Assays for bioactivity of these metabolites revealed no evidence for antimicrobial activity. Some phytotoxicity was seen on newly emerged leaves of Eucalyptus globulus, but not on juvenile or adult leaves, when treated with either metabolite

Pathogenicity variation in Fusarium verticillioides populations isolated from maize in northern Italy

One hundred and eighty one strains were selected among Fusarium verticillioides populations isolated from maize samples collected in three fields located in northern Italy. All the isolates were tested for their pathogenicity on maize seeds by assessing the seed germination percentages and the percentage infection indexes concerning seed colonization, radicle decay and coleoptile rot. Fusarium verticillioides strains did not affect seed germination even in presence of high seed colonization, but showed a variable pathogenic behavior according to the maize growth stages. Seedborne F. verticillioides population as well as strains isolated at maturity was effective in seed colonization and in inducing coleoptile rot, not causing however serious radicle decay. Only populations isolated at seedling and pre-silking stages showed high radicle decay ability. These results provide baseline information on F. verticillioides pathogenicity. They constitute an important input for further investigation of F. verticillioides biology in order to define its evolutionary potential

Cryphonectric acid and other minor metabolites from a hypovirulent strain of Cryphonectria parasitica

Investigations carried out on secondary metabolites produced in culture by a hypovirulent strain of Cryphonectria parasitica allowed the isolation of several compounds which were characterized by NMR analysis and derivatization reactions. The most abundant metabolite was a new compound, called cryphonectric acid (1). Other metabolites were diaporthin, the only known phytotoxic compound isolated from both virulent and hypovirulent strains of C. parasitica, (+)-orthosporin, and L-p-hydroxyphenyllactic acid (HOPLA). Root growth activity of the purified compounds was evaluated both on tomato seedlings and maize subapical segments

Activity of synthetic and natural compounds for phytoplasma control

A sustainable and rational procedure to evaluate the activity of synthetic and natural substances towards phytoplasma agents of important tree diseases was developed with the aim of finding new strategies of control. The method of testing is based on 1) the utilization of Catharanthus roseus; 2) the artificial infection of periwinkles with two phytoplasma strains; 3) scion dipping, selected as the most suitable method of applying the substances. A series of natural and synthetic compounds were chosen among a) new agrochemical entries, registered as plant-resistance inducers; b) secondary metabolites of fungal and plant origin; c) new and known biologically active substances never tested before for their antiphytoplasmal properties. The activity of this series of compounds on healthy and phytoplasma-infected periwinkles was evaluated on the basis of several parameters: phytotoxicity, evolution of symptoms and microscope observations. The in-volvement of the third component in the triangular interaction between phytoplasma, plant and compound is discussed

Secondary mould metabolites of Cladosporium tenuissimum, a hyperparasite of rust fungi

Investigation of the extracts of a culture of Cladosporium tenuissimum, a known hyperparasite of several rust fungi, gave rise to the isolation of cladosporols B\u2013E (2\u20135). Their structure and stereochemistry were elucidated on the basis of 1H and 13C NMR evidence and CD measures. Cladosporols 1\u20135 were active in inhibiting the urediniospore germination of the bean rust agent Uromyces appendiculatus