Diversity and mycotoxin production by Fusarium temperatum and Fusarium subglutinans as causal agents of pre-harvest Fusarium maize ear rot in Poland

Fungal Species and Mycotoxins Associated with Maize Ear Rots Collected from the Eastern Cape in South Africa

Maize production in South Africa is concentrated in its central provinces. The Eastern Cape contributes less than 1% of total production, but is steadily increasing its production and has been identified as a priority region for future growth. In this study, we surveyed ear rots at maize farms in the Eastern Cape, and mycotoxins were determined to be present in collected samples. Fungal isolations were made from mouldy ears and species identified using morphology and DNA sequences. Cladosporium, Diplodia, Fusarium and Gibberella ear rots were observed during field work, and of these, we collected 78 samples and isolated 83 fungal strains. Fusarium was identified from Fusarium ear rot (FER) and Gibberella ear rot (GER) and Stenocarpella from Diplodia ear rot (DER) samples, respectively. Using LC-MS/MS multi-mycotoxin analysis, it was revealed that 83% of the collected samples contained mycotoxins, and 17% contained no mycotoxins. Fifty percent of samples contained multiple mycotoxins (deoxynivalenol, 15-acetyl-deoxynivalenol, diplodiatoxin and zearalenone) and 33% contained a single mycotoxin. Fusarium verticillioides was not isolated and fumonisins not detected during this survey. This study revealed that ear rots in the Eastern Cape are caused by a wide range of species that may produce various mycotoxins.

First record of Fusarium concentricum (Hypocreales: Hypocreaceae) isolated from the moth Polychrosis cunninhamiacola (Lepidoptera: Tortricidae) as an entomopathogenic fungus

Fusarium concentricum Nirenberg & O' Donnell (Ascomycota: Hypocreales) is a fungal species known to infect plants, but never reported as entomopathogenic. Polychrosis cunninhamiacola Liu et Pei (Lepidoptera: Tortricidae: Olethreutinae) is a major and widespread insect pest causing economic losses to cultivated Chinese fir Cunninghamia lanceolata (Lamb.) Hook. It is routinely controlled by extensive use of chemical insecticides, which is perceived as environmentally unsustainable. During March and April of 2019-2020, muscardine cadavers of larvae and pupae of P. cunninhamiacola infected with growing fungus were collected in a fir forest in northern Guangdong Province, China. Conidia were isolated and cultured on PDA medium, from which the fungal strain was identified as F. concentricum FCPC-L01 by morphology and by sequence alignment match with Tef-1α gene. Pathogenicity bioassays at the conidial concentration 1 × 107 revealed P. cunninhamiacola adults and Danaus chrysippus (L.) (Lepidoptera: Nymphalidae) larvae are sensitive to the fungal infection, but not the fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae). We believe results indicate this fungal strain might be applicable against specific target insect pests. As this is the first record of a natural infection caused by F. concentricum in insects, we propose host specificity tests should be done to evaluate its potential as a biocontrol agent.

Recent Research on Fusarium Mycotoxins in Maize—A Review

Maize (Zea mays L.) is one of the most susceptible crops to pathogenic fungal infections, and in particular to the Fusarium species. Secondary metabolites of Fusarium spp.—mycotoxins are not only phytotoxic, but also harmful to humans and animals. They can cause acute or chronic diseases with various toxic effects. The European Union member states apply standards and legal regulations on the permissible levels of mycotoxins in food and feed. This review summarises the most recent knowledge on the occurrence of toxic secondary metabolites of Fusarium in maize, taking into account modified forms of mycotoxins, the progress in research related to the health effects of consuming food or feed contaminated with mycotoxins, and also the development of biological methods for limiting and/or eliminating the presence of the same in the food chain and in compound feed.

Occurrence, Pathogenicity, and Mycotoxin Production of Fusarium temperatum in Relation to Other Fusarium Species on Maize in Germany

Fusarium subglutinans is a plant pathogenic fungus infecting cereal grain crops. In 2011, the species was divided in Fusarium temperatumsp. nov. and F. subglutinans sensu stricto. In order to determine the occurrence and significance of F. temperatum and F. subglutinans on maize, a monitoring of maize ears and stalks was carried out in Germany in 2017 and 2018. Species identification was conducted by analysis of the translation elongation factor 1α (TEF-1α) gene. Ninety-four isolates of F. temperatum and eight isolates of F. subglutinans were obtained during two years of monitoring from 60 sampling sites in nine federal states of Germany. Inoculation of maize ears revealed a superior aggressiveness for F. temperatum, followed by Fusarium graminearum, Fusarium verticillioides, and F. subglutinans. On maize stalks, F. graminearum was the most aggressive species while F. temperatum and F. subglutinans caused only small lesions. The optimal temperature for infection of maize ears with F. temperatum was 24 °C and 21 °C for F. subglutinans. All strains of F. temperatum and F. subglutinans were pathogenic on wheat and capable to cause moderate to severe head blight symptoms. The assessment of mycotoxin production of 60 strains of F. temperatum cultivated on rice revealed that all strains produced beauvericin, moniliformin, fusaric acid, and fusaproliferin. The results demonstrate a higher prevalence and aggressiveness of F. temperatum compared to F. subglutinans in German maize cultivation areas.

Fusarium Species and Fusarium oxysporum Species Complex Genotypes Associated With Yam Wilt in South-Central China

Chinese yam (Dioscorea polystachya Thunb.) is an important root crop. Wilt caused by Fusarium is among the most important emerging diseases on yams. However, there is currently limited information on the molecular epidemiology of Fusarium causing yam wilt. Here, we investigated wilted yam samples from six regions in South-Central China. A total of 117 Fusarium isolates were obtained from diseased tissues of 37 wilted yam plants. These yam plants belonged to two varieties characterized by white and purple fleshy tubers, respectively. Analyses of ef1-α sequences identified that these 117 Fusarium isolates belonged to 11 putative species, with F. aff. commune being the most common (31.6%), followed by F. aff. cugenangense (29.1%), a potential undescribed species Fusarium aff. sp. (11.1%), F. aff. gossypinum (9.4%), F. aff. fujikuroi (8.5%), F. aff. nirenbergiae (6%), and one isolate each (0.85%) of F. aff. asiaticum, F. aff. curvatum, F. aff. odoratissimum, F. aff. solani, and F. aff. verticillioides. Six of these species were recently described as new species within the Fusarium oxysporum species complex (FOSC). Interestingly, 18 of the 37 yam plants were infected by two or more Fusarium species each and there was evidence for differential Fusarium species distributions based on geographic location and/or yam host variety. Multilocus microsatellite genotyping of the 67 FOSC isolates revealed that isolates of the same species from the same diseased plants often belonged to different genotypes. Interestingly, several FOSC microsatellite genotypes were shared among distinct geographic regions, consistent with long-distance dispersal. However, population genetic analyses revealed significant contributions of geographic separation to the overall genetic variation of FOSC with several pairs of geographic populations showing significant genetic differentiations, consistent with differential geographic distribution of the species within FOSC. The implications of our results to the managements of Fusarium wilt in yams were discussed.

Fusarium Mycotoxins Enniatins: An Updated Review of Their Occurrence, the Producing Fusarium Species, and the Abiotic Determinants of Their Accumulation in Crop Harvests

Cereal grains and their processed food products are frequently contaminated with mycotoxins produced by the Fusarium genus. Enniatins (ENNs), which belong to the so-called "emerging mycotoxins" family, are among the most frequently found in small grain cereals. Health hazards induced by a chronic exposure to ENNs or an association of ENNs with other major mycotoxins is a risk that cannot be excluded given the current toxicological data. Thus, efforts must be pursued to define efficient control strategies to mitigate their presence in cereal grains. A key condition for achieving this aim is to gain deep and comprehensive knowledge of the factors promoting the appearance of ENNs in crop harvests. After an update of ENN occurrence data, this review surveys the scientific literature on the Fusarium species responsible for ENN contamination and covers the recent advances concerning the abiotic determinants and the genetic regulation of ENN biosynthesis.

Plant Phytochemicals in Food Preservation: Antifungal Bioactivity: A Review

Synthetic food additives generate a negative perception in consumers. This fact generates an important pressure on food manufacturers, searching for safer natural alternatives. Phytochemicals (such as polyphenols and thiols) and plant essential oils (terpenoids) possess antimicrobial activities that are able to prevent food spoilage due to fungi (e.g., Aspergillus, Penicillium) and intoxications (due to mycotoxins), both of which are important economic and health problems worldwide. This review summarizes industrially interesting antifungal bioactivities from the three main types of plant nutraceuticals: terpenoids (as thymol), polyphenols (as resveratrol) and thiols (as allicin) as well as some of the mechanisms of action. These phytochemicals are widely distributed in fruits and vegetables and are very useful in food preservation as they inhibit growth of important spoilage and pathogenic fungi, affecting especially mycelial growth and germination. Terpenoids and essential oils are the most abundant group of secondary metabolites found in plant extracts, especially in common aromatic plants, but polyphenols are a more remarkable group of bioactive compounds as they show a broad array of bioactivities.