Differences in the geographic distribution of distinct trichothecene mycotoxins in wheat and barley were first recorded two decades ago. The different toxicological properties of deoxynivalenol (DON), nivalenol (NIV) and their acetylated derivatives require careful monitoring of the dynamics of these mycotoxins and their producers. The phylogenetic species concept has become a valuable tool to study the global occurrence of mycotoxin-producing Fusarium species. This has revolutionised our views on the terrestrial distribution of trichothecene-producing Fusaria in the context of agronomics, climatic conditions, and human interference by the global trade and exchange of agricultural commodities. This paper presents an overview of the dynamics of the different trichothecene-producing Fusarium species as well as their chemotypes and genotypes across different continents. Clearly not one global population exists, but separate ones can be distinguished, sometimes even sympatric in combination with different hosts. A population with more pathogenic strains and chemotypes can replace another. Several displacement events appear to find their origin in the inadvertent introduction of new genotypes into new regions: 3-acetyl-DON-producing F. graminearum in Canada; 3-acetyl-DON-producing F. asiaticum in Eastern China; 15-acetyl-DON F. graminearum in Uruguay; and NIV-producing F asiaticum in the southern United States.

https://www.tandfonline.com/doi/pdf/10.1080/19440049.2014.984244

Biogeography of Fusarium graminearum species complex and chemotypes: a review

The genetic basis for 3-ADON and 15-ADON trichothecene chemotypes in Fusarium.

Fusarium head blight (FHB) is primarily caused by Fusarium graminearum in North America. Isolates of F. graminearum can be identified as one of three chemotypes: 3-acetyl-deoxynivalenol (3...

https://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO-12-09-0332

The 3ADON Population of Fusarium graminearum Found in North Dakota Is More Aggressive and Produces a Higher Level of DON than the Prevalent 15ADON Population in Spring Wheat

There is increasing difficulty in identifying new plant leaf diseases as a result of environmental change. There is a need to identify the factors influencing the emergence and the increasing incidences of these diseases. Here, we present emerging fungal plant leaf diseases and describe their environmental speciation. We considered the factors controlling for local adaptation associated with environmental speciation. We determined that the advent of emergent fungal leaf diseases is closely connected to environmental speciation. Fungal pathogens targeting the leaves may adversely affect the entire plant body. To mitigate the injury caused by these pathogens, it is necessary to be able to detect and identify them early in the infection process. In this way, their distribution, virulence, incidence, and severity could be attenuated.

https://www.tandfonline.com/doi/pdf/10.1080/21655979.2019.1649520

A review of plant leaf fungal diseases and its environment speciation.

Potato crop is the fourth main food crop in the world and it will certainly feed a big part of the global population in the next years. The economical outlets for this crop are great; however, numerous diseases either soil- or air-borne can cause huge losses in the production. Worldwide, about 40 soil-borne diseases affect potato and cause severe damages especially on tubers, the economically most important part of the plant. The occurrence and development of soil-borne diseases depend on very diverse factors affecting either the pathogen or the plant. Favorable conditions for potato diseases development are frequently the same as the conditions needed for potato growth: temperature between 10°C and 25°C, high humidity, medium pH, etc. Adapted cultural practices such as a rotation longer than 4 years, appropriate fertilization and water management, an adapted delay between haulm killing and harvest, and dry and cool conditions for tuber storage are good ways to control potato diseases. In most cases, potato pathogens develop specific survival forms, dissemination ways and host penetration methods. The genetic variability of the pathogens implies the use of adapted diagnostic and control methods. Decision support systems developed to predict yield losses allow choosing good control methods such as the use of healthy seeds, adapted pesticides, cultural practices, and biological control agents for each potato disease. The complexity of the interactions between a pathogen and its host, influenced by biotic and abiotic factors of the environment, make the control of the diseases often very difficult. However, deep knowledge of pathosystems allows setting up integrated pest management systems allowing the production of healthy and good quality potatoes.

/pdf/potato-soil-borne-diseases-a-review-cb2rrubef2.pdf

Potato soil-borne diseases. A review

Fusarium graminearum causes Fusarium head blight (FHB) in small grains worldwide. Although primarily a pathogen of cereals, it also can infect noncereal crops such as potato and sugar beet in the United States. We used a real-time polymerase chain reaction (PCR) method based on intergenic sequences specific to the trichodiene synthase gene (Tri5) from F. graminearum. TaqMan probe and primers were designed and used to estimate DNA content of the pathogen (FgDNA) in the susceptible wheat cv. Grandin after inoculation with the 21 isolates of F. graminearum collected from potato, sugar beet, and wheat. The presence of nine mycotoxins was analyzed in the inoculated wheat heads by gas chromatography and mass spectrometry. All isolates contained the Tri5 gene and were virulent to cv. Grandin. Isolates of F. graminearum differed significantly in virulence (expressed as disease severity), FgDNA content, and mycotoxin accumulation. Potato isolates showed greater variability in producing different mycotoxin...

https://apsjournals.apsnet.org/doi/pdfplus/10.1094/PHYTO-97-7-0835

Real-time PCR Quantification and Mycotoxin Production of Fusarium graminearum in Wheat Inoculated with Isolates Collected from Potato, Sugar Beet, and Wheat

Mungbean (Vigna radiata var. radiata) is a key legume crop grown predominantly in South and Southeast Asia. Biotic and abiotic stresses cause significant yield reduction in mungbean, and among these, fungal diseases are particularly important. Although disease management practices, including physical, chemical, and biological methods have been researched and described in the literature, few of these are available or have been used by growers. Here we review the economic impact, pathogen characterization, and sustainable management options for the soil-borne and foliar fungal diseases of mungbean as well as major challenges to manage these diseases. Potential use of all possible components of integrated management practices including host resistance, fungicides, biocontrol agents, natural plant products, and cultural practices etc. are discussed. Major diseases include powdery mildew, anthracnose, Cercospora leaf spot, Fusarium wilt, Rhizoctonia root rot and web blight, Macrophomina charcoal rot/dry root rot and blight. Review of the literature indicated an absence of resistance to Rhizoctonia root rot, little sources of resistance for dry root rot and anthracnose. Major resistant genes (R genes) and quantitative trait loci (QTL) were identified for powdery mildew and Cercospora leaf spot, which may be potentially used in Marker assisted selection (MAS). has been used in resistance breeding for both of the latter. Although the mechanisms of induced systemic resistance (ISR) by biocontrol agents have been studied with Macrophomina blight, there is little information on the mechanisms and use of systemic acquired resistance (SAR) in managing fungal diseases of mungbean. Several studies targeted exploiting biological control for soil-borne root rot diseases. Botanical products, such as plant extracts, are also found effective to manage root and foliar diseases. However, many of these studies were limited to laboratory and/or green house experiments. Thus, long-term field studies are required for further exploitation of biological methods and commercial applications.

/pdf/perspectives-and-challenges-for-sustainable-management-of-d7gud3plcq.pdf

Perspectives and Challenges for Sustainable Management of Fungal Diseases of Mungbean [Vigna radiata (L.) R. Wilczek var. radiata]: A Review

Gibberella zeae, a causal agent of Fusarium head blight (FHB) in wheat and barley, is one of the most economically harmful pathogens of cereals in the United States. In recent years, the known host range of G. zeae has also expanded to noncereal crops. However, there is a lack of information on the population genetic structure of G. zeae associated with noncereal crops and across wheat cultivars. To test the hypothesis that G. zeae populations sampled from barley, wheat, potato, and sugar beet in the Upper Midwest of the United States are not mixtures of species or G. zeae clades, we analyzed sequence data of G. zeae, and confirmed that all populations studied were present in the same clade of G. zeae. Ten variable number tandem repeat (VNTR) markers were used to determine the genetic structure of G. zeae from the four crop populations. To examine the effect of wheat cultivars on the pathogen populations, 227 strains were sampled from 10 subpopulations according to wheat cultivar types. The VNTR markers also were used to analyze the genetic structure of these subpopulations. In all populations, gene (H = 0.453 to 0.612) and genotype diversity (GD = >0.984) were high. There was little or no indication of linkage disequilibrium (LD) in all G. zeae populations and subpopulations. In addition, high gene flow (Nm) values were observed between cereal and noncereal populations (Nm = 10.69) and between FHB resistant and susceptible wheat cultivar subpopulations (Nm = 16.072), suggesting low population differentiation of G. zeae in this region. Analysis of molecular variance also revealed high genetic variation (>80%) among individuals within populations and subpopulations. However, low genetic variation (<5%) was observed between cereal and noncereal populations and between resistant and susceptible wheat subpopulations. Overall, these results suggest that the populations or subpopulations are likely a single large population of G. zeae affecting crops in the upper Midwest of the United States.

https://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO-98-9-0969

Genetic relationships among populations of Gibberella zeae from barley, wheat, potato, and sugar beet in the upper Midwest of the United States.

Morphological and molecular characterization of Macrophomina phaseolina isolated from three legume crops and evaluation of mungbean genotypes for resistance to dry root rot

Gibberella zeae is one of the most devastating pathogens of barley and wheat in the United States. The fungus also infects noncereal crops, such as potatoes and sugar beets, and the genetic relationships among barley, wheat, potato, and sugar beet isolates indicate high levels of similarity. However, little is known about the toxigenic potential of G. zeae isolates from potatoes and sugar beets. A total of 336 isolates of G. zeae from barley, wheat, potatoes, and sugar beets were collected and analyzed by TRI (trichothecene biosynthesis gene)-based PCR assays. To verify the TRI-based PCR detection of genetic markers by chemical analysis, 45 representative isolates were grown in rice cultures for 28 days and 15 trichothecenes and 2 zearalenone (ZEA) analogs were quantified using gas chromatography-mass spectrometry. TRI-based PCR assays revealed that all isolates had the deoxynivalenol (DON) marker. The frequencies of isolates with the 15-acetyl-deoxynivalenol (15-ADON) marker were higher than those of isolates with the 3-acetyl-deoxynivalenol (3-ADON) marker among isolates from all four crops. Fusarium head blight (FHB)-resistant wheat cultivars had little or no influence on the diversity of isolates associated with the 3-ADON and 15-ADON markers. However, the frequency of isolates with the 3-ADON marker among isolates from the Langdon, ND, sampling site was higher than those among isolates from the Carrington and Minot, ND, sites. In chemical analyses, DON, 3-ADON, 15-ADON, b-ZEA, and ZEA were detected. All isolates produced DON (1 to 782 μg/g) and ZEA (1 to 623 μg/g). These findings may be useful for monitoring mycotoxin contamination and for formulating FHB management strategies for these crops.

/pdf/comparative-mycotoxin-profiles-of-gibberella-zeae-21atcsgkz3.pdf

Rishi R. Burlakoti

Papers

Real-time PCR Quantification and Mycotoxin Production of Fusarium graminearum in Wheat Inoculated with Isolates Collected from Potato, Sugar Beet, and Wheat

Perspectives and Challenges for Sustainable Management of Fungal Diseases of Mungbean [Vigna radiata (L.) R. Wilczek var. radiata]: A Review

Genetic relationships among populations of Gibberella zeae from barley, wheat, potato, and sugar beet in the upper Midwest of the United States.

Morphological and molecular characterization of Macrophomina phaseolina isolated from three legume crops and evaluation of mungbean genotypes for resistance to dry root rot

Comparative Mycotoxin Profiles of Gibberella zeae Populations from Barley, Wheat, Potatoes, and Sugar Beets