Vegetative Compatibility Groups Research Articles

Fluorescently Tagged Verticillium dahliae to Understand the Infection Process on Cotton (Gossypium hirsutum) and Weed Plant Species

Verticillium wilt is a soil-borne disease caused by distinct vegetative compatibility groups (VCG) of the fungus Verticillium dahliae. Defoliating (VCG 1A) and non-defoliating (VCG 2A) pathotypes of V. dahliae have contributed to yield losses of cotton production in Australia. To study the virulence and the infection process of V. dahliae on cotton, two isolates, one representing each VCG, have been transformed with fluorescent protein genes. The transformants maintained their ability to infect the host, and both strains were observed to move through the plant vasculature to induce wilt symptoms. Furthermore, virulence testing suggests that the cotton V. dahliae strains can endophytically colonise common weed plant species found in the Australian landscape, and that is contrasted by their ability to infect and colonise native tobacco plants. The fluorescently labelled strains of V. dahliae not only allowed us to gain a thorough understanding of the infection process but also provided a method to rapidly identify recovered isolates from host colonisation studies.

Structure of Aspergillus flavus populations associated with maize in Greece, Spain, and Serbia: Implications for aflatoxin biocontrol on a regional scale.

Aspergillus flavus is the most frequently identified producer of aflatoxins. Non-aflatoxigenic members of the A. flavus L strains are used in various continents as active ingredients of bioprotectants directed at preventing aflatoxin contamination by competitive displacement of aflatoxin producers. The current research examined the genetic diversity of A. flavus L strain across southern Europe to gain insights into the population structure and evolution of this species and to evaluate the prevalence of genotypes closely related to MUCL54911, the active ingredient of AF-X1. A total of 2173L strain isolates recovered from maize collected across Greece, Spain, and Serbia in 2020 and 2021 were subjected to simple sequence repeat (SSR) genotyping. The analysis revealed high diversity within and among countries and dozens of haplotypes shared. Linkage disequilibrium analysis indicated asexual reproduction and clonal evolution of A. flavus L strain resident in Europe. Moreover, haplotypes closely related to MUCL54911 were found to belong to the same vegetative compatibility group (VCG) IT006 and were relatively common in all three countries. The results indicate that IT006 is endemic to southern Europe and may be utilized as an aflatoxin mitigation tool for maize across the region without concern for potential adverse impacts associated with the introduction of an exotic microorganism.

Diversity of Genetic and Vegetative Compatibility Group of Colletotrichum coccodes Isolates from Chile Using Amplified Fragment Length Polymorphism Markers.

Colletotrichum coccodes (Wallr.) Hughes is an asexual fungus with five vegetative compatibility groups. It was postulated that C. coccodes was isolated at the center of origin of potato at one time, and due to the movement of potato around the globe, the fungus was established on each continent but became bottlenecked and genetically unable to form stable heterokaryons via vegetative compatibility grouping (VCG) studies. The objectives of this study were (i) to determine if the VCGs around the world are related to the VCGs in Chile, (ii) to determine the diversity of C. coccodes populations in Chile, and (iii) to find any evidence for a cryptic sexual life cycle for this fungus. Worldwide C. coccodes populations have been found to be genetically correlated and belong to one or more C. coccodes-identified VCGs. The most distributed VCG in Chile was VCG2, which is the most common VCG in North America. We hypothesize that one or more VCGs had spread from Chile to the rest of the world. Precautions and further studies should be investigated by using other molecular markers and gene sequencing.

Morphological Characterization and Fusarium Wilt Resistance of Triploid Banana Mutant Line (Musa acuminata Cola)

Br 23 banana mutant line derived from irradiated gamma-ray from pisang ambon cultivar was triploid (AAA) and sterile. Therefore, application of conventional breeding to improve the agronomic characteristics of bananas requires strenuous effort. Morphological and agronomical characterizations of mutant line were observed during the generative stage on the Fusarium hotspot. Sixteen qualitative characters were observed, and each of which related to color was standardized using RHS color chart. Based on these qualitative characteristics, it was confirmed that pisang Ambon belongs to the acuminata group. Several agronomical characteristics of Br 23 banana mutant line, such as the number of hands/bunch, the weight of fruits/hand, and single fruit weight, were observed. The experimental results on banana production showed that the first harvest could reach 26 t/ha. Unlike from the control plant, the Br 23 mutant line showed tolerant characteristics to Fusarium TR4. The evaluation of susceptibility to Fusarium wilt was analyzed using the Vegetative Compatibility Group (VCG) method with isolate no. 01236/16. These susceptible plants were planted nearby the Br 23 banana mutant line. In early 2019, this Br 23 banana mutant line was registered as a new mutant variety under the name of PIRAMA I.

Molecular characterizations of Verticillium dahliae isolates from grafted tomatoes grown in Antalya province of Türkiye

AbstractVerticillium wilt caused by soil‐borne fungus Verticillium dahliae results in serious quality, yield and economic losses in tomato fruit production in tomato‐growing areas around the world. In this study, V. dahliae isolates obtained from six different major grafted tomato production areas in Antalya province of Türkiye were characterized for races, pathotypes and vegetative compatibility groups using the specific PCR primers. Out of 66 isolates, 60 were determined to be race 2. Six isolates were not identified as race 1 or race 2. Fifty‐six isolates were determined as defoliating pathotypes (D) while 10 isolates were identified as non‐defoliating (ND) pathotypes. The isolates were clustered into four vegetative compatibility groups (VCGs): VCG1A (61), VCG2A or VCG4B (3), VCG2B (1) and VCG6 (1). According to the results of this study, the race 2, D pathotype and VCG1A isolates were dominant and widely distributed in the region. Additionally, the V. dahliae isolates fall into two major groups based on the dendrogram constructed from molecular data by Dice similarity index. The dendrogram showed significant diversity among the V. dahliae isolates particularly in the Elmalı region compared to other regions. The study is the first comprehensive research with the current disease and race 2 was identified for the first time in grafted tomatoes. These findings will lead to the development of V. dahliae‐resistant grafted tomatoes and breeding programs in Türkiye.

First report of Fusarium wilt of Cavendish bananas caused by Fusarium oxysporum f. sp. cubense Tropical Race 4 in the Grande Comoros Island.

Fusarium wilt of banana, caused by the soil-borne pathogen Fusarium oxysporum f. sp. cubense (Foc), is a major constraint to banana production worldwide (Viljoen et al., 2020). Currently, Cavendish bananas are severely affected by Foc Tropical Race 4 (TR4) globally. In Africa, Foc TR4 was first detected in northern Mozambique in 2013 (Viljoen et al., 2020), and has since been found on the island of Mayotte in the Mozambique Channel off the coast of southeastern Africa (Aguayo et al., 2021). In early 2023, severe leaf-yellowing and wilting of Cavendish banana plants was observed on Cavendish banana plants at several small holder farmer properties in Grande Comoros (Ngazidja) including in Ntsinimoipanga (-11,790054 S, 43°25'47,04384 E), Batou (-11,499716 S, 43°21'51,71976''E), Madjeweni (-11,8217 S , 43°16'41''E) and Mdé (-11°41'54'' S, 43°15'20''E). When the pseudostems of these plants were split open, a reddish-brown internal discoloration of the vascular tissue became apparent. Discolored strands of diseased plants were collected, and the causal agent identified using DNA-based techniques, vegetative compatibility group (VCG) analysis and pathogenicity testing. The samples were plated onto potato dextrose agar and single-spored and isolated from individual diseased plants identified as F. oxysporum based on cultural and morphological characteristics. These include the production of white fungal colonies with a purple center, infrequent production of macroconidia, but an abundance of microconidia on short monophialides, and terminal or intercalary chlamydospores (Leslie and Summerell, 2006). Foc TR4 was identified from seven isolates by conventional (Dita et al., 2010) and quantitative-PCR (Matthews et al., 2020), and with loop-mediated isothermal amplification (LAMP) (Ordóñez et al., 2021). All seven isolates were confirmed as members of the VCG 01213/16 complex when nit-1 mutants of the unknown Foc isolates were compatible with Nit-M mutants of the Foc VCG 01213 and VCG 01216 tester strains. Two isolates were then selected for pathogenicity testing, and 2-month-old tissue culture-derived Cavendish plants (cv. Williams) inoculated by using the method described by Ndayihanzamaso et al. (2022). After 4 weeks, the Foc TR4-inoculated plants produced wilting symptoms and internal rhizome discoloration typical of Fusarium wilt. Foc TR4 was reisolated from the inoculated plants and identified by qPCR (Matthews et al. 2020), thereby fulfilling Koch's postulates. These results provide scientific proof of the presence of Foc TR4 in a second island in the Comoros archipelago. Comprehensive surveys will be conducted in all three of the Comoros Islands to assess the presence and impact of Foc TR4 to implement containment strategies. Collaborative initiatives and coordinated actions among growers and other stakeholders are needed to prevent the spread of Foc TR4 to more Southwest Indian Ocean islands and countries on the East African coasts. The importance of banana for food security and livelihoods, and the unique genetic diversity of bananas found on the Comoros islands, requires the eradication and isolation of diseased bananas on the short term, and the screening of local banana varieties for Foc TR4 resistance on the longer term.

Cryphonectria parasitica Detections in England, Jersey, and Guernsey during 2020-2023 Reveal Newly Affected Areas and Infections by the CHV1 Mycovirus.

In England, Cryphonectria parasitica was detected for the first time in 2011 in a nursery and in 2016 in the wider environment. Surveys between 2017 and 2020 identified the disease at different sites in Berkshire, Buckinghamshire, Cornwall, Derbyshire, Devon, Dorset, London, West Sussex, and the island of Jersey, while the present study comprises the results of the 2020-2023 survey with findings in Derbyshire, Devon, Kent, Nottinghamshire, Herefordshire, Leicestershire, London, West Sussex, and the islands of Jersey and Guernsey. A total of 226 suspected samples were collected from 72 surveyed sites, as far north as Edinburgh and as far west as Plymouth (both of which were negative), and 112 samples tested positive by real-time PCR and isolation from 35 sites. The 112 isolates were tested for the vegetative compatibility group (VCG), mating type, and Cryphonectria hypovirus 1 (CHV1). Twelve VCGs were identified, with two of them (EU-5 and EU-22) being the first records in the UK. Both mating types were present (37% MAT-1 and 63% MAT-2), but only one mating type was present per site and VCG, and perithecia were never observed. Cryphonectria hypovirus 1 (CHV1), consistently subtype-I haplotype E-5, was detected in three isolates at a low concentration (5.9, 21.1, and 33.0 ng/µL) from locations in London, Nottinghamshire, and Devon.

Effect of various formulations of Piper aduncum botanical pesticide and concentration levels on fungal pathogen Fusarium oxysporum f.sp. cubense Vegetative Compatibility Group (VCG) 01213/16 Tropical strain 4 and VCG 01218 strain 1

Pathogen of Fusarium oxysporum f.sp. cubence (Foc) Vegetative Compatibility Group (VCG) 01213/16 (Tropical strain/TR4) and VCG 01218 (strain1) are the cause of wilt disease in banana. Plant-based pesticides are an alternative environmentally friendly substance that can control plant pathogens. This study aims to obtain a formulation of Piper aduncum oil with several essential oils to suppress the growth development of two Foc strains that cause wilt disease in banana plants. This study used a complete randomized design in factorial, where the first factor is the type of formulation: F1 = 25% P. aduncum leaf oil, F2 = P. aduncum leaf oil with lemongrass leaf oil (Cymbopogon flexiosus), F3 = P. aduncum oil with citronella leaves (Andropogon nardus), F4 = P. aduncum oil with Ceylon cinnamon leaf oil (Cinnamomum zeylanicum), F5 = P. aduncum oil with Padang cinnamon leaf oil (C. burmanii), F6 = P. aduncum oil with cloves leaf oil (Eugenia aromatica) F7=P. aduncum oil with wild ginger oil (Elettariopsis slahmong). The second factor is the concentration level: 1000, 2000, and 3000 ppm. The results showed that diameter of mycelium between Foc VCG01213/16 and VCG01218 did not differ significantly. However, there were significant differences in the botanical pesticide formulations used. P. aduncum oil formulation mixed with cloves leaf oil and ceylon cinnamon oil at a concentration level of 3000 ppm had better inhibition of colony diameter, namely for Foc VCG01213/16 (90.55% and 88.08%) and on Foc VCG 01218 (90.72% and 89.85%). Likewise, for the inhibition of colony biomass, the best formulation is the P. aduncum oil mixed with cloves leaf oil and with ceylon cinnamon oil, the concentration level at 3000 ppm for Foc VCG 01213/16 were 96.64 and 95.80%, respectively. In contrast, for Foc VCG 01218 were 96.00% for both.

First report of Fusarium wilt of Cavendish bananas caused by Fusarium oxysporum f. sp. cubense Tropical Race 4 in Venezuela.

Fusarium wilt of banana (Musa spp.), caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc), is a major constraint to banana production worldwide (Dita et al., 2018). A strain of Foc that affects Cavendish (AAA) bananas in the tropics, called Foc tropical race 4 (TR4; VCG 01213), is of particular concern. Foc TR4 was first detected in Malaysia and Indonesia around 1990 but was restricted to Southeast Asia and northern Australia until 2012. The fungus has since been reported from Africa, the Indian subcontinent, and the Middle East (Viljoen et al., 2020). Foc TR4 was detected in Colombia in 2019 and in Perú in 2021 (Reyes-Herrera et al., 2020). The incursions into Latin America and the Caribbean (LAC) triggered global concerns, as 75% of international export bananas are produced in the region. Banana production in Venezuela, however, is primarily intended for domestic consumption (Aular and Casares, 2011). In 2021 the country produced 533,190 metric tons of banana on an area of 35,896 ha, with an approximate yield of 14,853 kg/ha (FAOSTAT, 2023). In July 2022, severe leaf-yellowing, and wilting, along with internal vascular discoloration of the pseudostem, were noted in Cavendish banana plants cultivar 'Valery' in the states of Aragua (10°11'8″N; 67°34'51″W), Carabobo (10º14'24″N; 67º48'51″W), and Cojedes (9°37'44″N; 68°55'4″W). Necrotic strands from the pseudostems of diseased plants were collected for identification of the causal agent using DNA-based techniques, vegetative compatibility group (VCG) analysis and pathogenicity testing. The samples were first surface disinfected and plated onto potato dextrose agar medium. Single-spored isolates were identified as F. oxysporum based on cultural and morphological characteristics, including white colonies with purple centres, infrequent macroconidia, abundant microconidia on short monophialides, and terminal or intercalary chlamydospores (Leslie and Summerell, 2006). Foc TR4 was identified from five isolates by endpoint and quantitative-PCR using four different primer sets (Li et al. 2013; Dita et al. 2010; Aguayo et al. 2017; Matthews et al. 2020). The same isolates were identified as VCG 01213 by successfully pairing nitrate non-utilizing (nit-1) mutants of the unknown strains with Nit-M testers of Foc TR4 available at Stellenbosch University (Leslie and Summerell, 2006). For pathogenicity testing, 3-month-old Cavendish banana plants cultivar 'Williams' were inoculated with isolates from Venezuela grown on sterile millet seed (Viljoen et al., 2017). Plants developed typical Fusarium wilt symptoms 60 days after inoculation, including yellowing of leaves that progressed from the older to the younger leaves, wilting, and internal discoloration of the pseudostem. Koch's postulates were fulfilled by reisolating and identifying Foc TR4 from the plants by qPCR (Matthews et al., 2020). These results provide scientific proof of the presence of Foc TR4 in Venezuela. The Venezuelan Plant Protection Organization (INSAI) has declared Foc TR4 as a newly introduced pest (January 19, 2023), and infested banana fields were placed under quarantine. Comprehensive surveys are now conducted in all production areas in Venezuela to assess the presence and impact of Foc TR4, and information campaigns were started to make farmers aware of biosecurity protocols. Collaborative initiatives and coordinated actions among all stakeholders are needed to prevent the spread of Foc TR4 to other countries in Latin America, and to develop Foc TR4-resistant bananas (Figueiredo et al. 2023).

Characterisation and pathogenicity of Verticillium dahliae isolates associated with Verticillium wilt of tomato in the Limpopo Province of South Africa

In the Limpopo Province of South Africa, the sustainable production of tomatoes is threatened by a soilborne disease known as Verticillium wilt. Limited information is available regarding the Verticillium species involved, their genetic diversity and aggressiveness. Therefore, a pathogen survey was conducted in the three major tomato production regions in Limpopo (six fields in the Lowveld and two fields each in the Highveld and Soutpansberg). Verticillium dahliae was identified as the only Verticillium species associated with Verticillium wilt of tomatoes. Conventional vegetative compatibility group (VCG) testing identified 38 isolates as VCG 4B and two isolates as VCG 2B. Pathotype-genotype specific PCR analysis indicated that all the isolates belonged to the non-defoliating pathotype, specifically genotype C. These characteristics allowed for the classification of almost all the isolates from the Lowveld, Highveld and Soutpansberg regions into clonal lineage 4B (38 isolates). The exception was for two isolates from the Lowveld that belonged to lineage 2B824. Based on a race-specific PCR analysis, all 40 isolates belonged to race 2. Sequencing of the race-specific PCR amplicon revealed the presence of two haplotypes namely I and II. Evaluation of seven inoculation methods (agar plug, millet, node-inoculation, root-dip, sand-bran, soil-drench and toothpick methods) using three isolates showed that the root-dip method was the only method that consistently identified all the isolates as pathogenic based on disease severity as well as an increase in plant height. Assessment of the aggressiveness of the 40 characterised V. dahliae isolates showed that the isolates varied in aggressiveness to the cv. Floradade.

Identification of Fusarium oxysporum f.sp cepae race 4 isolated from shallots in East Java Indonesia

Fusarium oxysporum f.sp cepae (Foce) which causes moler disease, has been mutated into four races. The fourth race is the riskiest due to its vulnerability to being attacked by various cultivars. This research aims to identify the existence of Foce Race 4 in the shallot production center districts. The plant samples attacked by moler disease were taken in three districts (i.e., Magetan, Nganjuk, and Probolinggo) by Purposive Random Sampling method with 5% samples, obtaining 9 Foce isolates. The results were then identified using Volatile Odor Test (VOT), Biochemistry, and Vegetative Compatibility Group (VCG); four were identified as Race 4. Those four isolates were then examined for their virulences towards three cultivars, particularly Bauji, Tajuk, and Biru Lancor. The findings show that all four isolates were noxious and able to plague all the varieties.

Genetic Diversity and Pathogenicity of Fusarium fujikuroi Species Complex (FFSC) Causing Sugarcane Pokkah Boeng Disease (PBD) in China.

Pokkah boeng disease (PBD), a sugarcane foliar disease, is caused by various Fusarium spp. within the Fusarium fujikuroi species complex (FFSC). In the current study, we investigated the diversity of Fusarium spp. associated with PBD in China. In total, 320 leaf samples displaying PBD symptoms were collected over 10 consecutive years (2012 to 2021), during winter and summer, from six various sugarcane-growing regions (Guangxi, Yunnan, Guangdong, Zhejiang, Hainan, and Fujian) in China. Phylogenetic analysis of Fusarium spp. was reconstructed using translation elongation factor 1-α, and DNA-directed RNA polymerase II largest subunit and second-largest subunit multigene sequences. Evolutionary studies of these regions categorized the isolates into four FFSC species (F. sacchari, F. proliferatum, F. verticillioides, and F. andiyazi). The identified isolates, which developed irregular necrotic patches and rotting symptoms on the sugarcane plant after approximately 30 days were tested for their pathogenicity. Symptoms that appeared during pathogenicity testing were consistent with those observed under field conditions. Each strain of the pathogenic Fusarium spp. belonged to different vegetative compatibility groups (VCGs), and there was no affinity between VCGs. Our results contribute to understanding FFSC and accurately identifying Fusarium spp. associated with the sugarcane crop.

Various Population Structures of Cryphonectria parasitica in Cáceres (Spain) Determine the Feasibility of the Biological Control of Chestnut Blight with Hypovirulent Strains

Chestnut blight, caused by Cryphonectria parasitica, is a severe disease that may be biologically controlled by the use of hypovirulent strains, but the diversity of the pathogen population affects biocontrol feasibility. Villuercas–Ibores–Jara, the Jerte Valley and La Vera are the main chestnut production districts in Cáceres (central-western Spain). The purpose of this study is to determine the Vegetative Compatibility Groups (VCGs) and mating types in these districts and to identify hypovirulent isolates to be used in biological control. The VCGs were determined by the merging/barrage response; PCR tests were used for the mating type determination and CHV-1 hypovirus detection. In total, 40 sites were surveyed and 269 isolates were obtained, most of them (227) from the Villuercas–Ibores–Jara district, where EU11 was the predominant VCG (88.1%) with EU1 (6.6%) and EU12 (4.4%) being also present. In the Jerte Valley and La Vera, EU1 (61.9%), EU11 (11.9%) and EU12 (11.9%) were the predominant VCGs. Both mating types were detected (48% MAT-1; 50% MAT-2) and in general, only one mating type was found in each site. The presence of Cryphonectria hypovirus 1 (CHV-1), subtype I, was identified in only one isolate (VCG EU11) from Villuercas–Ibores–Jara. The characteristics of the C. parasitica population in this district and the occurrence of CHV-1 hypovirus support the potential of successful biological control in Villuercas–Ibores–Jara using hypovirulent strains, while in the Jerte Valley and La Vera only preventive measures are recommended.

Molecular Diagnosis and Vegetative Compatibility Group Analysis of Fusarium Wilt of Banana in Nepal

Fusarium wilt of banana (FWB), caused by Fusarium oxysporum f. sp. cubense (Foc), is the most important constraint of the banana industry globally. In Nepal, epidemics resembling FWB have been increasingly observed on the Malbhog cultivar in the past several years. However, the disease has not been officially reported yet, and consequently, little is known about the pathogen present across the country. In this study, we characterized 13 fungal strains isolated from banana plants of the Malbhog cultivar (Silk, AAB) showing symptoms similar to FWB in banana plantations in Nepal. All of the strains were typed as belonging to the F. oxysporum and caused FWB symptoms when inoculated in the Malbhog and Cachaco (Bluggoe, ABB) cultivars. No symptoms were observed in the Williams cultivar (Cavendish, AAA). Vegetative compatibility group (VCG) analysis classified the strains as VCG 0124 or VCG 0125. PCR analyses conducted with primers specific for Foc race 1 (Foc R1) or Foc tropical race 4 (TR4) revealed that all the strains reacted positively for Foc R1 and none for TR4. Altogether, our results demonstrated that the pathogen populations causing FWB of the Malbhog cultivar in Nepal were Foc R1. This work reported, for the first time, the occurrence of FWB in Nepal. Further studies with larger Foc populations are needed to better understand disease epidemiology to design sustainable disease management strategies.

An Interactive, Online Web Map Resource of Global Fusarium oxysporum ff. spp. Diversity and Distribution.

An Interactive, Online Web Map Resource of Global Fusarium oxysporum ff. spp. Diversity and Distribution.

Surveillance, Diversity and Vegetative Compatibility Groups of Fusarium oxysporum f. sp. vasinfectum Collected in Cotton Fields in Australia (2017 to 2022)

Cotton (Gossypium hirsutum) is a billion-dollar crop in regional New South Wales (NSW) and Queensland, Australia. Fusarium wilt (FW) caused by Fusarium oxysporum f. sp. vasinfectum (Fov) is an economically important disease. Initial disease losses of up to 90% when the disease was first detected resulted in fields being taken out of cotton production. The disease is now well-managed due to the adoption of highly resistant varieties. However, annual disease surveys recently revealed that the disease dynamic has changed in the past few seasons. With relatively mild and wet weather conditions during the 2021/22 growing season, FW was detected in eight surveyed valleys in NSW and Queensland, with the disease incidence as high as 44.5% and 98.5% in individual fields in early and late seasons, respectively. Fov is genetically distinct and evolved from local Fusarium oxysporum strains. Additionally, the pathogen was reported to evolve rapidly under continuous cotton cropping pressure. However, our knowledge of the genetic composition of the prevailing population is limited. Sequences of the translation elongation factor alpha 1 (TEF1) revealed that 94% of Fusarium isolates recovered from FW-infected cotton were clustered together with known Australian Fov and relatively distant related to overseas Fov races. All these isolates, except for nine, were further confirmed positive with a specific marker based on the Secreted in Xylem 6 (SIX6) effector gene. Vegetative compatibility group (VCG) analyses of 166 arbitrarily selected isolates revealed a predominance of VCG01111. There was only one detection of VCG01112 in the Border Rivers valley where it was first described. In this study, the exotic Californian Fov race 4 strain was not detected using a specific marker based on the unique Tfo1 insertion in the phosphate (PHO) gene. This study indicated that the prevalence and abundance of Fov across NSW and Queensland in the past five seasons was probably independent of its genetic diversity.

The Population of Fusarium oxysporum f. sp. cubense in Brazil Is Not Structured by Vegetative Compatibility Group or by Geographic Origin.

Fusarium wilt, caused by the soilborne fungus Fusarium oxysporum f. sp. cubense (Foc), is considered one of the most destructive diseases of bananas in Brazil. In this study, a collection of 194 monosporic isolates from several banana-producing regions located in different climatic zones along a south-to-north transect in Brazil was formed to assess the genetic structure of the population of Foc. The isolates underwent pathogenicity tests, PCR diagnosis for the detection of tropical race 4, and screening of SIX homolog genes that produce putative effector proteins. The vegetative compatibility group (VCG) of 119 isolates was determined by pairing against 17 internationally known VCG-tester strains. A group of 158 isolates was selected for simple sequence repeat (SSR) genotyping. There was moderate diversity of Foc in Brazil. Eight VCGs were identified: 0120, 0122, 0124, 0125, 0128, 01215, 01220, and 01222, of which 78% of isolates belong to a single VCG, whereas 22% of isolates are assigned to multiple VCGs, belonging to complexes of VCGs. The distribution of VCGs is uneven and independent of the banana genotype. The isolates of a VCG shared a similar profile of SIX homologs, but there was no association with geographic region. Four SSR loci were polymorphic, and, on average, 7.5 alleles were detected per locus. Thirty-five multilocus genotypes (MLGs) were identified. There was no association between VCG and MLGs, and no genetic structure of the population of Foc in Brazil was detected.

First report of the presence of Verticillium dahliae VCG6 in Australia

Verticillium dahliae was isolated from Noogoora burr (Xanthium occidentale) seeds collected from mature asymptomatic plants in 2017 growing along the riverbank at Condobolin, NSW. V. dahliae was isolated from seeds by transferring surfaced-disinfested seed components onto 25% Potato Dextrose Agar (PDA) plus Novobiocin. Morphological and molecular analysis, as well as fulfilment of Koch’s postulates, confirmed the causal pathogen was V. dahliae. Additional analysis was carried out to assign the isolates into a vegetative compatibility group (VCG) and pathotype. This is the first report of V. dahliae VCG6 in Australia infecting X. occidentale.

Differentiating individuals of Armillaria species in New Zealand forests

Background: Armillaria novae-zelandiae and A. limonea occur naturally as wood decay fungi in native forests in New Zealand. As pathogens they are responsible for significant root disease in trees and shrubs in plantations, crops and urban parks and gardens. A thorough understanding of their population dynamics entails knowledge of the spatial arrangement of their individual mycelia or genets. In previous work the distributions of vegetative compatibility groups (VCGs) of these fungi were mapped in an area of native forest prior to and after replacement by a young Pinus radiata plantation. With the advent of molecular technology, it has become possible to test species identities made earlier using culture techniques and to verify whether or not their VCGs, determined by incompatibility reactions between paired cultures, represent distinct individual genets. Methods: Stock subcultures of isolates representing each VCG were recovered from storage in order to obtain DNA. Extracted DNA was subjected to a polymerase chain reaction procedure (UP-PCR) using 11 universal primers to assess genetic variation between subcultures. Bands were scored as either present or absent for each primer-subculture combination and cluster analysis was undertaken by generating dendrogram trees to reveal genetic groupings among subcultures. Results: DNA cluster analysis divided subcultures of isolates into two species groups, A. novae-zelandiae and A. limonea, corresponding to identities determined through culture morphology. Within species, subcultures grouped into clusters that matched VCGs determined by earlier culture pairing. There was little indication of genetic variation within VCGs, except for one of A. limonea, which comprised two sub-clusters. Conclusions: The Armillaria species and VCGs identified by culture techniques in the laboratory were verified by independent molecular methodology. In general, the VCGs represent discrete individual genets or colonies in the field. Techniques that differentiate isolates based on differences in their DNA sequence provide a quick alternative to time-consuming laboratory culture methods for resolving population spatial structure. However, some complementary isolate pairing may be necessary when rationalising the significance of groupings in dendrogram trees.

Characterization of Vegetative Incompatibility in Morchella importuna and Location of the Related-Genes by Bulk Segregant Analysis.

Vegetative incompatibility (VI) is a widespread phenomenon developed in Morchella importuna, a species of ascomycete fungus that is cultivated on a rapidly expanding scale in China. Understanding the genetic bases of this nonself-recognition phenomenon is beneficial for resolving some problems that are associated with the production of this highly prized edible fungus, such as crossbreeding, strain classification, and pathogen transmission. VI is genetically controlled by het genes, organized in two different systems, namely allelic and nonallelic. These het genes have been well characterized in Podospora anserina and Neurospora crassa. In this work, putative het-homologs were identified in the genome of M. importuna, but their low allelic polymorphism in different vegetative compatibility groups (VCGs) suggested that VI in this fungus might not be regulated by these het genes. The progeny derived from vegetative compatible parents became a VCG, while the single-ascospore strains from vegetative incompatible parents were divided into four VCGs, and the interaction between the inter-group strains led to the formation of two types of barrages, viz., thin dark line and raised aggregate of hyphae. The Bulk Segregant Analysis confirmed that the genes mimpvic32 and mimpvic33 were linked to VI reactions in M. importuna; nevertheless, the formation of barrages also occurred between the pairs carrying the same allele of these two genes. In sum, the VI control system in M. importuna was complicated, and there were more other allelic or non-allelic VI-related genes.