Joshua L. Konkol

Bio: Joshua L. Konkol is an academic researcher from University of Florida. The author has contributed to research in topics: Laurel wilt & Persea. The author has an hindex of 11, co-authored 21 publications receiving 478 citations.

First Report of Fusarium oxysporum f. sp. cubense Tropical Race 4 associated with Panama Disease of banana outside Southeast Asia

Abstract: Fusarium wilt or Panama disease of banana, caused by Fusarium oxysporum f. sp. cubense (Foc), is among the most destructive plant diseases (3). Race 1 ravaged ‘Gros Michel’-based export trades until the cultivar was replaced by resistant Cavendish cultivars. However, a new variant of Foc, tropical race 4 (TR4), was identified in Southeast Asia in 1992 and has spread throughout the region (3). Cavendish clones, which are most important in subsistence and export production, are among the wide range of cultivars that are affected, and there is a huge concern that TR4 will further disseminate in Africa since its presence was announced in November 2013 and move into Latin America, thereby threatening other vital banana-growing regions. In Jordan, Cavendish bananas are produced on 1,000 to 1,500 ha in the Jordan Valley (32°N, 35.5°E). In 2006, symptoms of Fusarium wilt were observed and sampled for the isolation of Foc. On half-strength PDA amended with 100-ppm streptomycin sulfate, pale salmon-colored colonies...

Presence and Prevalence of Raffaelea lauricola, Cause of Laurel Wilt, in Different Species of Ambrosia Beetle in Florida, USA.

Abstract: We summarize the information available on ambrosia beetle species that have been associated in Florida with Raffaelea lauricola T.C. Harr., Fraedrich & Aghayeva, the primary symbiont of Xyleborus glabratus Eichhoff and cause of laurel wilt. In total, 14 species in Ambrosiodmus, Euwallacea, Premnobius, Xyleborus, Xyleborinus, and Xylosandrus were either reared from laurel wilt-affected host trees or trapped in laurel wilt-affected stands of the same, and assayed for R. lauricola. In six collections from native species in the southeastern United States [Persea borbonia (L.), Persea palustris (Raf.) Sarg., and Persea humilis Nash] and four from avocado (Persea americana Mill.), extracted mycangia or heads (taxa with mandibular mycangia) or intact bodies (taxa with mycangia in other locations) were surface-disinfested before assays on a semi-selective medium for the isolation of Raffaelea (CSMA+). Raffaelea lauricola was identified based on its characteristic phenotype on CSMA+, and the identity of a random subset of isolates was confirmed with taxon-specific microsatellite markers. The pathogen was recovered from 34% (246 of 726) of the individuals that were associated with the native Persea spp., but only 6% (58 of 931) of those that were associated with avocado. Over all studies, R. lauricola was recovered from 10 of the ambrosia beetle species, but it was most prevalent in Xyleborus congeners. This is the first record of R. lauricola in Ambrosiodmus lecontei Hopkins, Xyleborinus andrewesi (Blandford), and Xyleborus bispinatus Eichhoff. The potential effects of R. lauricola's promiscuity are discussed.

Tropical race 4 of Panama disease in the Middle East

Abstract: Panama disease (aka Fusarium wilt) of banana (Musa spp) has been a destructive problem for well over a century Race 1 of the pathogen, Fusarium oxysporum f sp cubense (Foc), was responsible for the demise of the first export trades of banana that were based on the cultivar ‘Gros Michel’ Currently, tropical race 4 (TR4) impacts the Cavendish cultivars, which are most important in both export and smallholder production TR4 was confirmed in Jordan in 2013, but has probably been present in the country since at least 2005 The outbreak in Jordan was apparently the first occurrence of Panama disease in the Middle East, but it also represented a considerable expansion of TR4’s distribution, which had previously been restricted to the Far East How TR4 arrived in Jordan is not known However, it is clear that TR4 has spread within Jordan, and is now also present elsewhere in the Middle East and Africa We review the history, epidemiology and management of Panama disease, and discuss the current distribution of TR4 and its potential impact on banana production in the Middle East

The genome of Nectria haematococca: contribution of supernumerary chromosomes to gene expansion

Abstract: The ascomycetous fungus Nectria haematococca, (asexual name Fusarium solani), is a member of a group of .50 species known as the Fusarium solani species complex . Members of this complex have diverse biological properties including the ability to cause disease on .100 genera of plants and opportunistic infections in humans. The current research analyzed the most extensively studied member of this complex, N. haematococca mating population VI (MPVI). Several genes controlling the ability of individual isolates of this species to colonize specific habitats are located on supernumerary chromosomes. Optical mapping revealed that the sequenced isolate has 17 chromosomes ranging from 530 kb to 6.52 Mb and that the physical size of the genome, 54.43 Mb, and the number of predicted genes, 15,707, are among the largest reported for ascomycetes. Two classes of genes have contributed to gene expansion: specific genes that are not found in other fungi including its closest sequenced relative, Fusarium graminearum; and genes that commonly occur as single copies in other fungi but are present as multiple copies in N. haematococca MPVI. Some of these additional genes appear to have resulted from gene duplication events, while others may have been acquired through horizontal gene transfer. The supernumerary nature of three chromosomes, 14, 15, and 17, was confirmed by their absence in pulsed field gel electrophoresis experiments of some isolates and by demonstrating that these isolates lacked chromosome-specific sequences found on the ends of these chromosomes. These supernumerary chromosomes contain more repeat sequences, are enriched in unique and duplicated genes, and have a lower G+C content in comparison to the other chromosomes. Although the origin(s) of the extra genes and the supernumerary chromosomes is not known, the gene expansion and its large genome size are consistent with this species' diverse range of habitats. Furthermore, the presence of unique genes on supernumerary chromosomes might account for individual isolates having different environmental niches.

Fusarium Wilt of Banana

Abstract: Banana (Musa spp.) is one of the world's most important fruits. In 2011, 145 million metric tons, worth an estimated $44 billion, were produced in over 130 countries. Fusarium wilt (also known as Panama disease) is one of the most destructive diseases of this crop. It devastated the 'Gros Michel'-based export trades before the mid-1900s, and threatens the Cavendish cultivars that were used to replace it; in total, the latter cultivars are now responsible for approximately 45% of all production. An overview of the disease and its causal agent, Fusarium oxysporum f. sp. cubense, is presented below. Despite a substantial positive literature on biological, chemical, or cultural measures, management is largely restricted to excluding F. oxysporum f. sp. cubense from noninfested areas and using resistant cultivars where the pathogen has established. Resistance to Fusarium wilt is poor in several breeding targets, including important dessert and cooking cultivars. Better resistance to this and other diseases is needed. The history and impact of Fusarium wilt is summarized with an emphasis on tropical race 4 (TR4), a 'Cavendish'-killing variant of the pathogen that has spread dramatically in the Eastern Hemisphere.

Fusarium wilt of banana: Current knowledge on epidemiology and research needs toward sustainable disease management

Abstract: Banana production is seriously threatened by Fusarium wilt (FW), a disease caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc). In the mid-twentieth century FW, also known as "Panama disease", wiped out the Gros Michel banana industry in Central America. The devastation caused by Foc race 1 was mitigated by a shift to resistant Cavendish cultivars, which are currently the source of 99% of banana exports. However, a new strain of Foc, the tropical race 4 (TR4), attacks Cavendish clones and a diverse range of other banana varieties. Foc TR4 has been restricted to East and parts of Southeast Asia for more than 20 years, but since 2010 the disease has spread westward into five additional countries in Southeast and South Asia (Vietnam, Laos, Myanmar, India, and Pakistan) and at the transcontinental level into the Middle East (Oman, Jordan, Lebanon, and Israel) and Africa (Mozambique). The spread of Foc TR4 is of great concern due to the limited knowledge about key aspects of disease epidemiology and the lack of effective management models, including resistant varieties and soil management approaches. In this review we summarize the current knowledge on the epidemiology of FW of banana, highlighting knowledge gaps in pathogen survival and dispersal, factors driving disease intensity, soil and plant microbiome and the dynamics of the disease. Comparisons with FW in other crops were also made to indicate possible differences and commonalities. Our current understanding of the role of main biotic and abiotic factors on disease intensity is reviewed, highlighting research needs and futures directions. Finally, a set of practices and their impact on disease intensity are discussed and proposed as an integrative management approach that could eventually be used by a range of users, including plant protection organizations, researchers, extension workers and growers.

DNA sequence-based identification of Fusarium : Current status and future directions

Abstract: Fusarium ranks as one of the world’s most economically destructive and species-rich groups of mycotoxigenic plant pathogens (Aoki et al. 2014). These ubiquitous molds produce a plethora of toxic secondary metabolites, such as trichothecenes, zearalenone, fumonisins, and enniatins, which pose a significant threat to agricultural biosecurity, food safety, and plant, human and animal health (Marasas et al.1984). Fusarial-induced diseases of virtually every economically important plant cost the global agricultural economy multi-billion euro losses annually. Moreover, phylogenetically diverse fusaria, including plant pathogens (Short et al. 2011), cause infections in humans, with those involving the cornea and nails being the most common (Chang et al.2006 and references therein). Because fusaria are broadly resistant to the spectrum of antifungals currently available, disseminated infections in patients who are artificially immunosuppressed or immunocompromised and severely neutropenic are typically fatal (Balajee et al.2009). The likely reservoir of nosocomial fusarioses is the plumbing system, which has been shown to harbor the most common human opportunistic fusaria (Kuchar 1996; Short et al.2011). Accurate identification of the etiological and/or toxigenic agent is central to disease management and infection control (Wingfield et al. 2012). Thus, the primary focus of this mini-review is to provide a contemporary guide to the following three web-accessible resources for DNA sequence-based identification of Fusarium: FUSARIUM-ID (http://isolate.fusariumdb.org/; Geiser et al.2004; Park et al. 2010), Fusarium MLST (http://www.cbs.knaw.nl/fusarium/; O’Donnell et al.2010), and NCBI GenBank (http://www.ncbi.nlm.nih.gov/). The following brief overview of Fusarium phylogenetic diversity is provided as background information for the sections on DNA sequence-based identification.