Sorghum sheath blight caused by Fusarium spp. in Sinaloa, Mexico

Sorghum (Sorghum bicolor) leaf sheath blight was observed for the first time in Sinaloa, Mexico in the summer of 2020. Fungal isolates were obtained from symptomatic tissue in PDA. Fusarium spp. were associated with symptomatic plants in ten sampling sites under field conditions. No root and stalk rot were observed during the sampling period. Analysis of fragments of the EF-1a and RPB2 genes indicated that all isolates belong to the Fusarium fujikuroi species complex (FFSC). Five groups were delineated from this complex: F. thapsinum, F. verticillioides, Fusarium sp. (four isolates), Fusarium sp. (Fus4), and Fusarium sp. (Fus16), which is closely related to Fusarium madaense. The morphological characteristics (colony color and morphometry of conidia) of isolates with sequence similarities to those of F. thapsinum and F. verticillioides were in the expected range for these species. The morphology of isolates Fus7a, Fus7b, Fus11 and Fus17, as well as Fus4 and Fus16, were similar to those of the FFSC, specially to F. andiyazi and F. madaense. Inoculations of sorghum with representative isolates of F. thapsinum, F. verticillioides and the unidentified Fusarium species resulted in reddish brown lesions similar to those observed under field conditions; the original isolates inoculated were reisolated fulfilling the Koch's postulates. Although leaf sheaths on sorghum plants were heavily damaged, root and stalk rot were not observed in the greenhouse inoculations or under field conditions. Future research should focus on determining the identity of the unknown Fusarium spp. in order to design control measures of the disease. This is the first report of Fusarium spp. causing sorghum leaf sheath blight in Mexico.

Fenhexamid - an efficient and inexpensive fungicide for selection of Magnaporthe oryzae transformants

Magnaporthe oryzae is one of the most economically important phytopathogenic fungi, and is used as a model organism to study plant-pathogen interactions. To unravel the infection process, forward and reverse genetic approaches are essential, but are often hindered by the lack of a straightforward selection procedure for transformants. Here we report on the use of fenhexamid, an inhibitor of ergosterol biosynthesis, for selection of M. oryzae transformants. An allele of the sterol 3-ketoreductase gene of Fusarium fujikuroi (FfERG27), known to confer resistance to fenhexamid, has already been used successfully with transformants of Botrytis cinerea. Our results demonstrate that expression of the FfERG27 allele in M. oryzae also enables highly efficient selection of transformants on fenhexamid-containing media. The use of fenhexamid is an inexpensive alternative for selection as compared to commonly used antibiotics like hygromycin. No impact on growth and infection phenotypes of fenhexamid resistant M. oryzae mutants was detected, which underpins its usefulness for selecting M. oryzae transformants.

Current Status of Fusarium and Their Management Strategies

Fusarium spp. is one of the most economically important plant pathogens causing a wide range of plant diseases with significant crop losses globally. Fusarium wilt is a major problem all over the world. Fusarium oxysporum, Fusarium solani, Fusarium fujikuroi are economic importance species in worldwide. Fusarium solani causing disease in many agriculturally crops and favored by high temperatures and warm moist soils. The fungus produces three types of asexual spores; microconidia, macroconidia and chlamydospores serve as propagules in infecting host plants and found endophytes and saprophytes. The color of the colony, length and shape of the macroconidia, the number shape of microconidia and the presence or absence of chlamydospores are key features for the differentiation of Fusarium species. Pathogens, forms over 100 formae speciales cause disease in dicot and monocot plant species and infecting a variety of hosts. Vegetative compatibility Groups (VCG) is used to differentiate their races. Resistant cultivars and bio-control agents (Trichoderma spp., and Psedomonas spp.) have been used to manage the disease.

Fusarium casha sp. nov. and F. curculicola sp. nov. in the Fusarium fujikuroi Species Complex Isolated from Amaranthuscruentus and Three Weevil Species in South Africa

Trials are currently being conducted in South Africa to establish Amaranthus cruentus as a new pseudocereal crop. During recent surveys, Fusarium species were associated with weevil damage in A. cruentus fields. Preliminary studies showed that some of these Fusarium species grouped into two distinct clades within the F. fujikuroi species complex. The aim of this study was to characterize these isolates based on the morphology and phylogeny of the translation elongation factor 1α (TEF1α) gene region, ß-tubulin 2 (ßT) gene region and RNA polymerase II subunit (RPB2), and to determine if these isolates are pathogenic to A. cruentus. Phylogenetic and morphological studies showed that these two clades represent two novel species described here as F. casha and F. curculicola. Both species were shown to have the potential to be pathogenic to A. cruentus during routine greenhouse inoculation tests. While isolations indicate a possible association between these two species and weevils, further research is needed to understand this association and the role of weevils in disease development involving F. casha and F. curculicola in A. cruentus.

عزل وتشخيص الفطريات داخل النبات وتقييم كفاءتها في مقاومة مرضي التعفن الأبيض وموت البادرات على الطماطم

تناولت الدراسة عزل فطريات داخل النبات من المجموعين الجذري والخضري لنباتات الطماطم المأخوذة من ثلاث مناطق مختلفة ضمن حدود محافظة صلاح الدين شملت أقضية بيجي والعلم والشرقاط. أُجريت إِختبارات التضاد للعزلات الفطرية مع الممرضين Sclerotinia sclerotiorum وPythium aphanidermatum باستخدام طريقة الزراعة المزدوجة وأظهرت نتائج التضاد أن أعلى تثبيط للعزلتين SLC1 و ALS6سجل ضد الممرض P.aphanidermatum وبنسبة تثبيط بلغت 75%.أما العزلات الفطرية BSR3 وBRM3 و SRS2حققت أعلى فعالية تضاد تجاه الممرض S.sclerotiorum وبنسبة تثبيط بلغت 75% في المزرعة المزدوجة. شخصت العزلة الفطرية التي اعطت توافق في تضادها ضد الفطريين الممرضين على مستوى النوع ARC3 Fusarium fujikuroi. أوضحت نتائج التجربة الحقلية تأثير هذا الفطر في المعايير الخضرية الى تفوق معنوي لمحتوى نباتات الطماطة من الكلوروفيل في معاملة الفطر (ري + رش تركيز1010 كونيدة/مل) بوجود الفطرين الممرضين P. aphanidermatum و S. sclerotiorum إذ بلغ 36.74 و34.66 سباد، على التتابع مقارنة بأدنى القيم في معاملة الممرضين فقط والتي بلغ فيهما محتوى الكلوروفيل 25.74 و23.21 سباد على التتابع. كما أبدت معاملة الفطر نفسها أعلى معدل ارتفاع للنبات وأوضحت نتائج تأثير الفطر ARC3 في نسبة إصابة النبات بوجود الفطرين الممرضين P. aphanidermatum و S. sclerotiorum تفوقاً معنوياً في خفض نسبة الإصابة في معاملة الفطر ( ري + رش تركيز1010 كونيدة/مل )، إذ بلغت 15.14 و19.27% على التتابع مقارنة بأعلى قيم لنسبة الإصابة والتي بلغت 86.83 و 78.71% في معاملات الممرضين فقط، على التتابع.

Fusarium musae from Diseased Bananas and Human Patients: Susceptibility to Fungicides Used in Clinical and Agricultural Settings

Fusarium musae belongs to the Fusarium fujikuroi species complex. It causes crown rot disease in banana but also keratitis and skin infections as well as systemic infections in immunocompromised patients. Antifungal treatments in clinical and agricultural settings rely mostly on molecules belonging to the azole class. Given the potential risk of pathogen spread from food to clinical settings, the goal of the work was to define the level of susceptibility to different azoles of a worldwide population of F. musae. Eight fungicides used in agriculture and five antifungals used in clinical settings (4 azoles and amphotericin B) were tested using the CLSI (Clinical and Laboratory Standards Institute) protocol methodology on 19 F. musae strains collected from both infected patients and bananas. The level of susceptibility to the different active molecules was not dependent on the source of isolation with the exception of fenbuconazole and difenoconazole which had a higher efficiency on banana-isolated strains. Minimal inhibitory concentrations (MICs) of the different molecules ranged from 0.12–0.25 mg/L for prochloraz to more than 16 mg/L for tetraconazole and fenbuconazole. Compared to the F. verticillioides, F. musae MICs were higher suggesting the importance of monitoring the potential future spread of this species also in clinical settings.

Molecular diagnosis of thiophanate-methyl resistant strains of Fusarium fujikuroi in Japan

Fusarium fujikuroi is the pathogen of rice bakanae disease, and is subclassified into gibberellin and fumonisin groups (G- and F-groups). Thiophanate-methyl, a benzimidazole fungicide, has been used extensively to control F. fujikuroi. Previous investigation showed that F-group strains are thiophanate-methyl sensitive (TMS), while most G-group strains are thiophanate-methyl resistant (TMR) in Japan. The minimum inhibitory concentration (MIC) in TMS strains was 1–10 μg mL-1, while that in TMR strains was higher than 100 μg mL-1. E198K and F200Y mutations in β2-tubulin were detected in TMR strains. A loop-mediated isothermal amplification-fluorescent loop primer (LAMP-FLP) method was developed for diagnosis of these mutations, and was applied to 37 TMR strains and 56 TMS strains. The result indicated that 100% of TMR strains were identified as having either the E198K mutation (41%) or the F200Y mutation (59%), while none of the TMS strains tested showed either mutation. We found one remarkable TMR strain in the F-group which had a F200Y mutation. These results suggest that E198K and F200Y mutations in β2-tubulin contribute to thiophanate-methyl resistance in F. fujikuroi.

Telomere to telomere genome assembly of Fusarium musae F31, causal agent of crown rot disease of banana.

Fusarium musae van Hove causes crown rot of banana and it is also associated to clinical fusariosis. A chromosome-level genome assembly of Fusarium musae F31 obtained combining Nanopore long reads and Illumina paired end reads resulted in 12 chromosomes plus one contig with overall N50 of 4.36 Mb, and is presented together with its mitochondrial genome (58072 bp). F31 genome includes telomeric regions for 11 of the 12 chromosomes representing the most complete genome available in the Fusarium fujikuroi species complex. The high-quality assembly of the F31 genome will be a valuable resource for studying the pathogenic interactions occurring between F. musae and banana. Moreover, it represents an important resource for understanding the genome evolution in the Fusarium fujikuroi species complex.

Optimization of a Loop-Mediated Isothermal Amplification Assay for On-Site Detection of Fusarium fujikuroi in Rice Seed

Fusarium fujikuroi, causing bakanae disease, is one of the most important seedborne pathogens of rice, the detection of which is paramount for seed certification and for preventing field infections. Molecular tests—qPCR and loop-mediated isothermal amplification (LAMP)—are replacing the blotter test in seed health procedures, due to higher sensitivity, specificity, fast turnaround results delivery, on-site application and the possibility of quantifying endophytic seed infections. A LAMP test, which had been previously developed with primers designed to target the elongation factor 1-α sequence of F. fujikuroi, was validated according to the international validation standard (EPPO, PM7/98) on thirty-four rice seed lines of different levels of susceptibility to the disease, thus comparing it to the blotter test and with two different DNA extraction procedures. The use of crude extracted DNA provided more sensitive results than the DNA extracted with the commercial kit Omega E.Z.N.A® Plant DNA kit. The results showed that the endophytic infection of F. fujikuroi is essential for the development of the disease in the field and that the minimum amount of the pathogen necessary for the development of the disease corresponds to 4.17 × 104 cells/µL. This study confirms the applicability of the LAMP technique on-site on rice seeds with fast and quantitative detection of the pathogen.