Browsing by Author "Chen, W."

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Characterization of Ascochyta rabiei for population structure, mating type and pathogenic variability from Pakistan and United States
(III international Ascochyta workshop, Cordoba, Spain, 2012) Hinaali, A.S.S.; Attanayake, R.N.; Rahman, M.; Chen, W.
Chickpea production is greatly hampered by blight causing fungal pathogen Ascochyta rabiei (AR) in chickpea growing regions of the world. Genetic variability and mating type frequency of thirty two AR isolates from six geographical regions of Pakistan were compared with a US-AR population. Pakistani AR (PAR) population had an apparent skewed (3 Mat1-2: 1 Mat1-1) distribution, although Chi-square tests showed non significant deviation from equal distribution due to small sample sizes and the US-population showed a 1:1 distribution. The results showed that sexual reproduction is rare in PAR due to either unavailability of both mating types or lack of conductive environment but statistical analysis showed panmixia which may be due to past recombinational events. Genetic variation at six microsatellite loci was assessed and each isolate was assigned to a microsatellite haplotype. Population structure using Bayesian analyses differentiated isolates into three distinct clusters, two clusters of PAR and one of the US isolates. However, few isolates from US shared same genetic background with one cluster of the PAR isolates, providing a link of inter-continental migration of the pathogen due to import of seeds. Additionally, the two clusters of Pak-isolates are not strictly linked to the geographic locations in Pakistan, suggesting frequent gene flow of AR among different locations. Pathogenic variability of nineteen PAR collected from two different provinces was assessed. The results based on the reaction of isolates with differential lines showed that aggressive and highly aggressive pathotypes II and III respectively are prevalent in Pakistan as compared to least aggressive pathotype I. It is interesting to note that highly aggressive pathotypes III and IV have only beenreported from Syria and Pakistan where we assume less frequency of sexual reproduction due to predominance of one mating type, in contrast to other countries where both mating types are present in equal ratio hence, this issue needs further investigations.
Detection of intrachromosomal recombination in Sclerotinia sclerotiorum populations
(Phytopathology, 2012) Attanayake, R.N.; Chen, W.
Genetic structure and reproductive mode of the homothallic fungal pathogen Sclerotinia sclerotiorum have been widely studied using linkage disequilibrium (LD) tests with putatively unlinked molecular markers. We previously observed random association between linked loci in S. sclerotiorum populations suggesting intrachromosomal recombination or high mutation rates at these loci. This study was aimed at testing intrachromosomal recombination using 12 microsatellite loci distributed over four chromosomes. Two hundred thirty isolates sampled from seven populations in the USA and China from a variety of crops were genotyped. Each isolate carried a single allele for each of the 12 loci suggesting the isolates were haploid and homokaryotic. Pairwise LD tests of all the intrachromosomal loci showed relationship ranged from linked to random association, and in many cases LD declined with increasing physical distance between loci. Thus the random associations of alleles cannot be simply attributed to random mutation. Majority of the isolates were mycelially incompatible, likely minimizing the possibility of heterokaryon formation and mitotic recombination. Thus the observed high intrachromosomal recombination is most likely due to meiotic recombination following outcross in these populations.
Erysiphe trifolii Causing Powdery Mildew of Lentil (Lens culinaris)
(Plant Disease, 2009) Attanayake, R.N.; Glawe, D.A.; Dugan, F.M.; Chen, W.
The taxonomy of the powdery mildew fungus infecting lentil in the Pacific Northwest (PNW) of the United States was investigated on the basis of morphology and rDNA internal transcribed spacer (ITS) sequences. Anamorphic characters were in close agreement with descriptions of Erysiphe trifolii. However, teleomorphs formed chasmothecial appendages with highly branched apices, whereas E. trifolii has been described as producing flexuous or sometimes loosely branched appendages. Branched appendages have been described in Erysiphe diffusa, a fungus reported from species of Lens, Glycine, and Sophora, raising the possibility that the PNW fungus could be E. diffusa. Examination of morphological characters of an authentic specimen of E. trifolii from Austria determined that it included chasmothecial appendages resembling those seen in PNW specimens. Furthermore, ITS sequences from five powdery mildew samples collected from lentils in PNW greenhouses and fields from 2006 to 2008 were identical to one another, and exhibited higher similarity to sequences of E. trifolii (99%) than to those of any other Erysiphe spp. available in GenBank. Parsimony analysis grouped the lentil powdery mildew into a clade with Erysiphe baeumleri, E. trifolii, and E. trifolii?like Oidium sp., but indicated a more distant relationship to E. diffusa. In greenhouse inoculation studies, the lentil powdery mildew fungus did not infect soybean genotypes known to be susceptible to E. diffusa. The pathogenicity of E. trifolii on lentil was confirmed using modified Koch's postulates. This is the first report of E. trifolii infecting lentil. E. diffusa and E. trifolii have different host ranges, so the discovery of E. trifolii on lentil has implications both for determining species of powdery mildews on cool-season grain legumes, and in disease management.
Erysiphe trifolii? a newly recognized powdery mildew pathogen of pea
(Plant Pathology, 2010) Attanayake, R.N.; Glawe, D.A.; McPhee, K.E.; Dugan, F.M.; Chen, W.
Diversity of powdery mildew pathogens infecting pea (Pisum sativum) in the US Pacific Northwest was investigated using both molecular and morphological techniques. Phylogenetic analyses based on rDNA ITS sequences, in combination with assessment of morphological characters, defined two groups of powdery mildews infecting pea. Group I (five field samples and three glasshouse samples) had ITS sequences 99% similar to those of Erysiphe pisi in GenBank and exhibited simple, mycelioid type of chasmothecial appendages typical of E. pisi. Erysiphe pisi is normally considered as the powdery mildew pathogen of pea. Group II (four glasshouse samples and two field samples) had ITS sequences 99% similar to those of E. trifolii and produced chasmothecia with dichotomously branched appendages similar to those of E. trifolii. There are fourteen nucleotide differences in the ITS region between the two groups. The correlation of rDNA ITS sequences with teleomorphic features for each of the two groups confirms their identity. Repeated samplings and artificial inoculations indicate that both E. pisi and E. trifolii infect pea in the US Pacific Northwest. Erysiphe trifolii is not previously known as a pathogen of pea. The existence of two distinct powdery mildew species infecting pea in both glasshouse and field environments may interfere with the powdery mildew-resistance breeding programmes, and possibly explains putative instances of breakdown of resistance in previously resistant pea breeding lines.
First Report of Powdery Mildew of Chickpea (Cicer arietinum) Caused by Leveillula taurica in Washington State
(Plant Health Progress, 2008) Chen, W.; Attanayake, R.N.; Glawe, D.A.; McPhee, K.E.; Dugan, F.M.
In Oct. 2007, powdery mildew was found in chickpea fields in an experimental farm near Pullman, Whitman County, Washington. Although disease signs were observed on all chickpea cultivars in the fields, high incidence was seen only on cvs. Dwelley and Spanish White. To our knowledge this is the first record of powdery mildew caused by Leveillula taurica on chickpea in WA. The pathogen has also been reported from chickpea in California and elsewhere, e.g., Ethiopia, India, Iran, Morocco, Pakistan, Sudan, Turkey, and the former USSR.
Genetic and phenotypic divergence of the Sclerotiniasclerotiorum populations from China and USA
(Phytopathology, 2013) Attanayake, R.N.; Carter, P.A.; Jiang, D.H.; Río-Mendoza, L.D.; Chen, W.
Genetic and phenotypic diversity and population differentiation of Sclerotinia sclerotiorum isolates infecting canola from China and the United States were investigated. Genetic diversity was assessed with eight microsatellite markers and mycelial compatibility groups (MCGs). Phenotypic diversity was assessed with sensitivity to three fungicides, production of oxalate and sclerotia, growth rate, and virulence on two canola cultivars. No shared MCGs or multilocus haplotypes were detected between the two populations, and populations differed significantly (P < 0.001). Recombination was detected in both populations but was greater in the Chinese population. A polymerase chain reaction detection assay showed that ~60% of the isolates were inversion-plus at the mating type locus. The two populations differed significantly (P < 0.05) for all of the phenotypic traits except for sensitivity to fungicide fluazinam and virulence. Isolates in the Chinese population were unique in several aspects. Despite the phenotypic differentiation, heritabilities of the phenotypic traits were similar for both populations. Significant correlations were found among five phenotypic traits. Cross resistance to benomyl and iprodione was detected. Virulence was not significantly correlated with any other phenotypic trait and had the least heritability. However, both populations were equally virulent on either a susceptible or a moderately resistant canola cultivars.
Genetic and phenotypic diversity and random association of DNA markers of isolates of the fungal plant pathogen Sclerotinia sclerotiorum from soil on a fine geographic scale
(Soil Biology and Biochemistry, 2012) Chen, W.; Johnson, D.A.; Porter, L.; Attanayake, R.N.
Sclerotia of the soil-borne plant pathogen Sclerotinia sclerotiorum were collected from 1 m2 area of the top 1.27 cm layer of soil in an alfalfa field in southeastern Washington state of the US. Out of 272 sclerotia collected, 40 were randomly selected and analyzed for genetic diversity in terms of microsatellite loci, mycelial compatibility groups (MCGs) and phenotypic diversity using five phenotypic traits (fungicide sensitivity, oxalic acid production, growth rate, colony color and virulence). Sixteen microsatellite haplotypes and 15 MCGs were found among the 40 isolates. The isolates showed three colony colors (beige, dark and white) on Difco PDA and exhibited significant differences in growth rate, oxalic acid production, and sensitivity to three fungicides, benomyl, fluazinam and iprodione. However, these isolates did not show differences in their ability to colonize detached pea leaves. No apparent relationship among the neutral genetic markers and the phenotypic traits was detected. Two of the haplotypes accounted 40% of the isolates, suggesting isolates of these haplotypes might be better adapted to the environmental conditions in this alfalfa field. Several lines of evidence indicated high levels of genetic diversity and potential outcrossing within the population of S. sclerotiorum: 1) high likelihood of five genetic populations based on Bayesian probability and the presence of admixed isolates; 2) random association of alleles in every pair-wise linkage disequilibrium test among eight independent microsatellite loci; 3) discordances between microsatellite haplotypes and MCGs and 4) lack of correspondence among the genetic markers and phenotypic traits. Multilocus Index of Association test suggested that outcrossing occurs only within interbreeding subpopulations of S. sclerotiorum.
Genetic diversity and population differentiation of Sclerotinia sclerotiorum collected from canola in China and in U.S.A.
(Phytopathology, 2011) Attanayake, R.N.; del Río-Mendoza, L.; Chen, W.; Jiang, D.
Sclerotinia sclerotiorum is an important pathogen of canola and many other crops worldwide. Genetic diversity and population differentiation of S. sclerotiorum collected from canola fields in Anhui Province, China (30 isolates) and in North Dakota, U.S.A. (29 isolates) were investigated in terms of genetic variation in 8 simple sequence repeat (SSR) marker loci, mycelial compatibility groups (MCGs) and three phenotypic traits: sensitivity to fungicides benomyl, iprodione and fluzinam, oxalic acid production, and pathogenicity. Significant genetic differences were observed; there were no shared SSR haplotypes and no shared MCGs between the two populations. Population differentiation was significant (p = 0.000) indicating lack of gene flow between the two populations. There were also significant differences between the two populations in oxalic acid production and in fungicide sensitivity. The Chinese population displayed high levels of insensitivity (faster growth rate) to benomyl and fluzinam and higher levels of oxalic acid production per unit dry weight of mycelium than did the U.S. population. However, there was no significant difference in pathogenicity between the two populations as measured by colonization of detached canola leaves. Data Vol. 101, No. 6 (Supplement), 2011 S11 suggest that despite geographic and genetic isolation the two populations of S. sclerotiorum were equally adapted to colonizing canola plants, and pathogenicity is under different selection pressure than the other genetic and phenotypic traits.
A global survey on the use of the international classification of diseases codes for metabolic dysfunction-associated fatty liver disease
(Springer, 2024) Zhang, H.; Targher, G.; Byrne, C.D.; Kim, S.U.; Wong, V.W.; Valenti, L.; Glickman, M.; Ponce, J.; Mantzoros, C.S.; Crespo, J.; Gronbaek, H.; Yang, W.; Eslam, M.; Wong, R.J.; Machado, M.V.; Yu, M.; Ghanem, O.M.; Okanoue, T.; Liu, J.; Lee, Y.; Xu, X.; Pan, Q.; Sui, M.; Lonardo, A.; Yilmaz, Y.; Zhu, L.; Moreno, C.; Miele, L.; Lupsor-Platon, M.; Zhao, L.; LaMasters, T.L.; Gish, R.G.; Zhang, H.; Nedelcu, M.; Chan, W.K.; Xia, M.; Bril, F.; Shi, J.; Datz, C.; Romeo, S.; Sun, J.; Liu, D.; Sookoian, S.; Mao, Y.; Méndez-Sánchez, N.; Wang, X.; Pyrsopoulos, N.T.; Fan, J.; Fouad, Y.; Sun, D.; Giannini, C.; Chai, J.; Xia, Z.; Jun, D.W.; Li, G.; Treeprasertsuk, S.; Li, Y.; Cheung, T.T.; Zhang, F.; Goh, G.B.; Furuhashi, M.; Seto, W.; Huang, H.; Sessa, A.D.; Li, Q.; Cholongitas, E.; Zhang, L.; Silveira, T.R.; Sebastiani, G.; Adams, L.A.; Chen, W.; Qi, X.; Rankovic, I.; Ledinghen, V.D.; Lv, W.; Hamaguchi, M.; Kassir, R.; Müller-Wieland, D.; Romero-Gomez, M.; Xu, Y.; Xu, Y.; Chen, S.; Kermansaravi, M.; Kuchay, M.S.; Lefere, S.; Parmar, C.; Lip, G.Y.H.; Liu, C.; Åberg, F.; Lau, G.; George, J.; Sarin, S.K.; Zhou, J.; Zheng, M.; Niriella, M.A. (MAFLD ICD-11 coding collaborators)
BACKGROUND With the implementation of the 11th edition of the International Classification of Diseases (ICD-11) and the publication of the metabolic dysfunction-associated fatty liver disease (MAFLD) nomenclature in 2020, it is important to establish consensus for the coding of MAFLD in ICD-11. This will inform subsequent revisions of ICD-11.METHODS Using the Qualtrics XM and WJX platforms, questionnaires were sent online to MAFLD-ICD-11 coding collaborators, authors of papers, and relevant association members.RESULTS A total of 890 international experts in various fields from 61 countries responded to the survey. We also achieved full coverage of provincial-level administrative regions in China. 77.1% of respondents agreed that MAFLD should be represented in ICD-11 by updating NAFLD, with no significant regional differences (77.3% in Asia and 76.6% in non-Asia, p = 0.819). Over 80% of respondents agreed or somewhat agreed with the need to assign specific codes for progressive stages of MAFLD (i.e. steatohepatitis) (92.2%), MAFLD combined with comorbidities (84.1%), or MAFLD subtypes (i.e., lean, overweight/obese, and diabetic) (86.1%).CONCLUSIONS This global survey by a collaborative panel of clinical, coding, health management and policy experts, indicates agreement that MAFLD should be coded in ICD-11. The data serves as a foundation for corresponding adjustments in the ICD-11 revision.
Inferring outcrossing in the homothallic fungus Sclerotinia sclerotiorum using linkage disequilibrium decay
(Heredity, 2014) Attanayake, R.N.; Tennekoon, V.; Johnson, D.A.; Porter, L.D.; del Río-Mendoza, L.; Jiang, D.; Chen, W.
The occurrence and frequency of outcrossing in homothallic fungal species in nature is an unresolved question. Here we report detection of frequent outcrossing in the homothallic fungus Sclerotinia sclerotiorum. In using multilocus linkage disequilibrium (LD) to infer recombination among microsatellite alleles, high mutation rates confound the estimates of recombination. To distinguish high mutation rates from recombination to infer outcrossing, 8 population samples comprising 268 S. sclerotiorum isolates from widely distributed agricultural fields were genotyped for 12 microsatellite markers, resulting in multiple polymorphic markers on three chromosomes. Each isolate was homokaryotic for the 12 loci. Pairwise LD was estimated using three methods: Fisher?s exact test, index of association (IA) and Hedrick?s D?. For most of the populations, pairwise LD decayed with increasing physical distance between loci in two of the three chromosomes. Therefore, the observed recombination of alleles cannot be simply attributed to mutation alone. Different recombination rates in various DNA regions (recombination hot/cold spots) and different evolutionary histories of the populations could explain the observed differences in rates of LD decay among the chromosomes and among populations. The majority of the isolates exhibited mycelial incompatibility, minimizing the possibility of heterokaryon formation and mitotic recombination. Thus, the observed high intrachromosomal recombination is due to meiotic recombination, suggesting frequent outcrossing in these populations, supporting the view that homothallism favors universal compatibility of gametes instead of traditionally believed haploid selfing in S. sclerotiorum. Frequent outcrossing facilitates emergence and spread of new traits such as fungicide resistance, increasing difficulties in managing Sclerotinia diseases.
Pair-wise linkage disequilibrium decay among linked loci suggests meiotic recombination in natural populations of Sclerotinia sclerotiorum
(Asilomar Conference Grounds, 2013) Attanayake, R.N.; Chen, W.
Both clonal and recombining population structures have been reported in Sclerotinia sclerotiorum populations around the world. Association of independent and putatively unlinked markers indicates clonal population structure, whereas random association of the markers suggests recombination and outcrossing. However, high mutation rates of markers used for inference, like certain microsatellite markers, could interfere and compromise the inferences of recombination and outcrossing. To test if the recombination is due to outcrossing or mutation, we used 12 microsatellite loci distributed over four chromosomes to genotype 230 isolates sampled from seven populations in the USA and China from a variety of crops. All the isolates produced single alleles for each of the loci tested, indicating all the isolates were homokaryotic for the microsatellite loci in consideration. Pair-wise linkage disequilibrium (LD) tests (Hedrick?s D, Fishers exact test and IA) between physically linked loci showed relationships ranging from linked to random association with increasing distance between loci on three chromosomes. For the three loci on chromosome four, LD decay with increasing physical distance between loci was found in six of the seven populations.
Population structure and mating type distribution of the chickpea blight pathogen Ascochytarabiei form Pakistan and the United States
(Journal of plant pathology, 2012) Ali, H.; Alam, S.S.; Attanayake, R.N.; Rahman, M.; Chen, W.
Ascochyta blight caused by the fungus Ascochyta rabiei (AR) depresses chickpea production in Pakistan and worldwide. Thirty two AR isolates representing six geographical regions of Pakistan were compared with a US-AR population for mating type frequency and genetic variation. Mating type results showed that the Pakistani AR (PAR) population had an apparent skewed (3 Mat1-2: 1 Mat1-1) distribution, although Chi-square tests showed non-significant deviation from equal distribution due to small sample sizes. The US population showed a 1:1 distribution of the two mating types. The uneven distribution of mating types indicates that sexual reproduction among the PAR is rare due to either unavailability of both mating types or lack of conducive environment, but statistical analysis showed that panmixia is there reflecting past recombinational events. Genetic variation at six microsatellite loci was assessed and each isolate was assigned to a microsatellite haplotype. Population structure of the isolates was inferred using Bayesian analyses implemented in the structure software which differentiated isolates into three distinct clusters, two clusters of PAR and one of the US isolates. However, few isolates from the US shared the same genetic background with one cluster of the PAR isolates, providing a link of inter-continental migration of the pathogen. Additionally, the two clusters of PAR-isolates are not strictly associated with geographic locations in Pakistan, suggesting frequent gene flow of AR among different locations. Future studies should extend the sampling of representative populations to overcome the limitations of the small sample size for more accurate assessment of population structure.
Potential alternative hosts for a powdery mildew on pea
(Phytopathology, 2009) Attanayake, R.N.; Glawe, D.A.; Dugan, F.M.; Chen, W.
Powdery mildew of pea (Pisum sativum) is an important disease in the field and in the greenhouse. The most widely documented powdery mildew on pea is Erysiphe pisi, but E. trifolii and E. baeumleri have also been reported. From greenhouse-grown peas, we obtained powdery mildew samples with rDNA ITS sequences nearly identical to previously deposited sequences of E. trifolii. Because detailed studies on host range of this pea powdery mildew in the US Pacific Northwest were lacking, we tested common legume plants from the region as potential alternative hosts. Eleven species were used in greenhouse cross inoculation studies: Lens culinaris, Glycine max, Melilotus albus, M. officinalis, Medicago polymorpha, M. lupulina, M. scutellata, Lathyrus latifolius, Trifolium pratense, Vicia cracca, and V. faba. Except for Glycine max, all the plant species tested developed powdery mildew lesions in 10?14 days after inoculation. Susceptibilities of two of these species (L. culinaris and M. albus) were also confirmed with detached leaf assays. Results showed that all the above legumes (except soybean) are potential alternative hosts for the E. trifolii found on pea. Powdery mildews found on wild legumes (Meliotus albus and Medicago lupulina) were also confirmed to be E. trifolii, suggesting that the wild legumes could be inoculum sources of powdery mildew on greenhouse pea plants during winter months. These findings have implications in managing powdery mildew of pea.
RNA N6-Methyladenosine (m6A) Methyltransferase-like 3 Facilitates Tumorigenesis and Cisplatin Resistance of Arecoline-Exposed Oral Carcinoma
(Cells, 2022) Wang, C.; Kadigamuwa, C.; Wu, S.; Gao, Y.; Chen, W.; Gu, Y.; Wang, S.; Li, X.
Background: Arecoline is known as the main active carcinogen found in areca nut extract that drives the pathological progression of oral squamous cell carcinoma (OSCC). Studies have revealed that dysregulation of RNA N6-methyladenosine (m6A) methyltransferase components is intimately linked to cancer initiation and progression, including oral cancer. Methods: The arecoline-induced dysregulated methyltransferase-like 3 (METTL3) gene was identified using RNA-seq transcriptome assay. Using in vitro and in vivo models, the biological roles of METTL3 in arecoline-transformed oral cancer were examined. Results: We found that METTL3 was markedly elevated in arecoline-exposed OSCC cell lines and OSCC tissues of areca nut chewers. We identified that hypoxia-inducible factor 1-alpha (HIF-1↵) stimulated METTL3 expression at the transcriptional level and further proved that METTL3-MYC-HIF-1↵ formed a positive autoregulation loop in arecolinetransformed OSCC cells. Subsequently, we manifested that METTL3 depletion profoundly reduced cell proliferation, cell migration, oncogenicity, and cisplatin resistance of arecoline-exposed OSCC cells. Conclusions: Developing novel strategies to target METTL3 may be a potential way to treat OSCC patients, particularly those with areca nut chewing history and receiving cisplatin treatment.
Sclerotinia sclerotiorum Populations Infecting Canola from China and the United States Are Genetically and Phenotypically Distinct
(Population Biology, 2013) Chen, W.; Attanayake, R.N.; Carter, P.A.; Jiang, D.; del Río-Mendoza, L.; Weidong
Genetic and phenotypic diversity and population differentiation of Sclerotinia sclerotiorum isolates infecting canola from China and the United States were investigated. Genetic diversity was assessed with eight microsatellite markers and mycelial compatibility groups (MCGs). Phenotypic diversity was assessed with sensitivity to three fungicides, production of oxalate and sclerotia, growth rate, and virulence on two canola cultivars. No shared MCGs or multilocus haplotypes were detected between the two populations, and populations differed significantly (P < 0.001). Recombination was detected in both populations but was greater in the Chinese population. A polymerase chain reaction detection assay showed that ~60% of the isolates were inversion-plus at the mating type locus. The two populations differed significantly (P < 0.05) for all of the phenotypic traits except for sensitivity to fungicide fluazinam and virulence. Isolates in the Chinese population were unique in several aspects. Despite the phenotypic differentiation, heritabilities of the phenotypic traits were similar for both populations. Significant correlations were found among five phenotypic traits. Cross resistance to benomyl and iprodione was detected. Virulence was not significantly correlated with any other phenotypic trait and had the least heritability. However, both populations were equally virulent on either a susceptible or a moderately resistant canola cultivars.
Sclerotinia sclerotiorum populations: clonal or recombining?
(Tropical Plant Pathology (2019) 44:23–31., 2019) Attanayake, R.N.; Xu, L.; Chen, W.
Sclerotinia sclerotiorum, a homothallic plant pathogen, undergoes sexual reproduction via haploid selfing (equivalent to clonal reproduction), and produces long-lasting surviving vegetative structures called sclerotia, enhancing clonal persistence and spread. Thus it is not surprising to detect clones of the species. Whether outcrossing can occur in the homothallic S. sclerotiorum remains unanswered. Early studies showed that S. sclerotiorum has a clonal population structure, consistent with its life history traits. However, recent studies using polymorphic and co-dominant molecular markers showed frequent genetic recombination, suggesting outcrossing. This review focuses on recent developments in population genetics studies related to detecting recombination, random association of alleles and dynamic mating type (MAT) alleles in Sclerotinia. Despite frequent reports of random association of alleles, the mechanisms for outcrossing in a homothallic species remain elusive. Recent intriguing findings are: the MAT genes in Sclerotinia are subject to inversion or deletion in every meiotic generation, the MAT gene deletion is related to ascospore dimorphism and mating type switching in S. trifoliorum, and ascospore dimorphism was also observed in S. sclerotiorum. Determining the nature of the dimorphic ascospores and their prevalence in relation to environmental cues could significantly advance our understanding how S. sclerotiorum populations behave in nature
Taxonomic complexity of powdery mildew pathogens found on lentil and pea in the U.S. Pacific Northwest
(Phytopathology, 2008) Attanayake, R.N.; Glawe, D.A.; McPhee, K.E.; Dugan, F.M.; Chen, W.
and field production conditions in the U.S. Pacific Northwest was investigated using morphological and molecular characters. Isolates collected from lentil plants grown in the greenhouse or field displayed morphologies in substantial agreement with descriptions of Erysiphe trifolii, but sometimes with more extensively branched chasmothecial appendages resembling those of E. diffusa. ITS sequences of the lentil fungi were identical to each other, and more similar to GenBank accessions of E. trifolii (99.5%) than of E. diffusa (97%). The data suggest there may be more than one Erysiphe species causing lentil powdery mildew. The fungus on field-grown pea plants was determined to be E. pisi. However, powdery mildew samples obtained from greenhouse pea plants were either E. pisi or E. trofolii depending on the time of sampling and greenhouse location. Therefore, the powdery mildews infecting lentil and pea are more diverse than previously assumed. Powdery mildews from black medic (Medicago sp.) and sweet clover (Melilotus sp.) found near the greenhouses exhibited ITS sequences with 99.9 to 100% similarity to isolates from lentil and pea in the greenhouses, and to isolates from lentil from the field. These weedy legumes could be inoculum sources for powdery mildew of lentil and pea in the greenhouses, and serve as alternative hosts for cultivated legumes.
The Importance of Reporting New Host-Fungus Records for Ornamental and Regional Crops
(Peer-Reviewed by Plant Health Progress, 2009) Dugan, F.M.; Glawe, D.A.; Attanayake, R.N.; Chen, W.
Accurate and timely reports of new host-fungus records are essential for diagnostics and identification, management, and prevention of plant diseases. Important also are venues to publish these reports in a timely manner and the ability to rapidly search for the information contained in these reports. Presented herein are examples of first reports of fungal pathogens on regional crops, including ornamentals and turf grasses, which illustrate how first reports contribute to preparedness, accurate diagnostics, and knowledge of biogeography and host range. We provide a guide to sources of host-fungus records, discuss venues for publishing new records, and review the information important in a new record, including deposition of voucher specimens. We appeal to plant health professionals to increase their efforts of discovering, documenting, and reporting new records.