scholarly journals High Genetic Diversity in Predominantly Clonal Populations of the Powdery Mildew Fungus Podosphaera leucotricha from U.S. Apple Orchards

2021 ◽  
Author(s):  
Lederson Gañán-Betancur ◽  
Tobin L. Peever ◽  
Kate Evans ◽  
Achour Amiri
Keyword(s):  
New York ◽  
Powdery Mildew ◽  
Resistance Gene ◽  
Mating Type ◽  
Genetic Heterogeneity ◽  
Population Biology ◽  
Plant Diseases ◽  
Apple Orchards ◽  
Podosphaera Leucotricha ◽  
Major Resistance Gene

Apple powdery mildew (APM), caused by Podosphaera leucotricha, is a constant threat to apple production worldwide. Very little is known about the biology and population structure of this pathogen in the USA and other growing regions, which impacts APM management. Two hundred fifty-three P. leucotricha isolates, sampled from 10 apple orchards in Washington, New York, and Virginia, were genetically characterized with novel single sequence repeat and mating type markers. Eighty-three multilocus genotypes (MLGs) were identified, most of which were unique to a given orchard. Each isolate carried either a MAT1-1 or MAT1-2 idiomorph at the mating type locus, indicating that P. leucotricha is heterothallic. Virulence tests on detached apple leaves showed that the 10 most frequent P. leucotricha MLGs were not avirulent on a line containing a major resistance gene. Analysis of molecular variance showed significant differentiation (P > 0.001) among populations, a result supported by principal coordinate analysis revealing three genetic groups, each represented by non-overlapping MLGs from Washington, New York, and Virginia. A Bayesian cluster analysis showed genetic heterogeneity between Washington populations, and a relative migration analysis indicated substantial gene flow among neighboring orchards. Random mating tests indicated that APM epidemics during the active cycle were dominated by clonal reproduction. However, the presence of sexual structures in orchards, the likelihood that five repeated MLGs resulted from sexual reproduction, and high genotypic diversity observed in some populations suggest that sexual spores play some role in APM epidemics. IMPORTANCE Understanding the population biology and epidemiology of plant pathogens is essential to develop effective strategies for controlling plant diseases. Herein, we gathered insights into the population biology of P. leucotricha populations from conventional and organic apple orchards in the United States. We showed genetic heterogeneity between P. leucotricha populations in Washington, and structure between populations from different U.S. regions, suggesting that short-distance spore dispersal plays an important role in the disease’s epidemiology. We presented evidence that P. leucotricha is heterothallic, and that populations likely result from a mixed (i.e., sexual and asexual) reproductive system, revealing that the sexual stage contributes to apple powdery mildew epidemics. We showed that the major resistance gene Pl-1 is valuable for apple breeding because virulent isolates have most likely not emerged yet in U.S. commercial orchards. These results will be important to achieve sustainability of disease management strategies and maintenance of plant health in apple orchards.

scholarly journals Apple powdery mildew caused by Podosphaera leucotricha: some aspects of disease management

2014 ◽  
Vol 20 (1-2) ◽  
Author(s):  
I. J. Holb
Keyword(s):  
Biological Control ◽  
Disease Management ◽  
Powdery Mildew ◽  
Chemical Control ◽  
Apple Cultivar ◽  
Apple Orchards ◽  
Cultivar Resistance ◽  
Podosphaera Leucotricha ◽  
Control Options ◽  
Apple Cultivars

Apple powdery mildew (Podoshphaera leucorticha) occurs wherever apples are grown. One of the most important fungal disease of apple which causing severe econimic loss on susceptible apple cultivars. This review focuses on the control of apple powdery mildew. The first part of the study provides details of novel aspects of non-chemical control approaches, including agronomic measures, mechanical and biological control options as well as essential features of apple cultivar resistance. After this, developments in chemical control options are described sperately for integrated and organic apple orchards.

No Evidence of Resistance to Trifloxystrobin, Triflumizole, and Boscalid in Podosphaera leucotricha Isolates from U.S. Commercial Apple Orchards

Plant Disease ◽  
2021 ◽  
Author(s):  
Lederson Gañán-Betancur ◽  
Tobin Peever ◽  
Achour Amiri
Keyword(s):  
New York ◽  
Pacific Northwest ◽  
Apple Orchards ◽  
Protein Subunit ◽  
Podosphaera Leucotricha ◽  
Group I ◽  
Detached Leaves ◽  
In Vivo Testing ◽  
Positive Correlations

Apple powdery mildew, caused by Podosphaera leucotricha, continues to be a challenge in commercial apple orchards in the U.S. Pacific Northwest and worldwide. In this study, P. leucotricha isolates were collected in 2018 and 2019 from two organic (baseline) and eight conventional (exposed) apple orchards in Washington, New York, and Virginia, and assessed for their sensitivity to trifloxystrobin (TRI, n= 232), triflumizole (TFZ, n = 217), and boscalid (BOS, n = 240) using a detached leaf assay. Effective concentrations inhibiting 50% growth (EC50) were not significantly different between baseline and exposed isolates, and ranged from 0.001 to 0.105, 0.09 to 6.31, and 0.05 to 2.18 µg/ml, for TRI, TFZ, and BOS, respectively. Reduction in sensitivity by factors of 105, 63 and 22 to TRI, TFZ, and BOS, respectively, were observed in some isolates, but all isolates were controlled by the commercial label rates of the three fungicides on detached leaves. Sequencing of the cytochrome b (cytb), cytochrome P450 sterol 14α-demethylase (CYP51), and the iron-sulfur protein subunit (SdhB) genes in isolates with high EC50 revealed no mutation previously reported to confer resistance to these fungicides in other fungi, and presence of a group I intron after codon 143 in the cytb gene. Significant (P < 0.001) moderate positive correlations (r = 0.38) observed between sensitivity to TRI and TFZ warrant continuous rotations of fungicides with different modes of actions in conventional orchards. The established baseline sensitivities and the molecular markers will help in selecting discriminatory doses and by-passing the challenging in vivo testing for future sensitivity monitoring in P. leucotricha.

scholarly journals Homologous Streptomycin Resistance Gene Present among Diverse Gram-Negative Bacteria in New York State Apple Orchards

1991 ◽  
Vol 57 (2) ◽  
pp. 486-491 ◽  
Author(s):  
John L. Norelli ◽  
Thomas J. Burr ◽  
Adriana M. Lo Cicero ◽  
Mathew T. Gilbert ◽  
Barbara H. Katz
Keyword(s):  
New York ◽  
Resistance Gene ◽  
New York State ◽  
Streptomycin Resistance ◽  
Gram Negative Bacteria ◽  
Apple Orchards ◽  
Gram Negative ◽  
York State

Optimizing Use of DMI Fungicides for Management of Apple Powdery Mildew Caused by Podosphaera leucotricha in New York State

Plant Disease ◽  
2021 ◽  
Author(s):  
David Strickland ◽  
Sara M. Villani ◽  
Kerik Cox
Keyword(s):  
New York ◽  
Powdery Mildew ◽  
Disease Control ◽  
Disease Incidence ◽  
New York State ◽  
Optimal Timing ◽  
Fresh Market ◽  
Podosphaera Leucotricha ◽  
York State ◽  
Dmi Fungicides

Powdery mildew, caused by the ascomycete Podosphaera leucotricha, is an endemic disease found wherever apples are grown that negatively impacts both tree vigor and fresh market yield. In the absence of durable host resistance, chemical management is the primary means of disease control. Demethylation inhibitor (DMI) fungicides are widely used to manage apple powdery mildew, but members within this fungicide class have been observed to differ in efficacy with respect to disease control. Moreover, debate exists as to the optimal timing of DMI fungicide applications for management of apple powdery mildew. In this regard, the goal of this study was to determine the best-use practices for DMI fungicides to manage apple powdery mildew in New York State. Multi-year trials were conducted to evaluate the potential differential efficacy performance of four common DMI fungicides, as well as additional trials to assess optimal application timing. In all years, we observed that treatments of flutriafol and myclobutanil consistently had the lowest incidences of powdery mildew compared to difenoconazole and fenbuconazole. In the 2018 and 2021 trials, the newly registered mefentrifluconazole was more comparable to the difenoconazole program with respect to powdery mildew disease incidence. We hypothesize that differences in DMI efficacy may be due to each fungicides’ water solubility and lipophilicity characteristics, and thus their ability to move systemically in the host or more easily penetrate the surface of germinating conidia. Applications timed between petal fall and first cover resulted in the lowest incidence of powdery mildew on terminal leaves of apple shoots compared to applications timed prior to petal fall. These observations are contrary to previous studies conducted in regions with differing climates. We also found that the incidence of secondary powdery mildew observed two weeks after petal fall was influenced by applications of DMI fungicides during the previous season. For example, management programs consisting of applications of flutriafol or myclobutanil in the prior season tended to have lower incidence of apple powdery in the following spring, presumably owing to reductions in overwintering inoculum. Despite reports of DMI resistance in other apple pathosystems, the DMI fungicide class is still relevant for the successful management of apple powdery mildew in New York State.

scholarly journals A Genome Resource for the Apple Powdery Mildew Pathogen Podosphaera leucotricha

2020 ◽  
Vol 110 (11) ◽  
pp. 1756-1758
Author(s):  
Lederson Gañán ◽  
Richard Allen White ◽  
Maren L. Friesen ◽  
Tobin L. Peever ◽  
Achour Amiri
Keyword(s):  
Powdery Mildew ◽  
Population Biology ◽  
Molecular Mechanisms ◽  
Draft Genome ◽  
Single Copy ◽  
Sequencing Data ◽  
Pome Fruit ◽  
Podosphaera Leucotricha ◽  
A Genome ◽  
Powdery Mildew Pathogen

Powdery mildew, caused by Podosphaera leucotricha, is an economically important disease of apple and pear trees. A single monoconidial strain (PuE-3) of this biotrophic fungus was used to extract DNA for Illumina sequencing. Data were assembled to form a draft genome of 43.8 Mb consisting of 8,921 contigs, 9,372 predicted genes, and 96.1% of complete benchmarking universal single copy orthologs (BUSCOs). This is the first reported genome sequence of P. leucotricha that will enable studies of the population biology, epidemiology, and fungicide resistance of this pathogen. Furthermore, this resource will be fundamental to uncover the genetic and molecular mechanisms of the apple−powdery mildew interaction, and support future pome fruit breeding efforts.

scholarly journals Detection of Powdery Mildew Resistance Gene in Melon Cultivar Meloni Based on SCAR Markers

2020 ◽  
Vol 12 (1) ◽  
pp. 76-82
Author(s):  
Muhammad Alif Ishak ◽  
Budi Setiadi Daryono
Keyword(s):  
Powdery Mildew ◽  
Resistance Gene ◽  
Powdery Mildew Resistance ◽  
Fungal Infections ◽  
Plant Diseases ◽  
Scar Markers ◽  
Powdery Mildew Resistance Gene ◽  
Mildew Resistance ◽  
Sequence Characterized Amplified Region ◽  
Melon Seeds

Powdery mildew is one of the diseases caused by fungal infections that can reduce the production of melon fruit worldwide including in Indonesia. A powdery mildew-resistant cultivar of melon is needed to increase melon yield crops. This study aimed to detect resistance gene linked to powdery mildew using a sequence characterized amplified region (SCAR) markers. The melon cultivar Meloni was used in this study. SL-3, PI 371795, and Aramis cultivar were used to compare. Amplification of the marker was performed employing a pair of primers. The result showed that Meloni had a powdery mildew resistance gene by the presence of a DNA target band at 1058 base pair (bp). Based on this result, it could be concluded that Meloni was an excellent melon cultivar because of its ability to overcome the powdery mildew infections naturally. SCAR markers have been used for various purposes, especially to detect resistance genes to plant diseases. The present study had provided information for plant breeders about Meloni as the new melon cultivar that was genetically resistant against powdery mildew infections. Furthermore, Meloni could be proposed as an alternative to native Indonesian superior melon seeds.

scholarly journals Natural Occurrence of Phytophthora infestans Causing Late Blight on Woody Nightshade (Solanum dulcamara) in New York

Plant Disease ◽  
2010 ◽  
Vol 94 (8) ◽  
pp. 1063-1063 ◽  
Author(s):  
K. L. Deahl ◽  
F. Perez ◽  
C. J. Baker ◽  
R. W. Jones ◽  
L. Cooke ◽  
...  
Keyword(s):  
United States ◽  
New York ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Mating Type ◽  
The United States ◽  
Plant Diseases ◽  
Home Garden ◽  
Mitochondrial Haplotype ◽  
Solanum Dulcamara

Woody nightshade (Solanum dulcamara) is a common hedgerow herbaceous perennial in the United States, one of only three native Solanum spp. S. dulcamara is a known host of Phytophthora infestans (3), but infection is rarely reported. There is a U.S. record from Maryland (2); in 1947, Peterson (4) stated that this species had never been found blighted in its natural habitat, although in 1960 it was listed as a host of P. infestans in New York (1). The A2 mating type has not been reported on this host. On 2 July, 2009, leaf lesions similar to those of P. infestans on potato were found on wild S. dulcamara at Riverhead, NY. The plant was growing in a home garden within 10 m of potato and tomato plants infected with P. infestans. When two infected leaves of S. dulcamara were incubated for 24 h under high humidity, a pathogen growth developed around the lesion margins that was characterized by hyaline mycelium bearing lemon-shaped sporangia that released motile zoospores after chilling in water, which is consistent with P. infestans. The caducous and limoniform to ovoid sporangia were 39 to 50 μm (average 45 μm) × 26 to 28 μm (average 27 μm) with a length/breadth ratio of 1.66. No oospores were observed. Three isolates were obtained from this plant during July 2009. Growth on rye agar was indistinguishable from that of local tomato isolates of P. infestans. Detached leaflets of S. dulcamara and S. tuberosum, inoculated with the woody nightshade isolates and kept in a humid chamber, became infected and developed profuse sporulation within 5 days. The pathogen isolated was confirmed as P. infestans by morphological, biochemical, and molecular characteristics. Inoculations of attached leaves of potted S. dulcamara plants resulted in necrotic lesions with many sporangia; sporulation also developed on inoculated, attached, and detached tomato leaves. P. infestans was reisolated and identity confirmed as before. The three isolates were A2 mating type, metalaxyl-resistant, mitochondrial haplotype Ia. All were glucose-6-phosphate isomerase 100/122 and peptidase 100/100, as confirmed with single-spore isolates. RG57 fingerprint analysis confirmed that isolates from woody nightshade, tomato, and potato obtained from the same and nearby sites were identical. Although P. infestans in the United States belongs to the new population, which may infect a wider host range than the old US-1 clonal lineage, S. dulcamara infections have only been found when late blight is already widespread in neighboring fields and there is no evidence to suggest that woody nightshade acts as an overwintering host in the United States. References: (1) Anonymous. Index of Plant Diseases in the United States. Page 456 in: Agric. Handb. No. 165, 1960 (2) C. Cox. Phytopathology 38:575, 1948. (3) D. C. Erwin and O. K. Ribeiro. Page 190 in: Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (4) L. C. Peterson. Am. Potato J. 24:188, 1947.

Molecular Mapping of Powdery Mildew Resistance Gene MlWE18 in Wheat Originated from Wild Emmer (Triticum turgidum var. dicoccoides)

2009 ◽  
Vol 35 (10) ◽  
pp. 1791-1797 ◽  
Author(s):  
Jun HAN ◽  
Lian-Song ZHANG ◽  
Gen-Qiao LI ◽  
Hong-Tao ZHANG ◽  
Chao-Jie XIE ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Resistance Gene ◽  
Powdery Mildew Resistance ◽  
Molecular Mapping ◽  
Triticum Turgidum ◽  
Wild Emmer ◽  
Powdery Mildew Resistance Gene ◽  
Mildew Resistance
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