scholarly journals Characterization of Phytophthora spp. on Floriculture Crops in North Carolina

Plant Disease ◽  
2011 ◽  
Vol 95 (8) ◽  
pp. 1013-1020 ◽  
Author(s):  
H. A. Olson ◽  
D. M. Benson
Keyword(s):  
North Carolina ◽  
Growth Inhibition ◽  
Mating Type ◽  
Host Species ◽  
Effective Concentration ◽  
Phytophthora Nicotianae ◽  
Mating Types ◽  
Previous Survey ◽  
Phytophthora Spp

Isolates of Phytophthora in floriculture crops were collected from North Carolina commercial greenhouse facilities in 2007 and 2008, identified, and characterized for mating type and mefenoxam sensitivity. In all, 163 isolates from 13 host species at 11 locations were identified primarily as Phytophthora nicotianae (59%), P. drechsleri (23%), P. cryptogea (9%), and P. tropicalis (4%). Multiple Phytophthora spp. were found at five locations. DNA sequencing was more reliable for differentiating P. cryptogea and P. drechsleri. Only the A1 mating type of P. drechsleri was collected; however, both mating types of P. nicotianae, P. cryptogea, and P. tropicalis were found. Overall, 66% of Phytophthora isolates were resistant or intermediate in resistance to mefenoxam at 1 μg a.i./ml. Three groups of P. drechsleri isolates had effective concentration of mefenoxam providing 50% growth inhibition (EC50) estimates over 700 μg a.i./ml. EC50 estimates for P. nicotianae ranged from 246 to 435 μg a.i./ml. Isolates of P. nicotianae exhibited phenotypic heterogeneity at several locations, suggesting multiple separate introductions to the facilities. In contrast, P. nicotianae and P. drechsleri isolates from two locations were phenotypically identical to a previous survey, suggesting that the facilities have Phytophthora spp. established onsite.

scholarly journals Characterization of the Black Shank Pathogen, Phytophthora nicotianae, Across North Carolina Tobacco Production Areas

Plant Disease ◽  
2018 ◽  
Vol 102 (6) ◽  
pp. 1108-1114 ◽  
Author(s):  
Courtney A. Gallup ◽  
Kestrel L. McCorkle ◽  
Kelly L. Ivors ◽  
David Shew
Keyword(s):  
North Carolina ◽  
Natural Populations ◽  
Hyphal Growth ◽  
The United States ◽  
The State ◽  
Phytophthora Nicotianae ◽  
Mating Types ◽  
Black Shank ◽  
Nuclear Regions

Black shank disease of tobacco, caused by the oomycete Phytophthora nicotianae, is a major threat to production in the United States and tobacco-producing areas worldwide. In a statewide survey of North Carolina, the rapid shift from race 0 to race 1 was documented. Collected pathogen isolates were characterized phenotypically for mating type and mefenoxam sensitivity, and genotypically by comparing sequences from three cytoplasmic and two nuclear regions. Both the A1 and A2 mating types were found throughout the state. When both mating types were recovered from the same field, pairings of isolates yielded viable oospores, indicating for the first time the potential for sexual sporulation by P. nicotianae in natural populations. Because the loss of complete resistance required a renewed use of the fungicide mefenoxam, a subset of the survey isolates was screened for sensitivity to the fungicide. All isolates were sensitive, with a mean effective concentration to inhibit 50% of hyphal growth of 0.4 μg/ml that was similar across mating types and races. Molecular characterization of 226 isolates revealed that the pathogen exists as multiple clonal types within the state. Genetic diversity among the pathogen population and the potential for sexual recombination may help explain the ability of the pathogen to rapidly adapt to host resistance genes.

scholarly journals Characterization of Phytophthora spp. Isolated from Ornamental Plants in Florida

Plant Disease ◽  
2016 ◽  
Vol 100 (2) ◽  
pp. 500-509 ◽  
Author(s):  
Jaimin S. Patel ◽  
Anne Vitoreli ◽  
Aaron J. Palmateer ◽  
Ashraf El-Sayed ◽  
David J. Norman ◽  
...  
Keyword(s):  
Mating Type ◽  
Phylogenetic Analyses ◽  
Management Strategies ◽  
Ornamental Plants ◽  
Phytophthora Nicotianae ◽  
Cross Resistance ◽  
Phytophthora Spp ◽  
Molecular Phylogenetic ◽  
Ornamental Crops

This report investigates population structure and genetic variability of Phytophthora spp. isolated from botanically diverse plants in Florida. Internal transcribed spacer-based molecular phylogenetic analyses indicate that Phytophthora isolates recovered from ornamental plants in Florida represent a genetically diverse population and that a majority of the isolates belong to Phytophthora nicotianae (73.2%), P. palmivora (18.7%), P. tropicalis (4.9%), P. katsurae (2.4%), and P. cinnamomi (0.8%). Mating type analyses revealed that most isolates were heterothallic, consisting of both mating type A1 (25.2%) and mating type A2 (39.0%), and suggesting that they could outcross. Fungicide sensitivity assays determined that several isolates were moderate to completely insensitive to mefenoxam. In addition, several isolates were also moderately insensitive to additional fungicides with different modes of action. However, correlation analyses did not reveal occurrence of fungicide cross-resistance. These studies suggest that a genetically diverse Phytophthora population infects ornamental crops and the occurrence of mefenoxam-insensitive Phytophthora populations raises concerns about disease management in ornamentals. Mitigating fungicide resistance will require prudent management strategies, including tank mixes and rotation of chemicals with different modes of actions.

scholarly journals Characterization of Isolates of Phytophthora infestans from Southern and Southeastern Brazil from 1998 to 2000

Plant Disease ◽  
2003 ◽  
Vol 87 (8) ◽  
pp. 896-900 ◽  
Author(s):  
Ailton Reis ◽  
Christine D. Smart ◽  
William E. Fry ◽  
Luiz A. Maffia ◽  
Eduardo S. G. Mizubuti
Keyword(s):  
Restriction Fragment Length Polymorphism ◽  
Phytophthora Infestans ◽  
Mating Type ◽  
Fragment Length Polymorphism ◽  
Southeastern Brazil ◽  
Mating Types ◽  
Clonal Lineage ◽  
Metalaxyl Resistance ◽  
Restriction Fragment Length

The population of Phytophthora infestans in Brazil was first characterized 12 years ago. In this research, isolates of P. infestans from potato (n = 184) and tomato (n = 267) collected in southern and southeastern Brazil were characterized to provide more detailed analysis of the current structure of the population. All 451 isolates were analyzed for mating type, and subsets of the isolates were analyzed for allozymes, restriction fragment length polymorphism fingerprint, mtDNA haplotypes, and metalaxyl resistance. Tomato isolates were all of A1 mating type, mtDNA Ib, and US-1 genotype or some variant within this clonal lineage. Of the potato isolates, 82% were A2 mating type, mtDNA IIa, BR-1 genotype, which is a new lineage of P. infestans. All A2 isolates were found on potato, whereas 91% of the A1 isolates were from tomato. A1 and A2 isolates were never found in the same field. The frequency of resistance to metalaxyl was higher in isolates from tomato (55%) than in isolates from potato (38%). After more than a decade of coexistence of isolates of the A1 and A2 mating types, the population was highly clonal, dominated by the BR-1 and US-1 clonal lineages.

scholarly journals Resistance to Mefenoxam and Metalaxyl Among Field Isolates of Phytophthora capsici Causing Phytophthora Blight of Bell Pepper

Plant Disease ◽  
2001 ◽  
Vol 85 (10) ◽  
pp. 1069-1075 ◽  
Author(s):  
Gregory Parra ◽  
Jean Beagle Ristaino
Keyword(s):  
North Carolina ◽  
Phytophthora Capsici ◽  
Effective Concentration ◽  
Bell Pepper ◽  
Mating Types ◽  
Phytophthora Blight ◽  
Field Isolates ◽  
The Mean ◽  
First Time ◽  
Important Disease

Incidence of Phytophthora blight in bell pepper fields that were sprayed for the first time with Ridomil Gold (mefenoxam) according to labeled recommendations was higher in North Carolina in 1997 than in previous years. Mefenoxam is the more active enantiomer contained in the racemic fungicide metalaxyl. A total of 150 isolates were obtained from 17 fields at eight grower locations. Among isolates from all locations, 30% were classified as sensitive, 10% as intermediate, and 59% were resistant to mefenoxam. Mefenoxam-resistant isolates were found in 82% of the fields sampled (14 of 17 fields). The proportion of resistant isolates in individual (fields ranged from 28 to 100%. The mean effective concentration (EC50) values for mefenoxam-sensitive isolates was 0.568 μg ml-1 (ranging from 0.12 to 1.1 μg ml-1), whereas the mean EC50 value for mefenoxam-resistant isolates was 366.5 μg ml-1 (ranging from 3 to 863 μg ml-1). The mean EC50 value for metalaxyl-sensitive isolates was 0.27 μg ml-1 (ranging from 0.00002 to 1.3 μg ml-1) and for metalaxyl-resistant isolates was 470.34 μg ml-1 (ranging from 10 to 966 μg ml-1). The greatest proportion of resistant isolates came from fields where mefenoxam was used alone rather than in combination with other fungicides. Both mating types were found among resistant isolates, suggesting that these isolates may persist in soil in subsequent years. Field isolates of Phytophthora capsici resistant to mefenoxam on pepper have not been reported previously and now pose new challenges for management of this important disease.

scholarly journals Identification, Mefenoxam Sensitivity, and Compatibility Type of Phytophthora spp. Attacking Floriculture Crops in North Carolina

Plant Disease ◽  
2005 ◽  
Vol 89 (2) ◽  
pp. 185-190 ◽  
Author(s):  
J. Hwang ◽  
D. M. Benson
Keyword(s):  
North Carolina ◽  
Species Identification ◽  
Plant Species ◽  
Mating Type ◽  
Single Source ◽  
Phytophthora Cryptogea ◽  
African Violet ◽  
Phytophthora Spp ◽  
Sensitivity Tests ◽  
Symptomatic Plant

Phytophthora isolates were collected from floriculture crops grown in commercial greenhouses in North Carolina for species identification, compatibility type determination, and mefenoxam sensitivity tests. Isolation from 41 symptomatic plant species at 29 production locations resulted in 483 isolates from eight crops at seven locations. Phytophthora cryptogea (184 isolates) was recovered from dusty miller and gerbera daisy. All isolates of P. cryptogea were insensitive or intermediate in sensitivity to mefenoxam at 1 μg a.i./ml and were A1 compatibility type. P. nicotianae (273 isolates) was isolated from African violet, lavender, pansy, petunia, and vinca. Of these isolates, 21% were insensitive to mefenoxam at either 1 or 100 μg a.i./ml. Isolates of P. nicotianae from five locations were A2 compatibility type, whereas isolates on pansy at one location were A1 compatibility type. English ivy grown at two locations was infected with P. palmivora. All 26 isolates of P. palmivora were sensitive to mefenoxam and were A1 compatibility type. Mating type and mefenoxam sensitivity were uniform among isolates of P. nicotianae and P. palmivora from a given crop at a given location, suggesting that epidemics within a location may have originated from a single source of inoculum.

scholarly journals MUTATIONS AFFECTING SEXUAL CONJUGATION AND RELATED PROCESSES IN SACCHAROMYCES CEREVISIAE. I. ISOLATION AND PHENOTYPIC CHARACTERIZATION OF NONMATING MUTANTS

Genetics ◽  
1974 ◽  
Vol 76 (2) ◽  
pp. 255-271
Author(s):  
Vivian Mackay ◽  
Thomas R Manney
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Low Frequency ◽  
Phenotypic Characterization ◽  
Mating Types ◽  
Sex Factors ◽  
Low Frequencies ◽  
Conjugation Process

ABSTRACT Nonmating mutants were also isolated from haploid strains of yeast of both mating types. The mutants were characterized with respect to their ability to produce and respond to specific yeast sex factors, their ability to mate at low frequencies, and the ability of the low-frequency diploids to sporulate. Loss of the ability to mate by either mating type was invariably accompanied by the loss of one or more, and in some cases, all, of the above capabilities. The results strongly indicate that the sex factors are functionally involved in the conjugation process.

scholarly journals Mating types of Phytophthora colocasiae on the island of Upolu, Samoa

2018 ◽  
Vol 71 ◽  
pp. 289-292 ◽  
Author(s):  
Kieran D. Mellow ◽  
Joy L. Tyson ◽  
Robert A. Fullerton ◽  
Angelika Tugaga ◽  
Fa'alelei Tunupopo ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Mating Type ◽  
Genetic Recombination ◽  
Leaf Blight ◽  
Phytophthora Nicotianae ◽  
Mating Types ◽  
Comprehensive Understanding ◽  
Phytophthora Colocasiae ◽  
Oospore Formation ◽  
Taro Leaf Blight

Taro leaf blight (TLB) caused by Phytophthora colocasiae is a damaging disease that destroyed Samoa’s taro industry following its introduction in 1993. The aim of this study was to determine the occurrence of the A1 and A2 mating types of P. colocasiae for a more comprehensive understanding of the risk the pathogen poses for the future of the taro industry in Samoa. In September 2015, 54 isolates of P. colocasiae were collected from taro leaf blight lesions from 13 farms around the island of Upolu, Samoa. The mating types of each isolate was determined by observation of oospore formation when paired with tester isolates of Phytophthora nicotianae of known mating types (A1 or A2). Fifty isolates were found to be A2 mating type and four did not form oospores with either mating type. No A1 or self-fertile isolates were found. These results suggest that the A1 mating type has not been introduced to the island of Upolu, preventing the formation of oospores between compatible mating types of P. colocasiae and lessening the risk of new and potentially more threatening genotypes of the pathogen from emerging through genetic recombination. Keywords taro leaf blight, Colocasia esculenta, taro, sexual reproduction

scholarly journals Differential Gene Expression between Fungal Mating Types Is Associated with Sequence Degeneration

2020 ◽  
Vol 12 (4) ◽  
pp. 243-258 ◽  
Author(s):  
Wen-Juan Ma ◽  
Fantin Carpentier ◽  
Tatiana Giraud ◽  
Michael E Hood
Keyword(s):  
Differential Expression ◽  
Differentially Expressed Genes ◽  
Mating Type ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Gc Content ◽  
Differentially Expressed ◽  
Mating Types ◽  
Sexual Antagonism ◽  
Recombination Suppression

Abstract Degenerative mutations in non-recombining regions, such as in sex chromosomes, may lead to differential expression between alleles if mutations occur stochastically in one or the other allele. Reduced allelic expression due to degeneration has indeed been suggested to occur in various sex-chromosome systems. However, whether an association occurs between specific signatures of degeneration and differential expression between alleles has not been extensively tested, and sexual antagonism can also cause differential expression on sex chromosomes. The anther-smut fungus Microbotryum lychnidis-dioicae is ideal for testing associations between specific degenerative signatures and differential expression because 1) there are multiple evolutionary strata on the mating-type chromosomes, reflecting successive recombination suppression linked to mating-type loci; 2) separate haploid cultures of opposite mating types help identify differential expression between alleles; and 3) there is no sexual antagonism as a confounding factor accounting for differential expression. We found that differentially expressed genes were enriched in the four oldest evolutionary strata compared with other genomic compartments, and that, within compartments, several signatures of sequence degeneration were greater for differentially expressed than non-differentially expressed genes. Two particular degenerative signatures were significantly associated with lower expression levels within differentially expressed allele pairs: upstream insertion of transposable elements and mutations truncating the protein length. Other degenerative mutations associated with differential expression included nonsynonymous substitutions and altered intron or GC content. The association between differential expression and allele degeneration is relevant for a broad range of taxa where mating compatibility or sex is determined by genes located in large regions where recombination is suppressed.

scholarly journals Protection of Citrus Rootstocks Against Phytophthora spp. with a Hypovirulent Isolate of Phytophthora nicotianae

2007 ◽  
Vol 97 (8) ◽  
pp. 958-963 ◽  
Author(s):  
G. C. Colburn ◽  
J. H. Graham
Keyword(s):  
Poncirus Trifoliata ◽  
Phytophthora Nicotianae ◽  
Root Weight ◽  
Post Inoculation ◽  
Phytophthora Root Rot ◽  
Phytophthora Spp ◽  
Naturally Occurring ◽  
Fibrous Roots ◽  
Cleopatra Mandarin ◽  
Swingle Citrumelo

Phytophthora root rot of citrus in Florida is caused by Phytophthora nicotianae and P. palmivora. A naturally occurring isolate of P. nicotianae (Pn117) was characterized as hypovirulent on citrus roots. Pn117 infected and colonized fibrous roots, but caused significantly less disease than the virulent isolates P. nicotianae Pn198 and P. palmivora Pp99. Coincident inoculation of rootstock seedlings of Cleopatra mandarin (Citrus reticulata) or Swingle citrumelo (C. paradisi × Poncirus trifoliata) with the hypovirulent Pn117 and the virulent isolates Pn198 and Pp99 did not reduce the severity of disease caused by the virulent Phytophthora spp. When either rootstock was inoculated with the hypovirulent Pn117 for 3 days prior to inoculation with virulent isolates, preinoculated seedlings had significantly less disease and greater root weight compared with seedlings inoculated with the virulent isolates alone. Recovery of the different colony types of Phytophthora spp. from roots of sweet orange (C. sinensis) or Swingle citrumelo was evaluated on semiselective medium after sequential inoculations with the hypovirulent Pn117 and virulent Pp99. Pn117 was isolated from roots at the same level as the Pp99 at 3 days post inoculation. Preinoculation of Pn117 for 3 days followed by inoculation with Pp99 resulted in greater recovery of the hypovirulent isolate and lower recovery of the virulent compared with coincident inoculation.

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