scholarly journals Phytophthora Species Associated with Crown and Root Rot of Apple in Chile

Plant Disease ◽  
2001 ◽  
Vol 85 (6) ◽  
pp. 603-606 ◽  
Author(s):  
B. A. Latorre ◽  
M. E. Rioja ◽  
W. F. Wilcox
Keyword(s):  
Central Valley ◽  
Phytophthora Species ◽  
Crown Rot ◽  
Apple Rootstocks ◽  
Apple Trees ◽  
Potting Medium ◽  
Root And Crown Rot ◽  
Genotype Interaction ◽  
Crown And Root Rot ◽  
Isolated Species

Phytophthora cactorum, P. cryptogea, P. gonapodyides, and P. megasperma were isolated from necrotic root and crown tissues or the rhizospheres of apple trees exhibiting typical symptoms of Phytophthora root and crown rot in the Central Valley of Chile. Representative isolates of all four species were pathogenic on a variety of apple rootstocks and scions in trials conducted on excised shoots and 1-year-old MM.106 rootstock grown for 4 months in infested potting medium. P. cactorum was the most frequently isolated species and the most virulent in pot tests, although a significant Phytophthora sp.-apple genotype interaction was observed. This is the first report of any species other than P. cactorum causing root and crown rot of apple trees in Chile.

scholarly journals Resistance to Phytophthora Species among Rootstocks for Cultivated Prunus Species

HortScience ◽  
2017 ◽  
Vol 52 (11) ◽  
pp. 1471-1476 ◽  
Author(s):  
Gregory T. Browne
Keyword(s):  
Root Rot ◽  
Phytophthora Species ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Prunus Species ◽  
Phytophthora Megasperma ◽  
Soil Flooding ◽  
Root And Crown Rot ◽  
Crown And Root Rot ◽  
Multiple Species

Many species of Phytophthora de Bary are important pathogens of cultivated Prunus L. species worldwide, often invading the trees via their rootstocks. In a series of greenhouse trials, resistance to Phytophthora was tested in new and standard rootstocks for cultivated stone fruits, including almond. Successive sets of the rootstocks, propagated as hardwood cuttings or via micropropagation, were transplanted into either noninfested potting soil or potting soil infested with Phytophthora cactorum (Lebert & Cohn) J. Schöt., Phytophthora citricola Sawada, Phytophthora megasperma Drechs, or Phytophthora niederhauserii Z.G. Abad & J.A. Abad. Soil flooding was included in all trials to facilitate pathogen infection. In some trials, soil flooding treatments were varied to examine their effects on the rootstocks in both the absence and presence of Phytophthora. Two to 3 months after transplanting, resistance to the pathogens was assessed based on the severity of root and crown rot. ‘Hansen 536’ was consistently more susceptible than ‘Lovell’, ‘Nemaguard’, ‘Atlas’, ‘Viking’, ‘Citation’, and ‘Marianna 2624’ to root and/or crown rot caused by P. cactorum, P. citricola, and P. megasperma. By contrast, susceptibility to P. niederhauserii was similarly high among all eight tested genotypes of peach, four genotypes of peach × almond, two genotypes of (almond × peach) × peach, and one genotype of plum × almond. Most plum hybrids were highly and consistently resistant to crown rot caused by P. niederhauserii, but only ‘Marianna 2624’ was highly resistant to both crown and root rot caused by all of the Phytophthora species. The results indicate that there is a broad tendency for susceptibility of peach × almond rootstocks and a broad tendency for resistance of plum hybrid rootstocks to multiple species of Phytophthora.

scholarly journals Incidence and Severity of Crown and Root Rots on Four Apple Rootstocks Following Exposure to Phytophthora Species and Waterlogging

1993 ◽  
Vol 118 (1) ◽  
pp. 63-67 ◽  
Author(s):  
W.F. Wilcox
Keyword(s):  
Root Rot ◽  
Shoot Growth ◽  
Disease Susceptibility ◽  
Disease Incidence ◽  
Phytophthora Species ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Apple Rootstocks ◽  
Root Rots ◽  
Potting Medium

Plants of four apple (Malus ×domestica Borkh.) rootstock clones, M.7, M.26, MM.111, and Ottawa (O.) 3, were grown in unamended potting medium or in the same medium infested with Phytophthora cactorum (Leb. & Cohn) Schroet., P. cambivora (Petri) Buisman, P. cryptogea Pethyb. & Laff., or P. megasperma Drechsler, causal agents of crown and root rots. Plants were flooded for either 0, 24, 48, or 72 h every 7 days for 4 months, then assessed for disease incidence and severity. Averaged across all pathogens and rootstocks, mean crown rot incidences were 2.5%, 6.3%, 19%, and 50% following weekly flooding periods of 0, 24, 48, and 72 h, respectively; when averaged across all rootstocks and flooding treatments, mean incidences of crown rot caused by P. cryptogea, P. cactorum, P. cambivora, and P. megasperma were 36%, 26%, 15%, and 8.8%, respectively; when averaged across all four pathogens, mean crown rot incidences after 72 h of flooding were 40%, 45%, 50%, and 75% for M.26, 0.3, M.7, and MM.111, respectively. In contrast, 72-h flooding periods in the absence of a pathogen were least detrimental to growth of MM.111 clones and most detrimental to shoot growth of M-26. Exceptions to general trends were reflected by statistical interactions among pathogens, rootstocks, and flooding durations, e.g., after 72-h floodings, 0.3 was the rootstock with the greatest amount of root rot caused by P. cryptogea but the least amount caused by P. megasperma. Differential disease susceptibility among rootstocks appeared greatest with respect to P. cactorum and least with respect to P. cryptogea.

scholarly journals PhytophthoraSpecies Are Common on Nursery Stock Grown for Restoration and Revegetation Purposes in California

Plant Disease ◽  
2019 ◽  
Vol 103 (3) ◽  
pp. 448-455 ◽  
Author(s):  
S. Rooney-Latham ◽  
C. L. Blomquist ◽  
K. L. Kosta ◽  
Y. Y. Gou ◽  
P. W. Woods
Keyword(s):  
North America ◽  
Phytophthora Species ◽  
Molecular Techniques ◽  
Crown Rot ◽  
Native Plant ◽  
Nursery Stock ◽  
Plant Nursery ◽  
Root And Crown Rot ◽  
Symptomatic Tissue ◽  
First Time

Phytophthora tentaculata was detected for the first time in North America in 2012 in a nursery on sticky monkeyflower plant (Diplacus aurantiacus) and again in 2014 on outplanted native plants. At that time, this species was listed as a federally actionable and reportable pathogen by the USDA. As a result of these detections, California native plant nurseries were surveyed to determine the prevalence of Phytophthora species on native plant nursery stock. A total of 402 samples were collected from 26 different native plant nurseries in California between 2014 and 2016. Sampling focused on plants with symptoms of root and crown rot. Symptomatic tissue was collected and tested by immunoassay, culture, and molecular techniques (PCR). Identifications were made using sequences from the internal transcribed spacer (ITS) rDNA region, a portion of the trnM-trnP-trnM, or the atp9-nad9 mitochondrial regions. Phytophthora was confirmed from 149 of the 402 samples (37%), and from plants in 22 different host families. P. tentaculata was the most frequently detected species in our survey, followed by P. cactorum and members of the P. cryptogea complex. Other species include P. cambivora, P. cinnamomi, P. citricola, P. hedraiandra, P. megasperma, P. multivora, P. nicotianae, P. niederhauserii, P. parvispora, P. pini, P. plurivora, and P. riparia. A few Phytophthora sequences generated from mitochondrial regions could not be assigned to a species. Although this survey was limited to a relatively small number of California native plant nurseries, Phytophthora species were detected from three quarters of them (77%). In addition to sticky monkeyflower, P. tentaculata was detected from seven other hosts, expanding the number of associated hosts. During this survey, P. parvispora was detected for the first time in North America from symptomatic crowns and roots of the nonnative Mexican orange blossom (Choisya ternata). Pathogenicity of P. parvispora and P. nicotianae was confirmed on this host. These findings document the widespread occurrence of Phytophthora spp. in native plant nurseries and highlight the potential risks associated with outplanting infested nursery-grown stock into residential gardens and wildlands.

scholarly journals First Report of Phytophthora citrophthora on Penstemon barbatus in Italy

Plant Disease ◽  
2006 ◽  
Vol 90 (9) ◽  
pp. 1260-1260 ◽  
Author(s):  
A. Garibaldi ◽  
D. Bertetti ◽  
D. Minerdi ◽  
M. L. Gullino
Keyword(s):  
Its Region ◽  
The United States ◽  
Phytophthora Species ◽  
Crown Rot ◽  
Pathogenicity Test ◽  
Phytophthora Citrophthora ◽  
First Report ◽  
Blastn Analysis ◽  
Root And Crown Rot ◽  
Pathogenicity Tests

Penstemon barbatus (Cav.) Roth (synonym Chelone barbata), used in parks and gardens and sometimes grown in pots, is a plant belonging to the Scrophulariaceae family. During the summers of 2004 and 2005, symptoms of a root rot were observed in some private gardens located in Biella Province (northern Italy). The first symptoms resulted in stunting, leaf discoloration followed by wilt, root and crown rot, and eventually, plant death. The diseased tissue was disinfested for 1 min in 1% NaOCl and plated on a semiselective medium for Oomycetes (4). The microorganism consistently isolated from infected tissues, grown on V8 agar at 22°C, produced hyphae with a diameter ranging from 4.7 to 5.2 μm. Sporangia were papillate, hyaline, measuring 43.3 to 54.4 × 26.7 to 27.7 μm (average 47.8 × 27.4 μm). The papilla measured from 8.8 to 10.9 μm. These characteristics were indicative of a Phytophthora species. The ITS region (internal transcribed spacer) of rDNA was amplified using primers ITS4/ITS6 (3) and sequenced. BLASTn analysis (1) of the 800 bp obtained showed a 100% homology with Phytophthora citrophthora (R. & E. Sm.) Leonian. The nucleotide sequence has been assigned GenBank Accession No. DQ384611. For pathogenicity tests, the inoculum of P. citrophthora was prepared by growing the pathogen on autoclaved wheat and hemp kernels (2:1) at 25°C for 20 days. Healthy plants of P. barbatus cv. Nano Rondo, 6 months old, were grown in 3-liter pots (one plant per pot) using a steam disinfested substrate (peat/pomix/pine bark/clay 5:2:2:1) in which 200 g of kernels per liter of substrate were mixed. Noninoculated plants served as control treatments. Three replicates were used. Plants were maintained at 15 to 20°C in a glasshouse. The first symptoms, similar to those observed in the gardens, developed 21 days after inoculation, and P. citrophthora was consistently reisolated from infected plants. Noninoculated plants remained healthy. The pathogenicity test was carried out twice with similar results. A nonspecified root and crown rot of Penstemon spp. has been reported in the United States. (2). To our knowledge, this is the first report of P. citrophthora on P. barbatus in Italy as well as in Europe. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997 (2) F. E. Brooks and D. M. Ferrin. Plant Dis. 79:212, 1995. (3) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (4) H. Masago et al. Phytopathology 67:425, 1977.

scholarly journals Characterization of Oomycete Species Associated With Root and Crown Rot of English Walnut in Chile

Plant Disease ◽  
2019 ◽  
Vol 103 (4) ◽  
pp. 691-696 ◽  
Author(s):  
Jeannette Guajardo ◽  
Sebastián Saa ◽  
Natalia Riquelme ◽  
Gregory Browne ◽  
Cristian Youlton ◽  
...  
Keyword(s):  
Phytophthora Cinnamomi ◽  
Juglans Regia ◽  
Pythium Ultimum ◽  
Crown Rot ◽  
Root Rots ◽  
Root And Crown Rot ◽  
Pathogenicity Tests ◽  
English Walnut ◽  
Crown And Root Rot ◽  
Root Tissues

English (Persian) walnut (Juglans regia) trees affected by root and crown rot were surveyed in five regions of central Chile between 2015 and 2017. In each region, nine orchards, ranging from 1 to 21 years old, were randomly selected and inspected for incidence and severity of tree decline associated with crown and root rot. Soil and symptomatic crown and root tissues were collected and cultured in P5ARP semiselective medium to isolate potential oomycete pathogens, which were identified through morphology and molecularly using ITS sequences in the rDNA gene and beta tubulin gene. The most frequently isolated species was Phytophthora cinnamomi. Pathogenicity tests were conducted with representative oomycete isolates. P. cinnamomi, P. citrophthora, and Pythium ultimum were all pathogenic in J. regia. Nevertheless, only P. cinnamomi and P. citrophthora were pathogenic to English walnut. Py. ultimum caused limited levels of root damage to English walnut seedlings. Our research indicates that as the Chilean walnut industry has expanded, so have walnut crown and root rots induced by oomycetes.

scholarly journals Phytophthora Root and Collar Rot of Paulownia, a New Disease for Europe

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1664
Author(s):  
Francesco Aloi ◽  
Mario Riolo ◽  
Federico La Spada ◽  
Gaetano Bentivenga ◽  
Salvatore Moricca ◽  
...  
Keyword(s):  
Irrigation Management ◽  
Morphological Characteristics ◽  
Stem Bark ◽  
Phytophthora Species ◽  
Crown Rot ◽  
Infested Soil ◽  
Soil P ◽  
Rdna Its ◽  
Rdna Its Sequences ◽  
Root And Crown Rot

Paulownia species are fast growing trees native to China, which are being grown in managed plantings in several European countries for the production of wood and biomasses. In 2018, wilting, stunting, leaf yellowing, and collapse, as a consequence of root and crown rot, were observed in around 40% of trees of a 2-year-old planting of Paulownia elongata × P. fortunei in Calabria (Southern Italy). Two species of Phytophthora were consistently recovered from roots, basal stem bark, and rhizosphere soil of symptomatic trees and were identified as Ph. nicotianae and Ph. palmivora on the basis of both morphological characteristics and phylogenetic analysis of rDNA ITS sequences. Koch’s postulates were fulfilled by reproducing the symptoms on potted paulownia saplings transplanted into infested soil or stem-inoculated by wounding. Both Phytophthora species were pathogenic and caused root rot and stem cankers. Even though P. palmivora was the only species recovered from roots of naturally infected plants, in pathogenicity tests through infested soil P. nicotianae was more virulent. This is the first report of Phytophthora root and crown rot of a Paulownia species in Europe. Strategies to prevent this emerging disease include the use of healthy nursery plants, choice of well-drained soils for new plantations, and proper irrigation management.

Efficacy of Fungicides and Biopesticides for Management of Phytophthora Crown and Root Rot of Gerber Dais

2011 ◽  
Vol 12 (1) ◽  
pp. 13 ◽  
Author(s):  
D. M. Benson ◽  
K. C. Parker
Keyword(s):  
Root Rot ◽  
Fungicide Resistance ◽  
Pathogen Resistance ◽  
Crown Rot ◽  
Disease Development ◽  
Greenhouse Production ◽  
Run Off ◽  
Action Committee ◽  
Root And Crown Rot ◽  
Crown And Root Rot

Several fungicides and biopesticides were evaluated for control of Phytophthora crown and root rot of Gerber daisy caused by P. cryptogea, a frequently encountered pathogen in greenhouse production. In greenhouse trials, biopesticides were applied 3 to 5 days before inoculation with P. cryptogea, while fungicides were applied at the time of inoculation. Efficacy of the treatments was assessed according to fresh plant top weights and root rot ratings at the end of experiments. Phosphite salt fungicides such as AgriFos, Aliette, Alude, Magellan and Vital sprayed to run off prior to inoculation were ineffective. Similarly, the strobulurins (Disarm, Heritage, and Insignia) as a drench and the biopesticides (Muscodor albus, Remedier, and Taegro) incorporated or as a drench failed to prevent root and crown rot and collapse of plants. Adorn as a drench at 2 fl oz/100 gal prevented Phytophthora crown and root rot in two of three trial years. Fenstop as a drench at 14 fl oz/100 gal or Orvego as a drench at rates of 22.5 to 34 fl oz/100 gal consistently controlled disease in three years of trials. Segway as a drench at 6 fl oz/100 gal varied in efficacy but in all trials, disease development was less than the non-treated, inoculated control. Because the effective fungicides are in different Fungicide Resistance Action Committee codes, growers have valuable rotation options for managing crown and root rot caused by P. cryptogea on Gerber daisy and avoiding pathogen resistance in the Phytophthora populations. Accepted for publication 18 February 2011. Published 12 May 2011.

Identification, Chemical and Biological Management of Phytopythium vexans, the Causal Agent of Phytopythium Root and Crown Rot of Woody Ornamentals

Plant Disease ◽  
2020 ◽  
Author(s):  
Milan Panth ◽  
Fulya Baysal-Gurel ◽  
Farhat A. Avin ◽  
Terri Simmons
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Root Rot ◽  
Field Trials ◽  
Causal Agent ◽  
Crown Rot ◽  
Red Maple ◽  
Woody Ornamentals ◽  
Root And Crown Rot ◽  
Crown And Root Rot

Soilborne diseases caused by pathogens such as Phytophthora, Rhizoctonia, Fusarium, Verticillium, and Pythium species are the most important diseases of woody ornamentals. Ginkgo (Ginkgo biloba) and red maple (Acer rubrum) ‘October Glory’ plants grown in containers and fields in Tennessee have shown root and crown rot symptoms with dark brown to black lesions in 2017 and 2018. The objective of this research was to isolate and identify pathogens affecting ginkgo and red maple plants in nurseries of Tennessee and develop fungicide/biofungicide management recommendations for nursery producers. Isolations were made from the infected roots. Several Phytophthora-like colonies with spherical zoospores, filamentous to globose oogoni, and whitish mycelium, were isolated on V8-PARPH medium. For confirming identity, total genomic DNA was extracted followed by the sequence analysis of the internal transcribed spacer (ITS) regions, and large subunit (LSU) of the nuclear ribosomal RNA (rRNA) as well as cytochrome c oxidase subunit I (Cox I) and cytochrome c oxidase subunit II (Cox II) of mitochondrial DNA (mtDNA). Based on morphological and molecular analysis, Phytopythium vexans was described as a causal agent of crown and root rot from the infected ginkgo and red maple plants. To complete Koch’s postulates, a pathogenicity test was performed by drenching 100 ml V8 agar medium slurry of P. vexans inoculum on 1-year-old potted ginkgo plant root systems as well as red maple ‘October Glory’. Necrotic lesion development was observed in the root system 45 days after inoculation and P. vexans was re-isolated from the roots of both ginkgo and red maple. All control ginkgo and red maple plants remained disease-free and no pathogen was re-isolated. In addition, the efficacy of fungicides, biofungicides, fertilizer and host-plant defense inducers (traditionally recommended for management of oomycete diseases) for control of Phytopythium crown and root rot was evaluated on ginkgo and red maple ‘October Glory’ seedlings in greenhouse and field trials. The fungicides such as Empress Intrinsic, Pageant Intrinsic, Segovis and Subdue MAXX were effective in both greenhouse and field trials, and the biofungicide Stargus reduced the disease severity caused by pathogen P. vexans on ginkgo and red maple plants in greenhouse trials. These results will help nursery producers to make proper management decisions for newly reported Phytopythium crown and root rot disease of ginkgo and red maple plants.

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