Phytophthora crown rot of Florida Strawberry: Inoculum Sources and Thermotherapy of Transplants for Disease Management

Plant Disease ◽  
2021 ◽  
Author(s):  
Juliana Silveira Baggio ◽  
Marcus Vinicius Marin ◽  
Natalia A. Peres
Keyword(s):  
Heat Treatment ◽  
Chemical Control ◽  
Pathogen Resistance ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Inoculum Sources ◽  
Phytophthora Spp ◽  
Commercial Farms ◽  
Important Disease

Phytophthora crown rot, caused mainly by Phytophthora cactorum, and also by the recently reported P. nicotianae, is an important disease in the Florida strawberry annual production system. Mefenoxam is the most effective and widely used fungicide to manage this disease. However, due to pathogen resistance, alternatives to chemical control are needed. Phytophthora spp. were rarely recovered during the summer from soil of commercial farms where the disease was observed during the season. In a more detailed survey on research plots, neither of the two species was recovered one month after the crop was terminated and water was shut off. Therefore, Phytophthora spp. does not seem to survive in the soil over summer in Florida. In a field trial, asymptomatic nursery transplants harboring quiescent infections were confirmed as the major source of inoculum for these pathogens in Florida. Heat treatment of P. cactorum zoospores at 44oC for as little as 5 min was effective in inhibiting germination and colony formation; however, oospore germination was not inhibited by any of the tested temperatures in vitro. In the field, thermotherapy treatment of inoculated plants was shown to have great potential to serve as a non-chemical approach for managing Phytophthora crown rot in production fields and reducing mefenoxam-resistant populations in nursery transplants.

Improving the toolbox to manage Phytophthora diseases of strawberry: searching for chemical alternatives

2021 ◽  
Author(s):  
Marcus Vinicius Marin ◽  
Natalia Peres
Keyword(s):  
Fungicide Resistance ◽  
Chemical Control ◽  
Mycelial Growth ◽  
Crown Rot ◽  
Resistance Risk ◽  
In Vivo Assays ◽  
Modes Of Action ◽  
Phytophthora Spp

Florida strawberry production is affected by two economically important Phytophthora diseases, Phytophthora crown rot (PhCR) and leather rot (LR), caused primarily by P. cactorum and P. nicotianae. Although products are available, chemical control is limited to mefenoxam, phosphites, and azoxystrobin and resistance to mefenoxam and azoxystrobin has been reported. Both in vitro and in vivo assays were conducted to evaluate the effectiveness of eight different chemical classes on controlling PhCR and LR of strawberry. The fungicides mandipropamid, fluopicolide, oxathiapiprolin, and cymoxanil completely inhibited mycelial growth of both species at 1µg/ml. The same fungicides controlled LR and PhCR caused by P. cactorum, in detached fruit and greenhouse trials, respectively, including mefenoxam-resistant isolates. However, for PhCR caused by P. nicotianae only oxathiapiprolin and cymoxanil were effective in controlling the disease. Cyazofamid, fluazinam, propamocarb, and tebuconazole did not control PhCR caused by either Phytophthora spp. Except for tebuconazole, all fungicides tested reduced incidence of LR caused by P. cactorum in the detached fruit assay; in contrast, fluazinam, cyazofamid, and propamocarb had no effect on P. nicotianae. This study identifies four fungicides that could potentially be registered to manage both PhCR and LR of strawberry. The registration of additional fungicides with different modes of action would allow fruit and nursery growers to alternate products to reduce fungicide resistance risk.

scholarly journals Induced Resistance as a Possible Means to Control Diseases of Strawberry Caused by Phytophthora spp.

Plant Disease ◽  
2003 ◽  
Vol 87 (4) ◽  
pp. 345-350 ◽  
Author(s):  
H. Eikemo ◽  
A. Stensvand ◽  
A. M. Tronsmo
Keyword(s):  
Growth Rate ◽  
Disease Resistance ◽  
Crown Rot ◽  
Fragaria Vesca ◽  
Disease Score ◽  
Phytophthora Cactorum ◽  
Phytophthora Spp ◽  
Retarding Effect ◽  
Severity Of The Disease

Two putative elicitors of disease resistance (acibenzolar-S-methyl and chitosan) were tested for their effect on crown rot (Phytophthora cactorum) in strawberry. The effect of both compounds was enhanced when the time between treatment and inoculation was prolonged from 2 to 20 days. There were no significant differences between treatments when the concentration of acibenzolar-S-methyl was increased from 10 to 1,000 μg a.i./plant. The lowest tested concentrations of chitosan (10 and 50 μg a.i./plant) resulted in a lower disease score compared with the highest concentrations (250 or 1,000 μg a.i./plant). There were no differences in disease score between treatment with fosetyl-Al, acibenzolar-S-methyl, or chitosan when applied 5 or 15 days before inoculation. The effect of acibenzolar-S-methyl and chitosan also was tested against P. fragariae var. fragariae in alpine strawberry (Fragaria vesca var. alpina cv. Alexandria). Chitosan had no effect, whereas fosetyl-Al and all treatments with acibenzolar-S-methyl (50 or 250 μg a.i./plant; 5, 10, 20, or 40 days before inoculation) reduced the severity of the disease. There were no significant differences between acibenzolar-S-methyl and fosetyl-Al when applied at the same time. Acibenzolar-S-methyl and chitosan at concentrations of 0.5, 5, 50, and 500 μg a.i. ml-1 in V8 juice agar were tested for possible effects on P. cactorum and P. fragariae var. fragariae in vitro. Only chitosan at concentrations of 50 and 500 μg a.i. ml-1 had a growth-retarding effect on P. cactorum. Both acibenzolar-S-methyl and chitosan at a concentration of 500 μg a.i. ml-1 reduced the growth rate of P. fragariae var. fragariae.

scholarly journals Phytophthora Crown Rot of Strawberry

EDIS ◽  
2019 ◽  
Vol 2019 (5) ◽  
pp. 3
Author(s):  
Natalia A Peres ◽  
Juliana S. Baggio
Keyword(s):  
Plant Pathology ◽  
Chemical Control ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Pathology Department ◽  
Important Disease

This new 3-page article describes Phytophthora crown rot, an important disease in Florida strawberry fields caused mainly by Phytophthora cactorum, and provides some recommendations for cultural and chemical control. Written by Natalia A. Peres and Juliana S. Baggio and published by the UF/IFAS Plant Pathology Department. https://edis.ifas.ufl.edu/pp350

scholarly journals Survival of Botrytis cinerea as mycelium in rose crop debris and as sclerotia in soil

2005 ◽  
Vol 30 (5) ◽  
pp. 516-521 ◽  
Author(s):  
Alderi E Araújo ◽  
Luiz A Maffia ◽  
Eduardo S. G Mizubuti ◽  
Acelino C Alfenas ◽  
Guy de Capdeville ◽  
...  
Keyword(s):  
Weight Loss ◽  
Botrytis Cinerea ◽  
Rosa Hybrida ◽  
Inoculum Sources ◽  
Disease Epidemiology ◽  
Plant Parts ◽  
Polyethylene Bags ◽  
Stems And Leaves ◽  
Important Disease

Botrytis blight caused by Botrytis cinerea is an important disease of rose (Rosa hybrida) grown in greenhouses in Brazil. As little is known regarding the disease epidemiology under greenhouse conditions, pathogen survival in crop debris and as sclerotia was evaluated. Polyethylene bags with petals, leaves, or stem sections artificially infected with B. cinerea were mixed with crop debris in rose beds, in a commercial plastic greenhouse. High percentage of plant parts with sporulation was detected until 60 days, then sporulation decreased on petals after 120 days, and sharply decreased on stems or leaves after 90 days. Sporulation on petals continued for 360 days, but was not observed on stems after 150 days or leaves after 240 days. Although the fungus survived longer on petals, stems and leaves are also important inoculum sources because high amounts of both are deposited on beds during cultivation. Survival of sclerotia produced on PDA was also quantified. Sclerotia germination was greater than 75% in the initial 210 days and 50% until 360 days. Sclerotia weight gradually declined but they remained viable for 360 days. Sclerotia were produced on the buried petals, mainly after 90 days of burial, but not on leaves or stems. Germination of these sclerotia gradually decreased after 120 days, but lasted until 360 days. Higher weight loss and lower viability were observed on sclerotia produced on petals than on sclerotia produced in vitro

Detection and Characterization of QoI-Resistant Phytophthora cactorum and P. nicotianae Causing Leather Rot in Florida Strawberry

Plant Disease ◽  
2021 ◽  
Author(s):  
Marcus Vinicius Marin ◽  
Teresa E Seijo ◽  
Ellias Zuchelli ◽  
Natalia A. Peres
Keyword(s):  
Point Mutations ◽  
Crown Rot ◽  
Cytb Gene ◽  
Phytophthora Cactorum ◽  
Phytophthora Spp ◽  
Mitochondrial Cytochrome B ◽  
Qualitative Resistance ◽  
Selection Of ◽  
Qoi Resistance

Phytophthora cactorum and P. nicotianae cause leather rot (LR) of fruit and Phytophthora crown rot (PhCR) in strawberry. LR occurs sporadically but can cause up to 70% fruit loss when weather is conducive. In Florida's annual strawberry winter production system, PhCR can be severe, resulting in plant stunting, mortality, and severe yield loss. Currently, azoxystrobin is labeled for control of LR but not for PhCR. The aims of this research were i) to determine the sensitivity of P. cactorum and P. nicotianae isolates from strawberry to azoxystrobin and ii) to investigate mechanisms of QoI-resistance present in P. cactorum and P. nicotianae based on the known point mutations within the cytb gene. Isolates of both Phytophthora spp. causing LR and PhCR were collected from multiple strawberry fields in Florida between 1997 and 2020. Isolates were tested for sensitivity to azoxystrobin at 0, 0.01, 0.1, 1.0, 10, and 50 µg/ml on potato dextrose agar (PDA) amended with SHAM (100 µg/ml). Isolates were separated into two groups, sensitive isolates, with the 50% effective concentration (EC50) values lower than 1.0 µg/ml, and resistant isolates having EC50 values higher than 50 µg/ml. P. cactorum and P. nicotianae resistance to azoxystrobin was found for isolates collected after 2010. The first 450 nucleotides of the mitochondrial cytochrome b (cytb) gene were sequenced from a selection of resistant and sensitive isolates of both species. The G143A mutation reported to confer resistance to azoxystrobin was found in all resistant P. cactorum isolates. However, in P. nicotianae, qualitative resistance was observed, but the isolates lacked all the known mutations in the cytb gene. This is the first report of resistance to azoxystrobin in P. cactorum and P. nicotianae.

scholarly journals Lethal Cankers Caused by Phytophthora spp. in Almond Scions: Specific Etiology and Potential Inoculum Sources

Plant Disease ◽  
1999 ◽  
Vol 83 (8) ◽  
pp. 739-745 ◽  
Author(s):  
G. T. Browne ◽  
M. A. Viveros
Keyword(s):  
Control Strategies ◽  
Soil Surface ◽  
Crown Rot ◽  
Inoculum Sources ◽  
Disease Epidemiology ◽  
Phytophthora Spp ◽  
Almond Trees ◽  
Root And Crown Rot ◽  
Pathogenicity Tests ◽  
Significant Disease

Etiology of a new lethal canker syndrome of almond trees was investigated in the San Joaquin Valley of California. Phytophthora citricola was isolated most frequently from cankers limited to the aboveground scion portions of trees; whereas P. cactorum usually was isolated from cankers originating at or below the soil surface. Repeated observations and isolations indicated that some of the cankers associated with each species were perennial. In pathogenicity tests, isolates of P. cactorum and P. citricola caused bark cankers in excised segments of almond shoots and branches, as well as root and crown rot on potted almond seedlings. Only P. citricola caused significant disease in root and crown tissues of peach seedlings. When pear fruits and almond seedlings were used as bait, P. cactorum and P. citricola were isolated from orchard soil, debris collected in natural depressions where scaffold branches and the tree trunk joined at a common point, and debris deposited on tree surfaces during nut harvest. Control strategies for Phytophthora diseases of almond should consider aboveground as well as belowground modes of attack by P. citricola and P. cactorum. Debris infested with these pathogens and deposited on trees during harvest may play a role in the disease epidemiology.

Chemical control of crown rot in Queensland bananas

1991 ◽  
Vol 31 (5) ◽  
pp. 693 ◽  
Author(s):  
DR Jones
Keyword(s):  
Chemical Control ◽  
Good Control ◽  
Crown Rot ◽  
Postharvest Disease ◽  
Adequate Control ◽  
Fusarium Pallidoroseum ◽  
Banana Plantations

The efficacy of benomyl, prochloraz, flusilazole and other fungicides in controlling crown rot, a postharvest disease of bananas, was studied. In experiments with harvested fruit, prochloraz and flusilazole were the most effective fungicides. Benomyl was less effective than prochloraz. In 1 experiment, Fusarium pallidoroseum and a Verticillium sp. were frequently isolated from diseased crowns of untreated fruit. Both fungi were pathogenic and sensitive to prochloraz in vitro, but only F. pallidoroseum was sensitive to benomyl. The Verticillium sp. was consistently isolated from diseased crowns of benomyl-treated fruit. The failure of benomyl to control crown rot adequately in Queensland may be related to the presence of benomyl-tolerant crown rot fungi in the flora of banana plantations. In 2 experiments, prochloraz gave good control of crown rot in fruit stored for extended periods before ripening; however, it failed to give adequate control in a third.

scholarly journals Influence of native endophytic bacteria on the growth and bacterial crown rot tolerance of papaya (Carica papaya)

2021 ◽  
Author(s):  
Mark Paul Selda Rivarez ◽  
Elizabeth P. Parac ◽  
Shajara Fatima M. Dimasingkil ◽  
Eka Mirnia ◽  
Pablito M. Magdalita
Keyword(s):  
Plant Growth ◽  
Endophytic Bacteria ◽  
Plant Biomass ◽  
Growth Promotion ◽  
Bacterial Colonization ◽  
Fold Increase ◽  
Pathogen Resistance ◽  
Crown Rot ◽  
Native Plant

Abstract The native plant microbiome is composed of diverse communities that influence its overall health, with some species known to promote plant growth and pathogen resistance. Here, we show the antibacterial and growth promoting activities of autoclaved culture metabolites (ACMs) from native endophytic bacteria (NEB) in a papaya cultivar that is tolerant to bacterial crown rot (BCR) caused by Erwinia mallotivora . Initially, bacterial colonization in recovering tissues of this cultivar was observed before onset of tissue regeneration or 'regrowth'. We further isolated and characterized these bacteria and were able to identify two culturable stem NEB under genera Kosakonia (EBW), related to Enterobacter , and Sphingomonas (EBY). We also identified root NEB (BN, BS and BT) under genus Bacillus . Inhibition assays indicated that ACMs from these NEB promptly (18-30h) and efficiently inhibited (60-65%) E. mallotivora proliferation in vitro. Interestingly, when ACMs from BN and EBW were inoculated in surface-sterilized papaya seeds, germination was variably retarded (20-60% reduction) depending on plant genotype, but plant biomass accumulation was significantly stimulated, at around two-fold increase. Moreover, greenhouse experiments show that ACMs from all isolates, especially EBW, significantly reduced BCR incidence and severity in susceptible genotype, at around two-fold. In general, our observations of pathogen antagonism, plant growth promotion leading to disease reduction by ACMs of native endophytic bacteria suggested its contribution to increased fitness of papaya and tolerance against the (re)emerging BCR disease.

scholarly journals “Shining a LAMP” (Loop-Mediated Isothermal Amplification) on the Molecular Detection of Phytopathogens Phytophthora spp. and Phytophthora cactorum in Strawberry Fields

Pathogens ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1453
Author(s):  
Dominika G. Siegieda ◽  
Jacek Panek ◽  
Magdalena Frąc
Keyword(s):  
Molecular Detection ◽  
Detection Method ◽  
Molecular Techniques ◽  
Isothermal Amplification ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Loop Mediated Isothermal Amplification ◽  
Phytophthora Spp ◽  
Freeze Dried ◽  
Starting Point

Phytopathogenic microorganisms belonging to the genus Phytophthora have been recognized many times as causal agents of diseases that lower the yield of many plants important for agriculture. Meanwhile, Phytophthora cactorum causes crown rot and leather rot of berry fruits, mainly strawberries. However, widely-applied culture-based methods used for the detection of pathogens are time-consuming and often inaccurate. What is more, molecular techniques require costly equipment. Here we show a rapid and effective detection method for the aforementioned targets, deploying a simple molecular biology technique, Loop-Mediated Isothermal Amplification (LAMP). We optimized assays to amplify the translation elongation factor 1-α (EF1a) gene for two targets: Phytophthora spp. And Phytophthora cactorum. We optimized the LAMP on pure strains of the pathogens, isolated from organic plantations of strawberry, and successfully validated the assay on biological material from the environment including soil samples, rhizosphere, shoots and roots of strawberry, and with SYBR Green. Our results demonstrate that a simple and reliable molecular detection method, that requires only a thermoblock and simple DNA isolation kit, can be successfully applied to detect pathogens that are difficult to separate from the field. We anticipate our findings to be a starting point for developing easier and faster modifications of the isothermal detection methods and which can be applied directly in the plantation, in particular with the use of freeze-dried reagents and chemistry, allowing observation of the results with the naked eye.

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