scholarly journals Etiology and epidemiology of Pythium root rot in hydroponic crops: current knowledge and perspectives

2006 ◽  
Vol 32 (4) ◽  
pp. 307-321 ◽  
Author(s):  
John Clifford Sutton ◽  
Coralie Rachelle Sopher ◽  
Tony Nathaniel Owen-Going ◽  
Weizhong Liu ◽  
Bernard Grodzinski ◽  
...  
Keyword(s):  
Nutrient Solution ◽  
Root Rot ◽  
Root Zone ◽  
Pythium Ultimum ◽  
Stress Factors ◽  
Pythium Root Rot ◽  
Whole Plant ◽  
Phenolic Substances ◽  
Hydroponic Systems ◽  
The Impact

The etiology and epidemiology of Pythium root rot in hydroponically-grown crops are reviewed with emphasis on knowledge and concepts considered important for managing the disease in commercial greenhouses. Pythium root rot continually threatens the productivity of numerous kinds of crops in hydroponic systems around the world including cucumber, tomato, sweet pepper, spinach, lettuce, nasturtium, arugula, rose, and chrysanthemum. Principal causal agents include Pythium aphanidermatum, Pythium dissotocum, members of Pythium group F, and Pythium ultimum var. ultimum. Perspectives are given of sources of initial inoculum of Pythium spp. in hydroponic systems, of infection and colonization of roots by the pathogens, symptom development and inoculum production in host roots, and inoculum dispersal in nutrient solutions. Recent findings that a specific elicitor produced by P. aphanidermatum may trigger necrosis (browning) of the roots and the transition from biotrophic to necrotrophic infection are considered. Effects on root rot epidemics of host factors (disease susceptibility, phenological growth stage, root exudates and phenolic substances), the root environment (rooting media, concentrations of dissolved oxygen and phenolic substances in the nutrient solution, microbial communities and temperature) and human interferences (cropping practices and control measures) are reviewed. Recent findings on predisposition of roots to Pythium attack by environmental stress factors are highlighted. The commonly minor impact on epidemics of measures to disinfest nutrient solution as it recirculates outside the crop is contrasted with the impact of treatments that suppress Pythium in the roots and root zone of the crop. New discoveries that infection of roots by P. aphanidermatum markedly slows the increase in leaf area and whole-plant carbon gain without significant effect on the efficiency of photosynthesis per unit area of leaf are noted. The platform of knowledge and understanding of the etiology and epidemiology of root rot, and its effects on the physiology of the whole plant, are discussed in relation to new research directions and development of better practices to manage the disease in hydroponic crops. Focus is on methods and technologies for tracking Pythium and root rot, and on developing, integrating, and optimizing treatments to suppress the pathogen in the root zone and progress of root rot.

scholarly journals Report of Root Rot Caused by Pythium F-Group on Hydroponically Grown Celery in South Africa

Plant Disease ◽  
2002 ◽  
Vol 86 (4) ◽  
pp. 441-441
Author(s):  
N. Labuchagne ◽  
C. Gull ◽  
F. C. Wehner ◽  
W. J. Botha
Keyword(s):  
South Africa ◽  
Nutrient Solution ◽  
Root Rot ◽  
Apium Graveolens ◽  
Gauteng Province ◽  
Warm Summer ◽  
Hydroponic Systems ◽  
Hydroponically Grown ◽  
Zoospore Suspension ◽  
Group 1

Celery (Apium graveolens) is commonly grown in hydroponic systems in South Africa. During the warm summer months, plants often become stunted or die, with mortality as high as 70% in some systems. Affected plants show severe root rot and yellowing of the foliage. Root segments excised from symptomatic celery plants collected from various hydroponic systems in Gauteng Province, South Africa, were rinsed in sterile distilled water and plated on PARP medium (2). Pythium was isolated consistently from both rotted and symptomless roots. Isolates produced only noninflated filamentous sporangia and no oospores, conforming to the description of Pythium F-group (1). Koch's postulates were confirmed by inoculating 4-week-old celery seedlings cultivated in aerated nutrient solution in a hydroculture system in the greenhouse. A zoospore suspension (105 zoospores per ml) of Pythium F-group cultured on V8 juice agar was added to the nutrient solution at the rate of 3 ml/1iter. Control plants received no inoculum, and the experiment was repeated once. Plants were assessed after 4 weeks. All inoculated plants showed symptoms of root rot, stunting, and yellowing, whereas control plants remained healthy. Pythium F-group was recovered on PARP medium only from the roots of inoculated plants. Pythium F-group has been described as a pathogen of celery elsewhere, but to our knowledge, this is the first report of root rot caused by the fungus on celery in South Africa. References: (1) M. W. Dick. Keys to Pythium. University of Reading Press, Reading, UK, 1990. (2) S. N. Jeffers and S. B. Martin. Plant Dis. 70:1038, 1986.

A pythium root rot of muskmelon

1968 ◽  
Vol 46 (10) ◽  
pp. 1165-1171 ◽  
Author(s):  
C. D. McKeen ◽  
H. J. Thorpe
Keyword(s):  
Experimental Data ◽  
Root Rot ◽  
Pythium Ultimum ◽  
Wilt Disease ◽  
Field Soil ◽  
Southern Ontario ◽  
Pythium Root Rot ◽  
High Soil ◽  
Infested Field ◽  
Soil Temperatures

Pythium ultimum was readily isolated from the necrotic roots of young and mature muskmelon plants growing in soil in which root rot had been severe. Muskmelons planted in steamed soils inoculated with P. ultimum developed necrotic roots and aboveground symptoms closely similar to those produced in naturally infested field soil. The fungus was considerably more pathogenic at low than at high soil temperatures. All of seven commercial varieties of muskmelon commonly grown in southern Ontario were moderately to highly susceptible to P. ultimum. Experimental data support the conclusion that P. ultimum probably plays an important role in the "sudden wilt" disease of mature muskmelon plants.

scholarly journals Effects of Oxygen Deprivation and Pythium Root Rot on Sugarcane Red Rot

Plant Disease ◽  
1998 ◽  
Vol 82 (11) ◽  
pp. 1237-1241 ◽  
Author(s):  
Zhi Yin ◽  
J. W. Hoy
Keyword(s):  
Root Rot ◽  
Field Experiments ◽  
Root Zone ◽  
Atmospheric Oxygen ◽  
Oxygen Deprivation ◽  
Red Rot ◽  
Colletotrichum Falcatum ◽  
Pythium Root Rot ◽  
Humidified Air ◽  
Poor Drainage

The effects of oxygen deprivation or poor drainage and Pythium root rot on development of red rot, caused by Colletotrichum falcatum, and spring shoot population of sugarcane were evaluated under controlled and field conditions. Detached stalks of five cultivars were exposed to low atmospheric oxygen (0.5 to 2.7%), created by enclosing stalks in sealed chambers through which humidified nitrogen gas was passed for 0, 1, or 2 weeks. Stalks were then inoculated with C. falcatum and maintained for 6 weeks with humidified air flow. Red rot severity, assessed as four disease traits, was not increased by previous oxygen deprivation. In field experiments, inoculation of stalks of three cultivars with C. falcatum before planting resulted in a reduction in shoot populations the following spring. Poor drainage resulted in an additional reduction in shoot populations developing from inoculated stalks. Soil atmospheric oxygen was reduced in the root zone below planted stalks under poor drainage conditions. However, only minor reductions in oxygen were detected in the zone of elevated rows in which planted stalks were located. The detrimental effect of poor drainage on shoot populations from inoculated stalks was alleviated by metalaxyl application. Pythium root rot, caused by Pythium arrhenomanes, reduced the initial root system and growth of shoots in greenhouse experiments. The combination of P. arrhenomanes and C. falcatum inoculation increased dead bud percentage in one of two cultivars and red rot severity for both. The results suggest that spring shoot populations developing from red rot-affected stalks exposed to poor drainage can be reduced by the combined effects of red rot and Pythium root rot.

scholarly journals Improved Biocontrol Efficacy of Trichoderma harzianum 1295-22 for Foliar Phases of Turf Diseases by Use of Spray Applications

Plant Disease ◽  
1997 ◽  
Vol 81 (10) ◽  
pp. 1132-1138 ◽  
Author(s):  
C.-T. Lo ◽  
E. B. Nelson ◽  
G. E. Harman
Keyword(s):  
Trichoderma Harzianum ◽  
Root Rot ◽  
Field Experiments ◽  
Root Zone ◽  
Creeping Bentgrass ◽  
Dollar Spot ◽  
Trichoderma Spp ◽  
Brown Patch ◽  
Pythium Root Rot ◽  
Spray Applications

Trichoderma harzianum strain 1295-22 is an effective biocontrol agent for several fungal diseases. The efficacy of granule and spray applications of strain 1295-22 for control of Pythium root rot, brown patch, and dollar spot of creeping bentgrass was investigated. Spray applications of conidial suspensions (SA) of strain 1295-22 significantly reduced all three diseases of creeping bentgrass turf in both greenhouse and field experiments. Control was greatest when Triton X-100 at 0.1% was added to aqueous spray suspensions. When SA were applied weekly, the biocontrol treatments were equivalent to standard fungicides. Broadcast granule applications (GA) also significantly reduced foliar symptoms of Pythium root rot, dollar spot, and brown patch; turf quality also was enhanced. The populations of Trichoderma spp. in the root zone of a bentgrass putting green treated with SA or GA of strain 1295-22 increased 10- to 100-fold after treatment compared with untreated plots. However, strain 1295-22 was present at high levels on bentgrass leaves only following SA. Collectively, the results suggest that strain 1295-22 possesses both rhizosphere and phylloplane competence. The combination of broadcast applications of granules followed by spray applications of conidia reduced damage from both root and foliar diseases.

scholarly journals Efficacy of Various Biological Control Agents and Biorationals against Pythium Root Rot in Poinsettia

2003 ◽  
Vol 13 (1) ◽  
pp. 149-153 ◽  
Author(s):  
M. Little ◽  
W. Brown ◽  
T.J. Blom ◽  
J.A. Gracia-Garza ◽  
K. Schneider ◽  
...  
Keyword(s):  
Root Rot ◽  
Pythium Ultimum ◽  
Common Disease ◽  
Root Weight ◽  
Environmental Implications ◽  
Biological Origin ◽  
Development Of Resistance ◽  
Pythium Root Rot ◽  
Significant Difference ◽  
Legitimate Concern

Pythium root rot (Pythium spp.) is a common disease of greenhouse-grown poinsettias (Euphorbia pulcherrima) that can cause serious plant loss or reduction in plant quality. Application of effective chemical fungicides to poinsettia plants has reduced losses due to Pythium; however, development of resistance to these fungicides is a legitimate concern, as well as the environmental implications of using chemical pesticides. In this study, a group of products of biological origin and known biocontrol agents were evaluated for their efficacy to control pythium root rot of poinsettia. These products and organisms were compared to metalaxyl (Ridomil), a fungicide commonly used to reduce losses to Pythium. The results showed that two products based on two different species of Streptomyces, Mycostop and Actino-Iron, were as effective as metalaxyl at reducing the symptoms associated with pythium root rot when artificially inoculated with Pythium ultimum var. ultimum compared to the control plants. Many roots remained functional throughout the duration of the experiments and the overall appearance and number of bracts of commercial quality of the plants were similar for the three treatments mentioned above. In an additional experiment, Mycostop was tested in combination with a single application of metalaxyl either at 3, 7, or 11 weeks after transplanting. Plants inoculated with P. ultimum var. ultimum and treated with metalaxyl either on week 3 or 7 after transplanting in combination with two applications of Mycostop, had greater fresh root weight than those only treated with metalaxyl at week 11 or the chemical control (three applications of metalaxyl). However, there was no significant difference in the number of bracts or the bract diameter between plants treated with metalaxyl at weeks 3 or 7 followed by Mycostop and those plants treated with the fungicide alone. A reduction in the amount of fungicide used to control pythium root rot can be achieved when used in combination with a biocontrol agent without compromising the health of poinsettias.

scholarly journals Pythium Root Rot and Growth Responses of Organically Grown Geranium Plants to Beneficial Microorganisms

HortScience ◽  
2009 ◽  
Vol 44 (6) ◽  
pp. 1622-1627 ◽  
Author(s):  
Valérie Gravel ◽  
Claudine Ménard ◽  
Martine Dorais
Keyword(s):  
Pseudomonas Putida ◽  
Root Rot ◽  
Dry Weight ◽  
Pythium Ultimum ◽  
Organic Production ◽  
Plant Production ◽  
Trichoderma Atroviride ◽  
Growth Responses ◽  
Pythium Root Rot ◽  
Organically Grown

Pythium root rot, caused by Pythium ultimum, is responsible for important losses in geranium plant production, mainly as a result of the decrease in the plant overall quality. An organic production system for geranium plants based on fertilization using a filtered suspension of dehydrated hen manure was compared with a conventional fertilization system to evaluate their tolerance to root disease. Under typical greenhouse conditions, geranium plants were inoculated with a suspension of Pseudomonas putida, Trichoderma atroviride, a mixture of both or with Trichoderma harzianum, and a commercially available product, Rootshield®, 1 and 4 weeks after planting. Four weeks after the first inoculation, Pseudomonas putida and Trichoderma atroviride stimulated plant growth (shoot and root dry weight) compared with the control regardless of the fertilization. The results also showed that the colonization of geranium roots by Pythium spp. was significantly lower for organically grown plants for all treatments compared with the inoculated control under conventional fertilization. Inoculation with T. atroviride under conventional fertilization was the only treatment that did not significantly reduce root colonization by Pythium spp. compared with the conventional control. For both organically and conventionally grown plants, the coinoculation with both P. putida and T. atroviride resulted in the weakest colonization of roots by the pathogen. The inoculation of P. putida, T. atroviride, and the mixture of the bacterium and the fungus also significantly increased the fresh and dry weight of roots regardless of the fertilization used. All microorganism treatments in conventionally grown plants significantly increased the fresh and dry weight of the shoot compared with the control.

scholarly journals Stress Detection Using Proximal Sensing of Chlorophyll Fluorescence on the Canopy Level

2021 ◽  
Vol 3 (3) ◽  
pp. 648-668
Author(s):  
Linnéa Ahlman ◽  
Daniel Bånkestad ◽  
Sammar Khalil ◽  
Karl-Johan Bergstrand ◽  
Torsten Wik
Keyword(s):  
Abiotic Stress ◽  
Chlorophyll Fluorescence ◽  
Powdery Mildew ◽  
Pythium Ultimum ◽  
Stress Factors ◽  
Biological Information ◽  
Proximal Sensing ◽  
Whole Plant ◽  
High Throughput Phenotyping ◽  
Light Excitation

Chlorophyll fluorescence is interesting for phenotyping applications as it is rich in biological information and can be measured remotely and non-destructively. There are several techniques for measuring and analysing this signal. However, the standard methods use rather extreme conditions, e.g., saturating light and dark adaption, which are difficult to accommodate in the field or in a greenhouse and, hence, limit their use for high-throughput phenotyping. In this article, we use a different approach, extracting plant health information from the dynamics of the chlorophyll fluorescence induced by a weak light excitation and no dark adaption, to classify plants as healthy or unhealthy. To evaluate the method, we scanned over a number of species (lettuce, lemon balm, tomato, basil, and strawberries) exposed to either abiotic stress (drought and salt) or biotic stress factors (root infection using Pythium ultimum and leaf infection using Powdery mildew Podosphaera aphanis). Our conclusions are that, for abiotic stress, the proposed method was very successful, while, for powdery mildew, a method with spatial resolution would be desirable due to the nature of the infection, i.e., point-wise spread. Pythium infection on the roots is not visually detectable in the same way as powdery mildew; however, it affects the whole plant, making the method an interesting option for Pythium detection. However, further research is necessary to determine the limit of infection needed to detect the stress with the proposed method.

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