Pathogenicity of Phytophthora cinnamomi Towards Nothofagus cunninghamii

1975 ◽  
Vol 23 (2) ◽  
pp. 277 ◽  
Author(s):  
G Weste
Keyword(s):  
Mating Type ◽  
Root Rot ◽  
Host Plants ◽  
Phytophthora Cinnamomi ◽  
Dry Weight ◽  
Mating Types

Two-year-old plants of Nothofagus cunninghamii were inoculated with isolates of either A1 or A2 mating types of Phytophthora cinnamomi. Both mating types were pathogenic, causing root rot and cankers, and resulting in significant reductions of height and dry weight compared with controls. Death occurred in all host plants inoculated with the A1 mating type, but in only 60% of those inocu- lated with the A2 isolate. Symptoms were correspondingly more severe in plants inoculated with the A1 mating type of the pathogen than in those inoculated with the A2 type.

scholarly journals Characterization and fungicides sensitivity of Phytophthora cinnamomi isolates causing avocado root rot in Zitácuaro, Michoacán

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Alejandra Mondragón-Flores ◽  
Patricia Manosalva ◽  
Salvador Ochoa-Ascencio ◽  
Marlene Díaz-Celaya ◽  
Gerardo Rodríguez-Alvarado ◽  
...  
Keyword(s):  
Growth Rate ◽  
Mating Type ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Potassium Phosphite ◽  
Pathogenicity Tests

<em>Phytophthora cinnamomi</em> is the pathogen most frequently associated with avocado root rot. In Zitácuaro, Michoacán, production has increased by 19.8%; however, there are no studies of root rot in this area. The objective of the study was to characterize the isolates obtained from avocado roots and assess the sensitivity to fungicides. Samples from 5 avocado orchards were collected, sampling 5 trees per orchard (a total of 25 samples). The samples isolated were characterized morphological and molecularly. Mating type was analyzed using reference isolates of<em> P. cinnamomi</em> A1 (isolate from camelia) and A2 (isolate from avocado). To confirm the pathogenicity, tests were performed on avocado fruits with the isolates. The sensitivity of 15 isolates to potassium phosphite and to metalaxyl-M at different concentrations was evaluated<em> in vitro</em>. In a subgroup of six isolates, it was evaluated whether there was a relationship between growth rate and potassium phosphite sensitivity. Fifteen isolates were obtained with coenocytic coraloid mycelium, chlamydospores, sporangia without papilla, ovoid to ellipsoid, with internal proliferation, heterothallic with mating type A2, with amphigynous antheridia and plerotic oospores, characteristics consistent with <em>P. cinnamomi</em>. The inoculated isolates were pathogenic on avocado fruits. The isolates were more sensitive to potassium phosphite than to metalaxyl-M, with mean EC50 values of 24.62 and 0.215 ?g mL-1 of i.a., respectively. No relationship was observed between growth rate and potassium phosphite sensitivity. It is necessary to obtain a greater number of<em> P. cinnamomi</em> isolates for virulence studies.

scholarly journals Implications of Irrigation Method and Amount of Water Application on Phytophthora and Pythium Infection and Severity of Root Rot in Highbush Blueberry

HortScience ◽  
2007 ◽  
Vol 42 (6) ◽  
pp. 1463-1467 ◽  
Author(s):  
David R. Bryla ◽  
Robert G. Linderman
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Canopy Cover ◽  
Dry Weight ◽  
Vaccinium Corymbosum ◽  
Highbush Blueberry ◽  
Silty Clay ◽  
Water Application ◽  
Irrigation Method ◽  
Northern Highbush Blueberry

A 2-year study was done in Oregon to determine the effects of irrigation method and level of water application on the development of root rot in northern highbush blueberry (Vaccinium corymbosum L. ‘Duke’). Plants were grown on mulched, raised beds and irrigated by overhead sprinklers, microsprays, or drip at 50%, 100%, and 150% of the estimated crop evapotranspiration requirement. Soil at the site was a silty clay loam. By the end of the first season, plants were largest with drip, intermediate-sized with microsprays and smallest with sprinklers; however, this was not the case the next season. By the end of year 2, plants irrigated by drip had less canopy cover, fewer new canes, lower pruning weights, and only half the shoot and root dry weight as plants irrigated by sprinklers or microsprays. Destructive sampling revealed that the field was infested by root rot. Less growth with drip was association with higher levels of infection by the root pathogen, Phytophthora cinnamomi. Phytophthora infection increased with water application, regardless of irrigation method, but averaged 14% with drip and only 7% with sprinklers and microsprays. Roots were also infected by Pythium spp. Pythium infection likewise increased with the total amount of water applied but, unlike P. cinnamomi, was similar among irrigation methods. Overall, drip irrigation maintained higher soil water content near the base of the plants than sprinklers and microsprays, resulting in conditions more favorable to root rot. Sprinklers and microsprays may be better alternatives than drip at sites prone to problems with the disease.

Comparative Pathogenicity of Fourteen Australian Isolates of Phytophthora cinnamomi Determined on Transplants of Tasmanian Temperate Heathland

1989 ◽  
Vol 37 (6) ◽  
pp. 491
Author(s):  
FD Podger
Keyword(s):  
Root Rot ◽  
Native Species ◽  
Host Plants ◽  
Phytophthora Cinnamomi ◽  
Single Plant ◽  
Taxonomic Affinity

Peat cores containing mature plants of 21 native species were transplanted from heathland in south- western Tasmania to a greenhouse and inoculated individually with 14 Australian isolates of Phytophthora cinnamomi. The isolates, which had been obtained from 10 different species of host plants and from 14 localities widely distributed across the continent, included three of the four isotypes of the fungus known to occur in Australia. Abnormal coloration, root-rot and death occurred in 9 of the 11 species of dicotyledons present; in a single plant of one species of the 11 monocotyledons but in neither of the two ferns. Of the nine species of dicotyledons in which disease occurred, five species were highly susceptible. Comparisons of the relative pathogenicity of isolates, based on the response of the five highly susceptible species, showed no evidence of strong differences in pathogenicity between groups of isolates, whether these groups were based on isotype of the fungus, climate at the source of the isolates or taxonomic affinity of the host plants from which they were originally isolated.

Control of sexuality in Phytophthora cinnamomi

1974 ◽  
Vol 22 (4) ◽  
pp. 669 ◽  
Author(s):  
ST Chang ◽  
CJ Shepherd ◽  
BH Pratt
Keyword(s):  
Mating Type ◽  
Phytophthora Cinnamomi ◽  
Chemical Stimulation ◽  
Mating Types ◽  
Hyphal Fusion ◽  
Field Isolates ◽  
Heterokaryon Formation ◽  
Oospore Formation

The mating type behaviour of 176 single zoospore isolates collected from 11 dissected sporangia of Phytophthora cinnamomi Rands was examined and the results confirmed previous conclusions from studies of field isolates, that two compatibility types may be involved in the formation of oospores in this fungus. The bilateral formation of sexual spores in paired cultures is believed to occur via the hyphal fusion of two compatibility types and it is thought that chemical stimulation is not involved. Oospore production is also affected by nutrition and innate characters of the isolates used. Determination of the mating reactions of terminal hyphae isolated from mixed A1 and A2 cultures suggested that extensive heterokaryosis of A1 and A2 type nuclei did not occur in the vegetative hyphae of either mating type, and that heterokaryon formation was probably restricted to the site of oospore formation. The absence of 'vegetative' heterokaryosis between the two mating types of P. cinnamomi is postulated and the control of sexuality in this fungus is discussed.

scholarly journals New Oomycota Fungicides With Activity Against Phytophthora cinnamomi and Their Potential Use for Managing Avocado Root Rot in California

Plant Disease ◽  
2019 ◽  
Vol 103 (8) ◽  
pp. 2024-2032 ◽  
Author(s):  
Rodger J. Belisle ◽  
Wei Hao ◽  
Brandon McKee ◽  
Mary Lu Arpaia ◽  
Patricia Manosalva ◽  
...  
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Dry Weight ◽  
The United States ◽  
Baseline Sensitivity ◽  
Phytophthora Root Rot ◽  
Mean Values ◽  
Potassium Phosphite ◽  
Pathogen Populations

Phytophthora root rot (PRR), caused by Phytophthora cinnamomi, is the most destructive disease of avocado worldwide. In the United States, mefenoxam and phosphonate products are currently the only registered fungicides for managing avocado PRR. Four new Oomycota-specific and two registered fungicides, all with different modes of action, were evaluated. Seventy-one isolates of P. cinnamomi from avocado in California, most of them collected between 2009 to 2017, were tested for their in vitro sensitivity to the six fungicides. Baseline sensitivity ranges and mean values (in parentheses) of effective concentrations to inhibit mycelial growth by 50% (EC50) for the new fungicides ethaboxam, fluopicolide, mandipropamid, and oxathiapiprolin were 0.017 to 0.069 μg/ml (0.035), 0.046 to 0.330 μg/ml (0.133), 0.003 to 0.011 μg/ml (0.005), and 0.0002 to 0.0007 μg/ml (0.0004), respectively. In comparison, the EC50 value range (mean) was 0.023 to 0.138 μg/ml (0.061) for mefenoxam and 12.9 to 361.2 μg/ml (81.5) for potassium phosphite. Greenhouse soil inoculation trials with 8-month-old Zutano seedlings and 10-month-old Dusa and PS.54 clonal rootstocks were conducted to assess the efficacy of these fungicides for managing PRR. Mefenoxam and potassium phosphite were effective treatments; however, oxathiapiprolin, fluopicolide, and mandipropamid were more effective. Ethaboxam was effective in reducing PRR on the rootstocks evaluated. Oxathiapiprolin reduced PRR incidence and pathogen population size in the soil by >90%, and plant shoot growth and root dry weight were significantly increased compared with the control; thus, oxathiapiprolin was one of the best treatments overall. The high activity and performance of these new fungicides supports their registrations on avocado for use in rotation and mixture programs, including with previously registered compounds, to reduce the risk of development and spread of resistance in pathogen populations.

scholarly journals First Report of Root Rot Caused by Phytophthora cinnamomi on Avocado in Italy

Plant Disease ◽  
1998 ◽  
Vol 82 (11) ◽  
pp. 1281-1281 ◽  
Author(s):  
S. O. Cacciola ◽  
A. Pane ◽  
M. Davino ◽  
G. Magnano di San Lio
Keyword(s):  
Mating Type ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Glucose Dehydrogenase ◽  
Selective Medium ◽  
Field Resistance ◽  
Persea Americana ◽  
Tropical Fruit ◽  
Experimental Field ◽  
Electrophoretic Patterns

Root rot caused by Phytophthora cinnamomi Rands is generally recognized to be the most important disease of avocado (Persea americana Miller) wherever this tropical fruit tree is grown (3). The disease was first found in Italy in the spring of 1998. Eight-year-old trees, with symptoms ranging from initial to severe, were observed in an experimental field near Rocca di Caprileone, in Sicily. Few trees showed symptoms of both root rot and collar rot. Infected trees were of 13 commercial cultivars. Trees were grafted on two different rootstocks: Hass seedlings and G6 seedlings. G6 is a selection reported to have some field resistance to P. cinnamomi infections (2). However, no correlation was observed between symptom severity and rootstock. P. cinnamomi was isolated on BNPRAH selective medium (4) from trunk bark, feeder roots, and rhizosphere soil of diseased trees, and from roots of symptomless trees. The isolates, identified primarily on the basis of morphological and cultural characteristics, formed rosaceous colonies on potato dextrose agar (PDA) and on corn meal agar (CMA) coralloid-type mycelium, with abundant hyphal swellings, which were typically spherical and in clusters. Chlamydospores were either terminal or intercalary, and often occurred in characteristic grapelike clusters. Sporangia, which were produced in saline solution (1), were broadly ellipsoidal or ovoid, persistent, non-papillate and proliferous. The identification was confirmed by the electrophoresis of mycelial proteins on polyacrylamide slab gel. The electrophoretic patterns of total soluble proteins and eight isozymes (AKP [alkaline phosphatase], EST [esterase], FUM [fumarase], GLC [NAD-glucose dehydrogenase], G6PD [glucose-6-phosphate dehydrogenase], LDH [lactate dehydrogenase], MDH [malate dehydrogenase], and SOD [superoxide dismutase]) of the isolates from avocado were identical to those of two strains of P. cinnamomi, used as reference (isolate 70473 from International Mycological Institute, U.K., and an isolate from myrtle from the Institute of Plant Pathology, University of Catania, Italy). Conversely, the electrophoretic phenotype of the P. cinnamomi isolates from avocado was clearly distinct from those of reference strains of eight other species included in Waterhouse's taxonomic group VI. Pairings with isolates of a known mating type of P. cinnamomi, P. cryptogea, and P. drechsleri revealed that all the isolates from avocado were A2 mating type. It is possible that P. cinnamomi had been introduced into the experimental field on infected symptomless nursery trees. In Italy, root rot caused by P. cinnamomi could have a significant impact on commercial avocado plantings extending over about 20 ha. Moreover, this polyphagous pathogen may be a threat to other crops as well as to forest trees. References: (1) D. W. Chen and G. A. Zentmyer. Mycologia 62:397, 1970. (2) M. D. Coffey. Plant Dis. 71:1046, 1987. (3) D. C. Erwin and O. K. Ribeiro. 1996. Phytophthora Diseases Worldwide. American Phytopathological Society, St. Paul, MN. (4) H. Masago et al. Phytopathology 67:425, 1977.

scholarly journals Tuber melanosporum: mating type distribution in a natural plantation and dynamics of strains of different mating types on the roots of nursery-inoculated host plants

2010 ◽  
Vol 189 (3) ◽  
pp. 723-735 ◽  
Author(s):  
Andrea Rubini ◽  
Beatrice Belfiori ◽  
Claudia Riccioni ◽  
Sergio Arcioni ◽  
Francis Martin ◽  
...  
Keyword(s):  
Mating Type ◽  
Host Plants ◽  
Tuber Melanosporum ◽  
Mating Types ◽  
Type Distribution

scholarly journals Influence of Root Flooding Interval on Phytophthora Root Rot of Blueberry

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 468D-468
Author(s):  
Amal. P. de Silva ◽  
W. Keith Patterson
Keyword(s):  
Disease Severity ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Linear Trend ◽  
Disease Incidence ◽  
Severe Disease ◽  
Dry Weight ◽  
Vaccinium Corymbosum ◽  
Root Dry Weight ◽  
Water Logging

Phytophthora root rot is a severe disease on blueberry (Vaccinium corymbosum L.) in poorly drained soils. The objective of the study was to determine the frequency of water-logged conditions on disease severity of blueberry. Phytophthora cinnamomi was grown on rice hulls and incorporated into the soil at the rate of 10% v/v. Water logging conditions were inflicted for 48 hr on mulched and non–mulched blueberry plants at 1-, 2-, and 4-week intervals. Non-water logging conditions were used on both mulched and non-mulched control plants. There was a significant linear relationship between disease severity of shoots and roots and the frequency of water-logging conditions. Disease symptoms were low in control plants, but disease ratings were high in mulched and non-mulched plants that were treated with water-logging conditions every week. There was also a linear trend between shoot dry weight and root dry weight of plants with frequency of water logging. Higher dry weights were seen on control plants. There was a significantly higher shoot, root dry weight and number of leaves of mulched plants than non-mulched plants. The percentage of infection on roots were high with frequent water logging. The study revealed high disease incidence with frequent water loggings. However, growth of mulched blueberry plants were comparable in control plants and plants that were subjected to water logging at 4-week intervals.

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 Cellulase Activity as a Mechanism for Suppression of Phytophthora Root Rot in Mulches

2011 ◽  
Vol 101 (2) ◽  
pp. 223-230 ◽  
Author(s):  
Brantlee Spakes Richter ◽  
Kelly Ivors ◽  
Wei Shi ◽  
D. M. Benson
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Cellulase Activity ◽  
Enzyme Concentration ◽  
Disease Suppression ◽  
In Vitro Assays ◽  
Infested Soil ◽  
Phytophthora Root Rot ◽  
Standard Curve

Wood-based mulches are used in avocado production and are being tested on Fraser fir for reduction of Phytophthora root rot, caused by Phytophthora cinnamomi. Research with avocado has suggested a role of microbial cellulase enzymes in pathogen suppression through effects on the cellulosic cell walls of Phytophthora. This work was conducted to determine whether cellulase activity could account for disease suppression in mulch systems. A standard curve was developed to correlate cellulase activity in mulches with concentrations of a cellulase product. Based on this curve, cellulase activity in mulch samples was equivalent to a cellulase enzyme concentration of 25 U ml–1 or greater of product. Sustained exposure of P. cinnamomi to cellulase at 10 to 50 U ml–1 significantly reduced sporangia production, but biomass was only reduced with concentrations over 100 U ml–1. In a lupine bioassay, cellulase was applied to infested soil at 100 or 1,000 U ml–1 with three timings. Cellulase activity diminished by 47% between 1 and 15 days after application. Cellulase applied at 100 U ml–1 2 weeks before planting yielded activity of 20.08 μmol glucose equivalents per gram of soil water (GE g–1 aq) at planting, a level equivalent to mulch samples. Cellulase activity at planting ranged from 3.35 to 48.67 μmol GE g–1 aq, but no treatment significantly affected disease progress. Based on in vitro assays, cellulase activity in mulch was sufficient to impair sporangia production of P. cinnamomi, but not always sufficient to impact vegetative biomass.

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