Ultrastructural changes in roots of peppers resistant and susceptible to Phytophthora capsici

The infection by Phytophthora capsici Leonian causes foliar blight and crown and root rot of pepper plants. The ultrastructural examination of resistant and susceptible host-pathogen interactions was conducted in the pepper cultivars Ince Sivri-35, PM217, and PM702=CM 334 following inoculation with Phytophthora capsici. Responses were characterized and compared with healthy non-inoculated controls at 2,4 and 6 days after inoculation. Numerous ultrastructural studies have been made of the interaction of various host plants Phytophthora spp. No ultrastructural studies comparing the resistant and susceptible reactions of pepper cultivars to P. capsici. have been reported. It is important to examine the ultrastructural changes in inoculated and infected tissue of resistant and susceptible pepper cultivars to P. capsici. Information reported here characterizes the processes of pathogen containment in resistant interactions and compares these with the processes occuring in susceptible interactions.After 2 days in susceptible interactions, the pathogen grew intercellularly in roots, whereas in resistant interactions only a few intercellular hyphae were observed penetrating the host cells and forming haustoria.

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Screening of Cucurbita moschata Duchesne Germplasm for Crown Rot Resistance to Floridian Isolates of Phytophthora capsici Leonian

HortScience ◽

10.21273/hortsci.46.4.536 ◽

2011 ◽

Vol 46 (4) ◽

pp. 536-540 ◽

Cited By ~ 13

Author(s):

Dario J. Chavez ◽

Eileen A. Kabelka ◽

José X. Chaparro

Keyword(s):

Root Rot ◽

Phytophthora Capsici ◽

Crown Rot ◽

Fruit Rot ◽

Cucurbita Moschata ◽

Breeding Lines ◽

Foliar Blight ◽

Disease Rating ◽

Crown And Root Rot ◽

Highly Virulent

Phytophthora capsici causes seedling death, crown and root rot, fruit rot, and foliar blight on squash and pumpkins (Cucurbita spp. L.). A total of 119 C. moschata accessions, from 39 geographic locations throughout the world, and a highly susceptible butternut squash cultivar, Butterbush, were inoculated with a suspension of three highly virulent P. capsici isolates from Florida to identify resistance to crown rot. Mean disease rating (DR) of the C. moschata collection ranged from 1.4 to 5 (0 to 5 scale with 0 resistant and 5 susceptible). Potential resistant and tolerant individuals were identified in the C. moschata collection. A set of 18 PIs from the original screen were rescreened for crown rot resistance. This rescreen produced similar results as the original screen (r = 0.55, P = 0.01). The accessions PI 176531, PI 458740, PI 442266, PI 442262, and PI 634693 were identified with lowest rates of crown infection with a mean DR less than 1.0 and/or individuals with DR = 0. Further selections from these accessions could be made to develop Cucurbita breeding lines and cultivars with resistance to crown rot caused by P. capsici.

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Soil Inoculum Production, Survival, and Infectivity of the Boxwood Blight Pathogen, Calonectria pseudonaviculata

Plant Disease ◽

10.1094/pdis-12-14-1245-re ◽

2015 ◽

Vol 99 (12) ◽

pp. 1689-1694 ◽

Cited By ~ 12

Author(s):

Norm Dart ◽

Chuanxue Hong ◽

Caryn Allen Craig ◽

J. T. Fry ◽

Xinran Hu

Keyword(s):

Root Rot ◽

Soil Inoculum ◽

Foliar Blight ◽

High Inoculum ◽

Inoculum Production ◽

Foliar Pathogen ◽

Leaves And Roots ◽

Crown And Root Rot ◽

Stem Cankers

Boxwood blight caused by Calonectria pseudonaviculata is typically expressed as a foliage disease with aboveground symptoms including defoliation, dieback and formation of dark narrow stem cankers. Whether this pathogen behaves like other Calonectria spp. and has a significant soil phase in the epidemiology of boxwood blight is not known. In this study we observed experimentally that (1) the boxwood blight pathogen consistently forms microsclerotia in artificially inoculated leaves and roots of Buxus spp., (2) soil artificially inoculated with conidia and microsclerotia of this pathogen can cause foliar blight, (3) conidia and microsclerotia can remain viable in soil for up to 3 and at least 40 weeks, respectively (4) and the pathogen can cause crown and root rot to plants only when roots and crowns are directly exposed to relatively high inoculum levels. Our results suggest that C. pseudonaviculata is primarily a foliar pathogen with a potentially epidemiologically significant soil phase.

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Role of the Shrub Tamarix nilotica in Dissemination of Fusarium oxysporum f. sp. radicis-lycopersici

Plant Disease ◽

10.1094/pdis.2001.85.7.735 ◽

2001 ◽

Vol 85 (7) ◽

pp. 735-739 ◽

Cited By ~ 6

Author(s):

Y. Rekah ◽

D. Shtienberg ◽

J. Katan

Keyword(s):

Fusarium Oxysporum ◽

Root Rot ◽

Selective Medium ◽

Sampling Location ◽

Susceptible Host ◽

Growing Seasons ◽

Tomato Field ◽

Crown And Root Rot ◽

Pathogen Populations

The saltcedar shrub Tamarix nilotica grows as a weed in the Arava region of Israel. This weed is commonly found in cultivated fields naturally infested with Fusarium oxysporum f. sp. radicis-lycopersici, the causal agent of tomato crown and root rot. Young bushes, 20 to 40 cm tall, were randomly uprooted from different fields. The roots were cut into segments which were placed on Fusarium-selective medium. Although the plants did not show any symptoms of disease, the roots of the shrub were colonized by the pathogen. The incidence of infected saltcedar plants and level of root colonization by F. oxysporum f. sp. radicis-lycopersici decreased with increasing distance of the sampling location from a tomato field infected with crown and root rot. F. oxysporum f. sp. radicis-lycopersici was also isolated from chaff of inflorescence samples taken from mature T. nilotica shrubs. Identity of the pathogen isolates obtained from T. nilotica roots and chaff samples was verified by pathogenicity and vegetative compatibility tests. Roots of T. nilotica plants sown under greenhouse conditions in soil naturally infested with F. oxysporum f. sp. radicis-lycopersici became colonized by the pathogen. Uprooting and removing saltcedar plants throughout the season from fields not cultivated with tomatoes lowered the inoculum density of F. oxysporum f. sp. radicis-lycopersici in the soil from 611 to 6 and from 176 to 10 CFU/g of soil in the 1998-99 and 1999-2000 growing seasons, respectively. These results demonstrate that T. nilotica may contribute to the buildup of the pathogen populations in the absence of a susceptible host. Colonization of saltcedar by F. oxysporum f. sp. radicis-lycopersici is an additional mechanism for survival of this pathogen in the fields and for dissemination through the spread of infested seed or chaff of T. nilotica.

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Resistance of Pepper to Phytophthora Crown, Root, and Fruit Rot Is Affected by Isolate Virulence

Plant Disease ◽

10.1094/pdis-94-1-0024 ◽

2010 ◽

Vol 94 (1) ◽

pp. 24-30 ◽

Cited By ~ 46

Author(s):

J. M. Foster ◽

M. K. Hausbeck

Keyword(s):

Root Rot ◽

Laboratory Experiments ◽

Phytophthora Capsici ◽

Fruit Rot ◽

Hot Pepper ◽

Cultivar Resistance ◽

Breeding Lines ◽

Pepper Fruit ◽

Millet Seed ◽

Crown And Root Rot

Greenhouse and laboratory experiments were conducted to determine the virulence of four Phytophthora capsici isolates from Michigan to 31 bell and hot pepper cultivars and breeding lines. Resistance to crown and root rot was assessed following the inoculation of soilless media with P. capsici–infested millet seed. In a detached fruit assay, fruit rot resistance was evaluated following inoculation with zoospore suspensions of 1.75 × 106 zoospores/ml. The four isolates differed in virulence to pepper lines screened for crown and root rot resistance and were considered to be four different physiological races. The pepper lines CM334, NY07-8001, NY07-8006, and NY07-8007 were resistant to the isolates tested. None of the commercial cultivars were resistant to P. capsici isolate 12889, but several cultivars were resistant to the other isolates screened. The isolates varied in their ability to cause infection on the fruits of the different cultivars. Overall, pepper fruit were more susceptible to P. capsici than the roots and crowns. Management of Phytophthora crown and root rot of pepper can be improved through the use of resistant cultivars. However, since isolate virulence affects resistance, cultivar resistance will need to be utilized on a local scale accordingly.

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An Inexpensive Disease Screening Technique for Foliar Blight of Chile Pepper Seedlings

HortScience ◽

10.21273/hortsci.29.10.1182 ◽

1994 ◽

Vol 29 (10) ◽

pp. 1182-1183 ◽

Cited By ~ 11

Author(s):

Tito P. Alcantara ◽

Paul W. Bosland

Keyword(s):

Root Rot ◽

Fungal Pathogen ◽

Phytophthora Capsici ◽

Symptom Development ◽

Sources Of Resistance ◽

Screening Technique ◽

Land Race ◽

Foliar Blight ◽

Leaf Surfaces ◽

Test Plants

An inexpensive, rapid, and reliable seedling screening technique was developed to identify sources of resistance to foliar blight of Capsicum annuum L. caused by the fungal pathogen Phytophthora capsici Leon. Leaf surfaces of test plants were inoculated with 500 to 1000 zoospores prepared in distilled water. Seedlings were incubated for 5 days in an easy-to-construct dew chamber and observed for symptom development. `Criollo de Morelos 334' chile seedlings, a Mexican land race resistant to root rot caused by the same fungal pathogen, were highly resistant to foliar blight. All commercial cultivars tested in this study, however, were highly susceptible. No root rot symptoms were observed in any of the foliar-inoculated plants.

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Performance and Resistance to Phytophthora Crown and Root Rot in Squash Lines

HortTechnology ◽

10.21273/horttech04636-20 ◽

2020 ◽

Vol 30 (5) ◽

pp. 608-618 ◽

Cited By ~ 1

Author(s):

Kyle E. LaPlant ◽

Gregory Vogel ◽

Ella Reeves ◽

Christine D. Smart ◽

Michael Mazourek

Keyword(s):

Root Rot ◽

Cucurbita Pepo ◽

Field Experiments ◽

Phytophthora Capsici ◽

Severe Disease ◽

Field Trials ◽

Disease Symptoms ◽

Resistant Lines ◽

Oomycete Pathogen ◽

Crown And Root Rot

Phytophthora crown and root rot, caused by the oomycete pathogen Phytophthora capsici, is a devastating disease of squash and pumpkin (Cucurbita pepo). No currently available cultivars provide complete resistance to this disease. Three newly developed squash lines and four hybrids were evaluated in greenhouse and field experiments for their resistance to phytophthora crown and root rot as well as for their horticultural performance. The three newly developed lines ranked among the most resistant entries included in 2 years of field trials. In addition, in a separate greenhouse experiment, one of the lines was shown to display the least severe disease symptoms among a group of accessions previously reported to possess partial resistance to phytophthora crown and root. Furthermore, the resistance was observed to be robust to several isolates of P. capsici. However, the phytophthora-resistant lines had reduced yield relative to standard squash cultivars. These lines are useful for continued breeding efforts toward a phytophthora crown and root rot-resistant cultivar.

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A Rapid Technique for Multiple-race Disease Screening of Phytophthora Foliar Blight on Single Capsicum annuum L. Plants

HortScience ◽

10.21273/hortsci.45.10.1563 ◽

2010 ◽

Vol 45 (10) ◽

pp. 1563-1566 ◽

Cited By ~ 10

Author(s):

Ariadna Monroy-Barbosa ◽

Paul W. Bosland

Keyword(s):

Capsicum Annuum ◽

Root Rot ◽

Recombinant Inbred Lines ◽

Phytophthora Capsici ◽

Pepper Plant ◽

Phytophthora Blight ◽

Chile Pepper ◽

Physiological Races ◽

Foliar Blight

Phytophthora blight, caused by the oomycete Phytophthora capsici Leon., is a major disease that threatens production and long-term viability of the chile pepper (Capsicum annuum L.) industry. For each phytophthora disease syndrome such as root rot, foliar blight, and stem blight separate and independent resistant systems have evolved in the host. In addition, several physiological races of the pathogen have been identified. A novel, effective, and accurate screening technique is described that allows for multiple races to be evaluated on a single plant of C. annuum. The P. capsici resistant line Criollo de Morelos-334, a susceptible cultivar, Camelot, and three New Mexico Recombinant Inbred Lines, -F, -I, -S, were used to evaluate the new technique for phytophthora foliar blight multiple-race screening. Using three P. capsici physiological races, no interaction among the physiological races was observed with this technique. This novel technique provided a rapid disease screen evaluating multiple physiological races for phytophthora foliar blight resistance in a single chile pepper plant and can assist plant breeders in selecting for disease-resistant plants.

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Resistance to Crown and Root Rot Caused by Phytophthora capsici in a Tomato Advanced Backcross of Solanum habrochaites and Solanum lycopersicum

Plant Disease ◽

10.1094/pdis-08-15-0888-re ◽

2016 ◽

Vol 100 (4) ◽

pp. 829-835 ◽

Cited By ~ 4

Author(s):

L. M. Quesada-Ocampo ◽

A. M. Vargas ◽

R. P. Naegele ◽

D. M. Francis ◽

M. K. Hausbeck

Keyword(s):

Root Rot ◽

Phytophthora Capsici ◽

Defense Responses ◽

Vegetable Crops ◽

Backcross Population ◽

Phytophthora Root Rot ◽

Disease Response ◽

Advanced Backcross ◽

Solanum Habrochaites ◽

Crown And Root Rot

Phytophthora capsici causes devastating disease on many vegetable crops, including tomato and other solanaceous species. Solanum habrochaites accession LA407, a wild relative of cultivated tomato, has shown complete resistance to four P. capsici isolates from Michigan cucurbitaceous and solanaceous crops in a previous study. Greenhouse experiments were conducted to evaluate 62 lines of a tomato inbred backcross population between LA407 and the cultivated tomato ‘Hunt 100’ and ‘Peto 95-43’ for resistance to two highly virulent P. capsici isolates. Roots of 6-week-old seedlings were inoculated with each of two P. capsici isolates and maintained in the greenhouse. Plants were evaluated for wilting and plant death three times per week for 5 weeks. Significant differences were observed in disease response among the inbred tomato lines. Most lines evaluated were susceptible to P. capsici isolate 12889 but resistant to isolate OP97; 24 tomato lines were resistant to both isolates. Heritability of Phytophthora root rot resistance was high in this population. Polymorphic molecular markers located in genes related to resistance and defense responses were identified and added to a genetic map previously generated for the population. Resistant lines and polymorphic markers identified in this study are a valuable resource for development of tomato varieties resistant to P. capsici.

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Inheritance of Phytophthora Root Rot and Foliar Blight Resistance in Pepper

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.124.1.14 ◽

1999 ◽

Vol 124 (1) ◽

pp. 14-18 ◽

Cited By ~ 48

Author(s):

Stephanie J. Walker ◽

Paul W. Bosland

Keyword(s):

Root Rot ◽

Phytophthora Capsici ◽

Dominant Gene ◽

Segregation Ratio ◽

Stem Cutting ◽

Blight Resistance ◽

Phytophthora Root Rot ◽

Resistant Parent ◽

Foliar Blight ◽

Foliar Resistance

The inheritance of resistance to Phytophthora capsici Leonian root rot and foliar blight was compared in two different Capsicum annuum L. var. annuum pod types. The seedling was screened for phytophthora root rot, while a genetically identical stem cutting was screened for phytophthora foliar blight to determine if the same gene(s) confer resistance to both disease syndromes. The susceptible parents were `Keystone Resistant Giant #3' (`Keystone'), a bell pepper type, and `Early Jalapeño', while `Criollo de Morelos-334' was the resistant parent. Resistance was observed in both F1 populations screened for phytophthora root and foliar infection indicating dominance for resistance. Reciprocal effects were not detected. To determine if the same gene(s) conferred root rot and foliar resistance, root rot screening results were matched to the corresponding foliar blight stem cutting reaction. The segregation of resistance in the F2 generations was dependent on the susceptible parent. In the F2 generation derived from `Early Jalapeño', root rot resistance and foliar blight resistance segregated in a 9:3:3:1 (root resistant/foliar resistant: root resistant/foliar susceptible: root susceptible/foliar resistant: root susceptible/foliar susceptible) ratio. One independent, dominant gene was necessary for root rot resistance, and a different independent, dominant gene was needed for foliar blight resistance. In the F2 generation derived from `Keystone', root rot and foliar blight resistance segregated in a 7:2:2:5 (root resistant/foliar resistant: root resistant/foliar susceptible: root susceptible/foliar resistant: root susceptible/foliar susceptible) ratio. This segregation ratio is expected when one dominant gene is required for root resistance, and a different dominant gene is required for foliar resistance. In addition to these two genes, at least one dominant allele of a third gene must be present for expression of root rot and foliar blight resistance.

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