scholarly journals First Report of Petunia Root Rot Caused by Rhizoctonia solani in Argentina

Plant Disease ◽  
2004 ◽  
Vol 88 (1) ◽  
pp. 86-86
Author(s):  
E. R. Wright ◽  
M. C. Rivera ◽  
K. Asciutto ◽  
L. Gasoni ◽  
V. Barrera ◽  
...  
Keyword(s):  
Rhizoctonia Solani ◽  
Root Rot ◽  
Disease Incidence ◽  
Common Garden ◽  
Anastomosis Group ◽  
Fluorescent Light ◽  
First Report ◽  
Blue Solution ◽  
Crown And Root Rot ◽  
Species Taxonomy

Common garden petunias (Petunia × hybrida Hort. Vilm.-Andr.) are herbaceous annual plants with brightly colored flowers up to 10 cm in diameter. During the winter of 2002, crown and root rot were observed on plants (cv. Ultra) growing in five greenhouses in Buenos Aires. Affected plants were randomly distributed in the greenhouses, and mean disease incidence in all the greenhouses was 26%. Basal leaves turned yellow and gradually became necrotic, and infected plants were often killed. Small pieces of affected tissues were disinfested in 2% sodium hypochlorite for 1 min and plated on 2% potato dextrose agar (PDA). Fifteen isolates identified to the genus Rhizoctonia were obtained. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Hyphal branched at right angles, were constricted at the base of the branch near the union with main hyphae, and septate near the constriction. Basidia were not observed in the greenhouses or on the plates. Isolates were cultivated on water agar and incubated at 25°C for 3 days. Hyphal cells were determined to be multinucleate when stained with 1% aniline blue solution (2) and examined at ×400. Anastomosis group of one isolate was determined by using AG-4 HG II, AG-1 IA, AG-1 IB, AG-1 IC, AG-2 2-1, and AG-2 2IIIB tester strains of Rhizoctonia solani that includes isolates reported to be pathogenic on ornamentals (1). Anastomosis was observed only with strains of AG-4 HG II. Pathogenicity on this isolate was conducted on potted, healthy, adult plants that were 10 to 22 cm high and flowering. Thirty-five plants were inoculated by placing 1 cm2 pieces of PDA from 7-day-old mycelial cultures near the base of the stem. Twelve control plants were treated with 1 cm2 PDA plugs. Plants were kept at 22 to 24°C, >95% relative humidity, and 12 h of fluorescent light. Wilt symptoms due to basal stem rot appeared 7 days after inoculation, and all the inoculated plants died within 27 days. Control plants remained disease free. The pathogen was reisolated from symptomatic tissues, completing Koch's postulates. To our knowledge, this is the first report of R. solani causing disease on petunia in Argentina. References: (1) D. M. Benson and D. K. Cartwright. Ornamental diseases incited by Rhizoctonia spp. Pages 303–314 in: Rhizoctonia species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. B. Sneh et al., eds. Kluwer Academic Publishers, London, England, 1996. (2) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

scholarly journals First Report of Crown and Root Rot Caused by Rhizoctonia solani AG-4 on Banana Passionflower (Passiflora mollissima) in Italy

Plant Disease ◽  
2011 ◽  
Vol 95 (9) ◽  
pp. 1194-1194 ◽  
Author(s):  
G. Polizzi ◽  
D. Aiello ◽  
V. Guarnaccia ◽  
A. Panebianco ◽  
P. T. Formica
Keyword(s):  
Rhizoctonia Solani ◽  
Root Rot ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Fluorescent Light ◽  
Disease Symptoms ◽  
First Report ◽  
Pathogenicity Tests ◽  
Crown And Root Rot ◽  
Safranin O

The genus Passiflora (Passifloraceae family) contains more than 500 species and several hybrids. In Italy, some of these species and hybrids are grown as ornamental evergreen vines or shrubs. During August and September 2010, a crown and root rot was observed in a stock of approximately 6,000 potted 2-year-old plants of Passiflora mollissima (Kunth) Bailey, commonly known as the banana passionflower, in a nursery located in eastern Sicily (southern Italy). Disease incidence was approximately 20%. Disease symptoms consisted of water-soaked lesions at the crown and a root rot. Successively, older crown lesions turned light brown to brown and expanded to girdle the stem. As crown and root rot progressed, basal leaves turned yellow and gradually became necrotic and infected plants wilted and died. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently isolated from crown lesions and brown decaying roots when plated on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 μg/ml. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Mycelium was branched at right angles with a septum near the branch with a slight constriction at the branch base. Hyphal cells removed from 10 representative cultures grown at 25°C on 2% water agar were determined to be multinucleate when stained with 1% safranin O and 3% KOH solution (1) and examined at ×400. Anastomosis groups were determined by pairing isolates on 2% water agar in petri plates (4). Pairings were made with tester strains of AG-1, AG-2, AG-3, AG-4, AG-5, AG-6, and AG-11. Anastomosis was observed only with tester isolates of AG-4 (3). Pathogenicity tests were performed on container-grown, healthy, 3-month-old cuttings. Twenty plants of P. mollissima were inoculated near the base of the stem with five 1-cm2 PDA plugs from 5-day-old mycelial plugs obtained from two representative cultures. The same number of plants served as uninoculated controls. Plants were maintained at 25°C and 95% relative humidity with a 12-h fluorescent light/dark regimen. Wilt symptoms due to crown and root rot, identical to ones observed in the nursery, appeared 7 to 8 days after inoculation with either of the two isolates and all plants died within 20 days. No disease was observed on control plants. R. solani AG-4 was reisolated from symptomatic tissues and identified as previously described, confirming its pathogenicity. Damping-off or crown and root rot due to R. solani were previously detected on P. edulis in Brazil, Africa, India, Oceania, and Australia (2). To our knowledge, this is the first report of R. solani causing crown and root rot on P. mollissima. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) J. L. Bezerra and M. L. Oliveira. Fitopathol. Brasil. 9:273, 1984. (3) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (4) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

scholarly journals First Report of Crown and Root Rot Caused by Rhizoctonia solani AG-4 on Coprosma repens and C. lucida in Italy

Plant Disease ◽  
2009 ◽  
Vol 93 (9) ◽  
pp. 972-972 ◽  
Author(s):  
G. Polizzi ◽  
D. Aiello ◽  
I. Castello ◽  
A. Vitale
Keyword(s):  
Rhizoctonia Solani ◽  
Root Rot ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Fluorescent Light ◽  
Centraalbureau Voor ◽  
First Report ◽  
Crown And Root Rot ◽  
Stem Lesions ◽  
Safranin O

Coprosma (J.R. Forster & G. Forster), a genus containing approximately 90 species, occurs principally in New Zealand, Hawaii, Australia, New Guinea, and islands of the Pacific. In Italy, some of these species, including many variegated varieties and hybrids, are grown as ornamental evergreen shrubs or small trees. In June 2008, a crown and root rot was observed in a stock of approximately 12,000 potted 3-year-old plants of Coprosma repens cv. Yvonne and C. lucida in a nursery in eastern Sicily. Disease incidence was approximately 30%. Disease symptoms consisted of water-soaked lesions at the crown of the trunk and a root rot. Successively, older stem lesions turned orange to brown. As a consequence, leaves initially became chlorotic, gradually became necrotic, and death of the plant followed. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently isolated from crown and root lesions when plated on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 μg/ml. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Mycelium was branched at right angles with a septum near the branch and a slight constriction at the branch base. Hyphal cells removed from cultures grown at 25°C on 2% water agar were determined to be multinucleate when stained with 1% safranin O and 3% KOH solution (1) and examined at ×400. Anastomosis groups were determined by pairing isolates on 2% water agar in petri plates (3). Pairings were made with tester strains of AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, and AG-11. Anastomosis was observed only with tester isolates of AG-4, giving C2 and C3 reactions (2). Two representative isolates obtained from symptomatic tissues of C. lucida and C. repens cv. Yvonne were deposited at the Fungal Biodiversity Centre, Centraalbureau voor Schimmelcultures (DISTEF CL1 = CBS-124593 and DISTEF CR1 = CBS-124594, respectively). Pathogenicity tests were performed on container-grown, healthy, 3-month-old cuttings. Ten plants of C. lucida and ten plants of C. repens cv. Yvonne were inoculated near the base of the stem with five 1-cm2 PDA plugs from 5-day-old mycelial cultures. The same number of plants served as uninoculated controls. Plants were maintained at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Symptoms identical to ones observed in the nursery appeared 5 days after inoculation and all plants died within 15 days. No disease was observed on control plants. A fungus identical in culture morphology to R. solani AG-4 was consistently reisolated from symptomatic tissues, confirming its pathogenicity. To our knowledge, this is the first report of R. solani causing crown and root rot on the genus Coprosma. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (3) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

scholarly journals First Report of Crown and Root Rot Caused by Rhizoctonia solani AG-4 on Orange Jessamine in Italy

Plant Disease ◽  
2009 ◽  
Vol 93 (2) ◽  
pp. 204-204 ◽  
Author(s):  
D. Aiello ◽  
A. Vitale ◽  
E. Lahoz ◽  
R. Nicoletti ◽  
G. Polizzi
Keyword(s):  
Rhizoctonia Solani ◽  
Root Rot ◽  
Morphological Characteristics ◽  
Ruthenium Red ◽  
Fluorescent Light ◽  
First Report ◽  
Pectic Enzymes ◽  
Electrophoretic Patterns ◽  
Crown And Root Rot ◽  
Hyphal Diameter

Murraya paniculata (L.) Jack, commonly called orange jessamine or orange jasmine (Rutaceae), is a small tropical tree that is native to Asia. This species, closely related to Citrus, is grown as an ornamental tree or hedge. During October of 2007, crown and root rot was observed on approximately 12,000 pot-grown, 4-month-old plants in a nursery in eastern Sicily, Italy. Basal leaves turned yellow and gradually became necrotic, and infected plants often died. Disease symptoms were observed on 1,800 (15%) plants. Isolations from affected tissues on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 mg/liter recovered a fungus with mycelial and morphological characteristics consistent with Rhizoctonia solani Kühn. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Microscopic examination revealed that hyphae had a right-angle branching pattern, were constricted at the base of the branch near the union with main hyphae, and were septate near the constriction. The nuclear condition of hyphal cells was determined on cultures grown at 25°C on 2% water agar (WA) when stained with 3% safranin O solution and examined at ×400. Anastomosis groups were determined by pairing isolates on 2% WA in petri plates (4). Pairings were made with tester strains AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, and AG-11. Anastomosis was observed only with tester isolates of AG-4 producing both C2 and C3 reactions. The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and cell death of adjacent cells was observed. These results were consistent with other reports on anastomosis reactions (1). The identification of group AG-4 within R. solani has been confirmed by electrophoretic patterns of pectic enzymes (polygalacturonases) in vertical pectin-acrylamide gel stained with ruthenium red (2). Pathogenicity tests were conducted on potted, healthy, 6-month-old seedlings of orange jessamine. Twenty-five plants were inoculated by placing 1-cm2 PDA plugs from 5-day-old mycelial cultures near the base of the stem. The same number of plants inoculated with PDA plugs served as controls. Plants were maintained at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Wilt symptoms, identical to ones observed in the nursery, developed 3 months after inoculation because of crown and root rot. Control plants remained disease free. The pathogen was reisolated from symptomatic tissues, completing Koch's postulates. Collar rot due to R. solani was previously detected on M. koenigii (3). To our knowledge, this is the first report of R. solani causing disease on M. paniculata. References: (1) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (2) R. H. Cruickshank and G. C. Wade. Anal. Biochem. 107:177, 1980. (3) A. C. Jain and K. A. Mahmud. Rev. Appl. Mycol. 32:460, 1953. (4) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

scholarly journals First Report of Damping-Off Caused by Rhizoctonia solani AG-4 on Mediterranean Fan Palm in Italy

Plant Disease ◽  
2010 ◽  
Vol 94 (1) ◽  
pp. 125-125 ◽  
Author(s):  
G. Polizzi ◽  
D. Aiello ◽  
I. Castello ◽  
V. Guarnaccia ◽  
A. Vitale
Keyword(s):  
Rhizoctonia Solani ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Mediterranean Area ◽  
Western Mediterranean ◽  
Fluorescent Light ◽  
Damping Off ◽  
Centraalbureau Voor ◽  
First Report ◽  
Stem Lesions

Mediterranean fan palm (Chamaerops humilis L.), one of just two autochthonous European palms, is native to the western Mediterranean Region in southwestern Europe and northwestern Africa. It can be found growing wild in the Mediterranean area. In Europe, this species is very popular as an ornamental plant. In March 2009, a widespread damping-off was observed in a stock of approximately 30,000 potted 1-month-old plants of C. humilis cv. Vulcano in a nursery in eastern Sicily. Disease incidence was approximately 20%. Disease symptoms consisted of lesions at the seedling shoot (plumule). Stem lesions were initially orange, turned brown, and followed by death of the entire plumule or eophyll. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently isolated from lesions when plated on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 μg/ml. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Mycelium was branched at right angles with a septum near the branch and a slight constriction at the branch base. Hyphal cells removed from cultures grown at 25°C on 2% water agar were determined to be multinucleate when stained with 1% safranin O and 3% KOH solution (1) and examined at ×400. Anastomosis groups were determined by pairing isolates with tester strains AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, and AG-11 on 2% water agar in petri plates (3). Anastomosis was observed only with tester isolates of AG-4, giving both C2 and C3 reactions (2). One representative isolate obtained from symptomatic tissues was deposited at the Fungal Biodiversity Centre, Centraalbureau voor Schimmelcultures (CBS No. 125095). Pathogenicity tests were performed on container-grown, healthy, 1-month-old seedlings. Twenty plants of C. humilis cv. Vulcano were inoculated near the base of the stem with two 1-cm2 PDA plugs from 5-day-old mycelial cultures. The same number of plants served as uninoculated controls. Plants were incubated in a growth chamber and maintained at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Symptoms identical to those observed in the nursery appeared 5 days after inoculation and all plants died within 20 days. No disease was observed on control plants. A fungus identical in culture morphology to R. solani AG-4 was consistently reisolated from symptomatic tissues, confirming its pathogenicity. To our knowledge, this is the first report in the world of R. solani causing damping-off on Mediterranean fan palm. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (3) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

scholarly journals First Report of Damping-Off Caused by Rhizoctonia solani AG-4 on Lagunaria patersonii in Italy

Plant Disease ◽  
2008 ◽  
Vol 92 (5) ◽  
pp. 836-836 ◽  
Author(s):  
D. Aiello ◽  
G. Parlavecchio ◽  
A. Vitale ◽  
E. Lahoz ◽  
R. Nicoletti ◽  
...  
Keyword(s):  
Rhizoctonia Solani ◽  
Morphological Characteristics ◽  
Ruthenium Red ◽  
Fluorescent Light ◽  
Damping Off ◽  
First Report ◽  
Pectic Enzymes ◽  
Electrophoretic Patterns ◽  
Blue Solution ◽  
Hyphal Diameter

Lagunaria patersonii (Adr.) G. Don (cow itch tree) is native to Australia and tolerates salted winds. During July 2007, damping-off of cow itch tree was observed on 4-month-old seedlings growing in a commercial nursery in eastern Sicily, Italy. More than 20% of the seedlings showed disease symptoms. First symptoms consisting of water-soaked lesions at the seedling base that expand rapidly girdle the stem and collapse the seedling in a few days. Diseased tissues were disinfested for 1 min in 1% NaOCl, rinsed in sterile water, plated on potato dextrose agar (PDA) amended with streptomycin sulphate at 100 mg/l, and then incubated at 25°C. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently yielded. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Microscopic examination revealed that hyphae had a right-angle branching pattern, were constricted at the base of the branch near the union with main hyphae, and septate near the constriction. Basidia were not observed in the greenhouses or on the plates. Hyphal cells were determined to be multinucleate when stained with 0.5% aniline blue solution and examined at ×400 magnification with a microscope. Anastomosis groups were determined by pairing isolates on 2% water agar in petri plates (3). Pairings were made with tester strains of AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, AG-11. Anastomosis was observed only with tester isolates of AG-4 producing both C2 and C3 reactions. The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and cell death of adjacent cells was observed. These results were consistent with other reports on anastomosis reactions (1). The identification of group AG-4 within R. solani has been confirmed by electrophoretic patterns of pectic enzymes (polygalacturonases) in vertical pectin-acrylamide gel stained with ruthenium red (2). Pathogenicity tests were conducted on potted, healthy, 3-month-old seedlings of cow itch tree. Twenty plants were inoculated by placing plugs of PDA from 5-day-old mycelial cultures near the base of the stem. The same number of plants was treated with 1 cm2 PDA plugs as control. Plants were kept at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Wilt symptoms due to basal stem rot, identical to ones observed in the nursery, appeared 10 days after inoculation and all inoculated plants showed symptoms within 1 month. Control plants remained healthy. The pathogen was reisolated from symptomatic tissues, completing Koch's postulates. To our knowledge, this is the first report in the world of R. solani causing disease on L. patersonii. References: (1) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (2) R. H. Cruickshank and G. C. Wade. Anal. Biochem. 107:177, 1980. (3) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

scholarly journals First report of collar and root rot of faba bean caused by Rhizoctonia solani AG-2-2 IIIB in Bangladesh

Plant Disease ◽  
2021 ◽  
Author(s):  
S. K. Paul ◽  
Dipali Rani Gupta ◽  
Nur Uddin Mahmud ◽  
A.N.M. Muzahid ◽  
Tofazzal Islam
Keyword(s):  
Rhizoctonia Solani ◽  
Faba Bean ◽  
Root Rot ◽  
Disease Incidence ◽  
Management Strategies ◽  
Its Region ◽  
Anastomosis Group ◽  
Grain Legume ◽  
Collar And Root Rot ◽  
Wheat Kernels

Faba bean (Vicia faba L.) is an underutilized promising grain legume commercially grown in central and northern part of Bangladesh (Yasmin et al. 2020). In January 2021, faba bean plants exhibiting symptoms of collar and root rot and yellowing of leaves were observed in thirty plots of an experimental field at the Bangladesh Agricultural University (24.75° N, 90.50° E), Mymensingh, Bangladesh. Infected plants had dark brown to black lesions on the roots, extending above the collar region. An average disease incidence and severity was 7.16% and 6.91%, respectively. Eight diseased plants were collected from the field by uprooting one plant from each of eight randomly selected experimental plots and surface disinfected with sodium hypochlorite (0.2%) for 3 min followed by 1 min in ethanol (70%), and then rinsed three times with distilled water and dried on sterile paper towels. Collar and root pieces (5×5 mm) of symptomatic tissues were placed on Potato Dextrose Agar (PDA). Plates were incubated at 25°C for three days and isolates were purified from single-tip culture. The isolates produced brown colored mycelia often with brown sclerotia. Under microscope, fungal colonies exhibited right–angled branching with constriction at the base of hyphal branches and a septum near the originating point of hyphal branch consistent with the description of Rhizoctonia solani Kuhn (Sneh et al. 1991). The isolates grew at 35°C on PDA (5 mm/24). Molecular identification of the isolates BTRFB1 and BTRFB7 was determined by sequencing the rDNA internal transcribed spacer (ITS) region using primers ITS1 and ITS4 (White et al. 1990). A BLAST search showed that the sequences (GenBank Accession nos. MZ158299.1 and MZ158298.1) had 99.28% similarity with R. solani isolates Y1063 and SX-RSD1 (GenBank Accession nos. JX913811.1 and KC413984.1, respectively). Phylogenetic analysis revealed that the present isolates grouped with R. solani anastomosis group AG-2-2 IIIB. To confirm pathogenicity, both isolates were grown individually on sterile wheat kernels at 28°C for 6 days (D’aes et al. 2011). Faba bean seedlings were grown in plastic pots containing sterile potting mix (field soil/composted manure/sand 2:2:1 [v/v]). Two-week-old plants were inoculated by placing five infested wheat seeds adjacent to the roots. Control pots were inoculated with sterile wheat kernels using the same procedure. Plants were placed in a growth room with a 16 h/8 h light/dark photoperiod at 25 ± 2°C after inoculation. Fifteen days after inoculation, typical collar and root rot symptoms were developed on inoculated plants, similar to symptoms observed in the field. Control plants remained non-symptomatic. Finally, six isolates of R. solani were isolated from the symptomatic plants and identified by morphological and molecular analysis. Rhizoctonia solani is the causal agent of seed and root rot, hypocotyl canker, and seedling damping-off diseases of faba bean in many other countries (Rashid and Bernier 1993; Assunção et al. 2011). To our knowledge, this is the first confirmed report of Rhizoctonia solani causing collar and root rot of faba bean in Bangladesh. This finding will be helpful for the development of management strategies to control this disease and to expand the production of faba bean in Bangladesh.

scholarly journals First Report of Sugar Beet Rhizoctonia Crown and Root Rot Caused by Rhizoctonia solani AG-2-2IIIB in Shanxi Province of China

Plant Disease ◽  
2014 ◽  
Vol 98 (3) ◽  
pp. 419-419 ◽  
Author(s):  
C. Zhao ◽  
X. H. Wu
Keyword(s):  
Sugar Beet ◽  
Rhizoctonia Solani ◽  
Root Rot ◽  
Its Region ◽  
Northern China ◽  
Shanxi Province ◽  
Molecular Characteristics ◽  
First Report ◽  
Crown And Root Rot ◽  
Wheat Seeds

Sugar beet (Beta vulgaris L.) is grown worldwide as the second largest sugar crop. Sugar beet crown and root rot is an economically serious disease mainly caused by Rhizoctonia solani (teleomorph Thanatephorus cucumeris) AG 2-2 and AG 4 (1). In July 2010, at the 25- to 27-leaf stage, symptoms typically associated with crown and root rot, including dark brown to black lesions at the base of the petioles or circular to oval dark lesions (up to 10.0 mm in diameter) at the taproot, were observed on 15% of sugar beet plants collected from three sites in Shanxi Province, northern China. Pieces of internal root tissues cut from the margins between symptomatic and healthy-appearing tissue were disinfected with 0.5% NaOCl for 2 min, rinsed three times with sterile water, then placed on water ager (WA) for incubation at 25°C in the dark. After 2 days, single hyphal tips of three Rhizoctonia-like isolates (designated SX-RSD1, SX-RSD2, and SX-RSD3) were transferred to potato dextrose ager (PDA). Colonies of all isolates were brown and developed dark brown sclerotia (0.5 to 1.0 mm diameter) on the media surface after 4 and 7 days, respectively. Mycelia were branched at right angles with septa near the branches and slight constrictions at the bases of the branches were present. Average hyphal diameters of the three isolates were 8.1, 7.3, and 7.6 μm, respectively. Hyphal cells were determined to be multinucleate (4 to 9 nuclei per cell) by staining with 4′-6-diamidino-2-phenylindole (DAPI) (2). Anastomosis groups were determined by pairing with reference strains (kindly provided by N. Kondo, Hokkaido University, Japan) (2), and all three isolates anastomosed with R. solani AG-2-2IIIB. All three isolates grew well on PDA at 35°C, which separates AG-2-2IIIB from AG-2-2 IV. The internal transcribed spacer (ITS) region of rDNA was amplified from genomic DNA of these isolates with primers ITS1 (5′-TCCGATGGTGAACCTGCGG-3′)/ITS4 (5′-TCCTCCGCTTATTGATATGC-3′). Sequences (GenBank Accession Nos. KC413984, KC413985, and KC413986) were over 99% identical to those of 19 R. solani AG-2-2 IIIB isolates (e.g., FJ492146.3; strain F510). Therefore, based on the molecular characteristics and the anastomosis assay, these three isolates were identified as R. solani AG-2-2IIIB. To determine the pathogenicity of the isolates, wheat seeds were autoclaved twice for 60 min at 121°C on consecutive days and inoculated with each isolate (3). Subsequently, wheat seeds (three seeds per plant) were placed around 8-week-old sugar beet (cv. HI0305) plants at 2 cm intervals to each root and 10 mm deep in soil. Plants were grown at 25 to 27°C for 7 days in a glasshouse. All inoculated plants developed symptoms of root rot, whereas control plants inoculated with sterilized wheat seeds remained healthy. R. solani AG-2-2IIIB was consistently re-isolated from the symptomatic root tissue and was confirmed by both morphological and molecular characteristics described above, fulfilling Koch's postulates. To our knowledge, this is the first report of R. solani AG-2-2IIIB on sugar beet in Shanxi Province of China. R. solani AG2-2IIIB has been reported to be pathogenic on wheat in China (4), which is often grown in rotation with sugar beet. This rotation could increase the risk of soilborne infection to either crop by R. solani AG2-2IIIB. References: (1) R. M. Harveson et al. Compendium of Beet Diseases and Pests, American Phytopathological Society. St. Paul, MN. 2009. (2) W. C. Kronland and M. E. Stanghellini. Phytopathology. 78:820, 1988. (3) M. J. Lehtonen et al. Plant Pathol. 57:141, 2008. (4) D. Z. Yu et al., Hubei Agric. Sci. 3:39, 2000.

scholarly journals First Report of Crown Rot and Stem Rot Caused by Rhizoctonia solani AG-4 on Marmalade Bush in Italy

Plant Disease ◽  
2010 ◽  
Vol 94 (4) ◽  
pp. 486-486 ◽  
Author(s):  
G. Polizzi ◽  
D. Aiello ◽  
I. Castello ◽  
V. Guarnaccia ◽  
A. Vitale
Keyword(s):  
Rhizoctonia Solani ◽  
Anastomosis Group ◽  
Crown Rot ◽  
Fluorescent Light ◽  
First Report ◽  
Brown Discoloration ◽  
The Family ◽  
Perennial Shrub ◽  
Pathogenicity Tests ◽  
Safranin O

Marmalade bush (Streptosolen jamesonii (Benth.) Miers), also known as fire bush, is an evergreen, perennial shrub in the family Solanaceae, which is native to South America (Colombia, Ecuador, and Peru). In Italy, this species is cultivated as an ornamental creeper or bush. During September 2009, a new disease was observed in a stock of ~10,000 pot-grown, 2-month-old plants of marmalade bush in a nursery in eastern Sicily, Italy. More than 50% of the plants exhibited symptoms of disease. Disease symptoms consisted of extensive water-soaked, dark brown lesions at the crown level that girdled entire stems and an internal brown discoloration of cortical tissue. Infected plants died within a few days. Diseased tissue was disinfested for 10 s in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 mg/liter. Fungal colonies were initially white, turned brown after 2 to 3 days, and produced irregularly shaped, brown sclerotia. Microscopic examination showed mycelium consistent with Rhizoctonia solani Kühn that branched at right angles, constricted at the base of the branch originating from primary hyphae, and septate near the constriction. The number of nuclei per hyphal cell was determined on cultures grown at 25°C on 2% water agar in petri plates by staining with 1% safranin O and 3% KOH solution (1) and examined at ×400. The hyphal cells were all multinucleate. Anastomosis group was determined by pairing isolates on 2% water agar in petri plates (2). Pairings were made with tester strains AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, and AG-11. Anastomosis was observed only with tester isolates of AG-4. Pathogenicity tests were performed by placing 1-cm2 plugs of PDA from 5-day-old mycelial cultures near the base of the stem on 25 potted, healthy, 2-month-old rooted cuttings of marmalade bush. The same number of plants treated with 1-cm2 PDA plugs served as controls. Following inoculation, all plants were maintained for 20 days at 25°C and 95% relative humidity under a 12-h fluorescent light/dark regimen. Crown and stem symptoms, identical to those observed in the nursery, developed 5 days after inoculation on all inoculated plants. Control plants remained symptomless. R. solani was consistently reisolated from symptomatic tissues and identified as previously described. To our knowledge, this is the first report of R. solani causing disease on marmalade bush. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

scholarly journals Identification of Rhizoctonia solani isolates from sugar beet roots by analyzing the ITS region of ribosomal DNA

2007 ◽  
pp. 161-171 ◽  
Author(s):  
Vera Stojsin ◽  
Dragana Budakov ◽  
Barry Jacobsen ◽  
Eva Grimme ◽  
Ferenc Bagi ◽  
...  
Keyword(s):  
Sugar Beet ◽  
Rhizoctonia Solani ◽  
Ribosomal Dna ◽  
Root Rot ◽  
Its Region ◽  
Anastomosis Group ◽  
Crown Rot ◽  
Internal Transcribed Spacer Region ◽  
The Usa ◽  
Crown And Root Rot

Rhizoctonia solani (K?hn) is one of the most important sugar beet pathogens Rhizoctonia solani anastomosis groups (AGs) 2-2 and 4 are proven to be the most common pathogenic strains on sugar beet. AG 2-2 (intraspecific groups IIIB and IV) can cause root and crown rot while damping-off of seedlings is most frequently attributed to AG 4. Four isolates of R. solani from sugar beet roots showing characteristic crown and root rot symptoms, collected from different localities in Vojvodina Province, were chosen and compared to the well-characterized R. solani isolate R9, AG 2-2 IV, from the USA. All Vojvodinian isolates showed medium level of pathogenicity and were able to cause crown and root rot symptoms on inoculated sugar beet roots. Based on anastomosis reaction, isolates from Vojvodina did not belong to the AG 2-2 group. Sequencing of the ITS (internal transcribed spacer) region of ribosomal DNA was performed on the Vojvodinian isolates from R9 in order to determine their relatedness. Sequence analysis showed that these isolates were different than R9 and were closely related (99-100% sequence homology) to anastomosis group 4, subgroup HG II.

scholarly journals First Report of Phytophthora parsiana Causing Crown and Root Rot on Guayule in the United States

Plant Disease ◽  
2022 ◽  
Author(s):  
Jiahuai Hu ◽  
Austin Rueda
Keyword(s):  
United States ◽  
Root Rot ◽  
Disease Incidence ◽  
Water Extract ◽  
The United States ◽  
High Energy ◽  
First Report ◽  
Blast Analysis ◽  
Crown And Root Rot ◽  
Cox 1

Guayule (Parthenium argentatum A. Gray) is a perennial shrub plant (approximately 50 cm in height) cultivated in the southwestern United States. It produces natural low-allergenic latex, resins and high-energy biofuel feedstock. During August 2021, a crown and root rot disease was observed on 2-year-old plants of direct-seeded guayule cultivar ‘Az 2’ in research plots located in Pinal county, Arizona, where a record 36 cm of rainfall fell during monsoon season. Symptoms included yellowing of leaves, wilting, and plant death. Average disease incidence was 16%. Isolation from necrotic crown and root tissues on 10% clarified V8-PARP (Jeffers and Martin 1986) yielded Phytophthora-like colonies. Three isolates were subcultured on V8 agar and chlamydospores and hyphal swellings were abundant in 2-week-old cultures. All three isolates produced abundant noncaducous and nonpapillate sporangia ranging from 33 to 54 μm × 20 to 39 μm (average 45.5 × 28.5 μm, n = 20) in soil water extract solution. Isolates did not produce oospores after 2 weeks on carrot agar at 20°C in the dark. Isolates had optimum vegetative growth at 30 oC and grew well at 35 oC. There was no growth at 5 and 40 oC. Genomic DNA was extracted from the mycelia of three isolates using DNeasy Plant Pro Kit (Qiagen Inc., Valencia, CA) according to the manufacturer’s instructions. The internal transcribed spacer (ITS) region of rDNA, mitochondrially encoded cytochrome c oxidase 1 (cox 1) gene, and beta-tubulin (β-tub) gene were amplified with primers ITS1/ITS4 (White et al., 1990), COXF4N/COXR4N and TUBUF2/TUBUR1 (Kroon et al., 2004) and the resulting 3 amplicons were sequenced (GenBank Accession No. OK438221, OK484426, and OK484427). A BLASTn search of 811-bp amplicon (OK438221) revealed 99% match (762/766) with ITS sequences MG865562 which was Phytophthora parsiana Ex-type CPHST BL 47 from Iran. BLAST analysis of the 867-bp amplicon (OK484427) showed 99% identity (866/867) with the COX 1 sequence of P. parsiana (KC733455) from Virginia. BLAST analysis of the 941-bp amplicon (OK484426) showed 99% identity (928/938) with the β-tub sequence of P. parsiana (AY659746). To fulfill Koch’s postulates, pathogenicity tests were conducted twice on 2-week-old ‘Az 2’ guayule seedlings grown in 10 plants per 1.9-liter pot filled with a steam-disinfested potting mix. Pots were placed in a plastic container and watered three times a week by flooding, to create waterlogged conditions. Plants were maintained in a greenhouse with 12 h day/12 h night (15-28 oC) and fertilized weekly with a 20-20-20 fertilizer at 1mg/ml. Fifty plants in 5 pots were challenged with a P. parsiana isolate by drenching each pot with 50 ml of a 1×105 zoospore/ml suspension. Fifty plants in 5 pots, serving as a control, received each 50 ml of distilled water. Symptoms of wilting, root rot, and plant death were observed 1 week afterward in inoculated plants, whereas control plants remained asymptomatic. P. parsiana was reisolated from necrotic roots of inoculated plants but not from control plants. To our knowledge, this is the first report of crown and root rot in guayule caused by P. parsiana in Arizona. P. parsiana is a species known for causing root rot on woody plants such as pistachio in California (Fichtner et al., 2016) and Iran (Mostowfizadeh-Ghalamfarsa et al., 2008). Arizona is home of desert woody guayule plant. P. parsiana may represent a significant barrier to commercialization of guayule for rubber in low desert areas of Arizona. The origin, distribution, and virulence of the pathogen on Arizona guayule is currently unknown. Disease resistance evaluation may help identify resistance in guayule germplasm that are useful in breeding for resistant cultivars.

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