scholarly journals First Report of Stem Rot and Wilt of Sunflower Caused by Sclerotinia minor in Spain

Plant Disease ◽  
2002 ◽  
Vol 86 (6) ◽  
pp. 697-697
Author(s):  
M. L. Molinero-Ruiz ◽  
J. M. Melero-Vara

In 2001, sunflower (Helianthus annuus L.) plants with symptoms of stem and root rot and wilt were observed in Soria, Spain. Light brown, water-soaked lesions developed on the collar of infected plants and extended along the stem, affecting the pith and causing early and sudden wilt. White mycelium and sclerotia (0.5 to 2 mm long) formed in the pith of stems. The sclerotia were disinfested in NaClO (10% vol/vol) for 1 min, transferred to potato dextrose agar (PDA), and incubated at 20°C. The fungus consistently obtained was identified as Sclerotinia minor Jagger (1). Pathogenicity was confirmed in a greenhouse experiment (15 to 25°C, 13 h light). Seven-week-old plants of six genotypes of sunflower (‘Peredovik’, HA89, HA821, HA61, RHA274, and HA337) were inoculated by placing one PDA disk with active mycelial growth adjacent to each basal stem just below the soil line and covering it with peat/sand/silt (2:2:1, vol/vol). Six plants of each genotype were inoculated without wounding, and another six were inoculated immediately after stem base wounding with a scalpel; six wounded and uninoculated plants were used as controls. First symptoms (wilting) appeared 4 days after inoculation in all genotypes. Two weeks after inoculation, the percentage of dead plants ranged from 33 to 92% (depending on cultivar), white mycelium was observed at the base of affected plants, and sclerotia were present in the pith of diseased plants. There was no effect of plant wounding on disease incidence or severity, and the fungus was reisolated from inoculated plants. To our knowledge, this is the first report of S. minor in Spain. Reference: (1) L. M. Kohn. Mycotaxon IX 2:365, 1979.

Plant Disease ◽  
2005 ◽  
Vol 89 (8) ◽  
pp. 913-913
Author(s):  
C. Eken ◽  
S. Ercişli ◽  
A. Eşitken ◽  
E. Demirci ◽  
G. Y. Yuen

Orchis palustris Jacq. is a wild orchid native to wetlands in eastern Anatolia. During June of 2003, near Erzurum, Turkey, a decline of this orchid was observed in several meadows that had been irrigated for forage production. Stems were chlorotic, wilted, and collapsed. There was a soft, watery rot at the crowns and lower stems. White mycelium and black sclerotia formed on necrotic stem and crown tissues. The fungus was isolated from sclerotia on potato dextrose agar (PDA) and identified as Sclerotinia minor Jagger on the basis of small sclerotia (0.5 to 2.5 mm long) scattered throughout the colonies (2). Pathogenicity was confirmed by inoculating stems of 8-week-old plants with mycelial plugs from 5-day-old PDA cultures and enclosing inoculated plants in transparent plastic bags for 3 days. After 2 weeks, symptoms similar to those in the field were observed, and S. minor was reisolated from inoculated plants. Noninoculated control plants remained asymptomatic. The disease was previously observed on O. laxiflora Lam. in Turkey (1), but to our knowledge, this is the first report of S. minor infecting O. palustris References: (1) C. Eken et al. Plant Pathol. 52:802, 2003. (2) L.M. Kohn. Phytopathology 69:881, 1979.


Plant Disease ◽  
2013 ◽  
Vol 97 (9) ◽  
pp. 1250-1250 ◽  
Author(s):  
S. T. Koike

Mexican sunflower (Tithonia rotundifolia) is a plant in the Asteraceae that is grown commercially as a cutflower commodity and also as a beneficial insectary plant. In June 2012 in coastal California (Santa Cruz County), several fields of organic lettuce (Lactuca sativa) were interplanted with direct-seeded rows of Mexican sunflower (cv. Torch) in order to attract beneficial insects. When approximately 2 to 3 weeks from harvest, lettuce plants began to wilt and collapse. Lettuce crowns were decayed and covered with white mycelium and small (0.5 to 3 mm diameter), irregularly shaped, black sclerotia. These plants were confirmed to have lettuce drop disease caused by Sclerotinia minor (2). In addition, Mexican sunflower plants began to wilt and eventually died. Initial symptoms on crowns and bases of the main stems in contact with soil consisted of a light tan discoloration. These discolored areas turned darker brown, became necrotic, and later were covered with white mycelium and sclerotia that were identical to those found on lettuce. Symptomatic sunflower stems were surface disinfested and small pieces from the margins of necrotic areas were placed into petri plates containing acidified potato dextrose agar. Resulting fungal colonies were white, produced profuse numbers (approx. 39 sclerotia/cm2) of small black sclerotia, and were identified as S. minor. Six-week-old Mexican sunflower plants grown in a peat moss-based rooting medium in 5-cm square pots were used to test the pathogenicity of four isolates. Isolates were grown on cubed and autoclaved potato pieces and resulting sclerotia were recovered and dried (1). For each isolate, 12 plants for each of three cultivars (cvs. Fiesta del Sol, Torch, and Yellow Torch) were inoculated by placing 3 to 5 sclerotia 1 cm below the soil level and adjacent to the plant crowns/stem bases. Sterile sand was placed next to crowns of the control plants. Plants were maintained in a greenhouse at 22 to 24°C. Symptom development was rapid and after 6 to 7 days, inoculated Tithonia plants exhibited brown necrosis at inoculated areas. After 10 days, Tithonia crowns were decayed and plants wilted. S. minor was reisolated from selected necrotic crown and stem tissues. Diseased plants that were not used for reisolations later supported the growth of the characteristic white mycelium and black sclerotia. There were no significant differences between the Tithonia cultivars, and overall disease incidence ranged from 74 to 100%. Non-inoculated plants were asymptomatic. The experiment was repeated and results were similar. In addition, the sclerotia of the four Tithonia isolates were similarly inoculated onto sets of 12 romaine lettuce plants (cv. Green Towers). After 5 to 6 days, all plants developed lettuce drop disease and the pathogen was reisolated. To my knowledge, this is the first report of Mexican sunflower as a host of S. minor. These findings indicate that Mexican sunflower and lettuce are susceptible to the same lettuce drop pathogen, and that this beneficial insectary plant could increase soilborne inoculum of S. minor. Growers should therefore be aware of the host status of beneficial insectary and other plants interplanted with crops. References: (1) P. Chitrampalam et al. Phytopathology 101:358, 2011. (2) K. V. Subbarao. Plant Dis. 82:1068, 1998.


Plant Disease ◽  
1998 ◽  
Vol 82 (1) ◽  
pp. 129-129 ◽  
Author(s):  
C. A. Clark ◽  
M. W. Hoy ◽  
J. P. Bond ◽  
C. Chen ◽  
Y.-K. Goh ◽  
...  

Bacterial root and stem rot of sweetpotato (Ipomoea batatas (L.) Lam.) was first fully characterized in the U.S. in 1977 (2). It was thought to be caused exclusively by Erwinia chrysanthemi. Although a previous report described sweetpotato as a host for E. carotovora subsp. carotovora, based on artificial inoculations, others have reported that neither E. carotovora subsp. carotovora nor E. carotovora subsp. atroseptica decay sweetpotato storage roots (1). In October 1995, storage roots of sweetpotato cv. Beauregard were received from St. Landry Parish, LA, that displayed typical bacterial root rot. Isolations from these roots yielded bacteria that showed a similarity of 0.945 to E. carotovora subsp. carotovora with the Biolog GN Bacterial Identification System (version 3.50). This isolate (Ecc-LH) also differed from isolates of E. chrysanthemi (Ech) from sweetpotato and other hosts in that it was insensitive to erythromycin, did not produce phosphatase or lecithinase, and did not produce gas from glucose. Ecc-LH differed from known strains of E. carotovora subsp. atroseptica in that it did not produce reducing substances from sucrose or acid from palatinose. When Beauregard storage roots were inoculated by inserting micropipette tips containing 50 μl of 1.0 × 108 CFU/ml, both Ecc-LH and Ech-48 produced typical bacterial root rot symptoms. However, when they were compared by infectivity titrations at 28 to 32°C, Ecc-LH was less virulent than Ech-48. Ecc-LH had an ED50 of approximately 1.0 × 106 CFU/ml and did not cause appreciable disease below inoculum concentrations of 1.0 × 105, whereas Ech-48 had an ED50 of approximately 1.0 × 108 and caused soft rot at the lowest concentration tested, 1.0 × 103. Similar disease incidence was observed in infectivity titrations at 22 to 24°C, but Ech-48 caused less severe soft rot. E. carotovora subsp. carotovora was reisolated from inoculated storage roots and its identity was reconfirmed by Biolog. When terminal vine cuttings of Beauregard were dipped in 1.0 × 108 CFU/ml and planted in a greenhouse, bacterial stem rot symptoms developed on plants inoculated with Ech-48 at about 4 weeks postinoculation, or when new growth began. However, no symptoms developed on plants inoculated with Ecc-LH. This is the first report of natural occurrence of E. carotovora subsp. carotovora causing bacterial root rot of sweetpotato in Louisiana. E. chrysanthemi remains the most important pathogen causing bacterial soft rot in sweetpotato since it is widely associated with sweetpotato, is more virulent on storage roots and also causes a stem rot. E. carotovora subsp. carotovora can cause root rot, but has been isolated in only one location to date, is less virulent on storage roots, and apparently does not cause stem rot on the predominant cultivar in U.S. sweetpotato production, Beauregard. References: (1) C. A. Clark and J. W. Moyer. 1988. Compendium of Sweet Potato Diseases. American Phytopathological Society, St. Paul, MN. (2) N. W. Schaad and D. Brenner. Phytopathology 67:302, 1977.


Plant Disease ◽  
2001 ◽  
Vol 85 (12) ◽  
pp. 1287-1287
Author(s):  
E. R. Wright ◽  
M. C. Rivera ◽  
K. Asciutto ◽  
L. Gasoni

During 2001, basal stem rot, wilt, and plant death were observed on 30% of the plants in a crop of Dianthus plumarius L. ‘Telstar’ in Buenos Aires. Pieces of diseased stems ≈1 cm long were surface-disinfested in 2% NaOCl for 1 min and cultured on 2% potato dextrose agar (PDA), pH 7, at 22 to 24°C. After 7 days, an identical fungus was consistently isolated from pieces of infected tissue. Colonies initially were white, turned brown after 2 to 3 days, and eventually formed irregularly shaped sclerotia. Cultures exhibited morphological characteristics typical of Rhizoctonia solani Kühn (2) and were identified with known anastomosis group tester isolates (1). Positive anastomosis was observed with tester strains of R. solani AG-4-HG-II. One isolate was tested for pathogenicity by placing two pieces of PDA (1 cm2) containing 7-day-old mycelial growth ≈0.5 cm from the base of healthy 2-month-old plants. Control plants were treated with sterile pieces of PDA using the same procedures. Ten replicate plants were used for each treatment. Plants were maintained at 22 to 24°C under 95 to 100% relative humidity and a 12-h light/dark photoperiod. After 7 days, symptoms developed that were similar to those originally observed, and Koch's postulates were satisfied by reisolating the fungus. To our knowledge, this is the first report of R. solani AG4-HG-II causing disease on D. plumarius in Argentina. References: (1) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St. Paul, MN, 1991. (2) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.


Plant Disease ◽  
2019 ◽  
Vol 103 (7) ◽  
pp. 1613-1620 ◽  
Author(s):  
Xue-ping Huang ◽  
Jian Luo ◽  
Yu-fei Song ◽  
Bei-xing Li ◽  
Wei Mu ◽  
...  

Sclerotinia sclerotiorum, which can cause Sclerotinia stem rot, is a prevalent plant pathogen. This study aims to evaluate the application potential of benzovindiflupyr, a new generation of succinate dehydrogenase inhibitor (SDHI), against S. sclerotiorum. In our study, 181 isolates collected from different crops (including eggplant [n = 34], cucumber [n = 27], tomato [n = 29], pepper [n = 35], pumpkin [n = 32], and kidney bean [n = 25]) in China were used to establish baseline sensitivity to benzovindiflupyr. The frequency distribution of the 50% effective concentration (EC50) values of benzovindiflupyr was a unimodal curve, with mean EC50 values of 0.0260 ± 0.011 μg/ml, and no significant differences in mean EC50 existed among the various crops (P > 0.99). Benzovindiflupyr can effectively inhibit mycelial growth, sclerotial production, sclerotial shape, and myceliogenic and carpogenic germination of the sclerotia of S. sclerotiorum. In addition, benzovindiflupyr showed good systemic translocation in eggplant. Using benzovindiflupyr at 100 μg/ml yielded efficacies of 71.3 and 80.5% for transverse activity and cross-layer activity, respectively, which were higher than those of acropetal and basipetal treatments (43.6 and 44.7%, respectively). Greenhouse experiments were then carried out at two experimental sites for verification. Applying benzovindiflupyr at 200 g a.i. ha−1 significantly reduced the disease incidence and severity of Sclerotinia stem rot. Overall, the results demonstrated that benzovindiflupyr is a potential alternative product to control Sclerotinia stem rot.


Plant Disease ◽  
2020 ◽  
Author(s):  
Hongmiao Wu ◽  
Jiachun Wu ◽  
Feng Li ◽  
Ling Zheng ◽  
Jingkai Fan ◽  
...  

Radix pseudostellariae L. is one of the most common and highly-prized Chinese medicinal plants with various pharmacological effects, and mainly produced in acid soils in the Guizhou and Fujian provinces of southwestern and southeastern China, respectively (Wu et al. 2020). However, consecutive monoculture of R. pseudostellariae results in severe root rot and decline in biomass and quality of underground tubers. Root tubers of R. pseudostellariae are typically planted in December and harvested in next June. Root rot commonly starts developing in May. The disease incidence of root rot was ranging from 37 to 46% in root portions and basal stem of R. pseudostellariae under the consecutive monoculture fields in Shibing County, Guizhou Province, China (108°12ʹE, 27°03ʹN) (Li et al. 2017). Severe root rot was observed in Shibing County in May 2018. Infected plants displayed curly, withered, and yellow leaves, blight, retarded growth, root rot, and yield losses. Abundant whitish mycelia were observed on roots and surrounding soil. Two fungal isolates, designated GZ20190123 and GZ20190124, were obtained from symptomatic roots cultured on potato dextrose agar (PDA). The optimum temperature range for growth of the two isolates was 25 to 30°C. The optimum pH range for the growth of GZ20190123 was 5 to 5.5, whereas GZ20190124 grew better between pH 5 to 8.5. The mean mycelial growth rates of GZ20190123 and GZ20190124 at 30°C were 2.1 and 1.5 cm/day, respectively. Conidia of the two isolates were ovoid or obclavate and were produced in single or branched chains. The internal transcribed spacer (ITS) region was amplified with primers ITS1 and ITS4 (White et al. 1990). The sequences were deposited in GenBank as accession No. MN726736 for GZ20190123 and MN726738 for GZ20190124. Sequence comparison revealed 99% (GZ20190123) and 97% (GZ20190124) identity with previously reported isolate xsd08071 of Mucor racemosus Bull. (accession No. FJ582639.1) and isolate BM3 of Mucor fragilis Bainier (accession No. MK910058.1), respectively, which was confirmed by phylogenetic analysis. The two isolates were tested for pathogenicity on R. pseudostellariae. Six roots of R. pseudostellariae were surface-sterilized with 75% ethanol and stab inoculated with mycelia using a sterile toothpick for each isolate. Sterile distilled water was stab inoculated to twelve roots to serve as the control. Treated roots were incubated in a greenhouse with 16 h day length [light intensity 146.5 μmol/(m2·s)] and day/night temperature 26°C/18°C. The inoculated roots showed the expected symptoms on roots and sprouts 7 days after inoculation, whereas the control roots with sprouts did not show any symptom. The fungi were re-isolated from the diseased roots and confirmed as expected M. racemosus or M. fragilis based on the ITS sequences, which satisfied Koch’s postulates. Thus, isolate GZ20190123 was identified as M. racemosus and GZ20190124 as M. fragilis. Previously, M. racemosus and M. fragilis have been reported as a pathogen on tomato (Kwon and Hong 2005) and grape (Ghuffar et al. 2018), respectively. To our knowledge, this is the first report of M. racemosus and M. fragilis causing root rot of R. pseudostellariae in southwestern China, where the disease could cause a significant loss to production of this important medicinal plant.


Author(s):  
Ashish Kumar Gupta ◽  
Ravish Choudhary ◽  
Bishnu Maya Bashyal ◽  
Ishwar Singh Solanki

The incidence of Sclerotinia rot disease was recorded on various pigeonpea cultivars from flowering initiation to pod formation stage during the years 2012-13 and 2013-14. Critical symptoms of the disease were observed as formation of cottony white mycelium along with number of sclerotia on infected tissues. The pathogen was characterized on the basis of morphological and pathological traits. The cool wet winter with average minimum and maximum temperatures (9.2 and 21.0 ºC) and more than 93% relative humidity play an important role for stem rot disease development and spread in pigeonpea crop. The pigeonpea cultivar, ‘ICPL-151’ showed maximum disease incidence, twig infection and yield losses up to 73.35%, 23.58% and 15.70%, respectively, while ‘Kudrat’ and ‘MAL-13’ cultivars were found completely resistant to the disease.


Nukleonika ◽  
2015 ◽  
Vol 60 (3) ◽  
pp. 679-682 ◽  
Author(s):  
Magdalena Ptaszek ◽  
Leszek B. Orlikowski ◽  
Wojciech Migdał ◽  
Urszula Gryczka

Abstract Effectiveness of electron beam irradiation was evaluated against Phytophthora nicotianae var. nicotianae, the causal agent of stem base and root rot of tomato. In laboratory trials, irradiation of 7-day-old Phytophthora cultures growing on potato-dextrose-agar (PDA) medium with 1 kGy resulted in the disintegration of the pathogen’s hyphae. Increasing the irradiation dose to 3 kGy caused decay of the hyphae. Irradiation of infested stonewool with 5 kGy caused decrease of the pathogen population about 5 times. Application of 20 kGy completely eliminated the pathogen from stonewool. Irradiation of substratum resulted in significant increase of tomato seedlings healthiness, especially when the dose 20 kGy was applied.


Plant Disease ◽  
2002 ◽  
Vol 86 (7) ◽  
pp. 813-813
Author(s):  
J. P. Mansilla ◽  
O. Aguín ◽  
M. C. Salinero

Camellias are widely cultivated in gardens and grown in nurseries for plant and flower production in northwestern Spain. Camellia japonica L. is most frequently grown, but many other camellia species and hybrids are also produced. In spring 1998, plants of Camellia sp. from a garden were observed to be affected by a root fungal pathogen, that formed a white mycelium that covered most of the roots, while aboveground plant parts showed a general decline. Infected roots were macerated and discolored. Fragments of the infected roots were surface-sterilized and placed in petri dishes containing potato dextrose agar and incubated at 24°C in the dark. The fungus formed a white mycelium that turned black in 1 week, developing pyriform swellings characteristic of Rosellinia necatrix Prill (1). To confirm pathogenicity, inoculum of the isolate was produced on wheat (Triticum aestivum L.) seeds autoclaved in glass vessels for 30 min at 120°C. Wheat seed cultures were started from disks of R. necatrix mycelium and grown at 24°C in the dark for 30 days. Pathogenicity tests were conducted on 48 2-year-old plants of the hybrid Camellia × williamsii cv. Mary Phoebe Taylor, which had been grown in 1.5-liter pots (one plant per pot) filled with soil in a glasshouse. The R. necatrix isolate was inoculated by adding 30 g of infected wheat seeds to each pot. The inoculum was mixed thoroughly with the substrate before potting. Another set of pots was left uninoculated, and served as a control. All pots were randomly arranged in a growth chamber at 22 to 24°C with a 12-h photoperiod. Seventeen days after inoculation, aerial symptoms of chlorosis and leaf fall were observed, while control plants remained symptomless. Inoculated plants died 3 months after inoculation. R. necatrix was reisolated from roots of all infected plants. To our knowledge, this is the first report of a root rot of camellia caused by R. necatrix, a pathogen causing white root rot mainly in deciduous fruit crops. Reference: (1) S. Freeman and A. Sztejnberg. Pages 71–73 in: Methods for Research on Soilborne Phytopathogenic Fungi. The American Phytopathological Society, St. Paul, MN, 1992.


2019 ◽  
Vol 15 (2) ◽  
pp. 53-58
Author(s):  
Antok Wahyu Sektiono ◽  
Syamsuddin Djauhari ◽  
Putri Devinta Pertiwi

Sclerotium rolfsii, a the Causal Agent of Stem Rot Disease on Hippeastrum sp.Symptoms of stem rot that cause Hippeastrum sp. or red lily wither, leaves turn yellow, and eventually die found at Mangliawan Village, District of Pakis, Malang - East Java. The purpose of this study was to identify the pathogens that cause root rot disease on lily plants and find out their host range. Sclerotium from the symptomatic base of the plant was isolated on potato dextrose agar medium. Fungus was identified based on the morphological characteristics of the colonies and mycelium. Host range test of pathogen was carried out by manual inoculation on Rain lily (Zephyranthes) St. Bernard's lily (Chlorophytum) and Beach Spider lily (Hymenocallis). The results of the identification showed that the fungus had white mycelium and formed sclerotium. Sclerotium is irregularly rounded, white when young, and dark brown when ripe, and forms 10 days after incubation. In hyphae, there are branching, septa, and clam connections. Based on the morphological characteristics of the disease the fungus was identified as Sclerotium rolfsii. In the host range test, the fungus was able to infect rain lilies and paris lilies, but not in spider lilies. This is the first report of S. rolfsii infection in lily in Indonesia.


Sign in / Sign up

Export Citation Format

Share Document