Relationship of Rhizoctonia solani inoculum density to incidence of hypocotyl rot and damping-off in dry beans

1989 ◽  
Vol 35 (12) ◽  
pp. 1132-1140 ◽  
Author(s):  
A. J. L. Phillips
Keyword(s):  
Phaseolus Vulgaris ◽  
Linear Regression ◽  
Rhizoctonia Solani ◽  
Disease Incidence ◽  
Inoculum Density ◽  
Damping Off ◽  
Dry Beans ◽  
Site Model ◽  
Relationship Of

The effect of inoculum density on preemergence disease incidence was described by linear regression. Variations in virulence among 10 isolates formed a continuum. The effect of inoculum density on hypocotyl disease incidence was described by a limiting site model and variations in virulence among the isolates also formed a continuum. The ability of an isolate to cause preemergence disease was not necessarily related to its ability to cause hypocotyl disease. Both saprophytic colonization and preemergence infection arose from propagules in the spermosphere, while depending on the isolate, infection of hypocotyls was from propagules in either the rhizosphere or the rhizoplane. The observed number of hypocotyl lesions was greater than that estimated from the percentage of plants infected. This effect was more pronounced when seeds were sown at 4 than at 1 cm depth.Key words: beans, epidemiology, Phaseolus vulgaris, Rhizoctonia solani.

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 Pengaruh Waktu Inokulasi dan Jumlah Inokulum Terhadap Patogenisitas Phytophthora nicotianae pada Bibit Tembakau

2016 ◽  
Vol 2 (2) ◽  
pp. 75
Author(s):  
Nurul Hidayah ◽  
Titiek Yulianti
Keyword(s):  
Incubation Period ◽  
Disease Incidence ◽  
Inoculum Density ◽  
Phytophthora Nicotianae ◽  
Artificial Inoculation ◽  
Damping Off ◽  
Black Shank ◽  
Plant Variety ◽  
Two Factors ◽  
Screen House

<p>Waktu inokulasi yang tepat serta jumlah inokulum yang digunakan merupakan salah satu faktor yang me-nentukan keberhasilan inokulasi buatan yang lazim dilakukan dalam pengujian ketahanan suatu varietas ter-hadap patogen tertentu. Penelitian ini bertujuan untuk mengetahui waktu inokulasi dan jumlah inokulum Phytophthora nicotianae yang paling efektif untuk dapat menimbulkan gejala penyakit lanas pada bibit tembakau. Penelitian dilaksanakan di laboratorium dan rumah kasa Fitopatologi Balittas, Malang pada bulan Juli Oktober 2006. Metode penelitian menggunakan rancangan acak lengkap (RAL) yang terdiri dari dua faktor, yaitu umur bibit saat inokulasi (faktor I), terdiri dari tiga tingkat yaitu: 1) bibit berumur 5 minggu setelah se-mai (mss), 2) bibit berumur 6 mss dan 3) bibit berumur 7 mss dan jumlah inokulum (faktor II), terdiri dari 4 tingkat yaitu: 1) tanpa inokulum (kontrol), 2) 1.3502.400 zoospora/bibit, 2) 2.7004.800 zoospora/bibit, dan 4) 5.4009.600 zoospora/bibit. Masing-masing kombinasi perlakuan diulang 3 kali. Pengamatan dilaku-kan pada masa inkubasi dan kejadian penyakit. Hasil penelitian menunjukkan bahwa masa inkubasi penyakit dipengaruhi oleh umur bibit saat inokulasi. Bibit yang lebih muda mempunyai masa inkubasi lebih cepat yak-ni 4,5 hari dibandingkan dengan bibit yang lebih tua. Kejadian penyakit tertinggi yaitu sebesar 56,9% terjadi pada saat bibit diinokulasi berumur 5 mss dengan jumlah inokulum 1.3502.400 zoospora/bibit.</p><p> </p><p>Suitable time of inoculation and inoculum density are factors to determine the success of artificial inoculation to evaluate of resistant level of plant variety to pathogen. The aim of this research was to study the appro-priate time of inoculation and inoculum density of Phytophthora nicotianae, the causal agent of black shank and damping off on tobacco seedling. The research was conducted in Phytopathology laboratory and screen house of IToFCRI Malang from July-October 2006. This research was arranged in complete randomized de-sign which consisted two factors and three replicates. The first factor was comprised of three times of ino-culation, and the second was the density of P. nicotianae inoculum. The parameters observed were incuba-tion period and disease incidence. The result showed that the incubation period was affected by the age of seedling when it was inoculated. The younger seedling was more susceptible than the older one. The high disease incidence (56.9%) was reached when the seedling five weeks old and inoculated by inoculum con-tained of 1,3502,400 zoospores/seedling.</p>

scholarly journals First Report of Soybean Seedling Disease caused by Rhizoctonia solani AG-7 in Taiwan

Plant Disease ◽  
2021 ◽  
Author(s):  
Yu-Cheng Lin ◽  
Min-Nan Tseng ◽  
Hao-Xun Chang
Keyword(s):  
Rhizoctonia Solani ◽  
Tap Water ◽  
Disease Incidence ◽  
Soil Surface ◽  
Anastomosis Group ◽  
Damping Off ◽  
Soybean Seedlings ◽  
Fungal Inoculum ◽  
Potential Pathogen ◽  
Causal Pathogen

From August to November 2020, reduced emergence and damping-off of soybean seedlings were observed in two fields (Benzhou and Wandan) in Taiwan. Disease incidence was approximately 40% in Benzhou by field scouting. The roots of damping-off seedlings were brown. Affected seedlings could be easily pulled out from the soil and the lesions on the roots/stem were generally dry and sunken. These symptoms suggested the possibility of Rhizoctonia infection. Soil surrounding symptomatic seedlings were collected to bait the potential pathogen and symptomatic plants were used for pathogen isolation. The diseased tissues were washed with tap water and surface-disinfected with 1% bleach before placing on the Dexon selection medium at 26°C for 2 days (Ko and Hora 1971). Hyphae were transferred to potato dextrose agar (PDA), and a brown colony with brown and irregular-shaped sclerotia grew from 90 out of 99 isolates. The hyphae exhibited typical characteristics of Rhizoctonia solani, including a constriction and a septum near the end of branching hyphae (Ajayi-Oyetunde and Bradely, 2018). Two isolates from Benzhou and two isolates from Wandan were tested for their pathogenicity, and eight surface-disinfected seeds were distributed evenly on the water agar plates covered by 2-day-old mycelia at 25°C in dark for 7 days. All isolates caused cotyledon rot and reduced germination. To verify their pathogenicity in pots, double-sterilized sorghum seeds were inoculated with two strains and incubated at 25°C for 2 weeks to be used as fungal inoculum (Ajayi-Oyetunde and Bradely, 2017). A layer of 15 ml of fungal inoculum was placed 5 cm beneath the soil surface in pots. Four soybean seeds were planted approximately 3 cm above the inoculum in each pot. After two weeks, reddish lesions on the hypocotyls or taproots of all seedlings in the inoculated pots were observed, while seedlings in the control pots inoculated with sterile sorghum seeds remained healthy. The pathogen was re-isolated from lesions and had identical morphology to the original isolates. To characterize the fungal identity, the internal transcribed spacer (ITS) was sequenced using the primers ITS1/ITS4 (Sharon et al., 2006). Using BLASTN in the NCBI database, the sequence (GenBank no. MW410857 and MW410858) showed 100% (639/639 bp) similarity to KF907734 and 99.83% (635/636 bp) similarity to AF354099, both belong to R. solani anastomosis group 7 (AG-7) (Hua et al. 2014; Gonzalez et al. 2001). Phylogenetic analysis comparing sequences with different AGs (Ajayi-Oyetunde and Bradely, 2017) grouped our isolates within the AG-7 clade with a 100% bootstrap confidence. In the anastomosis test, an incompatible zonation and unequal mycelial growth rates were observed when AG-7 isolates were paired with an AG-1 IA isolate. On the other hand, the compatible tuft reaction was observed when two AG-7 isolates were paired, and the compatible merge reaction was observed in the self-pairing tests (Macnish et al. 1997). Accordingly, the molecular and morphological characterizations confirmed the causal pathogen as R. solani AG-7. R. solani AG-7 was first reported on radishes in Japan (Homma et al., 1983), first found on carnation in Taiwan (Lo et al., 1990), and in field soils of various crops but not soybean (Chuang, 1997). It was suggested that Rhizoctonia diseases of soybean may be present in Taiwan, but molecular confirmation was lacking (Anonymus, 1979). As R. solani AG-7 causes diseases of soybean in the US and Japan (Baird et al., 1996), the importance of AG-7 as an endemic pathogen of soybean in Taiwan should be recognized and its prevalence determined as a first step to managing this disease.

scholarly journals Impact of Cellulose-Rich Organic Soil Amendments on Growth Dynamics and Pathogenicity of Rhizoctonia solani

2021 ◽  
Vol 9 (6) ◽  
pp. 1285
Author(s):  
Anna Clocchiatti ◽  
Silja Emilia Hannula ◽  
Muhammad Syamsu Rizaludin ◽  
Maria P. J. Hundscheid ◽  
Paulien J. A. klein klein Gunnewiek ◽  
...  
Keyword(s):  
Rhizoctonia Solani ◽  
Disease Severity ◽  
Disease Incidence ◽  
Pathogenic Fungus ◽  
Pathogenic Fungi ◽  
Paper Pulp ◽  
Damping Off ◽  
Cellulolytic Bacteria ◽  
Arable Soils ◽  
Saprotrophic Fungi

Cellulose-rich amendments stimulate saprotrophic fungi in arable soils. This may increase competitive and antagonistic interactions with root-infecting pathogenic fungi, resulting in lower disease incidence. However, cellulose-rich amendments may also stimulate pathogenic fungi with saprotrophic abilities, thereby increasing plant disease severity. The current study explores these scenarios, with a focus on the pathogenic fungus Rhizoctonia solani. Saprotrophic growth of R. solani on cellulose-rich materials was tested in vitro. This confirmed paper pulp as a highly suitable substrate for R. solani, whereas its performance on wood sawdusts varied with tree species. In two pot experiments, the effects of amendment of R. solani-infected soil with cellulose-rich materials on performance of beetroot seedlings were tested. All deciduous sawdusts and paper pulp stimulated soil fungal biomass, but only oak, elder and beech sawdusts reduced damping-off of beetroot. Oak sawdust amendment gave a consistent stimulation of saprotrophic Sordariomycetes fungi and of seedling performance, independently of the time between amendment and sowing. In contrast, paper pulp caused a short-term increase in R. solani abundance, coinciding with increased disease severity for beet seedlings sown immediately after amendment. However, damping-off of beetroot was reduced if plants were sown two or four weeks after paper pulp amendment. Cellulolytic bacteria, including Cytophagaceae, responded to paper pulp during the first two weeks and may have counteracted further spread of R. solani. The results showed that fungus-stimulating, cellulose-rich amendments have potential to be used for suppression of R. solani. However, such amendments require a careful consideration of material choice and application strategy.

scholarly journals Level of inoculum suitable for studies on the relationship of coffee seedlings and Rhizoctonia solani or Myrothecium roridum

1969 ◽  
Vol 83 (3-4) ◽  
pp. 181-188
Author(s):  
Wanda I. Mercado ◽  
Rocío del P. Rodríguez
Keyword(s):  
Rhizoctonia Solani ◽  
Disease Incidence ◽  
Dry Weight ◽  
Seedling Mortality ◽  
Inoculum Level ◽  
Inoculum Concentration ◽  
Myrothecium Roridum ◽  
Relationship Of ◽  
The Relationship ◽  
Coffea Arabica L

Suitable levels of inoculum of Rhizoctonia solani and Myrothecium roridum for the induction of symptoms in coffee (Coffea arabica L.) seedlings were determined in greenhouse tests based on the percentage of seedling mortality and disease incidence. Best inoculum level for R. solani and M. roridum was 15 and 10%, respectively. Myrothecium roridum was more virulent than R. solani, and thus caused higher mortality of coffee seedlings. For both pathogens, as the inoculum concentration increased, the dry weight of plants decreased. A direct positive relation between incidence of the disease and concentration of the inoculum was detected, it was found that R. solani is more persistent than M. roridum in the inoculated soil.

scholarly journals Controle de Rhizoctonia solani e Fusarium oxysporum f.sp. phaseoli por biopreparados de isolados de Trichoderma spp.

2013 ◽  
Vol 39 (4) ◽  
pp. 258-262 ◽  
Author(s):  
Pedro Paulo Dias ◽  
Ricardo Luis Louro Berbara ◽  
Maria do Carmo de Araújo Fernandes
Keyword(s):  
Phaseolus Vulgaris ◽  
Rhizoctonia Solani ◽  
Fusarium Oxysporum ◽  
Lactuca Sativa ◽  
Damping Off ◽  
Phaseolus Vulgaris L ◽  
Trichoderma Spp ◽  
Lactuca Sativa L

Os experimentos objetivaram avaliar em condições de casa de vegetação o biocontrole dos fitopatógenos Rhizoctonia solani (RS) e Fusarium oxysporum f.sp. phaseoli (FOP) em alface (Lactuca sativa L.) cultivar Regina, e feijão-vagem (Phaseolus vulgaris L.) cultivar Alessa, respectivamente, utilizando como agentes antagonistas, 10 isolados de Trichoderma spp. selecionados em testes in vitro. Foram feitos biopreparados à base de arroz previamente colonizado por isolados de Trichoderma spp. e posteriormente triturados. Para a realização dos testes, os biopreparados foram inoculados previamente na proporção de 10(9) conídios.mL-1, em substrato comercial para produção de mudas. Após sete dias, os patógenos foram introduzidos separadamente em duas concentrações distintas: R. solani na proporção de 144 mg de meio de arroz por kg de substrato e F. oxysporum f.sp. phaseoli inoculado na forma de suspensão contendo 4,75 x 10(6) conídios.mL-1. Avaliou-se a influência dos biopreparados na % de damping-off de pós-emergência em plantas de alface e a severidade de murcha em plantas de feijão-vagem. O biopreparado referente ao isolado T-03 foi o mais eficiente no controle de R. solani em plantas de alface cultivar Regina, por ter reduzido a incidência de damping-off de pós-emergência nessa cultura. Por outro lado, nenhum dos biopreparados apresentou efeito antagonista satisfatório à F. oxysporum f.sp. phaseoli em plantas de feijão-vagem.

scholarly journals The Impact of Herbicides on the Incidence and Development of Rhizoctonia solani-Induced Cotton Seedling Damping-off

Plant Disease ◽  
1998 ◽  
Vol 82 (1) ◽  
pp. 110-113 ◽  
Author(s):  
A. Heydari ◽  
I. J. Misaghi
Keyword(s):  
Field Experiment ◽  
Rhizoctonia Solani ◽  
Field Experiments ◽  
Disease Incidence ◽  
Disease Development ◽  
Damping Off ◽  
Environmental Chamber ◽  
Cotton Seedling ◽  
Disease Progress ◽  
The Impact

The impact of three pre-plant herbicides, trifluralin, pendimethalin and prometryn, on the incidence and the development of Rhizoctonia solani-induced cotton seedling damping-off was investigated in the controlled environmental chamber and in the field. In the controlled environmental chamber experiments, trifluralin, pendimethalin and prometryn were applied to the soil at 1.8, 2.4, and 3.6 μg a.i. g-1 soil, respectively (equivalent to the respective recommended field concentrations of 0.7, 0.9, and 1.3 kg a.i. ha-1). In the controlled environmental chamber experiments, where soil was infested at planting, application of prometryn, but not pendimethalin or trifluralin, to the soil caused a significant (P < 0.05) increase in damping-off incidence. In controlled environmental chamber experiments where soil was infested after emergence, damping-off increased significantly (P < 0.05) in the presence of pendimethalin and prometryn, but not trifluralin. In a field experiment conducted in Safford, Arizona, pre-plant application of pendimethalin or prometryn, but not trifluralin, caused significant (P < 0.05) increases in disease incidence. In another field experiment in Tucson, Arizona, a significant (P < 0.05) increase in disease incidence was observed in plots treated with prometryn, but not in plots treated with pendimethalin or trifluralin. In both controlled environmental chamber and field experiments, application of selected herbicides had significant effects on disease development as judged by the slope of disease progress curves.

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