scholarly journals First Report of Pythium torulosum Causing Corn Root Rot in Northeastern China

Plant Disease ◽  
2020 ◽  
Author(s):  
Xiujun Tang ◽  
Shuning Chen ◽  
Xiaojing Yan ◽  
Huizhu Yuan ◽  
Daibin Yang
Keyword(s):  
Root Rot ◽  
Petri Dish ◽  
Soil Samples ◽  
Northeastern China ◽  
Growth Chamber ◽  
Corn Root ◽  
First Report ◽  
Corn Root Rot ◽  
Soil Mix ◽  
Pythium Torulosum

In October 2017, we collected five soil samples from each of several fields with a history of severe corn (Zea mays) seedling disease in Heilongjiang province of China. Affected seedlings were wilted with severe root rot, and a high incidence of seedling death was observed in the fields. Corn seeds were seeded in the collected soil samples and grown in a growth chamber for 21 days set at the following incubation temperatures: 21℃/7℃ for 6 days, 10℃/3℃ for 4 days, 16℃/7℃ for 5 days, 20℃/20℃ for 6 days (16 h/8 h, light/dark) (Tang et al. 2019). The corn seedlings in the growth chamber showed the same symptoms observed in the field as mentioned above. Corn root rot samples were collected from several symptomatic plants in the growth chamber to isolate the possible pathogen. Symptomatic roots were washed in 0.5% NaOCl for 2 min, rinsed in sterile water and cut into 1-2 mm segments and then plated on corn meal agar amended with pimaricin (5 μg/ml), ampicillin (250 μg/ml), rifampicin (10 μg/ml), pentachloronitrobenzene (50 μg/ml), and benomyl (10 μg/ml) (PARP+B), which is selective for oomycetes (Jeffers and Martin 1986). After 3 days of incubation in the dark at 25℃, colonies were transferred to 10% V8 juice agar and incubated at 25℃ for 2 weeks. Six isolates were identified as Pythium torulosum based on the morphology of sexual and asexual structures following van der Plaats-Niterink’s key (van der Plaats-Niterink 1981). On 10% V8 juice agar, the hypha were aseptate and colonies had filamentous sporangia with a dendroid or globose structure. The oogonia were globose or subglobose, laevis, terminal, rarely intercalary, ranging from 12-19 (average 16) μm. Antheridia were mostly sessile or brachypodous, and each oogonium was supplied by 1-2 antheridia cells. Oospores were globose, plerotic, ranging from 9-16 (average 13) μm. For the molecular identification, two molecular targets, the internal transcribed spacer (ITS) region of ribosomal DNA and cytochrome c oxidase subunit II (CoII), were amplified and sequenced using universal primer sets DC6/ITS4 (Cooke et al. 2000) and FM58/FM66 (Villa et al. 2006), respectively for one isolate, “copt”. BLAST analyses of a 971 bp ITS segment amplified from copt (GenBank Accession No. MT830918) showed 99.79% identity with a P. torulosum isolate (GenBank Accession No. AY598624.2). For the COⅡ gene of copt, BLAST analyses of a 553 bp segment (GenBank Accession MT843570) showed 98.37% identity with P. torulosum isolate (GenBank Accession No. AB095065.1). Thus, the isolate, copt, was identified as P. torulosum based on morphological characteristics and molecular analysis. To confirm pathogenicity and Koch’s postulates, a pathogenicity test was conducted as described by Zhang et al. (2000). Briefly, a 5 mm culture plug from the P. torulosum isolate, copt, was transferred to a 9-cm petri dish containing 20mL 10% V8 juice agar and incubated in the dark at 25℃ for 7 days. The culture was cut into small pieces and mixed with a sterilized soil mix (40% organic peat substrate, 40% perlite, and 20% soil) at a ratio of one petri dish per 100 g soil mix. Ten corn seeds were planted at a depth of 2 cm in a 500-mL pot containing the inoculated soil mix. The control pots were mock inoculated with plain 10% V8 juice agar. Pots were incubated in a greenhouse at temperatures ranging from 21 to 23℃. There were four replications. After 14 days, corn roots brown and rotted were observed, which was similar to those observed in the field and growth chamber. Control plants remained symptomless and healthy. P. torulosum copt was consistently re-isolated from the symptomatic roots. To our knowledge, this is the first report of P. torulosum causing root rot of corn in Northeastern China. Corn is an important crop in Heilongjiang and the occurrence of root rot caused by this pathogen may be a new threat to corn plants. There is a need to develop management measures to control the disease.

scholarly journals First Report of Pythium sylvaticum Causing Corn Root Rot in Northeastern China

Plant Disease ◽  
2021 ◽  
Vol 105 (1) ◽  
pp. 231
Author(s):  
Xiujun Tang ◽  
Shuning Chen ◽  
Xiaojing Yan ◽  
Huizhu Yuan ◽  
Daibin Yang
Keyword(s):  
Root Rot ◽  
Northeastern China ◽  
Corn Root ◽  
First Report ◽  
Pythium Sylvaticum ◽  
Corn Root Rot

scholarly journals Aphanomyces euteiches Race 2 in Central Illinois Alfalfa Fields

Plant Disease ◽  
2002 ◽  
Vol 86 (5) ◽  
pp. 560-560 ◽  
Author(s):  
D. Malvick
Keyword(s):  
Root Rot ◽  
Soil Samples ◽  
Disease Index ◽  
Growth Chamber ◽  
Aphanomyces Euteiches ◽  
First Report ◽  
Dead Plant ◽  
Race 2 ◽  
Central Illinois

Approximately 260,000 ha of alfalfa is grown in Illinois. Two soil samples were collected randomly from slowly drained thin patches in each of four established alfalfa fields near Urbana in 2001. Plants in the thin patches were asymptomatic. Aphanomyces euteiches Drechs. was baited from the soil with cv. Saranac alfalfa seedlings and was isolated from 3- to 4-week-old infected seedlings using a medium containing metalaxyl and benomyl (1,2). It is difficult to isolate A. euteiches from field-grown roots. One to seven isolates were obtained per field, and all were identified as A. euteiches based on morphology (1,2). A. euteiches (races R1 and R2) causes root rot of alfalfa in slowly drained fields in Iowa, Kentucky, and Wisconsin (1,2). The race of 13 isolates was determined in tests repeated once with alfalfa populations Saranac (susceptible to R1 and R2), WAPH-1 (resistant only to R1), and WAPH-5 (resistant to R1 and R2) (1). Twelve 7-day-old seedlings in each of three pots per population were inoculated with 103 zoospores per seedling in a growth chamber (25°C). A disease index (DI) was determined 12 days later by scoring plants on a 1 to 5 scale, where 5 is a dead plant (1). Race was based on DI, R1: DI ≥3 for Saranac and <3 for WAPH-1, and R2: DI > 3 for Saranac and WAPH-1. The DI was 1.0 for noninoculated plants. All isolates were R2; the DI was >3.0 for inoculated Saranac and WAPH-1 and <3.0 for WAPH-5. To our knowledge, this is the first report of A. euteiches races in Illinois, and this pathogen was reported previously only from northwest Illinois. Control of Aphanomyces root rot is based on resistance; however, few alfalfa cultivars are resistant to R2. References: (1) D. Malvick and C. Grau. Plant Dis. 85:740, 2001. (2) G. Munkvold and W. Carlton. Plant Dis. 79:1251,1995.

scholarly journals First Report of Root Rot Caused by Pythium aphanidermatum on Bell Pepper (Capsicum annuum L.) in Italy

Plant Disease ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 854-854 ◽  
Author(s):  
A. Garibaldi ◽  
G. Gilardi ◽  
G. Ortu ◽  
M. L. Gullino
Keyword(s):  
Capsicum Annuum ◽  
Root Rot ◽  
Agar Medium ◽  
The United States ◽  
Pythium Aphanidermatum ◽  
Northern Italy ◽  
Bell Pepper ◽  
Growth Chamber ◽  
Sodium Hypochlorite Solution ◽  
First Report

During July 2012, symptoms of root rot were observed on bell pepper (Capsicum annuum) grown in 2,000 m2 of commercial greenhouses near Cuneo in northern Italy. Symptoms first developed 30 to 40 days after transplanting, when greenhouse temperatures ranged from 25 to 30°C, and 10% of the plants were affected. Affected plants were stunted with leaf chlorosis, reduced growth, and sudden wilting. Roots were severely affected with a brown discoloration, water-soaking, and soft rot. Eventually, affected plants collapsed. Tissue fragments of 1 mm2 were excised from symptomatic roots, dipped in a 1% sodium hypochlorite solution, and placed on potato dextrose agar (PDA) and an agar medium selective for oomycetes (3). Plates were incubated under constant fluorescent light at 22 ± 1°C for 5 days. An isolate grown for 12 days on V8 agar medium (200 ml V8 Campbell Soup, 15 g agar, 0.5 g CaCO3, and 1 liter distilled water) showed aseptate hyphae that were 3.5 to 6.3 μm (avg. 5.2 μm) wide. Oogonia were globose, smooth, and 24.3 to 29.0 (avg. 25.1) μm in diameter. Antheridia were barrel-shaped, while oospores were globose, and 17.3 to 23.5 μm (avg. 21.2 μm) in diameter. These morphological characters identified the microorganism as a Pythium sp. (4). The ITS region of rDNA of a single isolate was amplified using the primers ITS1/ITS4 and sequenced. BLAST analysis (1) of the 781-bp segment (GenBank Accession KF840479) showed 100% homology with the ITS sequence of an isolate of Pythium aphanidermatum in GenBank (AY598622.2). Pathogenicity tests were performed twice on 30-day-old plants of C. annuum cv. Cuneo grown in 2-L pots (4 plants/pot), containing a steam-disinfested, organic peat substrate (70% black peat and 30% white peat, pH 5.5 to 6.0, N 110 to 190 mg/liter, P2O5 140 to 230 mg/liter, K2O 170 to 280 mg/liter) that was infested with wheat and hemp kernels colonized by the isolate of P. aphanidermatum, at a rate of 1 g colonized kernels/liter potting medium. The inoculum was prepared by autoclaving at 121°C for 30 min a mixture of wheat-hemp kernels (2:1 v/v) in a 1-liter flask, to which the bell pepper isolate of P. aphanidermatum was added in the form of colonized agar medium selective for oomycetes plugs. Before use, the inoculated flask was incubated for 10 days at 22°C in the dark. Four plants/pot were transplanted into each of four pots filled with the infested medium/growth chamber, while the same number of plants were grown in non-infested substrate in pots in each growth chamber. Plants were kept in two growth chambers, one set at 20°C and the other at 28°C. Symptoms first developed 7 days after inoculation. After 30 days, 50% of inoculated plants showed brown roots and died in the growth chamber set at 28°C, while only 10% of the plants were symptomatic at 20°C. Control plants remained asymptomatic at both temperatures. P. aphanidermatum was re-isolated consistently from the symptomatic roots of plants grown in the infested soil by using the same protocol as the original isolations, while no fungal colonies were obtained from asymptomatic roots of the non-inoculated control plants. To our knowledge, this is the first report of the presence of P. aphanidermatum on C. annuum in Italy. The same disease was reported in the United States (2). The importance of the disease, although limited in distribution at present to the greenhouses surveyed in northern Italy, could increase in areas where sweet pepper is grown intensively. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. O. Chellemi et al. Plant Dis. 84:1271, 2000. (3) H. Masago et al. Phytopathology 67:425, 1977. (4) T. Watanabe. Pictorial Atlas of Soil and Seed Fungi. CRC Press, Boca Raton, FL, 2002.

scholarly journals Features of allelopathy between fusarium species and concomitant Trichoderma longibrachiatum in the maize rhizosphere in Kuban

2021 ◽  
pp. 41-44
Author(s):  
Viktor Petrovich Sokirko ◽  
Elena Vladimirovna Eliseeva ◽  
Eric Nshirimana ◽  
Anastsiya Ivanovna Dmitrenko
Keyword(s):  
Root Rot ◽  
Agricultural Sector ◽  
Fusarium Species ◽  
Fold Increase ◽  
Northern Region ◽  
Pcr Analysis ◽  
Corn Root ◽  
Significant Damage ◽  
Corn Root Rot ◽  
The Relationship

The purpose of these studies was to study the interaction of pathogens of corn root rot in the agricultural sector of the Northern region of Krasnodar region. Corn root rot in the agricultural farms of the region annually cause significant damage to the harvest of silage and corn grain. In the course of research, the biological feature of the relationship between two species of the genus Fusarium: Fusarium concentricum Nirenberg & O'donnell and Fusarium proliferatum Matsush., optimizing the five-fold increase in the first species of mushroom compared to the growth of the second. PCR analysis revealed Fusarium oxysporum strain IMI 58289 with increased ability to exhibit elements of aggressive synergism. These fungi belong to the Department Ascomycota, order Hypocreales. In the soil of the studied rhizosphere, a natural hyperparasite – Trichoderma was detected, which can be used to minimize Fusarium infection.

scholarly journals Occurrence of Sclerotinia sclerotiorum causing Sclerotinia root rot on American ginseng in northeastern China

Plant Disease ◽  
2021 ◽  
Author(s):  
Yi Ming Guan ◽  
Ying Ying Ma ◽  
Lin Lin Zhang ◽  
Xiao Xi Pan ◽  
Ning Liu ◽  
...  
Keyword(s):  
Root Rot ◽  
Management Strategies ◽  
Its Region ◽  
Petri Dish ◽  
American Ginseng ◽  
Northeastern China ◽  
Protease Gene ◽  
Aspartyl Protease ◽  
Panax Quinquefolium ◽  
Sorghum Grain

American ginseng (Panax quinquefolium) is a valuable medicinal plant that is commercially cultivated in China. In May 2020, Sclerotinia root rot of American ginseng was observed on 4-year-old plants in Fusong County in northeastern China, which is the most important part of the country for American ginseng cultivation. The pathogen only infected the tuberous ginseng roots, with sclerotia tightly attached to the root surface. Infected roots, which were brownish and had a watery soft rotted appearance (Fig. 1), eventually became hollow and filled with sclerotia. There were no significant changes to the aboveground plant parts during the initial infection stage, but as the disease progressed, the foliage became discolored and wilted because of the damaged roots. More than 31% of the plants in a 30-ha field were infected. Symptomatic roots were collected and sclerotia were removed from the diseased tissue, immersed in 1% NaClO for 1 min, rinsed three times with sterile water, and placed on acidified potato dextrose agar (PDA) in Petri dishes. After an incubation in darkness at 20 °C for 2–3 days, 21 suspected Sclerotinia isolates were obtained. Isolates JH1 and JH2 were randomly selected for identification. On PDA, colonies produced sparse, white, and cottony aerial mycelia (i.e., wool-like appearance), with septate, branched, and hyaline hyphae. Within 4 days of incubation, the PDA surface was covered with white hyphae. Small and white sclerotial primordia formed 3 days later and were irregularly distributed in the middle and along the edge of the Petri dish. After maturing, the hardened and black sclerotia had an irregular shape and size, ranging from 1.4 × 1.5 to 4.1 × 7.5 mm (n = 50). Most of the sclerotia developed separately, with approximately 15–25 per plate (Fig. 2). On the basis of their morphology, the isolates were initially identified as Sclerotinia sp. (Mordue and Holliday 1976; Kohn 1979). Using the JH1 and JH2 rDNA internal transcribed spacer (ITS) region (GenBank accession no. MZ031405 and MZ031406) and the aspartyl protease gene specific to S. sclerotiorum (MZ292709 and MZ292710) in GenBank as queries, BLAST searches revealed that the sequences were respectively 99%–100% similar to S. sclerotiorum sequences KF859933 and AF271387. The primer pairs for amplifying the ITS region and the aspartyl protease gene were respectively ITS4/ITS5 (White et al. 1990) and SSaspr F/SSaspr R (Abd-Elmagid et al. 2013). The pathogenicity of JH1 and JH2 was evaluated using healthy plants. The roots of 4-year-old ginseng plants were washed, wiped with 75% alcohol, and transferred to flower pots containing sterile sand and sorghum grain (10:1 v/v) infested with 10-day-old isolates. For both isolates, 12 plants were inoculated, with four plants per pot. Control plants were transferred to flower pots containing sorghum grain lacking fungus. The inoculated samples were incubated in a greenhouse (12 h photoperiod and 25 °C) for 25 days before they were examined. The test was repeated twice. The inoculated roots exhibited the same symptoms as those observed in the field, whereas the controls remained symptomless. The same fungus was reisolated from all infected roots and resequencing results confirmed its identity. To the best of our knowledge, this is the first report of S. sclerotiorum causing Sclerotinia root rot on American ginseng in China. Because this disease is detrimental to the production of American ginseng, effective management strategies will need to be developed.

Interaction ofpra tylenchus scribneri and helminthosporium pedicellatum in the etiology of corn root rot

1986 ◽  
Vol 14 (4) ◽  
pp. 287-295 ◽  
Author(s):  
OLufunke A. Egunjobi ◽  
D. C. Norton ◽  
C. Martinson
Keyword(s):  
Root Rot ◽  
Corn Root ◽  
Corn Root Rot

scholarly journals First Report of Brown Root Rot of Alfalfa Caused by Phoma sclerotioides in Wisconsin

Plant Disease ◽  
2004 ◽  
Vol 88 (7) ◽  
pp. 769-769 ◽  
Author(s):  
R. C. Larsen ◽  
C. R. Grau ◽  
G. J. Vandemark ◽  
T. J. Hughes ◽  
B. D. Hudelson
Keyword(s):  
United States ◽  
Root Rot ◽  
Lateral Roots ◽  
The United States ◽  
Soil Samples ◽  
Soil Extraction ◽  
Soil Dna ◽  
First Report ◽  
Phoma Sclerotioides ◽  
Brown Root Rot

Brown root rot (BRR) has been associated with winterkill of alfalfa (Medicago sativa L.) in the temperate regions of North America where winters are severe (1). Although suspected, BRR has not been associated with winterkill of alfalfa in the upper Midwestern United States. Alfalfa plants exhibiting symptoms resembling those induced by the causal agent Phoma sclerotioides G. Preuss ex Sacc. were collected from fields in Marinette, Pierce, and Marathon counties in Wisconsin during the spring and early summer of 2003. Symptoms included stunting and decline in 1- to 3-year-old plants that were slow to break dormancy in the early spring. Roots frequently exhibited dark brown lesions or were entirely decayed. Advanced lesions often formed dark bands around the circumference of tap and secondary roots. Beaked pycnidial structures typical of P. sclerotioides were also observed on many samples with advanced lesions. Plants with symptoms of BRR were also observed in Clark, Langlade, Lincoln, Oconto, Shawno, Taylor, and Wood counties. Several lesion areas of tissue on the tap and lateral roots of each sample were excised with a sterile scalpel. Total DNA was extracted using the Fast DNA kit (Bio 101, Carlsbad, CA). In addition, soil samples were collected in the root rhizosphere of symptomatic plants from four fields in two counties. Soil DNA was extracted with the Ultra-Clean DNA soil extraction kit (Mo Bio, Solana Beach, CA). DNA extractions were diluted 1:10 or 1:50, and samples were evaluated for the presence of P. sclerotioides using polymerase chain reaction (PCR)-based sequence-characterized amplified region (SCAR) markers according to the method described previously (4). Amplicons of the expected size (499 bp) were detected from alfalfa roots sampled from Marathon (4 of 4), Marinette (4 of 5), and Pierce (4 of 4) counties but not in roots from healthy controls produced in the greenhouse at Prosser, WA. PCR amplicons were also produced from all field soil samples in Marathon and Marinette counties. Proof of pathogenicity via Koch's postulates for this host-pathogen system was not attempted because of the extensive time period required (1). However, characteristic beaked pycnidia were present, and the pathogen was identified using PCR on DNA from roots symptomatic of BRR. Detection of BRR has been limited in the United States to Wyoming (2), but has been thought to occur in other states with severe winters (3). To our knowledge, this is the first report of P. sclerotioides in Wisconsin. References: (1) J. G. N. Davidson. Brown root rot. Pages 29–31 in: Compendium of Alfalfa Diseases. 2nd ed. D. L. Stuteville and D. C. Erwin, eds. The American Phytopathological Society, St. Paul, MN, 1990. (2) F. A. Gray et al. Pages 27–28 in: Proc. 10th Western Alfalfa Improv. Conf., 1997. (3) C. R. Hollingsworth et al. Can. J Plant Pathol. 25:215, 2003. (4) R. C. Larsen et al. Plant Dis. 86:928, 2002.

STUDIES ON ROOT ROT OF CORN IN ONTARIO

1942 ◽  
Vol 20c (4) ◽  
pp. 241-256 ◽  
Author(s):  
J. K. Richardson
Keyword(s):  
Cover Crops ◽  
Root Rot ◽  
Severe Damage ◽  
Corn Root ◽  
Field Crops ◽  
Soil Temperatures ◽  
Severity Of The Disease ◽  
Corn Root Rot ◽  
Micro Organisms ◽  
Intermediate Effect

Root rot of corn in Ontario is caused primarily by parasitic soil micro-organisms, the most important of which are species of Pythium, Helminthosporium, and Fusarium in that order. The disease causes a decrease in the stand by pre-emergence killing and a dwarfing of the plants by the parasitic invasion and destruction of their roots by the organisms. The pathogens have different optimum soil temperatures but the lower ranges favour those that cause the most severe damage. The roots of other field crops can be parasitized by the organisms found associated with corn root rot, but their effect on the development of the crop varies greatly. It has been proved under greenhouse conditions that the severity of the disease is greatly reduced if the corn is preceded by cover crops of soybeans and materially increased when preceded by timothy. Other crops tested have an intermediate effect.

scholarly journals First Report of Aphanomyces euteiches Race 1 and Race 2 Causing Aphanomyces Root Rot on Alfalfa (Medicago sativa) in South Dakota

Plant Disease ◽  
2021 ◽  
Author(s):  
Conner L. Tordsen ◽  
Jennifer M. Giles ◽  
Andrew Edward Sathoff
Keyword(s):  
South Dakota ◽  
Medicago Sativa ◽  
Root Rot ◽  
Severity Index ◽  
The United States ◽  
Soil Samples ◽  
Aphanomyces Euteiches ◽  
Specific Primers ◽  
Lake County ◽  
First Report

Aphanomyces euteiches causes Aphanomyces root rot (ARR) in alfalfa (Medicago sativa), along with root rot on many other legumes, including pea, clover, and lentil (Malvick et al., 2009). In 2020, South Dakota (SD) planted the most acres of alfalfa in the United States, which demonstrates the importance of alfalfa to the state. Several SD growers reported alfalfa establishment problems likely to be associated with ARR. Soil samples were collected from 16 fields under commercial alfalfa production in Lake County, SD in June 2020. Composite soil samples based on 24 subsamples were collected in a W-shaped pattern at a depth of 15 cm. Collected soil was sieved, and 80 cm3 was placed in plastic pots (6 cm x 6 cm). Each pot was planted with 25 seeds, covered with an additional 15 cm3 soil, and placed in a growth chamber with a 16-hour photoperiod at temperatures of 24 and 19 ℃ (day and night). Alfalfa seedlings, including Saranac (susceptible to races R1 and R2), WAPH-1 (resistant only to R1), WAPH-5 (resistant to both R1 and R2), and Mustang 625 (resistant to both R1 and R2 and coated with mefenoxam) grew in collected soil for 7 days, followed by 4 days under flooded conditions. Trays were drained, and at 21 days after planting (DAP), roots were removed from soil, washed in distilled water, and rated to measure severity of disease symptoms (Samac et al., 2015). The average severity index (ASI) used a 1-5 disease severity scale, 5 being a dead plant and 1 being no symptoms present (http://www.naaic.org/stdtests/Aphano.html). Race was based on ASI where R1 included an ASI of ≥3 for Saranac and <3 for WAPH-1, and R2 included an ASI of >3.0 for Saranac and WAPH-1 and <3.0 for WAPH-5 (Malvick and Grau, 2001). Race-typing experiments were repeated twice with six replicate pots per alfalfa cultivar per experiment and determined the presence of both R1 and R2 in Lake County, SD. ASI values for Mustang 625 and WAPH-5 were similar across all fields evaluated, which indicates limited confounding effects of other root rotting pathogens. DNA was extracted from three symptomatic roots from each field and was PCR amplified using A. euteiches specific primers (Vandemark et al., 2002). A PCR product was observed in all 16 fields evaluated, and the absence of a product was observed when DNA was extracted from alfalfa roots grown in vermiculite. Following race-typing, infected alfalfa roots were surfaced sterilized and placed on Aphanomyces selective media consisting of mefenoxam and benomyl in cornmeal agar (CMA) (Pfender et al., 1984). Isolates were identified as A. euteiches based on hyphal morphology (Malvick and Grau, 2001). Alfalfa seedlings (Saranac) were grown in vermiculite under growth conditions used for the race-typing assay and inoculated 6 DAP with two isolates of A. euteiches. Inoculation was completed using half plates of one week old A. euteiches mycelium on CMA blended with one liter of water (Samac et al., 2015). At 35 DAP, control alfalfa seedlings inoculated with blended CMA and water remained asymptomatic, and alfalfa infected with A. euteiches displayed symptoms including honey-brown colored lesions. For confirmation of Koch’s postulates, DNA from three re-infected seedlings was again PCR amplified using A. euteiches specific primers and confirmed our previous work. This is the first report of either R1 or R2 of A. euteiches causing ARR on alfalfa in SD. To avoid future yield loss, SD growers should consider planting available alfalfa cultivars that have resistance to both races of A. euteiches.

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