Chickpea seed rot and damping-off caused by metalaxyl-resistant Pythium ultimum and its management with ethaboxam

Plant Disease ◽  
2020 ◽  
Author(s):  
Moying Wang ◽  
Stephen Van Vleet ◽  
Rebecca McGee ◽  
Timothy Carl Paulitz ◽  
Lyndon D. Porter ◽  
...  
Keyword(s):  
Field Tests ◽  
Pythium Ultimum ◽  
Damping Off ◽  
Fitness Costs ◽  
Seed Treatments ◽  
Dryland Agriculture ◽  
Metalaxyl Resistance ◽  
Resistance Trait ◽  
Seed Rot ◽  
Northern Idaho

Metalaxyl and its isomer mefenoxam have been the primary fungicides used as seed treatments in managing Pythium seed rot and damping-off of chickpea. However, recent outbreaks of seed rot and damping-off of metalaxyl-treated chickpea seeds were found in the dryland agriculture regions of southeastern Washington and northern Idaho. Pythium spp. isolated from rotten seeds and associated soils showed high levels of resistance to metalaxyl. Large proportions (31 to 91%) of Pythium isolates resistant to metalaxyl were detected in areas where severe chickpea damping-off occurred and were observed in commercial chickpea fields over several years. All metalaxyl-resistant isolates were identified as P. ultimum var. ultimum. The metalaxyl resistance trait measured by EC50 values was stable over 10 generations in the absence of metalaxyl, and no observable fitness costs were associated with metalaxyl resistance. Under controlled conditions, metalaxyl treatments failed to protect chickpea seeds from seed rot and damping-off following inoculation with metalaxyl-resistant Pythium isolates. In culture, ethaboxam inhibited mycelial growth of metalaxyl-resistant, as well as metalaxyl-sensitive isolates. Greenhouse and field tests showed that ethaboxam is effective in managing metalaxyl-resistant Pythium. Ethaboxam in combination with metalaxyl is now commonly applied as seed treatments in commercial chickpea production.

scholarly journals The Efficacy of Ethaboxam as a Soybean Seed Treatment Toward Phytophthora, Phytopythium, and Pythium in Ohio

Plant Disease ◽  
2020 ◽  
Vol 104 (5) ◽  
pp. 1421-1432 ◽  
Author(s):  
Kelsey Scott ◽  
Meredith Eyre ◽  
Dair McDuffee ◽  
Anne E. Dorrance
Keyword(s):  
Seed Treatment ◽  
Soybean Seed ◽  
Primary Objective ◽  
Phytophthora Species ◽  
Damping Off ◽  
Seed Treatments ◽  
Seedling Disease ◽  
Seed Decay ◽  
Fungicide Mixtures ◽  
Seed Rot

Phytophthora, Phytopythium, and Pythium species that cause early-season seed decay and pre-emergence and post-emergence damping off of soybean are most commonly managed with seed treatments. The phenylamide fungicides metalaxyl and mefenoxam, and ethaboxam are effective toward some but not all species. The primary objective of this study was to evaluate the efficacy of ethaboxam in fungicide mixtures and compare those with other fungicides as seed treatments to protect soybean against Pythium, Phytopythium, and Phytophthora species in both high-disease field environments and laboratory seed plate assays. The second objective was to evaluate these seed treatment mixtures on cultivars that have varying levels and combinations of resistance to these soilborne pathogens. Five of eight environments received adequate precipitation in the 14 days after planting for high levels of seedling disease development and treatment evaluations. Three environments had significantly greater stands, and three had significantly greater yield when ethaboxam was used in the seed treatment mixture compared with treatments containing metalaxyl or mefenoxam alone. Three fungicide formulations significantly reduced disease severity compared with nontreated in the seed plate assay for 17 species. However, the combination of ethaboxam plus metalaxyl in a mixture was more effective than either fungicide alone against some Pythium and Phytopythium species. Overall, our results indicate that the addition of ethaboxam to a fungicide seed treatment is effective in reducing seed rot caused by these pathogens commonly isolated from soybean in Ohio but that these effects can be masked when cultivars with resistance are planted.

scholarly journals First report of Pythium ultimum causing damping-off of Sugar beet (Beta vulgaris. L) in Montana, USA

Plant Disease ◽  
2020 ◽  
Author(s):  
Mohamed Fizal Khan ◽  
Md. Ehsanul Haque ◽  
Peter Hakk ◽  
Md. Ziaur Rahman Bhuyian ◽  
Yangxi Liu ◽  
...  
Keyword(s):  
Sugar Beet ◽  
Beta Vulgaris ◽  
Pythium Ultimum ◽  
Pathogenicity Test ◽  
Damping Off ◽  
First Report ◽  
Beet Root ◽  
Pcr Products ◽  
Seed Rot ◽  
Sugar Beet Root

Sugar beet (Beta vulgaris L.) is a globally important crop for sugar. In May 2019, sugar beet seedlings were observed with wilting, lodging and a few were dead in Glendive (46.970170, -104.838204), Montana. Symptoms appeared near the soil line as the stem (hypocotyl) turned dark brown to black with characteristic thread-like infections which resembled Pythium damping-off. It affected approximately 10% of the growing seedlings. Diseased sugar beet root tissues were excised with a sterile scalpel and small pieces (10 mm²) were surface sterilized with 70 % ethanol for 30 seconds, rinsed twice with autoclaved water, air-dried and transferred to potato dextrose agar (PDA) media amended with pimaricin-vancomycin-PCNB (Conway, 1985). Four plates were incubated at 25° C in the dark (Masago et al., 1977) and two weeks later white, dense colony was observed (Zhang et al., 2018). The terminal smooth, globose oogonia (average 18.5 µm in diameter) and antheridia (average 14.5 × 9.5 µm) extended below the oogonium were observed via VWR N. A. 0.30 microscope. The morphological features of the four isolates were consistent with Pythium ultimum Trow (Watanabe, 2002). Genomic DNAs (NORGEN BIOTEK CORP, Fungi DNA Isolation Kit #26200) of four isolates were used for polymerase chain reaction (PCR) with the ITS6-ITS7 primers (Taheri et al., 2017). Subsequently, PCR products were flushed by E.Z.N.A ®Cycle Pure Kit, OMEGA and four samples were sent for Sanger sequencing to GenScript (GenScript, Piscataway, NJ). The sequences were identical and submitted to GenBank, NCBI (accession no. MN398593). The NCBI Blast analysis showed 100% sequence homology to Pythium ultimum with the following GenBank accessions; KF181451.1, KF181449.1 and AY598657.2. Pathogenicity test was done on sugar beet with the same isolates in the greenhouse. Two week old, pythium culture was mixed with vermiculite and perlite mixer (PRO-MIX FLX) in the plastic trays (24´´ x 15´´× 3˝), (22 °C, 75% Relaive Humidity). Sterile water (500 ml/each tray) was added in the mixer to provide sufficient moisture. Twenty seeds of cv. Hilleshog 4302 were sown in the tray, and the trays were replicated thrice with inoculated and mock treatments. Plants were watered as needed to maintain adequate soil moisture conducive for plant growth and disease development. Seven days after sowing, 50% and 100% germination was observed in the inoculated and control treatments, respectively. At the beginning of the second week, 30% post-emergence damping-off was observed in the inoculated treatments. Diseased seedlings were gently pulled out from the pots where similar symptoms were observed in the sugar beet seedlings as described previously. No incidence of disease was observed in mock-treated seedlings. Consistent reisolation of Pythium ultimum was morphologically and molecularly confirmed from the diseased seedlings, thus fulfilling Koch’s postulates. Pythium spp identification is prerequisite to develop effective management of pre and post-emergence damping-off. Pythium ultimum was previously reported in Nebraska to cause sugar beet seed rot and pre-emergence damping-off (Harvenson 2006). To our knowledge, this is the first report of Pythium ultimum causing damping-off on sugar beet in the Sidney factory district in Montana.

scholarly journals Greenhouse Evaluation of Seed and Drench Treatments for Organic Management of Soilborne Pathogens of Spinach

Plant Disease ◽  
2009 ◽  
Vol 93 (12) ◽  
pp. 1281-1292 ◽  
Author(s):  
Jaime A. Cummings ◽  
Carol A. Miles ◽  
Lindsey J. du Toit
Keyword(s):  
Seed Treatment ◽  
Pythium Ultimum ◽  
Organic Production ◽  
Compost Tea ◽  
Damping Off ◽  
Seed Treatments ◽  
Greenhouse Study ◽  
Greenhouse Evaluation ◽  
Equivalent Control ◽  
Bacillus Pumilis

The efficacy of 14 seed and drench treatments for control of soilborne damping-off pathogens in organic production of spinach was evaluated in a greenhouse study. The efficacy of each treatment was compared with nontreated seed and seed treated with a conventional fungicide for control of Fusarium oxysporum f. sp. spinaciae, Pythium ultimum, and Rhizoctonia solani. Two experimental seed treatments, GTG I and GTG II (each comprised of a proprietary organic disinfectant and the latter also containing Trichoderma harzianum T22), provided equivalent control to the conventional fungicide, mefenoxam, against P. ultimum in one trial and significant reduction of damping-off in the second trial. Natural II and Natural X (Streptomycete products), and Subtilex (Bacillus subtilis) seed treatments each suppressed damping-off significantly in one of the two trials. For R. solani, GTG I and Natural II seed treatments reduced damping-off as effectively as a drench with the fungicide Terraclor (pentachloronitrobenzene). A soil drench with Prestop (Gliocladium catenulatum) suppressed postemergence wilt caused by F. oxysporum in both trials; a compost tea drench and seed treatment with Yield Shield (Bacillus pumilis) each suppressed postemergence wilt in only one of two trials. GTG I and GTG II significantly increased seed germination compared to nontreated seed. No treatment was effective against all three pathogens, and some treatments exacerbated damping-off.

scholarly journals Pathogenicity of Pythium species causing seed rot and damping-off in soybean under controlled conditions

2012 ◽  
Vol 91 ◽  
pp. 3-10 ◽  
Author(s):  
Lai Wei ◽  
Allen G. Xue ◽  
Elroy R. Cober ◽  
Carolyn Babcock ◽  
Jinxiu Zhang ◽  
...  
Keyword(s):  
Significant Influence ◽  
Pythium Ultimum ◽  
The Other ◽  
Effect Of Temperature ◽  
Pathogenic Species ◽  
Pythium Species ◽  
Damping Off ◽  
Highly Pathogenic ◽  
Seed Rot ◽  
Soybean Plants

Pythium species cause seed rot (SR) and damping-off (DO) in soybean worldwide. In a previous study, a number of Pythium species were isolated from infected soybean plants across Ontario and Quebec, but their comparative pathogenicities to soybean were not examined. In the present research, 24 isolates from eight Pythium spp. were evaluated for their pathogenicity in causing soybean SR and DO in a greenhouse environment. The effect of temperature on the ability of these isolates to cause SR was also studied. There were significant differences among the eight Pythium spp. for both SR and DO. When tested at 25°C, Pythium ultimum was the most pathogenic species, causing 97.0% SR and 46.4% DO, on average, in the two soybean cultivars used. Pythium aphanidermatum was the second most pathogenic species, resulting in 88.5% SR and 41.8% DO. The two species resulted in significantly greater SR and DO than the other six species tested and were considered highly pathogenic. Of the two cultivars used in these trials, ‘Beechwood’ was significantly more susceptible than ‘Nattawa’ to both SR and DO. Temperature had a significant influence on SR caused by Pythium spp. At all four temperatures tested (4°C, 12°C, 20°C and 28°C), P. ultimum was highly pathogenic, while P. arrenomanes, P. coloratum and P. dissotocum were the least pathogenic. The interactions between temperature and Pythium spp. were more pronounced for P. aphanidermatum, which showed an increased percentage of SR with an increase in temperature, and for P. irregulare, P. macrosporum and P. sylvaticum, which showed a decreased percentage of SR with an increase in temperature.

scholarly journals Selection-Based heritability of Resistance to Pythium Ultimum in Safflower

2014 ◽  
Vol 66 (1) ◽  
pp. 109-117
Author(s):  
Elham Nikmanesh ◽  
Mohammadhadi Pahlevani ◽  
Seyed Esmaeil Razavi
Keyword(s):  
Seedling Emergence ◽  
Pythium Ultimum ◽  
Realized Heritability ◽  
Breeding Methods ◽  
Damping Off ◽  
Seed Rot ◽  
Selection For ◽  
Severity Of The Disease ◽  
Germinating Seeds ◽  
Considerable Damage

Abstract Damping-off disease caused by Pythium ultimum can kill both germinating seeds and young seedlings and cause considerable damage in saflower cultivation. An estimation of heritability lets saflower breeders determine the most effective method for improving seedling emergence in soils infected with P. ultimum, the causal agent of seed rot and damping-off. Two cycles of selection were performed to estimate the realized heritability of resistance to the pathogen in five safflower populations. Undamaged seedlings were selected as resistant individuals and were kept to produce seed. The results showed that selection for two consecutive generations increased the emergence of seedlings in Pythium-infected soil from 46 to 53 %. The heritability estimates varied between 1.72 and 77.66 % over the genotypes and environments, in inverse proportion to the severity of the disease. Estimates of heritabilities showed that genes conferring resistance to P. ultimum in safflower are highly heritable and would respond to selection breeding, particularly in some of the studied genotypes, like Isfahan and Zarghan259. However, different breeding methods must be explored for other genotypes.

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