Aphanomyces Root Rot on Sugar Beet

Spatial distribution of Aphanomyces cochlioides inoculum and disease was assessed in sugar beet fields located near Moorhead, MN and Wahpeton, ND. Soil samples were collected in June and July 1994 from two main plots (60 by 60 m) in each field. Samples were evaluated for A. cochlioides using a sugar beet seedling assay in the greenhouse to determine a root rot index value (0-to-100 scale), which served as an indirect estimate of relative activity and density of inoculum. Field evaluations of Aphanomyces root rot on sugar beet (0-to-7 scale) were made at harvest in September at each soil collection site. Greenhouse root rot index values correlated positively with field disease ratings for all plots. Variance-to-mean ratios of greenhouse root rot index values and of field disease ratings among samples within each plot were calculated to compare the spatial distribution of midseason inoculum with root rot at harvest. Ratios of greenhouse root rot indices indicated that inoculum of A. cochlioides was aggregated in the field at midseason, but root rot was uniform within plots by harvest. Wet weather in July through August was conducive to infection and development of symptoms. A uniform distribution of disease at harvest likely reflects a combination of factors, including root growth into inoculum foci, redistribution of inoculum, and inoculum densities that are spatially variable but all above some minimum threshold for infection.

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Quantitative trait locus responsible for resistance to Aphanomyces root rot (black root) caused by Aphanomyces cochlioides Drechs. in sugar beet

Theoretical and Applied Genetics ◽

10.1007/s00122-008-0891-3 ◽

2008 ◽

Vol 118 (2) ◽

pp. 227-234 ◽

Cited By ~ 9

Author(s):

Kazunori Taguchi ◽

Naoki Ogata ◽

Tomohiko Kubo ◽

Shinji Kawasaki ◽

Tetsuo Mikami

Keyword(s):

Quantitative Trait Locus ◽

Sugar Beet ◽

Quantitative Trait ◽

Root Rot ◽

Aphanomyces Cochlioides ◽

Trait Locus

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Effects of Aphanomyces Root Rot on Carbohydrate Impurities and Sucrose Extractability in Postharvest Sugar Beet

Plant Disease ◽

10.1094/pdis-93-1-0094 ◽

2009 ◽

Vol 93 (1) ◽

pp. 94-99 ◽

Cited By ~ 4

Author(s):

Karen L. Klotz ◽

Larry G. Campbell

Keyword(s):

Sugar Beet ◽

Disease Severity ◽

Root Rot ◽

Severe Infection ◽

Storage Duration ◽

Disease Symptoms ◽

Aphanomyces Cochlioides ◽

Duration Of Storage ◽

Elevated Glucose ◽

Processing Properties

Sugar beet (Beta vulgaris) roots with rot caused by Aphanomyces cochlioides often are incorporated into storage piles even though effects of disease on processing properties are unknown. Roots with Aphanomyces root rot were harvested from six fields over 2 years. For each field, roots with similar disease symptoms were combined and assigned a root rot index (RRI) value (0 to 100; 0, no rot symptoms; 100, all roots severely rotted). After 20 or 120 days storage at 4°C and 95% relative humidity, concentrations of the major carbohydrate impurities that accumulate during storage and sucrose extractability were determined. Root rot affected carbohydrate impurity concentrations and sucrose extractability in direct relation to disease severity symptoms. Generally, roots with active and severe infection (RRI ≥ 85) exhibited elevated glucose and fructose concentrations 20 and 120 days after harvest (DAH), elevated raffinose concentration 120 DAH, and reduced sucrose extractability 20 and 120 DAH. Roots with minor or moderate disease symptoms (RRI 20 to 69), or damaged roots with no signs of active infection, had similar carbohydrate impurity concentrations and sucrose extractability after 20 and 120 days storage. Processing properties declined when RRIs exceeded 43, as determined by regression analysis, or when storage duration increased from 20 to 120 days. Results indicate that both disease severity and anticipated duration of storage be considered before Aphanomyces-infected roots are incorporated into storage piles.

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A reference genome sequence resource for the sugar beet root rot pathogen Aphanomyces cochlioides

10.1101/2021.08.11.456025 ◽

2021 ◽

Author(s):

Jacob Botkin ◽

Ashok K Chanda ◽

Frank N Martin ◽

Cory D Hirsch

Keyword(s):

Sugar Beet ◽

Genome Assembly ◽

Root Rot ◽

De Novo ◽

Sequence Data ◽

Aphanomyces Cochlioides ◽

Beet Root ◽

Long Read ◽

Illumina Sequence ◽

Sugar Beet Root

Aphanomyces cochlioides, the causal agent of damping-off and root rot of sugar beet (Beta vulgaris L.), is a soil-dwelling oomycete responsible for yield losses in all major sugar beet growing regions. Currently, genomic resources for A. cochlioides are limited. Here we report a de novo genome assembly using a combination of long-read MinION (Oxford Nanopore Technologies) and short-read Illumina sequence data for A. cochlioides isolate 103-1, from Breckenridge, MN. The assembled genome was 76.3 Mb, with a contig N50 of 2.6 Mb. The reference assembly was annotated and was composed of 32.1% repetitive elements and 20,274 gene models. This high-quality genome assembly of A. cochlioides will be a valuable resource for understanding genetic variation, virulence factors, and comparative genomics of this important sugar beet pathogen.

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First Report of Aphanomyces Root Rot of Sugar Beet in Nebraska and Wyoming

Plant Disease ◽

10.1094/pdis.2000.84.5.596b ◽

2000 ◽

Vol 84 (5) ◽

pp. 596-596 ◽

Cited By ~ 3

Author(s):

R. M. Harveson

Keyword(s):

Sugar Beet ◽

Beta Vulgaris ◽

Root Rot ◽

Causal Agent ◽

High Plains ◽

Sugar Beets ◽

Koch’S Postulates ◽

First Report ◽

Aphanomyces Cochlioides ◽

Central High

Sugar beet (Beta vulgaris L.) plants exhibiting dull green and chlorotic foliage were first observed in a field near Dalton, NE, in late July 1999. Root symptoms included distal tip rot with internal, yellow-brown, water-soaked tissues. Isolations on MBV medium (1) consistently yielded Aphanomyces cochlioides Drechs. Water cultures produced primary zoospores that encysted at the tips of sporangiophores, followed by release of secondary zoospores within 12 h. Seedlings inoculated with zoospores began to die 2 weeks after emergence in a greenhouse. Symptoms on hypocotyls began as water-soaked lesions that turned black and thread-like. The causal agent was reisolated from infected seedlings, completing Koch's postulates. The disease was subsequently found in more than 15 separate fields, representing 5 of 11 sugar beet-growing counties in Nebraska and 1 county in Wyoming. In October, plants from the same fields were observed with stunted, distorted roots and superficial, scabby lesions associated with latent A. cochlioides infection. The pathogen could not be isolated from this stage but was confirmed by observing mature oospores within thin, stained sections under a microscope. The sections were additionally mixed with sterile potting soil and planted in the greenhouse with sugar beets. Several weeks after emergence, seedlings began to die, and the pathogen was reisolated. This represents the first report of Aphanomyces root rot and its spread in the Central High Plains. It also confirms that the described latent symptoms on sugar beet are caused by A. cochlioides. Reference: (1). W. F. Pfender et al. Plant Dis. 68:845, 1984.

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Differentiation of the disease caused by Aphanomyces cochlioides and girth scab on sugar beet roots – a review

Plant Protection Science ◽

10.17221/152/2015-pps ◽

2016 ◽

Vol 53 (No. 2) ◽

pp. 71-77

Author(s):

Moliszewska Eva B

Keyword(s):

Sugar Beet ◽

Root Rot ◽

Weather Conditions ◽

Seedling Stage ◽

Aphanomyces Cochlioides ◽

Streptomyces Spp ◽

Current Classification ◽

Further Development ◽

Rainfall Level

Severe symptoms of root rot on sugar beet have been observed in Poland and Germany since 2001. The symptom classification suggested girth scab as it was mistakenly classified on the basis of current classification, e.g. in LIZ. However, the cause of the disease was Aphanomyces cochlioides infection, not Streptomyces spp. According to these findings we cannot call the symptoms caused by A. cochlioides as ‘girth scab’. The typical scab (girth scab) symptoms can be promoted by A. cochlioides infections. In many cases, A. cochlioides developed at the beginning of the season, during the seedling stage. Its further development was due to rainfall and was not routinely recognised in disease-changed tissues if in the middle of the summer the rainfall level was reduced. According to the described findings, renewed description and differentiation of the girth scab symptoms caused by Streptomyces spp. and root rot caused by A. cochlioides on sugar beet roots are suggested. Typical symptoms of the disease caused by A. cochlioides occur mainly on the upper part of the root but can also occur on its lower part, if weather conditions are favourable for the pathogen. The coexistence of A. cochlioides and Pythium spp. in the same niches is also possible. Currently the illustrations showing these symptoms are included in the ‘girth scab’ descriptions.

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Occurrence and importance of root rots caused by fungal pathogens on sugar beet grown in Konya province of Turkey

Sugar Industry ◽

10.36961/si25276 ◽

2020 ◽

pp. 674-681

Author(s):

Rıza Kaya ◽

Meltem Avan ◽

Cemre Aksoy ◽

Fikret Demirci ◽

Yakup Zekai Katircioğlu ◽

...

Keyword(s):

Sugar Beet ◽

Rhizoctonia Solani ◽

Root Rot ◽

Fungal Pathogens ◽

Fusarium Culmorum ◽

Macrophomina Phaseolina ◽

Growth Stages ◽

Aphanomyces Cochlioides ◽

Root Rots ◽

Phytophthora Spp

Sugar beet is extensively grown in Konya province of Turkey and about one third of production of Turkey is obtained from this region. Recently root rots have been observed at all the growth stages of sugar beet especially at later stages near the harvest. During 2015–2017 growing years, 866 fields were visited and diseased samples having root rot symptoms were collected. Various root rot pathogens were isolated from 691 fields; Rhizoctonia solani being the most common (15% of the fields) followed by Fusarium oxysporum, F. solani, Phoma betae, Aphanomyces cochlioides and Pythium spp. Apart from these pathogens, Fusarium culmorum, F. equiseti, F. sambucinum, F. verticillatum, unidentified Fusarium spp., Macrophomina phaseolina and Phytophthora spp. were also determined. All the fungal pathogens were isolated from both of the sugar beet growing stages of 0–12 BBCH and 31–49 BBCH, some of them being high ratios at the late stages. Some isolates of A. cochlioides, P. betae, Pythium spp., Phytophthora spp., and R. solani were highly aggressive when tested by a soil inoculum layer technique. Effects of twelve fungicides, in sixteen different combination and rate, on the most virulant and common four pathogens, A. cochlioides P. betae, Py. ultimum var. ultimum, Rhizoctonia solani, were investigated by the same technique. None of the fungicide mixes inhibited all four pathogens. Thiram + metalaxyl + hymexazol + pyraclastrobin mix sufficiently prevented disease development of the first three pathogens but not R. solani.

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