Aphanomyces cochlioides. [Distribution map].

A new distribution map is provided for Aphanomyces cochlioides Drechsler. Peronosporea: Saprolegniales: Leptolegniaceae. Hosts: spinach (Spinacia oleracea), sugar beet (Beta vulgaris), and other members of the Chenopodiaceae and Amaranthaceae. Information is given on the geographical distribution in Africa (Egypt), Asia (Japan, Hokkaido, Turkey), Europe (Austria, Belgium, Bulgaria, Croatia, Denmark, Estonia, France, Germany, Hungary, Ireland, Moldova, Netherlands, Poland, Russia, Spain, Sweden, Ukraine, UK), North America (Canada, Alberta, Nova Scotia, Ontario, Quebec, USA, Arizona, California, Connecticut, Idaho, Indiana, Iowa, Maine, Michigan, Minnesota, Montana, Nebraska, North Dakota, Ohio, South Dakota, Texas, Washington, Wisconsin, Wyoming), Oceania (Australia, Queensland), and South America (Chile).

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

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.

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

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.

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

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.

Bedeutung von Fäulniserregern für die Lagerung von Zuckerrüben und mögliche Kontrollmaßnahmen

Die zeitliche Ausweitung der Rübenkampagne stellt Anbauer sowie Zuckerfabriken vor neue Herausforderungen hinsichtlich der Langzeitlagerung von Zuckerrüben. Einflussfaktoren, die eine Qualitätsminderung zur Folge haben, nehmen dabei an Bedeutung zu. Infolge einer mikrobiellen Besiedlung kommt es zur Ausprägung von Lagerfäulen, die neben Zuckerverlusten auch die weitere Verarbeitungsqualität durch Anreicherung von unerwünschten Inhaltsstoffen erheblich beeinträchtigen. Die in Frage kommenden Mikro- organismen umfassen bekannte Pflanzenpathogene (z.B. Aphanomyces cochlioides), Wundpathogene (z.B. Fusarium spp.), Saprophyten (z.B. Mucor spp.) sowie Bakterien (z.B. Leuconostoc mesenteroides). Das Auftreten von Lagerfäulen ist charakterisiert durch eine starke Abhängigkeit von der Anbauumwelt. Es wird angenommen, dass neben starken Beschädigungen auch hohe Mengen Erdanhang sowie feuchte und warme Erntebedingungen ihr Auftreten fördern. Die Bekämpfung konzentriert sich in der Praxis bisher auf das Mietenmanagement. Durch Fortschritte im Bereich der Züchtung und Erntetechnik bieten sich auch hier Möglichkeiten einer Reduzierung des Auftretens von Lagerfäulen. Ziel dieses Übersichtsartikels ist es, die Ursachen und Folgen von Lagerfäulen zu beschreiben und praxisrelevante Bekämpfungsmaßnahmen zu erläutern.