Survival of Alternaria alternata during anaerobic digestion of biomass in stirred tank reactors.

The survival of Alternaria alternate during anaerobic digestion was investigated in context of a joint research project. The aim of this project was to estimate the phytosanitary risk of dissemination of pathogens by returning treated biomass as organic fertilizer to arable land. The studies were carried out in lab-scale stirred tank reactors under mesophilic conditions. After insertion of infected plant material into the reactors the influence on the viability of the fungal pathogen was studied concerning exposure time, pretreatment and storage of the digestates for four weeks or six months. The results clearly showed that anaerobic digestion leads to a complete inactivation of A. alternate already after an exposure time of six hours.

[Spargelstangenuntersuchungen zur Haupterntezeit auf Infektionen mitFusarium spp. und Kontaminationen mit Fumonisin B1 Investigation on asparagus spears during the main harvest byFusarium spp.- infections and contamination by Fumonisin B1].

Asparagus spears collected from a total of six commercial plantings in Austria during the main harvest periods in May and June of 2003 and 2004 were examined for endophytic colonization byFusarium spp., particularlyF. proliferatum. Potentially toxigenic fungi such asF. proliferatum were isolated and identified by morphological characteristics using light microscopy. Fumonisin B1 inF. proliferatum-infected asparagus spears was detected with IAS-HPLC-FLD or HPLC-MS/MS. The identity of endophytic fungi colonizing of a total of 816 individual spears was determined. The incidence of infection byF. proliferatum and otherFusarium spp. was highly dependent on location and sampling date. The dominantFusarium species among the endophytic microflora wasF. oxysporum. Other frequently isolated species includedF. proliferatum, F. sambucinum, F. culmorum, F. avenaceum andF. equiseti. The incidence ofF. proliferatum-infected asparagus spears was less than 10% at four of the six sampling locations. At the two remaining locations, 20-47% of the spears examined were infected withF. proliferatum. Further exploration of FB1 generation in asparagus is required because the low levels of FB1 (10-50 (µg/kg) detected in harvested spears in 2003 and 2004 cannot be explained by the results of this study.

Yield loss in susceptible cultivars of spring rapeseed due to Fusarium wilt caused by Fusarium oxysporum.

In 1999, reports of spring rapeseed plants (Brassica napus L.) exhibiting wilt symptoms were received by agricultural extension personnel from farmers near Fort Vermillion and Andrew, Alberta, Canada. Fungal colonies recovered from affected plants after surface disinfection were identified as Fusarium oxysporum by comparison of morphology on carnation leaf and potato dextrose agars with literature descriptions and reference cultures. Root-dip inoculation of young rapeseed plants with spore suspensions prepared from recovered F. oxysporum colonies resulted in rapid development of symptoms seen in the field. An initial estimate of yield loss in an affected field near Andrew was performed by removing all rapeseed plants from three 1 m2 quadrats. Each plant was evaluated according to a simple three point severity scale, and then the seed from each plant was individually threshed and weighed. Fully- and partially-wilted plants yielded 0.2 and 19.3% of asymptomatic plants, respectively. In 2000, wilt symptoms were observed at a plot research site near Ranfurly, Alberta. Disease symptoms were restricted to one B. napus cultivar, Nexera 705. A similar procedure to that used at Andrew in 1999 was applied at Ranfurly, except quadrat size was 2.5 m2, and replicated comparisons were made between Nexera 705 and an unaffected cultivar, Quantum. The average number of unaffected Quantum plants was 99.4%, while only 66.9% of Nexera 705 plants were asymptomatic. No Quantum plants were severely wilted, while 11.7% of Nexera 705 plants were wilted. Yield of Nexera 705 was 38.6% of Quantum. In 2004, the impact of fusarium wilt on yield of 6 susceptible and 9 resistant B. napus cultivars was determined at nine locations in western Canada. Cultivars were selected on the basis of survey results and agronomist's reports. Across all sites, yield of the most severely affected cultivar, 45A55, was 15.9% lower than the least severely affected cultivar 3455. At the most severely affected site, yield of the most severely affected cultivar, Bianca II, was 75.2% lower than the least severely affected cultivar, Option 501. Yield of wilt-susceptible (Canterra 1604) and resistant (Cougar CL) rapeseed was compared at a replicated large-plot (576 m2 per plot) experiment at Lavoy, Alberta in 2005. The susceptible variety was severely affected and yielded 44% of Cougar CL.

[Not Available]. / Untersuchungen zur pathogenität und mykotoxinbildung vonFusarium sambucinum, dem erreger der trockenfäule an kartoffeln.

Investigation into virulence and mycotoxin formation of the dry rot causing pathogen Fusarium sambucinum on potatos 11 strains ofFusarium sambucinum were isolated from tubers with dry rot symptoms from three different depots in the Land Brandenburg and Saxony-Anhalt. All isolates produced diacetoxyscripenol in artificially infected potato tubers. Additionally, two isolates produced T-2 and HT-2 toxins as well. The virulence and mycotoxin formation of the isolates was dependent on the potato varieties 'Sieglinde' and 'Berber' used in the experiment. The amount of diacetoxyscripenol in diseased tissue was positively correlated with the virulence of theF. sambucinum isolate and the susceptibility of the potato variety as well.

[Fusaria and their mycotoxins in hay and grass silage from grassland with different intensities of management]. / Nachweis von Fusarien und deren Mykotoxinen in Futterkonservaten aus Grünlandbeständen mit differenzierter Bewirtschaftungsintensität.

Conservation forage (17 hay and 18 grass silage samples) from 15 farms with different intensities of grassland management in the Federal State of Brandenburg were examined for contamination with fusaria and their mycotoxins. The numbers of culturable filamentous fungi in hay were determined by plate counting andFusarium isolates were classified taxonomically. The mycotoxins Zearalenone (ZEA) and Deoxynivalenol (DON) were extracted from hay as well as silage by different procedures and detected chromatographically (HPLC). The numbers of filamentous fungi in the hay samples were 10(2) and 10(6) CFU/g FM independently of intensive or extensive management. Only fourFusarium species were identified.Fusarium culmorum, a potential toxin producing species, was most frequently detected (52% of all isolates). ZEA was found in two hay and four silage samples (6-66 µg/kg), DON in three hay and seven silage samples (63-1290 µg/kg). There were no differences between forage samples of extensive and intensive cultivated grassland of the year 2003 regarding numbers of fusaria and the content of their mycotoxins.

Occurrence of fumonisins in asparagus (asparagus officinalis L.) and garlic (allium sativum L.) from Germany.

Fusarium proliferatum is able to produce fumonisins and is considered a pathogen of many economically important plants (e.g. corn, rice, asparagus) [1]. The occurrence of fumonisin FB1 inF. proliferatum infected asparagus spears from Germany was investigated using a liquid chromatography/electrospray ionization-mass spectrometry (LC-ESI-MS) method with isotopically labeled fumonisin FB1-d6 as internal standard. Asparagus samples were harvested in July 2000 and screened forFusarium species. AltogetherF. oxysporum, F. proliferatum and F. sambucinum were isolated from the spears. The samples infected with F.proliferatum were subsequently analyzed for fumonisins. FB1 was detected in 9 of the 10 samples in amounts ranging from 36.4 ng/g to 4513.7 ng/g (based on dry weight). Fumonisins FB2 and FB3 were found in six samples in lower concentrations. In asparagus spears of June 2002 we could findF. proliferatum in 6% of the samples, however no fumonisins were detectable.Furthermore the capability of producing FB1 by the fungus in garlic bulbs was investigated. Therefore garlic was cultured inF. proliferatum contaminated soil and the bulbs were screened for infection with F.proliferatum and for the occurrence of fumonisins by LC-MS. F.proliferatum was detectable in the garlic tissue and all samples contained FB1 (26.0 ng/g to 94.6 ng/g).This is the first report of the natural occurrence of FB1 in German asparagus spears and furthermore our findings suggest a potential for natural contamination of garlic bulbs with fumonisins. For detailed results and methods see Ref. [2].

The potential of pathogens as biological control of parthenium weed (Parthenium hysterophorus L.) in Ethiopia.

P. hsyterophorus is an exotic invasive annual weed now causing severe infestation in Ethiopia. Studies on diagnosis, incidence and distribution of pathogens associated with parthenium weed in Ethiopia were carried out from 1998-2002. Several fungal isolates were obtained from seed and other parts of parthenium plants. Among them were putative pathogenic fungal species of the genus Helminthosporium, Phoma, Curvularia, Chaetomium, Alternaria, and Fusarium. However, pathogenecity test of the isolates obtained showed no or non-specific symptoms. It was concluded that these pathogens could be opportunistic with insignificant potential for biological control of parthenium. Two most important diseases associated with parthenium were a rust disease, caused by Puccinia abrupta var. partheniicola, and a phyllody disease, caused by a phytoplasma of fababean phyllody (PBP) phytoplasma group. The rust was commonly found in cool mid altitude (1500-2500 m) areas while phyllody was observed in low to mid altitude regions (900-2500 m) of Ethiopia, with a disease incidence up to 100% and 75%, respectively, in some locations. Study of the individual effects of the rust and phyllody diseases under field conditions showed a reduction on weed morphological parameters (plant height, leaf area, and dry matter yield). Parthenium seed production was reduced by 42% and 85% due to rust and phyllody, respectively. Phyllody and rust diseases of parthenium showed significant potential for classical biological control of parthenium after further confirmation of insect vectors that transmit phyllody and host range of phyllody disease to the related economic plants in Ethiopia.