Indoleacetic acid enhancement of 14C methionine uptake by tomato cell cultures aids assay of pathogen extracts

Incorporation of one micromolar IAA in the assay system increased the rate of ¹⁴C methionine uptake by tomato cells in suspension and effectively differentiated the rates of uptake such that cells treated with pathogenic and non-pathogenic Fusarium extracts could be easily distinguished in a rapid 3 h assay.     

Distribution of Fusarium wilt of Bambara nut (Vigna subterranea (L.) Verdc.) in farmers’ fields’ of Busia County in Western Kenya and its management using farmyard manure

A study was carried out to determine Fusarium wilt distribution in Bambara nut farmers’ fields and its management using farm yard manure (FYM). Four villages in Busia County were purposively sampled for the study. The data generated were subjected to analysis of variance and treatment means separated by least significant difference test. Fusarium wilt incidence in the fields ranged from 14.63 to 43.56%. In the greenhouse, FYM reduced the disease incidence by 10.2% and severity by 9.5% on the black landrace and 1.9 and 12.8%, respectively, on the red landrace. In the field, FYM reduced disease incidence by 9.1% and severity by 6.9% on the black landrace and 10.4 and 10.4%, respectively, on the red landrace. Farm yard manure had the lowest area under disease progress curve irrespective of the landrace. The study confirmed the presence of the pathogen in the fields and the ability to manage the disease using FYM.     

Spatial pattern of pine wilt disease caused byBursaphelenchus xylophilus (Nematoda: Aphelenchoididae) within aPinus thunbergii stand

To understand the mechanism of spread of pine wilt disease caused by the pinewood nematode, Bursaphelenchus xylophilus, which is vectored by a cerambycid, Monochamus alternatus, the spatial distribution of trees weakened by the nematode was examined within a Pinus thunbergii stand from June to October for 4 years. The weakened trees were distributed in a clumped pattern in 1980 and 1981, at an early stage of infestation. In many cases, they showed a double-clumped pattern. The degree of aggregation was higher in June or July than after August. They were uniformly distributed in June or July 1982 and in June 1983 whereas they showed a double-clumped pattern after August. The trees were frequently weakened in June or July when they were near the trees weakened during the previous year. At quadrat sizes of more than 25 m², spatial overlapping was pronounced between trees weakened during June–July of the current year and those weakened in the previous year. The seasonal changes in spatial distribution of weakened trees were explained by the interaction among M. alternatus, B. xylophilus and Pinus trees.     

Ethanol production from pentoses and sugar-cane bagasse hemicellulose hydrolysate by Mucor and Fusarium species

The fermentation of carbohydrates and hemicellulose hydrolysate by Mucor and Fusarium species has been investigated, with the following results. Both Mucor and Fusarium species are able to ferment various sugars and alditols, including d-glucose, pentoses and xylitol, to ethanol. Mucor is able to ferment sugar-cane bagasse hemicellulose hydrolysate to ethanol. Fusarium F5 is not able to ferment sugar-cane bagasse hemicellulose hydrolysate to ethanol. During fermentation of hemicellulose hydrolysates, d-glucose was utilized first, followed by d-xylose and l-arabinose. Small amounts of xylitol were produced by Mucor from d-xylose through oxidoreduction reactions, presumably mediated by the enzyme aldose reductase¹ (alditol: NADP⁺ 1-oxidoreductase, EC 1.1.1.21). For pentose fermentation, d-xylose was the preferred substrate. Only small amounts of ethanol were produced from l-arabinose and d-arabitol. No ethanol was produced from l-xylose, d-arabinose or l-arabitol.     

Genetic variation, real-time PCR, metabolites and mycotoxins ofFusarium avenaceum and related species

In this paper the latest studies dealing with genetic variation and mycotoxins ofF. avenaceum and related species are reviewed and compared to the data from chromatographic image analyses. Forty-three European strains ofFusarium avenaceum and related species were classified by chromatographic image analysis on full chromatographic matrices. The results were in most cases in agreement with those from morphological and molecular analyses and supported the separation betweenF. avenaceum, F. arthrosporioides andF. tricinctum and betweenF. avenaceum groups I and II. The mycotoxin profiles of the FinnishF. avenaceum, F. arthrosporioides andF tricinctum strains were very similar to each other. Moniliformin and enniatins were the main mycotoxins produced. A fluorogenic TaqMan PCR assay (qPCR) was used for the detection ofF. avenaceum/ F. arthrosporioides DNA in Finnish barley and wheat. The qPCR results obtained from grain samples were compared to mycotoxin levels. A correlation was found betweenF. avenaceum/F. arthrosporioides DNA and moniliformin (MON) and enniatin (ENNs) levels in barley. A correlation was also found between the combinedF. avenaceum/F. arthrosporioides/F. tricinctum contamination and MON and ENNs levels in barley in 2002, but not in 2003. This was probably due to the higher MON and ENNs levels in 2002 than in 2003. It was possible to use the DNA levels ofF. avenaceum/F. arthrosporioides to distinguish between most barley samples containing high amounts of MON and ENNs from those containing low levels of the mycotoxins. Presented at the EU-USA Bilateral Workshop on Toxigenic Fungi & Mycotoxins, New Orleans, USA, July 5–7, 2005 Financial support: Grants from the National Technology Agency of Finland (No. 40168/03) and the Academy of Finland (No. 52104); travel grants from NorFA and the European Commission to the Laboratory of Dr. Ulf Thrane     

Genetic variation for foot-rot and Fusarium head-blight resistances among full-sib families of a self-incompatible winter rye (Secale cereale L.) population

The amount of genetic variation for resistance to foot rot caused by Pseudocercosporella herpotrichoides, Fusarium spp., and Microdochium nivale and for resistance to head blight caused by Fusarium culmorum are important parameters when estimating selection gain from recurrent selection in winter rye. One-hundred and eighty-six full-sib families of the selfincompatible population variety Halo, representing the Petkus gene pool, were tested for foot-rot resistance at five German location-year combinations (environments) and for head-blight resistance in three environments with artificial inoculation in all but one environment. Foot-rot rating was based on 25 stems per plot scored individually on a 1–9 scale. Head-blight resistance was plotwise scored on a 1–9 scale and, additionally, grain-weight per spike was measured relative to the non-inoculated control plots. Significant estimates of genotypic variance and medium-sized heritabilities (h ²=0.51–0.69) were observed in the combined analyses for all resistance traits. In four out of five environments, the amount of genetic variance was substantially smaller for foot-rot than for head-blight rating. Considerable environmental effects and significant genotype-environment interactions were found for both foot-rot and head-blight resistance. Coefficients of error-corrected correlation among environments were considerably closer than phenotypic correlations. No significant association was found between the resistances to both diseases (r=-0.20 to 0.17). In conclusion, intra-population improvement by recurrent selection should lead to substantial higher foot-rot and head-blight resistances due to significant quantitative genetic variation within Halo. Selection should be carried out in several environments. Lack of correlation between foot-rot and head-blight resistance requires separate infection tests for improving both resistances.     

Disseminated cutaneous and vascular invasion byFusarium moniliforme in a fatal case of acute lymphocytic leukemia

A 35 year old female patient with acute lymphocytic leukemia developed fusariosis in which dissemination appeared to be limited to cutaneous and vascular invasion. The first evidence of fungemia occurred nearly seven months after initial hospitalization. The fungus was identified asFusarium sp. and was considered a contaminant. Two weeks later blood cultures were again positive forFusarium sp. and the patient was placed on amphotericin B and 5-fluorocytosine therapy. The following day developing lesions were noted on her forearms and face; lesions ultimately spread to her trunk, abdomen, and lower extremities. Skin lesion biopsy sections revealed abundant septate and branching hyphae throughout the dermis and within capillaries. Twenty-six days after the initial isolation the patient died. Post-mortem blood cultures gave rise to the same fungus, which was identified asFusarium monoliforme. Postmortem cultures and stains of spleen, liver, lung, and brain specimens were all negative for fungi. The primary source and portal of entry of the organism remained undetermined.     

Relative growth rate correlates negatively with pathogen resistance in radish: the role of plant chemistry

Plant growth rate has frequently been associated with herbivore defence: a large investment in quantitative defence compounds occurs at the expense of growth. We tested whether such a relationship also holds for growth rate and pathogen resistance. For 15 radish (Raphanus sativus L.) cultivars, we determined the potential growth rate and the resistance to fungal wilt disease caused by Fusarium oxysporum. We subsequently aimed to explain a putative negative relationship between growth rate and resistance based on plant chemical composition. Both growth rate and resistance level varied greatly among cultivars. Moreover, there was a strong negative correlation between growth rate and resistance, i.e. there are costs associated with a high resistance level. Roots of slow-growing, resistant cultivars have a higher biomass density. Using pyrolysis mass spectrometry. we part1y explained variation in both growth rate and resistance in terms of the same change in chemical composition. Leaves of slow-growing, resistant cultivars contained more cell wall material. Surprisingly, roots of slow-growing, highly resistant cultivars contained significantly less cell wall material, and more cytoplasmic elements (proteins). We speculate that this higher protein concentration is related to high construction and turn-over costs and high metabolic activity. The latter in turn is thought to be responsible for a rapid and adequate resistance reaction, in which phenols may be involved.