Comparative genomics of geographically distant Fusarium fujikuroi isolates revealed two distinct pathotypes correlating with secondary metabolite profiles

Fusarium fujikuroi causes bakanae ("foolish seedling") disease of rice which is characterized by hyper-elongation of seedlings resulting from production of gibberellic acids (GAs) by the fungus. This plant pathogen is also known for production of harmful mycotoxins, such as fusarins, fusaric acid, apicidin F and beauvericin. Recently, we generated the first de novo genome sequence of F. fujikuroi strain IMI 58289 combined with extensive transcriptional, epigenetic, proteomic and chemical product analyses. GA production was shown to provide a selective advantage during infection of the preferred host plant rice. Here, we provide genome sequences of eight additional F. fujikuroi isolates from distant geographic regions. The isolates differ in the size of chromosomes, most likely due to variability of subtelomeric regions, the type of asexual spores (microconidia and/or macroconidia), and the number and expression of secondary metabolite gene clusters. Whilst most of the isolates caused the typical bakanae symptoms, one isolate, B14, caused stunting and early withering of infected seedlings. In contrast to the other isolates, B14 produced no GAs but high amounts of fumonisins during infection on rice. Furthermore, it differed from the other isolates by the presence of three additional polyketide synthase (PKS) genes (PKS40, PKS43, PKS51) and the absence of the F. fujikuroi-specific apicidin F (NRPS31) gene cluster. Analysis of additional field isolates confirmed the strong correlation between the pathotype (bakanae or stunting/withering), and the ability to produce either GAs or fumonisins. Deletion of the fumonisin and fusaric acid-specific PKS genes in B14 reduced the stunting/withering symptoms, whereas deletion of the PKS51 gene resulted in elevated symptom development. Phylogenetic analyses revealed two subclades of F. fujikuroi strains according to their pathotype and secondary metabolite profiles.

Detection of Fumonisins in Fresh and Dehydrated Commercial Garlic

An epidemic fungal disease caused by Fusarium proliferatum, responsible for fumonisin production (FB1, FB2, and FB3), has been reported in the main garlic-producing countries in recent years. Fumonisins are a group of structurally related toxic metabolites produced by this pathogen. The aim of this work was to establish an enzyme-linked immunosorbent assay (ELISA) procedure, mostly applied to cereals, that is suitable for fumonisin detection in garlic and compare these results to those obtained by high-performance liquid chromatography (HPLC) and screening of fresh and dehydrated garlic for toxicological risk. The results show good correlation between the two analytical methods. In fresh symptomatic garlic, fumonisin levels were higher in the basal plates than those in the portions with necrotic spots. Among the 56 commercially dehydrated garlic samples screened, three were positive by ELISA test and only one was above the limit of quantitation. The same samples analyzed by HPLC showed the presence of FB1 in trace amounts that was below the limit of quantitation; FB2 and FB3 were absent. The results are reassuring, because no substantial contamination by fumonisins was found in commercial garlic.

First Report of Fusarium andiyazi Associated with Rice Bakanae in Italy

Rice (Oryza sativa L.) is cultivated on approximately 230,000 ha in northern Italy. Since 2001, increasing economical losses presumably caused by Fusarium fujikuroi Nirenberg (Gibberella fujikuroi mating population C), an exotic fungus known as the etiological agent of Bakanae disease, have been reported in Italy. The spread of this disease is primarily seedborne. In 2009, during an annual survey of Italian rice seed, 69 samples were tested for the presence of strains belonging to the G. fujikuroi species complex. Four hundred seeds per sample were surface sterilized and then placed in 90-mm Petri dishes containing potato dextrose agar and incubated for 7 days at 21°C. Thirty two putative G. fujikuroi strains were single-spore purified and identified on the basis of their morphological features on Spezieller Nährstoffarmer agar plates with a piece of sterile filter paper. Strains were characterized at species level by morphological observations (1,2) and translation elongation factor 1-α (TEF) gene sequencing. Unexpectedly, 60% of the strains evaluated belonged to the species F. andiyazi Marasas, Rheeder, Lampr., K.A. Zeller & J.F. Leslie. This fungus, first described on sorghum (Sorghum bicolor L.) in Africa and the United States (1), has been reported to be one of the species associated with Bakanae in Asia and Africa (3). Two F. andiyazi strains, (E432 and E439), isolated in the district of Modena were chosen for pathogenicity testing and their TEF gene sequences were deposited in GenBank (Accession Nos. GU827420 and GU827419). A conidial suspension was produced on Mung-bean liquid media and adjusted to a concentration of 1 × 10⁶ CFU/ml. Italian cv. Galileo was used in the test because of its high susceptibility to Bakanae (Ente Nazionale delle Sementi Elette, Verona, Italy, data unpublished). Rice seeds were heat sterilized for 20 min at 60°C, submerged for 30 min in the conidial suspensions, dried, and subjected to a blotter test. Uninoculated, sterilized seeds served as a control. Seeds were incubated for 15 days in a growth chamber (26°C, 80% relative humidity, and 12-h photoperiod). For each strain, the experiment was repeated three times on samples of 25 seedlings. Results were analyzed by analysis of variance and Tukey test. Symptoms consisted of a generic seedling wilt, a root length reduction ranging from 21 to 48%, and the presence of root discoloration. Seed germination was reduced by 9%. Shoot development was not significantly altered. Proof of pathogenicity was obtained through reisolation of F. andiyazi from symptomatic tissues. To our knowledge, this is the first report of F. andiyazi on rice in Europe. References: (1) W. F. O. Marasas et al. Mycologia 93:1203, 2001. (2) H. I. Niremberg and K. O'Donnell. Mycologia 90:434, 1998. (3) E. G. Wulff et al. Environ. Microbiol. 12:649, 2009.

Management and survival of frail elderly cancer patients within a Geriatric Oncology Program

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Background: Abstention from administration of either chemo- or endocrine therapy to elderly cancer patients deemed frail at the Multidimensional Geriatric Assessment is still controversial, and few data are available concerning the actual survival of such patients. Methods: To evaluate the management and survival of all consecutive frail cancer patients older than 70 years, seen from October 2004 to December 2005 within our Geriatric Oncology Program. Frailty was defined by one or more of the following: age ≥ 85 years, dependence in one or more Activity of Daily Living (ADL), presence of at least three comorbidity of grade 3 or one of grade 4 according to CIRS-G, one or more geriatric syndromes [Balducci L, Cancer Control 2001]. Results: A total of 364 elderly patients were divided into three categories: fit (26.4%), vulnerable (49.5%) and frail patients (24.2%). These 88 frail patients had a median age of 79 years (range, 70–93), 43.2% males. Motives for being considered frail were age alone (13.6% of patients), ADL dependence (25%), comorbidity (14.8%), geriatric syndromes (6.8%) or, more frequently, the co-existence of two or more of these factors (39.8%). Thirty patients (34.1%) underwent chemotherapy: 8 for gastro-intestinal tumors, 7 lung, 7 hematological and 8 other sites. Patients received standard regimens at standard doses (27.6%) or with ≥ 25% dose reduction (24.1%), age-adapted regimens at standard doses (44.8%) or with reduced doses (6.9%). Six patients (20%) derived some clinical benefit but only two (6.7%) showed radiological response. Twenty-two patients interrupted chemotherapy prematurely due to toxicity/death (23.3%) or refusal/drop out (26.7%). All twenty-eight women with estrogen receptor positive breast cancer (31.9% of all frail patients) were prescribed endocrine therapy either adjuvantly, neo-adjuvantly or for metastatic disease, with a predominance of aromatase inhibitors (82.1%) compared to tamoxifen. Thirty out of 88 patients have died, with a 2-year overall survival of 35%. Conclusions: Frailty was observed in one fourth of all our elderly patients, but it did not prevent treatment of tumor with either chemo- or endocrine therapy in 66% of cases. Overall survival of frail elderly patients with cancer appears worse than in geriatric series.

No significant financial relationships to disclose.