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Globally, maize ( Zea mays L . ) is deemed an important cereal that serves as a staple food and feed for humans and animals, respectively. Across the East African Community, maize is the staple food responsible for providing over one-third of calories in diets. Ideally, stored maize functions as man-made grain ecosystems, with nutritive quality changes influenced predominantly by chemical, biological, and physical factors. Food spoilage and fungal contamination are convergent reasons that contribute to the exacerbation of mycotoxins prevalence, particularly when storage conditions have deteriorated. In Kenya, aflatoxins are known to be endemic with the 2004 acute aflatoxicosis outbreak being described as one of the most ravaging epidemics in the history of human mycotoxin poisoning. In Tanzania, the worst aflatoxin outbreak occurred in 2016 with case fatalities reaching 50%. Similar cases of aflatoxicoses have also been reported in Uganda, scenarios that depict the severity of mycotoxin contamination across this region. Rwanda, Burundi, and South Sudan seemingly have minimal occurrences and fatalities of aflatoxicoses and aflatoxin contamination. Low diet diversity tends to aggravate human exposure to aflatoxins since maize, as a dietetic staple, is highly aflatoxin-prone. In light of this, it becomes imperative to formulate and develop workable control frameworks that can be embraced in minimizing aflatoxin contamination throughout the food chain. This review evaluates the scope and magnitude of aflatoxin contamination in post-harvest maize and climate susceptibility within an East African Community context. The paper also treats the potential green control strategies against Aspergillus spoilage including biocontrol-prophylactic handling for better and durable maize production.

Fungal diversity in the rhizosphere of healthy and diseased clonal black spruce (Picea mariana) plants was analyzed with regard to nursery production chronosequences. The four key production stages were sampled: mother plants (MP), 8-week-old cuttings (B + 0), second-year cuttings (B + 1), and third-year cuttings (B + 2). A total of 45 fungal taxa were isolated and identified based on cultural, phenotypic, and molecular characters. Members of phylum Ascomycota dominated, followed by Basidiomycota and Zygomycota. Diagnosis characters and distance analysis of the internal transcribed spacer rDNA sequences allowed the identification of 39 ascomycetous taxa. Many belong to the order Hypocreales, families Hypocreaceae and Nectriaceae, which contain many clusters of potentially pathogenic taxa (Cylindrocladium, Fusarium, and Neonectria) and are also ecologically associated with antagonistic taxa (Chaetomium, Hypocrea, Microsphaeropsis, Penicillium, Paecilomyces, Verticillium, Trichoderma, and Sporothrix). This is also the first report of a Cylindrocladium canadense association with disease symptoms and relation with Pestalotiopsis, Fusarium, Exserochilum, Rhizoctonia, and Xenochalara fungal consortia. Both production chronosequence and plant health considerably influenced fungal taxa assemblages. Unweighted pair-group arithmetic average clustering showed that isolates from MP, B + 0, and B + 1 plant rhizospheres clustered together within healthy or diseased health classes, whereas isolates from healthy and diseased B + 2 plants clustered together. Canonical correspondence analysis revealed substantial alteration in community assemblages with regard to plant health and yielded a principal axis direction that regrouped taxa associated with diseased plant rhizosphere soil, whereas the opposite axis direction was associated with healthy plants. Two diversity indices were defined and applied to assess the fungal taxa contribution (Tc) and persistence (Pi) throughout the production.

The dynamic equilibrium of an ecosystem is driven by mutual feedback interactions between plants and soil microorganisms. Asparagus exerts a particularly strong influence on its soil environment through abundant production of persistent phenolic acids, which impact selectively soil microorganisms and may be involved in Fusarium crown and root rot (FCRR) of asparagus. In a survey of 50 asparagus plantations of the province of Québec, we found that FCRR was associated with a profound cultivar-specific, reorganization of the soil microbial community, as revealed by phospholipid fatty acid (PLFA) profiling. According to PLFA indicators, microbial biodiversity as well as bacterial and fungal abundance dropped sharply with the onset of FCRR in fields planted with the cultivar Guelph Millenium. This drop was followed by a similar drop in the arbuscular mycorrhizal population. Biodiversity and microbial population size then increased to finally reach a new equilibrium. Discriminant analysis of PLFA profiles obtained from soil samples also indicated a shift in soil microbial community structure associated with FCRR development in fields planted with the cultivar Jersey Giant. Different soil biological conditions, as indicated by microbial biomass C and N and soil enzyme activities, were associated with different cultivars. Preceding crop, manure application, geographical location and tillage depth also influenced the structure of soil microbial communities in asparagus plantations, as determined by PLFA profiling. If higher FCRR incidence is a consequence of the soil microbial community reorganization, means to reduce FCRR incidence in asparagus plantations may be found among practices such as soil organic fertilization, soil tillage and intercropping strategies that would dilute the negative influence of asparagus on the soil microbial community. Finally, FCRR outbreaks were generally promoted by a previous crop of maize. It seems that maize and asparagus host a F. proliferatum teleomorph (Gibberella fujikoroi) of the same mating type.

Abstract only During October 2002, symptoms of root rot of black spruce, Picea mariana (Mill.) B.S.P., were observed in the St-Modeste (47°46′N, 69°36′W) conifer nursery (400 km northeast of Montreal, Quebec, Canada). Disease severity was low in the greenhouse-produced mother plants and 1-year-old seedlings and moderate in field-grown 2- and 3-year-old seedlings. A species of Cylindrocladium was isolated on potato dextrose agar from 12 symptomatic seedlings from the greenhouse and 12 from the field. The isolates produced chestnut-colored colonies and chlamydospores, both of which were typical of C. canadense Kang, Crous & Schoch (2). DNA was extracted from representative isolates (MTF 101, MTF 102), and the internal transcribed spacer (ITS) of the rDNA gene was amplified and sequenced (GenBank Accession Nos. AY705980 and AY705981). There was a 99% match with a sequence of C. canadense (GenBank Accession No. AF348256). However, there was approximately 10% divergence with the ITS sequence of C. floridanum (GenBank Accession No AF307343). MTF101 and MTF102 were pathogenic on black spruce seedlings when fungal suspension (10 6 CFU/ml) was added to germinating seeds in petri plates or infiltrated into roots of 2-week-old seedlings growing in sterilized, moist, sandy soil in the greenhouse. Within 3 weeks, inoculated seedlings exhibited typical root necrosis, while control seedlings were symptomless. C. canadense was reisolated only from symptomatic seedlings. The occurrence of C. canadense in eastern North America has significant implications for forestry regeneration. Previously, only C. floridanum had been reported as pathogenic in the St-Modeste nursery and in eastern North America(1). References: (1) R. C. Hamelin et al. Appl. Environ. Microbiol. 62:4026, 1996. (2) J. C. Kang et al. Syst. Appl. Microbiol. 24:206, 2001.

This study reports the ability of Fusarium to induce orchid seed colouration and germination. The in vitro bioassay germination test, using a Fusarium isolate from the protocorm of Cypripedium reginae, was compared with standard chemical procedures of triphenyl tetrazolium chloride (TTC) and acid fuchsin (AC) for testing seed viability. With Cypripedium reginae, Cypripedium parviflorum and Platanthera grandiflora, the efficiency of the bioassay was similar to that of the TTC and AC procedures. However, the bioassay was more appropriate for estimating embryo viability after a prolonged seed pretreatment (more than 2h) in 10% sodium hypochlorite, a surface sterilant often used to enhance germination of terrestrial species. We also obtained in vitro Cypripedium reginae seed germination induction and protocorm formation by the same Fusarium isolate. This is the first confirmation of Bernard's early reports that orchid fusaria could stimulate seed germination (Bernard N. 1990.Révue Générale de Botanique12 : 108–120). However, the importance of the non-mycorrhizal Fusarium fungus in promoting germination seems to be relatively minor compared to that of specificRhizoctonia orchid mycorrhizas. Our results are discussed in light of the current North American strategy on orchid conservation methods which proposes the use of symbiotic germination.

Abstract only In August 2002, Phytophthora megasperma Drechs. was isolated from wilted plants of Asparagus officinalis L. cv. Guelph Millenium displaying spear and crown rot. Six affected plants were sampled in a commercial asparagus field located in the Saguenay-Lac-Saint-Jean Region (300 km northeast of Montreal, Quebec, Canada). The fungus was isolated from asparagus fern stalks, crown tissue, and spears after a rainy period and identified using morphological and cultural characteristics (2). In pinkish 4-week-old cultures, unbranched stalks bore abundant sporangia, which were ovoid to obpyriform in shape, 15 to 45 m long, and 10 to 30 m in diameter. Characteristic circular oospores >30 m in diameter were produced on V8 juice agar at 25°C in darkness after 1 month. Pathogenicity was tested on asparagus cvs. Guelph Millenium and Jersey Knight. A mycelium suspension (3 ml at 10 6 CFU/ml) prepared from 1-week-old shaken potato dextrose (PD) broth was sprayed on 30 1-week-old seedlings grown in petri plates filled with sterilized, moist, sandy soil and held at 20°C (day/night). Controls received sterile PD broth. Within 3 weeks of incubation in the dark, inoculated seedlings exhibited necrotic symptoms similar to those observed initially, while controls remained healthy. The pathogen was isolated from 75% of the ‘Guelph Millenium’ and 98% of the ‘Jersey Knight’ symptomatic seedlings, but not isolated from the control seedlings. In North America, disease caused by P. megasperma resulting in yield loss has been reported in California and New York (1,3). In Canada, the etiology of asparagus diseases is not well characterized. To our knowledge, this is the first report of P. megasperma on asparagus plants in Canada. References: (1) P. A. Ark and J. T. Barrett. Phytopathology 28:754, 1938. (2) D. C. Erwin et al. Phytophthora: Its Biology, Taxonomy, Ecology, and Pathology. The American Phytopathological Society, St Paul, MN, 1983. (3) T-L. Kuan and D. C. Erwin. Phytopathology 70:333, 1980.

Asparagus officinalis is a valuable perennial crop that showed a decline in the past decades leading to a loss in productivity, longevity and profitability of the fields. Fusarium species are the main pathogens responsible for the asparagus fields productivity decline and we previously showed that their populations in asparagus fields were composed of numerous species. In order to be able to rapidly process large number of samples, a Fusarium specific PCR-DGGE (denaturing gradient gel electrophoresis) method was developed and applied. DGGE is a highly discriminant culture-independent method with a theoretical resolution limit of one base pair between PCR products of similar length. Fusarium species diversity in commercial production fields is analysed by both PCR-DGGE and isolation on MBA selective medium, in relation with the following factors: geographic production area, effect of the first cropping season, cultural practices, arbuscular mycorrhizal fungi diversity, and age of the asparagus fields (1st year: installation of plants in the field; 3rd year: beginning of the harvest; and 5-6th years: first observed decline of production).

Pseudorobillarda monica sp. nov. is described and illustrated. The endophyte was isolated from living leaves and bark of twigs of a Thuja occidentalis bonsai (>90 years old) at the Montréal Botanical Garden and ornamental trees in Montréal urban plantations. This pycnidial fungus is typical of the genus in morphology but clearly differs from other species in Pseudorobillarda by the distinct size of the conidiomata and the shape and size of conidia and paraphyses. Its taxonomic placement is discussed and a key to the species of Pseudorobillarda is provided.

A new selective myclobutanil agar medium for the detection of Fusarium species is proposed. Ten media formulations based on various selective agents (pentachloronitrobenzene (PCNB), Rose Bengal, malachite green, sodium hypochlorite, captan, benomyl, chlorotalonil, myclobutanil, thiram, and cupric sulfate) were compared. First, mycelium growth and colony appearance of Alternaria alternata, Aspergillus flavus, Cladosporium cladosporioides, Epicoccum nigrum,Fusarium sp., Fusarium solani, Fusarium moniliforme, Fusarium oxysporum f.sp. dianthi, Penicillium sp., and Trichoderma viride isolates were compared. Second, the ability of the different media to isolate and enumerate fusaria from asparagus fields was evaluated. The myclobutanil-based medium showed the highest selectivity to Fusarium spp. growth but required a slightly longer incubation time (>5 d) than peptone–pentachloronitrobenzene-based agar (PPA) (< 5 d). PPA allowed a faster fusaria growth but also permited the growth of other moulds. The other media were less selective and did not allow to isolate fusaria or to differenciate them from other growing fungi.Key words: selective medium, myclobutanil, Fusarium, soil, Asparagus.

A new species of Coelomycete, Leptomelanconium abietis, is described and illustrated from chlorotic and necrotic needles of Abies balsamea. This fungus is typical of the genus in morphology and ecology, but clearly different from other known species in Leptomelanconium by host, distinct size of conidiomata, and shape and size of conidia. Its taxonomic placement and relation to other species in this genus and the genus Gloeocoryneum are given.