Claudia C. López Lastra

18S rDNA for species of Leptolegnia and other Peronosporomycetes: justification for the subclass taxa Saprolegniomycetidae and Peronosporomycetidae and division of the Saprolegniaceae sensu lato into the Leptolegniaceae and Saprolegniaceae

The 18S rDNA data.base for mainstream Peronosporomycetes has been substantially increased. The sub-class divide between the Peronosporomycetidae and the Saprolegniomycetidae is supported. The deep clade separation of the Leptomitales within the Peronosporomycetidae is reinforced and support is provided for divergences within the Phytophthora and Pythium lines. A new family for the Leptolegnia lineage is proposed from the Saprolegniaceae sensu lato.

Trichomycetes in Argentinean aquatic insect larvae

Investigations of larval aquatic Diptera (Chironomidae, Simuliidae, Culicidae), Coleoptera (Scirtidae), and Plecoptera (Gripopterygidae, Notonemouridae) in Buenos Aires Province and three Provinces...

An Overview of Arthropod-Associated Fungi from Argentina and Brazil

Arthropod pests in forest and agricultural systems are affected by many pathogenic organisms. Among them, entomopathogenic fungi are the one most common control agents that regulate their populations. This review compiles the information available from Argentina and Brazil about the entomopathogenic fungi occurring in agricultural and natural environments. The scientific names of the fungi are listed according to the latest phylogenetically based classification of fungi. We present an updated list of arthropod-pathogenic fungi occurring in 15 of the 23 provinces of Argentina and 20 of the 27 states of Brazil based on published literature and our personal observations. The list includes a total of 114 fungal species from 53 genera: of Blastocladiomycetes (2 genera), Entomophthorales (8 genera), Harpellales (13 genera), and a diverse assortment of ascomycetes (primarily from Hypocreales) in 22 anamorphic and 5 teleomorphic genera. In the both countries, molecular studies on arthropod-pathogenic fungi are still in their early stages and have focused primarily on intraspecific variability and adequate generic assignment. This listing seeks to encourage more active collection and characterization of these fungi by both traditional and molecular approaches from the obviously rich but underexplored flora of fungi affecting arthropods throughout this large region of South America.

Natural occurrence of entomopathogenic fungi (Zygomycetes: Entomophthorales) of aphid (Hemiptera: Aphididae) pests of horticultural crops in Argentina.

A three-year survey of entomophthoralean pathogenic fungi of aphids from horticultural crops in La Plata, Argentina, was conducted. Nine species of aphids, including Aphis fabae Scopoli, Aphis gossypii Glover, Brevicoryne brassicae (L.), Lipaphis erysimi (Kaltenbach), Macrosiphum euphorbiae (Thomas), Myzus sp., Myzus persicae (Sulzer), Nasonovia ribisnigri (Mosley) and Capitophorus elaeagni (del Guercio) were recorded as hosts of entomopathogenic fungi. Six species of Entomophthorales that infected and killed aphids were found in vegetable crops. The fungal species identified were Conidiobolus obscurus (Hall & Dunn) Remaudière & Keller, Entomophthora planchoniana Cornu, Neozygites fresenii (Nowakowski) Remaudière & Keller, Pandora neoaphidis (Remaudière & Hennebert) Humber, Zoophthoraradicans (Brefeld) Batko and Zoophthora sp. Pandora neoaphidis was the most predominant pathogen of aphids and was found throughout the summer (December–March) 2004. The recovery of C. obscurus, N. fresenii and P. neoaphidis represent first records of these fungi for South America.

Biotic and abiotic factors affecting Leptolegnia chapmanii infection in Aedes aegypti

ABSTRACT The effects of water volume, container surface area and the density of hosts and fungal zoospores on the infectivity of the oomycete fungus Leptolegnia chapmanii to Aedes aegypti were investigated in the laboratory. Late 3rd or early 4th instars from a laboratory colony were used as hosts in all assays. Fourth instars infected with L. chapmanii for 48 h (6.1 ± 0.2 × 104 zoospores/larva) were used as inoculum. Mortality rates were >90% in containers with 20 or fewer larvae when exposed to 1 infected larva, but they decreased to 37% in containers with 60 larvae. Mortality rates varied from 82% to 92% when healthy 4th instars were exposed to 1 and 2 infected larvae, respectively, whereas 100% mortality was obtained with ≥3 infected larvae. Infection and mortality rates in containers with volumes that varied from 300 to 5,000 ml but that had similar water surface area (397 cm2) varied from 89 to 92%, respectively. When water volume was held constant at 250 ml in containers with variable surface areas (14.5–875 cm2), larval mortality varied from 96% to 25%, respectively. The ability of L. chapmanii to infect mosquito larvae is dose dependent and influenced by larval density and surface area.

Prevalence of Harpellales from Chironomidae larvae in phytotelmata from Punta Lara Forest, Argentina

Harpellales (Zygomycota: Trichomycetes) fungi are cosmopolitan obligate inhabitants of the gut of immature insects. A biweekly survey of gut fungi associated with chironomid (Chironomidae: Diptera) larvae living in the impounded water from Eryngium cabrerae (Apiaceae) phytotelmata from Punta Lara forest, Argentina, was done Jan 2003–Dec 2004. Two species of Harpellales were associated with chironomid larvae, Smittium phytotelmatum in the hindgut of Polypedilum sp. and Stachylina lentica in the midgut of both Polypedilum sp. and Metriocnemus eryngiotelmatus. No statistically significant differences were recorded in the prevalence of these Harpellales between seasons. Environmental variables (temperature, rainfall and relative humidity), impounded water volume, pH and chironomid larval density did not have an effect on the prevalence of the Trichomycetes.

First report of Pandora neoaphidis resting spore formation in vivo in aphid hosts

The entomopathogenic fungus Pandora neoaphidis is a recognized pathogen of aphids, causes natural epizootics in aphid populations, and interacts and competes with aphid predators and parasitoids. Survival of entomophthoralean fungi in periods of unsuitable weather conditions or lack of appropriate host insects is accomplished mainly by thick-walled resting spores (zygospores or azygospores). However, resting spores are not known for some entomophthoralean species such as P. neoaphidis. Several hypotheses of P. neoaphidis winter survival can be found in the literature but so far these hypotheses do not include the presence of resting spores. Resting spores were found in an aphid population where P. neoaphidis was the only entomophthoralean fungus observed during surveys conducted in organic horticultural crops in greenhouses and open fields in Buenos Aires province, Argentina. This study sought to use molecular methods to confirm that these resting spores were, in fact, those of P. neoaphidis while further documenting and characterizing these resting spores that were produced in vivo in aphid hosts. The double-walled resting spores were characterized using light and transmission electron microscopy. The Argentinean resting spores clustered together with P. neoaphidis isolates with bootstrap values above 98 % in the small subunit ribosomal RNA (SSU rRNA) sequence analysis and with bootstrap values above 99 % the Internal Transcribed Spacer (ITS) II region sequence analysis. This study is the first gene-based confirmation from either infected hosts or cultures that P. neoaphidis is able to produce resting spores.

Diversity of trichomycetes in larval flies from aquatic habitats in Argentina.

Trichomycetes, mainly from nonbiting midge (Chironomidae), mosquito (Culicidae) and black fly (Simuliidae) larvae (Insecta: Diptera), are reported from diverse freshwater environments principally from previously unexplored areas of Argentina. Four new species of Harpellales are described: Austrosmittium patagonicum, A. lenticum, Smittium basiramosum and Legeriomyces lichtwardtii. This is the first report of Austrosmittium spp. from the Americas and the first report of a Legeriomyces from South America. Two other species (Simuliomyces sp. and Harpella sp.) are described but not named. Fourteen previously described species were recovered, and their geographical distribution and host ranges have been extended for Argentina, with Sm. phytotelmatum, Stachylina lentica, St. lotica and St. penetralis being new records for the country.

Further research on the production, longevity and infectivity of the zoospores of Leptolegnia chapmanii Seymour (Oomycota: Peronosporomycetes)

The effect of temperature on the production, survival and infectivity of zoospores of an Argentinean isolate of Leptolegnia chapmanii was determined under laboratory conditions. Production of zoospores of L. chapmaniiin vitro and in vivo upon first and fourth instars larvae of the mosquito Aedes aegypti was studied at three different temperatures. Zoospores from infected larvae were infective to mosquito larvae for 51, 12, and 5 consecutive days when maintained at 25, 35, and 10 degrees C, respectively. Maximum zoospore production in infected fourth-instar larvae was 9.6+/-1.4x10(4) zoosp/larva at 48 h at 25 degrees C. The average number of zoospores produced by individual fourth-instar Ae. aegypti larvae infected with L. chapmanii was 3.57+/-0.46x10(5) zoospores during 6 consecutive days at 25 degrees C. Zoospore production in vitro was also affected by temperature with a maximum of zoospores (n=47,666/ml) produced at 25 degrees C. When zoospores produced in vitro were used as inoculum against Ae. aegypti larvae at 25 degrees C, larval mortality was recorded for 5 consecutive weeks. The encystment process for zoospores took 17-20 min; the germination of cysts (excystment) occurred 5 min after exposure in water to mosquito larvae. The minimal time of contact between zoospores and mosquito larvae to develop infection was two minutes. Infection took place by zoospore attachment onto and then penetration through the larval cuticle or by ingestion of cysts as was confirmed by histological studies. Temperature directly affected infectivity and production of zoospores in vivo and in vitro although L. chapmanii zoospores tolerate a wide range of temperatures.

Characterization and phylogeny of Isaria spp. strains (Ascomycota: Hypocreales) using ITS1-5.8S-ITS2 and elongation factor 1-alpha sequences

The elongation factor 1‐alpha (EF1‐α) and the internal transcribed spacer (ITS) regions ITS1 and ITS2 (ITS1‐5.8S‐ITS2) sequences were used to characterize and to identify Isaria isolates from Argentina, Mexico, and Brazil, as well as to study the phylogenetic relationships among these isolates and other related fungi from the order Hypocreales. The molecular characterization, which was performed by PCR‐RFLP of EF1‐α and ITS1‐5.8‐ITS2 genes, was useful for resolving representative isolates of Isaria fumosorosea, Isaria farinosa, and Isaria tenuipes and to confirm the taxonomic identity of fungi from Argentina, Mexico, and Brazil. The phylogenetic analyses showed three clades corresponding to three families of Hypocreales. The genus Isaria was confirmed as polyphyletic and in family Cordycipitaceae, Isaria species were related to anamorphic species of Beauveria, Lecanicillium, and Simplicillium and to teleomorphic Cordyceps and Torrubiella. Therefore, EF1‐α and ITS1‐5.8S‐ITS2 genes were found to be powerful tools for improving the characterization, identification, and phylogenetic relationship of the Isaria species and other entomopathogenic fungi.