Lois H. Tiffany

Expansion of the sooty blotch and flyspeck complex on apples based on analysis of ribosomal DNA gene sequences and morphology

Sooty blotch and flyspeck (SBFS) is a late-season disease of apple and pear fruit that cosmetically damages the cuticle, resulting in produce that is unacceptable to consumers. Previous studies reported that four species of fungi comprise the SBFS complex. We examined fungal morphology and the internal transcriber spacer (ITS) and large subunit (LSU) regions of rDNA of 422 fungal isolates within the SBFS complex from nine orchards in four Midwestern states (USA) and compared them to previously identified species. We used LSU sequences to phylogenetically place the isolates at the order or genus level and then used ITS sequences to identify lineages that could be species. We used mycelial and conidial morphology on apple and in culture to delimit putative species. Thirty putative species found among the Midwest samples were shown to cause SBFS lesions on apple fruit in inoculation field trials. Among them Peltaster fructicola and Zygophiala jamaicensis have been associated previously with SBFS in North Carolina. The LSU analyses inferred that all 30 SBFS fungi from Midwestern orchards were Dothideomycetes; one putative species was within the Pleosporales, 27 were within Dothideales, and two putative species could not be placed at the ordinal level. The LSU sequences of 17 Dothideales species clustered with LSU sequences of known species of Mycosphaerella.

Distribution and seasonal occurrence of aquatic Saprolegniaceae in Northwest Iowa

Nine aquatic sites in northwest Iowa were sampled at three week intervals from April through November in 1977 and 1978 for members of the Saprolegniaceae. Saprolegnia diclina was associated predomi...

Formation of Calcium Oxalate Crystals Associated with Apothecia of the Discomycete Dasyscypha capitata

Calcium oxalate dihydrate crystals form at or near the tips of sterile hairs on the apothecia of the oak leaf litter discomycete Dasyscypha capitata. Early in their development, the crystals appear to be covered by a wall or membrane, whereas later they appear external. The crystals on each hair form a mass of crystals called a druse. Quite often the smaller crystals near the apex of the tip form a rosette, whereas the more peripheral crystals are much larger and display shapes possibly related to environmental factors. The formation and development of Dasyscypha crystals are compared with recent studies of other litter and soil fungi and their presence in other biological systems is put into perspective.

Oak-leaf-litter rhizomorphs from Iowa and Texas: calcium oxalate producers.

Unidentified basidiomycete rhizomorphs growing on oak-leaf litter {Quercus alba) in Iowa and in Texas {Quercus gravesii) displayed arrays of crystals associated with their hyphae. X-ray diffraction and birefringence analyses identified the crystals as a mix- ture of calcium oxalate-monohydrate and -dihydrate. The Iowa oak-leaf-litter rhizomorph crystals occurred in two forms: young hyphae displayed either small styloid-like crystals oriented in all directions along the hyphae; or large clusters of elongated styloid-like crys? tals surrounding the hyphae, with individual crystals in each cluster displaying pyramidal ends. Crystals as? sociated with the Texas oak-leaf-litter rhizomorphs consistently covered all of the young hyphae and their tips with either small dagger-like crystals or thin, plate? like crystals whose margins were either smooth or fin- ger-like. Some larger crystal masses were also com- posed of crystals with pyramidal ends. The dagger-like and plate-like crystals were tentatively identified as the monohydrate form based on their higher birefrin? gence, whereas the crystals with pyramidal ends were identified as the dihydrate form based on their shape and lower birefringence. It is not known whether the two crystalline forms associated with the rhizomorphs are a function of the individual rhizomorphs, the litter source, the stage of crystal growth, or the ions present in the surrounding soil/ground water.

Ultrastructure of the ascocarps, asci, and ascospores of Mycosphaerella populorum

Mycosphaerella populorum ascocarps, developing in overwintering poplar leaves, exhibit character? istics typical of the Dothideales of the Loculoascomycetidae. Each pseudothecium develops a locule containing a fascicle of bitunicate asci which arise asynchronously from basal ascogenous cells, an ostiole without periphyses, and heavily melanized outer wall cells. Ascospore-delimiting membranes seem to arise from the ascus plasmalemma and to assist in spore wall formation. Mature ascospores are one-septate with a central pore. The ascospores usually germinate by a germ tube from each cell. The germ tubes seem to penetrate the leaf only through stomata.

Soil Fungi Isolated from Fields Under Different Tillage and Weed-Control Regimes

A qualitative and quantitative survey of soil microfungi isolated from fields under two tillage regimes and three levels of atrazine application was undertaken. Using the soil-plate method, 1,658 c...

Host-parasite relations and development of Elsinoë panici

Hyphae of Elsinoe panici Tiffany and Mathre penetrated between epidermal cells of Panicum virgatum L. and quickly formed stromata composed of darkly pigmented, firm, pseudoparenchymatous cells. Int...

In vitro production of Mycosphaerella populorum ascomata

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