Master of Science (MS)
Plant Pathology and Crop Physiology
A study documenting basidiomycete yeast biodiversity was conducted in Baton Rouge, Louisiana during 2010 and 2011. Using the spore-fall method, the leaf surfaces of seven ferns were sampled at biweekly intervals. Maximum likelihood phylogenetic analyses of the internal transcribed spacer (ITS) region and the D1/D2 domain of the large subunit (LSU) of nuclear ribosomal DNA were used to identify 463 isolates representing 81 species spanning 12 orders within six classes in Basidiomycota. Nearly 30 of these isolates appear to be species new to science. Data indicate fern leaf developmental stage has an effect on the number of yeasts present. A significant difference exists between the number of isolates recovered from young versus senescent leaves. On average, more yeast isolates were recovered from young leaves than from senescing ones for all classes of yeasts except Ustilaginomycetes, which were more abundant on senescing leaves. The number of yeasts recovered from lower (abaxial) versus upper (adaxial) leaf surfaces did not differ significantly, though isolates were recovered more frequently from abaxial surfaces for all classes expect Microbotryomycetes and Tremellomycetes. For all six classes there was a trend for non-fertile frond portions to yield more isolates than those with sori, but this difference is not statistically significant. Monthly records of temperature and precipitation were compiled and while they show no statistically significant correlation with yeast abundance, several patterns may be meaningful. A general downward trend was observed in the number of isolates recovered with respect to decreasing temperature and increasing precipitation levels. More isolates were recovered during the months with the highest average temperatures and lowest levels of precipitation. Additionally, two new yeast species collected during this survey are provisionally described. SA209 and SA575 represent previously undescribed yeast species in the genera Farysia and Sporisorium (Ustilaginales). The LSU and ITS regions of these isolates were compared to available sequences of Farysizyma and Pseudozyma species and related taxa in Farysia, Sporisorium and Ustilago. SA209 is part of a Farysizyma/Farysia clade in Anthracoideaceae and SA575 is sister to Sporisorium chrysopogonis and S. heteropogonicola within a clade of Sporisorium species that includes the type (S. sorghi).
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Albu, Sebastian, "A survey of ballistosporic phylloplane yeasts in Baton Rouge, Louisiana" (2012). LSU Master's Theses. 3017.
Aime, M. Catherine