Question: Which pathogenic fungus did Annie Gravatt study?

Context paragraphs:
Chestnut blight: The pathogenic fungus Cryphonectria parasitica (formerly "Endothia parasitica") is a member of the Ascomycota (sac fungi) taxon, and is the main cause of chestnut blight—a devastating disease of the American chestnut tree that in the early 1900s caused a rapid, widespread die-off of this once plentiful tree from its historic range in the eastern United States.

Annie Gravatt: Annie Gravatt (Annie Evelyn Rathbun) was an American forest pathologist.  Her areas of research included plant physiology and white pine blister rust.  She also studied Chestnut blight, the fungus that devastated American chestnut trees in the early 20th century.  Along with her husband, George Gravatt, she founded the community of Scientists' Cliffs, Maryland.

Heterobasidion irregulare: Heterobasidion irregulare is a tree root rotting pathogenic fungus that belongs to the genus "Heterobasidion", which includes important pathogens of conifers and other woody plants.  It has a wide host and geographic range throughout North America and causes considerable economic damage in pine plantations in the United States.  This fungus is also a serious worry in eastern Canada.

Microsporum nanum: Microsporum nanum is a pathogenic fungus in the family Arthrodermataceae.  It is a type of dermatophyte which causes infection in dead keratinized tissues such as skin, hair, and nails.  "Microsporum nanum" is found worldwide and is both zoophilic and geophilic.  Animals such as pigs and sheep are the natural hosts for the fungus; however, infection of humans is also possible.  Majority of the human cases reported are associated with pig farming.  The fungus can invade the skin of the host; if it is scratched off by the infected animal, the fungus is still capable of reproducing in soil.

Asteroma: Asteroma is a genus of pathogenic fungus in the family Gnomoniaceae, containing several species that cause leaf spot and canker on plants such as goldenrod, primrose, and "Erythronium".

Penicillium ulaiense: Penicillium ulaiense is a plant pathogen that causes whisker mould.  It is considered an important infection of citrus fruit, especially in packinghouses.  "P. ulaiense" is a citrus postharvest pathogenic fungus described as a member of the serie Italica, together with "P. italicum".  In 1987, mycologists in Taiwan published a description of "P. ulaiense".  Authors familiar with green and blue moulds of citrus had mistaken the fungus for "P. italicum" and dismissed its unique features as variations due to particular environmental conditions.  To date, "P. ulaiense" has been reported in Argentina, Arizona, Australia, California, Florida, Italy, New Zealand, South Africa, Taiwan, and Texas.  In recent times, "P. ulaiense" has been reported in Egypt as a postharvest pathogen of orange fruit.

Armillaria sinapina: Armillaria sinapina is a species of mushroom in the family Physalacriaceae.  A plant pathogenic fungus, it causes Armillaria root disease, and has been found on a variety of tree hosts in Alaska.  The mycelium of the fungus is bioluminescent.

Aspergillus fumigatus non-coding RNAs: "Aspergillus fumigatus" is a pathogenic filamentous fungus and is responsible for more infections worldwide than any other mould.  Studies of the small non-coding RNA transcriptome of this fungus under a variety of different conditions and the subsequent generation of cDNA libraries from size selected small RNA species, identified several non-coding RNAs (ncRNA) within the fungal genome.  The ncRNAs identified were further classified as small nucleolar RNAs (snoRNAs), small nuclear RNAs (snRNAs) or novel ncRNAs.  The expression of these ncRNAs was also shown to be influenced by developmental stages of the fungus and environmental conditions.  Comparative genomics showed that the snoRNAs present within "A. fumigatus" are conserved across other strains of fungus.  This study also identified several partial tRNA sequences within the cDNA libraries which corresponded to either the 5’ or 3’ halves of tRNA molecules.  These partial tRNAs are thought to have been created by enonuclolytic cleavage within the anti-codon loop.  It has been suggested that these partial tRNA stall protein synthesis however, further studies are required to determine their exact function.  The table below summarised the type, genome location and corresponding target sites of the ncRNAs identified in "A. fumigatus".

Corn smut: Corn smut is a plant disease caused by the pathogenic fungus Ustilago maydis that causes smut on maize and teosinte.  The fungus forms galls on all above-ground parts of corn species, and is known in Mexico as the delicacy huitlacoche; which is eaten, usually as a filling, in quesadillas and other tortilla-based foods, and soups.

Rhizoctonia solani: Rhizoctonia solani (teleomorph: Thanatephorus cucumeris) is a plant pathogenic fungus with a wide host range and worldwide distribution.  It was discovered more than 100 years ago.  "R. solani" frequently exists as thread-like growth on plants or in culture, and is considered a soil-borne pathogen.  "R. solani" is best known to cause various plant diseases such as collar rot, root rot, damping off, and wire stem.  "R. solani" attacks its hosts when they are in their early stages of development, such as seeds and seedlings, which are typically found in the soil.  The pathogen is known to cause serious plant losses by attacking primarily the roots and lower stems of plants.  Although it has a wide range of hosts, its main targets are herbaceous plants.  "R. solani" would be considered a basidiomycete fungus if the teleomorph stage were more abundant.  The pathogen is not currently known to produce any asexual spores (conidia), though it is considered to have an asexual lifecycle.  Occasionally, sexual spores (basidiospores) are produced on infected plants.  The disease cycle of "R. solani" is important in management and control of the pathogen.

Supporting paragraphs: Annie Gravatt Chestnut blight
Answer: Chestnut blight