Plant Science & Landscape Architecture Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2797
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Item Evaluation of Raspberry (Rubus sp.) Genotypes for Postharvest Quality and Resistance to Botrytis cinerea(2012) Harshman, Julia Mae; Walsh, Chris S; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Raspberries are a delicate, high value specialty crop with an extremely short shelf life. This is exacerbated by their susceptibility to postharvest decay caused by Botrytis cinerea. Of the three commercially available species, red raspberry (Rubus idaeus L.) is the most widely grown. Yellow (R. idaeus L.), black (R. occidentalis L.) and purple raspberries (R. × neglectus Peck.) are mainly available from direct marketers. The quality and storageability of 17 cultivars was examined weekly from June to September during two growing seasons. Storage life was assessed weekly, while firmness, color, respiration and ethylene evolution rates were measured in select harvests. Black and purple raspberries outperformed red and yellow cultivars in their ability to resist B. cinerea colonization. Black raspberries also had the lowest ethylene evolution rates and incidence of decay. This information will be useful to raspberry breeding programs by identifying physiological characteristics that are correlated with greater resistance to B. cinerea.Item Physiological and Molecular Studies of Ethylene Effects on Soybean Root Infection by Soybean Cyst Nematodes(2007-12-10) Xue, Ping; Solomos, Theophanes; Tucker, Mark L.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Soybean cyst nematode (SCN), Heterodera glycines, is one of the most devastating pests of soybean in the world. Several earlier reports demonstrated that ethylene is involved in nematode feeding cell formation in Arabidopsis and tomato. I investigated whether or not ethylene is involved in SCN feeding cell formation in soybean. My results show that SCN parasitism was increased by treatment of roots with ethylene and inhibited by suppressors of ethylene action or in an ethylene resistant soybean mutant. My results also indicate that excised soybean roots colonized by SCN produced ethylene at 1.5-3 times the rate of non-infected roots between 14 and 22 days post inoculation. To determine if ethylene was being synthesized in feeding cells, an ethylene-responsive promoter fused to a GUS reporter gene was constructed and transformed into soybean roots with Agrobacterium rhizogenes. Overall, the results suggest that ethylene plays an important role in SCN infection in soybean