WSU CAHNRS

College of Agricultural, Human, and Natural Resource Sciences

Department of Plant Pathology

Congratulations to Recent Grads

Amy Salamone completed the requirements for an M.S. degree from the Department of Plant Pathology, Washington State University (WSU).  Her graduate program committee included Debbie Inglis (chair), Tim Paulitz, Lori Carris, and Lynne Carpenter Boggs.  Her thesis was entitled “Effects of temporary flooding rotations on Rhizoctonia solani AG-3 and on soil bacterial communities in western Washington”.   Temporary flooding rotations (TFR) are sometimes employed in western Washington to enhance shorebird habitat and offer control of certain soilborne plant pathogens.  Amy investigated viability of R. solani AG-3 causing potato diseases under varying soil moisture conditions on naturally infected potato tuber discs and in inoculated soil in growth chambers.  She determined viability of R. solani on tuber discs and in inoculated soil, and found multiple incidences of mycoparasitism of R. solani by Bionectria spp. and other unidentified fungi.  She assayed survival and pathogenicity of R. solani in inoculated and non-inoculated field microplots under various flooding conditions by direct baiting and qPCR.  In addition, she also studied the effects of TFR on soil nutrients and properties.  Amy was raised in eastern Tennessee.  She received her B.S. degree in biology from Tennessee Technological University and a MS degree in coastal science from University of Southern Mississippi.  She came to WSU in January 2013 for her second M.S. degree in plant pathology.  At WSU, she was awarded the Alexander A. Smick Scholarship in Rural Community Service and Development in 2013. Amy plans to continue research on soil fungi and bacteria in Inglis’ vegetable pathology lab.

Danilo Isaac Vera Coello completed the requirements for a Ph.D. degree from the Department of Plant Pathology, Washington State University (WSU).  His program committee included Tim Murray (advisor), Dennis Johnson, Gary Grove, and Weidong Chen.   His dissertation was entitled “Role of the ascigerous stage in the epidemiology of eyespot in wheat”.  Eyespot is a chronic disease of winter wheat, caused by Oculimacula yallundae (OY) and O. acuformis (OA).  Discovery of the teleomorph of the fungal species in the US Pacific Northwest is relatively recent, and the role of apothecia in the epidemiology of eyespot is unclear.  Danilo’s finding of apothecia of OY and OA in spring and fall in commercial wheat fields demonstrates that sexual reproduction occurs regularly in the PNW and may play a role as primary inoculum in the eyespot disease cycle.  However, he found that apothecia survived over summer but not over winter in inoculated field plots.   He trapped ascospores of OY and OA in inoculated field plots during spring and fall and found no differences in the number of ascospores trapped from fields with a wheat crop or stubble.  He developed regression models based on the environmental variables for ascospore formation.  He found that inoculation of winter wheat and spring barley straw segments with a suspension of conidia or mycelial plugs favored apothecia development; however, mature apothecia did not developed in treatments without host substrate.  Danilo’s research provides a base-line offering new insights into the role of the sexual stage of Oculimacula spp.

David Linnard Wheeler completed the requirements for an M.S. degree from the Department of Plant Pathology at Washington State University (WSU).  His graduate program committee was composed of Dennis Johnson (Chair), Lori Carris, and Tim Murray.  His thesis was entitled “Verticillium dahlia asymptomatically and differentially infects rotation crops of potato in the Columbia Basin, Washington”.  David’s research was to test the hypothesis that rotation crops of potato and mint are asymptomatically infected by Verticillium dahliae by inoculation of rotation crops and isolation of V. dahliae from rotation crops grown in fields with a history of Verticillium wilt. He planted mustards, grasses, Austrian winter pea, mints, and potato in soil infested with eight isolates of V. dahliae, grew them to senescence, and estimated inoculum density of V. dahliae from plants and soil on a semi-selective medium.  He found at least one isolate from all asymptomatic rotation crops, significant crop by isolate interactions, different inoculum density among rotation crops and isolates, and effects of infection on plant biomass in specific treatments.  From commercial fields, he detected V. dahliae in rotation crops from 8 of 21 surveyed commercial fields.  His results show that specific rotation crops are asymptomatically and differentially infected by V. dahliae.  David grew up in southeastern Pennsylvania and received his BS degree in horticulture from Temple University.  At WSU, David received the Everett and Helen Kreizinger Scholarship.  He will continue studying under Dennis Johnson’s guidance for his Ph.D. at WSU.

Elizabeth Kramer completed the requirements for her M.S. degree in plant pathology at Washington State University (WSU).  Her thesis was entitled “Interactions of wild vineyard yeast with Botrytis cinerea and sensitivity to select fungicides in vitro”.  Her committee included Dean Glawe (chair), Weidong Chen, Charles Edwards, and Lee Hadwiger.  Botrytis cinerea can produce significant reductions in fruit yields and quality in Washington vineyards.  Elle screened 50 wild yeast strains from a vineyard near Prosser, WA for suppressive activity against B. cinerea.  She found that 32 strains exhibited some inhibition of B. cinerea growth, including 11 highly suppressive strains, Candida saitoana, Metschnikowia chrysoperlae, M. pulcherrima, Aureobasidium pullulans var. pullulans, Curvibasidium pallidicorallinum, Meyerozyma guilliermondii, and Wickerhamomyces anomalus. She evaluated these strains for sensitivity to fungicides commonly used in Washington vineyards, and found them highly resistant to most fungicides. She also tested the yeast strains on detached grape berries for ability to reduce lesion size by B. cinerea.  Her study provides evidence that some naturally-occurring yeast strains from vineyards could be of possible use in managing Botrytis Bunch Rot of grape. Her results also suggest that the use of naturally-occurring yeasts to help suppress B. cinerea could be compatible with fungicide-based strategies to manage powdery mildew in in vineyards.  Elle grew up in Duluth, MN and received her B.S. degree in plant biology from the University of Washington in 2008. Before joining WSU in 2012, she was Field Botanist with the US Department of Interior. She is Lead Biologist in NorthStar Technologies.

Hui Yan completed the requirements for his Ph.D. in plant pathology at Washington State University.  His dissertation was entitled “effects of meteorological factors on conidia infection and production of Erysiphe necator, Podosphaera clandestina, and Podosphaera macularis on the leaves of grape, cherry, and hop”.  Hui’s major professor was Gary Grove, and his committee also included David Gent (USDA-ARS, Corvallis, OR), Dennis Johnson, and Naidu Rayapati.  Powdery mildews are common problems on grape, cherry, and hop in Washington State.  He determined optimal conditions for conidial sporulation of P. clandestine on cherry.  He conducted similar experiments to determine effects of RH on sporulation of P. macularis conidia at 20°C, and found a significant negative linear relationship between harvested conidia and RH at 80-97.5% during 48 h incubation. In the experiments of ultraviolet radiation (UV), he found that low levels of UV resulted in higher population of E. necator conidia, while high UV had the opposite effect, and determined the thresholds of UV-A and UV-B.  He described the negative relationship of UV with conidia concentration in current day (lag0) and the previous two days (lag2) using cross correlation analysis. He developed three dynamic prediction models of E. necator, P. clandestina, and P. macularis. This study suggested that the understanding of relationship between weather variables and conidia concentration could improve the management of powdery mildew on gape, cherry and hop.  Hui grew up in China, and received his M.S. in statistics from the University of Idaho in 2008.

Jinita Sthapit completed the requirements for her Ph.D. in plant pathology at Washington State University. Her dissertation was entitled “Wheat landraces for novel resistance to biotic and abiotic stresses”.  Her committee included Deven See (chair), Scot Hulbert, Xianming Chen, and Michael Pumphrey.  In her studies, she identified 165 accessions resistant to stripe rust and 30 of them also resistant to stem rust.  She used single-nucleotide polymorphism (SNP) markers grouped resistant landraces into different clusters and identified genetically distinct resistant genotypes indicating potentially diverse resistance genes. She developed recombinant inbred lines from crosses of four resistant landraces with a susceptible spring wheat genotype. By phenotyping the populations for stripe rust responses and genotyping with genotyping-by-sequencing and microsatellite markers, she mapped one to five quantitative trait loci for resistance to stripe rust in the four landraces.  With winter wheat germplasm, she identified a cluster of 553 landraces from regions of >40°N using SNPs. Through testing freezing tolerance using electrolyte leakage on 192 landraces, she found that greater freezing tolerance is in landraces from higher latitudes. She identified two chromosomal regions contributing to the adaptation to higher latitudes and conferring freezing tolerance using the genome-wide association study approach. Jinita grew up in Kathmandu, Nepal. She received her B.S. in biology in 2000 and M.S. in botany in 2010 from Tribhuvan University, Nepal, and M.S. in plant pathology from the University of Arkansas in 2010.  She was an assistant lecturer in National Multiple College, Nepal in 2003-2007.

Phuong Dinh completed the requirements for her Ph.D. in plant pathology at Washington State University. Her dissertation was entitled “Plant nematode interaction and the application of RNA interference for controlling root-knot nematodes (RKN)”.  Phuong’s advisors were Axel Elling and Debbie Inglis, and her committee also included Kiwamu Tanaka, Lori Carris, and Charles Brown. Phuong developed a novel, nondestructive technique to observe the progression of nematode pathogenesis in planta. She found that overexpression of 16D10, a highly conserved RKN effector in Arabidopsis thaliana, enhanced susceptibility of A. thaliana to Meloidogyne incognita. She cloned an ortholog of 16D10, Mc16D10L, from M. chitwoodi. By silencing Mc16D10L using plant-mediated RNA interference (RNAi), she observed significant reduction of M. chitwoodi race 1 reproduction in A. thaliana and potato plants. Introducing 16D10 RNAi into potato breeding line PA99N82-4 also decreased reproduction of M. chitwoodi pathotype Roza. The RNAi effect of Mc16D10L was transmitted to M. chitwoodi offspring, and significantly reduced pathogenicity of nematode offspring on non-RNAi plants. The potato RNAi line D21 further proved resistant to M. incognita, M. javanica, M. arenaria, and M. hapla. Her results show that plant-mediated 16D10 RNAi offers a promising new tool for molecular breeding against RKN in potato. Phuong was from Vietnam.  She received her B.S. in biotechnology from Vietnam National University in 2004 and M.S. in plant biology from Massey University, New Zealand in 2009.  She was research assistant in Southern Horticultural Research Institute, Vietnam 2004-2007 and 2009-2010.  Phuong works in the institute as plant pathologist.

Wonyong Kim completed the requirements for his Ph.D. in plant pathology at Washington State University. His dissertation was entitled “Functional characterization of polyketide-derived secondary metabolite solanapyrones produced by the chickpea blight pathogen, Ascochyta rabiei: genetics and chemical ecology”.  His committee included Weidong Chen (chair), Lee Hadwiger, George Vandemark, Tobin Peever, and Ming Xian. Solanapyrone A has long been considered a key virulence factor in the chickpea-A. rabiei interaction, due to its phytotoxicity to chickpea.  To determine the role of solanapyrones during infection process, Wonyong generated solanapyrone-minus mutants from A. rabiei strains of different pathotypes. He examined the phytotoxicity of solanapyrones with various legumes including chickpea plants with varying degree of resistance to the disease and expression levels of solanapyrone genes. He found that purified solanapyrone A has a broad spectrum of phytotoxicity, causing necrotic lesions on all tested plants. His results indicate that solanapyrone A is neither a host-selective toxin nor a virulence factor of A. rabiei. To investigate ecological roles of solanapyrones, he co-cultured wild-type strains or solanapyrone-minus mutants with saprobic fungi that have been isolated from chickpea debris left in a field. Wild-type strains effectively suppressed the growth of the saprobic fungi, whereas solanapyrone-minus mutants did not. These results suggest that solanapyrone A plays an important role in competition and presumably in survival of the pathogen in nature.  Wonyong was from South Korea.  He received his B.S. in agronomy in 2007 and M.S. in plant biotechnology in 2009 from Chonnam National University, South Korea.

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