Undergraduate Research

2015 - Denman Undergraduate Research Forum, The Ohio State University

Pathogenic effects of Magnaporthe oryzae pectin lyase 1 on resistant rice
Zachary Foust (Plant Health Management major), Dominique Tate and Thomas K. Mitchell

Magnaporthe oryzae is the causal agent of Rice Blast, one of the most destructive diseases affecting worldwide rice production. Nearly 60% of the rice grown every year is lost to this disease. In previous studies, it has been shown that overexpression of M. oryzae pectin lyase 1 (Mopln1) allowed the fungus to overcome the resistance gene in the Pi-2 rice line. Very few lines of rice are resistant to Rice Blast, however, these lines may not be resistant to all M. oryzae isolates. The main objective of this study is to investigate if the overexpression of Mopln1 affects the ability of the fungus to cause disease in various other rice lines. Wild-type M. oryzae, KJ201, has been transformed to express Mopln1 either with its native promoter or with constitutive ribosomal promoter 27 (RP27). Spores from these transformants and wild-type lines were sprayed individually on five sets of ten different rice lines grown separately on MS media in sterile test tubes. Still a work in progress, preliminary findings suggest that overexpression of Mopln1 causes normally resistant rice lines to become more susceptible to Rice Blast. Based on these findings, Mopnl1 may be critical to the pathogenicity of M. oryzae and its ability to overcome resistance. Mutations can occur quickly in fungi and M. oryzae is no exception. This gene could mutate quickly in the wild and a staple food crop would be lost, leaving millions to starve. (Biological Sciences category)

Analysis of Macrophomina phaseolina infection levels on inoculated soybean seedlings
Ambria Small (Plant Health Management major), Horacio Lopez Nicora and Terry L. Niblack

Macrophomina phaseolina is a fungal pathogen that causes charcoal rot on soybean and on approximately 500 other plant species.1 Charcoal rot is a major problem on soybean in the growing areas of the US. In 2007, US soybean production suffered about 25.1 million bushel yield loss.2 A technique that can allow us, under controlled conditions, to measure disease severity and eventually screen for resistant soybean cultivars will be tremendously beneficial. The goal of this study was to improve an inoculation technique. To do this, optimum levels of M. phaseolina that would produce quantifiable levels of infection in soybean seedlings were determined. Soybean seeds were planted and inoculated with M. phaseolina infested millet at different levels. Treatments were 0, 3, 5, and 10 grams of millet; additionally 5 grams of autoclaved, non-infested millet was used as a control. The 0 gram of millet treatment had no millet. Seven days after planting, emergence was recorded; seedlings harvested and wet and dry weight were collected. After allowing seedlings to air dry they were ground and plated onto potato dextrose agar (PDA) plates. Colony forming units (CFU) were counted after 5 days. The optimum level of inoculum was 5 grams of M. phaseolina infested millet seed. This inoculum level allowed us to detect and quantify the pathogen seven days after inoculation. Results generated in this study can be used to improve an existing inoculation technique and to answer more questions about this pathogen and its interaction with soybean. (Food, Agricultural, and Environmental Sciences category)

Survey of endophytic fungi of the phyllosphere in apple and crabapple

Christina Tomashuk (Plant Pathology major), Hannah Reynolds and Jason Slot

All lifeforms live side by side with beneficial and pathogenic microbes.  Many studies have been conducted on the rhizosphere of apples; however, few have studied the microbes of the phyllosphere.  We hypothesized that endophytic fungi from apple flowers and twigs would vary according to host tissue and variety. Gold Rush (apple), Enterprise (apple), and Prairie Fire (crabapple) were sampled from an organic orchard at Charlie's Apple Farm in early May, 2014.  Out of 528 total isolates, 146 morphological types were sorted based on color and culture growth pattern. Common morphotypes – those isolated at least 10 times -- were recovered from both twigs and flowers.  Overall, 102 (60%) of the morphotypes belonged to only a single tree variety whereas 44 (40%) morphotypes were shared between at least two varieties.  Using PCR and sequencing of the internal transcribed sequence (ITS), twelve samples recovered from multiple tree varieties and tissues were identified from six ascomycete fungal families from two classes: Pleosporaceae and Botryosphaeriaceae from the Dothideomycetes, and Xylariaceae, Diaporthaceae, Hypocreaceae, and Glomerellaceae from the Sordariomycetes.  While the species of most of the isolates could not be determined, several of them are closely related to fungi that cause important diseases, including Alternaria Leaf Blotch, Core Rots, and Root Rots.  Understanding the species that live on apples and their interactions with each other will help in developing management strategies for possibly pathogenic species. (Food, Agricultural, and Environmental Sciences category)