Diagnostic Walkabouts: Seventeen Years of Specialized Training for Horticultural Professionals

A diagnostic walkabout (DW) is an in-field diagnostic training program for professionals in the green industry (greenhouse, landscape, nursery, and turf businesses). DWs have been scheduled annually since 2002 and are easily replicable, fee-based programs that provide cost recovery. DWs also serve as a mentoring program for new Extension educators. Four generations of Extension Educators have participated. Recently, the annual program has been sponsored by state and regional trade associations. What began as an educational outreach program has become a bridge spanning Extension, trade associations, businesses, and generations of Extension educators

Intraspecific Variation In Freshwater Fishes; Insights Into Trophic Relationships, Morphology and Bioaccumulation

Individuals within fish populations differ in many traits, such as sex, life-history, habitat residence, diet, and morphology. Such trait differences among individuals (i.e. intra-population variation) may be greater than the differences among populations (i.e. inter-population variation). My dissertation examines intra-population variation, with a focus on trophic relationships and morphology; as well as how variation in these attributes may reflect differences in bioaccumulation of contaminants. The second chapter of my dissertation examines the influence of spatial-temporal variation on the trophic structures of round goby (Neogobius melanstomus) and two age classes of yellow perch (Perca flavescens) within Saginaw Bay, Lake Huron. Using stable isotope ratios (δ13C, δ15N, δ2H, δ18O) and stomach contents as trophic indicators, I examined variation of diets. I found that spatial variation had a greater impact on diet indicators than both annual and seasonal variation. This spatial variation could represent a form of compartmentalization within the community of fish residing in Saginaw Bay, and could provide stability to the community. Chapter three of my dissertation examines intra-population variation in yellow perch morphology through a series of mesocosm experiments. My first mesocosm study determined that yellow perch could be experimentally manipulated to display divergent morphologies using simulated habitats, specifically pelagic and littoral habitats. Following this experiment, I focused on specific environmental drivers (structure, prey resources, and predation risk) as possible influences on yellow perch morphology. Within experimental pools, I exposed yellow perch to one of four treatments (an open pool, a structured pool, pools with chironomid prey resources and pools with a perceived, olfactory, predation risk) in the summer of 2015. Following exposure to these treatments I examined the morphological changes in yellow perch in magnitude and direction. I observed that while each treatment induced some difference in morphology, the open and structured treatments had the greatest magnitude of difference. I repeated the open and structure treatments during the following summer (2016). Again, I found that structure and open morphologies could be induced by my mesocosm treatments, but also observed that shapes differed from the previous year’s structure and open treatments. Finally, my fourth chapter examined how variation in trophic niches and morphology may reflect variation in contaminant concentration of fish in their natural environment. In this chapter, I extended my work with yellow perch to also include black crappie (Pomoxis nigromaculatus) and examined fish from 5 northern Indiana glacial lakes. Using model inference techniques, I found that variation in mercury was closely associated with not only fish total length, but also stable isotopes (δ 13C and δ 15N) and morphology. Interestingly, morphology-related variables of both species were strong predictors of mercury concentration in fish, following total length. Together, the chapters within my dissertation highlight the importance of considering intrapopulation variation, in which local factors such as habitat conditions and prey availability can influence individual variation in trophic structuring and morphology. These in turn may reflect other attributes of interest, such as the accumulation of contaminants

Interacting effects of identity, size, and winter severity determine temporal consistency of offspring phenotype

Offspring size can strongly influence offspring fitness; however, the importance of female identity to offspring size determination is poorly understood, despite the potential for identity effects to drive offspring size adaptation and population dynamics. We tracked reproductive investment (skein mass) and mean egg diameter, mass, and density produced by individual female yellow perch (Perca flavescens) over four spawning years to determine the influences of maternal identity, size, and winter severity to reproductive trait variation. Individual identity significantly influenced egg diameter and mass, but did not affect egg density or skein mass. All egg traits were negatively influenced by winter severity prior to spawning, and egg mass and diameter were also negatively related to maternal size. Our results suggest that individual effects can comprise a large amount of the intrapopulation variation in reproductive traits in populations, which may be unaccounted for in studies examining only environmental or phenotypic effects. Accounting for potential identity effects would likely improve our understanding of constraints on offspring size plasticity and potential responses of offspring size in populations experiencing environmental change.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Differential expression analysis of Trichoderma virens RNA reveals a dynamic transcriptome during colonization of Zea mays roots

Abstract Background Trichoderma spp. are majorly composed of plant-beneficial symbionts widely used in agriculture as bio-control agents. Studying the mechanisms behind Trichoderma-derived plant benefits has yielded tangible bio-industrial products. To better take advantage of this fungal-plant symbiosis it is necessary to obtain detailed knowledge of which genes Trichoderma utilizes during interaction with its plant host. In this study, we explored the transcriptional activity undergone by T. virens during two phases of symbiosis with maize; recognition of roots and after ingress into the root cortex. Results We present a model of T. virens – maize interaction wherein T. virens experiences global repression of transcription upon recognition of maize roots and then induces expression of a broad spectrum of genes during colonization of maize roots. The genes expressed indicate that, during colonization of maize roots, T. virens modulates biosynthesis of phytohormone-like compounds, secretes a plant-environment specific array of cell wall degrading enzymes and secondary metabolites, remodels both actin-based and cell membrane structures, and shifts metabolic activity. We also highlight transcription factors and signal transduction genes important in future research seeking to unravel the molecular mechanisms of T. virens activity in maize roots. Conclusions T. virens displays distinctly different transcriptional profiles between recognizing the presence of maize roots and active colonization of these roots. A though understanding of these processes will allow development of T. virens as a bio-control agent. Further, the publication of these datasets will target future research endeavors specifically to genes of interest when considering T. virens – maize symbiosis

Probiotic strain Stenotrophomonas acidaminiphila BJ1 degrades and reduces chlorothalonil toxicity to soil enzymes, microbial communities and plant roots

Abstract Chlorothalonil, a non-systemic and broad-spectrum fungicide, is widely used to control the pathogens of agricultural plants. Although microbial degradation of chlorothalonil is known, we know little about the colonization and degradation capacity of these microbes in the natural and semi-natural soil environments. Therefore, we studied the colonization and detoxification potential of a chlorothalonil degrading Stenotrophomonas acidaminiphila probiotic strain BJ1 in the soil under green conditions. The results from polymerase chain reaction-denaturing gradient gel electrophoresis demonstrated that probiotic strain BJ1 successfully colonized the soil by competing with the native biota. Moreover, the bacterial inoculation stimulated some members of indigenous soil microbial communities. Meantime, the degradation half-life of chlorothalonil decreased from 9.0 to 4.9 days in the soil environment. Moreover, the results from enzymatic activities and micronucleus test of Vicia faba root tips showed that the probiotic strain BJ1 reduced the ecotoxicity and genotoxicity of chlorothalonil in the soil. We suggest that probiotic strains like BJ1 could potentially alleviate the toxic effects of pesticides on soil microbes and plant roots under greenhouse conditions