Degree Name

Master of Science (MS)

Semester of Degree Completion

2016

Thesis Director

Scott J. Meiners

Abstract

Production of hazelnuts has historically been limited to regions with mild climates, with almost all hazelnut production in the United States occurring in Oregon. A recent boom in demand, along with an expanded selection of varieties with improved environmental tolerances, has pushed hazelnut production into new regions. Hazelnut production could prove profitable in areas of the Midwest that are less well-suited to the cultivation of maize and soybeans. However, the lack of varieties proven to thrive in the climatological conditions of this region (cold winters, hot summers, frequent drought) presents a barrier to the viability of hazelnut production. A trial orchard was established in east-central Illinois to test the performance of seven hazelnut varieties, with a focus on issues present during orchard establishment. The orchard included five cultivars (Carmela, Gene, Matt, Slate, and Redleaf) and two seedling lines (NY and Precocious). To determine their suitability, I followed several traits that can be affected by climatological conditions: winter damage, flowering phenology, and extension growth. Additionally, I evaluated drought stress by assessing stomatal characteristics associated with drought resistance alongside quantitative measurements of plant stress through the chlorophyll fluorescence parameters Fv/Fm and PIABS.

Flowering occurred in the orchard between mid-March and early April, 2015. There was overlap in the flowering windows for both genders of all varieties, a promising sign for fertilization and nut set in mature plants. Winter damage and extension growth proved more problematic. Winter damage decreased from 2014 to 2015, but this decrease was likely due to more mild temperatures in the latter year, and cannot be contributed to plant maturity alone. The majority of extension growth occurred in the orchard before water became limiting in August. Only two varieties, NY and Redleaf, showed continued growth during the dry late season. As vegetative growth is linked to reproductive output, a combination of winter stem death and limited summer growth could lead to decreased yields in certain varieties at maturity.

Stomatal density differed significantly among varieties and correlated positively with growth. Fv/Fm and PIABS peaked in early August and declined until senescence due to the combined influence of leaf age, high temperature, and limited rainfall. Surprisingly, there was an additional depression in fluorescence parameters early in the season during a period of high rainfall. Hazelnuts are generally considered to be flood tolerant, so stress in response to high soil moisture content was unexpected. During the dry period, fluorescence parameters correlated negatively with growth, which is evidence of higher stress in plants with greater growth. Use of orchard sites with adequate drainage, late summer irrigation, and selection of varieties tolerant of the Midwestern climate will prove key in successful orchard establishment. Taken together, these results represent a groundwork for future hazelnut production in this region, with further study necessary as this orchard matures and bears fruit.

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