Date of Award

Summer 8-19-2016

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Horticulture

Advisor

Bryan J. Peterson

Second Committee Member

Stephanie E. Burnett

Third Committee Member

Christopher S. Campbell

Abstract

Amelanchier is a genus in the Rosaceae containing shrubs and trees indigenous to North America that possess traits valued by the horticulture industry. Amelanchier spicata (dwarf serviceberry), a heterogeneous complex of hybrids indigenous to eastern North America, has agricultural and ornamental merit with notable characteristics. White blossoms emerge in early spring, edible pomes ripen in the summer, and vibrant, orange foliage occurs in the fall. I investigated phenological and physiological factors influencing adventitious rooting of stem cuttings, the effects of nitrogen source on the development of seedlings grown in container culture, and phenotypic variation among seedlings of A. spicata from several provenances.

Over a two-year period, I evaluated the effects of hormone carrier, auxin concentration, wounding, and collection date on adventitious rooting of softwood and semi-hardwood stem cuttings. In 2014, softwood cuttings collected from two provenances in Maine were wounded by one-sided scraping and treated with K-IBA in water or IBA dissolved in 50% ethanol at concentrations of 0, 3000, 5000, or 8000 mg·L-1. There were no significant differences in rooting across hormone concentrations or carriers but cuttings treated with auxin had greater rooting percentage (75% vs. 50%) and root quality (2.3 vs. 1.1 out of five) compared with water and ethanol controls. In 2015, softwood or semi-hardwood cuttings were collected from one provenance in Maine on 17 June, 30 June, 14 July, and 29 July. Half of the cuttings received additional wounding by one-sided scraping and all were treated with K-IBA in concentrations of 0, 1000, 3000, and 5000 mg·L-1. Wounding always promoted greater rooting percentages and root ratings for all hormone concentrations. Wounded cuttings in a softwood condition had 93% rooting compared with 47% rooting for wounded semi-hardwood cuttings. The greatest average root quality resulted from wounded cuttings collected 14 July and treated with 5000 mg·L-1 K-IBA.

In 2015, we assessed the effects of nitrogen source (NH4-N, NO3-N, or NH4NO3-N) on the growth of A. spicata seedlings from four provenances in Maine and New Hampshire. Plants in container culture were grown for 61 days in a medium of 1:1 perlite:vermiculite, receiving nutrients in a modified, balanced Hoagland’s solutions that varied by nitrogen source. In addition to nitrogen form, we adjusted fertilizer solutions to pH 4.5 and 6.5 to establish a factorial with six treatment combinations. Substrate pH measured during the study varied by nitrogen form and was not influence by solution pH. Although there were significant differences in stem caliper, stem dry weight, leaf number, and SPAD across nitrogen forms, plant growth was uniform, indicating that either NH4-N or NO3-N is suitable for commercial production of A. spicata. In contrast, seedlings from different provenances varied greatly by stem dry weight, leaf dry weight, root dry weight, foliar nutrient concentration, stem caliper, stem length, leaf number, and SPAD. Moreover, phenotypic traits such as leaf and stem morphology were distinctly different among provenances. Our results indicate that there is much variation in the growth traits of A. spicata derived from different provenances, even on a localized spatial scale, and further evaluation of germplasm is merited.

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