Date of Award

Winter 2012

Project Type

Dissertation

Program or Major

Plant Biology

Degree Name

Doctor of Philosophy

First Advisor

J Brent Loy

Abstract

A comprehensive study at the New Hampshire Agricultural Experiment Station (NHAES) of 16 winter squash cultigens (Cucurbita spp.), including inbred lines and open pollinated and F1 hybrid cultivars from the University of New Hampshire breeding program, was undertaken to determine dry weight (%DW), soluble solids contents (%SSC) and carotenoid contents of mesocarp tissue, major attributes for determining acceptable eating quality and nutritional content. Data were recorded at harvest, either 40 or 60 days after pollination (DAP), and after 30 and 60 days of storage at 14 °C. Carotenoid contents were determined spectrophotometrically and using high performance liquid chromatography (HPLC).

The %DW in Cucurbita maxima cultigens at harvest ranged from 21.2% to 29.0%, and decreased after 30 and 60 days of storage. The %DW in Cucurbita moschata cultigens at harvest ranged from 13% to 23.1% and decreased slightly but differences were not statistically significant. The mean SSC for all Cucurbita maxima cultigens increased from 10.1% at 40 DAP to 12% at 60 DAP with little change. Mean %SSC for Cucurbita moschata cultigens at harvest were 7.4% at 40 DAP and 8.7% at 60 DAP and 11.5% after 60 d in storage.

Carotenoid content at harvest among Cucurbita maxima cultigens ranged from 146 to 320 mug/g FW; whereas, after 60 d of storage, carotenoid content was 274 to 623 mug/g FW. Among Cucurbita moschata cultigens carotenoid content ranged from 43 to 157 mug/g FW, lower than in Cucurbita maxima cultigens, yet Cucurbita moschata cultigens had a much higher proportion of nutritionally important carotenoids. beta-carotene, lutein, and neoxanthin were the predominant carotenoids identified in both winter squash species using HPLC. Lutein and zeaxanthin were present in the Cucurbita maxima cultigens and violaxanthin and alpha-carotene were present among Cucurbita moschata cultigens.

Among eight sweet potato cultigens (Ipomoea batatas) in this study, five orange-fleshed cultigens had increased carotenoid content at harvest, 78 to 137 mug/g FW whereas carotenoid content ranged from 0 to 25 mug/g FW in the cream and white-fleshed cultigens. beta-carotene was the main carotenoid, comprising 92% of the profile in all cultigens. Total carotenoid content in 'Georgia Jet' and 'Beauregard' increased 12 and 35% respectively during storage (38 days).

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