Date of Award

Spring 2012

Project Type


Program or Major

Plant Biology

Degree Name

Master of Science

First Advisor

Brent Loy


Interspecific hybrids derived from crosses of Cucurbita maxima Duch. x C. moschata Duch. have been utilized for taxonomic studies and introgression of advantageous traits, as well as for cultivation for fresh market squash. The present study involves the development and evaluation of C. maxima x C. moschata F1 hybrids for use as processing squash. Crosses were performed in the summers of 2009, 2010, and 2011 between inbred bush C. maxima breeding lines and vine C. moschata cultigens, and the resulting progeny were evaluated in the greenhouse and field in 2010 and 2011 for phenological growth traits, fruit traits, and fruit fresh and dry weight yields.

Compatibility between species was variable, but the C. maxima line NH65 was compatible with several C. moschata cultigens in terms of the ability to set fruit and produce abundant, viable seed.

In interspecific hybrids utilizing the C. moschata fresh market cultivar 'Waltham Butternut' (WBN), internode lengths resembled the bush parent (<2.0 cm) for the first three internodes but increased rapidly between nodes 4 and 7 and exceeded those in the vine parent (>17.0 cm) for several nodes. In hybrids between NH65 and the C. moschata processing cultivars 'Long Island Cheese' (LIC) and 'Dickinson Field' (DF), internode lengths did not exceed 5.0 cm until nodes 8 and 10, respectively, and mature internode lengths in these hybrids resembled, but did not exceed, those in the vine parents.

All interspecific hybrids observed were highly gynoecious. In the greenhouse, hybrids utilizing WBN produced precocious pistillate flowers below node 5, but pistillate flowering commenced later in hybrids 65xLIC (node 10) and 65xDF (node 14). Early flowering and fruit set in hybrids utilizing WBN resulted in suppressed vegetative growth in the field. The hybrids 65xLIC and 65xDF exhibited prolific leaf canopy formation prior to fruit set.

Fruit fresh weight in DF (12.1 kg) was significantly greater than that of the interspecific hybrids 65xLIC (4.1 kg) and 65xDF (7.1 kg), but mesocarp percent dry weight was higher in 65xLIC (9.3%) and 65xDF (7.7%) than in DF (5.6%). Additionally, fruit fresh weight yield in DF (48.1 mt/ha) was greater than in 65xDF (32.0 mt/ha) but similar to 65xLIC (46.6 mt/ha), and mesocarp dry weight yield in 65xLIC (3.9 mt/ha) was 50% greater than in DF (2.6 mt/ha).