Year of Publication

2010

Degree Name

Doctor of Philosophy (PhD)

Document Type

Dissertation

College

Agriculture

Department

Plant and Soil Science

First Advisor

Dr. Robert Geneve

Abstract

Eastern gamagrass [Tripsacum dactyloides (L.) L.] is a warm-season, perennial grass which is native to large areas across North America. Cultivars, selections and ecotypes suitable for erosion control, wildlife planting, ornamental, forage and biofuel applications are commercially available. Plantings are commonly established from seed; however, seed quality and dormancy are barriers to establishment. The objective here was to investigate parameters that contribute to inconsistent performance of this seed kind to subsequently improve seed lot quality.

Forty-two seed lots were used, with seed fill and germination potential ranging from 78- 100% and 11-91%, respectively. Actual germination and dormant seed ranged from 0-40% and 1-85%, respectively. Seed count per pound ranged from 3195 to 8344 and was influenced by genotype. Alternating laboratory temperature regimes were generally more effective in promoting germination than constant temperatures. Optimal germination occurred at 15/25, 20/30 or 20/35 ºC (16/8 hours), but was not consistent across cultivars or seed lots. These data suggest that germination temperature contributes to inconsistent laboratory germination and poor stands observed for untreated and pretreated seeds sown under field conditions.

Eleven primary dormancy breaking treatments were tested and most improved germination. Although not commercially feasible, cupule removal plus caryopsis scarification hastened germination and completely eliminated seed dormancy. Soaking in H2O2 (18 hr) improved germination, but the effect was not consistent. Moist chilling (5 or 10 °C) was generally superior to other treatments and remains the most simple, effective and consistent dormancy-breaking treatment, although duration varies by seed lot.

Benefits of moist chilling and H2O2 treatment were retained for short periods in seeds dried from approximately 55% to 13% moisture content. Removal of empty and light-weight cupules improved seed lot purity and germination, although removal of as much as 40% of the volume was necessary. The priming treatments tested were less than satisfactory in improving germination or the range of germination temperatures compared to moist chilling treatment alone.

Eastern gamagrass seed lot quality is highly variable, but can be improved. Multiple physical and physiological targets of opportunity have been identified to improve seed lot quality in eastern gamagrass.

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