Selection and Breeding to Eliminate Seed Dormancy in Eastern Gamagrass.

Eastern gamagrass is a hearty, long-lived perennial warm-season native grass.  The species has been utilized for forage, wildlife, bioenergy, riparian buffer, and ornamental purposes.  The most valuable and applicable of these purposes is as a forage crop, most effectively utilized as a grazing or hay crop.  The major impediments to more widespread use of eastern gamagrass are its hard seed coat and deeply dormant embryo, which cause delayed germination, emergence and establishment.  Eastern gamagrass seed units are large, woody cupules that encapsulate the embryo and endosperm.  These seed units have been shown to exhibit physical, mechanical and physiological dormancy.  The standard practice for treating gamagrass seed prior to planting involves six to eight weeks of cold, moist stratification followed by applications of fungicide and, often hydrogen peroxide.  A research study was designed in 2011 to eliminate physiological dormancy from eastern gamagrass via recurrent phenotypic selection breeding.  Seedlots of commercial diploid varieties were collected, along with local accessions, and screened for rapid germination without the necessity for prior treatment.  Seed were placed on two thicknesses of blue blotter paper and maintained in environment-controlled chambers alternating temperatures of 30°C with light for eight hours and 20°C without light.  Seed that germinated in six days or less were kept and maintained in a greenhouse for breeding population establishment.  Seedling plants were monitored and scored for vigorous growth throughout the vegetative stage and physiological characteristics desirable for forage and seed production.  Desirable individuals were space-planted in April, 2012 at the R.R. Foil Plant Science Research Center in Starkville, MS.  Seed were harvested sequentially, and were stored until November, 2012.  Subsequent germination and selection has led to three established breeding populations, representing four cycles of selection.  Initial 6-day germination of non-stratified base population seedlot was <0.001%, whereas mean 6-day germination of Gen₁ seedlot was 2.7%.