Seed dormancy, germination and fungal infestation of eastern gamagrass seed

Eastern gamagrass [Tripsacum dactyloides (L.) L.] is a US native perennial warm-season grass. Commercial seed lots commonly have low percentage germination with high levels of dormant seed. This study was conducted to develop technologies to break seed dormancy and enhance germination and seedling survival of eastern gamagrass in laboratory germination tests. Germination tests for all seed treatments were conducted at alternating temperatures of 20/30 °C with corresponding dark/light cycles consisting of 16 and 8 h, respectively. A method of physically removing the caryopsis from the cupule and then scarifying the caryopsis was previously described in the literature and termed scarified caryopsis (SC). Our research program developed a one-step method of simply grinding off the top of the seed, termed cupulated caryopsis top removal (CCTR). The CCTR treatment breaks the integrity of both the cupule and pericarp. Intact cupules and non-scarified caryopses of eastern gamagrass seed lots had high percentages of dormant seed, whereas the CCTR and SC treatments evaluated in this study reduced or even eliminated dormancy. Additionally, stratification for 8 or 12 weeks respectively broke dormancy of intact cupules of the two seed lots tested. Stratification followed by drying or drying + storage for four weeks caused dormancy reversion; however, reversion did not occur in the CCTR treatment. Seed contamination was evaluated in four seed lots. Chaetomium, Pithomyces and Rhizopus were detected in all seed lots. The fungicide seed treatments captan and thiram significantly reduced germination of CCTR treatments in comparison with the non-fungicide treated control. The combination of pyraclostrobin and fluxapyroxad seed treatments had the best control of fungal seed contaminants and final percentage germination in laboratory germination tests.