ABSTRACT
In the early 1990s, the US DOE identifi ed switchgrass (Panicum Virgatum L.) as an herbaceous energy crop and launched research efforts on switchgrass as a biomass energy feedstock (McLaughlin and Kszos 2005). Conger’s laboratory at the University of Tennessee was the pioneer in tissue culture and genetic transformation research on switchgrass. Their fi rst report on callus induction and plantlet regeneration was published in 1994 (Denchev and Conger 1994). Mature caryopses, along with young leaf segments from newly-formed shoots of secondary tillers (lowland cv. Alamo), were used as explants and cultured on MS medium supplemented with auxin, 2,4-D (22.5 µM, or 5 mg/l), and cytokinin, 6-benzylaminopurine (BAP, 45 µM, or 10 mg/l, for mature caryopses and 5 µM, or 1.1 mg/l, for young leaf segments). Mature caryopses cultures were maintained in the dark at 29°C for 4 wk, and callus and “organized structures” were observed. They
1Department of Horticulture, Virginia Tech, Blacksburg, VA 24061. 2Department of Crop Science, North Carolina State University, Raleigh, NC 27695. *Corresponding author: bzhao07@vt.edu
were transferred to MS medium without growth regulators and placed under light. Approximately 65 percent of the calluses regenerated into plants. For young leaf segment cultures exposed to the same conditions, embryogenic calluses originated from basal segments of innermost leaf pieces. Non-embryogenic calluses were produced from the remainder of the leaf segments. Histological and scanning electron microscopy (SEM) analyses indicated embryogenesis was the main pathway for regeneration from mature caryopses culture, whereas regeneration from leaf segment cultures was mostly through organogenesis. One thousand regenerated plants were obtained and grown in the fi eld.
