Registration of NEWRC Red Clover Germplasm

NEWRC red clover (Trifolium pratense L.) germplasm (Reg. no. GP-21, P1 578052) was released jointly by the Florida Agricultural Experiment Station, the USDA-ARS, and the Wisconsin Agricultural Experiment Station in 1993. This germplasm has use in genetic transformation and breeding research. NEWRC was developed from the cultivar Arlington by applying five cycles of recurrent phenotypic selection for increased plant regeneration via somatic embryogenesis from callus tissue. A three-step tissue culture protocol was used (callus induction, embryo induction, and plant development) based on Gamborg's B5 basal salts, NAA (a-naphthaleneacetic acid), and 2,4-D [(2,4-dichlorophenoxy)acetic acid] as auxins and kinetin and adenine as cytokinins (1). Hypocotyl tissue was used as the explant in Cycles 1 and 2, whereas petiole tissue was used for Cycles 3, 4, and 5. Plants in each cycle were selected on the basis of plantlet regeneration frequency in culture. In Cycle 3, 4, and 5, only original explant source plants (rather than regenerated plants) were used for intercrossing. This was done to minimize any possible negative somaclonal variation that might have been introduced in the culture phase. Numbers of plants selected and intercrossed in each generation have been reported previously (2). The percent of NEWRC plants capable of regenerating is 72 in contrast to 4 in the original base population, Arlington. The NEWRC germplasm is in the second generation of synthesis (Syn 2). Fifty-three Cycle 4 plants were intercrossed to produce Cycle 5 (Syn 1). Approximately 3000 Syn 1 plants were then intercrossed in caged isolation in Prosser, WA, using honeybees (Apis mellifera Linnaeus) to produce NEWRC. In the developmental phase, the Syn 1 germplasm was designated RPS5. Since the original population was Arlington, the germplasm should have good general agronomic adaptation and relatively good resistance to the disease northern anthracnose [caused by Aureobasidium caulivora (Kirchn.) W.B. Cooke; syn. Kabatiella caulivora (Kirchn.) Karak]. Small quantities (up to 5 g) of seed of NEWRC are available upon written request to either author.