Registration of Four Alfalfa Germplasm Pools Selected for Ease of Floret Tripping

Alfalfa (Medicago sativaL.) germplasm UCS AR-ET(L)2 (Reg. no. GP-287, P1 591467), UCSAR-ET(H)2 (Reg. no. GP-288, P1 591468), UCCUF-ET(L)2 (Reg. no. GP-289, P1 591469), and UCCUF-ET(H)2 (Reg. no. GP-290, P1 591470) were released by the Dep. of Agronomy and Range Science and the California Agricultural Experiment Station in May 1992. The Univ. of California [UC] identification numbers for the four pools are UC-1661, UC-1662, UC-1663, and UC-1664, respectively. UCSAR-ET(L)2 and UCSAR-ET(H)2 were selected from 'Saranac' and are easy and hard to trip, respectively. Both populations were developed by two cycles of phenotypic recurrent selection conducted under glasshouse conditions at Davis, CA (1,2). Ease of tripping was determined by evaluating four florets on each of two racemes per plant, using an electronic tripping meter (3). In Cycle 1, the 45 easiest-to-trip and 45 hardest-to-trip plants were selected from a population of 215 plants of Saranac. Within selection types, plants were intercrossed by hand pollination without emasculation and the resulting seed was harvested and bulked. Cycle-2 populations were developed by evaluating 308 easyand 285 hard-to-trip Cycle-1 plants and selecting the 45 easiestand 45 hardest-to-trip plants, respectively. Individuals selected within each of the populations were intercrossed and seed was harvested as before to produce Cycle 2. Easyand hard-to-trip Cycle-2 populations were significantly (P < 0.05) different from Saranac in glasshouse evaluations conducted during October 1991. UCS AR-ET(L)2 required 20% less force, and UCSAR-ET(H)2 required 12% more force to induce tripping than Saranac (2). Two years of field testing at Davis, CA, demonstrated a significant (P < 0.05) response to selection in both populations. However, the average differential in force required to induce tripping between the easy-to-trip (-6%) and the hard-to-trip (+8%) population and Saranac was less pronounced than in the glasshouse. Seed production, forage yield, and pest and disease reactions of these populations have not been determined. UCCUF-ET(L)2 and UCCUF-ET(H)2 were selected for easy and hard floret tripping, respectively, from 'CUF 101'. These populations were developed under glasshouse conditions using methods identical to those previously described (1,2,3). In Cycle 1, the 28 easiest-to-trip and 26 hardest-to-trip plants were selected from a population of 180 plants of CUF 101. Within selection types, plants were intercrossed by hand pollination without emasculation and the resulting seed was harvested and bulked. Cycle-2 populations were developed by evaluating 262 easyand 315 hard-to-trip Cycle-1 plants and selecting the 45 easiestand 45 hardest-to-trip plants, respectively. Individuals selected within each of the populations were intercrossed and seed was harvested as before to produce Cycle 2. Easyand hard-to-trip Cycle-2 populations differed significantly (P < 0.05) from CUF 101 in a glasshouse evaluation conducted during September 1991. UCCUF-ET(L)2 required 15% less force to induce tripping, and UCCUF-ET(H)2 required 27% more force to induce tripping than CUF 101 (2). These populations were evaluated under field conditions in both 1990 and 1991 at two locations on the University of California, Davis, campus. Populations exhibited significant (P < 0.05) response to selection in both tests. The average change from CUF 101 in force required to induce tripping between the easy-to-trip (—10%) and the hard-totrip (+26%) populations was nearly the same as we had previously determined when evaluating these CUF 101-derived populations in the glasshouse. Seed production, forage yield, and pest and disease reactions of these populations have not been determined. Individual plants selected in Cycle 2 were transplanted from the glasshouse to isolation cages for seed increase in 1991. Pollination was by honey bees (Apis mellifera L.). Five grams of Cycle-2 Syn1 seed of UCSAR-ET(L)2, UCSAR-ET(H)2, UCCUF-ET(L)2, and/or UCCUF-ET(H)2 are available upon written request and agreement to make appropriate recognition of this source a matter of open record when this germplasm contributes to either a publication or the development of a new cultivar, hybrid, or germplasm. Request seed from the corresponding author; include the UC identification number (given above), as well as the registered name and P1 number. Requests from outside the USA should be accompanied by appropriate customs control documents.