Registration of Six Alfalfa Germplasm Pools Seleted for Receptacle Diameter

Six alfalfa (Medicago saliva L.) germplasm pools (Reg. no. GP301 to GP-306) were released by the Department of Agronomy and Range Science at the University of California, Davis, and the California Agricultural Experiment Station in September 1987: UCRD-A(H)2, UCRD-A(L)2, UCRD-B(H)2, UCRD-B(L)2, UCRD-C(H)2, and UCRD-C(L)2. Their P1 numbers are given in Table 1. UCRD-A(L)2, UCRD-B(L)2, and UCRD-C(L)2 were selected for small receptacle diameter and UCRD-A(H)2, UCRD-B(H)2, and UCRD-C(H)2 were selected for large receptacle diameter. All six germplasm pools were developed by two cycles of phenotypic recurrent selection for receptacle diameter by intermating the best 45 of 450 plants in each cycle (1). The -A, -B, and -C germplasm pairs were selected from 'CUF 101', 'Team', and 'Vernal', respectively (Table 1). The first cycle of selection was conducted under greenhouse conditions at Davis, CA, in July of 1978 and the second cycle was conducted under equivalent conditions in July of 1979. Receptacle diameter was scored on a scale of 1 to 5, where 1 < 1.2 mm, 2 = 1.2 to 1.4 mm, 3 = 1.4 to 1.6 mm, 4 = 1.6 to 1.8 mm, and 5 > 1.8 mm (1). Syn-1 seed of each of the Cycle-2 pools was produced by unemasculated hand pollination in 1979 and evaluated under greenhouse conditions for receptacle diameter in 1980 and under field conditions at Five Points, CA, and Prosser, WA, in 1981 (2). Respective small and large receptacle diameter selections from each of the cultivars were significantly different from each other in both