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Dep. of Agronomy, Iowa State Univ., Ames, IA 50011. This journal paper of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa
* Corresponding author (hallauer{at}iastate.edu)
BSLE(M-S)C30 (Reg. no. GP-401, PI 636503) and BSLE(M-L)C30 (Reg. no. GP-402, PI 636502) are maize (Zea mays L.) populations developed after 30 cycles of divergent mass selection for ear length by the Iowa Agriculture and Home Economics Experiment Station. Both populations originated from Iowa Long Ear Synthetic (BSLE), which was developed by intermating 12 inbred lines with above-average ear length (Russell et al., 1971). The grid system of mass selection for shorter and longer ear length was used for each of the 30 cycles of selection (Gardner, 1961). After the initial cycle of selection, two isolation fields (a minimum of 200 m from other maize) were used, one for selection for shorter ears and the second for selection for longer ears. Within 100 plots of 40 plants per plot, three ears were selected, equal quantities of seed from the three selected ears were bulked, and the bulk used for the next cycle of selection. Effectiveness of mass selection for divergent ear length was monitored after 10 (Cortez-Mendoza and Hallauer, 1979), 15 (Salazar and Hallauer, 1986), and 27 (Lopez-Mendoza and Hallauer, 1998; Hallauer et al., 2004) cycles of selection.
BSLE(M-S)C30 is a strain of BSLE developed after 30 cycles of mass selection for reduced ear length. Average ear length decreased 0.37 cm cycle–1 of mass selection during 27 cycles of selection (Lopez-Mendoza and Hallauer, 1998). Average ear length of BSLE(M-S)C27 (10 cm) was 10 cm less than average ear length of BSLE (20 cm). Correlated changes for BSLE(M-S)C27 with mass selection for reduced ear length included 2.2 Mg ha–1 less yield, reductions in plant (43 cm) and ear (22 cm) height and days to flower (5.7 d) and increases in ear diameter (0.27 cm) and number of kernel rows (3.0) compared with BSLE. Root and stalk lodging were reduced with the correlated reductions in plant and ear height compared with BSLE.
BSLE(M-L)C30 is a strain of BSLE developed after 30 cycles of mass selection for increased ear length. Average ear length of BSLE(M-L)C27 increased 0.27 cm cycle–1 of mass selection (Lopez-Mendoza and Hallauer, 1998). Ear length of BSLE(M-S)C27 was 27.3 cm compared with 20 cm for BSLE. Selection for increased ear length did not increase grain yield. Twenty-seven cycles of mass selection for increased ear length caused a nonsignificant yield decrease of 0.27 Mg ha–1. Correlated changes in BSLE(M-L)C27 with mass selection for increased ear length were opposite to those for decreased ear length: plant (41 cm) and ear (27 cm) height and days to flower (5.7 d) increased, whereas ear diameter (0.54 cm) and number of kernel rows (1.6) decreased compared with BSLE (Lopez-Mendoza and Hallauer, 1998). Root and stalk lodging and prolificacy of BSLE(M-L)C30 also increased with mass selection for increased ear length.
BSLE(M-S)C30 and BSLE(M-L)C30 are significantly different from each other for ear length and other plant and ear traits, and both populations are significantly different from BSLE, the original population, for all traits except for grain yield of BSLE and BSLE(M-L)C27 (Lopez-Mendoza and Hallauer, 1998). Phenotypically, BSLE(M-S)C30 has more desirable plant and ear types than either BSLE and BSLE(M-L)C30, but yield of BSLE(M-S)C30 is about 50% less than BSLE and BSLE(L-S)C30. BSLE(M-S)C30 and BSLE(M-L)C30 are genetically unique populations for relative ear length, but both populations have limited value in maize breeding programs. Relative maturity of BSLE(M-S)C30 is AES700 and relative maturity of BSLE(M-L)C30 is AES800.
Breeder seed of BSLE(M-S)C30 and BSLE(M-L)C30 is maintained by the Iowa Agriculture and Home Economics Experiment Station. Seed (500 seeds per request) of BSLE(M-S)C30 and BSLE(M-L)C30 can be obtained from Mark Millard at the Plant Introduction Station, Ames, IA 500111.
NOTES
Project No. 3755, was supported by Hatch Act and State of Iowa funds. Registration by CSSA.
Accepted for publication March 31, 2005.
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