RECURRENT SELECTION FOR DIVERGENT LENGTH OF GRAIN-FILLING PERIOD IN THE COLUS MAIZE POPULATION (ZEA MAYS L.) (PHYSIOLOGICAL TRAIT, BLACK LAYER)
Abstract
The grain-filling period (GFP) is defined as the time to black-layer formation (BL) minus the time to anthesis. The Colus maize population was recurrently selected over four cycles for long and short GFP (LGF and SGF, respectively), attempting to keep time to anthesis fixed. The objectives were to evaluate the direct and indirect responses to selection. Cycles 0 to 4 selections were evaluated as selections per se for time to anthesis, BL, GFP (direct traits), and plant and ear height (indirect traits) in Lafayette in 1984. Cycles 0 to 3 were testcrossed to three inbred testers, which were evaluated for time to anthesis, BL, GFP (direct traits), grain yield, grain moisture, 100-kernel weight, percent lodging, ears per 100 plants, and ear and plant height (indirect traits) in 1983 and 1984. Testcrosses of cycles 0 and 3 were also evaluated for dry matter (DM) accumulation. The LGF and SGF selection responses were diverging for BL, GFP, grain moisture, 100-kernel weight, percent lodging, ears per 100 plants, and plant and ear height. The GFP of LGF selections increased 0.36 (+OR-) 0.22 days per cycle on a selections per se basis, and 0.56 (+OR-) 0.24 days per cycle on a testcross basis. The GFP of SGF selections decreased 3.02 (+OR-) 0.22 days per cycle on a selections per se basis, and 0.90 (+OR-) 0.24 days per cycle on a testcross basis. In LGF selections, the harvest grain moisture and 100-kernel weight were significantly increased. In SGF selections, the grain yield, harvest grain moisture, 100-kernel weight, and plant and ear height were significantly reduced, and the number of ears per 100 plants was significantly increased. The rate of DM accumulation of SGF-C3 was also reduced. These results indicate that SGF selection resulted in correlated changes in many traits characteristic of early maturing maize genotypes. LGF selection was less effective in changing traits both directly and indirectly. This asymmetry in the LGF and SGF selection responses may have resulted from an environmental restriction on the GFP length of the Colus population.
Degree
Ph.D.
Subject Area
Agronomy
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