Convergent-Divergent Selection for Seed Production and Forage Traits in Orchardgrass: I. Direct Selection Responses
- M. D. Casler ,
- I. T. Carlson,
- C. C. Berg,
- D. A. Sleper and
- R. E. Barker
- D ep. of Agronomy, Univ. of Wisconsin-Madison, Madison, WI 53706-1597
f ormerly Dep. of Agronomy, Iowa State University, Ames, IA 50011
2 72 Bradley Ave., State College, PA 16801
D ep. of Agronomy, Univ. of Missouri, Columbia, MO 65211
U SDA-ARS National Forage Seed Production Research Center, 3450 S.W. Campus Way, Corvalis, OR 97331-7102
Simultaneous improvement of forage traits and seed yield in orchardgrass (Dactylis glomerata L.) has been problematic because of geographic separation of forage and seed production locations. Most attempts to simultaneously improve both forage and seed traits have relied on a single location. The objective of this study was to conduct and evaluate two cycles of convergent-divergent (C/D) and local selection for panicle seed weight (PSW) and forage traits. Selection was conducted at four locations (Ames, IA; Mount Vernon, MO; Rock Springs, PA; and Arlington, WI) in four base populations (I79DT, MO2, PLS4, and WO11). Phenotypic selection on a spaced-plant basis was applied at a 0.25 selection intensity for forage traits, followed by a 0.25 selection intensity for PSW. All populations were evaluated as spaced plants at the Iowa and Pennsylvania locations in 1990 and 1991. Both selection methods were equally effective at increasing PSW, with responses averaging 1.0 to 18.2% cycle−1. Realized heritabilities for PSW were highly variable among the four populations (mean of 0.03–0.23) and were lower for Cycle 2 than for Cycle 1 (mean of 0.02 vs. 0.16). For C/D selection, IA, MO, PA, and WI selection locations increased PSW by 25, 39, 94, and 33 mg panicle−1 respectively. Three of the four populations had significant genetic changes of 2 to 4 d later heading, despite no direct selection pressure for heading dale. There were very few significant and biologically meaningful genotype × location interactions for any trait. Therefore, neither selection method resulted in plants with differential adaptation when evaluated as spaced plants.
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