|Hopkins, A - NOBLE FOUNDATION|
|Moore, K - IOWA STATE UNIVERSITY|
|Johnson, K - PURDUE UNIVERSITY|
|Carlson, I - IOWA STATE UNIVERSITY|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 8, 2003
Publication Date: November 1, 2003
Citation: Vogel, K.P., Hopkins, A.A., Moore, K.J., Johnson, K.D., Carlson, I.T. 2003. Winter survival in switchgrass populations bred for high ivdmd. Crop Science.42:1857-1862. Interpretive Summary: Recurrent breeding cycles for improved forage digestibility as measured by in vitro dry matter digestibility (IVDMD) in switchgrass has resulted in populations with improved digestibility which has resulted in improved animal performance. An advanced breeding population, EY x FF High IVDMD C3, had a high percentage of plants winter kill. Two studies were conducted to determine the association between increased digestibility and winter survival. One study involved space-transplanted families and the other trial used solid seeded plots. The results demonstrate that in the space-transplanted study, some families within the high IVDMD cycle 3 population had increased winter kill but other families had adequate winter survival and improved IVDMD. The differences in winter survival were not detectable in the solid seeded sward trials. The results indicate that multi-year evaluation trials should be used to breed for improved digestibility in switchgrass in order to select for winter survival and increased IVDMD.
Technical Abstract: In vitro dry matter digestibility (IVDMD) was improved by three cycles (C) of recurrent selection in a switchgrass (Panicum virgatum L.) population but significant winter kill occurred in the cycle 4 (C4) mass selection nursery. Stand density losses in strains differing in IVDMD also were noted in pastures intensively grazed for three years. Two studies were conducted to evaluate the effect of genetic changes in IVDMD of switchgras on plant survival. High IVDMD C3 half-sib family seedlings were planted into a replicated evaluation nursery in 1991 at Mead, NE. This nursery was harvested in 1993 and 1995 for biomass yield after plants had headed, forage was analyzed for IVDMD, and plant survival was determined. There were significant differences among the families for biomass yield, IVDMD, and plant survival. Among the half-sib families, the correlations of 1993 and 1995 IVDMD with 1995 survival were not significant nor were the correlations between 1993 and 1995 yields, and 1995 stands. In the C3 hig IVDMD populations, some families had decreased winter survival but other families had high IVDMD and good survival. Randomly selected plants from pasture trials (PC or pasture clones) of 'Trailblazer' and 'Pathfinder' were polycrossed and the resulting bulk populations were evaluated with parent populations in replicated sward trials at three locations along with the High IVDMD C3 population & its derived winter survival (WS) population produced by harvesting bulk seed from surviving plants in the C4 selection nursery. Differences among populations for stand were not detected in the sward trials, likely because survival & IVDMD have low correlations within populations. It should be feasible to continue to breed for high IVDMD in switchgrass but survival will need to be an additional selection criterion.