Responses to Divergent Selection for Fiber Concentration at Two Disease Potentials in Smooth Bromegrass
- L.X. Hana,
- M.D. Casler *b and
- C.R. Grauc
Neutral detergent fiber (NDF) concentration is related to intake potential of forages but might also be related to plant reaction to pathogens. Three smooth bromegrass (Bromus inermis Leyss.) populations from these cycles of uniparental mass selection for low NDF, one cycle of biparental mass selection for high NDF, and the base population were evaluated at high and low disease potentials at three locations for 2 yr and three harvests each year. High disease severity, measured as proportion of foliage diseased, was associated with high NDF and high lignin concentration (on a dry-matter basis and a cell-wall basis). Nevertheless, disease potentials did not affect the relative performance of selection cycles on any traits measured. On average, NDF was reduced 3.5 g kg−1 DM per cycle (P < 0.001) by selection for low NDF, and increased 11.1 g kg−1 DM in one cycle (P < 0.001) by selection for high NDF. For the spring harvest, the response in NDF could partially be attributed to a change in heading index. A positive correlated response in acid detergent lignin was found in the spring (P < 0.001) while a negative correlated response in cell wall lignin was detected in the summer and fall (P < 0.001). Selection for NDF modified the composition of NDF, as cell wall hemicellulose changed in the opposite direction of NDF. Lower dry matter yield per plant appeared to be associated with lower NDF and higher inbreeding. Selection for low NDF, accompanied by slight selection pressure on disease resistance, resulted in a reduction of NDF without an increase in disease susceptibility.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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