Kentucky Bluegrass (Poa pratensis L.) Germplasm for Seed Production without Field Burning.

With the loss of field burning of post-harvest residue in grass seed production in Washington, identifying Kentucky bluegrass germplasm that has sustainable seed yield without field burning while still maintaining acceptable turfgrass quality would be highly desirable for the turfgrass seed industry of Washington.  This long-term study initially evaluated 228 USDA/ARS Plant Introduction (PI) accessions for turf and agronomic parameters.  Eight PIs plus ‘Kenblue’, identified in follow-up research, expressed high seed yield without burning of post-harvest residue and good turfgrass quality.  Next, in a space-plant nursery, several agronomic yield parameters were evaluated over a 2-year period and individual plants were reselected within each accession, or check, with the highest seed weight, highest seeds/head, highest heads/area, and highest seed yield.  Turfgrass plots (replicated 2.25 sq. m plots) were established in 2006 and seed production plots (irrigated and non-irrigated, replicated 3.8 sq. m plots) were established in 2007 at Pullman, WA and harvested 2008-2011.  Seed increase plots (non-replicated 0.06 ha plots) of the three best performing selections were established in 2011 and harvested 2012-2014.  PI 368241, selection heads/area, in small plots showed the most promise of being able to provide long-term turfgrass seed yield (1003 kg/ha) without field burning and had fair turfgrass quality (NTEP quality = 5.1).  Kenblue, selection seeds/head, had good seed yield (893 kg/ha) and fair turfgrass quality (5.4); Kenblue check yielded 447 kg/ha.  PI 371775, selection seeds/head, had good turfgrass quality (6.1) while maintaining good seed yield (898 kg/ha) with irrigation.  In the seed increase plots at Pullman, the Kenblue selection seeds/head continued to show excellent dryland seed yield (1128 kg/ha) over three harvests.  PI371775 continued to produce fairly well (930 kg/ha) with irrigation.  PI368241 has shown a decline in seed yield over time.  A germplasm release of Kenblue, selection seeds/head, is planned for late 2015.