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Seed Production by Ryegrass-Fescue Hybrid Derivatives in Muslin-Covered Cages¹

Clones of ryegrass-fescue (Lolium-Festtica) hybrid-derivative origin were used to produce syn-1 generation seed of eight 4-clone synthetics under muslin-covered isolation cages. Cages, about 1.5 m wide x 5.2 m long x 15 m high, were constructed over plots containing 16 space-planted ramets of each of the four clones of each synthetic. The cages were covered with muslin a few days before anthesis.

Very large differences, which could be attributed to cages (or synthetics) and to clones within synthetics, were observed in 1966 and 1968. Some clones produced very little seed. Although differences between years were large, the correlation between seed production in 1966 and 1968 was highly significant (r = 0.478).

The effects of several cage treatments on seed production were evaluated on plots established to one 4-clone synthetic. The cage treatments were: no fan, fans, and fans plus dehumidifier in 1970; open cage, no fan, and fans in 1971; and open cage, no fan, one fan, and two fans/cage in 1972.

The presence of fans in the cages significantly increased seed yields in 1970, but not in 1971 or 1972. Using a dehumidifier did not increase seed production over that with fans alone. Seed production outside cages was always significantly greater than production in cages, regardless of the cage treatment. Although smaller than variations due to cage treatments and clones, significant clone by cage treatment interactions were observed each year. This interaction suggests that seed produced under different conditions could be genetically different. Seed of experimental ryegrass-fescue hybrid-derivative populations can be produced in isolation under muslin-covered cages. However, more research is needed to determine the effect of cage environments on the genetic composition of the seed produced and on techniques to reduce interactions.

Key Words: Grass breeding • Isolation • Pollination control • Seed yields • Ryegrass • Meadow fescue • Tall fescue • Lolium perenne L. • Festuca pratensis Huds. • Festuca arundinacea Schreb.

² Research geneticist and research agronomist, respectively, U.S. Regional Pasture Research Lab., ARS, USDA, University Park, PA 16802.

Received for publication May 10, 1974.