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Modifying Seedling Photomorphogenesis in Kleingrass by Recurrent Selection

USDA-ARS, Grassland, Soil and Water Res. Lab., 808 E. Blackland Rd., Temple, TX 76502-9601
Appalachian Soil & Water Conservation Res. Lab. USDA-ARS, P.O. Box 867, Beckley, WV 25802

^* Corresponding author (a03lctemple{at}attmail.com).

In emerging Panicoid grass seedlings, elongation of the subcoleoptile internode (SCI) stops shortly after the coleoptile tip receives a red light stimulus. This results in final placement of the crown node (CN) near the soil surface. Because adventitious roots originate from the CN, excessive elongation of the SCI places the CN above the soil surface, adversely impacting seedling establishment. A recently described continuous low light system identifies species with excessive CN elevation. Our objectives were to use this system to determine if CN positioning could be modified by selection. Three cycles of recurrent selection were performed for elevated crown (EC) and low crown (LC) CN placement in kleingrass (Panicum coloratum L.) in a continuous low light (1.5 umol m^–2 s^–2) environment from 1991 to 1994 in central Texas. Selection in both directions was successful. In the EC populations, a relatively linear increase in CN elevation was observed across the three cycles, while in the LC populations, most of the progress was made in the first cycle. Effects of selection for CN placement on shoot growth were minor. A small increase was observed with selection for higher CN placement. The Cycle 3 EC and LC germplasm should be useful for further characterizing seedling photo-morphological responses. In addition, the Cycle 3 LC germplasm should be less prone to excessive SCI elongation in field environments and may have superior establishment characteristics.

Received for publication October 12, 1994.