MODIFYING SEEDLING PHOTOMORPHOGENESIS IN KLEINGRASS BY RECURRENT SELECTION

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 surfa ce, adversely impacting seedling establishment. A recently described c ontinuous low light system identifies species with excessive CN elevat ion. Our objectives were to use this system to determine if CN positio ning could be modified by selection. Three cycles of recurrent selecti on were performed for elevated crown (EC) and low crown (LC) CN placem ent in kleingrass (Panicum coloratum L.) in a continuous low light (1. 5 umol m(-1) s(-1)) environment from 1991 to 1994 in central Texas. Se lection in both directions was successful. In the EC populations, a re latively 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 growt h were minor. A small increase was observed with selection for higher CN placement. The Cycle 3 EC and LC germplasm should be useful for fur ther characterizing seedling photo-morphological responses. In additio n, the Cycle 3 LC germplasm should be less prone to excessive SCI elon gation in held environments and may have superior establishment charac teristics.