Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Plants, Soils, and Climate

Department name when degree awarded

Plant Science

Committee Chair(s)

William F. Campbell


William F. Campbell


Melvin D. Rumbaugh


John R. Simmons


John O. Evans


Somaclonal variation, to provide germplasm for crop improvement, must be screened, selected and characterized. Immature wheat, Triticum aestivum L., (PCYT-10) embryos (10-12 days old) were cultured on Hurashige and Skoog (MS) medium containing 0.5 mg L-1 6-furfurylaminopurine (kinetin) and 2, 3, or 4 mg L-1 of 1-methoxy-3,6-dichlorobenzoic acid (2,4-D). Dicamba, at 2 and 3 mg L-1 and 0.2 mg L-1 2,4-D, produced 12.7%, 30.3%, and 28.2% of the somaclones, respectively. No plantlets were produced from other treatments. Variants were characterized by cytology, biochemistry and morphology. Somaclones showed significant differences in length and width of flag leaf, plant height, number of tillers, spike length, awn length, and number of seeds per main head when compared to parental controls for two salfed recurrent generations. Number of spikelets per main head in the second generation showed no significant difference from controls. Stability and segregation of somaclones for measured traits indicated that genetic changes had occurred which could enhance wheat germplasm.

Leaf isozymes of somaclones (SC1 and SC2) showed no variation in glutamine oxaloacetate transaminase (GOT) (E.C., leucine aminopeptidase (LAP) (E.C., or esterase (EST) (E.C. 3.4.99) bands in 28% of the somaclones, 28% with light, and 44% missing a fast movind band. Approximately 30% of the normal group set no seeds. Mutants with the missing band were stable through the fourth-selfed generation, whereas, variants with the light EP band were still segregating. Plants with the missing EP band were morphologically normal compared to the parents except rachis internodes were longer than those of the parents.

There was no correlation between the missing EP band and a missing chromosome in some mutants. The mutant may have been due to a point mutation, deletion, or activation of a repressor gene. Variants exhibited a wide range of protein density and missing or extra bands.

Relative amounts of DNA per telophase nucleus were affected by inorganic salts and sucrose levels. Ploidy level increased with time within single-strength MS, but not within double MS medium. Calli grown on the modified double MS medium exhibited a higher number of shoots than those grown on modified MS.

Individual variants with desirable characteristics with high seed production, high protein levels, supernumerary spikelets, and larger flag leaves could be incorporated into a wheat improvement program.