Date of Award:

1-1-1988

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Advisor/Chair:

William F. Campbell

Abstract

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 Hu rashige and Skoog (t1S) medium containing 0.5 mg L-1 6- furfurylaminopurine (kinet in) 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 -l 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 sal fed 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 (SC 1 and sc 2 ) showed no variation in glutamine oxaloacetate transaminase (GOT) (E.C . 2. 6. 2.1. ), leucine aminopeptidase (LAP) (E.C. 3.4.11.1), 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. Cal li 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.

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