Date of Award

1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant, Environmental Management and Soil Sciences

First Advisor

Don R. LaBonte

Abstract

Arbitrarily-primed PCR-based assays established the presence of sweetpotato intra-clonal genetic variability. These DNA polymorphism assays provided benchmark information regarding cultivar genetic uniformity in sweetpotato foundation seed programs. Arbitrarily-primed markers were also used to compare the genetic uniformity among sweetpotato clones derived conventionally, i.e., through adventitious sprouts, and nodally-based propagation systems. Initially, 38 primers generated 110 scorable DNA fragments using two virus-indexed plants from each clone source. Twenty-one bands (18.6%) were scored as putative polymorphic markers based on the presence or absence of amplified products. A subset of 14 marker loci generated by four selected primers was used to further assay 10 sample plants per clone group. Polymorphism ranged from 7.1% to 35.7% in five of eight clone groups. Field studies show variation in nearly all yield grades measured. In three tests during the 1991 and 1992 seasons, yield differences ranged from 27% to 46% within the economically important U.S. No. 1 root grade. The results suggest the usefulness of arbitrarily-primed markers in detecting intra-clonal genomic variability in the crop. To determine the role of propagation method in sweetpotato genotypic uniformity, a single sprout each of 'Jewel,' 'Sumor,' and L87-95 served as source of clonal plants simultaneously propagated through conventional adventitious procedures and an in vitro-based nodal technique. Fifteen arbitrary primers generated 64 scorable amplified fragments, 29 of which were putatively polymorphic across n = 60 samples (10 each of nodal and adventitiously derived plants/genotype). Within adventitiously derived materials, putative polymorphisms ranged from 4.7% to 31.3% depending upon genotypic class. In contrast, putative polymorphisms ranged from 0.0% to 3.1% among nodally-derived samples. The marker loci differentiated the genotypes and putative marker phenotype variants as revealed through multidimensional scaling analysis. An 'analysis of molecular variance' shows that genotypic effects accounted for 88.7% of the total marker variability, while propagation effects (within genotypic groups) accounted for 11.3%. The results suggest variability associated with propagation, wherein clonal plants derived from pre-existing meristematic regions are more genetically uniform than plants propagated from adventitious origins.

Pages

74

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