Date of Award

2004

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant Science

Advisor

Gregory A. Porter

Second Committee Member

Mary Susan Erich

Third Committee Member

Alan R. Langille

Abstract

The overall goal of this research was to develop new rapid techniques for screening potato genotypes for drought tolerance. A series of approaches namely singlenode cutting assay (SNCA), root tip cutting assay (RTCA), microtuberization assay (MA), greenhouse experiment GE), and leaf disc assay (LDA) were employed to answer the questions: (1) can root and shoot growth reduction be used to screen potato for drought-stress tolerance, (2) can tuber production be used to screen potato for droughtstress tolerance, (3) can excised root elongation and leaf disc growth reduction be used to screen potato for drought-stress tolerance? Potato genotypes (Chagllina-INZq E86.011, Reiche, C89.3 1 5, Tacna, Unica, Andover, Superior, Shepody, Kennebec, Katahdin, and Russet Burbank) were exposed to Polyethylene glycol (PEG) solutions (8% PEG8000, except for LDA using 10% PEG8000) and their growth reduction compared to the control (0% PEG8000) were determined. It was expected that PEG treatments could mimic the effects of water stress and cause significant growth reduction in which genotypes known to be drought tolerant demonstrated less growth reduction than genotypes known to be drought sensitive. As expected, the results showed that PEG treatments mimicked the effect of water stress in all approaches employed during the study. Kennebec known to be drought tolerant consistently showed less growth reduction than most genotypes tested, while Superior known to be drought sensitive demonstrated the opposite. It was true for root length density reduction WDR) and root dry weight reduction (RDWR) in SNCq and leaf growth reduction (LGR) in LDA, which meant that those dependent variables could be use to select potato genotypes for water stress tolerance. Root growth reduction (RGR) and RDWR in RTCA might be used to select potato genotypes for water stress tolerance in conjunction with LGR of LDA. The GE approach needs lots of improvement to be used for water-stress screening of potato genotypes. To minimize the effect of environmental factors, it was recommended that the screening process be done in the growth chamber regardless of the choice of the approaches.

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