Masters Theses

Date of Award

6-1983

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

B. V. Conger

Committee Members

James MacDonald Stewart, James Caponetti

Abstract

The primary objectives of this study were to develop a suitable culture system and obtain plant regeneration from callus for Kentucky bluegrass (Poa pratensis L.) cultivars. Secondary objectives included (a) comparing the regenerability of cultivars differing in percent apomictic reproduction; (b) cytological investigation of chromosome numbers of regenerated plants; (c) testing incubation temperature effects on plant regeneration; and (d) determining the mode of plant regeneration from callus cultures. Mature embryos of seven Kentucky bluegrass cultivars were plated on a solid, modified Schenk and Hildebrandt medium in a series of three experiments. The first experiment, using the cultivar 'South Dakota,' tested the four synthetic auxins 2,4-D(2,4- dichlorophenoxyacetic acid), 2,4,5-T(2,4,5-trichlorophenoxyacetic acid, dicamba (3,6-dichloro-o-anisic acid), picloram (4-amino-3,5,6- trichloropicolinic acid) at six different concentrations for callus induction and growth. Results indicated that dicamba at 20 μM and picloram at 60 μM produced the best callus growth and most shoot and root suppression. Using these auxin concentrations, a second experiment was conducted using seven cultivars with varying percentages of apomictic reproduction. Results indicated variation among cultivars and auxins in call using and plant regeneration with plantlet formation percentages being low (0%-3.1%). Somatic chromosome counts of regenerated plants and cultivar reference plants showed some varia-tion. No relationship was observed between percent apomictic reproduction and plant regenerability in the cultivars. A third experiment tested the effects of culture temperature (25°C vs. 15°C) and cold shock (4°C for 7 days) on plant regenera-tion from calli of the cultivars 'A25 x Blacksburg' and 'Ram I' using 20 μM dicamba. Culture at 15°°C improved plant regeneration over 25°C for both cultivars. Cold treatment at the 15°C culture temperature was not superior to no cold treatment for A25 x Blacksburg. Ram I demonstrated the highest percent plant regenera-tion at 15°C with a cold treatment (18.0%). A histological examination of calli in the latter two experiments showed the mode of plant regeneration to be organogenesis.

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