Masters Theses

Date of Award

12-1988

Degree Type

Thesis

Degree Name

Master of Science

Major

Entomology and Plant Pathology

Major Professor

Mark T. Windham

Committee Members

J. Graveel, L.F. Johnson, C.J. Southards

Abstract

Pythium nunn (N3) a mycoparasite of other Pythium spp. , was added to five Tennessee soils (Bruno, Bowdre, Fullerton, Morganfield, and Robinsonville) to study its ability to colonize these soils. Mycelial mats were mixed into the soils and N3's inoculum density was determined weekly during an eight week incubation period. Numbers of colony forming units (cfu) fluctuated from nondetectable levels to 1040 cfu's/g of soil in the second to fourth week of incubation and decreased to approximately 80 cfu's or lower in the fourth to eighth week. In a separate experiment, N3 s ability to colonize Morganfield and Robinsonville soils was compared with it's ability to colonize Nunn sandy loam soil (a soil from Colorado from which it was originally isolated). Colony forming units of N3 were higher in the Tennessee soils than in the soil from Colorado after five weeks of incubation.

The effects of eight oils on growth and/or reproduction of Pythium nunn (N1) and N3 were determined. Wheat germ oil with 20 or 3 g/1 glucose or sucrose, consistently stimulated growth of N1 when compared to the other oils with sugar or controls. Codliver, wheat germ, sesame, and sunflower oils stimulated growth of N3. Several oils had varying effects on growth of both N1 and N3 when different sugars were used. Few or no sporangia of N3 formed in the oil and sugar combinations. These two Pythium spp. apparently have different chemical requirements for growth and reproduction.

Isolates of Trichoderma koningii, T. harzianum, T. viride and T. pseudokoningii were tested for their abilities to inhibit growth and/or stimulate reproduction of N3 and N1. Culture filtrates of the isolates were sterilized by cold filtration or autoclaving, were seeded with agar plugs of N1 or N3. All filtrates tested inhibited growth of N1 and N3. Two isolates of T. viride inhibited growth and oospore formation of N1 to a greater extent than did the other Trichoderma species. There was no difference in inhibition of growth and oospore formation with autoclaved or cold filtrates. Stimulation of reproductive structures in N1 and N3 by filtrates of Trichoderma species was not observed. Inhibition of growth of N3 in filtrates of Trichoderma reduces the possibility of integrating P. nunn with Trichoderma as an effective biocontrol management system.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS