Carrot bait

From BugwoodWiki

Contents 1 Purpose 2 Instructions 3 Notes 4 References 5 Contributed by

Purpose

For isolation of Thielaviopsis basicola¹ from soil.

Instructions

1. If using roots, wash them, but do not surface-sterilize.
2. Scrape two carrots with knife to remove surface tissue. Cut off tops and bottoms.
3. Place filter paper in bottom of two pyrex Petri dishes. Moisten with sterile dH2O, using Pasteur pipette.
4. Surface-disinfect carrots in 10% bleach solution for 2-5 minutes.
5. Cut carrots into disks about 5 mm thick with sterile knife. Place about 6 disks on filter paper in each dish with one disk in center (control).
6. Place roots or soil on all disks except control.
7. Moisten roots/soil with sterile dH2O and place a carrot disk on top of each disk. Also moisten tops of disks with sterile dH2O.
8. Leave roots for 2-7 days at room temperature. If using soil, leave at room temperature, but in 2-4 days wash soil off with sterile dH2O and place disks on fresh moist filter paper; continue incubation.

• Steps 3-8 should be performed under a hood.

Notes

• Malby, et al. cautions against using carrots contaminated with Chalaropsis thielavioides, which is very similar to T. basicola.

• ¹To detect crown gall bacteria, see Plant Dis. Reporter 42: 1279-1281; to detect Ceratocystis fimbriata, see Phytopathology 58: 123-124.

References

• Lloyd, A.B. and J.L. Lockwood. 1962. Precautions in isolating Thielaviopsis basicola with carrot discs. Phytopathology 52: 1314-1315.

• Maloy, O.C. and M. Alexander. 1958. The "most probably number" method for estimating populations of plant pathogenic organisms in the soil. Phytopathology 48: 126-128.

• Yarwood, C.E. 1946. Mycologia 38: 346-348.

Contributed by

From the Virginia Tech Mediabook; Orignially created by Robert Wick; contributed by Mary Ann Hansen