J. AMER. SOC. HORT. SCI. 121(4):599-603. 1996.

Gamma Irradiation-induced Variation in Carrots (Daucus carota L.)

Bassam Al-Safadi¹ and Philipp W. Simon²
Vegetable Crops Research Unit, U.S. Department of Agriculture-Agricultural Research Service, Department of Horticulture, University of Wisconsin, Madison, WI 53706

Additional index words. mutagenesis, somaclonal variation

Abstract. Carrot tissue cultures, germinating seed, and dry seed were exposed to gamma radiation. Irradiation accelerated germination of carrot seed in the M₁ generation at low doses (0.5 and 1 krad), whereas higher doses delayed germination. A high negative correlation was observed between dose and survival of plants after seed irradiation. Plant size and root weight were 20 % to 35% greater than control plants after seeds, but not tissue cultures, were exposed to low doses of gamma irradiation. Higher doses reduced M₁ plant size by >50% in germinating seed and tissue culture treatments but less for the dry seed treatment. Seed production decreased while phenotypic variation of M₁ plants increased with increasing gamma ray dosage. Root weight and total dissolved solids were highly variable in M₂ families. Less variation was observed in total carotene content and none was seen in sugar type (reducing vs. non-reducing sugars). Induced variation in root color and root shape was also observed. Irradiation of germinating seed and tissue cultures yielded more M₂ variation than irradiation of dry seed. Putative point mutations were not observed. Unirradiated carrot tissue cultures did not yield significant M₂ somaclonal variation. Average root weight of M₂ plants increased with increasing gamma ray dosage especially for the dry seed treatment.

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Received for publication 28 Aug. 1995. Accepted for publication 7 Mar. 1996. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

¹Graduate Research Assistant. Permanent address: Syrian Atomic Energy Commission, P.O. Box 6091, Damascus, Syria.

²Research Geneticist and Professor.

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