ANTIMITOTIC AGENTS - EFFECTS ON DOUBLE HAPLOID PRODUCTION IN WHEAT

Chromosome doubling of microspore-derived plantlets and calli is a critical step in haploid breeding programs. For anther culture experiments, colchicine, (S)-N-(5,6,7,9-tetrahydro-1,2,3,10-tetramethoxy-9-oxobenzo[a]heptalen-7-yl)acetamide, is the most commonly used compound in doubling the chromosomes of seedlings derived from such experiments. Colchicine, however, is carcinogenic and expensive. We evaluated three antimitotic agents (colchicine; trifluralin, 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine; and oryzalin, 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide) at two treatment durations (48 and 72 h) and two concentrations [colchicine at 0.0125% (313-mu-M) and 0.025% (626-mu-M), and both trifluralin and oryzalin at 5 and 10-mu-M each for their effects on the production of double haploids from anther-derived calli of two wheat [Triticum aestivum (L.) em. Thell.] cultivars, Pavon and Kitt. Calli from Pavon were more responsive to the three agents than those from Kitt. Colchicine was the most effective in double the chromosome number. For Pavon, 89% of the plantlets from calli treated with colchicine were double haploids (2n = 6x = 42). However, treating calli for 72 h with colchicine at either concentration had a deleterious effect. No significant differences were observed between concentrations of any of the antimitotic agents. All the plantlets produced from the control treatment (without antimitotic agents) were polyhaploids (2n = 3x = 21). These results indicated that colchicine is still the most effective compound for chromosome doubling, and colchicine treatment of anther-derived calli is an effective method of obtaining a high frequency of double haploid plantlets through anther culture systems.