Walkof, C.
The use of sodium 2, 3 - dichloroisobutyrate as a selective gametocide has resulted in temporary male sterility in the Meteor and Manitoba tomato varieties at Morden, Manitoba. In view of the popularity of F1 hybrid tomatoes this type of sterility may have value in producing seed at reasonable cost. In greenhouse tests optimum concentration for gametocide spray appeared to approximate 0.3 per cent. Best results were obtained by wetting the plants thoroughly. Slight floral distortion and marginal leaf discoloration were noted shortly after treatment. Repeated spray applications at 10 to 14 day intervals are required to maintain a sterile male gamete in actively growing plants. Lower seed set per fruit in treated plants than in those that were emasculated and not treated can be expected. This difference is offset by a potentially greater number of fruits containing hybrid seed from treated plants than from those manually emasculated with the use of an equal amount of labor. Use of the gametocide in hybrid tomato seed production in the field would require alternating rows of treated plants used as females with those of the male or pollen parent. Insects would be expected to transfer pollen to treated plants. Increasing the concentration of gametocide greater than the optimum for male sterility tended to destroy the function of the female gamete. Plants treated with excessive amount of gametocide (up to 1.5 per cent) in one application failed to recover normal growth.