Dark-light treatments influence induction of tomato anther callus

Three tomato (Lycopersicon esculentum Mill.) cultivars were studied to de- termine the effect of nine dark-light regimes on anther callus initiation and growth. Prophase I (leptotene) stage anthers of 'L-680A', 'Licato', and 'Ailsa Craig' were plated on Doy's basal medium 1 and provided with 2 to 10 weeks of dark treatment. After each dark period, each plate was transferred to a 16-hour photoperiod for the duration of the 10-week experiment. At this time, the number of anthers producing calli and the diameter of the calli produced were recorded. Callus number and diameter in- creased as the dark period duration increased. Callus diameter peaked at 8 weeks of dark treatment for 'Ailsa Craig' and 'Licato', whereas 'L-680A' calli continued to grow over the entire 10-week dark treatment. Although the number and size of callus may continue to increase past 8 weeks of dark incubation, callus quality and appearance decreased noticeably during this period. For each additional week of dark period exposure, 7% more of the plated anthers produce callus, and callus diameter increases by 0.27 mm (12% of total growth). -