The effect of the time and mode of application of gibberellic acid on the growth and yield of potato plants derived from true potato seed

The effect of the time and mode of treatment (single or repeated applications) of gibberellic acid (GA(3)) on the growth and tuberisation of plants grown from true seed (TPS) of potato Chacasina F-1 was studied. Plant height, fresh and dry weight of stems and leaf dry weight increased in response to single or repeated GA(3) applications. Leaf colour was not affected by single applications of GA(3), whereas repeated applications caused a reduction in colour intensity. The numbers of secondary shoots and leaves per plant as well as total leaf area were largely unaffected by GA(3), although repeated applications from early in the growth cycle increased these parameters under conditions of decreasing photoperiod. When applied as a single dose during spring, GA(3) caused an increase in the number of tubers per plant, with a concomitant decrease in tuber dry matter content, irrespective of application date. In autumn the number of tubers per plant increased following single applications of GA(3) up to 50 days after transplantation, whereas tuber dry matter decreased. By contrast, repeated applications of GA(3) in both seasons increased tuber number only when initiated early in the growth cycle. The mean weight of tubers per plant was variably affected by GA(3) application, depending on the season, time and mode of application. It is suggested that the foliar application of GA(3) to plants from TPS at an early stage of vegetative development may be of value for seed tuber or micro-tuber production, primarily by increasing the number of tubers produced per plant. (c) 2006 Society of Chemical Industry.