Concentration and ratio of IAA and gibberellic acid as factors to affect the effectiveness of potato micropropagation

Abstract

Nutrient media differed in the concentration and ratio of IAA and gibberellic acid (GA3) were compared concerning their effect on the rate of cloning of potato microplants in vitro. Microplants of the Red Scarlet variety served as the object. Hormone-free Murashige-Skoog medium (MS) was used as a control. The total cultivation period was 49 days. The rate of shoot growth and the internode formation was higher by 1.5 times on the media with phytohormones already in the first week of cultivation. From the 35th day until the end of the observations, the number of internodes on I1G2 media (1 mg/l IAA and 2 mg/l GA3) and I15G3 (1.5 mg/l IAA, 3 mg/l GA3) exceeded the values obtained in the control by 20%. In terms of weight and length, the plants on these media were 20–30% higher and heavier than the control ones. With a decrease in the concentration of hormones to 0.5 and 1 mg/l, respectively, such an increase was not observed. The ratio of IAA to GA3 1:2, regardless of the level of hormones, reduced the rate of rhizogenesis by half (14 days instead of 7) and decreased the root growth rate  by a third (21 days instead of 14) compared with the control. At the same time, the frequency of callus formation on the wound surface of the cutting on these media increased by 4-8 times, and the rate of callus formation increased by 1.5-2 times, in comparison with the control, in parallel with an increase in the absolute values of the phytohormones concentration. Media I05G2 (0.5 mg/l IAA, 2 mg/l GA3) and G3 (3 mg/l GA3) had no stimulating effect on the growth and development of microplants. Since in the process of mass cloning of potato in vitro, the problem of callusogenesis and delayed rhizogenesis can be neglected, and also from the considerations of minimizing the consumption of reagents, I1G2 is the most effective among the studied media.