Sprouting, plant establishment, and yield improvement of potato (Solanum tuberosum L.) minituber cultivars by foliar application of benzylaminopurine and abscisic acid

Backgrounds and Potato is the fourth important crop worldwide. Since potato is mainly propagated vegetatively via tubers, increasing production of high quality and virus free seed potato is of great importance. Phyto-hormones regulate a wide range of processes and tuberization in potato. Due to small size and weakness of minitubers and some difficulties in plantlets establishment in the field, more studies are needed to improve plant establishment and productivity of minitubers under such conditions. Therefore, this study was carried out in order to evaluate the possibility of improving sprouting and plantlet establishment of potato minituber cultivars (Agria and Fontane) using plant growth regulators (6-benzylaminopurine- BAP, and abscisic acid- ABA).
A two-step experiment was carried out at the Ferdowsi University of Mashhad, during 2014-15. In the first experiment, foliar treatment of mother plants at stolonization or tuberization stages using plant growth regulators (BAP, ABA, and BAP, 50 µM) under controlled conditions was performed. In the second experiment, progeny minitubers were compared in terms of sprouting, plantlets establishment, and yield under field conditions. Factorial arrangement based on completely randomized design and complete block design were used for the first and second experiments, respectively. Number of sprouts per minituber, length of sprouts, day to emergence, emergence percentage, number of stems per plant, morphological traits, yield, and yield component were evaluated.
Day to emergence tended to decrease with an increase in sprout length. In both cultivars, BAP application at tuberization stage increased sprout length compared with the untreated control plants. The number of established plantlets and percentage of emergence were enhanced by treating plants using BAP or ABA compared with control plants, but the effects were different on the cultivars. The greatest emergence percentage observed in ABA-treated plants at stolonization stage, which was 39% more than the control. In addition, Fontane showed greater emergence percentage (15 %) than Agria. BAP application at tuberization stage advanced the number of sprouts in Agria, whereas, the most number of sprouts in Fontane recorded when BAP applied at tuberization stage. Good linear relationship was observed between sprout length and day to emergence (R2=0.88) and between the number of sprouts on minitubers and the number of tubers in the next generation (R2=0.53). Regardless to the cultivar, application of BAP at tuberization stage increased the number of tubers per plant.
The results indicating that application of BAP resulted in increasing the number of sprouts and shortened the days to emergence, whereas, ABA improved emergence parentage and plantlet establishment of the both cultivars. It seems that both BAP and ABA could be effectively used for improving sink strength for better supporting the sprouts growth under field conditions. In addition, it seems tha application of PGRs increase the number of sprouts per tuber which resulte in producing greater number of stems, hence, enhance the number of tubers per plant, however, the effects are different between cultivars.