POTENTIAL APPLICATION OF JASMONIC ACID IN IN VITRO ROOTING OF LOW VIGOROUS PEAR AND CHERRY ROOTSTOCKS

We studied the capacity of jasmonic acid (JA) to improve the in vitro rooting phase in micropropagated shoots of very popular low vigorous pear and cherry rootstocks – Pyrodwarf and Gisela 6, respectively. The experiment was performed during the rooting phase and it included 7 medium types containing Murashige and Skoog (1962) macro- and micro-salts reduced to half, organic complex unchanged and supplemented with JA at four concentrations – 0.2, 0.5, 1 and 2 mg/L. The trial also involved two independent, standard rooting media supplemented with 1 mg/L of indole-3-butyric acid (IBA) and 1 mg/L of α-napthyl acetic acid (NAA), both combined with 0.1 mg/L gibberellic acid (GA3). The hormone-free medium (HF) served as a control. The rooting parameters: rooting rate (%), number and length of roots per rooted plant and quality of rooted plants were monitored in the study. The highest rooting rate in both genotypes was obtained on medium with the lowest JA concentration, i.e., 0.2 mg/L (93.3% Pyrodwarf and 40% Gisela 6), this medium also gave the greatest number of roots. Higher JA concentrations (0.5 and 1 mg/L) produced increment in root length. However, rooted plants were grown for longer time period on media supplemented with IBA or NAA. JA applied at 2 mg/L inhibited roots formation in both genotypes. Hormone-free medium had only a marginal effect on rooting in Pyrodwarf (16.7%) where roots were exceptionally long (4.6 cm in average), and had no effect on rooting in Gisela 6 genotype. The obtained results suggest that lower concentrations of JA should be used to improve the rooting process as they ensure a good root system and vigorous, high quality plantlets which, most importantly, are easier to acclimatize.