Cytokinins antagonize the jasmonates action on the regulation of potato (Solanum tuberosum) tuber formation in vitro

Abstract

The effects of jasmonic acid (JA) and methyl jasmonate (MeJA) on potato (Solanum tuberosum L.) tuberization were studied in relation to cytokinins using single-node cuttings (SNCs) in vitro. In three potato cultivars differing in maturity levels, JA or MeJA (0.0, 2.5, 5.0, 7.5 and 10.0 μM) action was examined with N6-benzyladenine (BA: 0.0, 22.0 and 44.0 μM) under optimum tuber-inducing treatment with 80 g L−1 sucrose. Although jasmonates had a stimulatory role in root growth from SNCs, BA inhibited the root growth and antagonized the jasmonates action on root growth promotion. There was a strong inhibitory effect of BA on stoloniferous shoot growth, and in combination with jasmonates it could exert a much pronounced inhibitory effect. Jasmonates did not have any role in tuber induction in terms of tuber number and source-sink coordination (harvest index), rather their effects were counteracted in the presence of 22.0 μM BA in early cultivar. However, they had a promoting effect on tuber growth after induction in early cultivar, possibly due to its lower levels of endogenous gibberellins. Cytokinins detrimentally affected the tuber growth, and antagonized the jasmonates action irrespective of the maturity levels of the cultivars. It could, however, increase the tuber dry matter concomitant with a higher accumulation of starch. The promoting effect of jasmonates on tuber dry matter and starch accumulation was apparent only in early cultivar. There were significant interactions between cytokinin and jasmonates for accumulation of reducing and total sugars in tubers. The results show that exogenous cytokinins antagonize the jasmonates action, and the correlated effects of these two growth hormones interact with the maturing time of the cultivar during potato tuber formation in vitro.