Nitric oxide in combination with indole-3-butyric acid improves root growth in Ferdor Julior' hardwood cuttings (Prunus insistitia (L.) x Prunus domestica (L.))

The production of plants for high density fruit orchards requires a highly efficient clonal propagation method. Ferdor Julior' rootstock is well adapted to different soil conditions, but its natural rooting potential is very limited. Propagation treatments, such as bottom heat and indole-3-butyric acid (IBA) applications have previously been used to improve rooting. The aim of this work is to evaluate the effects of either IBA, or sodium nitroprusside (SNP; a nitric oxide (NO) donor), or a combination of both on the rooting of hardwood cuttings of 'Ferdor Julior'. As metabolism markers, ascorbic acid (AA) and glutathione (GSH) were measured in adventitious roots. 'Ferdor Julior' hardwood cuttings were treated as follows: untreated, 0.3 mM IBA, 1 mM SNP, 1 mM SNP previously exposed to light (as a negative control), and 1 mM SNP + 0.3 mM IBA. After 4 months, the combined use of SNP and IBA had increased root growth and lateral rooting, but resulted in less shoot growth, whilst AA and GSH concentrations were also reduced. IBA and SNP individual treatments showed intermediate results, compared to untreated cuttings. According to the results obtained, there may be an additive effect of auxin and NO signaling pathways. In conclusion, this new and promising technique for Ferdor Julior' propagation could improve lateral root development and promote early lateral root growth.