BIOCHEMICAL AND MORPHOLOGICAL CHANGES IN MICROPROPAGATED SHOOTS OF GISELA6® (PRUNUS SPP.) ROOTSTOCK INOCULATED WITH TRICHODERMA HARZIANUM STRAIN T-22
Trichoderma harzianum strain T-22 (T22) has the ability of enhancing root growth and plant development. The aim of this research is to explain the biochemical basis of the direct plant-growth-promoting activity of T22. Seven days after the transfer to root-inducing medium, in vitro-cultured shoots of GiSeLa6® (Prunus cerasus × P. canescens), an important Prunus rootstock for sweet and sour cherry cultivars, were inoculated with T22. Root and shoot growth were significantly affected by T22 (+76 and +61%, respectively). Indole-3-acetic acid (IAA), trans-zeatin riboside (t-ZR) and dihydrozeatin riboside (DHZR) were analyzed by HPLC/MS. Acidification of the medium by plant, T22, and plant + T22 were assessed, whereas root morphological changes were observed by light and epifluorescence microscopic analysis. Nine days after inoculation, the levels of indole-3-acetic acid (IAA), trans-zeatin riboside (t-ZR), dihydrozeatin riboside (DHZR), gibberellic acid (GA3) and abscisic acid (ABA) were analyzed by high performance liquid chromatography coupled with mass spectrometry. The results showed that after T22-inoculation, IAA and GA3 significantly increased in both leaves (+49 and +71%, respectively) and roots (+40 and +143%, respectively) whereas t-ZR decreased (-51% in leaves and -37% in roots). Changes in DHZR were observed in T22-inoculated roots (-32%) but not in leaves, whereas the levels of ABA did not differ between the two treatments. Root activity determined a decline of medium acidity, and this effect was more marked in T22-inoculated plants (up to pH 4). Microscopic analysis revealed changes in root cell wall suberification in the exoderm and endoderm, with an increase in suberized cellular layers from 1 to 2-3, and an enhancement of cell wall epifluorescence. All these T22-induced changes promote rooting and shoot growth, and they could increase plant survival during the acclimatisation phase of nursery processes.
Sofo, A., Tataranni, G., Scopa, A., Dichio, B. and Xiloyannis, C. (2012). BIOCHEMICAL AND MORPHOLOGICAL CHANGES IN MICROPROPAGATED SHOOTS OF GISELA6® (PRUNUS SPP.) ROOTSTOCK INOCULATED WITH TRICHODERMA HARZIANUM STRAIN T-22. Acta Hortic. 961, 487-494
auxins, cytokinins, microscopic analysis, root acidification capacity, root growth, root suberification