| Endogenous
hormones and phenols of seedling trees of polyembryonic mango cultivars
and their role as rootstocks in scion vigour of cv. Alphonso. |
| Murti, G. S. R.,Upreti, K.
K.,Kurien, R. M.,Reddy, Y. T. N. |
| Plant
Hormones Laboratory, Indian Institute of Horticultural Research,
Hessaraghatta Lake Post, Bangalore 560 089, India. |
| Changes in
the levels of endogenous hormones, abscisic acid (ABA), cytokinins (t
-zeatin riboside (t -ZR) and dihydrozeatin riboside (DHZR)) in xylem sap
and leaves and indole acetic acid (IAA) and total phenols in the leaves
were determined in seven polyembryonic mango cultivars (Bappakai,
Chandrakaran, Furukan, Muvandan, Mylepelian, Olour and Vellaikolamban),
which are commonly used as rootstocks. Simultaneously morphological
characters were recorded on mango cv. Alphonso of similar age raised on
these cultivars as rootstocks to examine whether the hormones and
phenols produced by these bear any relationship to the growth and
development of scion. Also the stem anatomical features of the shoots
of current and previous year growth were studied in Alphonso grafted on
two rootstocks imparting contrasting effects on shoot vigour. The
morphological attributes such as tree girth and tree volume of Alphonso
were generally higher on rootstocks Muvandan, Bappakai and Olour and
least on Vellaikolamban followed by Kurukan and
Chandrakaran/Mylepelian. The ratio of radial width of phloem to xylem
tissue was higher in the shoots of current year growth of Alphonso
raised on dwarfing rootstock, Vellaikolamban, than the vigour imparting
Olour. Xylem sap yield was higher in Mylepelian, Muvandan, Olour and
Chandrakaran and least in Vellaikolamban. Lower levels of ABA and higher
levels of cytokinins, t -ZR and DHZR, in the sap and leaves, and IAA in
leaves were evident in the seedling trees of Muvandan and Olour. The
trends were opposite with respect to these hormones in Vellaikolamban,
Kurukan and Bappakai. Leaf phenol content in different cultivars showed
similar trends as of ABA. The cultivars that impeded the tree vigour of
Alphonso when used as rootstocks yielded lower sap volume and had
higher levels of ABA and phenols and lower concentration of cytokinins
and auxin. Screening of the polyembryonic cultivars at the initial
stages for ABA or phenols in the leaves is suggested for their
selection as rootstocks for vigour regulation. |
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