Vol. 75 No: 4

Title:
In vitro performance at high culture pH and in vivo responses to Fe-deficiency of leaf-derived quince BA 29 (Cydonia oblonga) somaclones regenerated at variable medium pH

Authors:
GRAZIA MARINO, SIMONE BEGHELLI, ADAMO DOMENICO ROMBOLÀ and LUCIA CABRINI

pp: 433-440

Abstract:
The aims of the work were to obtain quince (Cydonia oblonga) BA 29 somaclones tolerant to high culture pH and lime soils, to test the effectiveness of in vitro selection methods based on the selection pressure exerted by pH during regeneration, and to understand the mechanisms for the improved performance under Fe-deficient conditions of eventually tolerant clones. Leaf-derived somaclones obtained at variable medium pH (5.7, 6.0, 6.5, 7.0 and 8.0) were compared with each other and with the control (i.e. shoots derived from BA 29 mother plants by standard micropropagation) for their in vitro growth, proliferation, rooting performance and pH-reducing ability at pH 7.0, 7.5 and 8.0, and for their Fe-chelate reductase (FCR) activity and soluble sugar and organic acid accumulation in the roots and leaf chlorophyll content when grown in soiless culture under Fe-efficient and -deficient conditions. Preliminary results on SPAD analysis on leaves of the same plants transferred to lime soil are also reported. The effect of pH selection pressure was not very clear; however, while all the clones hardly grew and proliferated in vitro at pH 8, the somaclones regenerated at pH 7 generally tended to have better growth and proliferation than control and other somaclones at pH 7.5, especially 7-A. In contrast, most of those regenerated at low pH, but 5.7-A, tended to have lower proliferation rates and shorter axillary shoots. Little differences were found in the rooting performances of the clones, although most somaclones seemed more able to reduce the pH than the control. After 10 d in hydroponic culture under Fe-deficient conditions, almost all the somaclones tended to have some FCR induction in the roots; however, it was detected only in 5.7-A and 7-A at day 30. Leaf chlorophyll determinations in soiless culture and lime soil indicated quite good tolerance to Fe-chlorosis for 6-A, 7-A and especially 5.7-A. When the in vitro and in vivo results are considered together, the somaclones 5.7-A, 7-A and 6-A seem the most interesting, their success in growing in Fe-deficient conditions being probably due partially to sorbitol accumulation in the roots, in particular for 6-A and 5.7-A, and also to inositol and citric acid, respectively for 5.7-A and 7-A. However, further plant evaluation on lime soil is needed to verify these preliminary results and to understand whether some of these somaclones can replace the widespread pear rootstock quince BA 29, as more tolerant to lime-induced Fe-chlorosis.

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