Vol. 73 No: 5

Title:
Selection-Pressure Effects of Medium Ph During Regeneration on Successive Performances of Leaf-Derived ‘Tomuri’ and ‘Hayward’ Kiwifruit (Actinidia Deliciosa) Somaclones Cultured on Proliferation Culture Media with Variable pH

Authors:
GRAZIA MARINO and GIANPAOLO BERTAZZA

pp: 664-669

Abstract:
The aims of the work were in vitro selecting for tolerance to high culture pH (CpH) in kiwifruit and evaluating the effects of selection pressure exerted by pH variations during regeneration. Leaf-derived ‘Tomuri’ and ‘Hayward’ kiwifruit (Actinidia deliciosa) somaclones, which had been regenerated at pH 5.7, 7 and 7.5, were compared to each other and to controls (i.e. cultures derived from ‘Tomuri’ and ‘Hayward’ mother plants through standard micropropagation techniques) for shoot growth, proliferation and appearance when cultured at up to pH 8. The proliferation rate (PR), the number of nodes (NN) produced by each shoot and axillary shoot length (ASL) decreased in all ‘Tomuri’ and ‘Hayward’ somaclones and in controls as culture pH increased. At CpH 8, ‘Tomuri’ somaclones regenerated at pH 7.0 generally tended to have higher average PR and NN than the other somaclones and control; their ASL also exceeded that of the other somaclones and was just slightly higher than in control. Regardless of CpH, ‘Hayward’ somaclone 7.5–1 tended to have higher PR, NN and ASL than other female somaclones. When shoot growth and appearance (tissue hyperhydricity, leaf yellowing or browning) were considered together through a multivariate data analysis, most ‘Tomuri’ and ‘Hayward’ somaclones which appeared less sensitive than controls to high CpH had been regenerated at pH 7 and 7.5. These regeneration and culture methods, especially the selection pressure exerted by the high pH during regeneration, thus seem to be effective in obtaining ‘Tomuri’ and ‘Hayward’ variants tolerant to high culture pH.

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