In vivo growth and tolerance to lime-induced iron chlorosis of leaf-derived cvs. Tomuri and Hayward kiwifruit (Actinidia deliciosa) somaclones

Summary

The present paper reports on somaclonal variation of leaf-derived ‘Tomuri’ and ‘Hayward’ somaclones regenerated at variable pH, and the effect of the in vitro selection pressure on their tolerance to lime-induced iron chlorosis as adult plants in pots and in the field. In most plants grown in pots, the above ground component length (AGL) and the node number (NN), and also root weight of ‘Hayward’, tended to increase with the regeneration pH (RpH). The higher vigour of ‘Hayward’ somaclones regenerated at high pH seemed to be confirmed in the field. In contrast, the pH selection pressure during regeneration had no clear effect on plant tolerance to lime. For ‘Hayward’, the group of somaclones obtained at pH 5.7 showed at high lime levels higher average AGL and NN than those of plants regenerated at pH 7; while clone 7.5-1, the only surviving somaclone among those obtained at the highest pH, was apparently the most tolerant to lime. The percentage of ‘Tomuri’ somaclones obtained at pH 7.5 that seemed less sensitive to lime was slightly higher than those of somaclones regenerated at pH 5.7 and 7. ‘Tomuri’ and ‘Hayward’ controls were both very sensitive to lime. Some somaclones which had been able to grow at high pH in vitro were also fairly tolerant to lime when cultured in pots and/or in the field, especially ‘Tomuri’ 5.7-5, -6; 7-6, -8, -14 and 7.5-6, and ‘Hayward’ 5.7-5; 7-2, -3, -5 and 7.5-1. The in vitro regeneration and selection methods here described therefore seem useful for creating and selecting new variability in kiwifruit and promising for obtaining plants tolerant to high pH and lime levels in the soil.