DNA CONTENT OF NUCLEI OF ACTINIDIA-DELICIOSA VAR. DELICIOSA HAYWARD (KIWIFRUIT) ANALYZED BY IMAGE CYTOMETRY

Static image cytometry (ICM), computer-enhanced, optical microscopy was used to determine the DNA content of Feulgen-stained nuclei derived from in planta and in vitro shoots of kiwifruit (Actinidia deliciosa var. deliciosa 'Hayward'). Nuclei in meristem tips, analysed from the same vines, showed alterations in the nuclear DNA content between successive years. These findings correlate closely with flow cytometric analysis of meristem tips of the same vines. The absolute nuclear DNA content for the samples analysed by ICM lay between 5.58 pg DNA per 2C nucleus (spring 1991) and 7.96 pg DNA per 2C nucleus (spring 1992), an increase of 42.5%. The 2C nuclear DNA content of plantlets grown in vitro for 3 years displayed no significant differences, irrespective of the duration on fresh culture medium. The 2C nuclear DNA content of cells from the meristem tips of these plants was approximately 6.71 pg DNA, lower than the high point recorded from in planta apices. These estimates were significantly higher than those obtained by flow cytometry. Nuclei of meristematic cells of in planta shoots also showed an increased nuclear DNA content between analyses 13 days prior to bud burst and again 1 day after bud burst.