ISHS Acta Horticulturae 564: IV International Symposium on Mineral Nutrition of Deciduous Fruit Crops
INCIDENCE OF VASCULAR NODULES IN THE FRUIT OF PACIFIC ROSETM AND RELATED APPLES (MALUS X DOMESTICA BORKH.) |
| Authors: | I. McIvor, S. Lang, P.E. Jameson |
| Keywords: | phytopathogen, tumour, recessive gene, Gala x Splendour, plant hormone |
| Abstract:
Pacific Rose™ is the result of a 1975 cross between ‘Gala’ and ‘Splendour’ and is now an important apple cultivar in New Zealand. This apple has a tendency to develop dense tumour-like masses of small green cells, nodules, within the flesh along the lines of, and close to, the five primary vascular bundles lying opposite the locules. These so-called ‘vascular nodules’ are clearly visible from the early months of fruit development as dark-green blobs. They grow to around 1-2 mm diameter and, close to maturity, can further enlarge and will sometimes develop unsightly, dark-brown centres. They detract significantly from the visual quality of the fruit. There is also concern that they may form a starting point for a more widespread breakdown of the cortex in storage. Vascular nodules have been reported in the literature for the first time only this year (Lane et al., 2000). Based on our observation that they are found only very rarely among commercial apple cultivars, and that they appear (at low frequency) in both Gala and Splendour (these are possibly related), we hypothesise that susceptibility to vascular nodulation is a heritable characteristic and is more-or-less restricted to a particular genetic line - the offspring of Gala X Splendour. Our study records the incidence of vascular nodules in 26 named commercial cultivars, in Gala and Splendour and in 42 siblings of a Gala X Splendour cross including Pacific Rose™. Vascular nodules in the Gala X Splendour siblings tend to occur with either very high or with very low (or nil) frequency. Nodulation in both parents occurs with very low frequency. Within the population of 26 named commercial apple cultivars, vascular nodules were found in only Newton Pippin (excepting Gala and Splendour). Our data suggest that a high frequency of vascular nodulation is the expression of a single homozygous, recessive, possibly mutant, allele inherited from both parents. | |
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