VARIABILITY IN THE EXPRESSION OF EXTERNAL KNOBBLINESS AND POLLINATION RESPONSES IN THE PEAR CULTIVAR PACKHAM'S TRIUMPH

The influence of the polleniser, growing site, season and fruit size on the knobbliness of European pear (Pyrus communis) cultivar Packham's Triumph was investigated over two seasons in Nelson, New Zealand. Five pollenisers were used to pollinate Packham's Triumph flowers at each of three sites in 1990–91 and 1991–92. Pollen was applied at an uncontrolled rate. Fruit were scored using a visual scale of fruit knobbliness at harvest.

Fruit were more knobbly in 1991–92 than in 1990–91. There was a relationship between increased fruit size and increased knobbliness. In both 1990–91 and 1991–92 there was a relationship between polleniser-type and fruit knobbliness and there were also differences in the external knobbliness of fruit from the different sites with the influence of polleniser-type being growing site variable. However, there was no overall influence of polleniser-type.

The cell size 400, 650 and 1000μm from the cuticle was larger in smooth fruit than in knobbly fruit at three stages of fruit development but the difference was more pronounced at harvest.

The growing site and, more particularly, the season may have a marked influence on external appearance of Packham's Triumph pears. Cooler conditions throughout pollination and fruit development are probably responsible for increased expression of external knobbliness in Packham's Triumph. Harvesting less mature fruit may help reduce the incidence of knobbliness.