Reproducible differences in yield between sultana vines

Abstract

Differences in yield transmissible by vegetative propagation have been demonstrated in sultanas in the Murray Valley, Australia. Such differences occurred without obvious differences in vine vigour or obvious morphological differences in vegetation or in fruit.
Four pairs of adjacent sultana vines which had shown lar,ge differences in yield within pairs for four or seven years were selected from about fifty uniformly pruned vines on ,each of four vineyards. Vines propagated from these pairs showed corresponding ailld statistically significant differences in yield over four years in nine out of sixteen cases and in no case was there a significant difference opposite to that originally selected.
The ,Mgher yields of the vines propagated from the higher-yielding vines of the selected pairs were mainly due tu more bunches per vine or bigger bunches or both. Measurements of trunk circumference and weight of prunings suggested that they couLd not be ascribed to greater vegetative development.
Although the presence of virus has not yet 'been confirmed, slight virus-like symptoms have been observed on four of the low-yielding selections and the vines grown from them. The other 28 selections and the vines grown from them have shown no sign of such diseases nor of any morphological differences between them.
What,ever the reason for the differences it is clear that selection for yield should be valuable in increasing productivity of sultanas in Australia.