In this article:
Woodham and Alexander (1966) demonstrated differences in yield between Sultana vines which were reproducible in vines propagated from them, but did not establish reasons for the differences at that time.
Possible reasons would include genetic variation and differences in infection with virus diseases.
This paper reports investigations into the virus status of the selections in the original trial and the effect of graft inoculating a high yielding selection with buds from a number of other selections.
Differences in yield between Sultana clones were found to be partly transmissible by grafting and partly not. The most important graft transmissible factor was leafroll.
Yield differences not transmissible by grafting ranged up to about 50 %.
Yield Differences between Sultana Clones related to Vitis Status and Genetic Factors
1984, Vitis, vol 23, pages 73-83
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