Gene flow in cherry orchards.

A survey of Australian cherry orchards identified the cherry cultivars Sunburst, Summit, Merchant, Sam, Sylvia, Tieton, Kordia, Regina, Empress, Nordwunder and Ulster as having low fruit-set associated with poor pollination. Unique orchard sites across Australia where low fruit-set was not a problem for these cultivars were located, and pollen gene-flow-analysis conducted using 6-PGD, GOT, G6PD, GPI, IDH, FDP and SKDH isozyme markers. Pollenisers for the above-mentioned cultivars were determined and Stella was a polleniser for eight of them. Stella's predominance was linked to it reaching full bloom before the other cultivars; anther dehiscence occurs sometime after flowers open, as such newly opened flowers; the most-fertile stage was mainly exposed to Stella pollen. Sunburst a self-compatible cultivar showed no evidence of self-fertilisation. The majority of pollenisers were found to be within 20 m of the tree under examination. Isozyme profiles for 22 cultivars not previously analysed are also presented.