Pollen effects on fruit attributes and seed properties in colchicine-induced autotetraploids of red-fleshed kiwifruit (Actinidia chinensisPlanch.)

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Abstract
The effect of the ploidy level of the polleniser has not been considered during the characterisation and evaluation of colchicine-induced autotetraploids of Actinidia chinensis (kiwifruit). It is therefore possible that few induced autotetraploids reach their potential size. Five genotypes of tetraploid pollenisers were used for controlled pollination of red-fleshed autotetraploids. Fruit of colchicine-induced autotetraploids from two genotypes of female red-fleshed A. chinensis plants were, on average, 25–30% larger than fruit arising from open-pollination in an orchard containing only a diploid male as polleniser. Fruit dimensions increased more in cross-section than in length, so the fruit were more round. Seed set increased up to two-fold and the number of filled seeds also increased significantly (P ≤ 0.01). The average filled-seed weighed two-to-three times more than that of seed from open-pollination with pollen from a diploid male, and were heavier than those in fruit of their diploid progenitors under open-pollination. The distribution of the red-flesh pigmentation increased, although its intensity was not significantly improved. The total soluble solids content (TSSC) increased by 1–2% and the size of the core cavity at the stylar end was significantly reduced (P ≤ 0.01) and sometimes completely. All these effects on fruit attributes would benefit the commercial cultivation of red-fleshed kiwifruit. It is therefore recommended that, as for diploids, pollenisers of tetraploid red-fleshed kiwifruit should be of matching ploidy. Two abnormal fruit with soft red cores were found on a branch of a tetraploid regenerant during the evaluation of fruit generated by controlled pollination. The possible origin and application of this mutation for novel kiwifruit breeding are also discussed.

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