Seed attributes in fruit of colchicine-induced tetraploids of Actinidia chinensis

• This is the first time to describe the three methodologies developed and integrated together to study Actinidia seed number, quality and development, and systematic analysis of seed property in diploid golden-fleshed kiwifruit and red fleshed kiwifruit, and their colchicine-induced tetraploids.
• Colchicine-induced tetraploids had a significantly lower seed density in transverse sections of fruit, fewer normally filled seeds, and more unfertilized and aborted seeds than their corresponding diploid progenitors.
• The weight of filled seeds of colchicine-induced tetraploids from golden-fleshed ‘Hort16A’ was significantly (33%) higher than that of their diploid progenitor, but the weight of filled seeds from colchicine-induced red-fleshed kiwifruit was significantly lower than their respective diploid progenitors, all of these maybe have been mainly related to the availability of pollen of nearby the same ploidy pollenizers.
• However, the less number of filled seeds does not affect their large fruit character of autotetraploids.

Seed characteristics are important in kiwifruit breeding and production as they affect the efficiency of cross breeding and commercial fruit size and quality. Following a study of the size, shape and quality attributes of induced tetraploid kiwifruit, three methods for seed evaluation were compared to uncover the effect of chromosome doubling on seed development, quantity and quality in induced tetraploids of Actinidia chinensis. Results over 3 years consistently showed that colchicine-induced tetraploids had a significantly lower seed density in transverse sections of fruit, fewer normally filled seeds, and more unfertilized and aborted seeds than their diploid progenitors. The weight of filled seeds of colchicine-induced tetraploids from the commercial gold-fleshed kiwifruit cultivar ‘Hort16A’ was significantly (33%) higher than that of their diploid progenitor. In contrast, the weight of filled seeds from the fruit of colchicine-induced red-fleshed A. chinensis tetraploids was significantly lower than that of their respective diploid progenitors. Seed size may have been related mainly to the availability of pollen from nearby males of the same ploidy. The dry seed coat colour of colchicine-induced tetraploids was brown in comparison to the black seeds of diploids. This is the first time that the reproductive nature of autotetraploid kiwifruit has been systematically characterized. I have shown that chromosome doubling significantly reduces seed numbers and affects seed development inside kiwifruit.