Response of fruit set and quality and seed formation to ploidy levels of pollen donor in yellow-fleshed kiwifruits

Abstract

This study investigated how the ploidy level of the kiwifruit pollinizer cultivars “CK3” (diploid), “T line” (tetraploid), “Pohwa” (hexaploid) and “Chieftain” (hexaploid) affected fruit set, fruit quality, and seed formation in the tetraploid kiwifruit cultivars “Halla Gold” and “Sweet Gold” cultivated in an unheated greenhouse in Jeju, Korea. Pollen tubes growing in the pistil reached and combined with the ovule 3 days after artificial pollination, and their patterns differed depending on the ploidy level of the pollen parent. The number of pollen tubes observed in “Halla Gold” and “Sweet Gold” pistils was significantly lower following pollination by “CK3” than with the other pollen donors. In all pollen treatments, the fruit set rates were > 90%. The fruit weight of both “Halla Gold” and “Sweet Gold” were high following pollination with “Chieftain” and “Pohwa”. The dry matter content, soluble solids, and acidity were not significantly different among all pollination treatments. Fruit firmness was higher following pollination with “Chieftain” and “Powha.” Colorimeter h˚ values for flesh of “Halla Gold” was low following pollination with “CK3,” but there were no differences for “Sweet Gold” among all pollinations. The number of seeds showed a similar trend to fruit weight, but the 100-seed weight was highest with “T line” as the pollinizer. The results indicate that the ploidy level of the pollen donor affects fruit quality more than fruit set. Also, the pollen most suitable for cultivation of “Halla Gold” and “Sweet Gold” is considered to be tetraploid “T line” and hexaploid “Pohwa” and “Chieftain,” which showed favorable effects on the weight and firmness of fruits, and the number and weight of seeds without adversely influencing fruit set and dry matter content.