Study of Parthenocarpy in Three Kiwifruit Commercial Cultivars

Abstract

To examine parthenocarpy in commercial kiwifruit cultivars in Japan, ‘Rainbow Red’, ‘Kaimitsu’, and ‘Hayward’ cultivars were subjected to four treatments: 1) pistil removal just before flowering; 2) pistil removal just before flowering and soaking with 10 ppm N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU); 3) soaking with 10 ppm CPPU and natural pollination; and 4) artificial dust pollination. The percentage of fruit borne in the pistil removal treatment groups was 0% in ‘Rainbow Red’ and ‘Hayward’, and was 56% in ‘Kaimitsu’. Although 72% had fallen, the fruit borne in ‘Kaimitsu’ was harvestable. CPPU treatment induced parthenocarpy in the three kiwifruit cultivars. There were no viable seeds in the groups with pistil removal, regardless of treatment with or without CPPU. CPPU treatment also promoted fruit maturity at harvesting time in ‘Rainbow Red’ and ‘Kaimitsu’. In ‘Kaimitsu’, parthenocarpic fruits without CPPU treatment were nearly as ripe as pollinated fruits without CPPU treatment at harvest time. After ethylene treatment, fruits ripened, and ethylene was detected in all treatments and cultivars. We confirmed that ‘Kaimitsu’ exhibited fruit development without artificial pollination or CPPU treatment in another season. Furthermore, in ‘Kaimitsu’, parthenocarpic fruits without CPPU treatment were smaller than artificial pollinated fruits, and natural fruit drop was extensive. Thus, parthenocarpy of ‘Kaimitsu’ was thought to be unstable. These results showed that excessive parthenocarpy may be successful in kiwifruit depending on specific cultivars.