Pollination requirements of kiwifruit (Actinidia chinensis Planch.) differ between cultivars ‘Hayward’ and ‘Zesy002’

Abstract

Pollination by insects is critical for the production of many crops worldwide. Crop cultivars vary in a number of traits, but their differing pollination requirements are often overlooked. Kiwifruit (Actinidia chinensis) is reliant on pollen movement between male and female plants, but there has been disagreement in the literature about what its pollination requirements are. Additionally, there is little information about how time-of-day might affect fruit and seed set, and how this may alter the efficacy of pollination management strategies. In this study, we compare the pollination requirements of A. chinensis var. deliciosa 'Hayward' (a hexaploid green-fleshed variety) and A. chinensis var. chinensis 'Zesy002' (a tetraploid gold-fleshed variety). We find that 'Zesy002' requires fewer pollen grains than 'Hayward' for full seed set. Kiwifruit appears to be equally able to set fruit at any time of the day, meaning that insects which forage outside the peak hours of 0900-1500 h may play an important supporting role in fruit production, and that artificial pollination could profitably be applied into the evening hours rather than being limited to the period of peak pollinator activity.

Pollinator identity and behavior affect pollination in kiwifruit (Actinidia chinensis Planch.)

“…As kiwifruit can produce fruit regardless of the time-of-day pollination occurs ( Broussard et al, 2021 ), pollination need not be limited to peak honey bee foraging hours (late morning to early afternoon). There is the potential for other pollination strategies to compliment managed honey bees, including alternative insect pollinators and artificial pollination.…”

“…Of note is that gold-fleshed kiwifruit appear to have a lower pollination requirement than green kiwifruit ( Broussard et al, 2021 ), with green-fleshed ‘Hayward’ requiring 8x the insect visits of yellow-fleshed varieties ‘Hort16A’ and ‘Zesy002’ ( Broussard et al, 2021 ). This means that non- Apis pollinators, even those who deposit less pollen per visit, may have a greater part to play in these cultivars, as the number of grains they do deposit represents a larger percentage of the overall requirement.…”

“…As well as providing significant potential for complementary pollination services, pollinator diversity can reduce an over-reliance on a single species. This is particularly pertinent in the case of gold-fleshed kiwifruit cultivars which appear to have lower pollen requirements ( Goodwin, McBrydie & Taylor, 2013 ; Goodwin et al, 2017 ; Broussard et al, 2021 ): less efficient insects could have a higher proportional impact where fewer pollen grains are required as each visit would deliver a higher proportion of the total required pollen, while highly efficient insects may deliver more pollen than necessary.…”

Artificial Pollination Technologies: A Review

“…A third option is available for selected, self-compatible crops-such as tomato-where vibrating the floral structures, either through direct contact or with a puff of air, shakes loose pollen to fertilize the flower [59]. Most application literature measures results directly in terms of fruit or seed set, as pollen requirements have been characterized for relatively few crops [60][61][62][63]. Research has shown that liquid-carrier (or dry diluent composition) formulation, temperature, time of day, weather, stigma receptivity, and flower age all influence pollination efficacy [41,61,[64][65][66][67][68].…”

“…Dry application has two important advantages over wet pollen application: Most application literature measures results directly in terms of fruit or seed set, as pollen requirements have been characterized for relatively few crops [60][61][62][63]. Research has shown that liquid-carrier (or dry diluent composition) formulation, temperature, time of day, weather, stigma receptivity, and flower age all influence pollination efficacy [41,61,[64][65][66][67][68]. These factors are largely ignored in much of the work published on alternative pollination systems.…”