Pollinating kiwifruit

What usually happens when you cut up a piece of fruit to eat or to put in a salad? If it is an apple, a pear, a peach or a plum, you probably cut out the seeds and put them in the compost bin. But it’s different with a kiwifruit. Most kiwifruit have about 1,000 tiny seeds, and they give the fruit an interesting, crunchy texture so we leave them in. Growers want their kiwifruit to have lots of seeds because it means the fruit will be bigger.

Kiwifruit seeds

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When a kiwifruit flower is well pollinated, it produces plenty of seeds. The more seeds, the heavier the fruit, which is often what growers want.

Rights: The University of Waikato Te Whare Wānanga o Waikato

To get seeds in a kiwifruit, a female flower must be pollinated – the more pollen it gets, the more seeds it produces. Kiwifruit flowers are pollinated by insects, but the flowers are a bit unusual. The male and female reproductive parts are in separate flowers, which grow on separate plants. Insects need to collect pollen from male flowers and take it to female flowers. Fruit only grows from the female flowers, so growers put a few male plants amongst many female ones.

Pollination problems

Kiwifruit flowers do not have nectar to attract insects. If there are other flowers around a kiwifruit orchard, insects may visit them instead. Another problem is that female flowers produce ‘fake’ pollen to attract insects. It is not the same as male pollen because it does not contain genetic material or food. Both of these problems make it tricky to grow lots of big kiwifruit.

Kiwifruit flowers

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Kiwifruit have male and female flowers on separate vines. Female flowers have no nectar but use fake pollen to attract pollinating insects.

Rights: The University of Waikato Te Whare Wānanga o Waikato

Kiwifruit growers often use artificial pollination to make sure their plants get all the pollination they need. People collect pollen by hand from male flowers and spread it onto female flowers. Scientists are trying to find the best way to do this, including when to pollinate kiwifruit flowers and how much pollen to use.

The RoboBee

Dr Mark Goodwin and Dr Paul Martinson at Plant & Food Research are developing a machine called a RoboBee that can sense which flowers are female and spray pollen directly on to them. Normally, pollen is sprayed over the whole vine so a lot is wasted when it lands on leaves. Collecting and processing male pollen is very expensive, so the RoboBee will save a lot of pollen wastage.