Dr Mark Goodwin of Plant & Food Research explains what artificial pollination is and why it is needed for kiwifruit. Some work of the company PollenPlus™ is shown, including their QuadDuster spraying pollen onto kiwifruit vines. Mark describes research he is doing on honey bees and kiwifruit pollination, with footage of research associate Heather McBrydie working on kiwifruit vines.
DR MARK GOODWIN
Artificial pollination is where human beings come in and actually add pollen into the system to do more than what just the insect pollinators are doing, and for kiwifruit, what we do is we harvest flowers, we mill them to remove the pollen and then apply it back on the flowers using a whole lot of different methods.
Growers use artificial pollination because we’re finding, over the last 10 years or so, that the bees aren’t doing as good a job as they used to.
We’ve got a whole lot of new varieties that we actually don’t know how to artificially pollinate, so we have to work out the parameters around when to put the pollen on and how much pollen you have to put on to get really good fruit out of it.
The first question we have to ask is how long the flowers are viable for. If they’re only viable for 1 day, you have to put pollen on every day. If they’re viable for a week, all you’ve got to do is come and put it on once a week. To work out the viability, what we do is, every day when the flowers open, we put paper bags over the flowers before any insects get to visit them, and we do that every day so that, at the end of a week, we’ve got flowers that are 1 day old, 2, 3, 4, 5, 6 or 7 days old, take all the bags off, pollinate them, put the bags back on and see which ones set fruit.
The way we work out how much pollen you have to put on to get a full-sized fruit is we take a whole lot of flowers and we put on different concentrations of pollen. The next thing we have to do is take half the flowers, cut off the stigmas, wash them and to count the number of pollen grains so we can get a relationship between the rate, the number of pollen grains that ended up on the stigma and the number of seeds that have been produced.
The other question we have about this new variety is that fruit shape – size and shape – is very variable, and we’re trying to work out why. One obvious possibility is it’s all pollination, that the bees are really not doing a good enough job here. So what we wanted to know was how many bee visits you actually had to get to these flowers to get them fully pollinated.
The way that we work out how many bee visits you need to fully pollinate a flower is that we put bags over flowers before they open, and when the flowers open, we take the bags off – we just stand there and watch them and wait for a bee to come and visit them. When a bee’s visited them, we put the bag over, let it develop into a whole fruit, remove the fruit, count the number of seeds and from that we know how many seeds are being produced from each bee visit.
The green kiwifruit needs something like 40 bee visits to every flower to fully pollinate it. If we find that they’re not getting enough bee visits, we have a number of options. One of them is to increase the number of beehives so there’s more bees visiting the flowers, or if that’s not possible, we use artificial pollination on top of what the bees are doing.
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