Kitchen Science - Home Cloning & Bananas

We've only recently been able to clone animals, but we've actually been cloning plants for millennia, thousands of years.  So for this week's Kitchen Science, Ben found out about a clone you can clone at home!

Ben -   For Kitchen Science this week we decided that we would talk to you about how you can clone an organism in your own home.  That's right, you can actually clone something yourself at home and it's really easy.  I'm actually here at Cambridge University Botanic Gardens and I'm with Tim Upson.  Hi Tim!

Tim -   Hi there.

Ben - We are looking into cloning plants today, now the cloning we've heard about so far involves expensive lab equipment and carefully removing DNA from one cell and putting it into another.  So is that how you do it with plants?

Tim -   No, well thankfully plants are much easier. You can snap off a bit, stick it in some soil and wonderfully it will produce some new roots and you've actually cloned a plant.  It's the process of taking cuttings which millions of gardeners will do every year.

Ben -   So what is it that makes that new plant a clone?

Tim -   It's because it's genetically identical to the parent. So in contrast if you were to sow some seeds, which have come about through sexual reproduction, of course that's mixing of the genetic material and you get variation.

Ben -   So literally all you have to do to clone a plant at home is to cut a piece of one plant and plant it in the soil.

Tim -   Yes, plants have this wonderful property; their cells can re-differentiate into different materials.  So essentially if you take a shoot from a plant it will have leaves and it will have a stem.  Usually just underneath the surface of that stem some of those cells, in response to wounding and being cut will actually differentiate into roots.  These are called adventitious roots, new roots, and hey presto you've got a plant with all its functioning parts the leaves, the stem and of course, the roots.

Ben -   So it's the ability to differentiate into different cell types that means a plant can do this, but do you know why I wouldn't be able to cut off the tip of my finger and plant it in some agar and grow a whole extra hand?

Tim -   Yes, in animals they don't have this ability to differentiate cells once they've become a certain part of the body.  Unless, I guess, you go all the way back to stem cells which have a similar kind of ability to plants.

Ben -   So could you consider plant cells to be very similar to stem cells in that regard?

Tim -   Yeah, I think that's a good analogy actually.

Ben -   So how do we know that plant cells are capable of turning into all the different cell types?

Tim -   We now know that all of these are controlled by what are sometimes called plant hormones or plant growth compounds.  A good example is a hormone called Auxin, which encourages rooting.  When you go to the garden centre you can buy what's called a plant rooting compound, and that's high in auxins so when you dip the end of your shoot, which you've just broken off, into that powder it gives it a burst of auxin and that encourages the roots to develop.

Ben -   This sounds like a really good way for us to get more, and different, plants into our gardens.  Are there any problems associated with having plant clones?

Tim -   Well there are.  One good reason for cloning is because you find a plant which has very good characteristics; maybe it has a particularly delicious fruit or wonderful flower.  But of course along with that can equally go some negative characteristics.  That can be particularly problematic for example when we talk about susceptibility to pest and diseases.  If you do then get an outbreak of it and you've got a mass of clonal plants on an agricultural scale that could spell disaster if you're a farmer.

Ben -   So a farmer would clone a particular plant because, for example, it's the best banana and the easiest to sell, so for commercial reasons cloning would make sense because you'll get more of the best type of fruit.

Tim -   That's exactly right and bananas are a very good example.  Bananas are cloned on a commercial scale, if you go to the tropics and look at the commercial banana plantations they're usually made up of clonal lines of selected cultivars.  Bananas are synonymous with something called panama disease which is a fungal disease which actually attacks the water conducting vessels.  Some of the favoured banana clones like Gros Michel and now Cavendish bananas which are grown widely throughout the world for commercial purposes have become vulnerable to this fungus.  As soon as it starts to attack a field, or essentially move from country to country it can devastate that banana industry, so it can cause big problems and we are talking potentially multi-million pound loss of crops here.

Ben -   So how can we avoid this happening?

Tim -   Well, it all comes back to encouraging genetic diversity and all we have to do is to look to people like subsistence farmers, they wouldn't just grow one clone they would grow a number, so if one proved potentially vulnerable to pest and disease they've got others that they can look to.  Commercially, of course, now they're looking to breed more diversity into bananas and of course breeding in resistance particularly to panama disease is obviously very important and a major goal.

Ben -   So while cloning can offer us more and better fruit, it's always best to remember that it would only take a small outbreak of disease to take bananas off the shelves.  That's all for Kitchen Science today, we'll be back next week.