What is a Plant Improvement Scheme and how does it work? Take Lychees for example. These tend to bear erratically to varying degrees but a few trees in an orchard seem to bear more regularly than others and perhaps one or two particular trees bear very good crops of fruit every year without fail. It is the same with just about every tree crop in the world.
TREE CLONAL SELECTION
In a well-established orchard a grower knows where these good trees are. In a selection programme, usually conducted by the local DPI in conjunction with a grower group and with the participation of a local nurseryman, the best tree in each of the group's orchards is identified, given a number and clearly marked on a map of the property.
Later on, these SELECTED TREES are marcotted and the rooted marcots grown on by the nurseryman and eventually planted out in a TRIAL PLOT on one of the group's orchards.
THE TRIAL PLOT
Say for example 20 marcots are taken off each selected tree. When grown on, these 20 trees become what is known as a CLONE, all exactly the same as the single selected mother tree from which they came.
If 10 selected trees are identified in 10 different orchards, the trial plot will therefore have 10 different clones and each tree position of each of these 10 numbered clones is clearly marked on a map of the trial plot.
For scientific purposes, the clones should be randomised throughout the trial area. Thus the lucky grower who gets the trial plot has a whole orchard of well-above-average cropping trees. These trees are generally classified as IMPROVED MATERIAL if any marcots are taken from them.
TO FIND THE BEST CLONE
Once cropping commences, the fruit from each tree is weighed after each picking and after three or four years of recording the yields of each clone, the heaviest bearing clone is identified. Fruit quality must also be assessed.
Say clone No.7 was found to be the best one, then that IS the clone that is propagated for the industry.
Any commercial grower, hobby farmer or home gardener who plants clone No.7 is therefore guaranteed to pick a good crop of fruit every year without fail. No biennial bearing, providing of course that the trees are adequately watered and fertilized.
Picking and weighing fruit costs lots of money. The labour cost to harvest a trial as described above is usually funded both by industry and government.
If no money is forthcoming, then a purely visual assessment can still be made, if not of the best clone, then at least the worst clones can be identified and no further marcots taken from them.
Sometimes it is hard to visually pick out the best clone of all. The top five clones for example may all look much the same when looking at the fruit ripening on the trees.
The proper way to assess the trial is to pick and weigh fruit from each tree for at least three harvests.
Ultimately, once the best clone is identified, a whole block of trees of this one clone is then planted, from which large numbers of marcots can be taken in future. This is known as a REGISTERED SOURCE AREA and the owner is paid a royalty for any marcots taken from his trees.
Being comprised of only the very best clone, the source area will produce yields of fruit far in excess of the average for the district. For example, the Apricot Improvement Programme in South Australia resulted in a three-fold increase in yield compared to the district average.
A COMPREHENSIVE SCHEME
The above describes a typical clonal selection programme, but of course a comprehensive scheme embraces such other programmes as variety and rootstock trials, plant introduction, virus indexing, hybridization and tissue culture.
Having been involved in tree fruit improvement schemes for the South Australian DPI, it is interesting to make a comparison with what is happening with Rare Fruits in North Queensland.
WHAT IS AVAILABLE AND WHERE CAN YOU GET IT?
Good question. There is no overall Rare Fruit Improvement Scheme here complete with a selection programme, clonal trials and Registered Source Areas established for the supply of grafting wood and cuttings etc. But there are lots of people selling trees.
When somebody comes up here from the south to settle down and plant a Rare Fruit Orchard, he may hear of a certain 'Joe Blow' down the road who sells fruit trees. So he wanders off down there, buys his trees and plants them, full of hope and expectation.
Five or six years down the track he could still be waiting for results and some of his trees don't appear to be true to label. He then begins to wonder what went wrong.
He would have done a lot better to have joined his local branch of the RFCA in the first place and to have consulted the local DPI officer. Firstly to find out what trees to get for his locality, secondly where to buy them, and thirdly the good oil on how to grow them. Depending on local knowledge, some of this information may be available and some may not.
TABLE GRAPES AND DURIANS
Take the case of the ex-tobacco grower on the Atherton Tableland. Forced out of tobacco, he is now having to look at alternative crops. So, in a fit of enthusiasm, he joins the Table Grape Discussion Group organised by the Mareeba DPI to learn all about Table Grapes, what varieties to grow and where to get them.
No worries. He immediately has ready access to the very best planting material in Australia, the result of years of clonal selection and virus testing.
Almost unlimited numbers of cuttings from State Registered Source Areas, ably administered by local Vine Improvement Committees.
Any number of rootlings or grafted vines from accredited nurserymen under the Australia Wide Vine Improvement Scheme and all vines true to label. Fantastic!
This scheme, originally started in the Barossa Valley of South Australia in 1968, now has committees in all States and in all vine-growing regions within those States.
The Pome and Stone fruit industries are also served by similar schemes in all States.
But what about the chap down on the coast who wants to plant Durians? He would be really pushing up hill! Can he buy trees guaranteed to produce regular crops of a quality acceptable to the market? At this stage I doubt it.
There are introduced varieties planted and bearing and possibly a good selected seedling or two, but have there ever been any variety trials in Australia to establish which are the best performers? And yet, according to a list we have in the Cairns Branch, compiled in 1980, 15 people up here had Durians on their properties at that time, but have any of these trees been assessed? Might be worth having a look at them.
With Abius, there are some excellent selections such as Z2 and Z4 and some named varieties. The same with Carambola. Good backyard trees these. They are readily available from nurseries. But what about Jack Fruit? A very good selected seedling down south was mentioned in one of the Newsletters, but how does one get hold of a plant? Jackfruit seems quite a popular fruit in some circles. The staff at the Flecker Botanic Garden in Cairns complain that as soon as a fruit is nearing ripeness it always seems to disappear during the night!
Perhaps, for assessment purposes, a small observation plot should be planted somewhere of what are currently considered to be the best varieties and selections. Or maybe a windbreak?
Most lychee growers in F.N.Q. are members of the Far North Queensland Lychee Growers Association. The Tai So variety is the main one grown and is in demand for export. A good subject for selection.
It is not difficult to see variability between trees of this variety. Five mature trees on four properties have been selected from Innisfail to Julatten. Each tree was well-known to the grower as having a history of regular cropping and good quality fruit.
Hopefully marcots will be taken off these trees in the future and a replicated plot of the clones planted in one of the members' orchards.
Fay Zee Siu, an up-and-coming new variety is now available locally. The ideal lychee. The fruit is very large with a good appearance and flavour and a small 'chicken tongue' seed. It has been grown long enough now to identify superior trees. Fay Zee Siu clone No.3 has been selected and will eventually be made available as potted marcots once the Source plot of trees become large enough to marcot. Clone No.3 has cropped regularly each year since it came into bearing. It is a strong upright grower forming a good size tree in its early years. Just the job.
Yes, of course, we have Kwai May Pink Clone No.B3, a good variety for the Tableland. But has selection ever been done in other Lychee varieties?
WHAT OF THE FUTURE?
The problem with a lot of the Rare Fruit is trying to sort out what are the best varieties or selections from a whole lot of not-so-good ones. Where to get them. Their short supply and the need to order well in advance to allow time for propagation.
In some cases they are difficult to vegetatively propagate as with grumichama for example. There is a selected tree on the Tableland with very nice-tasting fruit and a regular bearer. Cuttings don't work and neither does marcotting. It looks like it will have to be propagated by approach grafting its seedlings back onto the parent tree. A slow and laborious process.
Apart from Cashew Nuts and a few others, there is no official overall Rare Fruit Improvement Scheme properly funded and administered by committees, as there are for all other tree fruits in Australia. A lot of species are too small in number anyway. However, it must be pointed out that if a home gardener, hobby farmer or commercial grower invests lots of money in a Rare Fruit orchard, to say nothing of the time, labour and materials that are necessary to bring the trees into bearing, then they should be entitled to the very best trees available. But they don't always get them, do they?
Guess we will just have to carry on the way we've been going. Better varieties will eventually be imported, better clones and selected seedlings are being identified and propagated each year. We'll get there somehow but not in quite the planned and well-managed way as with the temperate fruit crops down south.
DATE: March 1995
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