Grafting

I list the reasons for grafting.

1 To propagate, or to assist in propagating, plant varieties not otherwise conveniently propagated.

2 To substitute one part of a plant for another.

3 To join plants each selected for special properties, eg disease resistance or adaptability to special condittions of soil and climate.

4 To repair damage, to overcome stock/sion incompatability, to invigorate weakly plants.

5 To enable one root system to support more than a single variety or one branch system to derive from more than one root system.

6 To elucidate problems of structure, growth, and disease.

7 To bring forward sion maturity by grafting to a more vigourous understock.


TO BE CONTINUED

Questions, playing the Devil's advocate, I have in response to these reasons are (the numbers match with the points made above):

1. Why should we propagate those not otherwise conveniently propagated. To me it almost seems like perpetuating the problem.

2. I don't quite get this one.

3. Hmmm... maybe... on the other hand we spend a lot of time telling people here that they shold take the time to find out about all kinds of roses to find the ones that are better suited to their climate. It seems counter intuitive to then say I'm going to graft x onto y to allow people to grow it in places where it would otherwise do poorly.

4. This doesn't do anything to help the tip the balance I'm afraid. You wouldn't have scion/understock incompatibility if they weren't grafted.

5. Yeah... I've never looked at these bi-grafted roses. I would question how they would go long-term unless they were very evenly matched for vigour. I can see one becoming the more dominant one causing the plant to redirect resources away from the weaker one causing it to die off. Intersting concept about having more than one root system to support a single plant. I guess that's what ramblers do when they touch down and root where they come in contact with the soil.

6. I don't get this one either. Grafting them is often the cause of such problems in growth, structure, and disease. There has been some research to demonstrate that there is some cellular exchange of material between the understock and the scion which affects the disease resistance of the scion. You only have to look at how badly Dr Phooey mildews to wonder whether it is causing any such resistance problems in the scion.

7. This is a good reason especially for us breeders. To be able to speed thngs up so that more plants can be produced and evaluated in a shorter time is not something I had thought of before. This is a real good reason for me to add to my set of 'scales'.

Simon, take #7 off your scale for you need to know how well they grow on their own roots and what size they will reach in a given time.

Oh yeah... I'm not so much worried about that. I'm looking at further down the track once preliminary testing has been done. This would be around the year 3-4 mark I reckon. Not straight away.

GRAFTING CONTINUED. I'm back again with this never ending subject HO Hum, pardon me if I nodoff.

Viruses are transmitted from the buds (Sion) or from the understock resulting in an infected rose that is worthless. Heat treatment is unreliable to cure long term but just after treatment buds can be taken that supposed won't have the virus?
Best cure is to avoid all that and propagate using healthy virus free buds and understocks. A lot of the very old nurseries became infected when little was known about this problem. No doubt they are trying to get on top of the problem but a lot of infected plants are sold. The other problem is Mosaic Virus is very hard to identify and until a reliable test is available progress will be slow. The other problem is inexperienced operators grafting
infected plants and not having an eradication program in place.
I have virus free Multiflora I call mother plants at the back of this 5 acre property that supply all the understocks. No roses are anywhere near these plants. The cuttings from these are taken 300 yards away to be cut to length and callused. A month later when callused they are planted in the grafting area and budded when buds are available, ( Approx 3 months)
My main concern is bringing in infected budwood and infecting the baby Multiflora it is budded on. Some nurseries cut the top off these budded Multiflora and use them again for understock next year. No wonder Mosaic Virus has spread so quickly for the buds could be infected. I never use understocks that have been budded the second time. All these are discarded so if I keep my mother plants alive I will always have Virus free understocks. Even the secuteurs are seperate, one pair at the back of the property and another in the front. These mother plants are best up to 5 years so I propagate another lot of mother plants using cuttings from these.

I BELIEVE I HAVE IN PLACE A SYSTEM TO MAINTAIN VIRUS FREE UNDERSTOCKS. I BUY BUDS FROM A VERY RELIABLE NURSERY AND CAN DO NO MORE. I pride myself in growing healthy, disease free plants that are ideal for growing on as they are not growth checked by being potbound.


TO BE CONTINUED

Not all of this is exactly true Bruce...

Heat treatment is unreliable to cure long term but just after treatment buds can be taken that supposed won't have the virus?

It is extremely reliable and the people who pioneered the procedure have been able to show that the virus is killed and plants do no lapse again even a very long time down the track. I have been in discussions with Prof. Malcolm Manners, who is the above mentioned pioneer, and if people follow his protocol you can consider the rose cured pemanently. The data speaks for itself and anything else is pure speculation and unfounded. Seeing as we have no facilities here in Australia to carry out this procedure on a commerical scale we cannot easily repeat the results. Backyards can, however, attempt to erradicate the virus using some easily obtained materials and equipment.

Best cure is to avoid all that and propagate using healthy virus free buds and understocks

Ideally yes... this would be best. However, a lot of varieties are chronically infected. Varieties such as 'Peace' and 'Altissimo' are often mentioned as being chronically infected and almost every one seems to be. Altissimo for sure here in Australia. Best practise should then be to begin with erradicating the virus and then archiving the cured variety to make a bank of certified clean budwood.

A lot of the very old nurseries became infected when little was known about this problem.

A lot of nurseries are still being plagued by it whether they be young or new. The general opinion among lots of people is it is better to preserve an infected variety than risk losing it altogether. The history of RMV is quite interesting really. As it goes RMV was not a problem untill about the time Dr Huey was developed. Some intellectual giant decided that maybe prunus could be grafted onto rose understocks (i.e. Dr Huey) and when this failed the understocks were re-used and the rest is history. We would not be having this conversation now if;

1. Roses were never grafted
2. If some pee-brain with a little knowledge didn't try to graft a prunus infected with RMV onto a rose. The full name of RMV is Prunus Nectroric Ringspot Virus; PNRSV for short... there have since been found a number of other viruses that have similar effects. All can be cured with thermal therapy.
3. Dr Huey had not become the most wide-spread and generally accepted understock.
4. Grafting had not become the predominate method of large scale propagation (which also reflected the fashion of the day to select only for flower instead of what it is changing to today to select for other properties such as health and ease of propagation).

The other problem is Mosaic Virus is very hard to identify and until a reliable test is available progress will be slow.

This also is not true. There are many places where RMV can be tested for. The people in Florida have very sensitive ELISA tests that require only a single leaf to be sent to them. There is a lot of guff about returning false negatives during very hot weather, however, Malcolm has told me directly that they test all year round and can detect even the smallest amount of virus. We have many places here in Australia that can do the test. Last time I enquired the test cos about $80 per variety and took only a short time. Identifying the virus by visual means IS difficult due to climatic factors and that not every varoety is affected in the same way but identifying by lab methods are extremely sensitive. At one stage they were trying to erradicate the virus by tissue culture methods. however, they have discovered that even using minute tissue samples they still remained infected. Tissue culture is useful once the virus has been erradicated.

I would ask, Bruce, how you know for certain that your multiflora is virus-free? Did it start as a seedling? This is the ONLY way to guaranteee the understock does not have the virus because to date it has never been shown to be passed on by seed (which is unusual since it HAS been found in pollen... still... as I mentioned before the data speaks for itself and we are not talking about a year or two of data.. it's more like 30 years of data and research in this field). Have you had your multiflora virus tested and certified? Did it come with virus-free certification? All these are questions that are important because up there you there is a good chance that the virus could go unnoticed in some varieties. Some multiflora as very sensitive but the fact remains that unless you have lab certification to show that you understocks are virus free you are not able to make that claim based on visual inspection alone.

Bringing infected budwood onto a property is not really a problem if you have good cultural methods. The myths are;

* RMV can spread form plant to plant. This is false. The ONLY case of transmission documented was by root grafting when plants were planted too closely together.

* Tools such as secateurs can pass it on. This is false. People have tried to force machanical transmission and have never been able to achieve it. The data supports this.

* You can't use infected plants to breed from. Again, this is falso. There has never been a documented case of transmission via pollen despite it being detected in pollen.

I believe your system is rigorous and well thought out, Bruce, and you are to be complimented for putting it in place when so many others do not. I would feel more confident purchasing roses from you because of it than I would any other supplier. I do,however, think it is important to not make too many generalissations because RMV is one of those things that have been extremely well researched and the facts are very well known. Others will have you believe all kinds of rubbish that just isn't true. Speaking with the researchers themselves, however, is the best advice I can give. If you like I can invite Malcolm to come along and have a chat to people here. He is a wonderful helpful man and I am sure he would be more than happy to help dispell the myths if what I say isn't enough to convince anyone.

Given these issues, I'm still not sold on the grafting issue. I will, however, add a fourth reason to my list of why you would ever graft... and that's to cure RMV via thermal therapy.

The Multiflora was gifted to me by a grower who had a closed nursery as far as material coming in was concerned.
He was set up to do Iceberg on 30" Multiflora and had never seen Mosaic Virus on any of his plants over years of propagation. The budwood was taken from old Iceberg plants within the nursery. I can do no more than use this understock to stay in front of the problem as I don't have much time left due to my age.

We have talked about building a heat treatment box for treating valuable plants that could be lost if not treated. I lost interest in building the equipment when I read an article by another Boffin that heat treatment was not complete and the virus returned.
Think these two should sort this one out for me.

Regards Secateurs passing on viruses. There is a very technical grower in my district that practices almost operating theatre procedures. He grafted some Navel oranges for me onto his rootstock and charged me extra to sterilise his equipment and did the budding out on the footpath. He had a friend in Qld that lost his nursery due to Virus. Having 2 pair of cutters is more convence rather than disease control. I have noted less bud die off when sterilising my grafting board and tools regularly.
Yes!! would very much like to have contact with Malcolm. Pity the other Boffin wasn't available to join the party.

Regarding bringing RMV budwood onto the place means I am selling or giving away a plant that could be infected. My principles would not allow me to knowingly do this. The rootstock system I have in place will
ensure it doesn't infect the mother rootstock for if it got in there I might as well go fishing and hunting for 5 years until the Multiflora seeds grow into useable plants. Changing to seed grown plants can be started anytime the seeds are available in quantity but due to age I don't have the time.

I'll send you some advanced multiflora seedlings Bruce I have a few real goers that are two years old now.

I know of the other boffin but to say any more here would be inappropriate.

I'll contact Malcolm and see if he'd like a temporary membership to come along and host a guest question time on the forum chat window.

It's really important not to generalise RMV with the actions and behaviours of other viruses. If other orchardists have experienced great losses due to a virus, that doesn't mean the same will occur when we are talking about RMV and roses. Others have tried and failed to transmit the PNRSV virus using mechanical sheers and other such implements so it would be reasonable to think the chances of infection occuring through pruning sheers is slim. Of course you will always come across people who think they know better, and good for them... if they can show me the virus is PNRSV and not some other virus, or that the virus they think they've found and transmitted actually is PNRSV, then that would be a different story. There may be other pathogens, however, for which this is not true and clean secateurs is a good way to avoid such problems. I routinely sterilise mine as well because whilst it has never been documented to have happened I don't want to be the one that proves it wrong by infecting my own plants. So many other factors such as climate or local strains of RMV need to be taken into account before you can reliably say the 'never' word.

I love how our conversations evolve... it's very important to discuss these things in such a manner