Planning a new Orchard in North West Kent - Apples

[FB.]

There is also an interesting contradiction in the Diversity article. Alkmene, the offspring of two disease-prone parents, one of which is the widely-planted Cox, is nevertheless quite disease free.

Here's what I think is going on, with the likes of Alkmene or Bountiful (Cox x Lane's - both mildew-prone).

Cox has minor resistance gene "A" from its mother and "B" from ist father.
Dr.Oldenburg has minor resistance gene "C" from its mother and "D" from its father.

Think of them as antifungal chemicals which flow in the sap.

Over many years, the fungi have evolved to defeat the AB combination in Cox, or the CD combination in Dr.Oldenburg.
But their offspring will be AC, AD, BC or BD; they are combinations of the two.
Let's call Alkmene AC (A from Cox, C from Dr.Oldenburg)
The AB-specific diseases of Cox are defeated by the presence of C in the offspring from the other parent.
Similarly, the CD-specific diseases of Dr.Oldenburg are defeated by the A inherited from Cox.

However, since the ofspring still share one gene in common with their parents, the fungi are already halfway there to breaking through the resistance. This is a random chance event, modified by some varieties being lucky enough to carry a few additional resistance genes.

It is easier for Cox's AB-specific diseases to get past the single defeating gene of "C" in an "AC" offspring, than to get past the genes "E, F & G" in an old triploid (let's say Boskoop).

To defeat Alkmene, only one mutation is required from the existing Cox disease strains. But to defeat Boskoop (an unrelated variety to Cox) would require three fungal mutations all at once.

So Boskoop's resistance would turn out to be more durable in an orchard of Cox and Cox offspring.
This, of course, would be slightly modified by some offspring being lucky and recieving a few more resistance genes than others (there will, almost certainly, be more than a couple of minor resistance genes in Cox, even if they've been defeated, so my example above is greatly simplified); therefore a bit of variation in the susceptibility of the offspring of Cox.

[yummersetter]

This is relevant to the initial posting as well as my situation - how long would you expect the variety specific attacking organisms to linger without a host? And are we talking above ground or the total environment? Would his Bramleys be more vulnerable than if planted in an area that hadn't come across them before? Or would there be 'antibody' organisms that will protect them more in the earlier planting place?
My village is in the heart of an area renowned for apple growing for centuries, both for cider and more recently, for commercial dessert apples, the same, I'm sure, could be said of Kent. I specifically (sentimentally) chose a high proportion of local historic 'brands' when replanting, as many will in these days of Heritage Orchards. It takes me a long time to get a new planting going - I expect replant resistance comes into play, but once its been 'accepted' most of them are fairly healthy in the long term, if the weather permits. I bought my replacement trees from the same nursery my great grandfather did so effectively they're exactly the same varieties. The fact that so far they're doing fine makes me think that there is something there beyond suitable soil and climate.
Within five miles of here there were acres of Cox orchards until some EC grant led to them being grubbed out a decade or so back, yet a lot of my healthier trees are of the Cox family. I was looking yesterday at the Kidds Orange Red and realised that I take it for granted that there will be a good, troublefree crop. There are some mis-shapen ones but looking over a hundred or so apples barely one had any disease or insect damage.
I guess this is the luxury of being in an area that suits the crop - I perceive the battle between health and disease as being evenly balanced - that for every insect that will make holes in the leaves there's another that will pollinate the blossom, get rid of one and you're likely to lose the other.

[FB.]

I would guess that scion-adapted diseases, such as canker, scab and mildew, would disappear within a couple of seasons after all trees of that type were removed (let's use Bramley as an example, for simplicity).
The problem, though, is Bramley trees many miles away could still be harbouring those Bramley-specific diseases, and scattering spores on the wind when it rains.

Soil-borne diseases, such as phytophthora, would probably take much longer, as they might continue to feed on dead roots left behind in the soil after the trees were removed.

But if (say) M116 replaces an MM106, the new tree will probably grow well (that's what I've found, even after planting M116's straight into the same hole the same day as a crown-rot-killed MM106 was dug out).
Eventually, the soil-borne diseases would adapt to attack the M116, but by then the trees will be big enough, strong enough and the roots with thick enough "bark" to help resist attack or outgrow attack by these fungi. It is young trees of the same rootstock as is already planted which are most vulnerable as they just can't get established if well-adapted strains of pests or diseases are killing their roots.

If you already have an established orchard on (say) M25, the whole soil area could be contaminatd with M25-attacking fungi, making it difficult for weak young M25's to get going. Basically, planting a whole orchard on the same rootstock is as bad as a monoculture orchard where all trees are the same type.
For that reason, I tend to try to alternate my trees: MM111....M25.....MM111.....M25.

So plant M116 to replace MM106. Plant MM111 to replace M25.

[Feral007]

All very interesting reading.

I don't know if I mentioned this before but there has been talk among the apple growing folk to the west of us, that any fruit trees that are not being sprayed within an inch of their lives should be removed so that the mono-variety apple orchards don't have any bugs/spores coming to them.

I can't help thinking that trying to keep them safe while they grow only one type of apples is doing harm to the gene pools around. There are apple trees around here planted as street trees. They are so healthy and such old trees. They aren't pulling them out yet, but I'd hate to see that mentality catch on.

[Loudbarker1]

Thanks agian to all for thoughts and advice. I have been offline for a fortnight, so please forgive the late thanks.

I will digest the suggestions and the thread and post (probably) revised list in due course, and then we can go thrugh the same exercise with plums, pears, apricots and cherries!

LB