Low genetic diversity of Geneva rootstocks and viruses

[MikeC]

That may be a good choice to at least try out. I need a few apples to fill in the gap between really early apples and the later ones that seem to be in late September / Oct ripening slot. At least a variety that tastes good. Some varieties in the late Aug early Sept are very so-so. Nothing that is worth having a whole tree of. Alkmene may be a good one to give a try. TY!

[Levers101]

More evidence that G.935 is virus susceptible comes in the way of the Summer 2016 NYSHS Fruit Quarterly publication:

http://nyshs.org/wp-content/uploads/2016/10/Fuchs-Pages-25-27-NYFQ-Book-Summer-2016.pdf

[blueberrythrill]

Levers

You nailed it. Tree decline or death in commercial orchards who planted G935 rootstocks even after using virus free certified scions. This problem was known to exist on G16. The problem may be a good reason for me to reconsider pulling a bunch of my B9 trees and replacing them with G935.

Wonder if G11 and G41 suffer from the same latent virus problem?

[Levers101]

I found the MASTER-table for Geneva rootstocks (with their 4-digit CG trial code), that gives their parentage and original size classification. http://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS.2003.87.1.26

G.11 is M26 x Robusta 5
G.41 is M27 x Robusta 5

Not sure if Robust 5 is virus susceptible, but I doubt that M26 and M27, being older cultivars will die from viruses.

[blueberrythrill]

Thank you for the publication. I had not seen a discussion on the various FB strains before. I did not see any mention in the article if any of the strains used in the research article were resistant to Streptomycin.

Looks like virus problems are going to be big on G935 perhaps like G41. I learned from the article below that its very difficult to determine if the scion wood is really virus free using the common test. A more expensive test produces more accurate virus results, but I how many nursery are going to spend big bucks for the more expensive test?

Don't think I would be grafting anything to G935 until the virus problems are better understood

http://treefruit.wsu.edu/news/virus-sensitivity-in-g-935/

[scottfsmith]

From the WSU link:

More sensitive are G.16, which succumbs quickly to nearly any virus

Been there done that! I agree that G16 is the worst of the 2-digit G stocks. G30 I only had problems with union breaks, no decline issues.

[SuperG]

Looks like virus problems are going to be big on G935 perhaps like G41.

Maybe I'm reading this wrong or missed it in the article, but I thought G.41 was one of the few that HASN'T shown issues yet. Am I mistaken on that?

[blueberrythrill]

Superg

Thank you for catching that! You are exactly right. No problem with latent viruses on G41.

I intended to say G16 not G41. The Geneva chart shows problems exist on G16, G814 and G935

I planted a bunch of trees on G41 this year and they are growing like crazy.

[applenut]

Most of all the others I have are on M111. It is an OK rootstock but there are several issues with it. I HATE suckering at the rootstock and the M111 seems to be bad at that. I am getting too old to be bending down cutting those off month after month with some pruning shears.

Mike; sounds like you have M7, not M111. M111 suffers from aerial burr knots if the graft union is too far out of the ground, but hardly ever suckers. M7 on the other hand suckers heavily every year, and yes, I hate that.

M111 has been productive for us in a wide range of climates.

[MikeC]

I agree the M7 is worse at suckering. It seems the last few years the small trees on my M111 each has suckered. Not as many suckers as the M7 would get- those are absolutely THE worst at suckering. Maybe it was a fluke. I also agree about the burr knot issue with the M111. I have had some burr knots that are higher up the rootstock than what I imagined. I did take more dirt and put around the rootstock to cover it. I will double check those trees that I think has the M111 rootstocks. Perhaps they are M7 as you mentioned. Thanks for tip.
I appreciate your nice reply. Very good information. Nice looking apples in the picture.

[Levers101]

Not really thinking about this, I went ahead and stuck scions on my Liberty/G.935 tree Monday. Grr! Kicking myself for doing that now. Don't know if I can still pull them and move them elsewhere or not, but am considering it. Not sure if these viruses just need contact from pruning or scion contact (flu for trees) or need very intimate cellular callous and cambial growth to move (mononucleosis for trees).

[mamuang]

Lever,
Last year I grafted a Harrow Delight pear scion (confused it with Harrow Diamond peach) on a peach. Two weeks later when the graft leafed out, I realized it was a pear. I cut it off of the peach branch and grafted on a pear. Guess what, it took.

I bet that your newly grafted apple scion will survive and work fine on a new rootstock.

[blueberrythrill]

I love the way the grower used the water bottles for branch weights and I noticed that every branch with the weight has a huge bunch of apples.

Is that a MM111 tree in the picture?

[applenut]

Yes, the variety is Dorsett Golden and the rootstock is EMLA 111; the tree was planted as a benchgraft in 2014.

We're looking at increasing the planting density in this dry-farmed area. Later-ripening varieties are blossoming now, some will wait to about 5 years to start bearing.

[blueberrythrill]

Very impressive yield on a 3 year old bench graft. Does the area get a lot of rain? Does the grower use some type of animal manure for fertilizer?

[applenut]

Kampala gets about 50 inches of rain a year, April is the wettest month. The soil is very fertile, but they do add manure around the tree occasionally.

[VSOP]

For your interested, here is a link to a study performed to determine the graft strength of various Geneva rootstocks with different scions.

http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=6102&context=etd

(As an interesting aside, I found out that different scions also contribute to graft strength, with some being weaker and others stronger. Stands to reason, but I had not thought of that before.)