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Post by Tom Wagner on Aug 17, 2009 21:46:57 GMT -8
The varieties I use for Late Blight resistance are being introgressed into many, many types of tomatoes. Sometimes in a backcross, but most of the time I am diluting the presence of resistance by multiple generations of out crossing to the point that I don't know what I have. I was reminded that I had this picture posted on some kind of link to Facebook or something like that. photos-g.ak.fbcdn.net/photos-ak-sf2p/v282/67/82/1329755999/n1329755999_1669838_9799.jpgThe hybrid pictured here in 2007 was always like its half sibs...excellent LB resistance during the most rapid infestation period. I am hoping the races of blight have not found away around this resistance for this year. I expect to see blight coming in soon. The crosses and OP's for ph-2 and ph-3 are in several locations, therefore, I hope to have all my seed extractions done before any outbreak. I will be sowing some seed of my best LB resistant clones very soon to have plants growing before I leave for Europe. I hope to have someone take digital pictures of them while I am gone for two months and send them to me. These photographs will be used in real time for the workshops in Europe. |
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Post by robertb on Aug 18, 2009 10:46:26 GMT -8
Have you any idea how many genes are involved in blight resistance? In view of what you say, I can't help suspecting the answer's going to be 'several'.
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Post by Tom Wagner on Aug 18, 2009 14:45:24 GMT -8
I have found this a hard subject to make simple. But here goes...
Tomato late blight resistance genes are non-allelic
The gene, Ph-3, Chromosome 9
Ph-1 (chromosome 7
Ph-2 (chromosome 10).
Reports are that (Ph-1)
and that WV700 possessed one or more dominant resistance genes (but is associated with Ph-2)
The meaning of (genes interact in an epistatic manner )
epistatic (not comparable)
1. (genetics) Of or pertaining to epistasis, the interaction between genes.
I have a lot of self doubt about my work with Late Blight resistance. Since I had great results with sinlgle dominance with WV 700 with my particular strain of it for years 2004-2007. But 2008 is a year that needed homozygous Ph-2 and Ph-3 clones. Mountain Magic has heterozygous genes as a hybrid and it did not survive to the end of the infestation process. Only my most homozygous clone (Ph-2 and Ph-3)survived totally. I will be testing some seedlings from the recent hybrid of WV 700 X homozygous Ph-1 and 2 for this fall. The hybrid would be homozygous for Ph-2 but only heterozygous for Ph-1.
The good news is that I am transferring the genes Ph-2 and Ph-2 into a wide variety of clones such as Black Pineapple, Black Prince, Green Sleeves, WV 700, and many, many more. I've got to remind myself to sow a huge compilation of varieties soon.
The kind of work I am doing with require that I do a large extension collaboration. I will be exploring ideas to that effect soon.
Tom Wagner
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atash
Junior Member
Learning from my mistakes since 1964
Posts: 96
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Post by atash on Aug 18, 2009 22:45:55 GMT -8
If your resistant tomato survives past a few days into the autumn rains, when the rest of my tomatoes all collapse and die suddenly, I'll take its picture and it should be a striking one, with one live plant among a lot of dead ones. Too bad it's on the corner, but I could easily adjust the angle of the shot.
I don't usually get frost before December, but every year every plant I've ever had is dead within a few days of the start of the rain. So, it will be an excellent if challenging test.
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Post by Tom Wagner on Aug 18, 2009 23:10:36 GMT -8
I will have to take you up on that. I will give you Tim Pitts' phone number so you can come by and look at #65 in the garden right out front by the yellow house. The vine is healthy right now and I am picking fruit from it, but if the blight doesn't hit before Sept 9, I'd like to to look at it between that date and Oct 27.
I will put a yellow ribbon on the top of the plant with the number 65 on it. This will be my standard for any blight resistance.
I will do the same marking for #65 in the Skagit River location, Vancouver, WA, etc.
Thanks in advance, Atash
Tom Wagner
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Post by robertb on Aug 19, 2009 4:51:32 GMT -8
I didn't do anything about epistasis in the botany course I rely on for my knowledge of genetics, from about thirty years ago. I think I need to update myself! My current understanding of genetics is much influenced by an interest in bee breeding, and with haploid males, it's unlike anything else.
From what I can make out, for blight resistance, you need two genes which interact, and at least one of them needs to be homozygous. That's a start.
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Post by Tom Wagner on Aug 31, 2009 23:08:41 GMT -8
Today was one of those days when I emphasized the Late Blight resistance hybrids that I made around in late June and early July. Over and over, I had potato berries which begged me to extract the seed before it was too late. Many of those crosses carry resistance from both parents and these seed lines should give me odds of 75% of the progenies providing some LB resistance. One third of that group will be homozygous for a least one allele pair. I am glad I performed a lot of LB breeding years ago in order to make crosses in which the inbreeding depression will not be great between distantly related lines.
The tomato Skykomish is my best homozygous Ph-2 and -3 version that combines great flavor, super agronomic characteristics and wonderful bi color hues. I extracted so many crosses of Skykomish today in which it was a pollen parent that I lost track of how many I did.
Why Skykomish? Simple, the river by that named deposited Sultan alluvial deposits in the Tualco area where the Skykomish grew last year and this.
Tom Wagner
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tz
Junior Member
Posts: 73
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Post by tz on Sept 11, 2009 3:02:28 GMT -8
How easy is it to transfer LB resistance in crosses? Is it presence/absence in the F1s or dilution in heterozygotes (or other)? I ask because I have an unknown tomato (looks to be something like Indian Stripe x Omar's Lebanese -from a pack of Omar's seed). It is 1-2lb pink-black fruit with persistent stripes but the flavor is poor and texture is mealy so I want to cross it (probably to Brandywine x Black Krim F1 or F2) next year. The three plants I am growing are untouched by LB.
This is the first year LB has been a major problem for me so I don't know if it would even be possible to see if resistance was transfered in a cross if the LB doesn't show up again.
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Post by kctomato on Sept 26, 2009 9:35:46 GMT -8
Reference to a slide presentation at the Tomato Breeder's Round Table from Dina St Clair of UC Davis. QTLs that are a novel source of resistance to P. infestans in tomato and are NOT associated with Ph-1, Ph-2 or Ph-3 genes tgc.ifas.ufl.edu/2009/StClair%20UC%20Davis%20Update.pdfOther points Tomato QTLs lb4, lb5b, lb11b : – All 3 coincide with potato LB resistance QTLs – Lb5 and lb11 coincide with several horticultural traits (linkage drag) |
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