Pecan


#301

He must know something I don’t, however…

If he heats up his rootstocks for at least two weeks and then grafts and then keeps the temps fairly high (70-75F) then I see no reason that shouldn’t work.

I wait until bud swell. It’s that simple. Same with my buddy who’s been grafting pecans for more than thirty years. My buddy uses his homemade grafting tool with a V type cut and he’s gotten better than 90% results after being planted in the field and followed up on the second year.

Dax


#302

His trees are field grafted, which is standard operating procedure for the big pecan bare root farms around here. I may be wrong but I’m under the impression people like you and your buddy like to maximize results, and I like to also.

Also, he has thousands, if not tens of thousands, of trees to graft so it’s mainly a time constraint thing.


#303

Correct.

Dax


#304

Just a raw estimate, but what I saw yesterday was at least 150,000 trees hilled up and ready to sell plus another 100,000 still in the rows waiting to be harvested. I have no idea how many other fields he has growing, he would need at least 40 acres per year with a 3 or 4 year cycle.

The difficult with field grafting is that 70% take rate. That leaves 30% of the trees ungrafted. it is common to ring bud which can give another 20% but ring budded trees don’t grow off as fast as dormant season grafts. In other words, they are sellable, but usually with a different price than the whip and tongue grafts.


#305

Yep, just got back. He had mountains of pecan trees heeled in. I think 70% is pretty darn good these field grafted whip and tongues are not always pretty. The Elliot rootstock I got from him are beasts, they are the smallest size he has.


#306

Great! Hopefully you and I will get some (heavy) caliper persimmon seedlings from MO.'s state nursery, as-well. I would be happy to get the largest seedling as possible for anything I graft at any time. That gives you so many more options for technique. I hope to do mostly bark and 3-flap grafts on my MO. pecan seedlings and walnut seedlings.

Did either of you take any photos while you were there? What’s the name of the nursery? I went back up this thread and didn’t see a mention. @Fusion_power

Dax


#307

Sorry, I forgot to take photos. I was so focused on bagging everything I didn’t think to. It’s Shiloh Pecan Farm in Ray City, GA (no website). This video from DWN pretty much sums up what I saw https://www.youtube.com/watch?v=LLYI6MVJqsg ( DWN is a heavily roided version).


#308

That harvester is incredible.

Thanks for that video, David.

Dax


#309

Hey Dax, I happened upon a triple kernel pecan in Dr. Lenny Wells blog. He’s an awesome guy BTW.
Scroll down a little
https://blog.extension.uga.edu/pecan/2017/11/odd-pecans/


#310

Thanks, David. I’ve seen an abnormality one other time. I’m pretty sure it’s what that professor called a twin-pecan.

A triple kernel… that’s quite interesting. If it cracks well and the meat separates easily w/o much fill between the kernels, that would be okay to have in my book. Such as what Darrel describes with ‘Hall’.

Appreciate the link.

Dax


#311

Dax,

I ordered 20 persimmon seedlings from MO Forestry Dept about 7 years ago and I called the lady and requested larger seedlings for grafting. They sent me mostly larger seedlings like I requested. You may call them and request for larger seedlings.

Tony


#312

They know me well.

Dax


#313

I’ve been digging around for research on growing pecan in subtropical regions. This study in Turkey is incredibly enlightening if you put in the time to study the results.

With 500 hours below 40F, Western shows protogyny with 18 days between female and male flowers. With 300 hours, it still shows protogyny, but there are only 3 days between. This part is not in the article, but take Western down to 200 chilling hours and male/female flowers overlap fully with male flowers shedding pollen before female flowers! This is clear proof that male and female pecan flowers are chilling hour sensitive and that number of hours below 40F determines when flowers will open with different time requirements for male and female flowers! The most important concept is that bloom timing is not a sudden fall off the edge of the world event. It is a gradual process. Another thing shown is that different chill hours shift bloom time in one direction for male flowers and in the other direction for female flowers. I need to study this a bit more to derive the function to express this mathematically.


#314

The whole idea of “subtropical” east of the U.S. Rockies or north of Egypt is suspect for those of us in southern California, south Africa, and Austral-Asia from Perth on north. For evidence … look at the success of @applenut.

Our Fall, Winter, and Spring are different. Zone 9a in Riverside county CA does not translate to zone 9a in Turkey. I like the spreadsheet you are developing about Pecans but so far it does not account for the behavior of Pecans in the locations listed above.

Maybe we teach from the same textbook.


#315

My son and I transplanted 10 of the Avalon trees today. The root systems ranged from excellent to a few that were poor. I’ll monitor them closely this year and water as needed to help them get established. I checked the roots very carefully before setting them out. There were no signs of nematode damage. The trees will require some work to get growing straight up. I will put stakes beside them in a week or so.


#316

Out of my 10 Avalon trees, 4 of them had excellent root systems, 2 poor and the other 4 were mediocre. I put all 10 of my trees in 7 gallon RootTrapper knock off pots. I’m debating on whether I should plant the 4 really good ones. I’ve had such excellent results with these fabric pots, I can almost guarantee several feet of growth. On the other hand, my bare root trees directly field planted always go through major transplant shock with minimal to no growth that first year (if not demise).

Plus, I’m not sure where I can fit these 10 trees just yet. I’ve already planted 12 pecan trees this year. My orchard/collection keeps growing! I may need to invest in a 4th chainsaw. It seems I never have enough space.


#317

Editing this post to combine some other things I’ve been working on regarding the ARS-Grin database on pecan and the previously posted info about pecan dichogamy.

Alternate Bearing search for “pecan alternate bearing conner worley” for relevant articles

I’m working through the logistics of alternate bearing as it affects pecan. There are several published articles where Alternate Bearing Index (ABI) was studied over the last 100 years. Here is a short summary.

  1. Pecan matures from mid July to late November. There is no correlation between date of ripening and ABI.

  2. Pecan varies in size of crop with age. ABI does not correlate directly with age of tree.

  3. Pecan varies in size of crop load with some trees producing far more nuts than others in a given year for a given tree size. ABI correlates inversely with crop load, i.e. more load in one year is associated with less production the next.

  4. Artificially reducing the crop load by shaking water stage nuts off heavily loaded trees will reduce the ABI.

  5. Pistillate flower initials are formed in the year prior to nut production and generally are formed 2 to 3 weeks before the current year nuts mature.

  6. There are two theories why pecan alternate bears: the carbohydrate theory and the Phytohormone theory. Neither theory fully explains observations therefore neither theory in current form is valid.

  7. The closest correlation I could find is that something happening in the tree during formation of pistillate flower initials determines production in the following year.

  8. Heavy crop load is directly associated with freeze damage and winter mortality with some cultivars severely affected.

This is my theory. Pistillate flower formation appears to be directly associated with phytonutrient availability at the time the flowering buds are formed. This suggests that breeding for more leaf canopy as a ratio to current season nut production should directly affect ABI in pecan. There is also a photoassimilation index for leaves that indicates how efficient leaves are at a given point in their lifetime. Leaves start small and newly formed, develop to full mature size at which point their photoassimilation potential is maximal, then become senescent with corresponding reduction in potential until the leaf dies and falls from the tree. Photoassimilation index is highly dependent on tree nutrition, water availability, and leaf health! Breeding for longer duration of maximum photoassimilation potential will also be correlated with reduced ABI. Finally, the plant hormone element has to be accounted for. I propose that there is a feedback mechanism in pecan where forming nuts produce hormones that tell the plant to divert photosynthate into the developing nuts. The more maturing nuts on the tree, the higher the levels of hormone produced and the greater the diversion of photosynthate. Pistillate flower initials are sensitive to low photosynthate levels and do not form where absorption by nuts exceeds production potential of the leaf canopy.

tldr; To breed pecans with consistent yearly production, we have to increase leaf canopy, decrease nut load, and improve tree nutrition and health.

Dichogamy

Some pecan varieties have near 100% overlap of pollen production and pistillate flower receptivity and are capable of pollinating themselves. There is something unusual about the genetics of varieties that overlap. Let’s find out what.

Pecan dichogamy is determined by two alleles, ‘P’ = Protogynous and ‘p’ = Protandrous. Capital ‘P’ indicates that Protogynous is dominant and lower case ‘p’ indicates that Protandrous is recessive. You might attempt to do a standard Mendelian grid and expect native pecan to segregate with 1 - ‘PP’, 2 - ‘Pp’, and 1 - ‘pp’ which would be the norm with most genes. But this is not what happens with pecan. Because these alleles affect the bloom period and because they tend to force pistillate flowers to be pollinated by the opposite genotype, the result is that a Protandrous plant most of the time pollinates a Protogynous flower and vice versa. The result is that standard segregation patterns do not apply. In native stands of pecan, trees tend to segregate 50% protandrous and 50% protogynous. This means that about half of the time, native trees will have genotype ‘Pp’ and the other half ‘pp’.

But there are exceptions. One of the most notorious is Mahan which has genotype “PP”. All of Mahan’s progeny are Protogynous. What about trees that have genotype “pp”? Well, they have a quirk or two too. A plant with this genotype will always have pollen shed either prior to or concurrent with receptive female flowers. So what did I figure out that is unusual? Pecans that have near 100% overlap between pollen shed and flower receptivity are always genotype “pp”. There are no examples that I have found so far where a tree with ‘PP’ or ‘Pp’ genotype have strong overlap. Here are some examples: Barton, Cherokee, Creek, Jubilee, San Saba, and Western Schley. What makes this interesting? Most protandrous pecans do not overlap male and female flowers, therefore there must be a gene(s) that affects flowering type to cause them to overlap. I’m going to speculate that this will be a gene or biopath linked with chilling hour requirements.

Why so? A study of chilling hour requirements for pecan suggests that catkin buds have different chilling hour requirements to break dormancy than pistillate buds. I speculate that there is a gene(s) that sets both catkin and pistillate buds with the same chilling requirement so that they always break at the same time so long as chilling hour requirements are met. In other words, pollination type of pecan whether protandrous or protogynous is linked to the biopath for chilling hour requirements to break bud dormancy. The knock on effect is that there must be more than one ‘p’ allele but not necessarily more than one ‘P’ allele! Has anyone done work to determine if there are multiple alleles for dichogamy in pecan?

Database organization of ARS-Grin

The repository database has rudimentary data on each accession. Increasing value for research and breeding would suggest some of the following could be done.

  1. Add notes of origin, background, and genetics for each accession. This will consume several thousand hours of labor plus tie up a lot of resources doing DNA work. Consider breaking this down into smaller tasks that can each be accomplished in 1000 hours or less. Automation can do quite a bit of the work if the background data is available.

  2. Addition of new accessions has to be considered as part of long term database maintenance. A huge component of this should center on sampling to capture more geographic diversity. There are also quite a few grower selections that could be considered for addition to the repository. Source would be better if a geographic lat/lon reference were used instead of a general “U.S. or Mexico” label. For example, Mexico, Jalisco, 19.527193, -104.150108 would describe an accession geographic origin in Mexico Jalisco state.

  3. I don’t know enough about the breeding program so this is a general comment. Reshuffling the genes in existing varieties can only achieve a certain amount of improvement. At some point, additional material will be needed both from the central range of pecan and from the farthest extended boundaries of natives. There is a strong inference that other hickory species can contribute significantly to this. The most likely species to have high value are C. Cordiformis, C. Ovata, and C. Myristiciformis. Genetics for disease and pest resistance and for soil and climate conditions would be targets.

  4. I am not aware of a program to develop targeted breeding, but given the effort to sequence the genome, the next step is to leverage knowledge gained to make synergistic crosses. A program with clearly identified objectives should be developed. This is an area the genome team can contribute significant expertise into developing. An early objective should be to elucidate allele function so that fewer seedlings have to be grown out and evaluated. Much of the cost of a targeted breeding program can be recovered by reducing effort required in grow-outs.

  5. One viable objective is to extend the range where pecan is cultivated both north and south. There are several commercial orchards in zone 6a and strong potential to develop orchards in zone 5. Very few cultivars have been selected for southern climates zones 10, 11, and 12. There is potential for pecan in Puerto Rico for example.

  6. Genetic modification has to be considered. There is huge potential to increase value of existing cultivars for example by developing a cassette of disease resistance genes that could be inserted into the genome of a cultivar such as Schley.

  7. Regional adaptation is an area that could be in the database, especially for development of improved rootstocks. Salt tolerance, PH adaptation, nematode resistance, and ability to absorb nutrients efficiently from diverse soil types are examples of some types of data that would be useful.

Putting the above together, the current static database is not going to work. There is a need to develop a transaction overlay where each fixed element is an entry in the database and a transaction is used to move that element for example into a breeding pool for crosses. This is a database concept that will require some time and effort by someone who understands data organization. Just having the data is one thing. Getting use out of the data is a different animal.


#318

This may be useful to some of you, Ellis Bros in Vienna sells Elliot (open pollinated) in the shell. I’m planning to pick up some for direct planting. Hey Fusion, I’ve read 6-8 weeks stratification is sufficient. Would you agree with that?


#319

BM,
I’ve gotten pretty much 100% germination on unstratified pecan nuts… just held in an unheated room (or, some years, just at room temp in my house!), and soaked for 4 days or so prior to planting.


#320

Nice, thanks Lucky!