Breeding New Fruit Tree Landraces

General Fruit Growing
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Sage hobilus

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For many species of fruit trees, that trick does nothing to speed things along. And even when it does help, it doesn’t do so evenly. You’d likely be selecting for what you might call “seedling-grafting precocity” (I have no idea if there’s a term for that?), which may eliminate many other linked traits you’ll want to keep in the population.

For avocados, maturity usually takes at least 4 years from seed, and occasionally 10+ years, and you can’t really judge the fruit for a few years after it starts bearing. I’d say 8 years per generation would be a safe estimate, though you could push it a little lower if one of the traits you’re selecting for is just normal seedling precocity.

Even for other types of fruit trees that bear sooner, it seems very, very ambitious to hope to get to any level of trait stabilization within a lifetime, assuming you start with a diverse population.

What other traits besides precocity would you be attempting to stabilize? Fruit size, color, acidity, flavor, flowering time, brix, cold tolerance, heat tolerance, drought tolerance, disease tolerance, unique soil parameters, resistance to pest pressure, high (or low) vigor, self-pollination, growth habit, etc.?

In a true landrace, those things all vary a bit, but have usually been narrowed over time by local climate patterns, community expectations, or farming practices. If you’re trying to reach even a much lesser level of stabilization with most of those at an accelerated pace, the logistical challenge would be daunting when it comes to tracking trees and their traits and deciding what to cull and what to favor.

I have a database of just a few hundred avocado trees grown over the last 3 years. I struggle to keep things updated often enough to be useful. And I’m currently selecting for only a single trait! Well, I guess there are many different traits that may impact being tolerant of local winters, but so far the only thing that seems to be a problem is long duration hard freeze tolerance for the above-ground parts of the tree.

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Oh, damn, that really puts a spanner in the speedy plan, I didn’t realise the grafting only works speedily with grafts from adult plants! Do you know which Prunus species this would be speedy for and which it would not? And, in general for this principle, do you have direct experience with that or have heard reports from those who do? I assume so but asking just to be sure. Since I had heard that the flowering mechanisms are triggered from the… sorry I don’t know the right term but I’ll say the ‘mother plant’. For example, so far as I understand, short day tomato species will flower under long day conditions when grafted onto neutral day plants. Not sure if that’s just for mentor grafts or if grafting an entire plant onto a root stock. But that also makes me wonder, perhaps with those species you are referring to, it might not work with a full graft but might with a mentor graft? Although, a mentor graft might have other implications, since mentor grafts can bring cytoplasmic elements into the graft, so that may reduce cytoplasmic elements’ diversity, though, that might not necessarily be an issue.

Or rather than a full mentor graft (in which basically keep only the end 2 or so leaves on the grafted branch, removing all the rest as time continues, to maximise the mother (‘mentor’) influence), I wonder flowering might be accelerated even if just grafting onto a branch of a well established tree. Similar principle but just less strict, not bothering to remove leaves. Which would be easier. If anyone has tried either variations I’d be interested to hear if the results were similarly speedy to grafting an adult branch.

If it were me, I would not bother trying to stabilise size, colour etc. nor even flavour, just eliminate ones that were not useful, not tasty enough. And eliminate those that were not healthy enough for whatever reason. And yeah I guess if some had really annoying growth habit, remove those too.

Yeah so trying to be as speedy as possible to deliciousness and survivability so that it’s a workable useful population, but as you say, over a greater length of time, perhaps intergenerationally, the traits could narrow further as you say, if so desired. And that’s the beauty, continued adaptation, and the possibility for continued selection for phenotypes if desired. That can be so nice. Like take most crops … let’s say annual crops. People might keep growing an heirloom for 60 years. By the end, they have basically the identical crop as they started with. They might even have inherited it from their grandma, and pass it down to their own grandkids. But with an adaptive, your crop will be way better suited in the end than it was in the beginning, and over those 5 generations, all that growing from those family members has produced something potentially quite different than what they started with. I really like that.

In terms of tracking, the easiest way would be to track nothing. Just cull all that are too unacceptable, let nature cross them (particularly easy if an SI population), and keep planting more. Either on ones own land if one has the space, or distributed in the local community, getting other people involved in the passion of the project. Also if my grafting idea would work (whether that be due to mentor grafts or if the species were suitable or whatever), that would speed things but yes, require note taking and hand pollination, or even done without hand pollination but just faster culling of the insufficiently tasting trees, but you wouldn’t have to keep track further than knowing which graft was taken from which tree you have growing in the ground.

Like right now I am keeping track of all the crosses I’m making, all seeds kept very carefully. But this is because I’m focused on speed and efficiency. But people like Joseph Lofthouse don’t do that, they just remove the plants they dislike, and the rest, process the seeds altogether in one big mix. And that does work fine. He has great results. And it’s way less work! I’m just using a tighter method for the initial period for greater efficiency at creating a maximised hybrid swarm rapidly, as well as speeding up the creation of an (or hopefully 2) SI populations. So, there are options there on where one wants to choose on the spectrum of note taking and making specific crosses or not, vs. how urgent the speed of things is. In my opinion, note taking and keeping track of everything would pay off the most just for the initial 2 rounds of crossing for making the initial diversity. And not even in terms of tracking traits etc., just in terms of making sure one crosses everything with everything else, so you make the most diversity you can from the seeds you plant, whereas if you just let nature do the crossing, you might be planting 10 seeds that are all the same cross, and leaving out many others entirely. I’d say that’s fine once the project has been going for a while, but it’s at that initial point that you, or should I say I, would want to give the best chance of the genetics of all the individuals I have decided to start with, getting into the mix. And 2 rounds of crossing would be like shuffling the deck of cards. Once shuffled, deal them out!

Yeah, in reality, what I describe above might also end up mostly just being selection for that one trait, ‘delicious enough’. For most of the time, if where one lives is easy enough for that species or interspecial mix. It might even be a few years until a certain disease sweeps through the area, and maybe at such a time, all the neighbours’ trees are badly effected, and only 1/3 or 2/3 of ones diverse population effected! So cull all of those, and there’s your disease selection! And you have a whole bunch of really diverse seeds from those survivors to plant to replace the ones you removed. Maybe even your neighbours might be interested to have some seeds too, after such an incident!

Imagine if that kind of thing happened once every 10 years or so, maybe often different diseases or pests or weather events. Your neighbourhood might end up with very resilient trees!

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More info on interspecific hybrids in case i’s useful for anyone reading this post whether now or in future:

In the last years, the interest for obtaining complex genotypes has increased, and for this reason, the interspecific hybridizations have been used.

Initially, interspecific hybridization was used to improve plum rootstocks. Thus, the plum rootstock ‘Ishtara’ is a complex interspecific hybrid between P. domestica, P. cerasifera, and P. armeniaca [30]. ‘Jaspi’ plum rootstock was obtained from the crossing between P. salicina Methley and P. spinosa. ‘Marianna’ rootstock was obtained from the combination between P. cerasifera and P. munsoniana [3].

Within the European FP 7 project, a breeding program for the creation of rootstocks with resistance to plum pox virus was carried out. Thus, at the Technical University of Munich, the ‘Dospina 235’ (P. domestica × P. spinosa) and ‘Docera 6’ (P. domestica × P. cerasifera) rootstocks were obtained [31].

In Romania, there were crossed varieties belonging to the P. domestica and P. insititia species with the same number of chromosomes, and several cultivars were named: ‘Silvia,’ ‘Ialomita,’ ‘Diana’ (‘Renclod Althan’ × ‘Early Rivers’), ‘Renclod de Caransebes’ (‘Renclod Althan’ × ‘Wilhelmina Spath’), ‘Doina,’ ‘Zamfira’ (‘Anna Spath’ × ‘Renclod Althan’), ‘Romaner,’ and ‘Iulia’ (‘Tuleu gras’ × ‘Renclod Althan’) [2, 6].

Hybridization between diploid species (P. cerasifera, P. salicina, P. simonii, P. besseyi, P. americana, P. nigra, P. munsoniana, P. angustifolia, and P. hortulana) can be very easy. For example, ‘Santa Rosa’ variety with American origin is a mixture between P. salicina, P. simonii, and P. americana [32].

In recent years, fruits of plum hybrids obtained from interspecific crosses have appeared on the world market:

  • Interspecific hybrids between P. domestica and P. armeniaca called ‘Plumcot®’ (e.g., ‘Red Velvet,’ ‘Royal Velvet,’ ‘Flavor Supreme,’ ‘Flavor Queen,’ ‘Rutland,’ ‘Plum Parfait,’ ‘Spring Satin,’ and ‘Yiksa’). In Bulgaria, Argir Zhivondov made crosses between P. domestica (‘Stanley’ cv). and P. armeniaca (‘Modesto’ cv.) and obtained the cultivar named ‘Standesto’ [21].
  • Interspecific hybrids between (P. domestica × P. armeniaca) × P. domestica and (P. salicina × P. armeniaca) × P. salicina. The name of these hybrids is ‘Pluot®’.
  • Interspecific hybrids between (P. domestica × P. armeniaca) and P. armeniaca called ‘Aprium®’ (e.g., ‘Flavor Delight,’ ‘Flavor Candy,’ and ‘Honey Rich Aprium’).

Source: Plum Breeding | IntechOpen

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Lot of mistakes in that linked internet article. plumcot, pluot and aprium shown as domestica hybrids. Very incorrect. Lot’s of garbage on the web, basic research will show these have no domestica in them. The original breeder’s even say so.
“Ishtara” parentage is salicina, cerasifera and persica, the company that created it says so…

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Ah ok, damn, thanks for that.

I just tried to find specifics out of curiosity. I found a patent for ‘Flavor King’ which seems to be one of his pluots. It seems it’s:
[Mariposa Plum x [Red Beaut Plum x apricot] ] x [Red Beaut Plum x ‘open pollinated’ (no info on pollen parent)]

Confusingly, I see Mariposa Plum listed in some places as Prunus domestica, but in other places as Prunus salicina. And one site just says “The Mariposa plum originated in Pasadena, California, where it was a chance seedling that was selected by Jennie Benedict Thompson in 1923.”

Looking deeper I found this abstract of the paper ‘SPECIES COMPOSITION OF JAPANESE PLUM FOUNDING CLONES AS REVEALED BY RAPD MARKERS’:

Early domestication of diploid plums in the United States was focused on native North American plum species until Luther Burbank imported several Japanese plum (P. salicina Lindl.) seedlings from Japan and intercrossed these with Chinese plums, Eurasian plums, and native American plums. His released plums, which later became founding clones of Japanese-type plums in the United States, were mainly multispecies hybrids. The major founding clones for Japanese-type plums for the California gene pool are ‘Santa Rosa’, ‘Eldorado’, and ‘Gaviota’; and for the southeastern USA are ‘Methley’, ‘Santa Rosa’, and ‘Mariposa’. However, the parentage and consequently the species composition of these multispecies hybrids is poorly documented and has been based on their morphological traits. The objective of this study was to estimate species composition of California and southeastern diploid plum founding clones with 168 RAPD markers generated with eight primers (C10, E6, G6, J5, J8, K3, K18, and N10). The species composition was assessed with sets of diagnostic RAPD markers and was estimated with the RAPD marker frequency data. This analysis confirms that P. salicina, P. simonii , and P. cerasifera are in the backgrounds of these founding clones but raises questions about the P. americana parentage proposed in the development of the founding clones ‘Santa Rosa’ and ‘Gaviota’.

Unfortunately the full article seems to be behind a paywall, I can’t find any way of accessing it. But perhaps that would tell us something about what species are involved in that variety.

From what I could find, perhaps ‘Red Beaut’ is P. salicina? But then, it seems it was developed in California so perhaps that is also an interspecies hybrid?

He does give species details in his patent for ‘Flavor Grenade’, as:
[( (Prunus Salicina x (Prunus Salicina x Prunus armeniaca) x (Prunus Salicina x Prunus armeniaca))] x [(Prunus Salicina x (Prunus Salicina x Prunus armeniaca)) ]

Should I delete that comment of mine above? Perhaps would be better to?

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It’s not uncommon for sellers or low grade publications to list various cultivated plums as Prunus domestica when they are not because people just assume it to be the name for all “domestic” plums.

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You’ll see lots of published crap even from universities mixing up domestica with salicina hybrids and even calling all vintage diploid plums “salicina”. It’s a muddled mess for research, I always try to go to the original source for info.

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Fred Anderson created it in the mid 1960’s, he was big in breeding some great peaches. “Red Beaut” is a cross of “Eldorado” x “Burmosa”, according to its patent. PP2,539.
Only a very few cultivars are pure salicina.

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Off topic, but I remember the first time I had pure salicina in Japan and Taiwan and was completely thrown off by the lack of “plum” flavor I associate with American “salicina” cultivars. Despite their name, it’s interesting how much more popular Japanese plums are in the US than in Japan. In Taiwan, only pluots and Japanese plums imported from California and Chile are commonly sold for fresh eating. Locally grown salicina plums are usually picked half-ripe and lightly pickled.

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Did you eat ripe ones? How do they taste compared with European plums? I don’t think I have ever eaten Prunus salinica, nor any of the interspecies hybrids sold by that name in the US. I’d be interested how the latter two compare to European plums too.

Interesting. Is it similar to umeboshi? I heard umeboshi is made with Prunus mume - according to Wikipedia anyway.

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Yes, they were ripe. European plums are usually much sweeter with a different aroma. The closest thing in flavor to these pure salicina are the fruits of Prunus cerasifera. Not that that really helps you if you haven’t tried those either.

They’re not like umeboshi at all. More like a crunchy sweet/sour/salty pickle. Umeboshi is usually P. mume or ume x apricot hybrids.

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