Hmmm....
Well, to ask a question of ignorance, one time I read where, if you want mold resistance, choose landrace strains from humid tropical areas (like Thailand) that have lots of humidity in the air, because they selected for what grew best and gave them the most desirable results over time.
Is that not a good strategy?
Sure, that is the usual line of thinking, and it turns out also that I think a lot of sativas will have high terpinolene content and the accompanying other pine terpenes. But not all sativas exhibit this, and I don't think it's a guarantee that something labeled as a sativa, or a tropical sativa, will necessarily be bud rot resistant. For example, I grew Green Mountain Grape from Ace Seeds (who specialize in landraces) and it was definitely not bud rot resistant. (Unfortunately, no terpene profile was available.)
I am exploring this in terms of terpenes, because I definitely think that the terpenes are imparting the bulk of the bud rot resistance, and it makes sense. The plant is defending itself from pathogens that want to eat it, including botrytis. A plant that can't defend itself won't produce as much offspring. So they evolved volatile terpenes that pathogens such as fungus are vulnerable to. From my perspective, this is a mechanical/chemical effect on the plant surfaces, whereby the off-gassing volatiles zap the spores at the microscopic level, either killing them or otherwise preventing them from growing.
In the past week I've been tuning into the association between landrace indicas and terpinolene, and indica strains such as Big Bud and Northern Lights that are not too distant genetically (relatively speaking) from landraces. I have heard probably more than once that Grand Daddy Purple – an indica dominant strain – is bud rot resistant (GDP = Big Bud x Purple Urkle). So I checked terpene profiles and found that it contains significant amounts of terpinolene. I was surprised, because I think this is quite rare for an indica. So then I looked deeper, and researched the lineage of Grand Daddy Purple. To make a longer story short... I settled on Atomic Northern Lights as an indica that's terpinolene dominant. But I also want to try out Grand daddy Purple.
From the start in this thread, I have been looking for sativa, indica, and 50/50 hybrids that are highly bud rot resistant. And of course, the reason is... I live in a notoriously bad climate for growing cannabis, in terms of mold and fungus. It's a warm, wet, humid, tropical environment. I have found two strains/phenos so far that are quite good, both from Humboldt Seed Co.: HI-BISCUS (50/50 w/ sativa effects) and Humboldt Dream (indica-dominant). I had zero bud rot with HI-BISCUS. Although I haven't seen a terpene profile yet for HI-BISCUS, there's plenty of evidence on the internet that the phenos are either terpinolene-dominant or high in terpinolene. As for Humboldt Dream phenos, the terp profiles are even more obscure. I've seen some evidence of high amounts of pinene, but no evidence yet of terpinolene. Humboldt Dream does show some bud rot resistance (last harvest was quite good), and some degree of leaf mold resistance, but not fantastic.
There is the physical/structural dimension to avoiding bud rot too. Plants with narrow leaves and a more stretchy structure tend to be the evolutionary outcome of humid tropical cannabis. Plants with massive juicy buds/colas always have more tendency to various kinds of fungal attacks. Maui Waui is your classic Hawaiian strain (landrace more or less). Look to that form, or stretchy narrow-leaf phenos of whatever appeals to you, and those plants will do better at getting air moving inside the plant . Do your own crosses with promising strains. Luther Burbank would plant out thousands of seedlings and select a few; this is essentially landrace evolution speeded up to a season or so. We can't plant thousands of seeds, but we can intellegently select the best of what we have. Try to get regular seeds of a good strain so you have a true male to work with and slowly breed for the traits you want. If you have a few good strains the genes are in there. We can breed to select and enhance what is best for a location. The best plant for you and your location probably does not yet exist.
Again... sure, we all know that sativas are associated with bud rot resistance. Is it because of their structure? I can believe that it contributes, but I don't think it's the primary reason. I grew beautiful 90% sativas from Green Mountain Grape regular seed, and they succumbed to major bud rot (ACE refers to it as an "almost pure sativa"). Here's the
GMG lineage. I flowered two females, one a green bud pheno, the other a purple bud pheno. Both had lots of bud rot. Did I just happen upon two unfavorable phenos? Possibly. But that points out another problem, and that's phenotypic variability. I'm looking for genetics that are reliably bud rot resistant without needing to search through phenos. I think this approach is highly possible and practical, if indeed the terpinolene/pine terps theory pans out. And there is evidence, because – as I said – it appears that HI-BISCUS reliably produces phenos with significant terpinolene content, and the results are fantastic.
But there's more to the picture...
I just harvested my CBD #9, which is a 10% CBD variety of Cherry Blossom (THC < 1%). I would say this is a 50/50 hybrid, indica dominant. I have never had my single pheno tested for terps, however I've seen a terpene profile that shows high amounts of myrcene and pinene, but not terpinolene. I've done multiple harvests of this plant over the past few years, and there's always some bud rot. This time I grew in a 10 gal. pot (instead of 5 or 7 gal), for the first time, and the plant grew very tall and I topped at 8 ft. to fit in the greenhouse. The top buds were some of the
best buds I've ever harvested – big and dense. Basically zero bud rot in those top colas. There was some bud rot, especially lower down, but it was very isolated. ...I was kind of blown away.
So, it has now become obvious to me that the health of the plant is super important, and in my case – since I've covered basically all the other bases – the only remaining factor was pot size. The vigor of the plant is super important at the time leading up to the harvest. This is the time when both premature senescence can set in, and bud rot can get started. If the pot size is sufficient, then the needs of the plant are better met. And it's not just about nutrients, but about the health of the root zone. A pot that's too small results in an unhealthy root zone. Again, this matters the most at the time leading up to harvest, in terms of resistance to bud rot. I have another pheno of the Cherry Blossom, my CBD #1, and it's a very amazing, vigorous plant. I have a clone mom of CBD #1 right now in a 1 gal. pot, and she's way too big for the pot, but still looking absolutely amazing. So, plants can look amazing in pots that are too small, but bad things can happen when you try to flower them in pots that are too small.
In my case, with my outdoor greenhouse grow, I can safely say I've been flowering plants in pots that are too small (5, 6, and 7 gallon.) But I also flowered some plants in 15 gal fabric smart pots, and they also showed lots of bud rot. The fact that I was unknowingly stressing the plants in the smaller pots, leading up to flowering, pushed me to do three things: 1) look for ways to chemically suppress the leaf mold and bud rot (or apply beneficial biological foliar sprays), and 2) begin to think about finding strains that are naturally resistant to these pathogens.
I ultimately decided to completely bypass the chemical/biological methods – I simply don't want to deal with that, because it's too much work, given the realities of my tropical environment here. So, this line of reasoning led me to Humboldt Seed Co. and their HI-BISCUS strain, in Nov. 2022, which was specifically bred for mold/fungus resistance. Their seed sprouted like a dream. The seedlings vegged over winter, and I grew one pheno to
flower and harvest, in a 5 gal. pot. In May of 2023 I had a
great harvest with zero bud rot. There was plenty of leaf mold leading up to harvest, but no bud rot. And so, this is how a seed was planted in my head to begin looking at terpenes.
Hence began this thread, and my quest for mold/fungus resistant strains of sativa, indica, and 50/50 hybrids. The pot size of 10 gal (black plastic), along with good timing of up-potting to 10 gal and transfer from veg to flower, is the golden ticket. I've been scheming on the perfect terpene combination to provide both bud rot and leaf mold resistance. It seems I'm on the right track for bud rot resistance, with terpinolene and the associated pine terpenes. Leaf mold resistance is still a bit more mysterious, but we'll see what turns up next with the new genetics... Slymer pheno of Chernobyl (sativa-dominant), Agent Orange (sativa-dominant), Grand Daddy Purple (indica-dominant), and Atomic Northern Lights (indica-dominant). All are terpinolene strains.