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01-03-2016, 12:08 PM | #1 (permalink) |
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* Ask Gabe *
Hi Gabe, you are a bonafide researcher and our best expert to ask about descriptors.
Can the environment change the scoring of Plant Descriptor: 6.4.5 Peduncle hairiness, and if so to what extent? Descriptors for Musa Minimum highly discriminating descriptors are marked with a star, and 6.4.5 is marked with a star. Using a FHIA-01 Goldfinger as an example and disregarding all other descriptors, can they be very hairy at one location and hairless at another location? can some be very hairy and also some be hairless grown side by side at the same location?
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01-03-2016, 07:33 PM | #2 (permalink) |
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Re: * Ask Gabe *
Well, that's a rather complex question to answer with lots of variables, but I'll do my best to keep it simple.
Environment can theoretically change any trait of a plant, as everything is a result of genetics and the environment. This is not the same as what is referred to as genotype by environment (GxE). A trait such as the presence or absence of hair/(pubescence) on the peduncle is most likely a simple, single-gene-controlled trait (being qualitative rather than quantitative) that should be present in most environments. However, the relative degree to which the hair is present could reasonably be somewhat variable within a clone in different environments, but I don't think it would be totally absent in one environment and visibly present (in any amount) in another. In the exact same environment, if some plants of the same clone had it and others didn't, my first thoughts would be: 1. Is it really the exact same environment?; same sun exposure, same position relative to other plants, same water/fertilizer/soil etc... 2. Is it really the exact same plant?; from the same source, and not a potential minor off-type. 3. Is it really not present at all in some, or is it just present in very small amounts? If you have doubts you can take a mist bottle set to it's finest spray setting and gently mist the peduncle to better observe the presence of any hair which may be difficult to see otherwise.
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01-03-2016, 10:14 PM | #3 (permalink) |
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Re: * Ask Gabe *
Thanks Gabe.
Basically I was wondering if that descriptor could be used independently to prove that plants are not the same cultivar, either grown in the same environment or in different environments. There seems to be many different types of FHIA-01 Goldfingers on the org. Why would they note it as a highly discriminating descriptor?
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01-03-2016, 10:22 PM | #4 (permalink) |
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Re: * Ask Gabe *
I would imagine that those single gene traits are quite susceptible to mutation. I've had plants from the same tissue culture lot be different, and I've had a pup that was different than the mother. Perhaps the question should really be, how stable is a trait.
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01-04-2016, 04:16 PM | #5 (permalink) | ||
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Re: * Ask Gabe *
Quote:
Ideally, a verified true-to-type field grown sucker is initiated into culture as the original explant and then subcultured only about 5-10 times or no more than 1 year in-vitro, resulting in the production of about 1000 plants, at which point that tissue culture line is ceased, and new explant lines are initiated (in reality this is a continuous and overlapping process in high-production facilities). The rate and types of mutation observed varies among cultivars, but as a general rule no plant of economic importance should be indefinitely tissue cultured. Quote:
This also highlights a more fundamental question of what is a cultivar? In edible bananas, they are asexually propagated and thus the generation of new diversity is much lower than through sexual propagation, but there is still diversity generated through somatic mutation. At what point a new mutation is upgraded and deemed a new cultivar is partly based on how stable it is, but it is also just the opinion of whomever is evaluating it and it's appreciated significance. Most mutations/off-types are undesirable, and so they are eliminated to maintain the integrity of the cultivar. If the off-type is desirable in some way, it can be deemed a new cultivar. Personally I don't think variations in peduncle hairiness justify a new cultivar, but if there are other mutations of importance that came with it, and you could use the peduncle hairiness as a marker to track the presence of another more important trait (after lots of repeated testing and verification it is stable), then perhaps it is more justified. There is a 'Williams' off-type with hairy fruit, it is a minor genetic mutation but because it affects the fruit which is the most economically critical part of the plant to not have adverse mutations in, it is more or less regarded as a different cultivar. If that same level of genetic mutation happened in another trait, such as on the peduncle, I don't think anyone would really care, it would just be regarded as normal variation within a cultivar. In open pollinated (OP) seed-propagated crops, such as OP corn, there are many different genotypes within the population, but they are generally regarded as one cultivar because they are are stable for the traits of economic or horticultural importance. In bananas, there is the subgroup system of classification which in theory means that all cultivars within a subgroup are somatic mutations from the same original seedling (the classification of cultivars into subgroups is incomplete and on-going, but generally worked out for all the major triploid cultivars). A banana subgroup is kind of like an OP corn population which has not been selected and refined into a cultivar. Variation in OP populations is what has (in part) made hybrid corn so popular as there is essentially no genetic variation within the cultivar. A banana cultivar is like the hybrid corn, very uniform, but will not stay uniform over time without careful monitoring. 'Goldfinger' is a seedling, and so any mutations arising from it's creation onwards could be regarded as new cultivars within a new subgroup, but since it is so new, there are not very many. There is however one grower in Australia who has selected his own Goldfinger mutation and is growing it commercially as a distinct cultivar. The Cavendish subgroup is a great example to see how somatic mutations can generate a subgroup, perhaps one day there will be a Goldfinger subgroup with many different cultivars within it.
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02-02-2016, 10:03 AM | #6 (permalink) |
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An Ancient Mariner
An Ancient Mariner I feel rather like the Ancient Mariner who was rash enough to shoot an albatross and then had the corpse hanging round his neck for years (stinking probably). I had a substantial hand in inventing INIBAP (though not the name) in the early 1980s and the body has been kind enough to keep me on the mailing list despite my nasty remarks about what it is doing. Anyway, elderly gents who have shot albatrosses are notorious for yacking on and on about them. INIBAP is an acronym for ‘International Network for the Improvement of Bananas and Plantains’. The body was originally independent but then came under the direction of IPGRI in Rome; this body was the IBPGR and everyone knows what that means. INIBAP may have Roman bosses but it is centred on CIRAD in Montpellier, with networking tentacles spreading round the tropics. Networks are very trendy these days but the CG did not invent them. Feeding poor people by developing one of the halfdozen great crops of the world (but an almost totally neglected one) was INIBAP’s primary objective. Alas, it got enmeshed in Science, especially Pathology and in vitro tricks and it largely forgot the feeding-of-poorpeople bit of the story. Recent publications bear this out all too clearly. The core activity of INIBAP ought to have been banana breeding, a subject it has hardly touched, apart from faintly promoting the excellent efforts of FHIA in Honduras, as related in these pages a while ago (Rowe 1999; Simmonds 1999). Banana breeding is, of course, much harder than plant pathology and lends itself less well to the quick multi-author paper. So biotechery, hordes of new viruses, informatics and networks will have to do, even if poor folk remain under-fed; FHIA varieties should reach them someday. There have been some peculiar bureaucratic goings-on, too. INIBAP has spawned a body called PROMUSA (I am not clear why), which was, with GILB, the original GLOBAL PROGRAMME; since GILB is/was a CIP invention to breed resistance to potato late blight the logic was not wholly clear, unless INIBAP was making a play for CIP. A special programme for blight was as little needed as special programmes for banana diseases. And, much to CIP’s credit, they regarded blight resistance empirically as an exercise in handling polygenes, not as a Holy Grail. Whatever the history, GILB has disappeared from the INIBAP reckoning, along with late blight. Incidentally, potato and sugarcane breeders have much in common—they tend to treat nasty diseases empirically. Recent publications include the Annual Report (1999), a very attractive document with nice coloured pictures, the latest issue of the banana mag, INFOMUSA, with a four-page insert on PROMUSA, and a memorial document on Paul Allen. This last is published by INIBAP though apparently the work of FHIA; Allen was a very successful banana collector around 1960 when he assembled the large UFCo collection in Honduras, of which the survivors are now retained and well used by FHIA. This is a proper collection, meant for practical use; not one of in situ mushes which are currently so fashionable. Alas, the tribute to Allen does the great man little credit; the photos are bad, descriptions are incomplete and unexplained and the systematics uncertain. It looks as though ploidies were established by inspection without any proper chromosome counting—it can be done fairly well by the experienced but is better not attempted by amateurs unless tested against good metaphase plates. INIBAP is undoubtedly trendy. Its Report hardly mentions that vulgar old-fashioned plant breeding but is loaded with the delights of plant pathology (any disease will do for a paper or two); it promotes biotechery and in vitro stuff like crazy: it strongly favours informatics and computing, approves of in vitro conservation (while happily printing photos of planting new clones alongside the promotion): it muddles its taxonomy and there is never a chromosome count in sight. But there are some signs of grace: collections are being filled in, root systems are analysed and nutritional value is treated. (Bananas are pretty good nutritionally but not nearly so good as potatoes). Poor folk in the moister tropics desperately need an INIBAP; it is a pity the one we have got is not a bit better adapted to the demands placed upon it. Above all, decent breeding and let any essential plant pathology follow. No-one ever improved a crop by researching its diseases as a starting point, no matter what the bureaucrats and plant pathologists think. N.W. Simmonds Tropical Agriculture Association - March 2001 Hi Gabe, Can you explain this in a way easily understood? " It looks as though ploidies were established by inspection without any proper chromosome counting—it can be done fairly well by the experienced but is better not attempted by amateurs unless tested against good metaphase plates." Illustrated guide to the identification of banana varieties in the South Pacific
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02-02-2016, 11:03 AM | #7 (permalink) |
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Re: * Ask Gabe *
You can count chromosomes during metaphase. A diploid will have 22, a triploid will have 33, and a tetraploid will have 44.
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02-02-2016, 12:17 PM | #8 (permalink) | |
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Re: * Ask Gabe *
Quote:
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02-02-2016, 12:43 PM | #9 (permalink) |
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Re: * Ask Gabe *
I have no idea how an amateur would do it, but I suppose there are some phenological characteristics that could differentiate between diploid, triploid, and tetraploid...at least some of the time.
http://www.fruits-journal.org/articl...8/03/i8306.pdf if you want to try it yourself. |
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02-02-2016, 12:58 PM | #10 (permalink) | |
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Re: * Ask Gabe *
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02-02-2016, 11:58 PM | #11 (permalink) |
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Re: * Ask Gabe *
I'm not sure exactly what part you would like to understand more, but as for trying to determine ploidy levels it can be tricky. The general descriptions you posted are more or less true, but with so many exceptions and deviations that they can't be relied on for good data, they are more of a rough starting point. There are many many examples of very well trained and expert banana taxonomists mis-judging ploidy levels on new accessions. These days any serious ploidy determination is done by flow cytometry, which can also determine genome composition at the same time with good accuracy in most cases.
As for the root squash procedure, if you have any reasonable experience working in a lab and have the right equipment (which in itself could be the limiting factor), it could be performed without too much hassle. However, even if you succeed at making a nice slide and it looks good, without training to know exactly what to look for you might not get too far. I think what he means by "unless tested against good metaphase plates" is essentially having a good set of verified samples of which to compare your samples to, particularly ones with the chromosomes nicely aligned along the metaphase plate. If I were to do it, I would do it many times on plants of known ploidy, diploids, triploids and tetraploids, and then have a good set of slides to compare unknown plants to. It can be challenging to get good samples as when the chromosomes are not actively being duplicated, they are not in the nice orderly configurations you see in text book examples, they are a mess, and so to observe them in a discrete countable state requires some searching, and knowing what you're looking at. That being said, I know the theory behind it but I've never done it personally. I did work for awhile on a project for a professor of mine doing ploidy level estimations of induced-polyploid landscaping trees but we were able to do what we needed with guard cell measurements, an extremely easy procedure which sadly does not work for Musa. Unless you have a breeding program or are collecting some really exotic unknown germplasm, I think the easiest way to determine the ploidy level of a plant you have would just be to ID it and look it up. If you are really studying bananas and come across some puzzling Musa you need a genome analysis of, you can send them off to the Musa Genotyping Center.
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02-03-2016, 08:14 AM | #12 (permalink) | |
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Re: * Ask Gabe *
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