Hi Gang, Recently, while trying to find information about Crinum Mosaic Virus, I contacted plant pathologists around the world. They also helped me with information about Hippeastrum Mosaic Virus. As near as I could find, at the time, only one virus is described for Hippeastrum--at least only one that is regularly known. The main thing about Hippeastrum Mosaic Virus (HiMV) is that it is a potyvirus and it is almost certainly spread by insects and cutting tools. It is almost certainly not spread by leaf to leaf contact. One thing I do to keep HiMV (and CriMV) from spreading, should it be in my plants, is to regularly apply insecide. I'm not frantic about it, but I don't let infestations build up and I apply a systemic insecticide (imidacloprid) aboutr 3 times a year. I use the granulated formulation sold by Bayer (it also contains cyfluthin). I sprinkle a tablespoon or so on top of the soil of gallon containers, and a quater cup for 5-gallon containers (approximate amounts). For very large containers I might use a cup of granules (25 gallons). You won't be able to cure virus-infected plants in your garden (at least not by gardening methods), but you can easily prevent spread of HiMV by using imidacloprid and by cleaning cutting tools between plants (including shovels and clippers). Cordially, Joe ----- Original Message ----- From: <pbs-request@lists.ibiblio.org> To: <pbs@lists.ibiblio.org> Sent: Tuesday, November 21, 2006 4:29 PM Subject: pbs Digest, Vol 46, Issue 26 > Send pbs mailing list submissions to > pbs@lists.ibiblio.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://www.pacificbulbsociety.org/list.php > or, via email, send a message with subject or body 'help' to > pbs-request@lists.ibiblio.org > > You can reach the person managing the list at > pbs-owner@lists.ibiblio.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of pbs digest..." > > > List-Post: <mailto:pbs@lists.ibiblio.org> > List-Archive: <http://www.pacificbulbsociety.org/pbslist/> > > Today's Topics: > > 1. Re: Virus (totototo@telus.net) > 2. Lilies & virus (John Bryan) > 3. Re: Lilies & virus (John T Lonsdale) > 4. Re: Lilies & virus (Alani Davis) > 5. Re: Lilies & virus (Jim McKenney) > 6. Re: Lilies & virus (John T Lonsdale) > 7. Clonal breakdown (John Bryan) > 8. Re: Clonal breakdown (Diane Whitehead) > 9. Re: Clonal breakdown (Boyce Tankersley) > 10. Re: Lilies & virus (eob@vqme.com) > 11. Re: Neomarica - more (piaba) > 12. Re: Clonal breakdown (Jim McKenney) > 13. FW: Clonal breakdown (John T Lonsdale) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Tue, 21 Nov 2006 10:29:34 -0800 > From: totototo@telus.net > Subject: Re: [pbs] Virus > To: pbs@lists.ibiblio.org > Message-ID: <20061121182902.73KSKR1U83@priv-edmwaa05.telusplanet.net> > Content-Type: text/plain; charset=US-ASCII > > On 1 Jan 90, at 0:21, John Bryan wrote: > >> ...Growers in the Netherlands are very conscious of the need to >> sell only the best possible stock. > > I nearly choked on my morning bagel when I read that. Maybe they're > *conscious* of this need, but Dutch growers don't seem to act on that > consciousness. The Dutch bulb trade is notorious for mislabelling > what they send out, and it's well known that some types of bulbs from > Dutch sources are virtually always virused, lilies being the classic > example. I could mention the horrible virused form of Crocus > kotschyanus, but I won't. > > The mislabelling is insidious because they are generally careful to > substitute something with approximately the same look. Out of some > bluish Crocus biflorus cultivar? Just grab a bunch of C. > tommasinianus; no one will ever notice the difference. It is no > accident and esp. now when the bulbs are all prepackaged, it isn't > due to customers mixing the contents of the bins. That's the excuse I > used to get when I complained about misnamed bulbs! > > And some of the other "bulbs" one buys are diseased in other ways: > one friend with access to the necessary equipment determined that a > dahlia from Dutch sources was loaded with nematodes. > > It may be that you are distinguishing "growers" from "wholesalers" > and "distributors", but a man is known by the company he keeps. The > entire Dutch bulb trade is, I am sorry to say, unreliable and has > known for its failings since at least 1950 when E. B. Anderson > inveighed against mislabelled Dutch bulbs. > > Simply put, it appears that the Dutch bulb industry is long on profit > motive at the expense of ordinary everyday ethics and honesty. Their > long history of selling wild-collected bulbs, with the end result of > near extinction of many species, is just another example. > > > -- > Rodger Whitlock > Victoria, British Columbia, Canada > Maritime Zone 8, a cool Mediterranean climate > > on beautiful Vancouver Island > > > ------------------------------ > > Message: 2 > Date: Mon, 01 Jan 1990 00:38:06 -0800 > From: John Bryan <johnbryan@worldnet.att.net> > Subject: [pbs] Lilies & virus > To: pbs@lists.ibiblio.org > Message-ID: <259F16EE.728A69A6@worldnet.att.net> > Content-Type: text/plain; charset=us-ascii > > Way back in the 60's, the lily hybrid Enchantment, introduced by Jan de > Graaff's Oregon Bulb Farms, began to loose the size of flowers and the > bud count. Many acres of this hybrid had been grown for a great number > of years. It was decided to propagate, by tissue culture, a new stock. > Enchantment was, the first lily to receive a Patent, being grow widely > for cut flower production as well as a garden plant and we exported many > thousands to the Netherlands. It is to be noted that the plants did not > show signs of virus, just the flower size and count diminished. This was > thought to be a clonal breakdown, not an unusual occurrence and I think > this was a correct diagnosis. > > The result of the tissue culture was the new stock, so propagated, > regained the flower size and bud count of previous years. Thus it is not > only virus that causes such problems, but clonal breakdown is another > factor of a decline of a variety/culivar. I suppose Enchantment is still > being grown but has been superseded by newer hybrids, but the bloodline > of this great Asiatic lilly can still be seen in progeny, for example > the black tips of the buds etc. > > This might be of interest, the point being decline of a plant is not > always due to a virus, but continued propagation by vegetative means can > also cause problems. Cheers, John E. Bryan > > > ------------------------------ > > Message: 3 > Date: Tue, 21 Nov 2006 14:26:18 -0500 > From: "John T Lonsdale" <john@johnlonsdale.net> > Subject: Re: [pbs] Lilies & virus > To: "'Pacific Bulb Society'" <pbs@lists.ibiblio.org> > Message-ID: <009301c70da2$eb9fa600$6601a8c0@XPS400> > Content-Type: text/plain; charset=us-ascii > > John Bryan, > > Can you please explain what you mean by 'clonal breakdown'? How does TC > of > a lily suffering from 'clonal breakdown' fix this? > > Thanks. > > > John T Lonsdale PhD > 407 Edgewood Drive, > Exton, Pennsylvania 19341, USA > > Home: 610 594 9232 > Cell: 484 678 9856 > Fax: 801 327 1266 > > Visit "Edgewood" - The Lonsdale Garden at http://www.edgewoodgardens.net/ > > USDA Zone 6b > > > > > ------------------------------ > > Message: 4 > Date: Tue, 21 Nov 2006 14:41:54 -0500 > From: "Alani Davis" <adavis@ecoresource.com> > Subject: Re: [pbs] Lilies & virus > To: <john@johnlonsdale.net>, "'Pacific Bulb Society'" > <pbs@lists.ibiblio.org> > Message-ID: <006801c70da5$19ffd4f0$0305a8c0@crinum> > Content-Type: text/plain; charset="us-ascii" > > I am curious about this as well. I have heard this used many times as a > reason for decline of a variety through clones do to excessive asexual > reproduction, but would be the mechanism for this "decline"? How can > genetic > "vigor" be "lost"? How can one "know" it is clonal breakdown and not > environmental or pathanogenic? > > Alani Davis > Tallahassee, Florida > > > -----Original Message----- > From: pbs-bounces@lists.ibiblio.org [mailto:pbs-bounces@lists.ibiblio.org] > On Behalf Of John T Lonsdale > Sent: Tuesday, November 21, 2006 2:26 PM > To: 'Pacific Bulb Society' > Subject: Re: [pbs] Lilies & virus > > John Bryan, > > Can you please explain what you mean by 'clonal breakdown'? How does TC > of > a lily suffering from 'clonal breakdown' fix this? > > Thanks. > > > John T Lonsdale PhD > 407 Edgewood Drive, > Exton, Pennsylvania 19341, USA > > Home: 610 594 9232 > Cell: 484 678 9856 > Fax: 801 327 1266 > > Visit "Edgewood" - The Lonsdale Garden at http://www.edgewoodgardens.net/ > > USDA Zone 6b > > > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://www.pacificbulbsociety.org/list.php > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ------------------------------ > > Message: 5 > Date: Tue, 21 Nov 2006 14:45:32 -0500 > From: "Jim McKenney" <jimmckenney@jimmckenney.com> > Subject: Re: [pbs] Lilies & virus > To: "'Pacific Bulb Society'" <pbs@lists.ibiblio.org> > Message-ID: <000c01c70da5$9b4b8090$2f01a8c0@Library> > Content-Type: text/plain; charset="us-ascii" > > While we're waiting for John Bryan's response on this, I'll add this. What > John Bryan called clonal breakdown might be what I think of as clonal > drift. > > > Clonally propagated material varies over time, and the amount of variation > is probably proportional to the number of replications involved. > > To keep a clonally propagated product within the expectations of > consumers, > it's necessary periodically to reselect typical material on which to base > future cloning. > > This clonal drift is not necessarily a disadvantage. Many of the tulips of > the double early division are said to be somatic mutations of the tulip > Murillo, which itself is a somatic mutation of a single early tulip. So > where there was originally one product, there are now many, all pieces of > one original seedling. > > > Jim McKenney > jimmckenney@jimmckenney.com > Montgomery County, Maryland, USA, USDA zone 7 > My Virtual Maryland Garden http://www.jimmckenney.com/ > > Webmaster Potomac Valley Chapter, NARGS > Editor PVC Bulletin http://www.pvcnargs.org/ > > Webmaster Potomac Lily Society http://www.potomaclilysociety.org/ > > > > > > > > > > ------------------------------ > > Message: 6 > Date: Tue, 21 Nov 2006 14:46:59 -0500 > From: "John T Lonsdale" <john@johnlonsdale.net> > Subject: Re: [pbs] Lilies & virus > To: "'Pacific Bulb Society'" <pbs@lists.ibiblio.org> > Message-ID: <009801c70da5$cf72ca40$6601a8c0@XPS400> > Content-Type: text/plain; charset=us-ascii > > John Bryan wrote - "It is to be noted that the plants did not show signs > of > virus, just the flower size and count diminished." > > This is rather like saying the patient didn't show signs of HIV infection, > his CD4 cell count just plummeted; his viral load went through the roof, > he > got a bunch of opportunistic infections and suffered from Kaposi's > sarcoma. > > If reduced flower size and count aren't classic signs of viral infection > in > plants then I don't know what is. > > Perhaps you mean that the lily didn't have a bunch of yellow streaks in > the > leaves? > > Thanks, > > John T Lonsdale PhD > 407 Edgewood Drive, > Exton, Pennsylvania 19341, USA > > Home: 610 594 9232 > Cell: 484 678 9856 > Fax: 801 327 1266 > > Visit "Edgewood" - The Lonsdale Garden at http://www.edgewoodgardens.net/ > > USDA Zone 6b > > > > > ------------------------------ > > Message: 7 > Date: Mon, 01 Jan 1990 03:08:44 -0800 > From: John Bryan <johnbryan@worldnet.att.net> > Subject: [pbs] Clonal breakdown > To: pbs@lists.ibiblio.org > Message-ID: <259F3A3C.2871B91C@worldnet.att.net> > Content-Type: text/plain; charset=us-ascii > > Dear All: > > Hybrid vigor, while evident in plants raised from seed, does not last > for ever if continued asexual reproduction of a plant is continued over > many years. The classic example perhaps is to be found in the strawberry > Royal Sovereign, which just failed after many years. At one time it was > far ahead of other cultivars, but then lost many of the qualities for > which it was renowned. To my knowledge such loss of desired qualities > were simply lost due to the continued asexual propagation. Just what > happens when such does take place I do not know, but such has been > refereed to as Clonal Breakdown. Possibly the desired arrangement and > composition of the cells in the plant(s) was changed. > > John Lonsdale asked how TC fix this. Again a definitive answer, to my > knowledge, as not been determined, but it does work. Perhaps this method > of propagation is taking advantage of cells that are, for want of a > better explanation, stronger and closer to the original cells of the > first crosses and better replicas of cells carrying the desired > qualities. > > I should have mentioned the plants of Enchantment did not show any > visible signs of virus, to all intents and purposes the plants appeared > to be the same, except for size of flowers and bud count. > > Here it must be stated, those plants used for asexual propagation, were > selected in the field, the strongest, those with good flower size and > bud count were those selected and these plants showed no color variation > in the foliage at all. Selecting those plants that are the most vigorous > is an ongoing practice of good growers. When growing many hundreds of > Dahlias, I used to tag those tubers for propagation in the field and > they were lifted first prior to the lifting of others. > > John Londsale asks if reduced flower size and count are not classic > signs of viral infection, perhaps they are, but are not such accompanied > by other signs as well, such as changes in the foliage? Does this mean > such changes as clonal breakdown do not exist? When examined in the 60's > for virus, using the techniques available at that time, no virus was > found. > > Rodger Whitlock almost choked on his bagel, when he read my comments > regarding growers in the Netherlands, if you have found such poor > practices s you describe, I hope you have reported such to all > authorities who could challenge the practices and do something about it. > Is this perhaps a reason why such strict regulations are now in place > with importation of plants from overseas and which are decried by so > many? Perhaps the USDA are correct! In any profession there are rogues, > but firms such as Hoog and Dix, to mention but one, strive to maintain > the highest standards in nomenclature and health of the products they > sell. To label all growers as being, in effect, dishonest is not only > untrue but, in my opinion a libelous statement. such as Dahlias loaded > with nematodes. To which grower(s) are you referring? Have you reported > them to authorities? If not, why not? As to the selling of wild selected > bulbs, I presume you are aware of the rule governing such and these > rules are and have been imposed by the authorities in the Netherlands. > > Alani Davis asked how can one know if it is clonal breakdown and not > environmental or pathanogenic? I do not know, but the term clonal > breakdown was the term we used, other factors may well have played a > part, but let us not blame virus for all such occurrences, especially > after tests were made to see if virus was present. But as I mentioned, > this was way back in the 60's and more recent procedures might be able > to answer this question. > > The posting of Jim McKenney was interesting. I had not heard the term > Clonal Drift before, but obviously this must be the same. jim, as > mentioned above, steps were taken to keep the product within the > expectations of the consumer. this is why that, during the last years I > was with Oregon Bulb Farms, we were relying on 'strains' as such, being > seed of crosses between established clones as were the seed parents, had > vigor and the variation in height, color, size and number of flowers > were between very narrow limits. Black Dragon Strain took the place of > the clone Black Dragon, and Golden Splendor Strain took the place of the > clone of the same name, etc. Jim, could you explain somatic mutations? > How do such differ from other mutations/ > Cheers and Happy Thanksgiving to all I hope your turkeys are tasty, and > good eating and would there be clonal breakdown in such birds brought > about by inbreeding? > > > ------------------------------ > > Message: 8 > Date: Tue, 21 Nov 2006 13:38:02 -0800 > From: Diane Whitehead <voltaire@islandnet.com> > Subject: Re: [pbs] Clonal breakdown > To: Pacific Bulb Society <pbs@lists.ibiblio.org> > Message-ID: <CA623268-73B5-45D7-AE3D-16753CFFC775@islandnet.com> > Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed > > > I have read articles on human aging that state that cells can > duplicate themselves only a certain number of times. I'm not sure > what happens when this point is reached: do they stop? do they > accumulate mutations? > > Could this limit on cell duplication also be present in plants? > > Diane Whitehead > > > ------------------------------ > > Message: 9 > Date: Tue, 21 Nov 2006 15:43:12 -0600 > From: "Boyce Tankersley" <btankers@chicagobotanic.org> > Subject: Re: [pbs] Clonal breakdown > To: "Pacific Bulb Society" <pbs@lists.ibiblio.org> > Message-ID: > <52857FDB394B7E45BA1F2E60D7313E2A059CC906@cbgmail.chicagobotanic.org> > Content-Type: text/plain; charset="us-ascii" > > This information is from my memory so subject to error. I believe I read > the teliospores shorten everytime a cell divides. After a number of > years they are, in effect, down to the bare bones. It is at this stage > that decreases in vigor and other characteristics are noticeable. > > Boyce Tankersley > btankers@chicagobotanic.org > > -----Original Message----- > From: pbs-bounces@lists.ibiblio.org > [mailto:pbs-bounces@lists.ibiblio.org] On Behalf Of Diane Whitehead > Sent: Tuesday, November 21, 2006 3:38 PM > To: Pacific Bulb Society > Subject: Re: [pbs] Clonal breakdown > > > I have read articles on human aging that state that cells can > duplicate themselves only a certain number of times. I'm not sure > what happens when this point is reached: do they stop? do they > accumulate mutations? > > Could this limit on cell duplication also be present in plants? > > Diane Whitehead > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://www.pacificbulbsociety.org/list.php > > > ------------------------------ > > Message: 10 > Date: Tue, 21 Nov 2006 15:58:15 -0500 (EST) > From: eob@vqme.com > Subject: Re: [pbs] Lilies & virus > To: "Pacific Bulb Society" <pbs@lists.ibiblio.org> > Message-ID: <1727.4.136.141.181.1164142695.squirrel@http://www.vqme.com/> > Content-Type: text/plain; charset=iso-8859-1 > > "Clonal breakdown" is an interesting term, and I do know that continued > propagation of many plants can lead to decline in vigor, etc., but what > does the term actually refer to? If it is actually a change in the > genetics of the plant, then no amount of tissue culturing and "cleaning > up" of the clone is going to change the genetics back to the original. > > Does anyone know what the theory is re what is actually taking place if, > in fact, it is not removing virus. For that matter if the virus has been > incorporated into the genes (as often happens), then how do they clean > that up by tissue culture? Or, are the answers to these questions to > technical for this list? > > Ernie O'Byrne > Eugene, Oregon USA > > >> Sender Allowed >> >> Way back in the 60's, the lily hybrid Enchantment, introduced by Jan de >> Graaff's Oregon Bulb Farms, began to loose the size of flowers and the >> bud count. <snip> This was >> thought to be a clonal breakdown, not an unusual occurrence and I think >> this was a correct diagnosis. >> > <snip> >> >> This might be of interest, the point being decline of a plant is not >> always due to a virus, but continued propagation by vegetative means can >> also cause problems. Cheers, John E. Bryan >> >> > > > > > ------------------------------ > > Message: 11 > Date: Tue, 21 Nov 2006 14:17:12 -0800 (PST) > From: piaba <piabinha@yahoo.com> > Subject: Re: [pbs] Neomarica - more > To: Pacific Bulb Society <pbs@lists.ibiblio.org> > Message-ID: <20061121221713.96187.qmail@web51902.mail.yahoo.com> > Content-Type: text/plain; charset=iso-8859-1 > > i was traveling with mauro in 2001 when we found and > photographed that pic of N. glauca on the website. > flowers are smaller than other Neo. in that trip, > there were also 2 other weird irids we found in MG > state, unfort. neither one in bloom. one had > succulent leaves that were curvy (it could be the one > that he has as Pseudo. recurvata on his website), and > the other one had very thin and long but cylindrical > leaves. seeds of this last one germinated for me as > very thin tufts of grass but none survived to > adulthood. > > actually, when i think of it, we found so many weird > plants in the "campos rupestres" of MG, incl. some > weird yellow-flower bulb in the Rapateaceae family, > Sysirinchiums, Zephyranthes, crazy Melastomataceae > (not bulbs of course),and wonderful tuberous > APocynaceae with gorgeous flowers. > > ========= > tsuh yang > > --- Lee Poulsen <wpoulsen@pacbell.net> wrote: >> Mauro Peixoto has photos of the following species >> (as well as two >> very nice looking unnamed species): >> Neomarica glauca >> > http://mpeixoto.sites.uol.com.br/iridaceae/… > > > > > ____________________________________________________________________________________ > Sponsored Link > > Mortgage rates near 39yr lows. $420k for $1,399/mo. > Calculate new payment! http://www.lowermybills.com/lre/ > > > ------------------------------ > > Message: 12 > Date: Tue, 21 Nov 2006 17:18:20 -0500 > From: "Jim McKenney" <jimmckenney@jimmckenney.com> > Subject: Re: [pbs] Clonal breakdown > To: "'Pacific Bulb Society'" <pbs@lists.ibiblio.org> > Message-ID: <001501c70dba$f3ed93e0$2f01a8c0@Library> > Content-Type: text/plain; charset="us-ascii" > > John Bryan asked "Jim, could you explain somatic mutations? " > > I'm glad you asked this, John because it gives me the chance to tie > together > some disparate threads in my past postings. > > Somatic mutations are nothing more than what gardeners for centuries have > called sports. In the old days, with no knowledge of genetics and cell > division, this process must have seemed very mysterious. > > Somatic mutations are also the basis for my repeated assertion that the > elements which make up a clone are not necessarily genetically uniform. > > There are many ways of classifying the cells in an organism. One way is to > make the distinction between germinal cells (those which produce gametes, > reproductive cells) and the cells which make up most of the body of the > organism in question (somatic cells). > > In plants, somatic cells containing mutations might survive and continue > to > divide. Not only that, but if the plant in question is one being subjected > to intense asexual reproduction, there is always the possibility that > entities will result which contain only the mutated cells or a majority of > mutated cells. If the mutation in question is one which results in a > grossly > visible difference, then the gardener calls it a sport and treats it as a > new variety. > > On the other hand, when mutations occur in the germinal cells which > produce > gametes (eggs, sperm), the results are not likely to be visible in the > organism; however, because these cells produce gametes, such mutations can > be passed on to the progeny which result from sexual reproduction. > > That is why if you hybridize with plants whose distinctive characteristics > are the result of somatic mutations, any progeny which result will almost > certainly show the pre-somatic mutation characteristics. For instance, if > you cross parrot tulips with parrot tulips, chances are the resulting > progeny will be ordinary single tulips with not a parrot tulip among them. > > On the other hand, if you have a plant in which a mutation has occurred in > the germinal cells, there is a good chance that such a mutation will be > passed on to the progeny and, subject to the usual rules of genetic > expression, be apparent in such progeny. A simple example: plants which > typically produce red flowers often have yellow variants which are the > result of a relatively simple mutation in the germinal cells. If you cross > two such yellow flowered plants, chances are good that you will get plenty > of yellow flowered progeny rather than the typical red (assuming the > yellow > is a simple recessive to the red). > > That's it in a nutshell. For those who want more information, go to > Google. > > Jim McKenney > jimmckenney@jimmckenney.com > Montgomery County, Maryland, USA, USDA zone 7 > My Virtual Maryland Garden http://www.jimmckenney.com/ > > Webmaster Potomac Valley Chapter, NARGS > Editor PVC Bulletin http://www.pvcnargs.org/ > > Webmaster Potomac Lily Society http://www.potomaclilysociety.org/ > > > > > > > > > > > ------------------------------ > > Message: 13 > Date: Tue, 21 Nov 2006 17:29:09 -0500 > From: "John T Lonsdale" <john@johnlonsdale.net> > Subject: [pbs] FW: Clonal breakdown > To: "'Pacific Bulb Society'" <pbs@lists.ibiblio.org> > Message-ID: <00c201c70dbc$76e39eb0$6601a8c0@XPS400> > Content-Type: text/plain; charset=us-ascii > > When an organism or cell is propagated asexually for any period of time it > inevitably picks up somatic mutations. These are mutations in genes in > cells other than germline cells and they are not passed on by sexual > reproduction. These mutations may be silent (not obvious) or cause a > change in the phenotype (the organism looks or behaves differently). > Somatic mutations may cause cancer or variegation, for example. Many > cancers are the result of the acquisition of many somatic mutations, > each allowing the cell to escape from normal control mechanisms. I can > only assume that John Bryan's 'clonal breakdown' is the actually > accumulation of multiple somatic mutations that cause the desirable > features of a plant to be lost, or undesirable ones gained. 'Clonal > breakdown' cannot be fixed. In the case cited by JB he selected a > single individual from the population with desirable (or in reality > fewer undesirable) characteristics, put it into TC and propagated it > thereafter. It will still have carried forward all the somatic > mutations it had previously acquired, and would continue to acquire new > ones. > > Clonal drift is the same process as above. It is a problem in many > areas. For example human cells passaged in culture many times will > sooner rather than later start behaving differently to the cells that > were originally isolated. This has a big impact if those cultured cells > are to be used in research because they no longer are representative of > the cells that would be found in the body. > > Continued asexual reproduction, per se, does not cause a 'loss of > vigor', that is pure bunkum! > > It is wrong to think that all viruses cause leaf streaking - infection > can have many different symptoms or none at all that are visible. > Humans carry many viruses that are silent for some, most or all of the > time. > > One of the aging processes in cells other than stem cells is (as Boyce > said) a gradual shortening of the telomeres (the caps at the end of > chromosomes). Once they get past a certain point the cell detects this > and can become senescent or enters a pathway of programmed cell death > (apoptosis). In the devastating disease Progeria, which causes > premature aging in humans, the telomeres become prematurely shortened. > > Thanks, > > J. > > > > > ------------------------------ > > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://www.pacificbulbsociety.org/list.php > > > End of pbs Digest, Vol 46, Issue 26 > *********************************** > >