|
 
Welcome to the Shroomery Message Board! Please  login or  register to post messages and view our members-only content. You'll gain access to additional forums, encrypted messages, file attachments, board customizations, and much more!
|
 warriorsoul
 
Registered: 08/17/07
Posts: 796
Last seen: 41 minutes, 2 seconds
|
 Would this Work for Creating Hybrid Strains??
#8057340 - 02/22/08 04:54 PM (9 months, 7 days ago) |
|
|
Can i make a hybrid by mixing the spores of two different strains in water?
Edited by warriorsoul (02/22/08 05:44 PM)
|
 drkrobotnik
lurk moar.
Registered: 04/06/06
Posts: 3,939
Loc: tx
|
Re: Breeding Spores Question [Re: warriorsoul]
#8057389 - 02/22/08 05:04 PM (9 months, 7 days ago) |
|
|
--------------------
|
warriorsoul
Registered: 08/17/07
Posts: 796
Last seen: 41 minutes, 3 seconds
|
Re: Breeding Spores Question [Re: drkrobotnik]
#8057483 - 02/22/08 05:24 PM (9 months, 7 days ago) |
|
|
None of those threads answers my question.
|
RogerRabbit
Bans for Pleasure
Registered: 03/26/03
Posts: 18,223
Loc: USA Mountain Northwest
Last seen: 14 hours, 21 minutes
|
Re: Would this Work for Creating Hybrid Strains?? [Re: warriorsoul]
#8058527 - 02/22/08 09:42 PM (9 months, 7 days ago) |
|
|
Quote:
warriorsoul said:
Can i make a hybrid by mixing the spores of two different strains in water?
No. Different strains of the same species will often readily join, but such isn't a hybrid. Now, if you crossed two species, you'd have a hybrid.
RR
--------------------
www.mushroomvideos.com
"I wouldn't want to belong to any club that would have me as a member".
Mark Twain, Woody Allen, Groucho Marx, and anyone else who wishes to claim credit for the quote.
|
warriorsoul
Registered: 08/17/07
Posts: 796
Last seen: 41 minutes, 3 seconds
|
Re: Would this Work for Creating Hybrid Strains?? [Re: RogerRabbit]
#8059379 - 02/23/08 06:00 AM (9 months, 7 days ago) |
|
|
I wasnt talking about mixing species but strains rather.
Wouldnt it still be called a hybrid like pe6 or falbino or is there another word im looking for?
So if i mixed two spore prints from the same species together in water.Would some of the offspring be a cross of the two strains?
I dont see why the monokaryotic hyphae of two different strains wouldnt fuse.
Wouldnt it be the first compatible hyphae that the monokaryon comes in contact with?
Doesnt the system favour outbreeding?
Edited by warriorsoul (02/23/08 07:52 AM)
|
caricapapaya
Stranger
Registered: 04/10/06
Posts: 81
Last seen: 18 hours, 33 minutes
|
Re: Would this Work for Creating Hybrid Strains?? [Re: warriorsoul]
#8059800 - 02/23/08 10:34 AM (9 months, 6 days ago) |
|
|
With plants a hybrid is the offspring of 2 different strains.
usually it is referring to an F1 hybrid, which is the first generation of a cross between 2 pure breeding strains of the same species.
If you were to cross 2 species, you would have an interspecific hybrid, or 2 genera would be an intergeneric hybrid. Interspecific and intergeneric hybrids can be difficult to obtain, but not always.
Is the terminology the same for mushrooms?
That said, I think you would get some crossing, but identifying the crosses might be the tricky part depending on how different the parents are.
you should read workman's post about the 'White Penis' cross.
|
warriorsoul
Registered: 08/17/07
Posts: 796
Last seen: 41 minutes, 3 seconds
|
Re: Would this Work for Creating Hybrid Strains?? [Re: caricapapaya]
#8059822 - 02/23/08 10:42 AM (9 months, 6 days ago) |
|
|
Thanks.
Ive already read it.
I want to know if there is an easier way to make crosses when breeding for a certain phenotype.
Mixing the spores in water would be alot easier than isolating monokaryotic hyphae.
Edited by warriorsoul (02/23/08 01:05 PM)
|
Smushroom
Avid Learner
Registered: 02/02/05
Posts: 554
Last seen: 23 hours, 53 minutes
|
Re: Would this Work for Creating Hybrid Strains?? [Re: warriorsoul]
#8060452 - 02/23/08 01:27 PM (9 months, 6 days ago) |
|
|
You need to do a lot more reading if you want to create "hybrids". Mushroom genetics don't work in the same way as normal genetics.
The simple answer to your question like RR said, is no.
The long answer is way more complex than anyone here really wants to go into with you and it would be better if you just read until you figured it out yourself, but the simplified version is this:
Then you start from spores you will have millions of them germinate and grow. If you put spores from 2 strains together and allowed them to germinate you would have some that are Strain A, some that are Strain B, and some that are Strain AB. However you have to understand that the genetics of the Strain A mycelium will vary with every single germination. So if you inoculated a single jar with your "crossed" spores you would get a bunch of different colonies of mycelium growing in the same medium. Some would over power the others, some would grow alongside the others, and others would eventually be overpowered.
If you let that grow out and fruit you would have fruits with various genetics and wouldn't know which is which.
Now lets say you actually found a mushroom with genetics from both Strain A and Strain B. If you took a spore print from that and germinated those spores you would have the same genetics as last time, some A, some B, and some AB. So the cycle continues.
Eventually you would probably lose all AB mushrooms since they would not be as stable as the others.
If you truly want to create a "hybrid" strain you will have to do a lot of agar work and go through several generations to stabilize the genetics of it. You are looking at atleast 6 months worth of culture work to even get a strain that produces fruits 50% of the hybrid strain. You would need over a year of work to get something to yield 80% or more of a strain.
|
warriorsoul
Registered: 08/17/07
Posts: 796
Last seen: 41 minutes, 3 seconds
|
Re: Would this Work for Creating Hybrid Strains?? [Re: Smushroom]
#8061564 - 02/23/08 05:24 PM (9 months, 6 days ago) |
|
|
System prevents selfing, promotes outcrossing.
As long as the Afactors and B factors are different they mate.
Differences are based on alleles present at each of the A factor loci, and each of the B factor loci.
A(allele set 1)1
A(allele set2)2
B(alllele set1)1
B(allele set2)2
A1B1 mates with A2B2 succesfully. Dikaryon.
A1B1 mating with A2B1 might form clamps but not true clamps, no success.
A2B1 mates with A2B2 no clamps, no success.
Mating between a single strain 1/4 compatability.
Mating between two different strains, that share NO common parents, 100% compatable.
Mating between two strains that share a like A or B factor will result in 3/4 compatability.
If there is no common parent there should be over a 98% of mating. This doesn't apply to mixing Mycelium of different strains, though, of course. Only to different spores mating.
|
RogerRabbit
Bans for Pleasure
Registered: 03/26/03
Posts: 18,223
Loc: USA Mountain Northwest
Last seen: 14 hours, 21 minutes
|
Re: Would this Work for Creating Hybrid Strains?? [Re: warriorsoul]
#8062153 - 02/23/08 07:52 PM (9 months, 6 days ago) |
|
|
What constitutes a 'strain'? Certainly not the name some idiot put on the print. If someone picks a wild mushroom in one part of florida and gives it the name 'x' and someone else picks a mushroom in the next pasture and names it 'y' are they really two strains? 
The 'problem' with mixing the spores in water is if they cross or not cross, you won't be able to tell because in most cases there isn't a hill of beans difference between them and you'd have no basis to compare to even know if they crossed or not.
Monokaryons can cross with compatible monokaryons.
Dikaryons can cross with compatible dikaryons or monokaryons.
The above is how 'strains' avoid degeneration in nature. Spores from hundreds or even thousands of miles away can germinate and 'cross' with the local mycelium. Is such hybrids? No.
If a man from africa and a woman from texas have a baby, is it a hybrid? Of course not. If a monkey from africa and a woman from texas crossed, it would be a hybrid. Cross a cubensis with an oyster or shiitake and you have a hybrid.
RR
--------------------
www.mushroomvideos.com
"I wouldn't want to belong to any club that would have me as a member".
Mark Twain, Woody Allen, Groucho Marx, and anyone else who wishes to claim credit for the quote.
|
MycoAu
Registered: 07/18/07
Posts: 650
Last seen: 15 hours, 22 minutes
|
Re: Would this Work for Creating Hybrid Strains?? [Re: RogerRabbit]
#8062222 - 02/23/08 08:28 PM (9 months, 6 days ago) |
|
|
RR, so do you have any examples of fungal hybrids in the gourmet or medicinal mushrooms catagory (even some "commonly known" articles) in the past few years? I am interested in this type of experimentation if it is possible for the home grower to accomplish. How common is it for hybridization in Gourmet/medicinal mushies? In the wild? In the lab setting? (successes, that is)
Just curious if you could point me towards some "dumbed" down basic reading to get into this topic.
|
drkrobotnik
lurk moar.
Registered: 04/06/06
Posts: 3,939
Loc: tx
|
Re: Would this Work for Creating Hybrid Strains?? [Re: RogerRabbit]
#8062679 - 02/23/08 11:13 PM (9 months, 6 days ago) |
|
|
Quote:
RogerRabbit said:
If a man from africa and a woman from texas have a baby, is it a hybrid? Of course not. If a monkey from africa and a woman from texas crossed, it would be a hybrid. Cross a cubensis with an oyster or shiitake and you have a hybrid.
RR
what you tryin to say RR? 
--------------------
|
warriorsoul
Registered: 08/17/07
Posts: 796
Last seen: 41 minutes, 3 seconds
|
Re: Would this Work for Creating Hybrid Strains?? [Re: drkrobotnik]
#8063426 - 02/24/08 06:44 AM (9 months, 6 days ago) |
|
|
Im talking about breeding for unique genetic identifiers.
like breeding Albino with PE.
Wouldnt that be an intraspecies hybrid?
Doesnt the system favour outcrossing?
--------------------
Psilocybe baeocystis in the NorthEast
Psilocybe caerulipes
Edited by warriorsoul (02/24/08 10:25 AM)
|
ShivaMeme
Stranger thanFiction
Registered: 02/02/08
Posts: 11
Last seen: 7 months, 24 days
|
Re: Would this Work for Creating Hybrid Strains?? [Re: warriorsoul]
#8064844 - 02/24/08 03:00 PM (9 months, 5 days ago) |
|
|
Within species hybridization is well known in animal husbandry. Hybrid vigor is also well known. And yes when "strains" of humans mate, the resulting offspring are often or even usually faster stronger and smarter.
One study conducted with women rating the "attractiveness" of shirts they smelled revealed through blood testing that women find the most dissimilar immune systems in men to be the most attractive. IE promoting genetic diversity is a driving factor of evolution and many times combines the best of both worlds whereas stagnating genetics and inbreeding cause recessive traits to become dominant.
<soapbox>
If you believe all humans are born exactly the same then you must agree to allow a downs or other genetically mentally challenged adult to care for your child to prove it. Though they are far nicer, more selfless, loving and forgiving people than average they also have disadvantages. Just like all of us...
Everyone has strengths and weaknesses, advantages and disadvantages. Fear of inadequacy and hiding from glorious differences is the flip side but the same driving force as racism.
</soapbox>
--------------------
The curse of Genius is the constant scrutiny of lesser minds...
The curse of Stupidity is the constant delusion of Genius...
The curse of Insanity is the constant perception of scrutiny...
Keirsey Temperament: ENTP (Take it Here)
|
 lipa
Registered: 07/24/07
Posts: 604
Loc: Where it doesn't rain.
Last seen: 4 seconds
|
Re: Would this Work for Creating Hybrid Strains?? [Re: ShivaMeme]
#8068470 - 02/25/08 12:50 PM (9 months, 4 days ago) |
|
|
Please lets not get so into human genetics guy's. We should all know by now that in breeding mushrooms, there is no "sex". If man or animal could mate with mushrooms that would be fantastic and I would love to see it.
|
lipa
Registered: 07/24/07
Posts: 604
Loc: Where it doesn't rain.
Last seen: 4 seconds
|
Re: Would this Work for Creating Hybrid Strains?? [Re: warriorsoul]
#8068512 - 02/25/08 01:04 PM (9 months, 4 days ago) |
|
|
Quote:
warriorsoul said:
Thanks.
Ive already read it.
I want to know if there is an easier way to make crosses when breeding for a certain phenotype.
Mixing the spores in water would be alot easier than isolating monokaryotic hyphae.
What's the difference. You still have to isolate the monokaryotic tissue after they germinate.
I am just now getting into mating tissue and don't know much. so I can't give you much advice on the subject. I think you should just isolate for now and start crossing them and see what happens. Only then will you really understand " with a little help of the experienced" what it is all about. I personally think your jumping the gun on learning here. And I didn't mean that in a bad way.
Edited by lipa (02/25/08 02:43 PM)
|
fastfred
Registered: 05/17/04
Posts: 4,366
Loc: Dark side of the moon
|
Re: Would this Work for Creating Hybrid Strains?? [Re: lipa]
#8073161 - 02/26/08 03:48 PM (9 months, 3 days ago) |
|
|
> Mushroom genetics don't work in the same way as normal genetics.
LOL While there are differences in the sexual cycle, the molecular basis is still the same. The same Mendelian genetics apply.
I would have to disagree with RR on the strain aspect. It is simply scientific convention to name each sample collected from the wild as a separate strain. The designations strain or sub-strain just don't really have any firm meaning other than as a naming convention.
If I went to a field and collected several samples they would first be named as samples. If there were any morphological differences they would be named as separate strains. Samples collected from different locations or by different researchers would be named as separate strains. Strains are often later found to be the same and the nomenclature is revised.
As far as "hybrids" you can call things whatever you want for the most part. You could call them intra-species hybrids or inter-strain hybrids. Some might disagree with that nomenclature, but they would know exactly what you mean. Therefore it's a useful term.
Hybrids are generally considered to be between species, but species boundaries are usually defined by mating compatibility, so the terminology is certainly not the clearest.
Anyhow, your best bet for creating strain crosses is to dilute your spore solution to obtain only a couple spores per plate and then use the monokaryons obtained to create dikaryotic cultures. Workman also came up with a useful technique of colonizing some substrate with a monokaryon and then adding spores of the other strain to obtain a good percentage of crosses.
Other techniques would involve genetic markers. Using recessive traits you would need to take the crosses to the F2 generation to see them expressed. i.e. obtain spores from your crosses and then grow them out. Redboy, PE, and albino are all recessive I believe. I'm not really aware of any dominant markers.
Another techniques involves mutation, finding auxotrophs, then using nutritional complementation on minimal media to find verified crosses. Obviously this is beyond most people's capabilities and introduces deleterious mutations into your genetics that will take awhile to breed out, but if you're interested look up "filtration enrichment" + "auxotroph".
Workman's done a good job of coming up with a simple technique. Perhaps we should create a guide on ways to accomplish crosses since there seems to be so much interest in the topic. It might answer most of the basic questions and get some people involved in the more advanced aspects of mycology.
One book that might be useful is "Genetics and Breeding of Edible Mushrooms". It's quite technical and focuses way too much on the parasexual cycle and protoplast fusion, but there is some interesting info and examples of hybrids that have been created.
-FF
|
MycoAu
Registered: 07/18/07
Posts: 650
Last seen: 15 hours, 22 minutes
|
Re: Would this Work for Creating Hybrid Strains?? [Re: fastfred]
#8073201 - 02/26/08 04:03 PM (9 months, 3 days ago) |
|
|
I've considering purchasing that book, but as mentioned, it seems to be a little too complicated and expensive just to find out that I might not need that level of explanation. I'm interested in the information, as are several other members, I'm sure. It would definitely be appreciated if one or a couple of the "advanced" members could collaborate to create a user friendly approach to "hydrids" (or whatever term you decide to use).
|
fastfred
Registered: 05/17/04
Posts: 4,366
Loc: Dark side of the moon
|
Re: Would this Work for Creating Hybrid Strains?? [Re: MycoAu]
#8073329 - 02/26/08 04:39 PM (9 months, 3 days ago) |
|
|
I think that would be a good idea. I just don't really have the time myself to put much time into it.
I nominate.... Workman and RR!
I'd be happy to help out as much as I can. We might get more people with advanced breeding programs and fewer with "Can I just mix the spores?" questions.
-FF
|
warriorsoul
Registered: 08/17/07
Posts: 796
Last seen: 41 minutes, 3 seconds
|
Re: Would this Work for Creating Hybrid Strains?? [Re: fastfred]
#8076090 - 02/27/08 06:08 AM (9 months, 3 days ago) |
|
|
LOL.
Maybe if someone actually addresses my question..
System prevents selfing, promotes outcrossing.
As long as the Afactors and B factors are different they mate.
Differences are based on alleles present at each of the A factor loci, and each of the B factor loci.
A(allele set 1)1
A(allele set2)2
B(alllele set1)1
B(allele set2)2
A1B1 mates with A2B2 succesfully. Dikaryon.
A1B1 mating with A2B1 might form clamps but not true clamps, no success.
A2B1 mates with A2B2 no clamps, no success.
Mating between a single strain 1/4 compatability.
Mating between two different strains, that share NO common parents, 100% compatable.
Mating between two strains that share a like A or B factor will result in 3/4 compatability.
If there is no common parent there should be over a 98% of mating. This doesn't apply to mixing Mycelium of different strains, though, of course. Only to different spores mating.
why wouldnt some of the offspring be hybrids?
Edited by warriorsoul (02/27/08 06:21 AM)
|
doc34
Fungitarian
Registered: 02/14/04
Posts: 2,638
Loc: Myceliaville !!!
Last seen: 24 days, 12 hours
|
Re: Would this Work for Creating Hybrid Strains?? [Re: warriorsoul]
#8076540 - 02/27/08 09:57 AM (9 months, 2 days ago) |
|
|
Mushroom breeding!
Until about 1980, button mushrooms had been improved by selection: the discovery and preservation of mutants and of spore cultures that showed improvements relative to their parents.
Between 1970 and 1980 several laboratories learned techniques for cross-breeding two strains of A. bisporus to produce a hybrid strain. The first successful commercial hybrid strains were the Horst 'U1' and 'U3' strains, developed by Dr. Gerda Fritsche at the Proefstation voor de Champignoncultuur in The Netherlands. The U1 hybrid now forms the bloodstock of almost all commercial white button mushroom strains grown outside of Asia.
Dependence upon a single crop genotype is called 'monoculture'. It raises the risk that a large fraction of the global crop could be susceptible to a new or mutated pathogen. Serious pathogen outbreaks have affected the button mushroom crop previously: LaFrance virus disease in the 1960s, and aggressive Trichoderma harzianum strain types in the 1990s.
A basic goal of crop breeding is genetic diversification, to reduce and manage such risks. Further goals of mushroom breeding often include some or all of the following improvements:
Resistance to disease Bacterial blotch, mummy (Pseudomonas spp.)
Verticillium spp.
Trichoderma spp.
Mycogone sp.
LaFrance virus
Better utilization of substrate (compost) nutrients
Flavor
Appearance
Crop reliability
Profitability
Nutritional or health value
Breeding and diversification depend upon the availability of large numbers of genetically different individuals (= strains). Until recently, major culture collections held as few as 12 (or fewer) genetically distinct strains of A. bisporus. The Agaricus Resource Program is the first program designed to increase the amount of Agaricus germ plasm available to mushroom breeders worldwide.
In the early 1970's, California scientists first succeeded at splicing viral and bacterial DNAs in the test tube, heralding the birth of the recombinant DNA (rDNA) era, popularly known as genetic engineering, gene transfer technology, gene splicing, molecular biotechnology, and transgenics. This new biotechnology found immediate application in the production of pharmaceuticals, where synthesis by rDNA microbes provided a quantum leap in efficiency over the laborious extraction of miniscule amounts from other sources. Early on it was stated that "the uses of biotechnology are only limited by the human imagination." Today we are witnessing how this broad-based science is impacting virtually every sector of our society.
It was during the 1980's when the power and potential of the burgeoning discipline of genetic engineering was first brought to bear on the improvement of agricultural productivity. The discovery of techniques to transfer genes to the major agronomic crops, including corn, soybean, and wheat, from unrelated species provided breeders with new vistas for increasing the efficiency of food crop production. Remarkable progress, far exceeding early predictions, has been made during the last two decades in breeding plants with new traits such as insect, viral, and fungal resistance, herbicide, stress, and cold tolerance, delayed senescence, improved nutritional features, and others. The global demand for transgenic crops is projected to be a $25 billion market by the year 2010. The growth of this industry will be propelled, in part, by "Golden" rice, which was engineered using a daffodil gene to be rich in beta carotene and thereby the promising answer to the vitamin A deficiency problem pervading the developing world.
Despite concern for the unforeseeable health and environmental risks posed by genetically-modified (GM) crops, gene transfer technology has irreversibly revolutionized plant breeding. Today, more than 100 plant species have been modified by gene splicing for improved sources of food, fiber, or ornamentation. More than 50 new crop varieties have cleared all federal regulatory requirements and stand approved for commercial retail. Because field testing is an essential step in the commercialization process, the number of permits issued by the U. S. Department of Agriculture, Animal and Plant Health and Inspection Service (APHIS) for GM crops provides a measure of the interest in transgenic breeding. During a 16-year period, more than 8,000 permits and notifications (fast-track permits) were issued, rising from a low of 9 in 1987 to a high of 1,120 in 2001 (Fig. 1). For the first three months of 2002, 536 permits/notifications were recorded by APHIS with 49% involving insect resistance, 33% herbicide tolerance, 7% each for product quality and agronomic properties, and with the balance comprising fungal and viral resistance and other traits. Thus, the "genie out of the bottle" scenario describes the status of agricultural genetic engineering. Despite the anti-GM sentiment expressed by a vocal minority, the potency of the new biotechnology for problem solving has been realized to an extent that is far too compelling for it to be disregarded.
Genetically Engineering the Button Mushroom
For almost as long as scientists have been introducing genes into crop plants using molecular biotechnology, others have attempted with limited success at developing a gene transfer method for Agaricus bisporus. A major breakthrough came in 1995 with the surprising discovery that the bacterial workhorse, Agrobacterium tumefaciens, used to shuttle genes into plants, also operated with yeast fungi. Shortly thereafter, this method was extended to filamentous fungi, including A. bisporus.
Agrobacterium is a common soil bacterium with a worldwide distribution. It causes a disease known as crown gall on hundreds of woody and herbaceous plant species, but most commonly pome and stone fruits, brambles, and grapes. In its normal life cycle, the bacterium transfers a tiny bit of its DNA into the plant DNA resulting in the formation of galls. These galls serve as food factories for the mass production of the bacterium. Over the years, scientists learned how to develop disarmed strains of the bacterium that were incapable of inducing galls, but retained the ability to transfer DNA. In essence, a natural biological process was harnessed to create a bacterial delivery system for moving genes into plants, and now fungi.
Though Agrobacterium was shown to be highly promiscuous in shuttling genes into a spectrum of plant and fungal species, the method was still too inefficient to be applied to the breeding of A. bisporus. More recently, we devised a convenient and effective Agrobacterium-mediated 'fruiting body' gene transfer method holding the promise of a powerful tool for the genetic improvement of the mushroom. In our experiments, a small ring of DNA carrying a gene for resistance to the antibiotic, hygromycin, was transferred to a disarmed strain of the Agrobacterium. The antibiotic resistance gene is referred to as a selectable marker, because mushroom cells receiving this gene from the bacterium become marked by the resistance trait and can be selected based on the ability to grow on a hygromycin-amended medium. The end result is a mushroom strain having the newly acquired characteristic of hygromycin resistance. Such a strain has little commercial value, but rather the resistance trait was a research tool that allowed us to easily determine if the bacterium had transferred the gene to the mushroom, and exactly how efficiently it did so under different experimental conditions. Today, and more so in the future, this gene is being replaced or complemented by genes that will confer commercially relevant traits.
Figure 2 highlights the steps in the 'fruiting body' gene transfer method. In this procedure, gill tissue is taken from mushrooms approaching maturity, but with the veil intact, so as to ensure some degree of sterility. Next, the tissue is cut into small pieces and vacuum-infiltrated with a suspension of Agrobacterium carrying the antibiotic resistance gene. In a process referred to as co-cultivation, the gill tissue and bacterium are grown together in the laboratory for several days, during which time the bacterium transfers the resistance gene to the mushroom DNA. Because not all mushroom cells receive a copy of the gene, those that have can be distinguished from those that have not by the ability to grow on the antibiotic medium. After 7 days on the medium, mycelium of A. bisporus appears growing at the edges of some of the gill tissue pieces. After 28 days, upwards of 95% of the tissue pieces will have regenerated into visible cultures. At this point, the GM cultures can be transferred to a standard growth medium, and used to prepare grain spawn in the ordinary manner.
Figure 3 depicts the first of two cropping trials carried out at the Penn State Mushroom Research Center involving GM mushroom lines. In these trials, all six antibiotic-resistant GM lines mirrored the parental commercial hybrid strain in colonizing the compost and casing layer. Further, the GM lines produced mushrooms having a normal appearance and, in some cases, yielded on a par with the commercial strain (Table 1). Expression of the resistance trait in the mushrooms could be easily demonstrated by placing pieces of the cap or stem tissue on the antibiotic medium and observing for growth (Figure 4). These experiments were crucial, because the results established for the first time that a foreign gene could be introduced into A. bisporus without having a detrimental effect on its vegetative and reproductive characteristics.
Table 1. Productivity of genetically-modified (GM) mushroom lines expressing the antibiotic resistance gene that were derived from a commercial off-white hybrid strain.
Yield (lbs./sq. ft.)
Line Trial I Trial II
Commercial hybrid 3.00 a 3.68 a
GM-1 2.08 d 0.86 d
GM-2 1.73 d 1.45 d
GM-3 2.52 bc 2.70 c
GM-4 2.12 cd 2.99 bc
GM-5 2.90 a 3.63 a
GM-6 2.86 ab 3.59 a
Means within a column having the same letter are not significantly different according to the Waller-Duncan K-ratio t test at P<0.0001
Impact of Transgenic Breeding on Mushroom Cultivation
The overwhelming popularity of the hybrid mushroom strains introduced in the 1980's has created a near global monoculture that is precarious from the standpoint of disease and pest susceptibility, and has limited the choice of production characteristics and the range of tolerance to environmental and cultural stresses. During the last two decades, no notable advances have been made in breeding strains with strikingly improved features. This is due largely to the cumbersome genetics of A. bisporus and a shortage of commercially desirable traits. There is movement afoot in using traditional breeding to explore wild isolates of A. bisporus as a source of new traits. Though this represents an important step towards expanding the genetic base of cultivated A. bisporus, it is not yet clear which traits exist in the wild germplasm collection, and if they can be successfully bred into commercial strains.
The advent of a facile gene transfer technique for A. bisporus enables the exploration of genetic solutions to problems confronting the mushroom industry in a realm never before imagined. The awesome power of transgenics lies in what is known as the universality of the genetic code. The biochemical alphabet consisting of the letters G, A, T, and C that spells the DNA sequences of genes controlling traits is identical for all organisms. A scientist blindly handed a gene would have difficulty determining if its source was a mushroom, mouse, or man. It is this unifying feature of genes from all walks of life that makes transgenics so potentially powerful, while it is the tools of molecular biology that unleashes this power so this potential can be realized. Simply stated, the new biotechnology permits the exchange of genetic information between organisms outside the confines of the natural breeding barrier. No longer is the genetic improvement of the mushroom decided by the question of sexual compatibility or traits found within the species.
At another level, gene transfer technology will vastly accelerate our understanding of the molecular mechanisms underlying commercially relevant characteristics. It also will serve to strengthen the muscle of our industry's scientific arm, growing from a handful of mushroom researchers to the global workforce of molecular biologists. As one hypothetical illustration, the quest to breed robust resistance to dry bubble disease would not be restricted to a few scientists searching within A. bisporus, where it may or not exist. Instead, it would extend to scores of scientists working on unrelated organisms who have discovered resistance genes to other Verticillium species. Importing these genes to the mushroom for an evaluation against dry bubble is now possible. As farfetched as this may seem, it is precisely this trans-species approach that has met with commercial success. Genetic manipulations of this sort have been carried out on crop plants and include, importing cry genes from the Bacillus thuringiensis bacterium for insect resistance, a synthetase gene from Agrobacterium for glyphosate herbicide resistance, the nitrilase gene from the Klebsiella pneumoniae bacterium for bromoxymil herbicide resistance, a hydrolase gene from the Escherichia coli bacterium for modified fruit ripening, the barnase gene from Bacillus spp. for male sterility, and viral genes for virus disease resistance.
It cannot be overstated that gene transfer technology is not a panacea whose arrival marks the departure of traditional breeding. Quite the contrary, it is a new tool at the disposal of the breeder that will complement existing techniques, while offering a far broader range of options for successfully affecting genetic solutions to problems. Gene splicing will expedite the breeding process, transferring much of the time in development from the field to the laboratory. It will enable the introduction of genes with a surgical precision and from exotic sources, which otherwise would be unattainable by more conventional methods. It is important to recognize, however, that in the end, the forces of nature overcoming a trait (e.g., the breakdown of insect resistance) would act with the same intensity on the controlling gene whether introduced by traditional or transgenic breeding.
The melding of gene transfer methods with traditional techniques in a mushroom breeding program may take several forms initially, only to be continually refined, streamlined, and improved for higher efficiency and greater effectiveness. Many transgenic manipulations with A. bisporus will require the transfer of the gene to both parental lines so that their offspring mimic the natural inheritance process by carrying a duplicate copy of the gene. For other applications, introducing a single copy of the gene may achieve the desired effect. In either case, the resulting GM lines may require further selection before emerging as worthy commercial strains.
The Perils of Genetic Engineering
If the decision to exploit genetic engineering for agricultural improvement was left to scientists, the cultivation of GM crops would probably be far more widespread and diverse than it is today. But science does not occur in a vacuum. Political forces reflecting the pendulum of public opinion have a strong bearing on the direction and timetable of scientific progress. The early comment that, "the uses of biotechnology are only limited by the human imagination" was used within the context of its seemingly boundless benefit to humanity. In actuality, human imagination has limited biotechnology. That food crops created by genetic engineering are unnatural to the extreme of threatening human health and the delicate balance of the environment is a perception held by a segment of our society. Whether or not these fears are rationale is irrelevant, because their mere existence has hampered the growth of genetic engineering in agriculture. As with many new technologies, the question of acceptance by society will be answered through a distillation of the benefits to be derived for the risks that must be taken.
Both transgenic and conventional plant breeding strive to increase yield, improve quality, and reduce production cost. However, the two breeding strategies differ enormously in the manner in which the end is achieved. For many, it is the process of genetic engineering and not the final product that is most disconcerting. Removing the element of compatible sexual crosses from breeding and reducing it to the splicing of genes in the laboratory seems highly unnatural, constituting extreme human intervention. True, only transgenic breeding allows genes from exotic sources to be brought together in unique combinations. This has been criticized for the possibility of creating new and unpredictable food-borne allergies and toxicities. But the conclusions drawn by the American Medical Association, Board on Agriculture and Natural Resources and National Research Council, and Institute of Food Technologists, among other organi | |
|
|
Previous
Index
Next
Threaded
Edit 
Reply 
Quote 
