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Discussion on Origin of Sports...Summary Conclusions re Rule of Thumb(Zonneveld)


 Discussion on Origin of Sports...Summary Conclusions re Rule of Thumb
> Theory (Zonneveld)
>
> A major discussion  on Origin of Sports occurred on hosta-open during
> a four week period beginning Feb. 24, 2001. The issues identified at
> the beginning of the discussion were:
>    -What are the major causes of sports?
>    -What are the less important or less frequent cause of sports?
> The discussion centered on an examination of three articles written in

> the AHJ since 1996. They included:
>      1. Ben Zonneveld, Mutations , Recombinations, Sports and
> Chimaerae, AHJ  Vol.27,No.1.
>      2. Ben Zonneveld, Rule of Thumb for Sports in Hostas,AHJ Vol.28,
> No.1
>      3. Ben Zonneveld, When Are Independently Arisen Look-alike Sports

> Identical Rather Than Only Similar? AHJ Vol.30, No.1
>
> All members of hosta-open was invited to participate to the extent
> they wished. In addition other articles written by Dr. Kevin Vaughn,
> USDA, Dr. Michael Marcotrigiano of Smith College, MA, and Dr.
> Lineberger, Texas A&M were discussed and summarized. A review of the
> literature on the subject of chimeras and miscellaneous related
> articles were located on the Internet, studied and commented on.
>
> Comments of participants centered on three processes identified by
> Zonneveld as causal factors for deviations to occur which are
> responsible for sports. Also other processes identified by other
> workers, but not by Zonneveld,  were described in detail. A summary of

> these causal factors and their relative importance are provided in
> this summary. They represent the concensus opinions of Jim Hawes, Bill

> Meyer and Dr. Joe Halinar, the principal participants who opposed the
> views presented by Zonneveld in his articles and in his email
> comments. The three factors identified by Zonneveld were:
>
>      1. Mitotic Recombination ( or somatic crossing-over of
> chromosomes). While Zonneveld claimed this process as an important
causal
factor
> in all three of his article and his Rule of Thumb, no research
> evidence was presented to show that this process caused, initiated or
> was responsible in any way for the occurence of variegation in hostas.

> There was no literature review to indicate work of any other
> researchers in this area to prove any incidences of sports being
> caused by this process.  Zonneveld was asked repeatedly to prove his
> theory but he was unable or unwilling to provide any proof, examples,
> descriptions or any other evidence of this process as a causal factor
> for hosta sports as claimed.  While mitotic recombination CAN
> theoretically occur, or MAY occur in rare incidences in the plant
> kingdom, there was no proof submitted that it had actually ever
> occurred in hostas. Five incidences of "twin spots" were mentioned,
none
of which subsequently became stable periclinal chimeras.Therefore the
claim
that it is responsible for
> green edges on yellow hosta leaves or for changes from blue forms to
> green forms in hostas is a highly questionable claim. Zonneveld
> finally admitted, when asked several times about this, that it was a
> "guess" based upon his knowledge (but not his experience) as a
> geneticist.  Because mitotic recombination was ranked first as a
primary
cause for chimeras in Hosta, the entire Rule of Thumb must be questioned
as
to validity. . It is therefore considerd by this sub-panel
to be a purely theoretical exercise, and as such, a poor choice as an
accurate guide to better understanding of the origin of sports.
>
>      2.Chimeral Rearrangement (better known as tissue transfer or
> exchange). This process was identified by Zonneveld as being
> responsible for deviations to occur resulting in chimeras. He
> stated that  there is an exchange of cells in a meristem from one
> layer to another. While this process does occur, it is not a primary
> "cause" per se of a chimera.
>
> This process may modify the form of a chimera once a chimera becomes
> established. The obvious conclusion made is that this factor, while
> not being causal for chimeras, may be a modifier which could  be a
> valid process along with others which may be determined to be valid
> within this summary.
>
>       3. Nuclear Mutations. Zonneveld defined nucler mutation as a
> change in the DNA in a plant that can be transmitted through its
> offspring. He said  it was a rare occurrence (as was back mutation) in

> the magnitude of 1 to 100,000. An assessment of the relative
> importance that Zonneveld gave to nuclear mutation as a causal factor
> for sports in hostas created a rather paradoxical situation. Because
he
rates
> it such a rarely occurring process, Zonneveld seemed to attribute
> little weight to the relative importance of nuclear mutation with his
> Rule of Thumb list of  important causal factors. At the same time, it
was
> necessary for him to place exceptional importance on it as one of the
three primary
> causes of chimeras. Why so?  Because he does not recognise chloroplast

mutations as having any consequence as a causal factor, and indeed does
not
even mention them, so there must be at least one factor within his Rule
of
Thumb which is of sufficient importance to explain the large number of
sports which occur in hostas.  The only mention he made of plastids were

> chlorophyll losses or inactivations. He states that in tissue
> culture, chloroplasts are lost or inactivated in the outer layer (of
> leaves) leading to a whitish edge. He explained this might have to do
> with the fact that sometimes meristems are started from flower buds.
> (Note: This is histological nonsense as well as tissue culture
> protocol nonsense).  Thus, from assessing statements made in the
articles
in which he puts forth his theory, the most logical conclusion to be
arrived
at by this sub-panel is that nuclear mutation, as one of the three
significant causes of variegation put forth in his Rule of Thumb,
is over-emphasized far beyond its actual importance. It is also noted
that
plastid mutations and related processes are completely ignored, despite
their importance in the work of those who have done research in plant
variegation.
> An explanation of the true factors of importance are expected to  be
> covered in another summary.
>
> This leads to the conclusion that the Rule of Thumb guideline
> theory, which is an integral part of all three articles, is almost
completely at variance with all known research in plant variegation in
general, not just that done in Hosta.  The three articles and their
contents
are  not factually
> sound, are not in harmony with conclusions expounded by recognized
> authorities working in this same area of histology, cytology,
> embryology and cellular biology.  Zonneveld's theories fundamentally
> conflict with work of recognized scientist in this field, including
> Marcotriogiano, Dermen, Stewart, Tilney-Bassett, Vaughn and others.
> This sub-panel assessment finds that the three causal factors are
unsupported by evidence or even well-propounded, plausible theory.
Because
of many
> errors of commission, admitted "guesses" as to causes, a poor balance
> of causal factors, the use of poor or incorrect examples, weak and
incomplete explanations, and flagrant omission of the recognised causes
of
> chimeras, the Rule of Thumb must be considered fundamentally
> flawed and thus worthless as an introduction into the causes of
variegation. It cannot be
> justified on a sound, scientific basis.  Because of the weakness of
> the use of scientific method, the lack of a literature review to
> discuss the work of others, the lack of any convincing research data
to
> substantiate the contents and the lack of a sound basis of
> understanding of origins of sports, we recommend publishing of our
> findings described herein to represent "erratta" to provide
> corrections to mistakes made in these three articles. It is also
recommended that the theory represented as a "Rule of Thumb" be clearly
identified as a radical and unsupported work of theory, and not, as the
name
would suggest, a brief overview of contemporary knowledge in this area.
>
> As a sub-panel, we are aware that many issues still remain unresolved,

> requiring continued study and investigation.  We have all learned new
> facts and have perhaps changed our minds on the relative importance of

> causal factors of hosta sports.  We learned of processes which occur
> in hostas and other genera which determine how sports originate and
> develop into the various forms that we observe. We have learned that
> the existence of a process in plants is not proof that the process is
> in operation. Perhaps most of all, we have leared how much more we
have to
learn. Continued investigations are necessay for a better understanding
of
the sports that occur, for much is still a mystery to be unravelled by
true
scientific research.
>
> Appreciation is expressed for the participation of many individuals
> who helped in many ways and for their encouragement for efforts made.
> It was truly revealing how much interest there was in the subject of
> trying to understand hosta sports a little better than in the past.
Thanks
to
> all.
>
> Jim Hawes
> Dr. Joe Halinar
> Bill Meyer
>
>
>
>



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