I have a couple very basic question-- what causes the variegated foilage in citrus?

Are seeds of variegated citrus "true to type"?

Skeet

We found this related query below in another online Citrus forum.

I have a couple very basic question about variegated citrus-- what
causes the variegated foilage in citrus? (I am not talking about the
disease CVC or citrus variegated chlorosis)

Are seeds of variegated citrus "true to type"?

Applying conventional theory and in practice, in more cases than not, no,
the variegated Citrus are not true to type. Although some forms can be
true to type. Right offhand, I think the Variegated Pink Lemon is closer
to being true to type as when we graft or bud scions from this plant onto
a green non variegated rootstock we still get mostly variegated offspring.

Can new variegated varieties arise from a seed?

With Camellias the answer is yes. New variegated varieties can come from
seed but in most cases both parents had to have been variegated or the seed
parent was variegated and the pollen parent was either variegated or has the
virus that causes leaf variegation in its genome. The reverse can also be true
that a variegated pollen parent and a non variegated seed parent can also yield
a variegated offspring but the frequency in which we will see variegated seedlings
goes up if the seed parent in this case also has some variegation genes in its
genome. I did not make up these which does not always hold true in practice.
This is just standard theory with limited terminology used by me,.

I have read that they are chimeras and can originate from grafting-- is that true?

I think as a result of a chimera is the better word for it. What we determined
with our trials on a few plants is that the notion that the "yellow" virus that causes
variegation in a small variety of plants that was passed onto a new put together
offspring from grafting and budding did not automatically be introduced into
the genome of the offspring but the offspring could "carry" the variegation gene
for breeding purposes. Once the theorizing was over with that the "yellow" virus
was isolated and identified and later universally confirmed for the naysayers,
then people started to get nervous that the virus from a rootstock parent would
automatically be introduced into the scion upon the union of the two woods.
We found that this did not always happen. In most cases it did not happen which
led to our conclusion, right or wrong mind you, since not too many others have
tried to work with this phenomenon, is that the virus can be introduced into the
scion plant through propagation but in more times the virus does not show up as
being visible in the phenotype of the new plant. The worse fear of some people
in Camellias was that variegated rootstock would ruin the non variegated scion
plant. We found this notion with Camellias, Maples, Pines and Dogwoods to be
unfounded as more scion plants were left unaffected by the introduction of a
variegated rootstock parent upon propagation than the number of plants that
became enhanced or changed by showing some variegation in a previously
non variegated plant.

Now, the people that have worked with Citrus can tell their story and add to
the above.

A chimera does not always produce a variegation. Many times in Citrus a
chimera does not produce a variegation that we can see in the leaves and
the fruit. The term chimera has been broadened to include put together
plants such as budded and grafted forms. There we have two parents at
“play” for us. In a puritanical sense the term chimera should be used only
for pure line or newly developed plants such as a hybrid seedling, a plant
that came about from a rooted cutting or from layering or as seedling that
arose from the rooted cutting parent or the layered parent plant that went
to seed and produced a seedling that was different than either parent. In
more cases we would call this "new and different" individual a hybrid,
even if the parent plant was selfed.

The term chimera may be better applied for a plant that has undergone
a visible change such as a non variegated plant producing a branch that
may have some variegated leaves or a non variegated plant that produced
variegation in the rind of a fruit or a change in the overall shape of the fruit
in some cases. We are more likely now to see a change in the plant more
so today than in years past due to our continued propagation techniques
used on Citrus. We do not have too many pure line plants any more. Now
we have mutants and hybrids that have become form selections from two
parent put together offspring plants. We can have a King x Dancy hybrid
seedling and a Dancy x King seedling plant wood to work with but we
seldom try to keep the new pure line plant pure when we graft the hybrid
scion on another Citrus form rootstock such as a Troyer Citrange. Had
we taken rooted cuttings from the original hybrid plants rather than
introducing a hybrid rootstock that also may not be pure, we in effect
introduce a genetically “dirty” parent into the equation if the Troyer also
was not from a pure line.

We know that cytoplasmic DNA can move from the scion into the rootstock
and we also know that the rootstocks cytoplasmic DNA can move up into
and merge with the scion’s DNA . It was our feeling that when the two
foreign DNA merge to become one DNA that a chimera was more likely
to be seen somewhere in the plant but it can take many years for us to see
it. The so-called chimera itself can be just a change in the leaf shape in
Maples giving us the feeling that the rootstock had indeed influenced the
scion cultivar. We know over time and from continued grafting of red
and green form Japanese Maple cultivars that the rootstock has affected
the genome of the cultivar of which a palmate leafed cultivar can have
leaves that become more deeply divided over time or that a deeply divided
cultivar can start throwing out a series of palmate shaped leaves when in
years past all of the leaves were the same from the deeply divided cultivar
which never produced a palmate leaf. The change in the plant from our
estimation has come about from continued grafting of the cultivar, thus
introducing more foreign DNA into the cultivar thus affecting the purity
of the old Maple and we are seeing more and more of this type of change
in the offspring in our newly put together plants. What I am saying is that
that today’s Burgundy Lace and the old stock plant we have that came about
from rooted cuttings are not the same plant in appearance any more. Proof
positive that we have contaminated the old Maple with continued grafting
over the span of the last 40 years. We are seeing more change in the scions
today at a more steady and to a purist at an alarming rate than we did in the
last 25 years when this cultivar was in its infancy for being propagated by
grafting as opposed to being propagated for years previous by rooted cuttings.

How do I apply the above rationale to Citrus? Real simple, I bet my old in
ground transplant since 1965 Meyer Lemon that came to us as a rooted cutting
is a better plant and produces a better quality fruit than the old Meyer Lemon
form is that any of you can buy today. The old-timers that have been around
Citrus for a long while and know this Lemon will know exactly what I mean.

Thank you mr.shep for your thoughts in this post.

Snickles

Thanks Snickles for the reply. I had searched the web for info on the , but so much of the information on citrus is related to the CVC problem. I had thought that a virus might be involved.

One reason I asked is that I have a small seedling with only one true leaf so far that looks like it might be variegated. It is one that has lost any identification tags so I do not know if it is from a key lime, orange or tangerine-- all of which I have planted recently.

Just thinking out loud, but if this seedling is variegated, could it have originated like a chimera between an albino embryo and a normal embryo?

Skeet

You may be interested in looking at my website page about
variegated Poncirus seedlings
http://www.homecitrusgrowers.co.uk/poncirustrifoliata/variegatedseedlings.html
I can update this by saying all the surviving 'variegated' seedlings seem to have reverted to normal green leaves.
Mike.

Very interesting Mike,
The one seedling I have has a cream colored streak through the leaf, but when I look at it with 20 X magnification it looks like a streak of foam on top of the leaf.

Have all of your seedlings reverted to green?

Skeet

I was just reading about a Variegated Banana and the grower says they need to have low pH in the 4.5- 5.5 or they will revert back to green.
So maybe this goes for the Citrus too.

So, when I get an eye and t-bud it to another rootstock, the new tree will not be variegated, did I get it right?

If the bud you took was from a variegated citrus it will most likely produce a variegated sprout. There is the chance it will revert back to green...

Skeeter ask the question.........."What Causes Varigated Foliage?" I answered Skeet's question on another forum, but I will also answer it here.


Skeeter asks the question....." what causes the variegated foliage".......

Plastids which are in the tree's leaf contain genes that contribute to the development of the chloroplasts (the green color in leaves). These genes are passed from generation to generation by duplication and division of the plastids (their inheritance is distinct from that of nuclear genes). Since egg cells contribute plastids to the zygote while pollen cells usually do not, only the maternal parent has a part to play in plastid inheritance. Effects on the chloroplast genes are especially noted in the inheritance of variegated color patterns in the leaves of the tree. Here the egg cell contains both normal plastids and plastids that cannot develop into green chloroplasts because of defective genes. Some cells in the embryo have only the defective plastids. These cells divide further to produce the distinctive white or yellow patches on the leaves and stem of a variegated tree. - Millet

My first observation on variegated seedlings was, the ratio of them in flying dragon seedlings is really high, almost 40%.I wrote it in Removal of Growth With No Chlorophyll topic.

Here is my second observation, I wonder if you have observed the same thing;

Tap roots of albino seedlings grow faster than normal seedlings.I removed same amount of seedlings from the tray, half of them were albino.I noticed their tap roots are longer than normal seedlings.

What do you think, was it just coincidence?

A mutation of the chlorophyll synthesis in the germinal cells gives albinos (full or partial) that could transmit true to type by seed but they usually die.

The apical meristem is made of three layers of cells that reproduce (usually) separately. Depending of its origin layer a cell will differentiate in different tissue of the plant. If a mutation of the chlorophyll synthesis occurs in one of the "mother cell" of one of the three layers a variegated sprout appears.
Depending on the layer where occurred the mutation different types of variegation append. One layer gives the hedge of the leaves, an other the center, and the last the "inside".

As a mother cell of one layer can easily give a mother cell to an other layer, the variegated meristem can easily revert as non-variegated.
Indeed, as a seed is made of one cell, variegation cannot be transmitted by seed.

If you want to read about it, but in a good English:
http://lib.ucr.edu/agnic/webber/Vol2/Chapter2_5.htm#chimeras
Starting from "Autogenous Chimeras". But the whole chapter is worth to be read.

And there: http://www.lapshin.org/cultivar/N36/pogany-e.htm

And: http://www.lapshin.org/cultivar/N36/lineberger-e.htm

From my experience seeds from a variegated fruit will produce about 80-90% albino seedlings which die rather quickly.