My purpose is to get a lycopene pink arilbred iris. The lycopene pink is recessive in tall bearded iris (autotetraploids) and in standard dwarf bearded iris (allotetradloids). The arilbreds are a different allotetaploid from the standard dwarf bearded, and no lycopene pinks exist in them.
My plan is to use arilbred pollen from arilbreds that have the lycopene gene in them from the tall bearded side of their ancestry. I'll irradiate the pollen with the light, then use it on the standeard dwarf bearded with lycopene. The mutations in the lycopene gene should give hybrids that show the lycopene color.
The arilbred x standard dwarf bearded F1 iris are sometimes partially fertile. This should get the mutation into the arilbred iris.
Any comments on this are welcome. Especially on how much and the type of ultraviolet light to use.
Walter

I've tried to us UV light to induce mutation in chrysanthemum, but didn't get much. I had callus growing in the dark (it was white without anthocyanin or chlorophyll because those things can help protect the cells from UV light). I then exposed the cultures for a few days and then regenerated plantlets and looked for mutants. I only found one red mutant from a purple clone out of over 1,000 regenerants. That UV source was a lamp used for looking at DNA in agarose stained with ethrydium bromide and the cultures were ~10 inches below it. Gamma radiation seems to hold more promise. I would like to do a similar thing as well to draw out recessives with other plants.

Good Luck,
Sincerely,
David

I dont know exact wavelengths you are looking for but I have an idea you might try if you are willing to experiment with time exposures.

Find someone with a UV sterilizer for ponds or water. Im sure one could be adapted.

I had an old UV hood I actually got from KSU's trash but threw it out when I moved to go to school at NCSU (I worked for Dr Clayberg too).

Sounds interesting what you are trying.

Good Luck
Keith

Dose rates on these sort of things tend to be rather species and genotype specific anyway, so it would seem the best bet might be to try differing doses on different batches of pollen. This may not be a workable solution if you're limited in the amount of pollen or flowers at your disposal, I guess.

I dug through the papers I had on hand on mutagenesis, but did find much on UV...it doesn't appear to be a particularly favored method, for whatever reason (it's somewhat less penetrative, for one thing). All I found as far as a optimum dosage was 125 J/m2 for apple and pear leaf explants in tissue culture. I don't know that that has much bearing for iris pollen, but it'd at least be a starting point.

Actually, I am going to try both pink autotetraploids and the pink allotetraploids, both pollinated with pollen from the arilbbred amphiploids. But in both cases, the seed parent is homozygous pink. In both cses, the F1 has very low fertility, but does sometimes set seeds or give fertile pollen. So both cases are the same from a breeding point of veiw. In fact, in the progeny of the autotetraploid tall bearded iris x ampliploid arilbred and the standard dwarf bearded amphiploid x arilbred amphiploid, the F2 progeny get complete genomes, so the backcross progeny will be the same regardless of pedigree.
I checked with iris breeders about which cross gives more seedlings and the percent fertility of the seedlings. None could give me numbers. So I decided to try both and keep count of the numbers for future reference.
One way the amphiploid vs. autoploid does make a difference is that the amphiploid is much earlier to bloom than the autoploid. This is because the speices used to get the amphiploid is extremely early.
Walter

I don't know if this will be useful to you, but Dr. Peter Werckmeister wrote in Iris colors and pigments, Bull. Amer. Iris Soc. no. 158: 25-33 (1960):

"Now I have found that it is easy to extract the yellow pigment with alcohol, but lycopin is insoluble in alcohol and is not removed. If then orange-colored beards are immersed in alcohol the yellow color is removed and they turn pink if they contain lycopin; if no lycopin is present they become white. Also, plants heterozygous for the tangerine gene, which appear among F2 progenies are of T1t3 genetic constitution, can be detected by this test. Thus such tests are important for the breeder or geneticist because in some irises with bright orange beards the color is due entirely to orange colored carotenoids."

He also wrote Lycopin and pink-breeding in The Iris Yearbook, the British Iris Society, p. 155-159 (1958), but I don't have that article.

Karl

I just think it's useful to remind the beginners who read these posts that "recessive" doesn't necessarily mean that a trait is not expressed at all. In many cases the recessive trait is present but masked. Tricks like using alcohol to remove alpha-carotene so the lycopene can be seen are very useful.

One time I crossed a purple rose (cyanin+co-pigment) with an orange (pelargonin). Pelargonin was present but masked because there was so much less of it and because the cyanin complex is so much darker in color.

There are other such tests, such as placing a flower over an ammonia solution. This is from W. J. C. Lawrence, The Genetics and Cytology of Dahlia Species. J Genetics, 1921:

(c) Reactions of anthocyanins and flavones with ammonia and SO2

As indicated on p. 128 the change of colour occurring when white, ivory or yellow petals are fumed with ammonia is as follows:

Petal colour---Changes to
White---No change
Ivory---Lemon yellow
Yellow--- Intense orange

The ammonia test is a well-known method used for detecting the presence of anthocyanin in plant tissues. If anthocyanin is present a green or bluish colour usually develops upon fuming, though possibly other substances in the cell sap may modify this green or bluish appearance. In addition to the many fumings made with ammonia in the course of these experiments, petals have been bleached with SO2, and the reactions of different flower colours with these two reagents noted.
The observations may be briefly summarised as follows:
SO2. SO2 does not affect the flavones. It half bleaches the deeper coloured petals and almost entirely bleaches tinged varieties. Penetration is increased if the petal is first fumed in ammonia and then bleached—complete removal of the anthocyanin pigments resulting, thus revealing the flavone ground.
Ammonia (a) Magenta and purple flowers give green and bluish-green reactions. (b) Orange and scarlet give an intense reddish-brown coloration. (c) Intermediate forms give intermediate reactions.
The intense reddish-brown which develops when orange or scarlet petals are fumed is of some interest, since this is not typical reaction of anthocyanin with ammonia.
All the other species I have grown conform, after their kind, to the above results.
=======

Pale ivory can look white, but the ammonia test reveals the difference. This, too, is an important consideration. "Modifiers" can influence the expressions of traits, even to the extent that "recessive" traits become dominant -- or vice versa.

I suppose you are aware of the chilling requirement of arilbred embryos. TB embryos lack this requirement. I don't know about DBs.

It is also interesting to note that some of the DB species have deep yellow flowers but lack carotenes. They are pigmented by chalcones. (I wish we had yellow chalcones in roses. Then we could have bright, non-fading yellow AND rich fragrance.) This raises the possibility of hybrids with both lycopene and chalcone -- maybe a bicolor with chalcone yellow standards and lycopene pink falls.

Even without mutations, genes can be swapped between genomes occasionally. That is, a Pumila gene may be transferred to a TB chromosome once in several hundred seedlings of tetraploid IBs. The same should happen, probably as rarely, in Arilbred varieties.

Karl

Much more rarely.
The I. pumila and the tall bearded iris are both in the eupogon sectiion.
The arils are in a seperate section. Or subsection, I forget. But they are farther from the tall bearded than the miniature dwarfs are.
Even so, yes, I think that rarely gene exchange would take place.
I don't need an exchange though. Either a deletion or an exchange would be fine with me, if it gives the result. And I believe either would.
Generally, an exchange where pairing is very low is induced by hard radiation. That breaks up the chromosomes and pieces can end up in the wrong chromosome. And pairing is generally reduced.
A deletion, or more accurately perhaps, an inactivation, by changing a base pair, is more likely facilitated by UV or chemically induced mutation. And fertility is generally reduced less than with hard radiation.
The more I study it, the more I like UV on pollen. Relatively safe to handle. No fumes, it doesn't go through shielding. Turn it off and it is off. I'm expecting point mutations, with minimum fertility problems.
I found a germicidal UV light for $180. And maybe one for $50. Both would require modification, but they are possible.
The biggest problem I now see is that the treated pollen will give lots of other mutations, including recessive lethals. I'll be backcrossing to non-treated aribreds to keep or regain vigor.
Walter

What I had in mind were translocations rather than exchanges or crossovers between homeologous chromosomes. This, apparently, is what happens when Pumila genes (or chromosome segments carrying the genes) are translocated to TB chromosomes.

The crossovers resulting in translocations are more likely to occur within heterochromatic regions, so the homology of chromosomes is not a factor. All heterochromatin is effectively "homologous", according to Prokofyeva-Belgovskaya, who observed "Mechanical weakness of their chromonemata, increasing the frequency of chromosomal rearrangement and crossing-over in them".

Certainly, hard radiation could fragment chromosomes resulting in rearrangements. However, what I described has been reported as occurring among seedlings untreated tetraploid IBs. I'm not discussing this as an alternative method, but as an alternative explanation.

Once you get the result you're after (I have my fingers crossed for you because I'd love to see a flamingo pink Arilbred) it would be interesting to observe the linkages, if any, to see whether you got a point mutation or a translocation.

Karl

Of course, a translocation of the "gene for yellow" (and linked genes) from the Aril chromosome to a TB chromosome would amount to a deletion since the extra "gene for yellow" would segregate out in some back crosses to a flamingo pink TB.

You startled me a bit when you mentioned that lycopene had been available in irises for 50 years. It can't be that long because I remember the early ones and ... Oh, right! I have been around that long.

My first flamingo pink was 'Happy Birthday', which was given to me by an iris breeder when I was about 4 years old. I still love the color.

Karl

It states good dosages are 5x10/5th,8x10/5th and 1x10/6th ergs/ cm2.

I have a Ray-tech versalume with an output of 4w but the manufactures can't tell me how far to place the pollen in order to get the dosage needed. I can't afford a radiometer.

This info may be too late but thought I would post.

Ira

Could someone translate the method used by that hobby-gardener to get those cool plants??