Showing posts with label fertile family. Show all posts
Showing posts with label fertile family. Show all posts

Monday, September 14, 2020

Progress with Arilpums

by Tom Waters

When I wrote my previous blog post on arilpums early in 2019, I had to focus mostly on history and theory, as I did not yet have much to show from my own seedlings. That has now changed, and the current state of this project is even better than I had dared hope.

As explained in the previous post, arilpums are arilbreds dwarfs that come from crossing pure arils with the dwarf bearded species Iris pumila. If the aril parent is a tetraploid, theory says the resulting arilpums should be fertile amphidiploids, a sort of arilbred analog of the SDBs. They thus have the potential of ushering in a whole new "fertile family" of miniature arilbreds.

Waters Q025-01

This spring, I bloomed two arilpum seedlings, both prolific two-year-old clumps covered in bloom. The first, Q025-01, from 'Merlin's Magic' (a selection of Iris stolonifera) x P002-05, a pumila seedling of Armenian origin, has a dainty Regelia look and some nice veining. The second seedling, Q053-01, from 'Tadzhiki Bandit' x 'Sudden Butterflies' is larger and huskier, with flowers reminiscent of tall arilbreds with Regelia ancestry, such as 'Stars Over Chicago' or 'Saffron Charm'.

I also had good bloom this year on an arilpum seedling from

Waters Q053-01

George Hildenbrandt, GH-11-4-2, from 'Dunshanbe' x 'Hidden Dragon'. This is a charming dark arilpum with nice aril-like flower form.

Hildenbrandt GH-11-4-2

The remarkable thing is that all three of these seedling produced seed for me this year when crossed with other arilpums. In my previous post, I mentioned that earlier hybridizers working with arilpums had found them to be infertile as pod parents. That is clearly (and thankfully!) not a general rule! Here are my successful arilpum x arilpum crosses this year:

Q053-01 x Aladdin's Gem gave 38 seeds
Q025-01 x Q053-01 gave 9 seeds
GH-11-4-2 x Q053-01 gave 23 seeds
GH-11-4-2 x Aladdin's Gem gave 3 seeds

These are not huge seed yields, but they are certainly adequate for continued breeding. I am quite optimistic that a number of the second-generation seedlings from these crosses will be fully fertile, and it will be possible to line breed arilpums without having to constantly go back to the difficult aril x pumila initial cross. This will also open up arilpum breeding for hybridizers who live in areas where either arils or pumila are difficult to grow.

Next spring should offer even more excitement, as I have more than 30 arilpum seedlings from various crosses that will be blooming as two-year-old plants. I got a sneak preview of one this spring,  Q066-08, from 'Tadzhiki Bandit' x P018-02, a pumila seedling originating from the Caucasus mountains. It looks for all the world like a miniature rendition of its aril pod parent, giving a rather more "onco" impression than others mentioned in this post. It has not yet been tested for fertility.

Waters Q066-08

All this has been an exciting vindication of a breeding project motivated mostly by theoretic possibilities rather than concrete experience. I'm now confident that arilpums have a bright future ahead.


Monday, April 8, 2019

Arilpums: Fertile Arilbred Dwarfs!

by Tom Waters

'Aladdin's Gem' (Thoolen, 2002)
OGB/ABD

Most arilbred medians are produced by crossing standard dwarfs (SDBs) with fertile halfbreds (OGB). The results of such crosses tend to be pleasing garden subjects, occupying about the same niche as intermediates (IBs), but with the added interest of arilbred color patterns. Unfortunately, arilbred medians produced this way are usually infertile, or have very limited fertility at best. Also, being only ¼ aril (OGB-), they don’t always show enough pronounced aril characteristics to really stand out as arilbreds.

For those of us who enjoy the smaller arilbreds, the holy grail would be diminutive fertile arilbreds that are half aril in content. We might imagine miniaturized versions of the taller arilbreds that have come from breeding arils with tall bearded (TBs). One approach to realizing this dream is through the creation of “arilpums”: hybrids between arils and the tiny dwarf bearded species Iris pumila. This type of cross produces true arilbred dwarfs, around 10-12 inches (25-30 cm) in height, fertile, and half aril. Additionally, Iris pumila is expected to confer winter hardiness on its seedlings.

The potential of such breeding was first appreciated in the mid 20th century, when iris breeders became aware of the cytogenetics of irises, and the possibility of creating “fertile families” of irises from wide crosses, if the parents are chosen to have the right chromosome configurations to produce fertile offspring. Both the SDBs (from TBs crossed with Iris pumila) and the fertile arilbreds (from TBs crossed with arils) are examples of such fertile families, and show how varied and successful they can be.

The most direct way to build a fertile family of arilpums is to cross Iris pumila with tetraploid arils. In nature, the only tetraploid arils are the Regelia species Iris hoogiana and Iris stolonifera. Indeed, the pioneering hybridizer Paul Cook (who also introduced the first SDBs from TB x pumila crosses) produced two hoogiana/pumila hybrids in the 1950s: ‘Hoogpum Blue’ (Cook, 1956) and ‘Hoogpum Purple’ (Cook, 1956). Both were fertile, but Iris hoogiana doesn’t have many characteristics that most of us think of as epitomizing the “aril look”, and these little offspring were not very distinguishable from MDBs, and in fact were registered as such.

The first approach to arilpums with oncocyclus ancestry came from Peter Werckmeister, the great expositor of cytogenetic theory to English-speaking irisarians. In the 1970s, he produced “Miltonia” (not registered) from a lucky cross, in which the aril parent (an oncogelia from ‘Teucros’ x Iris susiana), although a diploid, acted as a tetraploid by producing an unreduced gamete. Werckmeister reported eventually creating a whole array of fertile arilpums from “Miltonia”. Alas, they were not widely distributed and are now lost to us.

Thoolen arilpum seedling AP9007-1
Interest in arilpums underwent something of a revival in the 1990s, after Samuel Norris and John Holden created a line of tetraploid oncogelias from using colchicine treatment. Crossing these with Iris pumila produced arilpums with much more “onco look” than had been possible previously. The first of these to be introduced was ‘Barbarella’ (Mathes, 1991), followed by ‘Aladdin’s Gem’ (Thoolen, 2002). Both Harald Mathes and Francesca Thoolen raised a number of different arilpum seedlings, but these were the only two registered and introduced into commerce. Both ‘Barbarella’ and ‘Aladdin’s Gem’ produce fertile pollen, but are unwilling pod parents. Mathes and Thoolen noted similar difficulties with their other arilpums, and their breeding programs were eventually abandoned.

The lack of pod fertility was an unfortunate setback, because the simplest way to build up this family would be to cross the existing arilpums among themselves, rather than repeating the initial aril x pumila crosses.

'Topaz Talisman' (Jensen, 2015)
RB/ABD
The most recent arilpum is the lovely stolonifera/pumila hybrid ‘Topaz Talisman’ (Jensen, 2015). It has not yet been tested extensively for pod fertility.

Why has this family not made more progress? It has been more half a century since its potential was first understood, theoretically. I do not believe the pod fertility issue is insurmountable, although it is a setback and perhaps kept the family from taking off in the 1990s, when interest was greatest. Since then, the number of hybridizers working with arilbreds has declined, and not all are interested in such an experimental project. The parent plants, tetraploid arils and Iris pumila, are not easy to grow in all locations: the arils need a very dry summer, and pumila needs a cold winter.

Another obstacle is that the initial crosses are difficult, not many viable seeds are produced, germination is poor, and so a lot of persistence is needed to bring arilpum seedlings to bloom. Since I began working in this area six years ago, I have made 365 pollinations, resulting in 525 seeds, and at long last four seedlings which I hope to see bloom this year or next.

I would love to see others get involved; the prospects for eventual success obviously depend on a number of people working with determination over the course of a number of years. Here is the recipe:
  1. Acquire tetraploid arils, such as Iris stolonifera, ‘Tadzhiki Bandit’, ‘Tadzhiki Eclipse’, ‘Werckmeister’s Beauty’, ‘Balalaika Music’, and ‘Dunshanbe’. Keep in mind that you must use tetraploid arils – crossing Iris pumila with random arils and arilbreds offers no special hope of fertility in the seedlings.
  2. Acquire Iris pumila, either from seed exchanges, or named cultivars such as ‘Royal Wonder’, ‘Wild Whispers’, ‘Little Drummer Boy’, ‘Hobbit’, and others.
  3. Make crosses between these two groups, as often as possible, and mixing and matching parents as much as possible.
  4. Also get any available arilpums (pretty much just ‘Aladdin’s Gem’ and ‘Topaz Talisman’ these days), to cross amongst themselves or with arilpum seedlings you produced from the aril/pumila crosses.

Hildebrandt arilpum seedling 11-4-2
(photo: George Hildebrandt)
I think this a project that offers enormous potential in the long term, and is ideal for a small, backyard hybridizer who does not have the resources to grow thousands of seedlings and does not need to worry about immediate commercial success. There is a whole new world waiting to be opened up!

Monday, November 7, 2016

Arilbred Irises: A Little History

Tom Waters

'Brash and Bold' (Black, 2009),
William Mohr medal 2106
(arilbred median)
The story of arilbreds begins in the late 19th century, when the exotic aril iris species of the Middle East found their way into the gardens of European plant enthusiasts. Sir Michael Foster, England's foremost iris expert at the time, tried his hand at crossing the arils with the more familiar tall bearded (TB) irises. His motives were mainly exploratory; at the time, no one knew if the arils and bearded irises were compatible, or whether desirable garden plants might result from crossing them.

Although these early arilbreds were interesting plants, showing features of both parents, they were also quite sterile. Arils and TBs were just too distantly related to produce fertile offspring when crossed. One might expect hybridizers to simply give up on the idea, but many kept trying. The allure of the arils, with their huge globular blooms, often strikingly marked with velvety signals, veins, and stippling, was not something to be lightly set aside. Also, the arils themselves were difficult to grow in England and much of the US, demanding very dry conditions when dormant in summer and winter. So the great hope was that crossing arils with TBs could produce an aril-like bloom on a plant that could grow in any garden where TBs grow.

The famous iris breeder William Mohr, working in California, produced an arilbred iris that seemed close to fulfilling this dream. Named for him posthumously in 1925 by his friend and fellow iris expert Sidney Mitchell, the iris 'William Mohr' was an instant sensation. Its large blooms and wide falls, inherited from its aril parent Iris gatesii, proved irresistible in an era when most TBs had relatively small, narrow flowers.

'Elmohr'
Like the other arilbreds of similar pedigree, 'William Mohr' was essentially sterile. But it was so popular that hybridizers all over the country kept making crosses with it, ever hopeful. And occasionally 'William Mohr' would reward such persistence by producing a seed or two. We now understand that these seeds were the result of unreduced gametes, where an ovule is produced by bypassing the normal cell division. Usually it was TB pollen used in making these crosses, so the resulting seedlings were 1/4 aril. 'Mohrson' and 'Grace Mohr' were the first introduced, in 1935, launching a tradition of working "Mohr" into the name of these arilbreds. One of these, 'Elmohr' (P. A. Loomis, 1942) became the first and only arilbred to win the Dykes Medal. In this way, William Mohr became associated with the "quarterbreds" (arilbreds of 1/4 aril ancestry), even though he himself never produced any irises of this type.

Although less widely appreciated than the famous 'William Mohr', there was actually one truly fertile arilbred in cultivation at this time, 'Ib-Mac' produced by the Dutch firm of Van Tubergen and introduced in 1910. Unreduced gametes were once again involved, as its aril parent Iris iberica produced an ovule will two sets of aril chromosomes instead of the usual one. 'Ib-Mac' thus ended up as a balanced tetraploid, with two sets of aril chromosomes and two sets of bearded chromosomes, a configuration that is usually fertile.

Crossing 'William Mohr' with 'Ib-Mac' produced the fertile arilbred 'Capitola' (Frank Reinelt, 1940). Many hybridizers now began using 'Capitola' pollen on TBs, a much surer way to produce quarterbreds than hoping for the occasional seed from 'William Mohr'. These quarterbreds were also colloquially referred to as "Mohrs".

The frustration for hybridizers of this era was that although one could produce quarterbreds by crossing 'William Mohr', 'Ib-Mac', or 'Capitola' with TBs, there was no easy way to get more arils into the mix. The quarterbreds only showed moderate aril characteristics, and did not go very far in capturing the appeal of the aril species themselves.

'Oyez'
The great breakthrough in arilbred breeding came from the work of Clarence G. White in the 1940s. Based in southern California, he was able to grow many pure arils and use them extensively in his hybridizing. His early hybrids, such as the perennially popular 'Oyez' (White, 1938), were infertile diploids, but eventually fertile arilbreds began to appear among his seedlings. The first to be introduced was 'Joppa Parrot' (White, 1948). In the decade that followed, a steady stream of fertile arilbreds in a remarkable range of colors and patterns issued from White's garden. We do not know exactly how this happened, because by this time White had given up on keeping records of his crosses, claiming it took too much time away from making the actual crosses. Most likely it was the sheer volume of his breeding program that made these breakthroughs possible. With an enormous number of seedlings, even unlikely events such as unreduced gametes are bound to happen from time to time. The fertile C. G. White arilbreds were later shown to be balanced tetraploids (like 'Ib-Mac' and 'Capitola') with two sets of aril chromosomes and two sets of TB chromosomes.

The 1950s saw the founding of the Aril Society International (ASI). Despite the name, its membership was largely concentrated in southern California, with a few in New Mexico and elsewhere. The ASI in its early years provided a much-needed framework for defining the arilbred class and encouraging the breeding of arilbreds with clear, strong aril flower characteristics. To be classified as an arilbred, an iris could have no less than 1/4 aril ancestry. Hybridizers had often crossed the early quarterbreds back to TBs, sometimes for several generations, promoting the progeny as "arilbreds", although their aril genes had in most cases dropped by the wayside, leaving plants that were for all intents and purposes just TBs. The ASI cooperated with the American Iris Society to establish the C. G. White award for best arilbred in 1961. In 1969, the William Mohr award was added for arilbreds of less than 1/2 aril ancestry, restricting the C. G. White award to those that are 1/2 or more aril. This further encouraged hybridizers to focus on arilbreds with strong aril characteristics. Both these awards attained medal status in 1993.

With the "fertile family" of C. G. White arilbreds firmly established, arilbred breeding at last came into its own. As breeders continued to work with these fertile arilbreds, they improved both in gardenability and in the form, color, and pattern of the flowers themselves. The original C. G. White hybrids typically had only a small diffuse signal patch, and veining that was indistinct and blended. Through the extended effort of dedicated arilbred hybridizers, we now have arilbreds with huge, dramatic signals, striking crisp veining, and an extraordinary range of bright clear colors.

'Anacrusis'
Most fertile arilbreds today derive almost entirely from the original C. G. White introductions. A few notable additions to the family appeared subsequently: 'Welcome Reward' (Sundt, 1971), Henry Danielson's fertile regeliabreds such as 'Genetic Artist' (Danielson, 1972), and Harald Mathes's fertile arilbred medians beginning with 'Anacrusis' (Mathes, 1992). Fertile arilbred seedlings produced by Samuel Norris from his tetraploid arils crossed with TBs also appear in the pedigrees of some modern arilbreds.

The fertile "C. G. White type" arilbreds have also opened up other new areas of arilbred breeding. Crossed with TBs, they have given us quarterbreds that are much more aril-like than the old "Mohrs", and crossed with the standard dwarf bearded (SDB) irises, they have produced the charming arilbred medians, which are at least as popular as the taller quarterbreds today.

The history of arilbred breeding has progressed from an early period of difficulty and frustration, through the breakthrough of C. G. White's "fertile family" to a modern era of continual improvement and expanding diversity. What will the future bring?