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The Development of Arilbred Irises

by John J. Taylor and Thomas M. Wilkes from Chapter 11, Arils and Arilbreds in "The World of Irises" ©AIS

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THE ARILBREDS

Seedlings from aril species or hybrids crossed with bearded iris species or garden varieties are known as arilbreds. Most arilbreds have been derived from oncos and regelias, though a number of dwarf varieties have been produced from the psammirises. Arilbreds from falcifolias and pseudoregelias have not yet been reported. Iris enthusiasts of the late nineteenth century were well acquainted with the beauty, grace and novelty of the oncocyclus and regelia irises. From gardening in the rainy temperate climate of Europe, they were also keenly aware of the difficulties in cultivating them. By 1885, some pioneering hybridizers had the idea of crossing arils with bearded irises in an attempt to preserve aril traits in more gardenable plants. Dammann's oncobred 'Alkmene' from I. paradoxa x I. swertii was probably the first of these arilbreds to be named, in 1896. It was soon followed by numerous arilbreds created by Foster, Denis, and the Van Tubergen company.

EARLY ARILBREDS

  'Alkmene' (1925) TBAlkmene  

Without knowledge of chromosome counts or homologies, early iris breeders of necessity used an experimental approach in crossing their plants. Because most of the arils and bearded irises at that time were diploids, nearly all the early arilbreds were diploid. Consequently, the improvement of arilbreds was plagued by hybrid sterility and poor germination, and progress was slow. By the middle 1920s, Grace Sturtevant had introduced the first arilbred from psammiris breeding, the partly fertile 'Ylo', and William Mohr had created several attractive but infertile regeliabreds and oncobreds.

EARLY ARILBREDS

  'William Mohr' (1925) TBWilliam Mohr  

In 1925, the diploid variety 'William Mohr' ( I. gatesii x 'Parisiana') was introduced. The large, globular blooms attracted much attention and many attempts were made to cross it with tall bearded varieties. Most failed, but occasionally 'William Mohr' set a small pod with a seed or two. We now know that those seeds were the result of unreduced gametes produced by 'William Mohr'. Through these unreduced gametes, 'William Mohr' had a great influence on the development of some of the tetraploid arilbreds.

DIPLOID ARILBREDS

Many crosses between diploid arils and diploid bearded irises have been reported. As expected, these crosses are difficult to make, producing few seeds, of poor quality. Germination, if any, is protracted and uncertain. Seedlings are usually sterile, though sometimes one may set a few seeds or produce viable pollen. Sir Michael Foster's 'Par-Var', for example, is slightly fertile both ways, while Mohr's 'Bellorio', McLeod 's 'Miss Martha', and White's 'Oyez' are occasional but penurious pod parents. An arilbred of this type, crossed with the regeliocyclus Saturnus by K. Dykes (sic Van Tubergen), produced 'Vacuna' in 1930. It is an early example of the hybrids sometimes called "three-quarter" arilbreds-from aril x (aril x bearded) or reciprocal crosses. Clarence White made thousands of crosses of arils with diploid bearded irises in his attempts to create fertile arilbreds, and registered about 30 of them. Some bear such intriguing names as 'Kish', 'Mozo', 'Myomy', 'Oyez' and 'Present'. Many of them are attractive and exhibit aril traits. Until recently, several were the most oncolike arilbreds available. A number of them are still grown and are quite vigorous. Although generally infertile, diploid arilbreds are worthwhile garden subjects. Modem miniature tall bearded irises and the newer bearded and aril species and hybrids may still be used to produce improved and novel varieties, such as the recently created diploid arilbred miniature dwarfs from I. timofejewii x I. humilis and I. timofejewii x I. korolkowii. The first of these is a dainty pinkish mauve, while the latter is a small pink version of its pollen parent.

TRIPLOID ARILBREDS

In crosses of a diploid with a tetraploid iris, barring an unreduced gamete, the seedlings, if any, are triploids. For many years, aril breeders assumed that triploid arilbreds were too infertile for useful hybridizing, and gave them little attention. However, though some seem sterile, many are partly fertile, occasionally both as pod and as pollen parents. Although triploids may be created by crossing tetraploid arils with diploid bearded irises, few have been reported, and by the 1970s only Dykes's 1923 'Twilight' had been registered. The more frequent crosses of diploid arils with tetraploid bearded varieties have involved all types of arils except falcifolias and pseudoregelias, and all classes of tetraploid bearded irises, including intermediates and amphidiploid arilbreds. Among the first named triploid and probably the first of the arilbred medians, was Monsieur Steichen from I. chamaeiris alba x I. iberica . Few other triploids of this type were reported until 1931 when E. B. Williamson- Charles Gersdorff introduced 'Baby Blue' and 'Fallen Leaf', both from I. korolkowii . Beginning in 1933, the Sass brothers introduced 'Gray Cloud', 'Stormy Dawn', 'Blue Topaz', 'Velvo' and others from crosses between regeliocycli and 40-chromosome dwarfs. In the years that followed, Marx, Hillson, Zickler and other breeders produced many more of this general type. Although some of the earlier triploid aril-medians are still grown, they have largely been superseded by the more recent floriferous and vigorous introductions: Rich's 'Kelita' series of 1966, and 'Canasta' and 'Nightlight' of 1975; Vallette's 'Plum Cute', and Taylor's 'Snow Pup' and 'Hoe Down' registered in 1976. . .

Most miniature dwarf arilbreds have been produced from psammirises crossed with 40·chromosome dwarfs (chap. 8). Some of these triploid miniatures are fertile and have been crossed with tetraploid miniature and standard dwarfs to produce such varieties as 'Lilac Girl' and 'Emerald Rays'. When some of the fertile triploids were backcrossed to psammirises, another unusual kind of "three-quarter" arilbred resulted, examples of which are the diminutive 'Tiny Treasure' introduced by Hillson in 1943, and Welch's 1956 'Morning Light'.

A substantial number of taller triploids have been obtained by crossing diploid arils with 48-chromosome bearded varieties. M. Foster's 'lb-Troy' was probably the first oncobred from such breeding, in 1893, Denis's 1923 'Korolcyp' the first regeliabred, and Ugrinsky's 'Kola', 'Missona' and 'Valery Germanis' the first from psammirises.

Others from many breeders have since been registered, and the early varieties are rarely grown. Some more recent introductions include 'Rojo Grande' from I. susiana, McLeod's posthumously named 'McLeod', Dom's 'Hannelore', and Blomquist's 'Red Rapport' from I. korolkowii. These produce a few good seeds when crossed with fertile tetraploids, and the seedlings are often fully fertile tetraploids.

Another important group of triploid arilbreds has been created by crossing the diploid arils with fertile tetraploid arilbreds, often C. G. White varieties or their derivatives. These are the most common and popular of the "three-quarter" arilbreds, and most have well-defined onco or regelia traits. William Mohr produced at least three of this type by crossing aril species with 'lb-Mac' in the early 1920s. One from I. korolkowii was introduced under the name 'Morera' in 1928. Since about 1955 a number have been introduced including: Sundt's 'Susimac'; Danielson's 'Radiant Smile', 'Tul Kerem', and 'Big Black Bumblebee' (figure 4) which won the C. G. White award in 1970; Johnson's glowing regeliabred, 'Red Korol'; and about 20 introductions from Leo Clark including such popular varieties as 'Corning', 'Addis Ababa', 'Prolific' (figure 4), ''Scrumptious' and 'Sudden Beauty'. Many of the popular "three-quarter" arilbred triploids are as easily grown as their arilbred parents, but usually are more aril-like in appearance. The color range of the group extends from white, cream, and yellow to orange red, and from pale mauve to purple. Many are almost selfs or amoenas, and others are rich blends. Some are neatly marked with delicate veins and dots, while others are more coarsely veined and speckled. Most have well-defined signals. They usually produce two flowers on each stem. Some of them are partly fertile when crossed with fertile tetraploids, and some seedlings from such crosses may also be fertile tetraploids (Wilkes 1974, 1975).

TETRAPLOID ARILBREDS

The largest and most important group of arilbreds are tetraploid. Tetraploid arilbreds may be considered of two sorts: fully fertile amphidiploids and balanced tetraploids which behave in breeding as amphidiploids (see chapter 26); and unbalanced, relatively infertile varieties. All the former group will be treated here as amphidiploids. The latter group, though infertile, has included many popular arilbreds since 1940, and many are still being introduced. This relatively infertile group includes the well-known "Mohr" irises.

THE MOHRS
The many futile attempts to set seeds on the diploid oncobred 'William Mohr' have been mentioned earlier. The first seedlings from William Mohr came from crosses with tetraploid tall bearded varieties and were tetraploid oncobreds. 'Mohrson' and 'Grace Mohr', in 1935, were the first to be introduced. Since then a substantial number, known collectively as "Mohrs," have been registered.

When Reinelt crossed 'William Mohr' with Van Tubergen's amphidiploid oncobred, 'lb-Mac', he created the highly fertile 'Capitola', one of the most famous pollen parents in iris history. Crossing 'Capitola' or 'lb-Mac' with tall bearded irises yielded progeny that were also classed as "Mohrs" because of the striking similarities among all of them. Since 1940, there has been a continuous procession of "Mohrs" from many breeders, especially from Tom Craig ('Heigho', 'Hurricane', 'Punch Bowl', 'Engraved' [figure 4] and others), and Jack Linse ('Blue Motife', 'Darlene Waters', 'Front Row', 'Trophy', etc.). Recent "Mohrs" include Gadd's 1971 'Isle of Zoar' and Danielson's 1975 'Aril Lady'. Some of the Mohrs are fertile with tall bearded irises, but seedlings from such crosses have shown few onco traits and many are inferior to tall bearded varieties. Crossing Mohrs with tetraploid regelias or regeliocycli, or with amphidiploid arilbreds has produced slightly fertile seedlings, but many lack the aril look. Repeated backcrossing to fertile tetraploid arilbreds produces progeny with considerable fertility and aril appearance. However, the Mohrs have not been used extensively in the development of modern arilbreds.

A group of arilbreds analogous with the Mohrs and frequently indistinguishable from them have been produced from crosses between tall bearded varieties and the C. G. White amphidiploid arilbreds and their progeny. Recent introductions from this kind of breeding in the early 1970s included Palmer's 'Green Mosaic', Hawkinson's 'Mai Tai', Peterson's 'Nicosia', and Scopes's 'Kalifa Gold'. A few of these unbalanced tetraploids are fertile, and have been backcrossed to amphidiploid arilbreds to produce the aril-like 'Cairo Sands' from Slamova, Fisherman's Net' from Tate, and 'Kaspar' from Hawkinson.

Also like the Mohrs are varieties from crosses of tall bearded irises with amphidiploid regeliabreds, among them 'Lake Elation', 'Fijian Seas', 'Saffron Jewel', 'Little Sheba', and Samuelson's 'Exotican' series of 1963. These have little fertility and few, if any, regelia traits.

Unbalanced tetraploids have also been produced by crossing amphidiploid arilbreds with tetraploid arils. 'Persian Art', 'Bedouin Child', 'Celeste Azul', 'Desert Fire', and 'Sadira' are of this type. 'Almost' and 'Ma Su Chen' are from unreduced oncocyclus gametes. These "three-quarter" arilbreds usually resemble their aril parents and are predictably infertile, though successful pollinations are occasionally reported. Tetraploid arilbred medians have been produced when tetraploid arils and amphidiploid arilbreds were crossed with 32- or 40-chromosome dwarfs. Since Schreiner's 'Peshawar' and Sass's 'Little Master', many dozens of these arilbreds have been registered (see chapter 9). Among them are Nichols's 'Byzantine Beauty', Hunt's 'Clouded Moon', Palmer's 'Haymaker', Alta Brown's 'lbab', Shelton's 'Little Mama', Doris Foster's 'Little Orchid Annie', and Blyth's 'Pirate Bird' and 'Sajjetta'. A few of these are sometimes fertile and can be used for further breeding.

FERTILE TETRAPLOID ARILBREDS

It is to Clarence G. White that we owe most of our modern fertile arilbreds (Wilkes 1964). For over 30 years he patiently worked to develop fertile arilbreds with the "onco look." His first successes date to 1938 when his "parrot" seedlings first bloomed; 'Joppa Parrot' was introduced from this group in 1945. From 1950 to 1957 he introduced more than 30 tetraploids, most of which were fertile. White insisted that he didn't know how he got his tetraploids, but also insisted that his general practice was to cross diploid arils ("oncos") with his and other arilbreds. This seems unlikely from cytogenetic considerations. Some of White's varieties were readily intercrossed, and the progeny backcrossed, linebred or outcrossed to produce the advanced generations presently grown.

In 1960, L. Fitz Randolph and J. Mitra reported that the fertile C. G. White arilbreds were 44-chromosome tetraploids containing two sets of aril and two sets of tall bearded iris chromosomes. At the same time, Peter Werckmeister deduced from seedling patch evidence that the White arilbreds must be amphidiploid-like (1960), and suggested (1961) intercrossing and linebreeding them and outcrossing them to other amphidiploid or amphidiploid-like arilbreds. Along with Randolph and Mitra's cytogenetic information, Werckmeister's "fertile family" approach gave breeders the basic theoretical knowledge needed to plan crosses that would produce fully fertile seedlings. It was this kind of fertile family breeding that had led to Sundt's 'Ardirnac' in 1959 and to Hunt's 'Esther the Queen' (figure 4) from an 'Ardimac' sibling x 'Kalifa Gulnare'. 'Esther the Queen' won the C. G. White award in 1971.

The present fertile family of amphidiploid and amphidiploid-like arilbreds includes the 44-chromosome White varieties and their intercross progeny, and 'lb-Mac', 'Capitola', 'Ardimac', 'Ardrun' and 'Sharksiana' as well as the Sundt-Rich 'Welcome Reward' and Taylor's 'Brawny Bill'. This group can be expanded through several lines of breeding: by crossing the so-called "three-quarter" arilbred triploids and tetraploids with tall bearded irises; by crossing tetraploid arils with 48-chromosome bearded varieties; and of course, by further intercrossing available amphidiploids. The "three-quarter" arilbred seedlings from crossing 'Capitola', 'Welcome Reward' and some others with aril species and hybrids could be used to produce amphidiploid arilbreds of known parentage.

When tetraploid arils are crossed with 48-chromosome bearded irises, amphidiploid arilbreds are readily obtained. Many such crosses have been reported, and the seedlings are generally vigorous and arillike in appearance. Since the mid-1950s few of this type have been introduced. Danielson's 'Collector's Pride', 'Genetic Artist' and 'Genetic Leader' all stem from tetraploid regelias. Analogous amphidiploids from tetraploid regeliocycli have not been registered to date. These 46-chromosome amphidiploid regeliabreds are interfertile and a few seedlings from crosses among them have been introduced, including 'Buddy Mitchell' from Nourse, 1957, and Danielson's 'Stars over Chicago', 'Genetic Dancer', and 'Genetic Moment'. These will interbreed with other members of the fertile family, and provide a practical tool for directly introducing desirable qualities of the modem border and tall bearded irises into the amphidiploid arilbreds. This is significant because many of our present varieties have old and inferior tall bearded irises in their pedigrees. Crosses between 44- and 46-chromosome amphidiploids are easy to make; seeds from such crosses germinate readily, and seedlings are generally vigorous and fully fertile. However, only a few have been introduced as yet, among them 'Vandal', from Crandall in 1964, 'King's Silk', Rogers 1970, and Taylor's 'Kalisaf', introduced in 1975.

Another group of interfertile tetraploids consists of 35- to 38-chromosome amphidiploid hybrids between tetraploid arils and pumilas. Cook's 'Hoogpum Blue' and 'Hoogpum Purple', introduced in 1956, are examples of such arilpums. Werckmeister's attractive and vigorous hybrids between I. hoogiana and yellow Serbian I. pumila demonstrated that many colors are possible in the arilpums.

Werckmeister's observations of these early arilpums and his familiarity with Simonet's (1932) concepts for producing "synthetic species" led him to predict (1960) that it should be possible to develop an amphidiploid-like 36- to 38-chromosome fertile family analogous to the 44- to 46-chromosome fertile arilbreds, by crossing diploid arils with I. pumila. Fully fertile tetraploids would result on occasion from unreduced aril gametes. He also pointed out that tetraploid regeliocycli could be used to expand this group of aril dwarfs, and predicted that all would be interfertile. Werckmeister spent many years developing a number of 36- to 38-chromosome arilbreds of this type. His first named hybrid was the tetraploid Miltonia from a cross of ('Teucros' x I. susiana) x I. pumila. Others came from crosses of 'Persian Pansy' and a few of his own tetraploid regeliocycli with I. pumila. (His tetraploid regeliocycli were obtained by treating embryos from crosses of 'Teucros' x I. susiana with colchicine.) By intercrossing his seedlings, Werckmeister enlarged his arilpum group into another fertile family of arilbreds. Considering the enormous color variations of I. pumila and cytogenetically similar miniature dwarf bearded garden clones, and the wide variety of diploid, triploid and tetraploid arils, it is apparent that a new race of attractive, hardy and interfertile dwarf arilbreds is imminent.

Because these amphidiploid dwarf arilbreds are analogous from a cytogenetic viewpoint to the taller arilbreds of the 44- to 46-chromosome fertile family, it would seem that we should expect them to be similar in their breeding behavior. However, at this writing the only three-quarter arilbred dwarfs from arilpum breeding are those which Paul Cook produced from crosses between his 'Hoogpums' and the psammirises.

HIGHER POLYPLOID ARILBREDS

A number of balanced and unbalanced arilbred polyploids with higher chromosome numbers have been reported; these include fertile pentaploids, hexaploids and one octoploid. The octoploid was produced by treating the tetraploid 'Hoag-Cham' (I. hoogiana x I. chamaeiris) with colchicine, while the others resulted from breeding. Simonet's pentaploid, 'Koriantha', came from an unreduced gamete of the 31-chromosome 'Koris' (I. korolkowii x I. chamaeiris) and a normally reduced gamete from his amphidiploid 'Autosyndetica' (I. hoogiana x 'Macrantha') x 'lb-Mac'. Rich's pentaploid seedling is of similar origin, and came from a cross of his triploid 'Kelita Adah' (Austin's oncocyclus hybrid OY-164 x 'Pogo') with Clark's fertile tetraploid seedling from 'Jallah Effendi' x (I. gatesii x I. auranitica).

The arilbred hexaploids are exemplified by three Werckmeister seedlings from I. stolonifera x 'Ivorine', a 44-chromosome median bearded iris. These were the first seedlings reported from an unreduced tetraploid male gamete, and have been called the 'Stolorine' seedlings. Although they, like the arilbred pentaploids, are fertile in outcrosses, they have not yet proved interfertile.

As expected the balanced octoploid from 'Hoog-Cham' is fertile both ways, and has been backcrossed to I. hoogiana and outcrossed to the 'Stolorines' to produce rampant seedlings which look very much like regelias. ' . · ·

The polyploids with more than four chromosome sets that have been produced to date are all interesting, with traits from the three great bearded iris groups: the arils, the tall bearded irises, and the dwarfs of the I. pumila type. The unexpected fertility of some also suggests great breeding potential-but these higher polyploids have been difficult to produce, and it is unlikely that much will be done with them until easier ways are developed for creating them in quantity.

CULTURE OF THE ARILBREDS

The arilbreds can be grown successfully in almost all climates by using the same cultural methods as those used for arils, even though most arilbreds are of much easier culture. The regeliabreds and other similar arilbreds are usually grown in the open essentially like the tall bearded irises, but may need better drainage in regions with over 62 cm (25 inches) of rainfall annually. The oncobreds and similar arilbreds are often grown in the open, but usually require more drainage than regeliabreds in wetter areas. Arilbreds from psammirises are grown like standard dwarfs. All respond to light, warm, rich soils. In climates where winter protection is required for the more tender tall bearded irises, some arilbreds also must be protected. Consequently, selecting the most tolerant varieties is important in regions with cold, wet winters.

The arilbreds are heavy feeders and benefit from regular fertilizing. They resent crowding and generally must be divided every two or three years, while more rampant varieties may require annual division. All are attacked by aphids, whitefly and other insects, and by leaf spot and other fungi. These should be controlled (chap. 23, 24). Persons growing arilbreds for the first time can profit from the experiences of successful growers in their own areas.

THE FUTURE OF ARILS AND ARILBREDS

We may expect continuing development of more gardenable arils and arilbreds. The most significant advances in arilbred breeding will probably be additions to the fertile families already extant or under development. Because developments in iris breeding and breeding theory since 1960 have provided hybridizers useful methods for utilizing more effectively what is available, we can anticipate arilbreds with even further variations in color, form, and height. With the wealth of bearded irises now available, and the enlarging group of arils, the potential of arilbred breeding is almost unlimited. The prospects of hexaploid and octoploid breeding may encourage experimentation with colchicine treatment (Appendix C).

The polyploids developed so far have been fertile, and there is evidence that the tetraploid level may not necessarily be optimal in developing arils and arilbreds. Prospects for producing tetraploid psammirises appear dim at this time, but we may expect worthwhile introductions from crossing the natural diploids with modern dwarf irises and with the low-growing 24- and 48-chromosome bearded varieties. Families of tetraploid arils and arilbreds could doubtless be developed from the falcifolias and pseudoregelias with much time and effort, but it is doubtful that they could contribute in any significant way to the breeding of attractive and useful arilbreds.


Continued from first part of Chapter 11 The Development of the Aril Irises

For more information on historic Irises visit the Historic Iris Preservation Society at http://www.historiciris.org/

-- BobPries - 2015-12-17
Topic revision: r17 - 13 Nov 2022, AlainFranco
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