Before we discuss hybrid lilies, let’s look at the meaning of hybrid:

The Meaning of Hybrid

In biology and specifically genetics, hybrid has several meanings, all referring to the offspring of sexual reproduction.
1. In general usage, hybrid is synonymous with heterozygous: any offspring resulting from the mating of two distinctly homozygous individuals
2. a genetic hybrid carries two different alleles of the same gene
3. a structural hybrid results from the fusion of gametes that have differing structure in at least one chromosome, as a result of structural abnormalities
4. a numerical hybrid results from the fusion of gametes having different haploid numbers of chromosomes
5. a permanent hybrid is a situation where only the heterozygous genotype occurs, because all homozygous combinations are lethal.

From a taxonomic perspective, hybrid refers to offspring resulting from the interbreeding between two animals or plants of different taxa.
1. Hybrids between different subspecies within a species (such as between the Bengal tiger and Siberian tiger) are known as intra-specific hybrids. Hybrids between different species within the same genus (such as between lions and tigers) are sometimes known as interspecific hybrids or crosses. Hybrids between different genera (such as between sheep and goats) are known as intergeneric hybrids. Extremely rare interfamilial hybrids have been known to occur (such as the guineafowl hybrids). No interordinal (between different orders) animal hybrids are known.
2. The second type of hybrid consists of crosses between populations, breeds or cultivars within a single species. This meaning is often used in plant and animal breeding, where hybrids are commonly produced and selected because they have desirable characteristics not found or inconsistently present in the parent individuals or populations. This flow of genetic material between populations or races is often called hybridization.

Etymology

According to the Oxford English Dictionary, the word is derived from Latin hyba, meaning the “offspring of a tame sow and a wild boar”, “child of a freeman and slave”, etc. The term entered into popular use in English in the 19th century, though examples of its use have been found from the early 17th century.

Types of hybrids

Depending on the parents, there are a number of different types of hybrids;
Single cross hybrids result from the cross between two true breeding organisms and produces an F1 generation called an F1 hybrid (F1 is short for Filial 1, meaning “first offspring”). The cross between two different homozygous lines produces an F1 hybrid that is heterozygous; having two alleles, one contributed by each parent and typically one is dominant and the other recessive. The F1 generation is also phenotypically homogeneous, producing offspring that are all similar to each other.

Double cross hybrids result from the cross between two different F1 hybrids.

Three-way cross hybrids result from the cross between one parent that is an F1 hybrid and the other is from an inbred line

Triple cross hybrids result from the crossing of two different three-way cross hybrids.

Population hybrids result from the crossing of plants or animals in a population with another population. These include crosses between     oganisms such as inter-specific hybrids or crosses between different races.

Interspecific hybrids

Interspecific hybrids are bred by mating two species, normally from within the same genus. The offspring display traits and characteristics of both parents. The offspring of an interspecific cross are very often sterile; thus, hybrid sterility prevents the movement of genes from one species to the other, keeping both species distinct. Sterility is often attributed to the different number of chromosomes the two species have, for example donkeys have 62 chromosomes, while horses have 64 chromosomes, and mules and hinnies have 63 chromosomes. Mules, hinnies, and other normally sterile interspecific hybrids cannot produce viable gametes because the extra chromosome cannot make a homologous pair at meiosis, meiosis is disrupted, and viable sperm and eggs are not formed. However, fertility in female mules has been reported with a donkey as the father.
Most often other processes occurring in plants and animals keep gametic isolation and species distinction. Species often have different mating or courtship patterns or behaviors, the breeding seasons may be distinct and even if mating does occur antigenic reactions to the sperm of other species prevent fertilization or embryo development. The Lonicera fly is the first known animal species that resulted from natural hybridization. Until the discovery of the Lonicera fly, this process was known to occur in nature only among plants

While it is possible to predict the genetic composition of a backcross on average, it is not possible to accurately predict the composition of a particular backcrossed individual, due to random segregation of chromosomes. In a species with two pairs of chromosomes, a twice backcrossed individual would be predicted to contain 12.5% of one species’ genome (say, species A). However, it may, in fact, still be a 50% hybrid if the chromosomes from species A were lucky in two successive segregations, and meiotic crossovers happened near the telomeres. The chance of this is fairly high: (where the “two times two” comes about from two rounds of meiosis with two chromosomes); however, this probability declines markedly with chromosome number and so the actual composition of a hybrid will be increasingly closer to the predicted composition.

Hybrids are often named by the portmanteau method, combining the names of the two parent species. For example, a zeedonk is a cross between a zebra and a donkey. Since the traits of hybrid offspring often vary depending on which species was mother and which was father, it is traditional to use the father’s species as the first half of the portmanteau. For example, a liger is a cross between a male lion and a female tiger, while a tigon is a cross between a male tiger and a female lion.

Hybrids between domesticated and wild animals in particular may be problematic. Breeders of domesticated species discourage crossbreeding with wild species, unless a deliberate decision is made to incorporate a trait of a wild ancestor back into a given breed or strain. Wild populations of animals and plants have evolved naturally over millions of years through a process of natural selection in contrast to human controlled selective breeding or artificial selection for desirable traits from the human point of view. Normally, these two methods of reproduction operate independently of one another. However, an intermediate form of selective breeding, wherein animals or plants are bred by humans, but with an eye to adaptation to natural region-specific conditions and an acceptance of natural selection to weed out undesirable traits, created many ancient domesticated breeds or types now known as land races.

Many times, domesticated species live in or near areas which also still hold naturally evolved, region-specific wild ancestor species and subspecies. In some cases, a domesticated species of plant or animal may become feral, living wild. Other times, a wild species will come into an area inhabited by a domesticated species. Some of these situations lead to the creation of hybridized plants or animals, a cross between the native species and a domesticated one. This type of crossbreeding, termed genetic pollution by those who are concerned about preserving the genetic base of the wild species, has become a major concern. Hybridization is also a concern to the breeders of purebred species as well, particularly if the gene pool is small and if such crossbreeding or hybridization threatens the genetic base of the domesticated purebred population.

The concern with genetic pollution of a wild population is that hybridized animals and plants may not be as genetically strong as naturally evolved region specific wild ancestors wildlife which can survive without human husbandry and have high immunity to natural diseases. The concern of purebred breeders with wildlife hybridizing a domesticated species is that it can coarsen or degrade the specific qualities of a breed developed for a specific purpose, sometimes over many generations. Thus, both purebred breeders and wildlife biologists share a common interest in preventing accidental hybridization.

Hybrid Lilies

A summary of the meaning of hybrid

In biology and specifically genetics, hybrid has several meanings, all referring to the offspring of sexual reproduction.
1. In general usage, hybrid is synonymous with heterozygous: any offspring resulting from the mating of two distinctly homozygous individuals
2. a genetic hybrid carries two different alleles of the same gene
3. a structural hybrid results from the fusion of gametes that have differing structure in at least one chromosome, as a result of structural abnormalities
4. a numerical hybrid results from the fusion of gametes having different haploid numbers of chromosomes
5. a permanent hybrid is a situation where only the heterozygous genotype occurs, because all homozygous combinations are lethal.

From a taxonomic perspective, hybrid refers to offspring resulting from the interbreeding between two animals or plants of different taxa.
1. Hybrids between different subspecies within a species (such as between the Bengal tiger and Siberian tiger) are known as intra-specific hybrids. Hybrids between different species within the same genus (such as between lions and tigers) are sometimes known as interspecific hybrids or crosses. Hybrids between different genera (such as between sheep and goats) are known as intergeneric hybrids. Extremely rare interfamilial hybrids have been known to occur (such as the guineafowl hybrids). No interordinal (between different orders) animal hybrids are known.

2. The second type of hybrid consists of crosses between populations, breeds or cultivars within a single species. This meaning is often used in plant and animal breeding, where hybrids are commonly produced and selected because they have desirable characteristics not found or inconsistently present in the parent individuals or populations. This flow of genetic material between populations or races is often called hybridization.

Lilies have always been admired, although they have not always enjoyed the same soaring popularity as today. Once they were the rich man’s play thing, when intrepid explorers and collectors sent back bulbs and seeds from Asia to Europe and America. These proved to be wonderful, new, exciting plants but often capricious, and many of the precious lilies lasted only a few years. The lily achieved its reputation for beauty and difficulty in these years between the end of the nineteenth century and the outbreak of the First World War.

The lily revolution really got underway in the 1950s, when the work of Jan de Graaff began to make a huge impact on the gardening public. All the best forms of species and hybrids were brought together, and a large-scale program of hybridization got under way. Phalanxes of new hybrids were introduced and proved to be so much more spectacular in growth and reliability as well as looks that they became irresistible. Globally, the main breeding work has been with the Asiatic hybrids, especially with those that have upward-facing flowers. Rapid propagation, quick and easy culture combined with attractive colors and flower forms that ensured easy packing and distribution, guaranteed success, making it the ideal cut flower. Many millions are sold annually in most European countries, in America, Australasia and all over the world, in florist’s shops and all sorts of stores. Even those with only a modest interest in gardening have bought packets of bulbs or carried home pots of lilies in growth. The lily is proving the ideal plant for modern homes and gardens. This explosion of interest would not have taken place if the plants had remained as relatively idiosyncratic as the original species. Breeding programs have cancelled out many of the inhibitions and problems with the wild plants and now we enjoy one of the easiest of plants.

Once you have tried a few Asiatic hybrids and found out how easily they grow in pots or in the garden, it is a short step to becoming an aficionado keen to try new kinds and types and also ‘to spread the word’. The diversity allows you to specialize, perhaps rejoicing in the almost overwhelming Orientals, or finding the long-lived, naturalizing martagon types just the thing to bring magic to your garden.

Hybrid lilies are offered as cultivars and as mixed strains. Thus you can buy a cloned cultivar such as ‘Enchantment’, with all the bulbs producing identical plants, or bulbs of a strain such as Citronella which is a ‘grex’, a number of clones of the same or very similar parentage with many characteristics in common, but not producing identical flowers. Commercial growers and dealers are happy to increase both classes of products and to market them.

The wild lily increases mainly by seed, and this is a realistic way for gardeners to increase their stocks. Some cultivars have been in cultivation for well over fifty years and are still worth growing, but perhaps we should think of lilies as plants that go through a natural cycle, to be replaced after some years. Growers of species know that some kinds are naturally short-lived, and they always have replacement seedlings coming along. The hybrids are unlikely to die out in this manner, but we could help to keep all well by arranging a turnover. We can then keep our outstanding kinds and also constantly upgrade the collection or change its balance.

Division 1: Asiatic hybrids

The most widely grown type of hybrid lily in gardens worldwide is the Asiatic hybrids, bred largely from the earlier-flowering Asian species. So many species are involved in their ancestry that there is almost infinite variation among them, particularly in the flower colors, which may be brilliant or soft, in all the warm shades and white. There is also an extensive range of heights and flower forms.

Asiatic hybrids are derived from the following species and their varieties:
  L. amabile
  L. bulbiferum
  L. callosum
  L. cernuum
  L. concolor
  L. dauricum
  L. davidii
  L. lankongense
  L. leichtlinii
  L. pumilum
  L. lancifolium
  L. wilsonii      

a: Upright-facing flowers.
b: Outward-facing flowers.
c: Pendent flowers.

Division 2: Martagon hybrids

As the name suggests these are derived from Lilium martagon and, initially, L. hansonii. Compared to the Asiatic lilies this is a very small group. Because they take longer from seed to flower – between five and seven years – results for hybridizers are slower and commercial interest has been slight.

Quite different in appearance from the Asiatic lilies, the whole plant is dainty, generally of medium to tall height bearing nodding, Turk’s cap-shaped flowers that add a sense of Eastern mystery to any garden. Like the species’ parents they flower early in the season, enjoy light shade and usually produce lots of flowers. They will also tolerate alkaline soil, thrive in heavy clay and loam but do well in sandy soils, too. Although they love shady places they can handle full sun. The flower color range is wide: white, yellow, orange, tangerine, mahogany, brown, lavender and lilac.

‘Marhan’, the first well-known hybrid in the group, was produced in 1891 in the Netherlands and is still available. It grows up to 6 ft. (1.8 m) with spotted flowers in a rich, orange-chestnut color.

A group of hybrids from Lilium martagon and L. hansonii, known as the Backhouse hybrids, was bred at the turn of the 20th century in England.

The Paisley hybrids appeared somewhat later and were a cross between Lilium martagon var. album and L. hansonii. In the second generation, the flower color range increased. From shades of gold and bronze they broadened to include clearer yellows and oranges as well as white and lilac.

These are normally healthy plants, resistant to virus and very cold hardy. Once planted, they will survive happily in one place for many years.

Martagon hybrids are derived from the following species and their varieties:
  L. hansonii
  L. martagon
  L. medeoloides
  L. tsingtauense

Division 3: Candidum hybrids

This is a small group and includes one of the oldest known hybrids, Lilium x testaceum, known as the Nankeen lily, a cross made in the early 19th century between L. candidum with trumpet-shaped flowers and L. chalcedonicum, with bright red Turk’s cap shaped blooms. More recently L. monadelphum, L. cernuum, L. longiflorum and L. henryi have been used in crosses with L. candidum and various Asiatic hybrids using embryo rescue techniques. With stems growing to 4 ft. (1.2 m), the flowers are big and fragrant and appear in early summer.
‘June Fragrance’, bred in 1971 from the variety Lilium candidum salonikae with L. monadelphum, is a notable hybrid in its own right with creamy white, perfumed flowers in early spring. It has been used in subsequent years as a parent of more hybrids.

Candidum hybrids are derived from the following species and their varieties:
  L. candidum
  L. chalcedonicum
  L. monadelphum

Division 4: American hybrids

These are generally tall, stately plants bred from the western or Pacific Coast species of North America. The flowers are mainly Turk’s cap-shaped, though less tightly reflexed than some of the species themselves. Like the martagon hybrids, they enjoy light shade, making attractive woodland plants with flowers in late spring or early summer. Best known are the Bellingham hybrids bred from Lilium humboldtii var. ocellatum, L. pardalinum and L. parryi.

In England Derek Fox used these to create his Bellmaid hybrids in 1968. Flowers are a rich yellow, darkening with age and are typically pendent, with reflexed petals. His Bullwood hybrids, introduced the previous year and bringing pink into the color spectrum, resulted in seedlings with peach-toned flowers and others where the typical orange-red of several species becomes a richer red.

American hybrids are derived from any North American species. Present-day hybrids in this division mostly originate from the western American species:
  L. bolanderi
  L. humboldtii
  L. kelloggii
  L. pardalinum
  L. parryi

Division 5: Longiflorum hybrids

L. longiflorum has had a long history of cultivation for the cut-flower and pot-plant trade. One form became associated with the name ‘Easter lily’ although now this is used with less precision for most forms of L. longiflorum. Over the years there have been, and still are, many named forms varying by fairly small taxonomic details but sometimes important commercial ones. Dwarf forms are useful for pots, ones with distinct foliage can be equally welcome. However, until fairly recently hybridization has not been an obvious part of the lily’s activities. Now this has changed somewhat with a range of hybrids with the rather similar L. formosanum, hybrids which certainly grow with vigor and produce good crops of pure white trumpet flowers. These still are on the whole of more interest to commercial growers than the amateur gardener.
Longiflorum hybrids are derived L. longiflorum. Most such lilies in the trade are: 

L.longiflorum x Asiatic hybrids (Division 1)     

a: Upright-facing flowers.
b: Outward-facing flowers.
c: Pendent or downward-facing flowers.

Division 6: Chinese trumpet and Aurelian hybrids

This group divides into two parts: the purebred trumpets, derived from the crossing of trumpet species and their hybrids, and the entire range of lilies that have in their breeding some of that tough species L. henryi – the antithesis of trumpet – form and a different kind of plant.
The pure trumpet hybrids have been derived from a number of species. These hybrids grown in gardens in temperate zones have been bred from L. regale, L. sargentiae, L. leucanthum, L. brownii and L. sulphureum. Some species, such as L. sulphureum and L. sargentiae, have never been plentiful in gardens as they are prone to succumb to virus.

A major advance in breeding took place when the de Graaff breeders raised large numbers of L. leucanthum centifolium and exercised a rigorous selection process to keep only those plants that appeared stronger and had wide-petalled flowers in a defined, pyramid shaped inflorescence. The inner white and the dark purple-mahogany of the buds were both intensified. The selected kinds were then mated with L. sargentiae, L. sulphureum and L. brownii. The selected progeny were originally marketed as Centifolium hybrids but then were renamed in 1955 and launched as the Olympic hybrids – a range of fine trumpets covering all colors from white, cream, lime and yellow to pink. Checking through the white-flowered ones led to further selection and reselection to end with the Black Magic strain with large white blooms with dark reverses. One outstanding plant was cloned and introduced as ‘Black Dragon’.

The most successful of the yellow trumpets has been the Royal Gold series, sometimes marketed as ‘the golden regale’. The progenitor of this was a yellow-flowered plant that turned up in the middle of a block of straight L. regale on the de Graaff farms. It was thought that L. sulphureum may have had something to do with the parentage and be the obvious reason for the flooding of the whole flower with yellow pigment. Certainly the original plant and the strain developed from it look very much of the L. regale stable.

From the progeny of both the cross L. regale x L. sargentiae and from batches of L. leucanthum centifolium appeared individuals with petals with pink margins and/or veining. These were gathered and interbred and suddenly pink flowers were raised which became the basis for the Pink Perfection strain. It is still not clear whether this breaking of the inhibition on the color zoning in the pinks was due to natural mutation, recombinations of genetic material or the accidental introduction of pollen from Aurelian hybrids which, with their L. henryi background, are free of zoning inhibitions.

It was the introduction of L. henryi material that enabled breeders to produce a much wider range of lilies that proved to be very hardy and amenable to a wide range of garden conditions.

The varying forms of these Aurelians necessitated their classification. The ‘trumpet’-division was split into four -these four classes have recently been modified so that they are separated by flower form.

Chinese trumpet and Aurelian hybrids are derived from the following Chinese species with purple bulbs:
  L.leucanthum
  L. regale
  L. sargentiae
  L. sulphureum
  L. henryi  

a: Upright-facing flowers.
b: Outward-facing flowers.
c: Downward-facing flowers.

Division 7: Oriental hybrids

The exotic beauty of the magnificent Oriental lilies is unsurpassed, not only among lilies but in the whole world of flowers. The typical Oriental hybrid is a late-flowering plant with broad alternate leaves. The flowers are usually large and showy, bowl-shaped, flat, or reflexed. Most have a powerful, sweet fragrance.

The preeminent characteristics sought in Oriental hybrids are identical to those required of other lilies: vigor, disease-resistance, and tolerance to virus-that is, the ability to grow well and show no serious symptoms even after being infected. These qualities must be present in lilies chosen as parents. Success is never achieved overnight; several generations were required to eliminate undesirable characteristics and produce today’s superior forms.

‘Empress of Japan’, a huge-flowered, red-spotted gold band lily derived from crossing Lilium x parkmannii with ‘Jillian Wallace’, completed the Empress series. It lacked the virus tolerance of the other clones, however, and it rapidly succumbed to infection.

The Potomac hybrids were also prominent. Produced by Samuel L. Emsweller, they originated from the cross (Lilium auratum x L. speciosum var. punctatum) x L. speciosum.
Oriental hybrids are derived from the following species and their varieties:
  L. alexandrae
  L. auratum
  L. japonicum
  L. nobilissimum
  L. rubellum
  L. speciosum

a: Upright-facing flowers.
b: Outward-facing flowers.
c: Downward-facing flowers.

Division 8: Orienpet hybrids

This new group of hybrids between Orientals and Trumpets or Aurelians (and all the species that have contributed their genes to the common pool) combines the beauty and fragrance of the former with the adaptability and colors of the latter. In climates where summers are too warm for Orientals to thrive, the Orienpets take over, coming into bloom three to four weeks after the Asiatics. They are high performers in gardens from coast to coast across the United States; in Canada, growers in the cold prairie provinces are enthusiastic about their success, though they recommend mulching for winter protection.

Many of the flowers have deeply re-flexed petals with Oriental lily colors while others have the color and character of the regale lilies but with outward, open petals. Most are large plants, often 6.5 – 8 ft. (2 – 2.5 m) tall with 20-60 flowers that are sensational for several weeks in the summer. So far the Orienpets as a group are not very fertile, though many crosses will form embryos without endosperm and this hybrid group is benefiting greatly from the use of embryo culture.

Some of the best of these hardy, beautiful lilies, are ‘Scheherazade’, ‘Northern Carillon’, ‘Silk Road’, ‘Starburst Sensation’, ‘Northern Sensation’ and ‘Leslie Woodriff’.

Orienpet hybrids are derived from the crossing of species and hybrids from Division 6 and Division 7.

a: Upright-facing flowers.
b: Outward-facing flowers.
c: Downward-facing flowers.

Division 9: Species

All true species and their botanical varieties.

Division 10: Miscellaneous hybrids

All hybrids not covered in the above divisions.

Reference

Wikipedia Encyclopedia