Matthiola incana
Encyclopedia
Matthiola incana is one of several species of stock
. It is known by the common names hoary stock and tenweeks stock. It is a common garden flower, available in a variety of colours.
Other varieties take longer to develop and are treated as biennials. These are often referred to as "Brompton stocks". In cool temperate regions they are generally sown in summer (June and July) to flower in the following spring. The extra trouble of overwintering the plants is compensated by the showy spring floral display. In hard winters there may be some mortality and a well-drained sheltered site suits them best.
Intermediate varieties (sometimes called "East Lothian" stocks as they originated in southern Scotland) may be treated either as annuals or biennials. If treated as annuals they give a fine late summer and autumn display.
form is caused by a recessive
gene variant (allele
) in the homozygous condition. Therefore, according to the Mendelian
laws of genetics, heterozygous single-flowered stocks should "throw" one quarter doubles in their offspring and one third of the singles should be pure breeding singles incapable of throwing doubles.
Selection over the centuries has greatly improved these ratios, resulting in the so-called "ever-sporting" stocks, in which pure-breeding singles are absent and the proportion of doubles is one half or greater. The reason was first worked out by the Danish geneticist Øjvind Winge
. In these varieties, the singleness allele is closely linked
to a pollen-lethal gene. Thus the pollen (male) contribution to seed is always a doubleness allele, while the female contribution is either a doubleness or a singleness allele. The result of this linkage is that doubles and singles are produced in 50:50 ratios and there are no pure-breeding singles.
Furthermore, many modern strains produce doubles in even higher proportions: 60% or even 80%. This is due to generations of selection for further linked viability effects, producing higher mortality of heterozygous singles, relative to homozygous doubles.
Matthiola
Matthiola |R.Br.]]), or stock, is a genus of flowering plants named after Pietro Andrea Mattioli.A cool season annual or perennial. Flowers are singles or doubles in a wide array of colors, very sweet smelling, and often used in bouquets of cut flowers...
. It is known by the common names hoary stock and tenweeks stock. It is a common garden flower, available in a variety of colours.
Main varieties of stocks
Some stocks are grown as annuals (the "Ten-week Stocks"). These varieties are sown in spring (generally from March onwards in colder areas, earlier in regions with mild winters). They give a good summer flower display.Other varieties take longer to develop and are treated as biennials. These are often referred to as "Brompton stocks". In cool temperate regions they are generally sown in summer (June and July) to flower in the following spring. The extra trouble of overwintering the plants is compensated by the showy spring floral display. In hard winters there may be some mortality and a well-drained sheltered site suits them best.
Intermediate varieties (sometimes called "East Lothian" stocks as they originated in southern Scotland) may be treated either as annuals or biennials. If treated as annuals they give a fine late summer and autumn display.
The genetics of "ever-sporting" stocks
Double-flowered stocks are prized by gardeners for their floral display but are sterile. They therefore have to be produced from the seed of single-flowered plants. The double-floweredDouble-flowered
"Double-flowered" describes varieties of flowers with extra petals, often containing flowers within flowers. The double-flowered trait is often noted alongside the scientific name with the abbreviation fl. pl....
form is caused by a recessive
Dominance relationship
Dominance in genetics is a relationship between two variant forms of a single gene, in which one allele masks the effect of the other in influencing some trait. In the simplest case, if a gene exists in two allelic forms , three combinations of alleles are possible: AA, AB, and BB...
gene variant (allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
) in the homozygous condition. Therefore, according to the Mendelian
Gregor Mendel
Gregor Johann Mendel was an Austrian scientist and Augustinian friar who gained posthumous fame as the founder of the new science of genetics. Mendel demonstrated that the inheritance of certain traits in pea plants follows particular patterns, now referred to as the laws of Mendelian inheritance...
laws of genetics, heterozygous single-flowered stocks should "throw" one quarter doubles in their offspring and one third of the singles should be pure breeding singles incapable of throwing doubles.
Øjvind Winge
Øjvind Winge was a Danish biologist and a pioneer in yeast genetics.He was born in the city of Aarhus in Jutland, the mainland of Denmark. After completing secondary school he travelled to the University of Copenhagen to study law but found himself more suited to the biological sciences into which...
. In these varieties, the singleness allele is closely linked
Genetic linkage
Genetic linkage is the tendency of certain loci or alleles to be inherited together. Genetic loci that are physically close to one another on the same chromosome tend to stay together during meiosis, and are thus genetically linked.-Background:...
to a pollen-lethal gene. Thus the pollen (male) contribution to seed is always a doubleness allele, while the female contribution is either a doubleness or a singleness allele. The result of this linkage is that doubles and singles are produced in 50:50 ratios and there are no pure-breeding singles.
Furthermore, many modern strains produce doubles in even higher proportions: 60% or even 80%. This is due to generations of selection for further linked viability effects, producing higher mortality of heterozygous singles, relative to homozygous doubles.