polyploidy and hybridization

What is polyploidy?

Polyploidy is the condition of having more than two complete sets of chromosomes in a nucleus.

How frequently does polyploidy occur spontaneously?

It occurs spontaneously at low frequencies.

How can polyploidy be induced experimentally?

by treating dividing cells with spindle inhibitors like colchicine.

From which plant is colchicine derived?

from the bulb of the autumn crocus (Colchicum).

How does colchicine induce polyploidy?

Colchicine disrupts spindle fibers during mitosis and meiosis, causing chromosomes to replicate but not segregate, forming a nucleus with all the chromosomes.

How do autopolyploids differ from diploids?

Autopolyploids have larger cells and are often more vigorous than diploids.

Why might autopolyploids be sterile?

They may be sterile because chromosome pairing during meiosis is disrupted.

Are hybrids between autopolyploids and diploid progenitors fertile?

No, hybrids between autopolyploids and diploid progenitors are typically sterile.

What is an example of an autopolyploid species in British Columbia?

Monkeyflower (Mimulus guttatus) on Queen Charlotte Islands is tetraploid, whereas it is normally diploid elsewhere.

How does the ploidy of Tolmiea menziesii differ by region?

diploid south of the Pleistocene glacial boundary in Oregon and tetraploid north of it, such as in British Columbia.

How do allopolyploids differ from autopolyploids in evolutionary significance?

they are hybrid polyploids, much more important evolutionarily than autopolyploids.

What's characteristic of allopolyploids?

Aare intermediate between the parent species but have fixed heterozygosity.

Why are allopolyploids reproductively isolated from their parent species?

segregational hybrid sterility, where chromosomes fail to segregate normally during meiosis.

How does the formation of allopolyploids contribute to speciation?

Allopolyploids are instant new species due to their reproductive isolation from both parent species.

In which other regions has Tragopogon mirus independently originated?

Northern Idaho, Wyoming, and Arizona.

What are the parent species of Raphanobrassica?

Radish (Raphanus sativus, 2n=2x=18) and cabbage (Brassica oleracea, 2n=2x=18).

sterility of raphanobrassica hybrid and allotetraploid?

hybrid = sterile, allotetraploid - fertile 2n=4x=36.

Why was Raphanobrassica not agriculturally useful?

It had the leaves of a radish and the roots of a cabbage, making it impractical as a crop.

What desirable traits does rye contribute to Triticale?

High lysine content, tolerance to poor soils, and cold weather.

What desirable traits does tetraploid wheat contribute to Triticale?

High yield and high protein content.

What is the sterilty of the hybrid between rye and wheat?

It is a sterile triploid with 21 chromosomes.

How was the sterile hybrid between rye and wheat made fertile?

It was treated with colchicine to produce a fertile hexaploid, triticale 2n=46.

How did the Loganberry originate?

accidental allopolyploid , originated as a spontaneous hybrid between a blackberry and a raspberry, followed by chromosome doubling.

What is the ploidy level and chromosome number of the Loganberry?

allohexaploid with 2n=6x=42 chromosomes.

What is a polyploid series?

based on diploids with the same basic chromosome number (x).

What is an example of a euploid series in plants?

Agropyron species with x=7 form a euploid series with 2n=14, 28, 42, 56, or 70 chromosomes.

What are dysploid series in polyploid complexes?

polyploid complexes based on hybrids between species with different basic chromosome numbers.

What is an example of a polyploid complex based on a dysploid series?

In Stipa, there is a polyploid complex based on diploids with x=5 and x=6.

What is an example of a diploid hybrid species formed through homoploid hybrid speciation?

Helianthus paradoxus originated from a hybridization between H. annuus and H. petiolaris.

Why is Helianthus paradoxus more successful in salty habitats?

H. paradoxus is 5 times as fit in salty habitats than either of its parent species.

What is a transgressive phenotype in hybrid species?

when a hybrid species exhibits traits that are beyond the range of its parent species.

Has anyone demonstrated ‘recombination of habitat characteristics’ in hybrids?

No, reduced competition with the parental species is thought to be the key factor.

How does the introduction of species promote hybridization?

Introducing species outside their natural range allows them to encounter related species and cross.

What is an example of hybridization due to species introduction?

The introduction of Senecio squalidus from Italy to Britain.

Who first studied introgressive hybridization, and in which plant?

Edgar Anderson (1897-1969) first studied introgressive hybridization in irises.

Can a species capture alleles from another species through hybridization?

Yes, a species can capture single alleles from another species, such as in the case of Senecio vulgaris (rayed groundsel).

What is the concept of "syngameon"?

A "syngameon" is a set of hybridizing species, where a species gains adaptive alleles by crossing with related species.

2 factors that promote hybridization?

habaitat and intro of new species

What are the parent species of the Loganberry?

A tetraploid blackberry (Rubus ursinus, 2n=4x=28) and a diploid raspberry (Rubus strigosus, 2n=2x=14).

What are the parent species of Triticale?

Rye (Secale cereale, 2n=2x=14) and tetraploid wheat (Triticum dicoccum, 2n=4x=28).

How is Polyploidy often experimentally induced

in plantbreeding by treating tissues with dividing cells, such
as germinating seeds or shoot tips, with aqueous
solutions of colchicine

What hybrid is formed when Senecio vulgaris and Senecio squalidus cross?

Senecio × baxteri, a sterile triploid with 2n=3x=30 chromosomes

what are the parent species involved in allopolyploid speciation of Tragopogon in the USA?

Tragopogon dubius (2n=12) and Tragopogon porrifolius (2n=12).

What is allopolyploidy?

formation of hybrid polyploids through the combination of chromosomes from different species.

what did radiate gene introgress from?

senecio squadidus

What is homoploid hybrid speciation?

when hybrids between species at the same ploidy level form new species

• create new species without changing the number of chromosomes in the offspring

what is autopolyploidy

doubling without crossing, resemble diploids they were dervied from except larger cells