It would be necessary to verify the chromosome countings on both populations. If the difference is proved true, you have can be two taxon different. It would then be interesting to verify the morphological characters in search of possible differences. We could explain this difference of chromosome numbers by phenomen as aneuploidy or dysploidy.

i am not sure about why? but such variation has been observed with in the species the example is Muntjacs  sp, (male has a diploid number of 7, the female only 6 chromosomes). 

I am not sure about why. But our group leader found the wild cucumber species (2n=24), and he did interspecific crossing with the cucumber cultivar (2n=14), the F1 must be x=19, with the embryo rescue adn doubling, it became 2n=38, and then by doing self-crossing and backcross with the cucumber cultivar,we got our introgression lines.

It would be necessary to verify the chromosome countings on both populations. If the difference is proved true, you have can be two taxon different. It would then be interesting to verify the morphological characters in search of possible differences. We could explain this difference of chromosome numbers by phenomen as aneuploidy or dysploidy.

Hi

it can have many reasons such as Cytomixis, recombination, translocation and etc.

this site will help you for more information:

http://www.ncbi.nlm.nih.gov/books/NBK21229/

Sometimes karyotype analysis can also explain the change of the chromosome numbers. By comparing the karyotypes of individuals from different populations it is possible to check if there were centromeric breaks leading to an increase or decrease in the total number of chromosomes. In such cases, even if the total numbers of chromosomes are different, one can see that the total number of arms remain the same. See Robertsonian translocations. In these situations the individuals can be considered as different species or yet during the differentiation process.

Thanks dear Researchers, i think, if there is aneuploidy, it is double nullisomy (2n-4) or there is other mutation. Maybe it changes according to being male or female. I have to verify the chromosome variations on both populations. Absolutely this situation will reflect the morphological distinctions. So I have to compare  karyotypes of individuals from different populations. But i dont know which reason is true and what is the effect and what will be new for science ? Is it worth to study? thanks again

Dear all,

The wild boar, Sus scrofa, is also well-known for being polymorphic in terms of chromosome numbers. You find individuals with 2n=36, 2n=37, and 2n=38. The karyotype of the domestic pig contains 2n=38 chromosomes. Within the wild boar, the three types seem to be present in different proportions in different populations. Even better, a study (attached) found the three types within a single litter! 

IMO, it makes sense in terms of evolution. Different taxa display different numbers of chromosomes, so it is expected that you should observe at least some variation within a species, which would form the basis for subsequent evolution. 

Best,

Antoine

Care should be taken to confirm the counts because very small chromosomes can easily be missed out during counting, particularly if there are spatial overlaps. Presence of chromosomes with secondary constrictions and attendant satellites can cause wrong counts, especially where relatively large satellites are wrongly counted as individual chromosomes. If the counts are correct, the variation could have arisen from such events as aneuploidy, dysploidy or recombination involving chromosomal aberrations. A comparison of meiotic chromosomal pairing and disjoining behaviour may help to ascertain which situation may be the case. However, evolutionary mechanisms of karyotype changes could lead to some chromosomes becoming so small that they can hardly be noticed during counting or the reverse. Karyotype analysis and meiotic studies would likely help here provided the taxa are truly similar. Transplant experimentation and systematic studies would show how really close or similar the two taxa are.

Besides chromosome polymorphism, which is quite frequent in some organisms (see above comments), you may also cosider the occurrence of cryptic species in this plant, differing in diploid chromosome numbers.

Frantisek

Counting chromosomes is not good enough. You have to do G-banding and produce a karyotype...using a digital karyotyping system. How many chromosomes are metacentric? How many are acrocentric?

Two acrocentric chromosomes fuse and result in a metacentric chromosome (=Robertsonian translocation). This is the most common change in chromosomal evolution.

Since your number is 34 and the other is 30, you should see more acrocentrics...

I don't think it is aneuploidy, I think it is chromosomal evolution ;-)

Thanks Dear all, firstly i will focus on Robertsonian translocation.Can you give advice to determine this situation with standart karyotype ( i have digital karyotyping system). G banding is necessary ? Thanks 

Regarding the 30-karyotype: Did anyone publish a karyogram (karyotype)? You have to know, how every chromosome looks like to do chromosome analysis.

You have to be sure not to cut metacentric chromosomes into two pieces and falsely classify them as being acrocentric.

I did chromosome analysis in mammals and G-banding was the basic requirement. G-banding and multicolor-FISH is the standard for human chromosomes. I have no experience regarding plant chromosomes. Just check the literature. I am sure there are many protocols out there. Chromosome analysis is not a new technique ;-)

Good luck

Reinhard

of course karyotyping those two populations is needed. and also I think its good if they are really have different chromosome numbers, then it would be good to look at some geographical patterns e.g. altitude differences or climatic/environmental conditions to interpret, I think also checking their hybridization (Poland and Check varieties) would be good to see whether breeding barriers between two populations, if there is, some kind of speciation might going on there etc. following source is one of the most comprehensive to interpret chromosomal differentiation in plant species: Levin 2002, The Role of Chromosomal Change in Plant Evolution, Oxford University Press

you would need to compare karyotypes between 2n=30 vs 2n = 34 to establish homologies and to identify putative homologs/potential sex chromosomes/heterochromatin as well as to identify and characterize the  additional chromosomes found in the 2n=34 population(s); centromere position, size and ultimately banding pattern (chromosomal rearrangements if present) - extra chromosomes maybe B chromosomes in which case you should look at various tissues to assess somatic/meiotic constancy-. As to biological differences search for areas of sympatry to assess if populations remain reproductively isolated- could validate findings thru various molecular genetic approaches wrt synteny (FISH etc)

First chek specimen identificatin. Second check chromosome count. Make karyotyping using C banding (G banding does not work well in plants). If faclities are availabe use FISH. Inreased chromosome numer  by one or two is aneuploidy and can occur by stepwise increase or decrease by nondisjuntion of chromosomes at anaphase or centric fusion. Karyotyping and banding will help. Reading Leven