fusarium oxysporum [fo] identification - (Nov/21/2007 )
How to identify fo by microscopy. what does the term race means as FO has many races as 0,1A,1B,2,4,5. DOES ANYONE KNOW HOW TO MAKE CARNATION LEAF AGAR.CAN ANY ONE HELP ME.
Hi, as far as i know
Identification of pathogenic races of F. oxysporum f. sp. ciceri has been mostly by use of differential reaction to selected host genotypes.
F. oxysporum Pathotypes have been differentiated into two groups based on the distinct yellowing or wilting syndromes.
As u know the eight races of the pathogen (race 0, 1A, 1B/C, 2, 3, 4, 5 and 6) have been identified by reaction on a set of differential chickpea cultivars. Races 0 and 1B/C induce yellowing symptoms, whereas the remaining races induce wilting.
The eight races have distinct geographic distribution. Races 1–4 have been reported from India, whereas 0, 1B/C, 5 and 6 are found in the Mediterranean region and USA.
Apart from using differential reaction to selected host genotypes, molecular markers like RAPD, RFLP and SSR have been increasingly used to study variability in pathogenic population of F. oxysporum f. sp. ciceri.
though i am not sure of microscopic identification of Fusarium races
Identification of pathogenic races of F. oxysporum f. sp. ciceri has been mostly by use of differential reaction to selected host genotypes.
F. oxysporum Pathotypes have been differentiated into two groups based on the distinct yellowing or wilting syndromes.
As u know the eight races of the pathogen (race 0, 1A, 1B/C, 2, 3, 4, 5 and 6) have been identified by reaction on a set of differential chickpea cultivars. Races 0 and 1B/C induce yellowing symptoms, whereas the remaining races induce wilting.
The eight races have distinct geographic distribution. Races 1–4 have been reported from India, whereas 0, 1B/C, 5 and 6 are found in the Mediterranean region and USA.
Apart from using differential reaction to selected host genotypes, molecular markers like RAPD, RFLP and SSR have been increasingly used to study variability in pathogenic population of F. oxysporum f. sp. ciceri.
though i am not sure of microscopic identification of Fusarium races
Dear GeneDoc.
You used the term differential reaction what does that mean? Could you help me where I cud get the help in studying more about its identification . In general I have studied its growth on different media and it morphological differentiation on different media . But need more help to know more detail about the different races.
sallie
Hi sallie,
Differential reaction to selected host genotypes: means the way the different varieties of particular host behave (or react) when infected with different races of a pathogen.
For eg. in chickpea (Cicer arienitum) there are many varieties and these are infected with different races of pathogens (F. oxysporum fsp. ciceri race1, 2, 3, ....etc). and the different varieties react differently to these various races thus they call it a differential reaction. This test identifies different races of pathogen as each race generates specific symptoms on a particular variety and none on others.
hope this is clear n sorry for delay.
Dear Gene Doc
Thanxs. I really understood 
As you told in your first reply that specific RAPD/RFLP ....markers have been developed Iam also doing the same research on developiong SCAR markers specific to Fusarium wilt. There is breeding studies also to see whether the markers are passed on to further generation.
There's a confusion which I have to ask you as there are many races in FO ciceri therefore its SCAR marker will be different to different races as resistant and susceptibility to a race will be specfic for the different cultivars of chickpea. The resistance to fusarium wilt caused by 1,2 race are oligogenic or monogenic will it hinder in the SCAR development if so how???
sallie
Hi, there are two things here
1. SCAR marker wrt the pathogen
2. SCAR for the host.
ya the resistance to the pathogen is sometimes under oligogenic control in the host, and this shud not affect the SCAR marker in ur pathogen or the other way round also shud be true.
either ways if ur SCAR marker will be for the particular race and not for the resistance mechanism that it shows (i.e. ur not linking the resistance (phenotype) to this marker (genotype).
if u r linking the resistance and marker then u may end up identifying a marker for the resistance.
hope this is ok.......!
Iam dealing with SCAR marker specific to to the resistance to Fusarium wilt caused in Chickpea. Therefore I hve done RAPD studies to analyse the difference between resistant and susceptible varieties . I got a primer which show a difference . now to study in detail shud I have to know the genes which provide resistance to the host .therefore i shud also know the race which iam dealing with cuse resistance due to oligogenic genes or multigenic genes how can I find out this
Hi,
since u r interested in the host resistance you would
1. select a cultivars of ur choice (one resistant & other susceptible)
2. select a pathogen strain which is causing a disease on the susceptible and not on the resistant cultivar.
3. compare the two host genotypes with what ever marker (RAPD, AFLP, ISSR.......etc)
4. pick the differential bands and convert to SCAR.
5. use this on a population generated by crossing these cultivars
6. find if ur identified marker is linked to the resistance trait.
7. if linked then identify the seggregation ratio of the population interms of resistant/susceptible lines this will tell u if its controlled mono/oligogenic.
8. if no linked to resistance then u might have to search for more markers
this is in a nut shell while there are many modifications and specific steps depending on how u want to go ahead.
u cud go thru papers which r related to this, i guess there are many and it wud be clearer then for u.
cheers....!