Yes, there are some genes conferring resistance to rust which are more durable than others. For e.g. Lr34 has been efficient for long. But definitely, I would recommend a combination of several genes/QTLs to ensure a better sustainability.

Thank you Prof. Pierre Devaux. So,  if cultivar have only Lr34, is that sufficient to be durable?

Please let me know which type of rust are interested in. May be the Lr34 has been overcome by the pathogen by now.

Generally, interested in the three wheat rusts (stripe, leaf and stem). Regarding Lr34, certainly is resistance gene to leaf rust. If case Lr34 has not been overcome, does this gene alone provide durability in commercial cultivar? If yes, there is confuse between race specific resistance and durable resistance. Regards

This is hard to tell as it has not been too much used in Europe so far and therefore I don't know whether it can provide sustainability in commercial cultivars. But definitely as I mentioned previously I would combine with additional genes/QTL.

A cultivar with durable resistance to rust  often has several resistance genes. So pyramiding of different resistance genes is a good way to control the disease.

Durability is a quality of a resistance source (gene) that can only be determined after deployment in a broad range of environments (years and locations). Please see Johnson (1981) for a fantastic definition of durable resistance - what it is and what it is not.

There are examples of durable resistance sources that are race specific and other examples that are not. Race-specificity can impact durability in practice, but does not determine durability, per se.

It sounds a bit tautological, but a resistance source is only durable until it is overcome by the pathogen. That may be 3 months or 30 years. Durability can only be determined in retrospect.

https://www.apsnet.org/publications/phytopathology/backissues/Documents/1981Articles/Phyto71n06_567.pdf

Dear Ibrahim, the question is not clear. What do you mean by a durable cultivar? I suppose from the context you mean durable resistance against  leaf rust. There does not exist durable resistance to LR in wheat so far. Any single resistance gene, especially if it works by recognition of an avirulence gene in the parasite, confers durable resistance, which lasts as long as a new pathogen race, either by introgression or parasite evolution, overcomes it. Avirulence genes are loss-of-function mutations, so they mutate easily. Resistance is more durable, if it is based on a number of genes (pyramiding) of if it is polygenic.

I'm sorry Erik, but I must respectfully disagree with your last statement. As far as I am aware, there has been no proof provided that polygenic resistance is more durable than single gene resistance. Lr34 is a single gene that has maintained durable resistance over 100 years of deployment. Where is the evidence for the durability of polygenic resistance?

I'd like to add that I believe that polygenic resistances certainly have the potential to be durable. However, your statement makes it sound as if all polygenic resistance is durable. Currently, there is insufficient evidence to support that claim.

Dear Jack, you are right, there is no proof, that polygenic resistance is more durable than a single gene resistance. I did not make such a claim. It is just a matter of probability, derived from the gene-for-gene concept. If three fully effective resistance genes are combined, than the parasite needs a combination of three complementary virulences to succeed. The evolution of a triple virulent race needs 3 mutations in the parasite, which takes more time than a single mutation. If however such a race is already somewhere present, it can spread and break down the triple resistance very fast. It all depends on the kind of function of the particular resistance gene and the composition of the pathogen population. There are examples  in other crops (barley/mildew), where a single resistance gene (mlo), which does not require recognition, is more durable than any combination of all other known resistance genes. Anyway, I agree strongly with your statements in your first answer.

Hi, Erik:

Respectfully, you actually did make that claim -  "Resistance is more durable, if it is based on a number of genes (pyramiding) of if it is polygenic."

Regardless, I think we are in agreement. In theory, polygenic resistance should be more difficult for a pathogen to overcome just based on probability. My point is that polygenicity is not predictive of durability.

Kind regards,

Erron