I have several ryegrass cultivars infected with (E+) and without endophyte (E-)under two water regimes. If I detect an main effect of endophyte on the plant yield but not an interaction between endophyte and water regimes, will one say endophyte has an effect on drought tolerance of the host?
I found in the published research that when people say endophyte infection improved drought tolerance, it refers to there is no difference between E+ and E- plants under irrigated conditions but E+ improved yield or other physiological traits compared to E- plants under drought. However, if endophyte infection improved yield or other physiological traits under both irrigated and non-irrigated conditions, will one still consider endophyte infection improves the drought tolerance of the host?
Here you have to use the controls properly, I think you should test E+ and E-both under irrigated and water stress condition.
If E+ is better at irrigated condition than E-, it is not unusual that E+ is better than E- at water stress condition.
Some use PEG screening methods in vitro to select endophytes that are tolarent to water limiting conditions although it is also controversial.
I think that measurements must be done by evolution of protein level, because the of endophitic are diazotrofic ones. Therefore, the "work" of them can be done by N level, or better by protein level inside them.
Hi Lulu, It's not uncommon for genotypes that perform well under moisture deficit to also perform well under irrigated conditions. A.R. (Tony) Fischer wrote a paper on wheat in 1978 (Aust. J.Ag. Res, ?) assessing wheat lines for drought tolerance and part of his index (if I remember correctly) related their yield under moisture deficit to their irrigated yield. It hasn't been easy to demonstrate that E+ consistently improves drought tolerance although the evidence is gradually accumulating that it does. Chuck (CP) West has shown that E+ tends to be associated with greater levels of osmotic adjustment & this might assist biomass production under water deficit. How you want to measure 'drought tolerance' will be related to what strategy you think the plant employs to cope with deficit. If you think that it is dehydration tolerance then I'd advise you employ the method of Volaire & Lelievre (2001, Plant & Soil). Volaire & I took this method a bit further to rate dehydration tolerance in 3 grass species in a Crop & Science paper (attached) & it would be interesting if you applied this methodology to your question. What do you think? Cheers Mark
Dear Lulu,
To answer your first question : If you have significant effect of an endophyte on plant yield, and no interaction between endophyte and water regimes, you can look at the main factor effects, in your example improvement in yields of the plants grown under stress conditions is due to endophyte inoculation (or simply put, plants grown under stress and inoculated with endophyte had significantly higher yield compared to un-inoculated control plants.)
the second question: if an endophyte infection improved yield or other physiological traits under both irrigated and non-irrigated conditions, will one still consider endophyte infection improves the drought tolerance of the host? Yes, it is common that plants infected with endophytes overall perform better, both under optimal and stress conditions.
best,
Hello, Mark. Thank you so much for your answer. Actually, I was not aiming to investigate dehydration tolerance. In my experiment, I measured some plant morphological and physiological traits of both irrigated and non-irrigated plants, and tested the effects of endophyte on these plant traits. In your opinion, if endophyte changes these plant traits but independent from water availability (i.e. only main endophyte effect and no interactions between endophyte and water availability), will you conclude endophyte had impacts on drought tolerance?
Thank you very much.
Cheers
Lulu
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