Dear Pourkhaloee,

'Resistance' and 'tolerance' are the terms used to denote the ability of the plant manage the stress, be it biotic or abiotic. I liked the way  Mirzaghaderi has explained it. Let me explain it further:

Resistance is an absolute term where the plant completely immunize itself to a particular stress. This kind of situation are are observed in case of Biotrophic pathogen (pathogen needing live host to draw nutrient) infection when the host contain a resistance gene and the infecting pathogen contain its corresponding avirulence gene (see gene-for-gene hypothesis, guard hypothesis and decoy hypothesis for further understanding). Typical examples of resistance are observed in diseases like rice blast, linseed rust, insects like brown plant hopper infestation of rice etc. But it does not mean that tolerance can not be obtained in case of biotic stress.

Tolerance is rather a relative term and it is also man made to some extent. In agriculture, tolerance means the plant can be under stress (diseased/ infected/ or physiologically challenged) but the extent of loss does not exceed the ECONOMIC THRESHOLD LEVEL (an extent of loss which do not hamper the economic potential of the produce). Examples of tolerance can be found in case of sheath blight of rice (necrotrophic pathogen that draw nutrient from dead host cells), Yellow stem borer of rice etc. and all the abiotic stresses because these are complex traits are are governed by multiple factors. 

Do you remember our old school days? There were few teachers who did not even allow to revolve our heads during exams and also the were few who did not really mind a little whispering but certainly wouldn't allow to copy from others. The first case is of resistance and the later is of tolerance !!!   

Hope this would be helpful for you. Best wishes.

• I think resistance use for biotic stresses, pest resistance but for abiotic stresses used tolerance.

Dear Pourkhaloee,

I am adding just explanation of what Amit has suggested. The Two terms are use in different context. When we are addressing the question of abiotic stress, we use tolerance as it depends on the physiological capability of the plant to cope with the prevailing stress, and  when the abiotic stress crosses  certain threshold level the plant dies.

For  biotic challenge a plant can be resistant or susceptible. Being resistant  to certain pathogen or pest is the genetic quality of the plant. Even if the plant is not under proper growth condition its quality of being resistance towards certain pathogen will not be challenged.

For example : in salt stress

Salt tolerance may be defined as an inherent ability of plants to withstand the effects of high salt concentrations in the root zone or in the leaves without a significant adverse effect.

Salt resistance may be defined Plant survival under stress through the possession of the mechanisms which reduce the influence of stress as CAM plant

May be this linke useful

http://agritech.tnau.ac.in/agriculture/agri_drought_tolerent_mechanism.html

Dear Pourkhaloee,

'Resistance' and 'tolerance' are the terms used to denote the ability of the plant manage the stress, be it biotic or abiotic. I liked the way  Mirzaghaderi has explained it. Let me explain it further:

Resistance is an absolute term where the plant completely immunize itself to a particular stress. This kind of situation are are observed in case of Biotrophic pathogen (pathogen needing live host to draw nutrient) infection when the host contain a resistance gene and the infecting pathogen contain its corresponding avirulence gene (see gene-for-gene hypothesis, guard hypothesis and decoy hypothesis for further understanding). Typical examples of resistance are observed in diseases like rice blast, linseed rust, insects like brown plant hopper infestation of rice etc. But it does not mean that tolerance can not be obtained in case of biotic stress.

Tolerance is rather a relative term and it is also man made to some extent. In agriculture, tolerance means the plant can be under stress (diseased/ infected/ or physiologically challenged) but the extent of loss does not exceed the ECONOMIC THRESHOLD LEVEL (an extent of loss which do not hamper the economic potential of the produce). Examples of tolerance can be found in case of sheath blight of rice (necrotrophic pathogen that draw nutrient from dead host cells), Yellow stem borer of rice etc. and all the abiotic stresses because these are complex traits are are governed by multiple factors. 

Do you remember our old school days? There were few teachers who did not even allow to revolve our heads during exams and also the were few who did not really mind a little whispering but certainly wouldn't allow to copy from others. The first case is of resistance and the later is of tolerance !!!   

Hope this would be helpful for you. Best wishes.

Tolerance to a stress implies a temporary adjustment to the stress condition. The plant may exhibit physiological responses to counteract the stress response. This character may not be carried over to the next generation.

Resistance usually refers to a genetic mechanism in the plant to counteract the stress. The resistance may be due to already existing genetic makeup of the plant or due to mutation. This can be carried over to next generations.

Interestingly, one possible outcome of multiple stress exposure is that plants that are able to defend themselves facing one stress can become more resistant to other stresses . This phenomenon is called cross-tolerance, showing that plants possess a powerful regulatory system that allows them to adapt quickly to a changing environment . Wounding, for instance, increases salt tolerance in tomato plants . Furthermore, in tomato plants again, localized infection by Pseudomonas syringae pv. tomato (Pst) induces systemic resistance to the herbivore insect Helicoverpa zea . The association between abiotic and biotic stress is also possible , as demonstrated by the reduced infection of tomato by Botrytis cinerea and Oidium neolycopersici following the application of drought stress .

Ozone exposure can induce resistance to virulent Pseudomonas syringae strains in Arabidopsis .Conversely, biotic stress can also interfere to increase the resistance to abiotic stress. This effect is visible when plants are under pathogen attack. Infection may cause stomatal closure to hinder pathogen entry and as a consequence water loss is reduced and leads to an enhanced plant resistance under abiotic stress [39]. Xu and colleagues [40] show that viral infection protects plants against drought stress. Verticillium infection in Arabidopsis plants induced the expression of the Vascular-Related No Apical meristem ATAF and Cup-Shaped Cotyledon (NAC) domain (VND) transcription factor VND7.VND7 induced de novo xylem formation ensuring the water storage capacity and as a consequence,

increased plant drought tolerance . Stress combination induces different signaling pathways, which share some components and common outputs [14–25]. This could help plants to minimize energy costs and create a flexible signaling network [42].

Resistance to both biotic and abiotic stress has been well documented in a variety of crops through priming of defenses. This component of induced resistance can be achieved through specific chemical stimuli like the resistance inducers BABA (beta-aminobutyric acid) or BTH (benzothiadiazole) , genetic manipulation of genes and proteins [45] or by previous contact with a pathogen [46]. Due to the complexity of interactions in defense, in the present review, we aim to focus on the cross-tolerancebetween abiotic and biotic stress as a part of induced resistance for defense.

Hello. I will like to address the matter focusing mostly on abiotic stress, although in biotic stress the following is also applicable. "Tolerance" in abiotic stress is a condition when a plant is "equipped", as in posses the means, to tolerate a stressor.  To tolerate something means exactly not take measures for something that may not pose so much of a direct threat. At least for awhile. "Resistance" implies an active approach to the stressor and has epigenetic implications. It doesn't necessarily mean that the plant deals with something really threatening, but it does suggest that the plant will eventually overcome it. These terms often complement each other: After awhile tolerance may give its place to resistance. Always consider time to be very important. Also, allow me to add that "tolerance" is a condition when the plant can actually take advantage of a stressor, because this stressor takes away all the competition and could paradoxically ensure the species' survival in an ecosystem. On the contrary, in the case of resistance, things become more complicated, as only the most resistant plant will prevail. The problem in this case is at what cost... I mean the most energy consuming way may not be the most effective way, despite survival and epigenetic improvement.

Dear Researchers,

Thank you very much for your helpful comments.

Dear Ali,

I liked Soham Ray's answer. I wish to add that in some classic articles (regarding specifically biotic stress) these terms are defined very simply (e.g., Kover and Schaal, 2002, PNAS 99 (17):11270). Resistance traits are those that reduce the extent of the pathogen infection. Tolerance instead, is defined as the host ability to reduce the effect of the pathogen infection. Some extreme examples: a host can be resistant but not tolerant when in a trial we observe low frequency of infections, but when they occur, the plant dies; conversely, if the plant accession is not resistant (susceptible) and tolerant, when the infection frequency is high, but those infections are not hampering plant fitness or yield. 

Dear Ali 

As to me the most appropriate definition of resistance and tolerance is as explained by Soham Ray's. Let me add albeit detailed explanation of these terms which I directly extracted from a book entitled as "Plant Nematology"  edited by  Perry R.N &  Moens M. (2009). 

‘Resistance’ is a term used to describe one aspect of the outcome of the interaction between a plant and a nematode. In the context of resistant cultivars, it refers to plants that have a phenotype different from at least some of the species, and usually different from the commonly grown crop cultivars. In many cases, resistance is towards one extreme of a range of host efficiency shown by a range of plant genotypes. 

The phenotypic continuum ‘susceptible–resistant’ is a measure of ‘host efficiency’. This is measured by comparing nematode reproduction on a number of host plant genotypes. Those which support no or little reproduction are ‘resistant’; those that allow substantial reproduction are ‘susceptible’. Note that this phenotypic classification is used as an adjective to describe the plant, but is in fact derived from the genetic interaction between plant and nematode. The important practical relevance of this range of phenotypes is that it is possible to propose that resistance be used in crops to control nematode populations.

The other aspect of the interaction is how a nematode affects its host, the ‘tolerant–intolerant (or sensitive)’ continuum. This is a measure of ‘host sensitivity’ and may be determined by assessing plant growth in the presence of the nematode, or in crop terms, measuring yield loss caused by nematodes. In practice, the sensitivity of a single plant usually not only depends upon its genotype but also is related to how many nematodes attack it. At very great nematode population densities, plants suffer measurable growth reduction, whereas when only a few nematodes attack roots most plants grow well. This is of course why we write of nematode management, or more strictly of nematode population management, rather than population control. The objective is to reduce and then maintain nematode populations at densities less than that at which economic crop loss occurs.

I hope it helps!

Awol S. 

Resistance Does not deal with the performance of the host but tolerance does. This is a very general explanation. In narrow, each stress agent has very specific cases. Moreover, resistance of many durable types has become almost the same as tolerance in reaction to the agent and in response to the host performance.

Resistance is more often viewed as an innate capability with which an organism is able to defend itself against the agents of diseases or the outcome of their activities. These capabilities which are usually acquired over time serve as shield to counteract the diseases

On the other hand, Tolerance is adaptive. The organism is able to some acquire physiological or physical adaptive features which enable it to withstand the stress placed on it by the negative environmental factor.

I think Ighere has the right idea. Tolerance implies that a prior exposure/experience has induced or selected for the resistance trait. Resistance is that state in which the response is depressed, for example, in an individual relative to the population. It would seem, then, that resistance could be arrived at by chance or by experience.

Plant tolerance is the characteristic of a plant that allows a plant to avoid, tolerate or recover from attacks from insects, among other things, under conditions that would typically cause a greater amount of injury to other plants of the same species. These inheritable characteristics are what influence the ultimate degree of damage caused by a pest. Tolerance in terms of agricultural production means that despite stress from a pest or disease, the production levels will remain above the economic threshold.

Resistance means that a plant completely immunizes itself from a particular stress.  This is typically a biotrophic pathogen infection. The host has a resistance gene which prevents the proliferation of the pathogen. The pathogen typically contains an avirulence gene which triggers plant immunity.

Source:

ecosystemsunited.com