Many compounds (resistance elicitors) have been shown to increase the resistance of plants to pests and pathogens by priming the resistance response prior to infection. The concept of induced disease resistance to reduce subsequent infection is well established, and recent publications suggest a transgenerational effect (i.e. some degree of increased resistance in offspring of induced plants). Fewer compounds have so far been tested for their ability to induce resistance to abiotic stress eg drought, and the molecular mechanisms of such induced resistance to abiotic stress are still poorly understood. A transgenerational effect (epigenetic modification) of induced drought resistance also occurs (see Tricker et al., 2013). Obvious candidate compounds able to affect resistance to drought are ABA and jasmonic acid as these have been well documented to play a role in signaling in response to abiotic stress. Other examples include (with references at bottom of page):-
ABA + tebuconazole
Horn et al. (2013) showed that simultaneous treatment of Arabidopsis with ABA and the fungicide tebuconazole prior to the onset of drought or salinity stress protected plants from both types of stress.
Takeuchi et al. (2016) showed that treatment with (-)-Abz-E3M induced stomatal closure and improved drought tolerance in Arabidopsis.
Liu et al. (2012) showed that application of alginate oligosacharides to wheat alleviated drought stress meaured by seedling and root length, fresh weight and relative water content.
Bergmann et al. (2013) showed that application of 2-aminoethanol (2-AE) and choline chloride (CC) to barley in pot experiments diminished the effect of drought stress.
Farooq et al. (2012) showed that soaking wheat seed in a solution of ascorbic acid prior to sowing improved drought resistance.
Ambiol® (a derivative of 5-hydroxybenzimazole) increases drought tolerance in tomato seedlings (MacDonald et al. (2009). MacDonald et al. also tested a number of antioxidants such as ascorbic acid, β-carotene, lutein and lycopene.
Jakab et al. (2005) showed that treatment of Arabidopsis with beta-aminobutyric acid (BABA) increased tolerance to drought and salt. Du et al. (2012) showed that BABA application to wheat increased abscisic acid accumulation and increased dessication tolerance but did not increase yield. Sós-Hegedűs et al. (2014) showed that soil drenched with BABA at a final concentration of 0.3 mM improves the drought tolerance of potato.
Cho et al. (2008) described the induced tolerance to abiotic stress in Arabidopsis caused by the rhizobacterium Pseudomonas chlororaphis O6 and suggested it was largely due to the production of the volatile compound 2R,3R-butanediol. Cho et al. (2014) provided evidence that nitric oxide and and hydrogen peroxide production are involved in systemic drought tolerance induced by 2R,3R-butanediol in Arabidopsis.
Hao et al. (2013) showed that exogenous applied coronatine improved drought tolerance in soybean by modulating antioxidant systems and membrane stability to maintain higher photosynthetic performance.
Yao (2010) reported on the work of John Burke that application of cytokinins to cotton can increase yields in water-limited conditions.
Shakirova et al. (2016) used 24-epibrassinolide as a pre-sowing seed treatment in two wheat cultivars differeing in drought tolerance.
Nahar et al. (2015) showed that exogenous glutathione to mung bean (Vigna radiata) seedlings enhanced some of the components of the antioxidant and glyoxalase systems.
Ma et al. (2007) and Agboma (2007) showed that foliar application of glycinebetaine improved growth of drought-stressed tobacco plants
Guler and Pehlivan 2016 showed that exogenous low dose application of hydrogen peroxide enhances drought tolerance of soybean.
Fumigation with H2S was shown by Jin et al. (2012) to stimulated the expression of drought-associated genes in Arabidopsis. Seedlings treated with NaHS (an H2S donor) showed a higher survival rate and a reduction in size of the stomatal aperture compared to controls.
Lee and Back (2016) investigated the effect of 2-hydroxymelatonin on rice seedlings and showed that it alleviated the effect of simultaneous abiotic stress (cold and drought).
Hydroxyproline-containing diketopiperazines (HPCDs)
HPCDs such as L-hydroxyprolyl-L-proline anhydride and L-hydroxyprolyl-L-leucine anhydride were shown to induce resistance to water stress in rice caused by sodium chloride or mannitol (Ienaga et al., 1990).
Jaleel et al. (2007) showed that ketoconazole (a fungicide and plant growth regulator) treatment resulted in partial mitigation of drought stress in Catharanthus roseus.
Filippou et al. (2015) showed that kresoxim-methyl primes Medicago truncatula against abiotic stress such as drought.
Park et al. (2014) reported using mandipropamid, an ABA related compound, to increase drought tolerance. See also news item.
A systemic insecticide shown by Han et al. (2010) to increase tolerance to drought in tobacco and red pepper.
Described as a growth regulator and herbicide was shown by Silim et al. (1993) to induce drought resistance in seedlings of several conifers viz western red cedar (Thuja plicata), yellow cedar (Chamaecyparis nootkatensis), and white spruce (Picea glauca). Mefluidide caused an accumulation of ABA in all three species possibly providing an indication of its mode of action.
Zhang et al. (2012) showed that long term exogenous application of melatonin to soil reduced effects of drought on apple. [Not an elicitor mode of action but still an interesting idea].
Liao et al. (2012) examined the effects of nitric oxide and hydrogen peroxide on adventitious rooting in marigold (Tagetes erecta L.) under drought stress and showed optimal concentrations were 10 μM of the nitric oxide donor sodium nitroprusside and 600 μM H2O2. Nitric oxide or H2O2 increased leaf chlorophyll content, chlorophyll fluorescence parameters, and hypocotyl soluble carbohydrate and protein content, while decreasing starch content.
Ocimum sanctum leaf extract
Pandey et al. (2016) reported that O. sanctum leaves are enriched for antioxidant compounds and application of O. sanctum extract increased expression of dehydrin genes in drought stressed rice plants.
Fernández et al. (2006) suggested that paclobutrazol increased root-to-shoot ratio and stomata density, decreased leaf area reduction, and affected fine roots which might allow the plants to tolerate drought after transplanting.
The 36 kDa protein PeaT1 isolated from Alternaria tenuissima has been shown to increase drought tolerance, salt tolerance and resistance to Botrytis cinerea in Arabidopsis (Abstract on internet).
A 36 kDa protein elicitor isolated from Botrytis cinerea strain BC-4-2-2-1 and shown by Zhang et al. (2010) to promote wheat seedling growth and to increase wheat seedling drought resistance. The protein also induced resistance of tomato to gray mould infection. The protein induced phenylalanine ammonia-lyase, peroxides, and polyphenol oxidase.
Goswami et al. (2013) showed that treatment of rice seed with 5% PEG improved seed germination and subsequent seedling growth under drought conditions.
Gupta et al. (2013) sprayed putrescine (0.1 mM) and benzyladenine (0.05 mM) on to the aerial parts of wheat (HD 2329) and showed that putrescine and benzyladenine treated plants had an increased yield under conditions of water stress.
Okamoto et al. (2013) showed that quinabactin, a sulfonamide ABA agonist, elicits guard cell closure, suppresses water loss, and promotes drought tolerance in adult Arabidopsis and soybean plants.
Kang et al. (2012) showed that pretreatment with salicylic acid for 3 days enhanced the growth and tolerance to subsequent drought stress (PEG-6000, 15%) in wheat seedlings.
Ahmed et al. (2013) reviewed evidence on the ability of silicon to increase tolerance of wheat to drought. Balakhnina & Borkowska (2013) have also reviewed the effects of silicon on plant resistance to environmental stress. Saud et al. (2014) showed that silicon increased the tolerance of Poa pratensis (kentucky bluegrass) to drought.
Asare-Boamh et al. (1986) showed that triadimefon, a fungicide with plant growth regulating properties, reduced transpiration and protected bean (Phaseolus vulgaris) plants from water stress.
Percival & Noviss (2008) tested a number of triazoles for their ability to alleviate the effects of drought when applied to horse chestnut (Aesculus hippocastanum) after a 2 week drought. They showed that the magnitude of treatment effects was in the order epixiconazole and propiconazole > penconazole > paclobutrazol > myclobutanil.
Marshall et al. (1991) showed that ABA and paclobutrazol protected 20 week old seedlings of jack pine (Pinus banksiana) from drought.
Many compounds differing markedly in their chemistry have been shown to ameliorate the effect of drought when applied as an exogenous spray to a wide range of plant species. This suggests that there could be many more compounds which have similar effects. There is potential for these compounds to affect yield when crops are moderately drought stressed in addition to perhaps making the difference between plants surviving a period of intense drought stress or dying.
A wide range of compounds are active in priming resistance to disease with some compounds being more effective with some Genera than others. A similar result should be expected with compounds enhancing drought tolerance ie compounds being more effective on some crops than others,
There is also potential to breed for an enhanced response to these compounds as well drought tolerance per se.
References for drought resistance elicitors
Agboma PC, Peltonen-Sainio P, Hinkkanen R, Pehu E. 2007. Effect of foliar application of glycinebetaine on yield components of drought-stressed tobacco plants. Experimental Agriculture 33, 345-352.
Ahmed M, Kamran A, Asif M, Qadeer U, Ahmed ZI, Goyal A. 2013. Silicon priming: a potentil source to impart abiotic stress tolerance in wheat: a review. Australian Journal of Crop Science 7, 484-491.
Asare-Boamh NK, Hofstra G, Fletcher RA, Dumbroff EB. 1986. Triadimefon protects bean plants from water stress through its effects on abscisic acid. Plant Cell Physiol 27, 383-390.
Balkhnina T, Borkowska A. 2013. Effects of silicon on plant resistance to environmental stress: a review. International Agrophysics 27, 225-232.
Bergmann H, Machelett B, Leinhos V. 2013. Effect of natural amino alcohols on the yield of essential amino acids and the amino acid pattern in stressed barley. Amino Acids 7(3):327-31.
Cho SM, Kang BR, Han SH, Anderson AJ, Park J-Y, Lee Y-H, Cho BH, Yang K-Y, Ryu C-M, Kim YC. 2008. 2R,3R-butanediol, a bacterial volatile produced by Pseudomonas chlororaphis O6, is involved in induction of systemic tolerance to drought in Arabidopsis thaliana. Molecular Plant-Microbe Interactions 21, 1067-1075.
Cho SM, Kim YH, Anderson AJ, Kim YC. 2014. Nitric oxide and hydrogen peroxide production are involved in systemic drought tolerance induced by 2R,3R-butanediol in Arabidopsis. Plant Path J 29(4), 427-34.
Du YL, Wang ZY, Fan JW, Turner NC, Wang T, Li FM. 2012. β-Aminobutyric acid increases abscisic acid accumulation and desiccation tolerance and decreases water use but fails to improve grain yield in two spring wheat cultivars under soil drying. J Exp Bot Aug 1.
Farooq M, Irfan M, Aziz T, Ahmad I, Cheema SA. 2012. Seed priming with ascorbic acid improves drought resistance of wheat. Journal of Agronomy and Crop Science. 22 May.
Fernándeza JA, Balenzateguia L, Bañóna S, Francoa JA. 2006. Induction of drought tolerance by paclobutrazol and irrigation deficit in Phillyrea angustifolia during the nursery period. Scientia Horticulturae 107, 277-282.
Filippou P, Antoniou C, Obata T, Van Der Kelen K, Harokopos V, Kanetis L, Aidinis V, Van Breusegem F, Fernie AR, Fotopoulos V. Kresoxin-methyl primes Medicago truncatula plants against abiotic stress factors via altered reactive oxygen and nitrogen species signalling leading to downstream transcriptional and metabolic readjustment. J Exp Bot Dec 27.
Goswami A, Banerjee R, Raha S. 2013. Drought resistance in rice seedlings conferred by seed priming : role of the antioxidantdefense mechanisms. Protoplasma Feb 27.
Guler NS, Pehlivan N. 2016. Exogenous low-dose hydrogen peroxide enhances drought tolerance of soybean (Glycine max L.) through inducing antioxidant system. Acta Biol Hung 67, 169-83.
Gupta S, Agarwal VP, Gupta NK. 2013. Efficacy of putrescine and benzyladenine on photosynthesis and productivity in relation to drought tolerance in wheat (Triticum aestivum L.). Physiol Mol Biol Plants Oct;18(4):331-336.
Han S-H, Kim C-H, Lee J-H, Kim I-S, Kim Y-C. 2010. Induced drought tolerance by the insecticide imidacloprid in plant. Korean Journal of Environmental Agriculture 29, 159-164.
Hao L, Wang Y, Zhang J, Xie Y, Zhang M, Duan L, Li Z. 2013. Coronatine enhances drought tolerance via improving antioxidative capacity to maintaining higher photosynthetic performance in soybean. Plant Sci 210, 1-9.
Horn R, Chudobova I, Hänsel U, Herwartz D, Koskull-Döring PV, Schillberg S. 2013. Simultaneous treatment with tebuconazole and abscisic acid induces drought and salinity stress tolerance in Arabidopsis thaliana by maintaining key plastid protein levels. J Proteome Res Feb 5.
Ienaga K, Nakamura K, Kurohashi M, Nakanishi T, Ichii T. 1990. Hyroxyproline-containing diketopiperazines inducing drought resistance in rice. Phytochemistry 29, 35-39.
Jakab G, Ton J, Flors V, Zimmerli L, Métraux JP, Mauch-Mani B. 2005. Enhancing Arabidopsis salt and drought stress tolerance by chemical priming for its abscisic acid responses. Plant Physiol 139, 267-74.
Jaleel CA, Manivannan P, Sankar B, Kishorekumar A, Gopi R, Somasundaram R, Panneerselvam R. 2007. Induction of drought stress tolerance by ketoconazole in Catharanthus roseus is mediated by enhanced antioxidant potentials and secondary metabolite accumulation. Colloids and surfaces B; Biointerfaces 60, 201-206.
Jin Z, Shen J, Qiao Z, Yang G, Wang R, Pei Y. 2012. Hydrogen sulfide improves drought resistance in Arabidopsis thaliana. Biochemical Biophysical Research Communications 414, 481-6.
Kang G, Li G, Xu W, Peng X, Han Q, Zhu Y, Guo T. 2012. Proteomics reveals the effects of salicylic acid on growth and tolerance to subsequent dDrought sStress in wWheat. J Proteome Res Oct 29.
Liao WB, Huang GB, Yu JH, Zhang ML. 2012. Nitric oxide and hydrogen peroxide alleviate drought stress in marigold explants and promote its adventitious root development. Plant Physiol Biochem. Jun 17;58C:6-15.
Liu H, Zhang YH, Yin H, Wang WX, Zhao XM, Du YG. 2012. Alginate oligosaccharides enhanced Triticum aestivum L. tolerance to drought stress. Plant Physiol Biochem 62C:33-40.
Ma XL, Wang YJ, Xie SL, Wang C, Wang W. 2007. Glycinebetaine application ameliorates negative effects of drought stress in tobacco. Russian Journal of Plant Physiology 54, 472-479.
MacDonald MT, Lada RR, Robinson AR, Hoyle J. 2009. Seed preconditioning with natural and synthetic antioxidants induces drought tolerance in tomato seedlings.HortScience 44, 1323-1329.
Marshall JG, Scarratt JB, Dumbroff EB. 1991. Induction of drought resistance by abscisic acid and paclobutrazol in jack pine. Tree Physiology 8, 415-421.
Nahar K, Hasanuzzaman M, Alam MM, Fujita M. 2015. Glutathione-induced drought stress tolerance in mung bean: Coordinated roles of the antioxidant defense and methylglyoxal detoxification systems. AoB PlantsJuly 1.
Okamoto M, Peterson FC, Defries A, Park SY, Endo A, Nambara E, Volkman BF, Cutler SR. 2013. Activation of dimeric ABA receptors elicits guard cell closure, ABA-regulated gene expression, and drought tolerance. PNAS July 1.
Pandey V, Ansari MW, Tula S, Sahoo RK, Bains G, Kumar J, Tuteja N, Shukla A. 2016. Ocimum sanctum leaf extract induces drought stress tolerance in rice. Plant Signal Behav Feb 18.
Park SY, Peterson FC, Mosquna A, Yao J, Volkman BF, Cutler SR. 2015. Agrochemical control of plant water use using engineered abscisic acid receptors. Nature Feb 4.
Percival GC, Noviss K. 2008. Triazole induced drought tolerance in horse chestnut (Aesculus hippocastanum). Tree Physiol 28, 1685-92.
Saud S, Li X, Chen Y, Zhang L, Fahad S, Hussain S, Sadiq A, Chen Y. 2014. Silicon application increases drought tolerance of kentucky bluegrass by improving plant water relations and morphophysiological functions. ScientificWorldJournal 2014:368694. doi: 10.1155/2014/368694.
Shakirova F, Allagulova C, Maslennikova D, Fedorova K, Yuldashev R, Lubyanova A, Bezrukova M, Avalbaev A. 2016. Involvement of dehydrins in 24-epibrassinolide-induced protection of wheat plants against drought stress. Plant Physiol Biochem 108, 539-548.
Silim SN, Guy RD, Lavender DP. 1993. Mefluidide-induced drought resistance in seedlings of three conifer species. Canadian Journal of Botany 71, 1087-1092.
Sós-Hegedűs A, Juhász Z, Poór P, Kondrák M, Antal F, Tari I, Mauch-Mani B, Bánfalvi Z. 2014. Soil drench treatment with B-aminobutyric acid increases drought tolerance of potato. PLoS One Dec 9;9(12):e114.
Takeuchi J, Okamoto M, Mega R, Kanno Y, OhnishiT, Seo M, Todoroki Y. 2016. Abscinazole-E3M, a practical inhibitor of abscisic acid 8'-hydroxylase for improving drought tolerance.Sci Rep 6: 37060.
Tricker P, Rodríguez López C, Hadley P, Wagstaff C, Wilkinson M. 2013. Pre-conditioning the epigenetic response to high vapor pressure deficit increases the drought tolerance of Arabidopsis thaliana. Plant Signal Behav Oct 1;8(10).
Wang P, Sun X, Li C, Wei Z, Liang D, Ma F. 2012. Long-term exogenous application of melatonin delays drought-induced leaf senescence in apple. J Pineal Res. Oct 1.
Yao S, 2010. Plant hormone increases cotton yields in drought conditions. News & Events, ARS, USDA.
Zhang Y, Yang X, Liu Q, Qiu D, Zhang Y, Zeng H, Yuan J, Mao J. 2010. Purification of novel protein elicitor from Botrytis cinerea that induces disease resistance and drought tolerance in plants. Microbiol Res 165, 142-51.
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