Drought Tolerance of Crops: Progress and Challenges

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1 Drought Tolerance of Crops: Progress and Challenges Dr. Viswanathan Chinnusamy Principal Scientist Division of Plant Physiology IARI, New Delhi

OUTLINE Introduction to drought stress Target

Challenges: o o o MIADE Realistic, accurate and

2 OUTLINE Introduction to drought stress Target Environment Mechanisms of drought tolerance Physiological and molecular genetic basis of drought tolerance Yield stability under drought Challenges: o o o MIADE Realistic, accurate and high throughput Phenotyping Molecular genetics of crop plants

3 Growth Growth ABIOTIC STRESSES Scarcity or excess of essential environmental factors Water - deficit, hypoxia, anoxia Temperature- Low, High Nutrients deficiency, toxicity Light - low, high ph acidity, alkalinity Excess of non-essential environmental factors Ionic toxicity - salinity, alkalinity, heavy metals Air pollution UV-B radiation Quantity of factor Quantity of factor

4 Crop Yield Drought Drought = moisture deficit stress water stress PWP FC Water logging Soil moisture Meteorological drought: Deficit in precipitation over a long term average Agricultural drought: Soil moisture deficit that leads to reduction in growth, development and yield of crops

5 Yield Water availability Target environment FC Terminal Intermittent Water scarcity PWP Crop growth stage Water Availability

6 Drought Stress Tolerance is No More a Myth It is very common to state that drought tolerance is a very complex trait and it is not tractable for genetic improvement. It is often believed that drought tolerance is a nebulous term that becomes more nebulous the more closely we look at it, much as a newspaper photograph does when viewed through a magnifying glass (Passioura 1996). This opinion emerged rather due to a global view of yield response of plants under illdefined experimental conditions or agricultural situations. Hence the results are confusing and non-reproducible. Omics of plant stress response revealed massive change in epigenome, transcriptome, proteome and metabolome in response to drought that further strengthened the opinion that drought tolerance is a very complex trait.

Complex traits are amenable for easy modification GA regulated genes

Yield improvement in green revolution is brought about by single gene

(semi-dwarf1/sd1) and GA insensitivity in wheat (Reduced height/rht).

of drought tolerances in crop plants," says Nguyen.

" Tester is also optimistic: Ultimately, "I think there will be a

7 Complex traits are amenable for easy modification GA regulated genes are more than 1100 in Arabidopsis seedlings. Yield improvement in green revolution is brought about by single gene mutation that resulted in gibberellin (GA) deficiency in rice (semi-dwarf1/sd1) and GA insensitivity in wheat (Reduced height/rht). "Clearly, recently we have seen some very promising advances in terms of drought tolerances in crop plants," says Nguyen. "Now it's a question of how to optimize the system." Tester is also optimistic: Ultimately, "I think there will be a palette of genes from which breeders and crop scientists will select for putting together the drought tolerance for a particular region. (Pennisi E. 2008)

Drought Tolerance Drought Resistance The mechanisms causing minimum loss of yield in a water deficit environment relative to the maximum yield in a water constraint free management of the crop.

8 Drought Tolerance Drought Resistance The mechanisms causing minimum loss of yield in a water deficit environment relative to the maximum yield in a water constraint free management of the crop. Drought Tolerance Drought Tolerance Constitutive mechanisms Acquired mechanisms Dehydration Avoidance Dehydration tolerance Yield Stability GY = WU x WUE x HI where: WU= water transpired by the crop WUE = water use efficiency (=biomass/unit water transpired) HI = harvest index (economic yield/total biomass) Passioura (1977)

9 Drought Tolerance Dehydration Avoidance Dehydration tolerance Water Mining (WU) Minimizing water loss Cellular tolerance WUE & EUW Phenotypic & developmental plasticity Root traits- Morphological & anatomical changes Aquaporins OA Transpiration -Stomata LAI (Leaf area, no. Leaf rolling & drying) leaf reflectance characters (wax load and pubescence, leaf angle, leaf rolling) Metabolic homeostasis Xanthopyll cycle Photorespiration Maintenance respiration Osmoprotection Cell membrane stability Oxidative Stress Mgmt. Stress proteins Activity & Efficiency of rubisco at low Ci Phenology Flowering Development + ABA -CK, Ethylene Recovery, growth, yield + ABA +CK, Auxin, GA,

10 Traits & Genes: Water Mining

06, a major constitutive QTL for root and agronomic traits in maize across water

11 QTLs for Root System Architecture Root-ABA1, a major constitutive QTL, affects maize root architecture and leaf ABA concentration Root-yield-1.06, a major constitutive QTL for root and agronomic traits in maize across water regimes Giuliani et al J Exp Bot. 56: Landi et al J Exp Bot. 61:

12 Root-specific manipulation of single gene expression can increase root traits P WRKY6 ::CKX ox Plant Physiology, May 2010, Vol. 153, pp , CL, Culm length PL, panicle length NP, number of panicles per hill NSP, number of spikelets per panicle TNS, total number of spikelets FR, filling rate NFG, number of filled grains TGW, total grain weight 1,000GW, 1,000 grain weight. NT RCc:OSNAC10

13 Application of omics technologies has contributed to the development of stress-tolerant crops in the field cdna microarray of drought stress response in rice SNAC1 with 5.6 fold enhanced expression was isolated from the upland rice cultivar IRAT109. WT 35S::SNAC1 Hu et al. PNAS USA 103:

14 The hrd-d mutant showed more secondary roots in Arabidopsis

15 Genes for root traits + ABA + Auxin - CK - Ethylene

16 Traits & Genes: Osmotic Adjustment High OA Low OA QTLs for osmotic adjustment in rice Garg et al :

by per plant) Zhang et al., 2002 Rice 7 QTLs located in 5 chomosomal regions. Xu et al.

17 Traits & Genes: WUE Crop No. of QTLs References Wheat 10 QTLs affecting per plant WUE (Total dry matter/ amount of water used by per plant) Zhang et al., 2002 Rice 7 QTLs located in 5 chomosomal regions. Xu et al., 2009 ERECTA, a putative leucine -rich repeat receptor-like kinase (LRR-RLK), known for its effects on inflorescence development, is a major contributor to a 13 C QTL on chr2.

18 ABA pathway engineering: Minimization of water loss & Enhancement of cellular tolerance

19 Traits & Genes: Transpiration control & Cellular tolerance ABA: Water mining Regulate primary root growth; Minimization of transpiration Stomatal Control; Osmotic adjustment regulates gene expression; Cellular tolerance aba2 WT Isomerase/A BA4 vp14 WT WT NCED3-ox ABA2 BG1 WT aao3 90% ~30% RH, 10 min /aba3

20 ABA Signal Transduction Negative regulators and effectors are shown in red for clarity. Colors in boxes represent relative expression level of a gene before and after ABA treatment (+ABA). Plant Cell 16: (2004)

Drought tolerance of rd29a:anti-atftb canola during flowering The DH12075 (a) and YPT2-RD29AantiAtFTP (b) plants were subjected to a 4-day drought

The pictures were taken on day 8 of re-watering after the drought stress Seed yields of WT and transgenic canola in 2003 (a) and 2004 (b) confined

21 Drought tolerance of rd29a:anti-atftb canola during flowering The DH12075 (a) and YPT2-RD29AantiAtFTP (b) plants were subjected to a 4-day drought treatment starting on day 8 after flowering. The pictures were taken on day 8 of re-watering after the drought stress Seed yields of WT and transgenic canola in 2003 (a) and 2004 (b) confined field trials In (a) the solid bars represent seed yields for the twoirrigation condition, and the dotted bars represent seed yields for the one irrigation condition. Irrigation was conducted during the flowering period. Wang et al Plant J. 43:

22 ABA confers dessication tolerance from moss to higher plants Oh et at Arabidopsis CBF3/DREB1A and ABF3 in transgenic rice increased tolerance to abiotic stress without stunting growth. Plant Physiology 138: Red Arrow indicates re-watering

The PP2C and the ABA receptors both belong to highly conserved families of proteins whose

23 Science Breakthrough 2009 Identification of the ABA receptors and its mechanism of action 2009 Science s TOP 10 These results are a boon for plant biology and possibly beyond. The PP2C and the ABA receptors both belong to highly conserved families of proteins whose roles in other organisms may become clearer now that their function in plants has been nailed down

24 Traits & Genes: Transpiration control & Cellular tolerance P ABF3 Hubbard K E et al. (2010) Genes Dev. 24:

25 Overexpression of ABA Receptor enhances drought tolerance

26 Vaccination? Identification of new agonist chemicals Engineered receptors that can be activated by the off-the-shelf agrochemicals Wheat seedlings grown in vermiculite and severely desiccated under drought. The seedling on the right received 0.1 µmol of ABA in the irrigation water before the onset of stress. Control seedlings received normal irrigation water before on the left.

27 Yield stability under field drought stress conditions

28 Reproductive stage stress tolerance Spikelet Fertility Molecular basis of spikelet fertility under drought stress needs to be studied

Regulated Expression of an Isopentenyltransferase

promoter in leaves increases drought tolerance NT

29 Regulated Expression of an Isopentenyltransferase Gene (P SARK ::IPT) in Peanut Significantly Improves Yield Under Field Drought Conditions Expression of IPT in senescence associated promoter in leaves increases drought tolerance NT P SARK ::IPT Qin et al Plant Cell Physiol 52:

30 Plant nuclear factor Y (NF-Y) B subunits improved corn yields under drought Nelson et al PNAS USA 104:

31 Bacterial RNA Chaperones Confer Improved Grain Yield in Maize under Water- Limited Conditions Castiglioni et al Plant Physiology 147:

32 QTL for Yield under drought Bernier J, Kumar A, Ramaiah V, Spaner D, Atlin G (2007). A large-effect QTL for grain yield under reproductive-stage drought stress in upland rice. Crop Sci. 47: Vandana x Way Rarem qtl12.1 This QTL accounted for an increase in grain yield, harvest index, and biomass yield under stress, and it was detected over seasons under field conditions. The QTL accounted for 51% of the genetic variance in yield under drought QTL qtl12.1 increases water uptake in upland rice: Bernier et al Field Crops Research 110: qtl12.1 has a large and consistent effect on grain yield under upland drought stress conditions, in a wide range of environments (21 field trials) Bernier et al Euphytica 166: Kumar R, Venuprasad R, Atlin GN (2007). Genetic analysis of rainfed lowland rice drought tolerance under naturally-occurring stress in eastern India: heritability and QTL effects. Field Crops Res.103: A QTL on chromosome 1 that accounts for 32% of the variation in yield under drought stress in rainfed lowland rice.

33 Trends in Plant Science, June 2011, Vol. 16, No. 6

34 Yang et al Mol Plant 3:

35 Yang et al Mol Plant 3:

36 CHALLENGE - 1 Large scale phenotyping under natural field A OPEN CHALLENGE Controlled environment phenotyping: Phenomics

CHALLENGE - 2 Minimum Information about a Drought Experiment (MIADE) 1. Agronomic conditions of crop culture: Soil type, ph and Ec; nutrition; spacing between plants 2.

37 CHALLENGE - 2 Minimum Information about a Drought Experiment (MIADE) 1. Agronomic conditions of crop culture: Soil type, ph and Ec; nutrition; spacing between plants 2. Soil water status: soil matric potential, amount and interval of irrigation 3. The crop growth stage at which the stress was imposed 4. Duration of stress 5. Plant water status: RWC or water potential and osmotic potential 6. Phenology, Yield and yield components 7. Weather data on rainfall, temperature and VPD

38 1. Genotypes: CHALLENGE - 3 Crop Functional Genomics Rate limiting traits/processes/genes Germplasm Cores Mini-cores Mutants T-DNA/Transposon tagged lines 2. Genomics: OMICS and Bioinformatics 3. Efficient and Easy Transformation Protocols Rate limiting step in gene function validation

39 Yield Yield Component Rate limiting traits/processes/genes Germplasm Phenotyping Mutants Phenotyping Component Traits Pathways Genes Contrasting genotypes Association mapping (LD) WGA Gene cloning QTL Mapping GENES MAS Breeding Transgenics Genotype with improved stress tolerance

40 CHALLENGE - 4 Yet to learn of the alphabets of the stress matrix Potential combinations of environmental stresses that can affect crops in the field

41 Omics Cellular networks Growth models CHALLENGE - 5 Systems biology CHALLENGE - 6 YIELD Collaboration & Translation of research findings in to products

42 Drought tolerance can be improved Drop by drop Gene by Gene Trait by Trait Be SPECIFIC Target Environment, Pyramid Traits? X

43 Thanks One who solves the problem of WATER is worth two NOBEL Prizes one for SCIENCE and one for PEACE - John F. Kennedy viswanathan@iari.res.in

TABLE OF CONTENTS. Abbreviations List of figures List of Tables Acknowledgements Abstract..1-2

TABLE OF CONTENTS. Abbreviations List of figures List of Tables Acknowledgements Abstract..1-2 TABLE OF CONTENTS Abbreviations List of figures List of Tables Acknowledgements Abstract..1-2 Chapter 1: Introduction and Review of literature......3-30 1.1. Introduction: Wheat 1.1.1. Economic importance