Transcript Slide 1
Enhancing wheat field performance and response to abiotic stress with novel growth-regulatory alleles Advisory panel Andy Phillips Peter Hedden Steve Thomas Martin Parry Ian Prosser Margaret Boulton John Snape Simon Griffiths Nicholas Harberd Nadia Al-Kaff Andrey Korolev Peter Jack, RAGT Seeds Simon Berry, NickersonAdvanta Mike Gooding, University of Reading John Bingham, farmer and former wheat breeder Mark Dodds, CPB-Twyford Background – there is a need for a greater choice of dwarfing alleles • most UK wheat varieties contain Rht-D1b (Rht2) • semi-dwarf varieties often require growth retardant (chlormequat) treatment for further growth control • altered growing conditions as a result of climate change, reduced N inputs or retardant application may require reoptimisation of dwarfing alleles • the wheat germplasm contains a range of largely uncharacterised dwarfing alleles that might be exploited cv. Maris Huntsman Avalon x Cadenza Background – stress responses are sensitive to gibberellin signalling (and vice versa) DELLA proteins OH O Biosynthesis H GID1 CO HO OH H O Growth responses GA1 deactivation degradation Low GA, high DELLA (RHT) protects against abiotic stress No NaCl 250 mM NaCl rht Rht1 Rht2 Rht3 Rht8 Rht10 Rht12 Objectives • Determine the effect of Rht semi-dwarfing alleles on tolerance to abiotic stresses (JIC) • Characterise the response of the GA-DELLA signalling system to stress (JIC/RRes) • Identify genetic loci responsible for variation in wheat stem height through co-localisation of genes encoding components of GA biosynthesis and signalling with height QTLs (RRES) • Identify allelic sequence variation in GA-DELLA genes and develop intragenic, allele-specific markers for these loci and validate by crossing into elite germplasm (RRes/JIC). • Assess the performance and stress tolerance of the selected alleles (JIC) Approaches – Rht semi-dwarfing alleles and stress tolerance CE, glasshouse, field and polytunnel experiments with Rht NILs Currently plants being grown at two sites (JIC and RRes) and in a polytunnel for monitoring of drought tolerance Traits to be monitored: •Emergence and early vigour •Times to bolting, anthesis and maturity •Architecture •Leaf chlorophyll (SPAD meter) •Canopy temperature and leaf rolling •Yield components •Water use efficiency (carbon isotope discrimination) •N and C assimilation efficiency and partitioning Approaches: response of the GA-DELLA signalling system to stress CPS (1) GGPP KAO (1) GA12 ent-KAURENOIC ACID GA53 GA13ox (0) GA20ox (4) GA20 KO (1) CPP KS (1) ent-KAURENE Bio-active GA3ox (2) GA1 GA2ox (5) Bio-inactive GA8 RHT (1) GID1 (1) GID2 (2) GA-DELLA signalling pathway showing component enzymes/proteins that are potential targets in stress responses. Numbers in parenthesis indicate the number of genes for this component identified in wheat per genome so far. Reference to rice and Brachypodium indicates single copy genes for enzymes early in the pathway and for RHT and GID1, while later biosynthetic and deactivating enzymes are encoded by families of genes. Approaches: response of the GA-DELLA signalling pathway to stress Effects of drought, temperature and salinity on gene expression (qRT-PCR) and on RHT protein stability (antibodies and pRHT::GFP-RHT). Effect of salt on RGA stability in Arabidopsis (Achard et al. Science 311, 91-94, 2006) Approaches: Do GA biosynthesis or signal transduction genes colocalise with height QTLs? Genes are being identified and mapped Parents of mapping populations analysed for polymorphisms using SSCP. Populations: Avalon x Cadenza dh Spark x Realto dh Synthetic x Opata GA2ox Av Ca Sp Ri Op Syn A GA2ox gene was mapped to chromosome 3AS in Avalon x Cadenza 0 cfd79a 5 6 gwm369 wPt-2478 wPt-1688 15 17 18 20 23 25 barc19 wmc505b 2-oxidaseCNFR wPt-9215 STM635acag wmc264 35 wPt-1562 51 gwm155 55 wPt-4725 79 wPt-5133 Underlies a height QTL 2oxCNFR Immediate goals •Assess drought tolerance of Rht NILs in the field •Set up CE experiments to determine effects of drought and temperature stress on GA signalling and plant development •Produce pRHT::GFP-RHT reporter lines •Complete mapping of GA signalling genes •Establish qRT-PCR for transcript analysis of these genes