Quantitative trait loci (QTL) have been identified for drought tolerance of grain yield in pearl millet (Yadav et al. 1999 and 2002). Marker-assisted selection (MAS) is being used to develop improved parental lines by introgression of QTLs into a homozygous inbred line background for the subsequent production of improved hybrids (marker-assisted backcrossing). and by transforming them into topcross pollinator populations that are more heterogeneous than inbred lines. Until - and unless - it is clearly demonstrated that the incorporation of these QTLs into elite breeding lines will significantly enhance the performance ofcultivars based on those lines, the benefits of these QTLs are unlikely to ever reach farmers' fields

Bidinger, F R

Cavan, G P

Hash, C T

Howarth, C J

Serraj, R

Yadav, R S

ICRISAT Open Access Repository

Breese WA, Hash CT, Devos KM and Howarth CJ. 2002.Pearl millet genomics - an overview with respect to breeding forresistance to downy mildew. Pages 243-246 in Sorghum andMillets Pathology 2000 (Leslie JF, ed.). Ames, Iowa, USA: IowaState Press.Devos K M , Pittaway TS, Reynolds A and Gale M D . 2000.Comparative mapping reveals a complex relationship betweenthe pearl millet genome and those of foxtail millet and rice.Theoretical and Applied Genetics 100:190-198.Jones ES, Liu CJ, Gale M D , Hash CT and Witcombe JR.1995. Mapping quantitative trait loci for downy mildew resistancein pearl millet. Theoretical and Applied Genetics 91 : 448-456.Jones ES, Breese WA, Liu CJ, Singh SD, Shaw DS andWitcombe JR. 2002. Mapping quantitative trait loci for resistanceto downy mildew in pearl millet: Field and glasshouse screensdetect the same QTL. Crop Science 42:1316-1323.Kapoor RL, Kakkar PS, Khairwal IS, Bainiwal CR,Nijhawan DC and Yadav HP. 1989. Bajra hybrid HHB 67 - a major break through. Haryana Farming 18:17, 21.Khairwal IS, Ram C and Chhabra AK. 1990. Pearl millet seedproduction & technology. New Delhi, India: Ramesh JainManohar Publications. 224 pp.Kolesnikova M A . 2001. Mapping new quantitative trait loci(QTL) for downy mildew resistance in pearl millet. PhD thesis,Russian National Academy of Sciences, Moscow, Russia.(English and Russian). 266 pp.Liu CJ, Witcombe JR, Pittaway TS, Nash M, Hash CT,Busso CS and Gale M D . 1994. An RFLP-based genetic map ofpearl millet (Pennisetum glaucum). Theoretical and AppliedGenetics 89:481-487.Liu CJ, Devos K M , Witcombe JR, Pittaway TS and Gale M D .1996. The effect of genome and sex on recombination rates inPennisetum species. Theoretical and Applied Genetics 93:902-908.Qi X, Lindup S, Pittaway TS, Allouis S, Gale MD andDevos K M . 2001. Development of simple sequence repeatmarkers from bacterial artificial chromosomes without subcloning.BioTechniques 31:355-361.Sharma A. 2001. Marker-assisted improvement of pearl millet(Pennisetum glaucum) downy mildew resistance in elite hybridparental line H 77/833-2. PhD thesis, Chaudhary Charan SinghHaryana Agricultural University, Hisar, Haryana, India. 131 pp.Yadav RS, Hash CT, Bidinger FR and Howarth CJ. 1999QTL analysis and marker-assisted breeding of traits associatedwith drought tolerance in pearl millet. Pages 211-223 in Geneticimprovement of rice for water-limited environments (Ito O,O'Toole J and Hardy B, eds.). Los Banos, Philippines: InternationalRice Research Institute (IRRI).Yadav RS, Hash CT, Bidinger FR, Cavan GP and Howarth CJ.2002. Quantitative trait loci associated with traits determininggrain and stover yield in pearl millet under terminal drought-stress conditions. Theoretical and Applied Genetics 104:67-83.Improving Pearl MilletDrought ToleranceRS Yadav1 *, FR Bidinger2, CT Hash2, GP Cavan1,R Serraj2 and CJ Howarth1 ( 1 . IGER, Aberystwyth,SY23 3EB, UK; 2. ICRISAT, Patancheru 502 324, AndhraPradesh, India)*Corresponding author: rattan.yadav@bbsrc.ac.ukQuanti tat ive trait loc i ( Q T L ) have been ident i f ied fordrought tolerance of grain y ie ld in pearl mi l le t (Yadav etal . 1999 and 2002). Marker-assisted selection ( M A S ) isbeing used to develop improved parental l ines byintrogression of Q T L s into a homozygous inbred l inebackground for the subsequent product ion of improvedhybrids (marker-assisted back crossing), and by transformingthem into topcross pollinator populations that are moreheterogeneous than inbred l ines. Un t i l - and unless - it isclear ly demonstrated that the incorporat ion of theseQTLs into elite breeding lines w i l l significantly enhance theperformance of cult ivars based on those l ines, the benefitsof these Q T L s are unl ike ly to ever reach farmers' f ields.Three topcross pol l inator populations (TCPs) weredeveloped by selecting and inter-mating individual genotypesf rom w i th in the F2:4 mapping fami l ies of a pearl mi l le tpopulat ion used for mapping Q T L s for drought tolerance(Fig. 1). The three TCPs produced were selected accordingto the fo l l ow ing methods and cri teria:• Marker-assisted selection: genetic composit ion at thedrought tolerance Q T L (to constitute a MAS-basedTCP) ;• Phenotypic selection: f ie ld performance (best 16) inthe drought trials used to ident i fy QTLs (to constitute a phenotype-based TCP) ; andFigure 1. The scheme used to test marker-assisted selection forpearl millet QTLs controlling drought tolerance using topcrosspollinators. Topcross pollinators based on phenotypic andrandom selections are controls for the pollinator based onmarker-assisted selection.I S M N 4 2 , 2 0 0 1 1516 F4 progeniesselected for fieldperformance indrought trials16 random F416 F4 progeniesselected for presenceof drought toleranceQTLsMAS TCPMASTCH1...12 PhenotypeTCH 1 12 Random TCH1.. . 12Random TCPCross with 12 'A'linesPhenotype TCPRecombineCheck for fertility restorationFigure 2. Grain yield performance of pearl millet hybrids madebetween three topcross pollinators and male-sterile line ICMA92777 in a range of summer season drought nursery moistureenvironments, ICRISAT 2001.• A random contro l : a random sample f rom w i th in themapping populat ion (to constitute a random TCP) .The three TCPs were subsequently used as pol l inatorson 12 A- l ines (male-steri le l ines) to produce topcrosshybrids, as shown in Figure 1. Compared to hybrids of thephenotype and random TCPs, the M A S T C P hybrids hadbetter drought tolerance indices and grain yields (F ig . 2)in the drought-stress environments, although they had a lower yields in the irrigated control environment. Selectings imply on the basis of f ield performance under droughtwas ineffective, but M A S was able to produce improvementin this character, wh ich is notor iously d i f f i cu l t to breedfor using conventional methods.Acknowledgments. Th is document is an output f r o m a project (Plant Sciences Research Programme R7375) fundedby the UK Department for International Development( D F I D ) and administered by the Centre fo r A r i d ZoneStudies (CAZS) for the benefit of developing countries.The views expressed are not necessarily those of D F I D .ReferencesYadav RS, Hash CT, Bidinger FR and Howarth CJ. 1999.QTL analysis and marker-assisted breeding of traits associatedwith drought tolerance in pearl millet. Pages 211 -223 in Geneticimprovement of rice for water-limited environments (Ito O,O'Toole J and Hardy B, eds.). Los Banos, Philippines: InternationalRice Research Institute (IRRI).Yadav RS, Hash CT, Bidinger FR, Cavan GP and Howarth CJ.2002. Quantitative trait loci associated with traits determininggrain and stover yield in pearl millet under terminal drought-stress conditions. Theoretical and Applied Genetics 104:67-83.16 I S M N 42, 2001New Molecular Marker Technologiesfor Pearl Millet ImprovementMD Gale1.*, KM Devos1, JH Zhu1, S Allouis1,MS Couchman1, H Liu1, TS Pittaway1, XQ Qi1,M Kolesnikova-Allen2 and CT Hash2 (1 . John InnesCentre, Norwich, UK; 2.ICRISAT, Patancheru 502 324,Andhra Pradesh, India)*Corresponding author: mike.gale@bbsrc.ac.ukAt a t ime when most of the wor ld sti l l v iewed moleculartechnology as a luxury , for use on ly w i t h major staplecrops, a D F I D - J I C - I C R I S A T project anticipated as earlyas 1991 the appl icat ion of molecular diagnostics in thebreeding of orphan crops for developing countries.The f irst molecular marker-based genetic l inkage mapof pearl mi l le t [Pennisetum glaucum (L.) R. Br.] was bui l tw i th restriction fragment-length polymorphisms (RFLPs) ,the marker system of choice in the early 1990s (L iu et al .1994). This map has served as the base for subsequentpearl mi l let marker-based studies at J1C (Busso et al .1996, 2000; Devos and Gale 2000; Devos et al . 2000; L i uet a l . 1996, 1997). The R F L P f ramework in the consensusmap now available (F ig . 1, see pages 18 -19 of this issue)is based on 173 (out of 500 available) mapped PstIgenomic clones f r om inbred l ine T i f t 2 3 D B , wh ich hasnow become the base genotype for pearl mi l le t moleculargenetics. The clones are available as D N A or, in somecases, as D N A sequences, and have been distr ibutedfreely wor ldwide .I C R I S A T was able to bu i ld one of the very earlymolecular marker faci l i t ies in the C G I A R system in theearly 1990s, and has used this faci l i ty for pearl mi l le tdiversi ty assessment (Bhattacharjee et al . 2002), mappingpopulat ion skeleton map construct ion (Azhaguvel 2 0 0 1 ;Kolesnikova-Allen 2001), and marker-assisted backcrossing(Sharma 2001). The markers and maps have also beenused at C A Z S and IGER in the U K , Universi te d 'Orsay inParis, and T i f ton in the U S A , to map and tag genescontro l l ing important traits in the pearl mi l le t crop. Theseinclude downy mi ldew resistance (Jones et al . 1995 and2002; Azhaguvel 2 0 0 1 ; Ko lesn ikova-Al len 2001), fo l iardisease resistance (Morgan et al. 1998), drought tolerance(Yadav et a l . 2002), plant height (Azhaguvel 2001),f lower ing t ime, and the mul t ip le phenotypic changes matoccurred when pearl mi l le t was domesticated - the so-called 'domestication syndrome' (Poncet et al. 2000, 2002).Molecu lar marker technologies have moved on,part icular ly w i th the development of the polymerasechain reaction (PCR) that al lows the rapid and inexpensiveampli f icat ion of small quantities of D N A precisely targetedto known regions. The ampl i f icat ion commences f romsmall lengths of D N A of known sequence known as primers.C o n t r o l L a t e s t r e s s E a r l y s t r e s s5 0 04 0 03 0 02 0 01 0 00M A SP h e n o t y p eR a n d o m

Improving pearl millet drought tolerance

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Improving pearl millet drought tolerance

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