Fine tuningthe progeny

making good thingseven better

Eric M McGaw

DFID Department forInternationalDevelopment

The progeny shown in this photo was brought aboutthrough cloning. It is the happy result of collaborativeresearch in marker-assisted breeding that promises to resistdisease strains in both India and West Africa. The researchwas conducted by scientists working in various countries,one of whom, Dr Maria Kolesnikova-Allen, is shown herewith a progeny of a different sort � her young daughterAnastasia.

Fine tuning the progeny

making good thingseven better

Eric M McGaw

DFID Department forInternationalDevelopment

© DFID 2001

All rights reserved

This publication was prepared for The Department for International Development(DFID). The views expressed are not necessarily those of DFID.

ISBN 1 84220 021 6

Written and designed by Eric M McGawemcgaw@hd1.vsnl.net.in

Printed by Pragati Offset Limited, Hyderabad, Indiawww.pragati.com

Making good things even better

This is a story of success. But it�s also a story aboutpoverty � or rather the fight against it.

Poverty is a nuisance. Get on an airplane and you findpictures of hungry children pleading for your sparechange. Cross a busy street corner in any country,developed or undeveloped, and you�re assailed foralms. Politicians everywhere run for office swearing towork overtime to help the poor. Massive institutions areset up in the name of poverty alleviation. Povertycommands a lot of attention � and a lot of money.Yet like most nuisances, poverty doesn�t go away. Like

Poverty: anuisance at best,

a tragedy atworst.

Fine tuning the progeny

1

a cold nasty drizzle, poverty hovers with no end in sight.So when something turns up that burns holes throughthe drizzle one tends to take notice. This booklet isabout one such ray of sunshine.

Specifically, it is about astounding success in cropimprovement. Not just any crop, but a crop that sustainslife in the most god-awful places capable of sustaininghuman habitation.

The crop is pearl millet. The success amounts toscientific advances that have cheated the crop�s nastiest

Downy mildew turnsa perfectly decenthead of pearl millet,like the one on theleft, into a perfidiousmass of confusion likethe one on the right.

2

adversaries. Our heroes are teams of scientists workingat four separate institutions in widely different places,all working towards a common goal.

The background

An earlier publication entitled Tempest ina Test Tube, released by DFID in 1998,

told about how four teams of scientists hadworked together to find ways to fine tune andhasten research on downy mildew, a killerfungus-like disease that devastates the crop.Tempest told of wonderful possibilities in thepipeline. This publication is to alert stakeholdersin the fight against poverty that light is nowvisible at the end of that pipeline.

The achievements brought about through tireless andpainstaking research over the past decade are nowavailable for use. The technology heralded in theearlier publication is now on the shelf.

3

The Centre for Arid Zone Studies (CAZS) workshand in glove with the Plant Sciences Programme of theUK�s Department for International Development (DFID).CAZS is located at the University of Wales at Bangor, innorthern Wales.

The Institute of Grassland and Environmental Research(IGER), a UK Government undertaking, located atAberystwyth, on the central Welsh coast.

Thepartners

4

The John Innes Centre (JIC), a private researchfoundation, is located in Norwich, in eastern England. Inthe photo is Dr Mike Gale, Associate Director.

The International Crops Research Institute for theSemi-Arid Tropics (ICRISAT) is one of the 16 FutureHarvest Centres of the Consultative Group onInternational Agricultural Research (CGIAR). Itsheadquarters are located near Hyderabad, AndhraPradesh, in south central India.

5

Streamlining the process

Let�s review what has happened so far. In 1990,the UK�s Overseas Development Agency, now

DFID, decided to support collaborative researchon pearl millet. The scientists involved quicklyfound that the road ahead meant incorporatingdefences against the two main enemies of thecrop: a nasty fungus-like disease called downymildew and drought.

The initialmilestonewas thecreation ofthe firstgenome mapof pearlmillet in1993. Thecollaboratingscientistsaccomplished this by using molecular markers.Molecular markers are like bookmarks, exceptthat they mark strands of DNA instead of pagesin a book. The variations that occur in DNA �the places where you place your markers � arecalled polymorphisms. By diligently usingmarkers to map chromosomal locations suspectedof possessing traits worth cloning, scientists wereable, within a single year, to map genes thatresisted downy mildew.

There are several kinds of DNA markers used in plantscience today. The three most common:

6

The villains:downy mildew(above) anddrought (right).

� RFLPs � restriction fragment lengthpolymorphisms

� AFLPs � amplified fragment lengthpolymorphisms

� SSRs � simple sequence repeats (alsoknown as microsatellites)

So far, more than 600 markers have been developedand mapped. The favoured technique in the beginning

7

Here today, gone tomorrow! Promising hybrids one year, cannonfodder the next. This figure shows the �boom-bust� cycle for pearlmillet hybrids in India since 1950.

The Boom-Bust CyclePearl millet grain in India since 1950

was RFLP, but this requiredmassive amounts of DNA andtook forever. Those were thedark ages of molecularmapping.

Enter the SSR. SSRs are toRFLPs what the microscope isto the magnifying glass. Theydo everything an RFLP can,but they do it faster andcheaper. They require smallamounts of DNA and aremuch easier to move todeveloping countries. By late2000, 100 SSRs had been

developed, and half of them had been mapped.

Using marker-assisted selection (MAS) to map moleculesis especially advantageous because you can improvethe unimprovable. You take a crop�s natural resistanceto a disease and then move beyond that. According tothe principle of natural selection, all organisms,

including diseases, will alwaysseek ways to survive. This meansthat scourges � like downymildew � will invariably find away around the annoyingdefence mechanisms put in placeby pesky scientists who wouldlike nothing better than toannihilate them. The notion ofself-preservation seems fairenough, except that the survivalof this disease means crop failure,and jeopardises farmers� survival.

8

RFLPs vs SSRs

Reproducible

Simple

Based on DNA

hybridisation

Need lots of DNA

Slow and very

time consuming

Expensive

BUT

Information equally

reliable

PCR-based, only need

small amounts DNA

Easily assayed,

quicker and cheaper

More easily

transferable to

laboratories

PLUS

Collecting downymildew spores.

The Welsh connection

Let�s take a look at who these scientists are.Interestingly, two of the four institutions involved in

the pearl millet work are in Wales. Dr John Witcombe,who works at the Centre for Arid Zone Studies atBangor, is concerned with downy mildew disease. Thisis understandable. For several years he was the seniorpearl millet breeder at ICRISAT, which has a globalmandate for the improvement of that crop. Since leavingthat institute in 1990 to join the University of Wales,Witcombe has kept in close contact with his formercolleagues, now his collaborators.

Explaining the pattern of the disease�s development,Witcombe says: �In year one, if a single cross hybridbegins to lose its resistance to downy mildew, it�ssporadic. In year two it becomes common. In year three,if conditions prevail, you�ve likely got an epidemic onyour hands.�

This is why MAS is so important. When a parent line of ahybrid is bred through MAS, resistance to downy mildewcan be incorporated directly into theseeds. If the breeder changes thegenetic composition of the pollinatorparent, that change feeds rapidlyinto the commercial hybrid. Whenthis happens, you find that thedisease-free seed you purchasedthree years ago is now infected.

HHB 67 is an enormously successfuldowny mildew-resistant varietydeveloped by researchers at

9

10

Haryana Agricultural University incollaboration with several partners,including CAZS and ICRISAT. It wasdeveloped several years ago. Accordingto the pattern described in the boom-bustcycle shown on page 7, HHB 67 shouldhave fallen victim to downy mildew bynow. But because resistance has beenbuilt into the variety using MAS, farmerscontinue to clamour for seeds.

In India, vibrant hybrid seed is attractive topoor farmers. They know that the highyields that result from sowing such seedswill benefit them in the end, so they are

willing to invest in seed. But they are doubtful, and forgood reason. What if downy mildew rears its ugly headagain, as it has so many times? Again and again, linesresistant to downy mildew have been identified, only towatch the disease make its triumphant return,devastating farmers� fields in its wake. This is why it is soimportant that the hybrid seed made available by bothprivate and public sources remains disease-free. And it iswhy scientists can never rest on their laurels � they mustcontinue to identify new sources of resistance and toincorporate these into seeds.

But what about Africa, where in some areas pearl milletis literally the only crop that can be cultivated? Africanfarmers, wary of diseases that can wipe out crops infields sown to a single variety, have for centuries hedgedtheir bets by mixing their seed. The result � hardly anydowny mildew, but very poor yields. But the status quois no longer viable. With population booming andavailable farming land becoming ever more scarce,these farmers desperately need better seeds. Traditional

Sudan

Nigeria

Niger

Mali

Senegal

Namibia

Chad

Burkina FasoTanzania

The main pearl milletcountries of sub-Saharan Africa.

11

breeding techniques arehighly unlikely to producethem. MAS and otherbiotechnologicalprocedures are thereforecrucial to improvement offood security in the drycountries of sub-SaharanAfrica � countries wherepearl millet continues tosustain the lives of thepoorest people on the faceof the earth.

Witcombe is fortunate tohave an array of industriousprofessionals on his team atCAZS.

The disease lady

One of the key players at CAZS is Dr Wendy Breese.She and her colleagues infect young plants with

hideous diseases like downy mildew. But they�re not asperfidious as all that � observing the results of deliberateinfection of plants is the best way to identify the genesthat resist the disease.

Breese�s team has evaluated many pearl millet mappingpopulations against downy mildew isolates. In so doingshe strives to ensure that the results she gets arecomparable to what would be obtained under field andgreenhouse conditions in India, where most of theisolates come from. Almost all the samples she screens

The disease lady atwork -- inoculating

pearl millet with downymildew sporangia. The

UK�s quarantineofficials are

understandablyunconcerned about

pathogens indigenousto the tropics.

Julian Bridges, who works with Wendy Breese in Bangor at the Pen yFridd Field Station, inspects a variety of pearl millet plants.

are sent from ICRISAT�s campus near Hyderabad, India.ICRISAT, which has a global mandate to collect andstore seeds of several food crops including pearl millet,has an active breeding programme that produces newresistant populations. The isolates of downy mildewBreese imports into the UK originate from suchgeographically diverse pearl millet-producing regions inAfrica as Senegal, Mali, Niger, Nigeria, Sudan andEritrea.

Although most of the seeds come from ICRISAT,occasionally JIC sends seeds over from Norwich withbuilt-in resistance genes. The results of Breese�sscreening trials are then sent to various locations.

12

Studying a cropindigenous to the drytropics in a place as coldand wet as northernWales may seem a bitironic, but the work isconducted insidelaboratories andglasshouses where theenvironment is controlledto replicate pearl millet�snatural home. The factthat pearl millet is not

Simulating the Sahel --Breese (left) and LynneGilbert (below) in the

glasshouse, Bangor.

13

cultivated in the UK meant that Breese, despite studyingthis cereal for several years, had never seen it growing ina field until she attended a meeting at ICRISAT in 1997.

Back to basics

Scientists at the John Innes Centre fill an importantniche in the collaborative effort to design the basic

tools needed for developing resistance to disease anddrought in pearl millet. Using MAS techniques, JICscientists supply researchers at CAZS, IGER and ICRISATwith basic markers.

JIC has been developing molecular markers on cereals,notably pearl millet, since 1994. What have they got toshow for it? Quite a lot. They developed the first pearlmillet gene map and then linked this to similar maps ofother cereals (page 15). This remarkable map assuresthat the framework is in place to conduct crucialresearch on various food crops, especially cereals. It is

appropriate that such aninternationally significant mapwas developed at JIC. Thescientists who work there area miniature United Nations.Dr Jiahui Zhu, who leads thepearl millet team, is fromChina. His associates includeFrancis Padi, a PhD studentfrom Ghana and SuzanneLindup, a research assistantfrom the UK. The projectleader, Dr Katrien Devos, isBelgian.

14

Padi and Lindupdiscussing theirresearch on tropicalcrops while asnowstorm ragesoutside their JIC lab.

JIC�s Dartboard

The genomic patterns that relate all cereals to a common grass ancestormake this JIC map a formidable piece of work. It traces the genomicsimilarities between various cereals. Comparative mapping of rice, foxtailmillet and pearl millet has demonstrated the relationships between thegenomes of these three cereal crops, and allows us to exploit for pearlmillet improvement genetic discoveries made in any grass species.Importantly, pearl millet is seen as a �bridge� between various cereals.

15

Padi and Lindupdevelop markers.Once this basicwork is done, themarkers aretransferred toother partners.The figure belowshows the extentof distribution ofJIC markers.Although Indiaremains by far thelargest recipient,requests from

Africa and America are increasingly common. One ofthe most important recipients of JIC�s markers is IGER,

16

Padi in the glasshouse.

which uses markers to makeadditional molecular maps, as well asfor conducting trait and QTL analysis.

Studying drought inthe rain

If conducting research on a cerealsuited to the dry tropics in Bangor

seems ironic, what Dr CatherineHowarth and her colleagues do at IGER is doubly so.Howarth�s focus is not disease, but the other principalconstraint to pearl millet production � drought � anagricultural constraint seldom experienced in Wales.

IGER is nestled in a small valley just outside the seasideresort town of Aberystwyth, 50 miles south of Bangor.

The team at IGER focuseson the basic physiology ofpearl millet; specifically,the plant�s responses toabiotic stresses like droughtand heat. Their mission isto identify molecularmarkers associated withthese stresses. Howarth,whose studies include bothseedling heat toleranceand drought tolerance, hasdeveloped field screeningtechniques using MAS as abreeding tool.

17

Jiahui Zhu, pearl milletteam leader at JIC.

Howarth (right) andtechnician Kirsten Skot

in the lab, IGER.

0000 0600 1200 1800 2400 0600

Time of day

60

55

50

45

40

35

30

25

So

ilsu

rface

tem

pera

ture

,C

O

IGER

Rajasthan

How can she develop field screening techniques for atropical plant in a decidedly untropical climate such asthat of Wales? Well, she does what all good scientists dowhen they run up against a brick wall. She cheats. Shecreates her own field indoors. And she does it well. Thefigure below shows how closely Howarth and her

Simulating the Semi-Arid Tropics

Susan Howarth and her team at IGER have pulled out all the stops increating a �virtual Rajasthan� in cold, wet Wales.

18

colleagues have managed toreplicate the field soil surfacetemperature of Rajasthan, theIndian state where farmersdepend most heavily on pearlmillet for sustenance.

One of Howarth�s colleagues isDr Rattan Yadav. Yadav is aplant molecular geneticistwhose in-depth studies ondrought tolerance have obligedhim to spend significant blocksof time in real field conditions atICRISAT�s large research farmnear Hyderabad. Yadav workson identifying markers fordrought tolerence from field testsof mapped populations. Thisprocedure is known asphenotyping. IGER�s work on abiotic stresses startedwith heat.

What�s next on the agenda for Howarth and hercolleagues? They believe genetic differences in theability to obtain phosphorous fromsoils in pearl millet may yieldknowledge of particular value toscientists and farmers in sub-SaharanAfrica, where nutrient-poor soils area primary constraint. She iscollecting samples of PRLT, a pearlmillet line derived from the Iniadimillets of Togo for this purpose.Playing the Africa card is crucial;indeed, it�s what this research is all

IGER�s Rattan Yadavduring a visit to

ICRISAT�s Patancherucampus.

19

Getting the drop onheat stress.

about. In the long run, making an impact on sub-Saharan Africa, where pearl millet is often the only cropthat can be grown, will be the barometer of success.

Bringing it all back home

Although pearl millet is indigenous to Africa, it�s beengrowing in India for hundreds of years. One of the

reasons the founders of ICRISAT decided to set up shopin India was that they sought an environment wherepearl millet was a staple food for millions of poorfarmers.

Arun Sharma is an authority on HHB 67, one of themost successful pearl millet hybrids yet developed.Since August 1998 he has been based at ICRISAT inIndia to work on his PhD thesis, Marker-assistedimprovement of pearl millet downy mildew resistance.

This important work, overseen by Dr Tom Hash,ICRISAT�s principal pearl millet breeder, was completedin 2001. Sharma took advantage of the various tools thathave been developed by an array of partners. To beginwith, he has a great deal of experience with HHB 67because he earned his MSc at Haryana AgriculturalUniversity in northern India, where the hybrid wasdeveloped. Using quantitative trait loci (QTLs) identifiedand developed at IGER, Sharma sought to improve pearlmillet using MAS at ICRISAT. When IGER identifiedgenes in ICMP 451, an ICRISAT line particularlyresistant to downy mildew disease, Sharma got to work.He crossed ICMP 451 with a pollinator of HHB 67 thatwas becoming susceptible to the disease. This variety,H77/833-2, had something else of importance that he

20

wanted to retain in the products hedeveloped � heat tolerance.Producing a line resistant to bothdisease and heat was a laudable goal,and his genetic map has rendered anextremely desirable result.

Although genetic mapping ispowerful, jumping from one cross toanother is a complicated andfrustrating business. Success in plantbreeding may come faster withbiotechnological techniques than withtraditional breeding, but that doesn�tmean it happens overnight. In creatinga genetic map, you first need to understand the targettraits you seek. You then need to line up the appropriatetools you need to conduct precision genotyping. Butyou also need good screening techniques, and for thatyou need good physiology. Hence the specialrelationship between the teams at ICRISAT, with its threedecades of field research, and the three Britishinstitutions previously discussed, with their emphasis onhigh quality of biotechnology and plant physiology.

What’s a QTL?

QTL = quantitative trait locus, a region on a chromosome with

genes controling a quantitative trait.

A quantitative trait is a trait for which the observed variation

is continuous within a population and is due to the segregation

of naturally occurring polymorphic genes, such as plant height,

disease resistance, drought tolerance and yield.

Arun Sharmainspecting his trial at

ICRISAT.

21

Let�s get back to those target traits.

� Seedling heat tolerance� Drought tolerance� Downy mildew resistance� Yield (both grain and fodder)� Stover quality (digestibility)

The danger with cute little lists with convenient bulletpoints like these, however, is that scientists can�t studyone particular trait in isolation. It�s unrealistic. Plantsexhibit or lack various traits, not just one, so scientistsneed to examine the whole package. At IGER, forexample, Howarth and Yadav have found that theycan�t focus exclusively on drought tolerance. Muchuseful information about downy mildew, technically thescientific purview of CAZS, has been brought to light byIGER scientists investigating drought-tolerantpopulations. But research results obtained fromwhatever source is money in the bank. That�s the wholepoint of partnership.

Back at ICRISAT, Dr Maria Kolesnikova-Allen, whoappears on the front cover of this publication, pursues a

0

100

200

300

400

500

600

700

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Nu

mb

er

of

markers

RFLP

AFLP

SSR

Molecular marker development

for pearl millet in the 90s

22

fairly old-fashionedmethodology. Earlier wetalked about the relativeefficacy of SSRs overRFLPs, but whenKolesnikova-Allen, ageneticist from Russia,began her work, no otheralternatives wereavailable.

�RFLP is slower, but morereliable,� she affirms. Sheshould know. The Russianinstitutions where sheundertook her researchare sticklers for exactness.Her PhD thesis, which shesuccessfully defended atMoscow State Universityin April 2001, was entitledMapping new QTLs fordowny mildew resistancein pearl millet. From 1991to 1994, she worked at theVavilov Institute of General Genetics, a part of theprestigious Russian Academy of Science. In 1998, shemoved to the University of Bangor, where Witcombeinfluenced her to focus on pearl millet. She took to thecrop like a duck to water, and eventually found herselfICRISAT, now under the guidance of Hash.

Hash, taking note of Kolesnikova-Allen�s Jobian patience,slyly contrived to have her map out some particularlyagonising crosses. Specifically, he asked her to genotype F2

progeny plants for constructing a new linkage map. The new

Maria Kolesnikova-Allen cramming for her

thesis defence. TomHash was helpful withthe English version, but

had a spot of botherwith the Russian.

23

map will facilitate the mapping of further QTLs for pearlmillet. Hash selected the lines with care. He chose W 504, adowny mildew-susceptible line from Delhi, as the control,and P 310, a popular resistant line from Mali.

Kolesnikova-Allen introduced the crosses and created amap of the F4 progeny individuals. She tested with nineisolates: five from India, for which the phenotyping wasdone by Dr RP Thakur and his ICRISAT associates; andfour from Africa (one each from Mali, Niger, Nigeria andSudan), for which the isolates were done by Breese atBangor. Using her trusty old RFLP techniques, she foundQTLs for the first time in linkage group 3. These wereeffective against the Indian isolates, but not against theAfrican ones. She also found QTLs in linkage groups 1and 4 that proved effective against both.

24

This genetic map ofpearl millet indicateslocations alonglinkage groups 1-7,corresponding to pairsof chromosomes, thatare associated withimportant traits.

It was a small step forward, but a very important one. Itwas clear that the QTLs would not be effective against allisolates, but it was also clear that they would be effectiveagainst most of them � seven of nine, to be exact. Thetrick now is to figure out how to use the QTLs elsewhere.

What�s next on the agenda for Kolesnikova-Allen? She�scurrently working on transferring identified resistanceinto elite lines widely cultivated in India. This work isPromethean in that it can never stop. Downy mildew willeventually overcome whatever defences scientists buildinto pearl millet (usually doing the job in about five years),so QTL work must continue forever. Although her work islargely confined to the laboratory, Kolesnikova-Allen hasenjoyed the opportunity of viewing the crop in the field. �Iworked on pearl millet for four years before seeing it in thefield. I knew its DNA, and once Tom (Hash) sent me somefreeze-dried leaves, but it wasn�t until I got to India in1998 that I saw it growing.�

Perumal Azhaguvel, a research scholar at ICRISATfrom 1999 to 2001, did his PhD research under TomHash and Dr P Rangasamy, Dean of the AgriculturalCollege of Madurai (attached to Tamil Nadu

25

What’s a linkage group?

Short answer: it’s more or less a chromosome.

Longer answer: Suppose you have one bit of DNA that containsmarkers A, B and C; another bit with B, C, D and E; and anotherwith C, D, E, F and G. You can say that A through G is a linkagegroup because the bits all overlap.

For an even longer answer, consult your local biotechnologist.

Agricultural University).Azhaguvel�sassignment was toundertake skeletonmapping andidentification of QTLs foradditional downymildew resistance inpearl millet. To do this,he created a template, aframework for furtherQTL analysis. Heidentified 40 markers

using RFLP in the F2 generation. With the F4 generationin hand, he began phenotyping, using QTLs against sixIndian isolates and two from Africa (one each from Maliand Nigeria). His PhD was awarded by the University ofWales at Bangor for this seminal work. Azhaguvel�sstudies have aroused international attention, and he isnow working in Japan.

DFID fuels the charge

DFID have been supporting important research onpearl millet at all four of the institutions with which

this publication is concerned: JIC, CAZS, IGER andICRISAT. The project in India, called MolecularBreeding of Pearl Millet, has been split into three phases.

1. Selection of parents with particular traits and makingpopulations. The parental lines must differ for thetrait to be mapped, and the populations mustconsist of a group of about 200 progenies from the F4

generation. Status: completed.

Comrades in arms:Yadav, Sharma andAzhaguvel atICRISAT.

26

2. Genotyping and phenotyping. Genotyping refersto the identification of the presence or absence ofmolecular markers and correlating them withperformance (in other words, identifying theQTLs). Phenotyping refers to the identification,through field trials of drought and downy mildewtolerance in pearl millet. This phase drew to aclose in late 2001. Status: nearly completed.

3. Evaluation of the selection criteria for molecularmarkers. Thisproject phase isdue to start inMarch 2002.Markers will beevaluated for theirapplicability todrought anddowny mildew �and also, for thefirst time, to yield.

The molecular breedingteam in India consists ofseveral ICRISATscientists: Tom Hash,Fran Bidinger, MariaKolesnikova-Allen, RPThakur, Rashid Serrajand S Chandra. Non-ICRISAT scientists withvital input in the projectinclude SK Bhatnagar,Project Director for theAll-India CoordinatedPearl MilletImprovement Program at

HHB 67, whichstands for Haryana

Hybrid Bajra � bajra isHindi for pearl millet),

in a farmer�s field inRajasthan. The hybrid

has dominated themarker since its

release.

27

Jodhpur, Rajasthan. Other important collaborators fromIndian universities whose contributions to the DFID-supported research are TNAU�s Dr Fazlullah Khan andHAU�s Dr CR Beniwal, Dr DC Nijhawan and Dr ISKhairwal. These four experienced pearl millet scientists,along with Dr Rangasamy, who was mentionedpreviously in connection with Azhaguvel�s research, allcollaborate in DFID-funded downy mildew resistanceand contig line projects.

The first thing the group undertook was a preliminaryevaluation of the effect of the genomic regions from theline H77/833-2 (the same one Arun Sharma used for hiscross), which is associated with improved yield underterminal drought stress. This was done by creatingtopcross pollinators from sets of 12 mapping populationprogenies. These pollinators maintained a high panicleharvest index under stress. In other words, theyexpressed significant terminal drought tolerance. IGER�sRattan Yadav and ICRISAT�s Fran Bidinger thenidentified a set of randomly selected progenies as acontrol, which they then crossed to 12 male-sterile lines.Finally, the resulting topcross hybrids were evaluated inthe drought nursery.

The hybrids were earlier flowering and produced lessbiomass than the control. In the absence of stress, theywere lower yielding than either the field or random

28

What’s a contig line?

Specifically, it’s biotechspeak for ‘contiguous chromosomesegment substitution line’. Contig lines are created when thegenome of one plant parent is introduced into another incontiguous segments. See the box on page 35 for a goodexample of how contig lines can be put to use.

topcross hybrids, but in the late- and mid-onset stresstreatments, they outyielded both. Across all three stresstreatments, the hybrids had a 6% grain yield advantageover the control, indicating a small but significantresponse to selection for the putative drought tolerancein terminal stress environments.

Because of DFID�s strong focus on poverty, it priortisesresearch on drought. The development of short-duration cultivars is good for poor farmers becausetheir crops can escape end-of-season drought. Thecost of seed is an important consideration for allfarmers, but among the crops cultivable in Rajasthan,pearl millet is by far the cheapest. You need only 5kilograms of millet seeds per hectare, while ricerequires 20 and wheat 100. Is it any wonder poorfarmers go for pearl millet hybrids?

Harvested HHB 67 in Rajasthan. Downy mildew,eat your heart out!

29

30

The risk factor is of course that devastating epidemicsof downy mildew are always a possibility. But thebiotech-generated material now available hasconvinced more and more poor farmers to invest inthe crop. The downy mildew-resistant version of thefarmers� favourite variety is great stuff indeed. It growsthe same. It looks the same. It tastes the same. Thedifference is that it resists downy mildew.

Dealing with poverty

Putting all this into context, how does this scienceresult in improving livelihoods of poor people?

Let�s review.

The goal was to find a way to obviate the devastation ofdowny mildew, the most important disease of a staplecrop of the world�s poorest people.

The first step in this process was to make a molecularmap. Using the map, scientists used a form of MAScalled MABC (marker-assisted backcrossing) to transferresistance into susceptible lines.

The second step was to develop a downy mildew-resistant pollinator. This was accomplished by scientistsat Haryana Agricultural University, who crossed theirpollinator onto an ICRISAT line and obtained a robust,downy mildew-resistant hybrid that matures very earlyand escapes drought. This is the most arduous step inthe process because the scientists have to ensure thateach QTL is backcrossed to the recipient parent. At eachstage they have to check to ensure that the progeniescarry the marker. But as arduous as this may sound, it�s

Facing page: HHB 67,the people�s choice.

Note the downymildew-infected head

in the middle. Thedisease persists, but

does not conquer.

31

far more efficient than traditional breedingtechniques, which require halting everygeneration or two to screen all the progeniesto isolate the backcrosses that carry theresistant genes . MABC is essentially thesame procedure as traditional breeding, butit�s at least twice as fast because all you needto do is check the QTL that�s linked toresistance. The other QTLs can be ignored.One technique simplifies the process furtherby stacking up all the QTLs associated withresistance. This is known as pyramiding.

The result, whether obtained throughbiotechnological methods or by traditionalplant breeding, is the same. The difference is

The road that began in India . . .

. . . will lead to Africa.

32

that with the former you get it in half the time. In thiscase, biotechnologists were able, within two years, tocomplete a job that would ordinarily have taken aboutfive years.

Downy mildew presents a tougher challenge than otherdiseases because it has more than one strain, orpathotype. This makes MABC especially useful. Werethis technique unavailable, you�d have to screen foreach pathotype -- scientists still don�t know how manyvariations down mildew has -- to be certain of identifyingthem all.

The third step was to develop a resistant version of HHB67. This is nearly done. It�s within reach. This is foodsecurity you can bank on. When downy mildew wendsits evil way through the defences put in place by thededicated scientists described herein, it will find newer,stronger, more resistant lines waiting. Score one for thescientists!

Down the road

In for a penny, in for a pound: DFID will surely remainan important investor in this important research. Tom

Hash, the Principal Investigator for the project, hasproposed a novel title for the third phase: Makingmiracles: exploiting marker-assisted methods for pearlmillet improvement. �Miracle� is not a word muchfancied by scientists. It smacks of fantasy and make-believe. But in this case the word is not misused.

The collaborating scientists on this final 3-year phasework for ICRISAT (RP Thakur, Rashid Serraj, Joseph Adu-

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Gyamfi, and S Chandra);HAU (CR Beniwal); andthe All India CoordinatedPearl Millet ImprovementProgramme (SKBhatnagar).

Of particular importancein this phase is theinclusion of Dr Adu-Gyamfi and his team atICRISAT-Kano, Nigeria.Kano is one of the world�s

largest cities within the pearl millet-growing area of theSahel. Of huge significance is that this is the first timethat the a test site within the Sahel will be part of theDFID thrust.

Pearl millet occupies some 27 million hectares of thehottest, driest portions of the tropics and subtropicswhere it provides the most reliable source of grain andstover for hundreds of millions of farming families.

Because the families living in thesemarginal environments are amongthe world�s poorest, pearl milletimprovement is directly related topoverty alleviation.

The partnership in thisremarkably successful onslaughtagainst hunger and poverty willcontinue to advance its marker-assisted improvement technology-- to fine tune the progeny -- andextend the application of itsachievements to Africa.

Science for the Sahel:northern Nigeria isideal for field testingdisease resistance anddrought tolerance inpearl millet. ICRISAT�sKano team, led by DrJoseph Adu-Gyamfi(seated), is keen tojoin the partnership.

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Pearl millet is for the birds

One pest that no one likes to talk about, both because everyoneloves them and because no one can do much about it, is birds.Birds wreak more havoc on pearl millet and sorghum fields than anysingle insect. However, it�s not politically correct to suggest killingthem. Entomologists who devise ways in which to kill insects arerespected. Just imagine the reaction you�d get by suggesting thatornithologists concentrate on murdering our feathered friends. But itwould certainly be appreciated if someone could figure out how tolessen the devastating impact of birds on open-pollinated cerealcrops. Tom Hash, who isa bit of an ornithologisthimself, tried using MASto fiddle the genes ofHHB 67 to come up witha variation that wouldresult in a product withbristled ears. Hemanaged the bristlesseen in the photo andcaused the birds to dineat the plot next doorwhere a bristle-less cropgrew unguarded, but assoon as they gobbled upthat crop, they got stuckinto the bristles. So thatwork needs a bit ofrefinement.

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DFID Department forInternationalDevelopment