near-isogenic lines for maize disease resistance qtl lines for maize disease resistance qtl x donor...

Near-Isogenic Lines for Maize Disease Resistance QTL

x

Donor

Approaches to NIL construction Population of chromosomal segment substitution lines (CSSLs)Recombinant inbred lines (RILs)

self

Heterogeneous inbred families (HIFs)

Introduction: To allow detailed study of quantitative trait loci (QTL), it is necessary to create near isogenic lines (NILs) that differ only for the QTL of interest. In this way, the effects of the QTL can be isolated from other genetic effects. Here we detail the production and analysis to date of NILs that differ for disease resistance QTL.

Repeated selfing

F1 F1

xRepeated random backcrossing

Regions introgressed

QTL identification

Recurrent Parent

NILs derived from identified CSSL outliers

Marker-assisted backcrossing

Backcrossing with recurrent phenotypic selection

38 bins associated with multiple disease resistance QTL were targeted for NIL construction, based on a consensus map of disease QTL in maize (Wisser et al. 2006). HIF- derived NILs were constructed from B73 x CML52 and B73 x DK888. The tropical lines CML52 and DK888 were chosen based on their superior resistance to NLB, GLS, SLB, and other diseases. The NIL pairs are now being characterized for resistance to northern leaf blight (NLB), gray leaf spot (GLS), southern leaf blight (SLB), anthracnose leaf blight (ALB), common rust, and common smut.

NILs derived from heterogeneous inbred families (HIFs)

Acknowledgements: Funding for this work is from the CGIAR Generation Challenge Program, the USDA Agricultural Research Service (ARS), The McKnight Foundation, and the Corn Growers Association of North Carolina.

References: Szalma et al. (2007) Theor. Appl. Genet. 114: 1211-1228. Wisser et al. (2006) Phytopathology 96: 120-129.

a The NLB-QTL was identified from corresponding heterogeneous inbred families in 2005 to 2006, but significant phenotypic contrast was not detected in selected NIL pairs at Aurora, 2007.

b Data based on one-year field trials, and need to be further validated. (Common rust and common smut are from natural infection.)

NILs derived from marker-assisted backcrossing

Major SLB QTLSLB QTL Chr. 1 SLB QTL Chr. 3

B73

NIL pairs inoculated with NLB and ASR

B73 NILs inoculated with SLB in the field

B73 NIL with Chr. 1 introgression B73 NIL with Chr. 3 introgression

NILs derived from backcrossing with recurrent phenotypic selection

u1228 m0371

Chromosome 4

p072u1008b1434nc135

u1669 u1509 b1126u2281 p096 b1265u2054u1142 u1451u1896 u2027u2038b1189u1808

u2041m0321u2285 u1313 u1999 u1101b589 b1890

0.0 50 100 150 200 250 300 350 400 450 500 550 600 650 700

Chromosome 1

Chromosome 2

p96100u2246 u2363b1017b1338m0111

u1756u1261 u2248p109642 b1018 m0401b1831b1036b1138u1080u2372b1329

u1042 b1662 b1940b1520u1252

p101049u1696

AY111236

0.0 50 100 150 200 250 300 350 400 450 500 550 600 650 700

Chromosome 3

u2118u2256p104127 u1886b1325b1523u1057

u2258u2369p099u2000

u2158b2047

u2261 u2264u1773 b1456b1904u1920u2376 u1266b1449 b1047u2266 u2269u2270u2271dupssr17

b1605 u1825 m0251b1108u1273u2276

dupssr33b1182b1496

u1062u1594u1136

0.0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800

Chromosome 5

u1308 u1496 u1781 b105 b1046 u1447 u1355 b1287b1208 m0081 u1853 u1722 p101u2216

p048b2305 b118 AY105910u2307

0.0 50 100 150 200 250 300 350 400 450 500 550 600 650

Chromosome 10

p041u1293u1291 u1152

u2034

u1337p059u1863u1866

p050u1995b1526u1077

u1115 u1506 b1028 u1084b1360 b1185

50 100 150 200 250 300 350 400 4500.0

b1065

Chromosome 8

u1414 b1194 u1913 b1834 b1863 u1457 b1176 b666 b1782 b1031 dupssr14 b1056 b1131

0.0 50 100 150 200 250 300 350 400 450 500 550 600

Chromosome 6

b1043 b426b1371 u1083u1572 AY111964m0241 b1732u1859 p299852 b1740 b1521

b1538nc009

u2324

0.0 50 100 150 200 250 300 350 400 450 500

Chromosome 7

b1367 b2132 u1159 b1094 u1983 b1022b1808b1305 b1070 b1805 b1666 b2259 b1407 p051

0.0 50 100 150 200 250 300 350 400 450 500 550 600

Chromosome 98000.0 50 100 150 200 250 300 350 400 450 500 550-39.0 700 750600 650

u1279 b1724u1867u2393b1810b1583u2335u1596

u1430b244 p061

u1107u2398u1120u1078u1231 u2095u2343u2371

b1191 u1366 b619 b128 u1982 u1277

NC250 Introgression likely derived from B37

NC250 Introgression likely derived from Nigerian

Composite ARb

NC250 Introgression in both NC292 and NC330

NC250 Introgression in NC292

NC250 Introgression in NC330

Unknown no SSR data

Major SLB QTL positions B73/NC250A F2:3population

umc1704

umc1532umc2011bnlg1917

u1636 dupssr19

b2228u1177

b149

0.0 50

a31 b1429u1160 b1484

b1866b652u2227

b2086u1297

u1988u1254u1035 u1122

u1661u1358b1556

b1025u1128p037u1848 m0041u2047u1298 u1431b1671

b1347u1500p265454 u1553u1129u1118 b2123

u1725u2244

100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100

u2053 u1576b594IDP1471IDP4016

500

AA BB CCDD EE

FF GG

HHII JJKK

The sister lines NC292 and NC330 were derived in the 1980s by Don Thompson at NCSU by repeatedly backcrossing a B73 / NC250 hybrid to B73 and selecting for SLB resistance at each generation. The resulting lines are more than 90% B73 genome-derived while retaining much of the original SLB resistance from NC250. We scanned the genomes of NC292 and NC330, and identified the 11 introgressed regions (shown right). We then constructed and tested B73 NILs carrying each of the introgressed regions alone (far right).

CSSLs outliers identified

The TBBC3 population (Szalma et al. 2007) consists of 90 lines with an average 89% B73 constitution. Each line carries a different set of introgressions from the line Tx303. We screened this population for lines that differed significantly in disease resistance from the B73 recurrent parent lines and from the rest of the population.

B73 Tx303 introgression at bin 1.02Tx303 introgression at bin 1.06

B73 NILs inoculated with NLB in the fieldB73 NILs infected with GLS in the field

B73

Tx303 introgression at bin 1.01

DK888 at bin 8.06

B73 at bin 8.06

B73 NILs inoculated with SLB in the field

John Zwonitzer 1*, Chia-Lin Chung 2*, Joy Longfellow 2, Rebecca Nelson 2, Peter Balint-Kurti 11 USDA-ARS and NCSU Dept. of Plant Path., 2 Cornell University Dept. of Plant Path. *Joint First Authors

Regions introgressed

B73 Introgression AB

Introgression BDIntrogression BD

Introgression BGIntrogression G

Introgression K

Introgression GH Introgression CFG

DK888No—NoNoCML52? aNoCML52No

CML52 or B73 (epistasis btw QTL in bin 2.10 and 5.03)

NoCML52? aCML52? aNLB

S11 / DK888

B73 / CML52

Cross of origin

——————8.06NoNoS11 bNoNo—6.05NoNoS11 bNoNo—5.06S11 bNoNoNoDK888 b—5.04NoNoNoNoNo—3.04CML52 bNoNoNoNoNo8.02/03

NLB, rustNoNoCML52 bNoNoNo7.04SLB, ALBNoNoCML52 bNoNoNo6.05NLB, ALB, rustCML52 bNoNoNoNoNo3.06

NoNoNoNoNoNo2.10, 5.03SLBNoNoNoNoNoNo2.04/06

NoNoNoNoNoNo1.07/08SLB, ALBNoNoNoNoNoNo1.06

Smut bRust bASR bALB bSLB bGLS b

Differential in resistance, but causative QTL unknown

Disease resistance (allele conferring resistance)Contrasting regions in available NIL pairs (bin)

B73 at bin 6.05

CML52 at bin 6.05

CML52 at bin 6.05

CML52 NILs contrasting for bin 6.05

DK888 NILscontrasting for bin 8.06

B73 at bin 6.05