Dissecting maize resistance to Aspergillus flavus. Santiago Mideros December 2008

Transcription

1 Dissecting maize resistance to Aspergillus flavus Santiago Mideros December 2008

2 Reports on Resistance Resistance to fungal growth and to accumulation of aflatoxin are considered to be distinct traits Partial Resistance; Quantitative trait H 2 = (multiple locations, years in MS) Is it possible to identify complementary mechanisms (loci) that could be combined to produce superior resistant lines?

3 Selected QTLs Donor Trait Bin Mp313E aflatoxin afl 3 :2.05 afl 5 :4.06 Oh516 aflatoxin ; 2.06; 3.08; 7.06 B73 ear rot Brooks, et. al Crop Sci. 45: 171 Busboom and White 2004 Phytopath. 94:1107

4 Colonization in maize ears 1. Silk 2. Glume 3. Rachis 4. Rachilla 5. Kernel Resistance to colonization on any of these tissues? Smart, et al Phytopathology 80: 1287

5 How to find differences in colonization? Tissue specificity CML69 Mp339 Sc212m Tx303 Components of resistance Latency, sporulation intensity Measurement method Ear rot GUS, GFP, natural mutants Ergosterol qpcr NIR spectroscopy K. Loeffler

6 Tissue Specific Resistance: hypotheses There is natural variation for resistance to infection and colonization of silk and young kernels in maize germplasm. Loci in the genome of the resistant maize inbreds CML322, CML52 and Tx303 confer resistance in maize tissues to A. flavus colonization and infection. Mississippi New York

7 Dissecting maize resistance to A. flavus 1. Tissue specific components of resistance 2. QTL Mapping B73xCML322 RILs population Targeted NILs Tx303 (TBBC3 lines) CML52 (Chia-Lin s)

8 Dissecting maize resistance to A. flavus 1. Tissue specific components of resistance 2. QTL Mapping B73xCML322 RILs population Targeted NILs Tx303 (TBBC3 lines) CML52 (Chia-Lin s)

9 Components of resistance on silk and developing kernels (DvK) assays, 2007 Resistance Component SILK KERNEL P n P n Experiment Source of material Infection Frequency Latent Period ns 31 ns 65 RILs B73xCML322 Aurora ns 62 HIFs B73xCML52 Aurora ns 12 Founders Aurora 2007 ns 4 ns 4 Inbreds Aurora ns 8 Inbreds GreenHouse 5B 2007 ns 8 - NILs Tx303 in B73 GreenHouse 5B RILs B73xCML322 Aurora HIFs B73xCML52 Aurora ns 12 Founders Aurora ns 4 Inbreds Aurora ns 7 Inbreds GreenHouse 5B ns 6 NILs Tx303 in B73 GreenHouse 5B 2008 Lesion Length ns 8 - NILs Tx303 in B73 GreenHouse 5B 2008 Sporulation < RILs B73xCML322 Aurora < HIFs B73xCML52 Aurora < Founders Aurora < Inbreds Aurora < Inbreds GreenHouse 5B < NILs Tx303 in B73 GreenHouse 5B 2008

10 Inbreds Resistance, 2007 Resistant Susceptible Trait Tissue Experiment Oh7B Ki3 M162W Infection Frequency Silk Founders field Mp339 B73 CML247 Mp313E CML322 NC300 CML52 Latent Period Silk Inbreds Greenhouse 5B P BBB IBM262 NC300 Sporulation Silk Inbreds field Tx303 M37W NC358 Mo17 B97 M162W Sporulation Kernel Founders field NC300 IBM262 B73 IBM54 Sporulation Kernel Inbreds field CML322 CML52 B73 Mp313E NC300 Mp339 CML247 Sporulation Kernel Inbreds Greenhouse 5B

11 Inbreds differences in developing kernel (DvK) sporulation NY 2007 Line Mean Line Mean Line Mean NC a B a CML a Mo a IBM a Mp b B ab NC b NC bc M162W 46.4 abc IBM b Mp313E 3.4 bc B abcd B bc Ky abcd CML bc Oh7B 23.8 bcd CML c CML bcd CML cd Oh43E 15.2 cd Tx d M37W 7.4 d NY 2008 Line dti LSM SP NC a NC a Oh7B a P BBB ab P ab Ms ab Mo ab CML ab B ab IBM ab IBM abc Sc212m abc CML abc M37W abc NC abc Il14H abc CML abc B bc B bc Mp bc Tx bc Ky bc Tx c CML c Ky c *tukey

12 Dissecting maize resistance to A. flavus 1. Tissue specific components of resistance 2. QTL Mapping B73xCML322 RILs population Targeted NILs Tx303 (TBBC3 lines) CML52 (Chia-Lin s)

13 LOD QTL for Resistance to Sporulation in Developing Kernels NY 2007 B73xCML322 RILs 10 IBM2 cm Markers Interval Trait Resistant Allele P 3.09 i432 KSP4 B i763 KSP7 B i798 KSP7 B NY 2008 B73xCML322 RILs Series3 arcsp SP GLM Marker

14 More on B73 x CML322 (Coming soon ) New York 07 and 08 Silk: IF, LP, SP, IC (qpcr) Mississippi 08: Kernel: aflatoxin, IC (qpcr) Silk: IC (qpcr) Trait evaluated (data analysis) Trait not yet evaluated

15 Dissecting maize resistance to A. flavus 1. Tissue specific components of resistance 2. QTL Mapping B73xCML322 RILs population Targeted NILs Tx303 (TBBC3 lines) CML52 (Chia-Lin s)

16 Targeted near isogenic lines (NILs) NY 07; CML52 NIL pairs Kernel: SP, IC (qpcr) Silk: IF, LP, SP, IC (qpcr) Green House 08; Tx303 NILs 7.02, 7.03 Kernel: SP, aflatoxin, IC (qpcr) Silk: LP, IC (qpcr) Tx303 NILs Kernel Traits Kernel Sporulation Aflatoxin Line LSM SP (%) log(ppb+1) ng/g B a a TBBC a a TBBC bc ab TBBC bc b Tx c b Tx303 NILs Silk Traits Latent Period IC above IC below Line LSM Mean LSM Mean LSM Mean TBBC a a a TBBC ab a ab TBBC b ab ab TBBC b ab ab TBBC b bc ab TBBC b cd bc Tx b bcd ab B b d c

17 More NIL analysis from 2008 data NY 08; CML52 NIL pairs Kernel: SP, IC (qpcr) Silk: IF, LP, SP, IC (qpcr) NY 08; Tx303 NILs Kernel: SP, IC (qpcr) Silk: IF, LP, SP, IC (qpcr) Mississippi 08; Tx303 NILs Kernel: aflatoxin, IC (qpcr) Silk: IC (qpcr) Tx303 NILs Kernel Traits Days to Sporulation Line inoculation LSM SP TBBC a TBBC b TBBC b B73_ b TBBC bc Sc212m bc TBBC cd TBBC cd B73_ d TBBC de TBBC de TBBC de Tx303_ de Tx e

18 Future QTL analysis: CML322, Tx303 (TBBC3), CML52 Mississippi 2009 New York 2009 Fine mapping F 2 TBBC3-03: Seed increase and genotype in GH Other more appropriate NILs for fine mapping? Characterization and localization of ROS