Breeding for MLN tolerance CIMMYT Africa

Biswanath Das, Yoseph Beyene, Stephen Mugo, Manje Gowde, Dan Makumbi, Mike Olsen and BM Prasanna

MLN Diagnostic Workshop, Naivasha 17th to 19th March 2015

CIMMYT’s Collaborative Global Maize Program (GMP)

GMP Focus: • Maize Breeding for the tropics where maize is an important food crop

CIMMYT’s MISSION: To sustainably increase the productivity of maize and wheat systems to ensure global food security and reduce poverty.

30,000 accessions in the CIMMYT genebank –enormous source of genetic diversity.

CIMMYTNARS

GMP Target TraitsAbiotic Stress • Drought • Poor soil fertility/N• Heat• Acid soils• Waterlogging

Biotic Stress • Diseases (Turcicum, GLS, Maize Lethal Necrosis, MSV, Ear rots)• Insects (Stemborers, post harvest pests (weevils, grain borers) • Striga (parasitic weed)

Nutrition (QPM, VitA)• Host R is just one

component of an IPM system

Varieties are screened for all traits during the breeding process

Breeding and Variety Development

Phenotyping

Elite Variety Evaluation

Commercialization

Release

How we workCIMMYT, IITA, NARS

CIMMYT, IITA, NARS, Private Sector

CIMMYT, Private Sector, NARS, NGOs

Regulatory Bodies, Private Sector/NARS

Private Sector/NARS

• Maize is different to many crops due to a vibrant seed sector (120 firms in Africa)• CIMMYT does not release varieties • Most hybrids are released by SMEs and MNCs, OPVs by NARS• It can take over 10 years from variety development to commercialization

Phenotypingnetwork for:• Drought• Low N• Striga• MSV• MLN

Artificial infestation of maize plants with stem borer eggs

Past Experience: Stemborers

Measuring Leaf Toughness

R Traits

Leaf damage score (1-9) Tunnel length Exit holes

Busseola fusca and Chilo partellus

Striga work initiated in 1998• 2.3 million ha affected by Striga in Africa

(AATF, 2006) resulting in yield losses between 20 and 80%

• Imidazolinone (herbicide) resistance exists naturally in maize and is easy to work with (single gene)

• Conversion of maize inbreds and hybrids to Imidazolinone resistant (IR) versions + herbicide seed coating formulation (BASF)

In 2013/14 3 OPVs and 5 hybrids released in Kenya and Tanzania

Genetic gains - MSVGrain yield

(t ha-1)Anthesis date

(d)ASI

Location Country Year Mean h Mean h Mean hHarare Zimbabwe 2012 5.21 0.79 76.1 0.89 -0.1 0.51Harare Zimbabwe 2013 7.21 0.72 71.7 0.91 0.6 0.37Harare Zimbabwe 2013 6.93 0.92 71.6 0.98 0.5 0.41

Combined 6.45 0.82 73.1 0.83 0.3 0.72

Estimated gains in tolerance to MSV: 141.3 kg ha-1 yr-1

(2.2% yr-1)

Maize Lethal Necrosis (MLN)

Symptoms: Severe mottling of leaves, dead heart, stunted growth (shortened internode distance), leaf necrosis and barren ears.

Why is MLN devastating maize in EA?

• MCMV is new to the region and the current strain is particularly aggressive

• Widespread cultivation of susceptible germplasm that has never been screened for MCMV

• Very favourable agronomic and environmental conditions

What has the EA maize breeding community done?

1. Artificial inoculation and screening protocols established in collaboration with OSU

2. MLN screening facility established at KALRO-Naivasha

3. Thousands of maize accessions screened for MLN by public and private sector

4. Promising hybrids have been submitted and recommended for fast track release in Kenya

Germplasm Evaluation by CIMMYT

Screening Year Location Entries Total Rows1st Screening Nov-12

Olerai and SunripeFarm 2,636 5,272

2ndScreening Jun-13

Oleria and Marula Farm 8,021 16,042

3rd Screening March-April 2014 KALRO Naivasha

19,53939,078

4th Screening October 2014 to Date KALRO Naivasha

15,32220,356

TOTAL 45,518 80,748

Approximately 65% of entries are inbreds.

Type of Germplasm Evaluated

• Diverse Inbred lines from CIMMYT’s Global Maize Program and collaborators (OSU and KU)

• Experimental and elite hybrids

• DH populations

• Biparental mapping populations

• Assocation mapping sets

Updates on Screening (2013)

May 2014

Breeding Approach

• Evaluation of existing elite hybrids for immediate recommendation (eg WE1101)

• Identification of donor inbreds• Formation of new hybrid combinations using

donor inbreds• Recycling donor inbreds (pedigree, BC, DH) for

development of new lines and next generation hybrid combinations

Inbred screening

Bad News: Close to 90% of materials susceptible

Good News: 10% of materials shows some tolerance

Bad News: Current elite CMLs collapse against MLN

CML442 CML443 CML448 CML444

CML395

Most widely used CML in existing commercial hybrids

Good News: Genetic Variation Exists

Severity Score Frequency in IMAS-AM panel

Distribution of Score frequencies indicates disease pressure is satisfactory and genetic progress can be made

Inbred line Kernel color Heterotic Group Max. MLN severity score

Disease response rating

CLRCY039 Y B 2.0 RCLYN261 Y A 2.0 RCLRCY034 Y B 2.0 RCKDHL120552 W A 2.3 MRCKDHL120161 W B 2.4 MRCKDHL120668 W B 2.4 MRCKDHL120664 W B 2.4 MRCML494 W B 2.5 MRTZMI730* W B 2.5 MRCKDHL120918 W B 2.5 MRCML550 W B 2.6 MRCML543 (CKL05003) W B 2.7 MRCKDHL120671 W B 2.7 MRCLA106 Y B 2.7 MRCKSBL10205 W AB 2.7 MRCKSBL10194 W AB 2.8 MRCML535 (CLA105) Y B 2.8 MRCKSBL10060 W A 2.9 MRCKDHL121310 W B 3.0 MRDTPYC9-F46-1-2-1-2-B Y A 3.0 MRCKDHL0500 W B 3.0 MR

Table 1. Responses of selected CIMMYT maize inbred lines to artificial inoculation with MLN at Narok and Naivasha in Kenya (2014)

Sources of Resistance are not ideal

CLRCY039CLRCY034

• Resistance is coming from unadapted tropical lowland sources from Latin America, SE Asia and from temperate germplasm from the USA.

• Most resistant lines tend to be yellow – there appears to be strong linkage between Y-1 and MCMV resistance.

Line Development Strategy• Resistant lines used directly in pedigree and DH breeding

pipelines: Over 900 pedigree starts made in 2014 alone. (F3)

• Resistant yellow lines are being converted to white versions by BC. Time consuming as yellow is dominant and MCMV R appears to be closely linked to Y1. (F2)

• Elite CMLs (eg CML442, CML444, CML312) are being converted to MLN-tolerant versions through phenotypic selection and MAS (BC2)

• DH can speed up the process and increase likelihood of fixing the right gene combinations (DH lines obtained)

• We know there are loci for SCMV R on Chr3 and Chr10. Relatively little is known about MCMV R.

Over 7,000 hybrids screened in 2014. Around 30 are showing promise for MLN and other traits. These have been submitted for release

HYBRID/PRODUCT DEVELOPMENT

MLN Scores (1-5)Entry Pedigree 1 3 4

13 CKH10085 1.8 2.6 2.518 CML78/P300C5S1B-2-3-2#-#1-2-B*7-#-B 1.8 2.0 2.6

5 CKIR12014 2.1 2.0 2.74 CKIR12010 2.1 2.9 2.8

28 CKH10773 1.7 3.2 2.92 CKIR11027 1.9 2.8 3.0

29 H513 3.3 3.9 4.430 H520 3.3 3.6 3.631 H614 3.2 3.2 3.332 H624 2.8 3.2 3.533 WH403 3.3 3.6 4.634 WH507 3.6 3.3 3.935 WH505 3.0 3.5 4.036 PAN691 3.6 3.9 3.837 PANM419 3.2 3.5 4.438 DUMA43 3.5 3.9 4.739 PHB30G19 2.1 3.1 3.340 DK8031 3.7 4.0 4.7

Mean 2.5 3.3 3.6LSD 0.85 0.74 0.88CV 17 11 12

Heritability 0.79 0.71 0.71

Results of hybrid re-validation trials at two locations

Commercial check

CKDHH0995

Promising pre-commercial hybrids with MLN tolerance

NUE Hybrids in NPT in East Africa

Hybrids submitted for release on basis of Low N + MLN scores below 3

Commercial Checks

New Hybrids are showing up to a 1 point (20%) improvement compared to checks

Hybrid Status MLN1 MLN2 MLN3

CKH10769Released in Uganda and Kenya

2014 2.9 3.0 3.2

CKH10767Released in Uganda and Kenya

2014 2.5 3.5 3.5

CHMLND0086 (CKH12600)

Recommended for release in UG in 2015. Top on-farm in TZ. 2.5 2.8 2.8

CKH12603Recommended for release in UG

in 2015 2.9 2.8 2.7

CKH12607Recommended for release in TZ

in 2015 2.7 3.0 3.0CKH12601 2.7 3.0 3.5CKH12613 2.4 2.7 3.0CKH12616 2nd year of NPT in Kenya 2.5 2.7 2.7

CKH126022nd year of NPT in Kenya and seed

scale-up underway 2.9 3.0 3.0NPT Check 3.7 3.7 3.7

Hybrids in NPT in EA

Expanding Phenotyping Capacity

• Heavy emphasis on MLN site at Naivasha• Disease pressure is high• Elevation (1900m) means most germplasm is

evaluated outside natural ecology

• There is a need for natural hotspot sites in the target agro-ecology

• Requirements: disease presence, data collection, agro-ecological parameters

MLN Network

Site Country Inoculation Method

Capacity Planting Season

Location

Naivasha Kenya Artificial Inoculation 16 ha April & OctLatitude: -0.68197734Longitude: 36.39519367Elevation: 1911m

Babati Tanzania Natural Hotspot 2 ha MarchLatitude: -4.20963602Longitude: 35.73990726Elevation: 1378m

Karama Rwanda Natural Hotspot 5 ha MarchLatitude: -2.24102797Longitude: 29.64548721Elevation: 1613m

Thank You