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Update: CIMMYT maize inbred lines and pre-commercial hybrids with potential resistance to maize lethal necrosis (MLN)

May 13, 2014

A promising pre-release CIMMYT hybrid versus an MLN-susceptible commercial check. Since 2011 MLN has become a disease of serious concern in the east African countries of Kenya, Tanzania, Uganda and possibly Rwanda. CIMMYT has been working in close collaboration with the Kenya Agricultural Research Institute (KARI), private sector partners and virology experts from the USA to combat the disease through host-controlled resistance. A CIMMYT-KARI MLN Screening Facility was established at Naivasha in September 2013, and a large array of maize germplasm is presently being evaluated against the disease under artificial inoculation. Subsequent to the development of effective protocols, CIMMYT and KARI have been conducting MLN screening trials in Kenya since 2012, to identify promising inbred lines and pre-commercial maize hybrids with resistance to MLN.  This is the second update of the information on potential MLN-resistant or moderately resistant inbred lines and pre-commercial hybrids (in CIMMYT genetic backgrounds), following the first update that was shared with public and private sector partners in May 2013.

An evaluation of CIMMYT inbred lines and pre-commercial hybrids was done under artificial inoculation during 2013-2014 in two independent trials, at Narok and Naivasha sites in the Rift Valley, Kenya (Tables 1 and 2).  In each trial, the entries were grown in at least two replications, and MLN severity scores were recorded at different stages of crop growth (vegetative and reproductive stages) on a 1-5 scale (1 = no disease symptoms, 5 = extensive damage). The highest MLN severity score recorded across different trials on a particular entry, and the corresponding disease response rating, are presented here.

Table 1. Responses of selected CIMMYT maize inbred lines to artificial inoculation with MLN
at Narok and Naivasha, Kenya (2013-2014)

Inbred line

Kernel color

Heterotic Group

Max. MLN severity score

Disease response rating

CLRCY039

Y

B

2.0

R

CLYN261

Y

A

2.0

R

CLRCY034

Y

B

2.0

R

CKDHL120552

W

A

2.3

MR

CKDHL120161

W

B

2.4

MR

CKDHL120668

W

B

2.4

MR

CKDHL120664

W

B

2.4

MR

CML494

W

B

2.5

MR

TZMI730*

W

B

2.5

MR

CKDHL120918

W

B

2.5

MR

CML550

W

B

2.6

MR

CML543 (CKL05003)

W

B

2.7

MR

CKDHL120671

W

B

2.7

MR

CLA106

Y

B

2.7

MR

CKSBL10205

W

AB

2.7

MR

CKSBL10194

W

AB

2.8

MR

CML535 (CLA105)

Y

B

2.8

MR

CKSBL10060

W

A

2.9

MR

CKDHL121310

W

B

3.0

MR

DTPYC9-F46-1-2-1-2-B

Y

A

3.0

MR

CKDHL0500

W

B

3.0

MR

*IITA Inbred Line

Abbreviations
Y: Yellow; W: White
Disease Response Rating
R: Resistant (max. MLN severity score ≤2.0)
MR: Moderately resistant (max. MLN severity
score ≥2.0 but ≤3.0)
S: Susceptible (max. MLN severity score >3.0)
MLN Severity Scoring (1-5 Scale)
1 = No MLN symptoms
2 = Fine chlorotic streaks on lower leaves
3 = Chlorotic mottling throughout plant
4 = Excessive chlorotic mottling and dead heart
5 = Complete plant necrosis

 

Table 2. Responses of selected CIMMYT pre-commercial hybrids under artificial inoculation
against MLN at Narok and Naivasha, Kenya (2013-2014)

Hybrid Pedigree

Max. MLN severity score

Disease response rating

CKH12613 Under NPT in Tanzania

2.25

MR

CKH12622 CML444/CML445//CLWN234

2.33

MR

CKH12603 Under NPT in Uganda

2.37

MR

CKH12623 CML539/CML442//CLWN234

2.38

MR

CKH12624 CML539/CML442//CML373

2.45

MR

CKIR12014 CML312/CML442// CKSBL10028

2.49

MR

CKH12625 CML444/CML445//CML373

2.50

MR

CKIR12007 CML78/P100C6-200-1-1-B-B-B-B-B// CKSBL10014

2.50

MR

CKDHH0970 CKDHL0089/CKDHL0323//CKDHL0221

2.50

MR

CKIR11024 CML78/P300C5S1B-2-3-2-#-#-1-2-B-B-#// CKSBL10060

2.51

MR

CKH12607 Under NPT in Tanzania

2.51

MR

CKH10085 Under NPT in Kenya

2.62

MR

CKH12600 Under NPT in Uganda and Tanzania

2.66

MR

CKH12627 CLRCW106//CML444/CML395

2.70

MR

CKDHH0943 CKDHL0159/CKDHL0282//CKDHL0214

2.75

MR

CKDHH0945 CKDHL0089/CML395//CKDHL0214

2.75

MR

CKH12626 CML395/CML488//CML373

2.77

MR

Note: The responses of the promising hybrids mentioned above are being validated through
experiments at the MLN Screening Facility in Naivasha

MLN Severity Scoring (1-5 Scale)
1 = No MLN symptoms
2 = Fine chlorotic streaks on lower leaves
3 = Chlorotic mottling throughout plant
4 = Excessive chlorotic mottling and dead heart
5 = Complete plant necrosis
Disease Response Rating
R: Resistant (max. MLN severity score ≤2.0)
MR: Moderately resistant (max. MLN severity
score ≥2.0 but ≤3.0)

 

 For further information on:

  • MLN research-for-development efforts undertaken by CIMMYT, please contact:
    Dr. B.M. Prasanna, Director, Global Maize Program, CIMMYT, Nairobi, Kenya;
    Email: b.m.prasanna@cgiar.org
  • Availability of seed material of the promising lines and pre-commercial hybrids, please contact:
    Dr. Mosisa Regasa (m.regasa@cgiar.org) if your institution is based in eastern Africa, or Dr. James Gethi (j.gethi@cgiar.org) if your institution is based in southern Africa or outside eastern and southern Africa.