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.
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 |
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.
Nutrition, health and food security 