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Maize lethal necrosis: Scientists and key stakeholders discuss strategies as the battle continues

29A recently-emerged disease in Eastern Africa, maize lethal necrosis (MLN), remains a serious concern. A regional workshop on the disease and its management strategies was held during 12-14 February 2013 in Nairobi, Kenya. Organized by CIMMYT and the Kenya Agricultural Research Institute (KARI), the workshop brought together nearly 70 scientists, seed company breeders and managers, and representatives of ministries of agriculture and regulatory authorities in Kenya, Uganda, and Tanzania, as well as experts from the U.S.A.

The key objective of the meeting was to “establish a strong interface between research and regulatory institutions in Eastern Africa to effectively tackle the MLN challenge, including the ongoing efforts and further steps to identify and deploy disease-resistant germplasm, and to create a system that can ensure a constant flow of varieties,” explained B.M. Prasanna, CIMMYT Global Maize Program director. Prasanna highlighted the difficulties faced by the maize farming community from the disease, and emphasized the need to accelerate deployment of MLN resistant maize varieties and to generate necessary awareness among the relevant stakeholders on management strategies. “It is necessary to break the MLN disease cycle and tackle the problem from multiple perspectives,” added KARI director Ephraim Mukisira. He mentioned that besides partnering with CIMMYT on breeding for MLN resistant varieties, KARI will also be distributing seed of alternative crops to farmers in affected areas. “As a dairy farmer, I will be planting napier grass instead of maize this season,” noted Mukisira.

The first signs of a new disease appeared in 2011 and 2012 in the Rift Valley Province, Kenya. A team of CIMMYT and KARI scientists identified it as MLN, a disease caused by a double infection of the maize chlorotic mottle virus (MCMV) and the sugarcane mosaic virus (SCMV) and transmitted by insects. According to Godfrey Asea, plant breeder and head of the Cereals Program at the National Crops Resources Research Institute (NaCRRI), Kampala, MLN was also identified in Uganda. Furthermore, symptoms of MLN have been cited in Tanzania, said Kheri Kitenge, maize breeder at the Selian Agricultural Research Institute (SARI), Arusha.

Scientists, particularly breeders, have made significant progress in tackling the disease. Studies are already underway at two field sites (Naivasha and Narok) where responses of a wide array of inbred lines and pre-commercial hybrids are being evaluated under high natural disease pressure and artificial inoculation. Participants visited the Sunripe Farm in Naivasha, where they observed KARI-CIMMYT MLN trials under natural disease pressure. A trial under artificial inoculation in Naivasha featuring nearly 175 commercial maize varieties is showing high levels of susceptibility to MLN. Researchers remain hopeful as some of the elite inbred lines and pre-commercial hybrids developed under projects such as the Drought Tolerant Maize for Africa (DTMA) or Water Efficient Maize for Africa (WEMA) are showing resistance to the disease.

During the farm visit, KARI pathologist Anne Wangai and her team showed how to generate artificial inoculum for MCMV and SCMV, as well as the enzyme-linked immunosorbant assay (ELISA) based technique for pathogen diagnosis at the national agricultural research laboratories at the KARI campus. The participants observed an artificial inoculation of maize seedlings in the field, followed by a discussion on some of the major changes in maize seed demand resulting from MLN incidence. “The maize seed industry is under stress in Kenya due to the need to replace some popular but MLN-vulnerable varieties as soon as possible,” explained Evans Sikinyi, Seed Trade Association of Kenya (STAK) executive officer. All stakeholders agreed that the foremost priority is to identify and speed deployment of MLN resistant maize varieties. “We also have to enhance the diagnostic capacity in the labs and ensure there is a rapid response and surveillance on MLN,” added Esther Kimani, general manager of phytosanitary services at the Kenya Plant Health Inspectorate Service (KEPHIS).

In the concluding session of the workshop, stakeholders identified key research areas and discussed partnership opportunities.