MAIZE and partners have worked tirelessly to prevent the spread and mitigate the impact of maize lethal necrosis (MLN) disease since its discovery in Kenya in 2011. The disease, which causes premature plant death and unfilled, poorly formed maize cobs, can lead to up to 100 percent yield loss in farmers’ fields. An MLN screening facility was established in 2013 in Naivasha, Kenya, followed by a quarantine facility in Zimbabwe in 2015. In the present, researchers continue to develop maize varieties with resistance to MLN using cutting-edge technologies and techniques to provide relief to farmers facing the disease.
Great strides were made in developing maize germplasm with resistance to maize lethal necrosis (MLN) disease in 2017, using both innovative technologies and novel maize genetic materials from around the world. MAIZE scientists have been working with Corteva Agriscience to identify one of the genes that confers strong resistance against MLN. With fine-mapping, a strategy that combines laboratory molecular tools with field phenotyping, scientists have narrowed their search to fewer than eight genes (from a total of ~40,000 in the maize genome).
A promising candidate among these eight genes will be validated via gene editing directly in the MLN-susceptible parental lines to determine whether it confers resistance to MLN. Gene editing, compared to other breeding methods, will allow scientists to shave off one third of the time it would take to develop new MLN resistant lines; expediting development and release of improved varieties to farmers.
Pre-breeding research, based on new sources of resistant alleles from native maize varieties in the germplasm bank transferred to early-generation lines for breeding use, is also used in the fight against MLN. Utilizing a broader range of disease resistant alleles in breeding helps to create varieties with durable resistance (capable of maintaining resistance over time). In 2017, 255 advanced pre-breeding lines developed from MAIZE were planted at the MLN screening site in Naivasha, Kenya for in situ evaluation for the first time.