Genetic Improvement of African Maize towards Drought Tolerance: A Review

Abstract

Africa supports a population of over 1 billion people with over half of them depending on maize for food and feed either directly or indirectly.  Maize in Africa is affected by many stresses, both biotic and abiotic which significantly reduce yields and eventually lead to poor production.  Due to the high demand for maize in the region, different improvement strategies have been employed in an effort to improve production.  These include conventional breeding, molecular breeding, high throughput phenotyping techniques and remote sensing-based techniques.  Conventional breeding techniques such as open pollination have been used to develop drought avoiding maize varieties like the Kito open pollinated variety (OPV) of Tanzania and Guto OPV of Ethiopia.  A combination of conventional breeding and molecular biology techniques has led to improved breeding strategies like the Marker Assisted Back Crossing (MABC) and Marker Assisted Recurrent Selection (MARS).  These techniques have been used to improve drought tolerance in existing inbred maize lines like the CML 247 and CML 176.  Through genetic engineering, different genes including C4-PEPC, NPK1, betA, ZmNF-YB2, cspB, ZmPLC1 and TsVP have been cloned in maize.  Transgenic maize crops expressing these genes have shown increased tolerance to drought stress.  Although there is substantial progress towards developing drought tolerant maize, many African farmers are yet to benefit from this technology.  This is due to lack of an enabling policy framework as well as a limited financial investment in biotechnology research.

Keywords: Maize, Drought tolerance, Genetic engineering; Biotechnology; Transgenic crops