Maize is grown on 15 mi1lion ha in eastern and southern Africa. Several diseases, including maize streak virus (MSV), grey leaf spot (GLS) and turcicum leaf blight (ET) are of common occurrence in the region and regularly result in significant yield losses. With funding from The Rockefeller Foundation, a regional disease nursery (REGNUR) project was initiated in 1998 to promote and enhance regional collaboration to address the common disease and insect problems of maize. The REGNUR project aims to identify and increase access to disease resistant germplasm, generate and disseminate information on disease and insect resistance sources, and facilitate National Programs to develop resistant varieties. A recent REGNUR project was a diallel mating among 12 elite inbred lines identified by REGNUR collaborators. The trial was grown at 7 sites during 2001. Results showed that both general combining ability (GCA) and specific combining ability (SCA) effects were highly significant for GLS, MSV, head smut, Phaeosphaeria Leaf Spot (PLS), turcicum and rust (P. sorghi), whereas only GCA was important for ear rot resistance. On average, GCA determined 69% of resistance to diseases and only 37% of variation for grain yield. This implies that the approach to developing multiple disease resistance should involve identifying lines with good per se resistances to diseases with final selection for good combining ability for yield. Correlations between GCA effects for disease scores were generally non-significant, implying that it is possible to pyramid the genes for resistances to the different diseases into inbred lines. This underlies the need for screening specific diseases using artificial inoculation or reliable "hot-spots" and highlights the importance of a project like REGNUR, which enables such collaboration,

Genetic Resources Program|Global Maize Program

English

0409|AGRIS 0401|AL-Maize Program

Juan Carlos Mendieta

INT1617|INT2396

CIMMYT Staff Publications Collection