Interactive maize breeding for biotic stresses across ecosystems in Kenya

 O.M. Odongo, S.I. Ajanga, C.M. Mburu & J. Ininda

Maize in Kenya is affected by a number of biotic stresses which vary in their effect on grain yield depending on the season and agro-ecological zones.  Major among theses stresses are northern leaf blight caused by Exserohilum turcicucum, maize streak virus transmitted by leaf hopper, rust (Puccinia sorghi), grey leaf spot (Cercosporazeae maydis), stalk/ear rot (Diplodia maydis and Fusarium spp.), stalk borer and weevils.  The most economic means of minimizing losses from these stresses is through resistance breeding.  The development of a variety resistant to all these stresses by one breeding programme will not only be very expensive, but will also be very demanding in expertise being available in a given programme.  It is in this respect that an interactive breeding approach was initiated in Kenya to take advantage of maize germplasm, equipment, ecology, and expertise found in different Kenya Agricultural Research Institute (KARI) Centres.  The Centres involved were Kakamega, Muguga, Embu, Kitale and Katumani.  The Centres were grouped on the basis of common biotic stresses.  These groupings linked Embu, Muguga and Kakamega Centres where blight, grey leaf spot, maize streak, stalk borer and weevil are major biotic stresses with varying magnitudes in their mandate areas.  Screening and selection of inbreds for various stresses was done at each Centre, emphasizing the major stresses in specific ecologies and thereafter there was exchange of information and germplasm.  Such information and germplasm were used in developing maize hybrids that have passed through the Kenyan variety testing system and are in the last stages of variety release system, having gone through preliminary yield trial, advanced yield trial, national performance trial and on-farm trial.  The paper presents data on the selected varieties at various test stages.  The data is on grain yield, major biotic stresses scores, plant height, maturity and standability.  Four hybrids have been developed at KARI Kakamega and are ready for release to farmers due to their superiority over available checks for biotic stresses and grain yield.  The varieties are KM 2001, KM 2012, KM 2013, KM2023, with grain yields ranging from 7 - 10 tonnes per hectare compared to the commercial checks Phb3253 and H622 which had grain yield ranging from 5 - 6 tonnes per hectare.