Determining the Heterotic Group of the Nineteen Open Pollinated Maize Varieties Based on the Performance of Their Topcrosses with Inbreed Lines Testers in Uganda
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The study was conducted to determine the heterotic group of the 19 OPVs using the specific combining ability effects of their test crosses in terms of grain yield generated from L x T mating design and evaluated in 4 agro ecologies of Uganda using 5x13 α-lattice design replicated twice per location. The results of this experiment indicated the presence of low variability for grain yield and thus the possibility of selection among the topcross hybrids that are adapted to the different agro ecologies of Uganda is low. An OPV parent was assigned to group A when its cross with inbred line tester A showed a large negative SCA value otherwise it was assigned to group B and those parents with their lower magnitude of SCA were assigned as AB heterotic group. Based on this criterion, 3 parent OPVs (Longe 4, Longe 5RS and SUWAN) were assigned to the heterotic group A, 2 (SITUKA MI and Ambsyn5) were assigned to heterotic group B, and other 14 OPVs that showed similar performance and lower SCA value than the SE when crossed with tester A or tester B were assigned to both heterotic group AB. The expressed heterosis between female OPV Ambsyn5 and SITUKA MI when test crosses with in bred line tester A (CML536) and Longe 4, Longe 5RS and SUWAN with another tester B (CML202) including OPV KC2014 which was with positive GCA could be exploited to produce topcrosses.