Usefulness of F3 Testcrosses to Identify Bi-Parental Maize Populations with the Best potential for Producing Superior Inbreds

Maize is an important crop in the East African region, but continues to be plagued by biotic and abiotic constraints. Genotypes carrying genetic resistance to these constraints in addition to having good agronomic traits are the most desirable. A cross between CIMMYT lines and NaCRRI weevil lines generated 112 populations. These need to be reduced to facilitate intensive testing to obtain inbreds with highest potential for developing hybrids with the desired traits. To achieve this, 10 F2 were selfed and advanced to F3, testcrossed and evaluated in 3 environments. Preliminary results on inheritance and heritability of 3 traits in this study revealed additive genes action or lesser dominance effect for turcicum leaf blight (TLB) and maize streak virus (MSV). Anthesis-silking interval (ASI) was quantitatively inherited with minor genes effects. Both ASI and TLB showed moderate values of heritability ranging from - 0.20 to 0.58. Low correlation values between F2 and F3 also emphasized low heritability of traits apart from E111 for TLB (r = 0.90). Index selection showed a huge disparity with visual selection. Managed and imposed environments will be used in evaluation of 250 F3 testcrosses to determine the level of tolerance to drought and TLB and MSV diseases and usefulness criterion will be used to choose promising populations.