Combining ability and heterotic grouping of early maturing maize lines
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Maize is the main staple food in sub Saharan Africa, but its productivity is often inadequate on account of many production constraints. Amongst these is drought that causes on average an annual grain yield reduction of about 20%. Occurrence of drought is erratic but its effects can be mitigated by use of drought tolerant, early maturing varieties. Breeders in eastern Africa have developed early maturing inbred lines whose combining ability and heterotic grouping needs to be known before they can be used as parents in hybrid and open pollinated variety development. This study was designed to determine the combining ability and heterotic grouping of early maturing maize lines adapted to the drier mid- altitude ecologies of eastern Africa. Two experiments were conducted with the following specific objectives: (i) to estimate the general combining ability (GCA) of 12 early maturing inbred lines and identify good single cross hybrids with potential of being parents in various types of hybrids, (ii) to classify 24 early maturing inbred lines into heterotic groups and (iii) to compare inbred line and single cross testers for heterotic grouping of inbred lines. Data were collected on grain yield and other agronomic traits. Data analysis was carried out using GLM procedure from SAS for each environment and across environments. In Experiment 1, results showed that hybrids 9 and 10 performed consistently well across all environments. P3 maintained a consistent, positive and significant GCA for grain yield. In Experiment 2, three lines were distinctively separated into heterotic A and five into heterotic group B. Twelve other lines were assigned into heterotic group AB.