Combining Ability of Highland Adapted Double Haploid Maize Inbred Lines using Line X Tester Mating Design
Development of inbred lines is a routine activity in hybrid maize breeding program.
Understanding the relative importance of general (GCA) and specific (SCA) combining ability effects for
different traits of newly developed maize lines is of paramount importance to design future breeding
strategies for the development of hybrid. There are several types of mating designs available to study the
combining abilities of maize inbred lines, of which line x tester mating scheme is one used to determine
the combining abilities and also to categorize the lines into heterotic groups. The objectives of the study
were, therefore, to estimate GCA and SCA of newly developed highland maize lines using line x tester
mating design, to identify best promising hybrid crosses with desirable traits for further breeding and
cultivar development, and to identify the heterotic groups of the lines involved in the crosses. Twelve
lines and four testers were involved in the study. A total of 48 testcrosses along with two checks were
made available for evaluation across locations. An alpha lattice design (10x5) with two replications at each
location was used. Two lines (L6 and L5) showed highly significant and positive GCA effects for grain
yield. Besides, L6 also revealed positive GCA effects for the other yield related traits such as number of
ears per plant (NEPP), number of rows per ear (NRPE), number of kernels per row (NKPR) and ear
diameter (ED). On the other hand, crosses L7XT2, L8xT4, and L9xT1 had positive and significant SCA
effects for grain yield. The lines and crosses with positive and significant GCA and SCA effects,
respectively; could be selected for use in highland maize hybrid or/and synthetic cultivar development.
The testers clearly categorized L3 and L6 into their respective heterotic groups in a similar pattern unlike
the other lines which requires the application of molecular markers for further verification.