Combining ability of introduced sorghum parental lines for major morpho-agronomic

Sorghum (Sorghum bicolor) is the dominant crop in thearid and semi-arid tropics, where drought seriouslyaffects its production. The use of improved cultivars,particularly hybrids, was found to be the majorcomponent of the integrated approach of mitigating thedrastic effect of drought. Thus information on thecombining ability of different lines is very pertinent tochoose the best parents and to set the suitable breedingmethod. Fifty-four F1 hybrids were developed bycrossing 18 pollinator parents with three standardfemales following the Design II mating scheme. Thehybrids were evaluated at two drought prone locations,Melkassa and Shoa Robit in Ethiopia, using randomizedcomplete block design. This research was conducted withthe objectives of estimating the combining ability of theparents with respect to yield and yield-related parameterslinked to drought tolerance, and to determine the mode ofgene action for drought tolerance traits. The StatisticalAnalysis Systems (SAS) was used to analyze the data.Combined analysis of variance revealed significantvariation among entries for panicle length, seed weight,plant height, time to maturity and panicle exsertion. Theentry × location effect was significant for the otherobserved traits thus signifying differential response of thegenotypes in each of the locations. General combiningability (GCA) for plant height, panicle exsertion, paniclelength, grain yield and seed weight was significant amongmale parents indicating the prevalence of additive geneaction in determining these traits. The GCA for femaleswas not significant for any of the observed traits exceptpanicle exsertion. However, P9517A appeared to bemarginally superior to the other two females in producinghigh-yielding hybrids having relatively higher panicleweights and panicle yields as well as in possessing largernumbers of green leaves at maturity, a trait termed asstay-green. The male parents exhibited considerablevariability for most of the traits considered. Specificcombining ability (SCA) effects were not significant forany traits observed.