Combining ability of early and intermediate maize (Zea Mays L.) inbred lines for drought tolerance using line by tester analysis.

Maize (Zea mays L.) is an annual plant belonging to the family (Graminae or Poaceae). It is a major cereal crop in West Africa, accounting for slightly over 20% of all food crops produced for domestic production in the sub-region. It is one of the most important cereals in Ghana, which is cultivated in all the agro-ecological zones. The objectives of this study were to estimate the general and specific combining ability effects of the inbred lines, determine the mode of gene action controlling grain yield and drought tolerance. A study was undertaken to assess the combining ability of 17 early and 26 intermediate maize inbred lines and one check for each genotypic group for drought tolerance using line by tester (line x tester) analyses. This trial was conducted in the screen house of the Department of Horticulture, KNUST in 2016. A randomized complete block design with three replications was used in the experiment. Some inbred lines with desirable general combining ability (GCA) effects for the studied traits were identified under drought-stress condition. For early maize genotypes inbred lines L1 followed by L4 were best general combiners for number of kernel row per ear, number of kernels per row, cob weight and grain yield under drought-stress condition. For intermediate maize genotypes under drought-stress condition, the line L4 was best general combiner for grain yield, cob weight, number of kernel rows per ear and ear diameter for their positive and significant GCA effects. These lines could be selected for their good traits to develop high yielding hybrids and for further exploitation in a breeding programme. Hybrid combination, L7 x T2 and L8 x T1 under well-watered condition and L6 x T2 under drought-stressed condition for intermediate maize genotypes were good specific combiners for grain yield while, for early maize genotypes, crosses were not significant for yield under well-watered and drought-stress conditions. The low ratio of 𝜎2gca/𝜎2sca, in the current study showed the preponderance of non-additive gene actions for almost all the traits for early and intermediate maize genotypes. The inbred lines L1 (S6-15-22) and L4 (CML538) for early maize maturity genotypes and L4 (CML502) for intermediate maize maturity genotypes were identified as best general combiners that can withstand drought-stress. These lines showed positive and significant GCA effects for yield and yield-related traits under drought-stress condition. The cross L6 X T2 was identified as good specific combiners that can withstand drought-stress for the positive and significant SCA effect for grain yield and yield-related traits under drought-stress condition. Positive and significant mid-parent heterosis was observed under drought-stress condition for early and intermediate maize maturity genotypes. The crosses L2 X T1 and L3 X T2 observed high mid-parent heterosis for early and intermediate maturity genotypes, respectively. Generally, the results of the current study identified crosses with good level of heterosis, inbred lines with good GCA effects and cross combinations with desirable SCA effect for the traits studied. The results indicate the possibility of developing desirable cross combinations through crossing and or recombination of inbred lines with desirable traits of interest. Hence, the information from this study could be useful to researchers who would like to develop high yielding varieties of maize under drought-stress condition.

Source: KNUST