Experiment on the Genetic Variation and Path Coefficient Analysis of Introgressed Maize Inbred Lines for Economic Traits

Aims: To evaluate introgressed maize inbred lines and respective donor inbred lines for selected
economic traits and adaptability.
Study Design: Field evaluation was carried out in this study.
Place and Duration of Study: The experimental material comprised 123 inbred lines: 76
introgressed inbred lines that combined temperate and tropical germplasm. These inbred lines were
selected from three distinct environments (Rattray Anorld Research Station and Kadoma in Zimbabwe
and Ukulinga Research Centre in South Africa) to form three sets of introgressed inbred lines and
were considered as test genotypes. There was also a set of 26 temperate inbred lines, including the
inbred donor line that was used as a set of positive control inbred lines adapted to the South Africa
warm temperate environment. Additionally, a set of 21 tropical inbred lines was included as negative
control maize inbred lines from Zimbabwe tropical germplasm. The evaluation experiment was carried
out at Rattray Anorld Research Station (RARS), Kadoma Research Centre (KRC), Cedara Research
Station (CRS) and Ukulinga Research Stations (UKRS) in Zimbabwe and South Africa in 2012-13
summer season.
Methodology: Augmented alpha lattice experimental design was used to evaluate a total of 123
inbred lines that were randomly assigned into six blocks, in each block, ten test entries were randomly
assigned to plots within each block, and two common tropical control lines (SC21 and SC19; repeated
checks) were also randomly assigned in each block.
Results: Genetic variation was significant (P < 0.05) for all the major economic traits among inbred
lines within and across sets. Heritability estimates ranged from low (0.21%) to high (91%) for stalk
lodging and silking days, respectively. Comparison of means of inbred lines sets illustrated that
environmental effect had an influence on grain yield of introgressed lines. Grain yield and ear
prolificacy performance across sets also illustrated that introgression of temperate germplasm in
tropical elite inbred lines was effective. Spearman’s rank correlation analysis on grain yield and ear
prolificacy highlighted the correlation between selection environments. Correlation among traits
demonstrated that grain yield had significant (P < 0.05) positive correlation with plant and ear aspects,
plant height, root and stalk lodging, ear prolificacy and grain moisture content at harvest. Generally,
indirect effects of secondary traits on the grain yield potential of inbred lines were negligible.
Conclusion: From the results, introgressed inbred lines has a significant genetic variation that can be
explored to select inbred lines that have desired economic traits that enhance adaptability in South
Africa warm temperate environment. Traits such as plant and ear height, root and stalk lodging, ear
prolificacy and grain moisture content at harvest can be used to select for high grain yielding inbred
lines directly. Indirect secondary traits (plant height and ear prolificacy) can be emphasised during
introgression of temperate germplasm in tropical elite inbred lines.