Topcross Analysis of Genetic Variability and Heterosis in Maize (Zea mays L.)

• Saif S Mahameed1, Mustafa Abed AL-Jabbar Salih2, Dheeaa S Alrawi3, Omar A Kanoosh4 and Mohammed S Abed4

  Author

          The research took place in 2024 on maize (Zea mays) in Al-Khalidiyah, Iraq during the autumn season, and aimed to identify variations in heterosis, as well as field performance and genetic diversity, of multiple inbred lines and their hybrids produced through top-crosses. The experiment involved seven inbred lines (S1 to S7), with line S1 being the male parent crossed with the remaining six inbred lines to produce six hybrids. Experimental treatments were arranged in a randomized complete block design (RCBD) with three replications, the experimental plot approximately 2.5 m × 2.5 m. Plants were spaced at 75 cm between rows and 25 cm between plants, giving a plant density of about 53.333 plants ha^-1. Eight morphological traits had been recorded and were statistically different among the treatments, and the LSD test showed that many of the hybrid plants had greater yields than their respective parents. The hybrid S1-S5 expressed positive and statistically significant mid-parent heterosis for most of the measured traits. When analyzing genetic variance, broad heritability estimates indicate that many types are influenced more by genetic factors than the environment. Simple correlation coefficient analysis found that yield had a positive significant relationship with grain per ear, grain per row, rows per ear and leaf area on yield. Cluster analysis classified the genotypes into three main clusters, reflecting substantial genetic diversity and suggesting the usefulness of these hybrids in maize breeding programs aimed at improving yield related traits.

• pdf