Abstract

     This study, conducted at the College of Agriculture, University of Kirkuk, in autumn during the growing season of 2023, aimed to examine the effect of heat accumulation on the growth and productivity of nine maize genotypes three different planting dates (July 5, July 15, and July 25). A split-plot design with a randomized complete block design with three replicate was used to analyze the impact of planting dates and genotypes on various heat accumulation stages, aiming to estimate genetic parameters variance, phenotypic variance, and expected genetic advance for each growth stage.
     The findings indicated that the various planting dates had a substantial impact on heat. In early heat accumulation phases (VE, V2, and V4), The expected genetic advance values for these stages were notably high, with percentages of 29.175%, 19.077%, and 18.283%, respectively the initial date (July 5) showed strong heritability rates, suggesting the possibility of improving genetic characteristics by selection at these periods. Meanwhile, these values were lower in stages such as V6 and V8, with heritability values of 0.571 and 0.572, respectively.. For the second date (July 15), heritability values were high in most stages, suggesting a significant influence of genetic factors, with moderate to high genetic advance in early stages but low in later stages like V12 (9.900%)  and V14 (4.256%). For the third date (July 25), genetic and phenotypic variance values were moderate across most stages, reflecting notable genetic and phenotypic variation. Heritability values were high in almost all stages, except for the final stage(V14), which had a moderate value of 0.457627. The expected genetic advance values were moderate across most stages, suggesting the potential to improve genetic traits at certain stages.