The latest study aimed to analyze the path coefficient for synthetic cultivars of maize (Zea mays L.) to determine the selection criterion for improved grain yield. In achieving this goal, a field experiment commenced in 2022 at the Ibn-Al-Bitar Preparatory Vocational School, Kerbala Governorate, Iraq. The study set up in a randomized complete block design (RCBD) used a split-plot arrangement and three replications. The main plots comprised six combinations of mineral and organic fertilizers, while subplots were the six synthetic corn cultivars, Fajr1, Maha, 5018, Sumer, Sarah, and Baghdad-3. The genotypic path coefficient analysis showed that grains per ear in the first and second fertilizer levels could benefit as a selection index, achieving the highest total effect (genotypic correlation) of 0.9459 and 0.9957, respectively, obtained through an indirect influence of the biological yield. The third level of fertilizer combination gave a harvest index that can also be a selection index because it showed the highest total result of 0.9825, obtained from a direct consequence of the grain yield (0.8745). In the fourth fertilizer combination, the biological yield can become a selection index because it gained the highest total outcome of 0.9898 from the direct effect of the grain yield (6.7848). In the fifth and sixth fertilizer combinations, the total uptake of nitrogen may be the basis for the selection index reaching the maximum total effects of 0.9806 and 0.9834, respectively, acquired through indirect effects of the biological yield in the fifth and total uptake of phosphorus in the sixth fertilizer combination.

Keywords: Maize (Zea mays L.), mineral fertilizers, organic manures, path coefficient, selection criteria, nitrogen uptake, growth and yield traits

Key findings: The grains per ear at the first and second fertilizer levels, the harvest index at the third level, the biological yield at the fourth level, and the total nitrogen uptake at the fifth and sixth fertilizer levels can be effective selection indicators for improving the maize grain yield.