Identification of subtropical breeding lines for ideal plant architecture in maize through multiple selection indices

High plant density assumes significance for higher yield per unit area. However, reports on breeding for ideal plant architecture (IPA) in maize are limited due to lack of comprehensive characterization of germplasm. Here, we assessed genetic variation and identified inbreds for 14 plant architectural traits among 48 subtropical maize inbreds through multi-location analysis. Wide genetic variation for (i) stalk-related traits, viz., plant height (100.5-209.8 cm), ear height (26.4-106.3 cm), internode number (3.8-10.9), and internode length (8.1-15 cm); (ii) leaf-related traits, viz., leaf length (39.7-77.1 cm), leaf width (5.2-10.5 cm), leaf area (158.6-568.4 cm²), leaf angle (18.4-84.6°), leaf orientation value (2.2-71.3), number of leaves above-ear (3.2-7.2), and husk number (5.7-14.4); and (iii) tassel-related traits, viz., tassel height (21.8-34.9 cm), number of tassel branches (3.9-16.6), and tassel branching angle (10.2-78.4°) were observed. All traits showed significant variation due to environment and genotype × environment interactions. Correlation analysis implied that narrow leaf angle would produce compact tassel as well (r = 0.53, p < 0.001). Internode number and leaf width (r = - 0.33, p = 0.031), number of leaves and leaf length (r = 0.42, p = 0.004), plant height and leaf length (r = 0.39, p = 0.005), and leaf length and tassel height (r = 0.44, p = 0.003) were also associated. HKI-1105, CML-568, BAUIM-4, and BAUIM-2 were the most stable and promising inbreds with IPA using three popular selection indices (AMMI-TGSI, WAASBY-I, and MTSI). These promising inbreds could serve as suitable donors for germplasm diversification, besides generating hybrid combinations for high plant density. This is the first comprehensive analysis to characterize sub-tropically adapted maize inbreds for plant architectural traits.