Direct effects on scenarios and types of path analyses in corn hybrids

The objective of this study was to estimate the direct effects of explanatory variables on the grain yield of corn in the combinations formed by three types of hybrids x two harvests x nine scenarios of explanatory variables x two types of path analyses. Eleven explanatory variables were measured in 361, 373, and 416 single-, triple-, and double-cross hybrid plants from the 2008/2009 harvest, respectively, and in 1777, 1693, and 1720 single-, triple-, and double-cross hybrid plants from the 2009/2010 harvest, respectively: plant height at harvest (PH), ear insertion height (EIH), ear weight (EW), number of grain rows per ear (NR), ear length (EL), ear diameter (ED), cob weight (CW), cob diameter (CD), 100-grain mass (HGM), number of grains per ear (NGE), grain length (GL) and, the main variable, grain yield (YIELD). Before conducting the traditional and ridge path analyses, 0, 1, 2, 3, 4, 5, 6, 7, and 8 explanatory variables were excluded from scenarios 1, 2, 3, 4, 5, 6, 7, 8, and 9, respectively. Next, the direct effects of explanatory variables on YIELD were estimated for each hybrid, harvest, scenario, and type of path analysis. The variables EW, NGE, and HGM had stronger direct effects on YIELD in the first three scenarios and the variables EL and ED had stronger direct effects on YIELD in the other scenarios regardless of hybrid or harvest. The use of the ninth scenario of path analysis is recommended regardless of hybrid and harvest given the ease of explanatory variable measurement (EIH, EL, and ED), the low degree of multicollinearity and the good prediction of the path analysis (R² ≥ 0.78).