Estimation of genetic divergence among maize genotypes under high plant densities and late sowing dates using cluster analysis

Abstract

With the aim of grouping similar Egyptian and Iraqi genotypes of   maize into homogeneous groups according to sowing date and plant density using cluster analysis and estimating the genetic divergence of the studied genotypes, the hierarchical clustering technique was used. A field experiment was carried out at Research Station A of the College of Agricultural Engineering Sciences - University of Baghdad, Department of Field Crops, in the Al-Jadriya area during the autumn season of 2023. A randomized complete block design (RCBD) was used with a split spilt-plots arrangement with four replications and three factors. The main plots included the two sowing dates (1^st August and 10th), and the sub plots included the plant densities (70.000 and 90.000 plants ha⁻¹). Six genotypes of   maize, two Iraqi and four Egyptian (Baghdad3, Al-Maha, TW-78, TW-345, IY-355, and IY-207), represented the sub-sub plots. The cluster analysis results showed that the genotypes differed in their clustering patterns according to sowing date and plant density. Euclidean distances also varied depending on the clustering pattern. The two genotypes that exhibited significant Euclidean distances were due to genetic differences and the presence of favorable genes not found in the other studied genotypes. The cluster analysis revealed that the Euclidean distance between the Iraqi variety Baghdad 3 and the Egyptian variety IY-355 was 8.779 and 14.47 at the first sowing date and densities of 70.000 plants h^-1and 90.000 plants h^-1, respectively. In contrast, the Iraqi variety Baghdad 3 and the Egyptian variety TW-78 exhibited an Euclidean distance of 9.44 at the second sowing date and densities of 70,000 plants h^-1. At the second sowing date and densities, the same Iraqi variety and the Egyptian variety TW-345 exhibited the highest Euclidean distance of 9.58. Therefore, it is recommended to include these varieties in crosses with the genotypes that have shown positive results. It is clear that variation is used to take advantage of the hybrid vigor and isolations from it, and thus we conclude that this statistical technique is a successful alternative to molecular techniques in case they are not available.