Kernel test weight (KTW) is one of the important assessment indexes of maize quality grade and one of the important influencing factors of yield. This study analyzed 12 traits related to KTW in 321 maize inbred lines using multivariate methods. The principal component analysis (PCA) indicated that the four PCs covered 78.176% of the information of the 12 traits in 321 maize inbred lines. Cluster analysis categorized the maize lines into six groups, identifying 16 elite inbred lines with the highest KTW. A stepwise regression model for KWT evaluation was developed using four PCA traits: starch content, amylopectin content, 100-kernel weight, and kernel circumference. The findings of this study serve as a valuable reference point for the genetic improvement of maize germplasm re-sources in kernel test weight and the creation of high kernel test weight maize resources.

Tropical germplasm has accumulated a large number of genes adapted to a variety of adversities. In this study, we assessed the genetic diversity and population structure of 109 inbred maize lines newly released from the International Maize and Wheat Improvement Center (CIMMYT) in the last few years. The results indicated the following: (1) linkage disequilibrium (LD) analysis showed that tropical maize germplasms had a faster rate of LD decay, suggesting higher recombination rates and genetic diversity; (2) both the phylogenetic tree and structure analysis supported the classification of the material into three subgroups; (3) the results of the principal component analysis were consistent with the population structure analysis, further verifying the reliability of subgroup delineation; (4) the genetic distances between the tropical germplasms from groups 2 and 3 and the elite temperate inbred lines were relatively close, which is suitable for temperate germplasms improvement. The results can help us select suitable tropical germplasms and speed up the process of inbred line development and maize improvement.