Commercial field corn hybrids are often used for germplasm or for extracting new inbred lines in hybrid breeding programs. However, the commercial single-cross hybrids should be identified before using their genetic materials to increase the effectiveness of new inbred lines and their hybrids. The objective of this study was to evaluate the genetic diversity of commercial single-cross hybrids as verified by Simple Sequence Repeat (SSR) markers and to assess their inbreeding depression using Troyer’s genetic diversity. Fifteen commercial field corn single-cross hybrids were selected from private seed companies and public sector agencies and evaluated for genetic diversity using 40 SSR markers. There was a high correlation between Jaccard’s index and simple matching index. The UPGMA dendrogram clustered the hybrids into 8 clusters, which showed hybrids within each of four clusters coming from the same genetic sources, except for a group of CP201 and NS3 hybrids that came from different sources. Besides, Troyer’s genetic diversity was applied to analyze the genetic diversity of six single-cross hybrids selected from the previous results. The SSR markers and the Troyer’s genetic diversity application gave the same direction of corn genetic diversity with a moderate correlation (r=0.66, P<0.01). Troyer’s genetic diversity ranged from 0.47 to 0.91, with an average of 0.72. The commercial field corn single-cross hybrids used in Thailand are still quite diverse, especially those from different seed companies. Therefore, breeders have a good chance to extract inbreeding lines from the commercial single-cross hybrids, and to make a new hybrid with high yield after the grouping of single-cross hybrids through the use of SSR markers or Troyer’s genetic diversity.
Keywords: SSR marker; genetic diversity; inbreeding depression; field corn hybrid
*Corresponding author: Tel.: (086) 9818658 Fax: (034) 351887
E-mail: agrcsj@ku.ac.th
