Diversity assessment among selected Philippine native corn (Zea mays L.) based on simple sequence repeat (SSR) markers and antioxidant activity � phytochemical content

A set of 46 Philippine native corn varieties sourced from various provinces in the Philippines was subjected to diversity assessment based on 37 polymorphic SSR markers and antioxidant activity-phytochemical content. The SSR-marker based genetic diversity analysis revealed a total of 146 alleles across all loci detected, mean of 4 alleles per locus, mean PIC values of 0.5908, suggesting that these SSR markers are genetically informative and can be used for further genetic diversity studies. Further genetic diversity analysis revealed a mean gene diversity of 0.6480, a mean heterozygosity of 0.2650, with most of the SSR loci deviating from Hardy-Weinberg Equilibrium (HWE) and a mean within-population inbreeding coefficient of 0.5982, suggesting that there is a high genetic diversity among the set of Philippine native corn and that inbreeding was the major driving force for the genetic chance for each population. A high genetic distance (mean of 0.7486) among the 46 native corn was also revealed. Clustering using the UPGMA-SAHN and as supported by principal coordinate analysis (PCoA) based on SSR marker polymorphisms, revealed two distinct genetic groupings. Diversity analysis based on the antioxidant activity and phytochemical content revealed several significant variations existing among the varieties. The native maize was characterized to have a mean DPPH radical scavenging activity of 0.64% mean phenolic content of 1.65 mug gallic acid equivalent (GAE)/g of dried corn kernel, mean flavonoid content of 1.87mug catechin equivalent (CE)/g of dried corn kernel and mean carotenoid content of 0.17 mug/g of dried corn kernel. Flavonoid content was suggested to have the largest contribution to the antioxidant activity for each variety. Only phenolic content had a significant correlation with the antioxidant activity. The UPGMA cluster analysis based on antioxidant activity-phytochemical content and as supported by principal component analysis (PCA), revealed six distinct groupings among the native corn varieties. The clustering pattern based on SSR marker polymorphisms was negatively correlated with clustering based on antioxidant activity � phytochemical content. Hence, another set of SSR-markers and other types of molecular markers linked to phytochemical metabolism of the native corn can be used for genetic diversity analysis. These results can be used for Philippine native corn varietal characterization and these native corn varieties can be included in the development of future corn breeding programs.