This paper reports the first genetic diversity analysis of Philippine traditional maize populations performed through a cost-effective DNA pooling strategy. The diversity among selected 100 traditional maize populations collected from Luzon, Visayas, and Mindanao was evaluated using twenty simple sequence repeats (SSR) markers at the Institute of Plant Breeding, University of the Philippines Los Baños, Laguna, Philippines. A total of 138 bands ranging from two to 12 bands per primer were detected. The average number of polymorphic alleles, polymorphism rate, effective multiplex ratio, marker index, resolving power, and expected heterozygosity are 6.283, 87.17%, 5.798, 4.104, 15.897, and 0.658, respectively. The polymorphism information content (PIC) varied between 0.141 to 0.848, with an average value of 0.620. A dendrogram was constructed with a dissimilarity coefficient ranging from 0.14 to 0.55 and a mean dissimilarity index of 0.425. Cluster analysis revealed 13 groups based on the result of Approximately Unbiased (AU) p-values from 10,000 bootstrap iterations. The cluster analysis enabled the classification of populations with ambiguous places of origin. Analysis of molecular variance (AMOVA) showed higher within-population diversity (70%) than among-population diversity (30%) with PhiPT (pairwise genetic differentiation metric) of 0.298 (P = 0.001). These results revealed the significant diversity of traditional maize populations in the Philippines and the power of SSR markers in diversity and cluster analyses despite the age of this marker technology. These findings will aid plant breeders in developing approaches towards knowledgeable and efficient execution of breeding programs using traditional maize populations.
Selected tomato genotypes with contrasting fruit colors of orange and red were investigated for sequence-level variations of candidate genes involved in lycopene cyclization. Sequence-specific markers for tomato lycopene beta-cyclase (3) and lycopene epsilon-cyclase (1) genes were designed and used to screen for putative single nucleotide polymorphisms (SNPs) through Ecotype Targeted Induced Local Lesions IN Genome (EcoTILLING) and Sanger sequencing. Despite being regarded as among the evolutionarily conserved genes in the carotenoid biosynthetic pathway of tomato, four homozygous and heterozygous SNPs were identified in lycopene epsilon-cyclase gene at the upstream of Exon 1 (1 SNP) and the intronic region between Exons 1 and 2 (3 SNPs) based on multiple sequence alignment of the processing tomato hybrid ‘Ilocos Red’ and table type inbred ‘Hawaii7996’. These SNPs may have a regulatory association with variations in tomato carotenoid metabolism. Interestingly, no sequence difference was found between FLA456 and ‘Super Apollo’ despite being characterized by orange and red fruit colors, respectively. The results support prior studies suggesting that lycopene cyclase genes are transcriptionally controlled as evidenced by their highly conserved sequences. The SNPs characterized in this study at the promoter and intronic regions of lycopene epsilon-cyclase are starting loci to investigate further the genetic control of this gene in regulating carotenoid metabolism and products that result in varying tomato fruit phenotypes.
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