To introduce downy mildew resistance from a yellow-colored resistant cultivar, ‘Santero’, into a yellow breeding line, OT803, the F₁ hybrid was produced by crossing Santero and OT803. The bulb color of the F₁ hybrids became light pink, suggesting involvement of complementation between the DFR-A and ANS genes in the onion anthocyanin biosynthesis pathway. Since Santero contained active DFR-A and inactive ANS alleles, OT803 was assumed to harbor active ANS and inactive DFR-A alleles. However, some yellow-colored individuals of OT803 were shown to contain the homozygous genotype of the active DFR-A^R4-like allele. Sequencing of 4,830-bp full-length sequences of this DFR-A^R4-like allele revealed that the nucleotide sequences of the DFR-A^R4 and DFR-A^R4-like alleles were identical except for a single nucleotide deletion in the last exon. This single base-pair deletion resulted in creation of a premature stop codon at 2-bp downstream of the deletion mutation. This new DFR-A mutant allele was designated DFR-A^PS2. The RT-PCR results showed that transcripts of the DFR-A^PS2 allele were significantly reduced, suggesting involvement of nonsense-mediated mRNA decay (NMD) mechanism. The systematic process consisting of PCR amplification and sequencing of the PCR products was modified to identify the DFR-A^PS2 allele among 16 different DFR-A alleles. No additional accession was found to contain the DFR-A^PS2 allele from 155 diverse onion germplasm, indicating very limited distribution of this new DFR-A^PS2 allele.

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The present study aimed to determine the contents of five flavonols and two glycoalkaloids as well as the antioxidant activities of leaf ethanol extracts of 50 tomato accessions. The antioxidant activity was assessed using different tests: 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 2,2-diphenyl-1-picryl hydrazyl (DPPH), nitric oxide (NO), and total polyphenol content (TPC). Flavonols and glycoalkaloids contents were determined using a high performance liquid chromatography-diode array detector system. Among five flavonols and two glycoalkaloids, naringenin and tomatine were detected in tomato leaves at high concentrations. Of the 50 tomato accessions, IT 229711, IT2365203, and IT 207224 were found to have the highest contents of quercetin, kaempferol, and tomatine, respectively. Leaf extract of IT189949 exhibited the highest relative antioxidant capacity index (RACI). Among the five flavonols, myricetin showed positive correlations with DPPH, ABTS, and NO, while isorhamnetin had positive correlation with DPPH. These results will expand the chemical constitution database and provide information on tomato leaves. They are valuable for the development of functional foods or feed-additives.

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