Creation of New Oregano Genotypes with Different Terpene Chemotypes via Inter- and Intraspecific Hybridization.

Oregano is a medicinal and aromatic plant of value in the pharmaceutical, food, feed additive, and cosmetic industries. Oregano breeding is still in its infancy compared with traditional crops. In this study, we evaluated the phenotypes of 12 oregano genotypes and generated F1 progenies by hybridization. The density of leaf glandular secretory trichomes and the essential oil yield in the 12 oregano genotypes varied from 97-1017 per cm2 and 0.17-1.67%, respectively. These genotypes were divided into four terpene chemotypes: carvacrol-, thymol-, germacrene D/ß-caryophyllene-, and linalool/ß-ocimene-type. Based on phenotypic data and considering terpene chemotypes as the main breeding goal, six oregano hybrid combinations were performed. Simple sequence repeat (SSR) markers were developed based on unpublished whole-genome sequencing data of Origanum vulgare, and 64 codominant SSR primers were screened on the parents of the six oregano combinations. These codominant primers were used to determine the authenticity of 40 F1 lines, and 37 true hybrids were identified. These 37 F1 lines were divided into six terpene chemotypes: sabinene-, ß-ocimene-, γ-terpinene-, thymol-, carvacrol-, and p-cymene-type, four of which (sabinene-, ß-ocimene-, γ-terpinene-, and p-cymene-type) were novel (i.e., different from the chemotypes of parents). The terpene contents of 18 of the 37 F1 lines were higher than those of their parents. The above results lay a strong foundation for the creating of new germplasm resources, constructing of genetic linkage map, and mapping quantitative trait loci (QTLs) of key horticultural traits, and provide insights into the mechanism of terpenoid biosynthesis in oregano.

Fingerprint construction through genotyping by sequencing for applied breeding in Brassica rapa.

This study evaluated the genotyping by sequencing (GBS) protocol for fingerprinting Brassica rapa, and the data derived were more reliable than the re-sequencing data of B. rapa. Of the 10 enzyme solutions used to analyze the numbers of genotypes and single-nucleotide polymorphisms (SNPs) in B. rapa, five solutions showed better results, namely, A (HaeIII, 450-500 bp), E (RsaI+HaeIII, 500-550 bp), F (RsaI+HaeIII, 500-600 bp), G (RsaI+HaeIII, 'All' fragment), and J (RsaI+EcoRV-HF®, 'All' fragment). The five enzyme solutions showed less than 40% similarity in different individuals from various samples, and 90% similarity between two individuals from one sample. The E enzyme solution was the most suitable for fingerprinting B. rapa, revealing well-distributed SNPs in the whole genome. Of the 82 highly inbred lines and 18 F1 lines of B. rapa sequenced by GBS in the E enzyme solution, known parents of 10 F1 lines were verified, and male parents were discovered for 8 F1 lines that had only known female parents. This study provides a valuable method for screening parents for F1 lines in B. rapa for the efficient evaluation of GBS with varied library construction strategies.