Development and characterization of microsatellite markers for Solen grandis using Illumina sequencing approach.

Solen grandis is an important economic and overexploited bivalve species. In order to perform its fine-scale genetic analyses, 105 pairs of microsatellites with polymorphism were identified through Illumina Hiseq platform and bioinformatic assembly technology in this study. The estimated fragment size ranged from 100 to 268 bp and the number of alleles per locus varied between 2 and 23. Observed and expected heterozygosities varied from 0.0667 to 1.0000 and 0.0966 to 0.9492, respectively. Fourteen loci deviated significantly from Hardy-Weinberg equilibrium after Bonferroni correction. These microsatellite markers developed in this study would be helpful for future genetic studies on S. grandis and closely related species.

Mapping of quantitative trait loci for the bolting trait in Brassica rapa under vernalizing conditions.

Premature bolting can occur occasionally during spring cultivation of heading Chinese cabbage in East Asia when the plants encounter low temperatures (vernalization), leading to economic loss. Breeding bolting-resistant cultivars is the best choice for solving this problem. We looked for QTLs responsible for varietal differences in the bolting trait in Brassica rapa under environmental conditions that promote vernalization. To achieve this goal, we constructed a linkage map with 107 simple sequence repeats and 54 insertion/deletion markers based on a segregating population of 186 F2 individuals. The resulting map consisted of 10 linkage groups and covered a total length of 947.1 cM, with an average genetic distance of 5.84 cM between adjacent markers. QTL analysis of the bolting trait was performed by two phenotypic evaluations (bolting index and flowering time) based on the scores in an F2 population in the spring of 2010, and scores in F2:3 families in autumn 2010 and spring 2011, respectively. Twenty-six QTLs that controlled bolting were detected, accounting for 2.6 to 31.2% of the phenotypic variance. The detected QTLs with large effects co-localized mainly on linkage groups A02, A06, and A07. These QTLs may provide useful information for marker-assisted selection in a breeding program for late bolting or bolting-resistant cultivars in B. rapa crops.

Analysis of sequence diversity through internal transcribed spacers and simple sequence repeats to identify Dendrobium species.

The Orchidaceae is one of the largest and most diverse families of flowering plants. The Dendrobium genus has high economic potential as ornamental plants and for medicinal purposes. In addition, the species of this genus are able to produce large crops. However, many Dendrobium varieties are very similar in outward appearance, making it difficult to distinguish one species from another. This study demonstrated that the 12 Dendrobium species used in this study may be divided into 2 groups by internal transcribed spacer (ITS) sequence analysis. Red and yellow flowers may also be used to separate these species into 2 main groups. In particular, the deciduous characteristic is associated with the ITS genetic diversity of the A group. Of 53 designed simple sequence repeat (SSR) primer pairs, 7 pairs were polymorphic for polymerase chain reaction products that were amplified from a specific band. The results of this study demonstrate that these 7 SSR primer pairs may potentially be used to identify Dendrobium species and their progeny in future studies.