263 SummaryPollen-and seed-mediated transgene flow is a concern in plant biotechnology. We report here a highly efficient 'genetically modified (GM)-gene-deletor' system to remove all functional transgenes from pollen, seed or both. With the three pollen-and / or seed-specific gene promoters tested, the phage CRE/ loxP or yeast FLP/ FRT system alone was inefficient in excising transgenes from tobacco pollen and/or seed, with no transgenic event having 100% efficiency. When loxP-FRT fusion sequences were used as recognition sites, simultaneous expression of both FLP and CRE reduced the average excision efficiency, but the expression of FLP or CRE alone increased the average excision efficiency, with many transgenic events being 100% efficient based on more than 25 000 T 1 progeny examined per event. The 'GM-gene-deletor' reported here may be used to produce 'non-transgenic' pollen and/or seed from transgenic plants and to provide a bioconfinement tool for transgenic crops and perennials, with special applicability towards vegetatively propagated plants and trees.
Background To efficiently protect and exploit germplasm resources for marker development and breeding purposes, we must accurately depict the features of the tea populations. This study focuses on the Camellia sinensis ( C. sinensis ) population and aims to (i) identify single nucleotide polymorphisms (SNPs) on the genome level, (ii) investigate the genetic diversity and population structure, and (iii) characterize the linkage disequilibrium (LD) pattern to facilitate next genome-wide association mapping and marker-assisted selection. Results We collected 415 tea accessions from the Origin Center and analyzed the genetic diversity, population structure and LD pattern using the genotyping-by-sequencing (GBS) approach. A total of 79,016 high-quality SNPs were identified; the polymorphism information content (PIC) and genetic diversity (GD) based on these SNPs showed a higher level of genetic diversity in cultivated type than in wild type. The 415 accessions were clustered into three groups by STRUCTURE software and confirmed using principal component analyses (PCA)—wild type, cultivated type, and admixed wild type. However, unweighted pair group method with arithmetic mean (UPGMA) trees indicated the accessions should be grouped into more clusters. Further analyses identified four groups, the Pure Wild Type, Admixed Wild Type, ancient landraces and modern landraces using STRUCTURE, and the results were confirmed by PCA and UPGMA tree method. A higher level of genetic diversity was detected in ancient landraces and Admixed Wild Type than that in the Pure Wild Type and modern landraces. The highest differentiation was between the Pure Wild Type and modern landraces. A relatively fast LD decay with a short range (kb) was observed, and the LD decays of four inferred populations were different. Conclusions This study is, to our knowledge, the first population genetic analysis of tea germplasm from the Origin Center, Guizhou Plateau, using GBS. The LD pattern, population structure and genetic differentiation of the tea population revealed by our study will benefit further genetic studies, germplasm protection, and breeding. Electronic supplementary material The online version of this article (10.1186/s12870-019-1917-5) contains supplementary material, which is available to authorized users.
Stachybotrys (asexual Hypocreales) has a worldwide distribution. This genus inhabits substrates rich in cellulose and is closely related to Memnoniella. Classification of species has previously been based on morphology, with conidial characters being considered as important. This study reevaluates Stachybotrys and Memnoniella, which is shown to include at least seven species-groups; while Memnoniella is a synonym of Stachybotrys. The sexual genera Ornatispora and Melanopsamma are also synonyms of Stachybotrys. With the exception of Stachybotrys subsimplex, species formed a wellsupported monophyletic group in LSU data analysis belonging to Stachybotriaceae. Seventy-four accepted Stachybotrys species are discussed, while eight species are considered to belong to other genera or are doubtful in this paper and a key to these species provided. Twelve new combinations and 1 nomina nova is proposed. The status of Stachybotrys species on health, as human or animal pathogens, in indoor environments, and use as biocontrol agents and compound discovery are also discussed.
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