Biology subjects

Giani, S.

Publications and source records attributed to Giani, S..

3 recordsLinked to original sources

bioRxiv2025

Hybridity of mainly asexually propagating duckweeds in genus Lemna - dead end or breakthrough?

O_LIThe cosmopolitan, mainly vegetatively propagating, organ-reduced monocotyledonous aquatic duckweeds are the smallest and fastest growing angiosperms, distributed world-wide and flower rarely in nature. Recently, we reported intra- and interspecific hybrids and ploidy variants in the genus Lemna. Thus, contrary to the expectation, sexual propagation may occasionally occur within and between Lemna species. Our main goal was to uncover whether the ecologically successful hybrids are evolutionary dead ends, or initiate further speciation and novel sexual recombination. C_LIO_LIWe investigated flower development, pollen viability, seed set and seed germination in hybrids and their parental species and characterized genome size and genetic markers in the progenies. C_LIO_LIIntraspecific crosses yielded fertile progeny, but all dihaploid and triploid interspecific hybrids were male sterile. Only an established allotetraploid hybrid reproduced sexually, while colchicine-induced allotetraploids from dihaploids did not re-gain sexual competence so far. C_LIO_LIWe concluded that only established allotetraploid hybrids represent an evolutionary break-through in duckweeds. Our results regarding sexual traits within the duckweed genus Lemna, and the sexual competence of diverse hybrids i) pave the way for further investigation in this understudied field, ii) provide fundamental data regarding the evolutionary potential of duckweed hybrids and iii) are important for future breeding efforts on this emerging crop. C_LI

evolutionary biology↗

bioRxiv2025

Genome diversity and phylogeny of the section Alatae of genus Lemna (Lemnaceae), comprising the presumed species Lemna aequinoctialis, Le. perpusilla and Le. aoukikusa

O_LIThe Section Alatae of genus Lemna of the monocotyledonous aquatic duckweed family (Lemnaceae) consists of rather diverse accessions with unknown phylogeny and unclear taxonomic assignment. In contrast to other duckweeds, some Alatae accessions, in addition to mainly vegetative propagation, produce readily flowers and viable seeds. We analyzed the genomic diversity and phylogenetic relationship of 52 Alatae accessions. C_LIO_LIFor this purpose, we applied multiple molecular and cytogenetic approaches, including plastid and nuclear sequence polymorphisms, chromosome counting, genome size determination and genomic in situ hybridization in combination with geographic distribution. C_LIO_LIWe uncovered ploidy variation, recurrent hybridization, and backcrosses between diploid species and their hybrids. The latter successfully spread over three continents. C_LIO_LIThe results elucidate the evolution of Alatae accessions (summarized in Fig. 7) and explain the difficult taxonomic assignment of distinct accessions. Our study might be an example for analogous studies to resolve the hitherto unclear relationships among accessions of the duckweed genera Wolffiella and Wolffia. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=166 SRC="FIGDIR/small/632899v1_fig7.gif" ALT="Figure 7"> View larger version (23K): org.highwire.dtl.DTLVardef@d05f08org.highwire.dtl.DTLVardef@f33c5org.highwire.dtl.DTLVardef@ff7adorg.highwire.dtl.DTLVardef@4da6e4_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 7C_FLOATNO Hypothetical scenario of evolution within Lemna Section Alatae. In bold are accessions from America. The classically defined diploid species Le. aequinoctialis and Le. perpusilla sensu stricto were confirmed by the applied molecular methods. The previously named Le. aoukikusa accessions were uncovered as tetraploid interspecific hybrids between Le. aequinoctialis and Le. perpusilla. In addition, further tri- and tetraploid hybrids as well as tri- and tetraploid "Backcross hybrids" were detected from the USA and China, respectively. C_FIG

evolutionary biology↗

bioRxiv2023

Characterization of the cryptic interspecific hybrid Lemna x mediterranea by an integrated approach provides new insights into duckweed diversity

Lemnaceae taxonomy is challenged by the particular morphology of these tiny free-floating angiosperms, reduced to a single leaf-like structure called frond, without or with one to few roots. Although molecular taxonomy has helped clarify the phylogenetic history of this family, inconsistency between morphological data and nuclear and plastid markers still poses challenging questions in some cases, leading to frequent misclassifications in the genus Lemna. Recently, the finding that Lemna japonica is an interspecific hybrid between Lemna minor and Lemna turionifera, provided a clear explanation to one of such taxonomic questions. Here we demonstrated that L. minor is also capable to hybridize with Lemna gibba, generating a cryptic, previously unrecognized, but widespread taxon in the Mediterranean area. The nothotaxon Lemna x mediterranea is described through the detailed investigation of seven hybrid clones from a living germplasm collection and compared with clones of the putative parental species L. minor and L. gibba. Genetic analysis revealed that two different cytotypes, diploid and triploid, originated by at least two independent hybridization events. Despite high overall similarity, morphometrical, physiological and biochemical analyses showed an intermediate position of L. x mediterranea between its parental species in most qualitative and quantitative characters, and also separation of the two hybrid cytotypes by some criteria. These data provide evidence that hybridization and polyploidization, driving forces of terrestrial plant evolution, contribute to the duckweed genetic diversity and may have also shaped the phylogenetic history of these mainly asexual, aquatic plants. Further elucidation of hybridization mechanisms and flowering regulation will provide perspectives for future breeding strategies.

plant biology↗