Nonreduction via meiotic restitution and pollen heterogeneity may explain residual male fertility in triploid marine halophyte Limonium algarvense (Plumbaginaceae)
Keywords:Apomixis, In vitro pollen germination, Limonium, Male sporogenesis and gametogenesis, Meiotic restitution, Polyploidy
The cosmopolitan halophylic genus Limonium (Plumbaginaceae) presents high cytogenetic interest because of the natural occurrence of diploid and polyploid variants. Natural triploids are very rare in nature but common in this genus, including the widespread triploid Limonium algarvense found in the Iberian Peninsula and in Morocco. This study describes male sporogenesis and gametogenesis, pollen formation and germination, and seed production in triploid L. algarvense and diploid Limonium ovalifolium using various cytological approaches. The diploid species presented regular meiosis. The triploid species was defective in male meiosis due to unpaired chromosomes, trivalent and tetravalent pairing, unbalanced chromosome segregation in meiosis I, and meiotic restitution in both meiosis I and II. These results may be explained by indeterminate and broad first meiotic restitution. Dyads and restitution nuclei at meiosis I were the most frequent meiotic products in the triploid species. Cytomixis was observed in both species, and callose deposition did not differ among them. In the diploid species, regular, tricolpate pollen grains, which germinated in vitro were found. Contrastingly, the triploid species produced heterogeneous pollen in morphology and size, with moderate to no viability that poorly germinated in vitro. We conclude that even if most triploids male gametes are non-functional, they seem to generate small numbers of viable gametes via nonreduction of chromosomes. Flow cytometric seed screening demonstrated that the diploid species presented a diploid progeny whereas triploids only showed triploid progenies. In the triploids low pollen fertility coupled with viable seed production may assure their persistence in natural populations.
How to Cite
- Copyright on any open access article in a journal published byCaryologia is retained by the author(s).
- Authors grant Caryologia a license to publish the article and identify itself as the original publisher.
- Authors also grant any third party the right to use the article freely as long as its integrity is maintained and its original authors, citation details and publisher are identified.
- The Creative Commons Attribution License 4.0 formalizes these and other terms and conditions of publishing articles.
- In accordance with our Open Data policy, the Creative Commons CC0 1.0 Public Domain Dedication waiver applies to all published data in Caryologia open access articles.