In Vitro Propagation of Isoëtes sabatina (Isoetaceae): A Key Conservation Challenge for a Critically Endangered Quillwort

Abstract

Isoëtes sabatina is an aquatic quillwort endemic to Italy. It is one of the rarest quillworts in Europe, and is critically endangered due to restricted range and to the continuous decline of both population and habitat quality. This study aims to develop an optimized protocol to reproduce and grow I. sabatina sporelings. Mature and immature megaspores were mixed with mature microspores to evaluate the influence of the developmental stage on germination and sporeling development. Two substrates, distilled water and water-agar medium, were tested for germination and sporeling emergence, and three substrates, sand, lake sediment and water-agar, were tested for transplants. A high percentage of megaspore germination (a total of 79.1%) was obtained in both substrates, higher for mature than immature spores. A total of 351 sporelings were produced in distilled water and water-agar cultures, with similar percentages (64.5% and 69.6%, respectively). The development stage of the megaspores affected both germination and sporeling development. Sporeling emergence showed significantly higher percentages in mature megaspores than immature ones (69.6% vs. 11.6%, respectively), with 85% of germinated spores developing sporelings. Only transplants over water-agar medium were successful. This protocol could be useful for the propagation of sporelings as the key step towards the planning of in situ actions to save this Mediterranean quillwort from extinction.

Importance of Plants with Extremely Small Populations (PSESPs) in Endemic-Rich Areas, Elements Often Forgotten in Conservation Strategies

“…The few remaining populations of O. vulgatum require urgent conservation action, both to protect and reinforce extant populations and, if possible, to reintroduce new populations into suitable sites. To do this, although there are no specific protocols, the experiences gained in recent years on other small ferns could be exploited (e.g., [ 46 , 47 ]).…”

Distinct Reproductive Strategy of Two Endemic Amazonian Quillworts

“…In this study, we obtained a wide range of variations in sporophyte regeneration from in vitro fertilization assays. Higher rates of sporophyte regeneration have been observed for other species, such as Isoëtes malinverniana [24], Isoëtes lacustris [17], and Isoëtes sabatiana [25], and have been attributed to the use of mature reproductive structures, while immature spores could lead to less effective sporophyte regeneration [15,25] or even to nongermination, as previously reported for I. cangae [14]. Consequently, the lower sporophyte regeneration obtained in some of our experiments could be affected by the use of spores that were not completely developed.…”

Isoëtes sabatina (Isoëtaceae, Lycopodiopsida): Taxonomic distinctness and preliminary ecological insights

“…In Europe, six out of the eight known obligate aquatic Isoëtes species are seriously endangered, occupying very restricted geographical areas (4–56 km 2 ; Table 1). Among them, one, Isoëtes heldreichii Wettst., is considered Critically Endangered (Possibly Extinct) (García Criado et al, 2017) and two, including Isoëtes sabatina Troìa & Azzella, fall into the Critically Endangered category (Troìa & Azzella, 2013; Christenhusz et al, 2017; García Criado et al, 2017; Magrini et al, 2020).…”

“…Consequently, it is essential to acquire genetic data on the taxonomic placement of I. sabatina and on the physical and chemical requirements of its unique population to give this species a chance of survival (Magrini et al, 2020). This was done using a multiple strategy consisting of: (i) molecular phylogenetic analysis (DNA barcoding) of…”