Date Published: April 9, 2019
Publisher: Public Library of Science
Author(s): Francesco Guarino, Angela Cicatelli, Giuseppe Brundu, Giovanni Improta, Maria Triassi, Stefano Castiglione, Massimo Labra.
Among the most widespread plant species with clonal reproduction Arundo donax L. represents one of most studied one characterized by very low genetic biodiversity. Although it is a perennial rhizomatous tall grass native to eastern and southern Asia, it spreads only asexually in the invaded range all over the world thriving very well in a large array of pedo-climatic conditions. This ability to morphologically or physiologically adapt to a broad array of conditions could be attributed to epigenetic mechanisms. To shade light on this relevant issue, 96 stems of A. donax from spontaneous populations distributed across the Italian invaded range (island of Sardinia, Northern and Southern Italy) were analysed. Leaf DNAs were extracted and processed through AFLPs and MSAPs for defining either genetic and epigenetic profiles. Both analyses clearly showed that the A. donax populations of Sardinia island are genetically distinct from those of Italian mainland; AFLPs showed an extremely low genetic biodiversity due to vegetative reproduction, whilst, epi-biodiversity, estimated through MSAP marker, increased within the analyzed populations. These results suggest that the capability of A. donax to invade and thrive in diverse environmental conditions can be, at least, partially attributed to a higher epigenetic variability. Therefore, the different DNA methylation status may have significant and important biological meaning, in particular, in the case of invasive clonal plants such as A. donax, also for the biodiversity definition, and MSAP marker can be considered an useful and cost effective marker to reveal it.
Arundo donax L. (Poaceae, subfamily Arundinoideae), also known as giant reed, is a perennial rhizomatous tall grass, native to eastern and southern Asia [1, 2]. It has been introduced and grown for local uses in the Mediterranean region since ancient times; traditional uses of A. donax include basket work, roofing, trellises, musical instruments and traditional medicine, and more recently it started to attract attention in Europe as a potential non-food crop and for biomass production . As a result of this human-mediated spread it is now widely naturalized around the world in areas of North and South America, Asia, Africa, Australia, New Zealand and numerous islands across the Pacific . Although well adapted to widely different ecological conditions, it is basically thrives in riparian habitats, where it forms dense monospecific stands [5, 6]. Its flowers are perfect , but neither pollen nor caryopsis have been documented in North America  and in other parts of the invaded range (e.g., for Europe ). For this reason, it is considered a sterile plant, which spreads only asexually, through rhizomes at the close proximity of the invaded area and by stem fragments, which can be distributed by water or through human activities at considerable distance from the primary invaded area. Vegetative reproduction is expected to reduce the genetic biodiversity because of absence meiotic mechanisms and, in particular, of its fundamental phases such as crossing over and gene recombination. A relevant number of studies have demonstrated that there is very little genetic variation in A. donax in the invaded range, e.g., in Australia [4, 10].
The ninety-six specimens of A. donax, collected in Italy from 14 populations were analyzed using AFLP and MSAP molecular markers. The AFLP profiles provided molecular data useful for estimating the biodiversity and the population structure in relation to genetic diversity, while, the MSAP profiles (EcoRI/MspI and EcoRI/HpaII) reflected DNA methylation variability.
Plants in general, and in particular the invasive riparian one, may have developed molecular processes to adapt themselves in order to colonize new and frequently changing habitats. Epigenetic mechanisms are, very likely, the trigger of a series of complex molecular mechanisms that allow plants to thrive in sometimes harsh conditions. In order to understand whether epigenetic biodiversity, rather than genetic diversity, might better explain the invasive success of the archaeophyte A. donax in Italy, we analysed 96 individuals from 14 naturalized populations using AFLP (EcoRI/MseI–genetic diversity) and MSAP (EcoRI/MspI and EcoRI/HpaII–epigenetic diversity).