Studies on the Cytology and Phylogeny of South Indian Grasses

Genetic Improvement of Arundo donax L.: Opportunities and Challenges

Arundo donax L., the giant reed-being a long-duration, low-cost, non-food energy crop able to grow in marginal lands-has emerged as a potential alternative to produce biomass for both energy production, with low carbon emissions, and industrial bioproducts. In recent years, pioneering efforts have been made to genetically improve this very promising energy crop. This review analyses the recent advances and challenges encountered in using clonal selection, mutagenesis/somaclonal variation and transgenesis/genome editing. Attempts to improve crop yield, in vitro propagation efficiency, salt and heavy metal tolerance by clonal selection were carried out, although limited by the species' low genetic diversity and availability of mutants. Mutagenesis and somaclonal variation have also been attempted on this species; however, since Arundo donax is polyploid, it is very difficult to induce and select promising mutations. In more recent years, genomics and transcriptomics data are becoming available in Arundo, closing the gap to make possible the genetic manipulation of this energy crop in the near future. The challenge will regard the functional characterization of the genes/sequences generated by genomic sequencing and transcriptomic analysis in a complex polyploid genome.

Impact of polyploidy on fertility variation of Mediterranean Arundo L. (Poaceae)

Failure of seed production in the genus Arundo L. (Poaceae) is often attributed to polyploidy. This study tested the impact of two ploidy levels (2n=12 and 18x) on the fertility of four Mediterranean Arundo. Viable pollen was screened from its production to its germination, and seed occurrence was monitored in admixture or isolated conditions. In addition, insights on restructuration of polyploid genomes were analysed using molecular cytogenetics. Our results show that high ploidy levels do not automatically induce failure of sexual reproduction. The two ploidy levels are able to produce viable pollen and seed set depending on species and cultural conditions. The sterility of A. micrantha (2n=12x) and A. donax (2n=18x) is due to the early failures of gametogenesis steps. For 18x cytotypes of A. donaciformis and A. plinii, seed absence for isolated genotype vs. seed production in admixed culture support their auto-incompatibility.

Arundo donax L.: a non-food crop for bioenergy and bio-compound production

Arundo donax L., common name giant cane or giant reed, is a plant that grows spontaneously in different kinds of environments and that it is widespread in temperate and hot areas all over the world. Plant adaptability to different kinds of environment, soils and growing conditions, in combination with the high biomass production and the low input required for its cultivation, give to A. donax many advantages when compared to other energy crops. A. donax can be used in the production of biofuels/bioenergy not only by biological fermentation, i.e. biogas and bio-ethanol, but also, by direct biomass combustion. Both its industrial uses and the extraction of chemical compounds are largely proved, so that A. donax can be proposed as the feedstock to develop a bio-refinery. Nowadays, the use of this non-food plant in both biofuel/bioenergy and bio-based compound production is just beginning, with great possibilities for expanding its cultivation in the future. To this end, this review highlights the potential of using A. donax for energy and bio-compound production, by collecting and critically discussing the data available on these first applications for the crop.

Origin of the invasive Arundo donax (Poaceae): a trans-Asian expedition in herbaria

BACKGROUND AND AIMS

The hypothesis of an ancient introduction, i.e. archaeophyte origin, is one of the most challenging questions in phylogeography. Arundo donax (Poaceae) is currently considered to be one of the worst invasive species globally, but it has also been widely utilzed by man across Eurasia for millennia. Despite a lack of phylogenetic data, recent literature has often speculated on its introduction to the Mediterranean region.

METHODS

This study tests the hypothesis of its ancient introduction from Asia to the Mediterranean by using plastid DNA sequencing and morphometric analysis on 127 herbarium specimens collected across sub-tropical Eurasia. In addition, a bioclimatic species distribution model calibrated on 1221 Mediterranean localities was used to identify similar ecological niches in Asia.

KEY RESULTS

Despite analysis of several plastid DNA hypervariable sites and the identification of 13 haplotypes, A. donax was represented by a single haplotype from the Mediterranean to the Middle East. This haplotype is shared with invasive samples worldwide, and its nearest phylogenetic relatives are located in the Middle East. Morphometric data characterized this invasive clone by a robust morphotype distinguishable from all other Asian samples. The ecological niche modelling designated the southern Caspian Sea, southern Iran and the Indus Valley as the most suitable regions of origin in Asia for the invasive clone of A. donax.

CONCLUSIONS

Using an integrative approach, an ancient dispersion of this robust, polyploid and non-fruiting clone is hypothesized from the Middle East to the west, leading to its invasion throughout the Mediterranean Basin.