Genetic diversity, cytogenetics, and biomass yields among taxa of giant reeds (Arundo species).

Genetic diversity and cytogenetics of 31 accessions of Arundo L. , collected from North America and South Asia, were characterized using 20 intersimple sequence repeat (ISSR) markers, flow cytometry, and cytology. In addition, field trials of 23 Arundo donax L. accessions were established in 2011 and harvested in 2012 to 2013 to assess annual biomass yields. Cluster analysis, based on Jaccard’s similarity coefficient method, clearly differentiated Arundo formasana Hack. from A. donax and a third unidentified Arundo taxon. Arundo donax further contained two subgroups representing North American (naturalized and cultivated) and South Asian collections. Within each A. donax subgroup, genetic distances were very low (0.03 for North America and 0.07 for South Asia). Principle coordinate analysis further supported distinct clusters. Relative genome sizes were determined usingPisum sativumL. as the reference genome and 6-diamidino-2-phenylindole (DAPI) fluorochrome. Chromosome numbers (2n), ploidy levels, and 2C relative genome sizes ranged from ’62 to 105, near 12x to near 18x, and 2.78 to 4.13 pg, respectively, and were similar within each taxa/subgroup. While there was a low level of genetic variability among A. donax accession, dry biomass yields varied significantly ranging from 6.5 to 65 Mg ha per year for the third growing season. Arundo species are perennial rhizomatous grass belonging to the tribe Arundinae (subfamily Arundinoideae: Poaceae) (Barker et al., 1999). Arundo donax, in particular, is one of the largest of the herbaceous grasses (Perdue, 1958), growing in dense clumps and attaining heights of up to 8–9 m (Lewandowski et al., 2003). With such impressive growth rates, A. donax is a leading candidate for cultivated biomass in Mediterranean climates (Angelini et al., 2009; Cosentino et al., 2006) and is also being considered as an energy crop in North America (Gilbert at al., 2008; Lewandowski et al., 2003). Many of the advantages of A. donax as an energy crop include a high yield potential (up to 63.1 Mg ha of dry matter), high lignin and cellulose content, rapid growth rate (up to 0.7 m week under favorable conditions), high carbon sequestration, widely adaptable to marginal sites, low irrigation and nutrient requirements, and minimal soil tillage, (Lewandowski et al., 2003). Arundo donax is generally found in alluvial, riparian habitats, such as along the borders of lakes or ditches, but can tolerate a wide range of diverse ecological conditions (Perdue, 1958; Vollmer et al., 2008). The native origin of A. donax has been variously reported as southern Asia (Bell, 1997; Dudley, 2000), eastern Asia (Polunin and Huxley, 1987), and countries surrounding the Mediterranean Sea (Perdue, 1958), though a recent study has provided evidence that A. donax likely originated in Asia and subsequently spread into the Mediterranean region (Mariani et al., 2010). A. donax also has beenwidely dispersed by humans throughout subtropical and warm-temperate regions for diverse applications including musical instruments, paper and pulp, and woven baskets (Perdue, 1958). In North America, A. donax was introduced into southern California in the early 1800s for erosion control with latter introductions being made in Texas and Florida as late as the 1940s (Bell, 1997; Perdue, 1958). Since its introduction, giant reed has beenwidely cultivated in North America and has escaped cultivation in some areas (Perdue, 1958). Genetic diversity is important for the selection, cultivation, and potential breeding of A. donax with desirable traits including high biomass yields, resistance to pest and diseases, and regional adaptability. Unfortunately, a low level of genetic diversity has been reported for A. donax in southern North America and southern Europe (Ahmad et al., 2008; Hardion Received for publication 25 Sept. 2015. Accepted for publication 19 Feb. 2016. We thank BP Biofuels North America, the Biofuels Center of North Carolina, and the North Carolina Department of Agriculture and Consumer Services for