Morphological and physiological traits determine Arundo drought recovery

Arundo donax is a plant that may work as a biomass crop in drought-prone marginal lands. However, there is not much variation in the plant. “The clonal reproduction of A. donax may have impaired its development as a biomass crop due to a lack of genetic diversity that can be exploited in breeding more productive and/or drought-tolerant varieties…,” said Haworth and colleagues in the Annals of Botany. “However, previous studies have reported variation in the biomass yield of A. donax ecotypes collected from different habitats…” The scientists investigated what variation there is to see the effect of traits from three different ecotypes on drought tolerance.

“We conducted a common garden experiment in Catania, Sicily, Italy, to assess the morphological and physiological characteristics of the Moroccan, Sicilian and Tuscan A. donax ecotypes and whether any variation in traits could be utilized in the development of more productive and/or drought-tolerant genotypes (a so-called ‘ideotype’),” said the authors. The ecotypes came from Marrakesh, Mount Etna and Florence, and were grown at the agricultural research station of the University of Catania.

“The largest biomass yield was observed in the Moroccan ecotype which exhibited the tallest but also the lowest density of stems,” said Haworth and colleagues. “Moreover, stem height was the only morphological parameter that significantly contributed to yield and, as one of the few heritable traits found in A. donax…), may represent a key attribute for exploitation in attempts to increase biomass yield. The Moroccan ecotype has been shown to have more xylem vessels with a higher diameter than the Tuscan A. donax under both well-watered and drought-stressed conditions … The greater cross-sectional area of the xylem vessels in the Moroccan ecotype may reflect the influence of selective pressures induced by growth in an arid environment where water is available for growth for relatively short periods.”

While these are useful traits, the team concluded that no single ecotype could be described as an ideotype. They all had their flaws. “While the Moroccan ecotype produced the longest stems and largest yield, it also showed the most pronounced downregulation of photosynthetic capacity and reduction in leaf gas exchange later in the year. The Sicilian ecotype retained photosynthetic capacity and P_N later in the year, and also emitted less previously fixed carbon as isoprene, but developed shorter stems than its Moroccan counterpart.”

The authors conclude there is room for selective breeding, either through genetic or mutagenic approaches.