Georgofili World

Newsletter of the Georgofili Academy

Mass propagation of giant reed (Arundo donax L.), an invasive species suitable for biomass production

Arundo donax (L.), known also as giant reed, is a perennial rhizomatous species which has recently been indicated as the most suitable for the production of biomass to be converted in heat, electricity and biofuel, as well as for the recovering of soils contaminated with heavy metals. Regardless the objectives and the agronomical implications of its cultivation, a crucial problem not yet solved is how to propagate efficiently young plants to be utilized for industrial plantations establishment.
 In fact, giant reed doesn’t produce fertile flowers and viable seeds in large area of the world, and in nature its propagation simply occurs by rhizomes and cane cuttings. Possibly, these are the causes of its reduced genetic variability and of the large diffusion in many countries, where it grows spontaneously in different climatic conditions. 
The establishment of giant reed cultivations requires a very high number of young plants/ha (15,000 – 20,000) and thus, a suitable nursery technique has to be highly efficient, particularly as concerns plant multiplication rate and low production costs. Although giant reed propagates very easily, such a technique is not yet pointed out.
The use of the rhizome as propagating material has shown to perform very well. Plants obtained by this technique establish easily in the soil and produce conspicuous amounts of biomass even after the first year from plantation. Rhizomes collection, selecting and soil planting operations can be assisted by specialized machines which significantly reduce the costs of propagation. Nevertheless, the total costs of this technique still need to be better evaluated as the planting rhizomes have to be supplied from dedicated plantations, which require to be established and managed. 
As it concerns cane cutting propagation, experimental evidences have pointed out interesting results together with some points of weakness as well. Most important limitations would be represented by the slighter amount of biomass produced by cutting propagated plants, compared to that obtained from plants propagated by rhizome, during the first and second year from plantation. Moreover, cane cutting propagation, likely rhizome, can only be performed during restricted periods of the year and it requires a conspicuous availability of mother plants. Procedures suggested for cane cuttings propagation are laborious as well; furthermore, the establishment of the plants in the soil is variable and it depends on cutting age and size, on irregular lateral bud bursting that is often scant, and some time on scarce shoot rooting that doesn’t occur on all the cane nodes.
An efficient alternative to traditional techniques of propagation of giant reed is micropropagation, as observed at the in vitro culture laboratory of the Department of Agriculture, Food and Environment of Pisa (Italy) University. Giant reed adapts easily to this technique, showing significant shoot multiplication rates and rooting performances. Interestingly, in vitro cane cultures have proved to be competent to develop new shoots and adventitious roots at the same time, allowing the overcoming of a specific rooting phase. Most attractive peculiarities of cane micropropagation are represented by the remarkable multiplication potential of this technique, which enable the production of large amounts of plants all over the year, in small room and short period of time, even starting from few buds. Moreover, it has been observed that young micropropagated plants suitably acclimated, can produce significant amount of biomass even at the end of the first year from plantation. So far, although agronomical results and costs of micropropagated plants need further validation, micropropagation appears to be the most efficient technique of propagation of giant reed, suitable to satisfy the request of very high numbers of good quality plants to establish cane industrial plantations. 

Stefano Morini -