Poster #19

Arbuscular mycorrhizas in the invasive grass Cynodon dactylon
S. GARCÍA; F. PEZZANI; A. GUIDO; F. A. LATTANZI
Facultad de Agronomía. Universidad de la República. Uruguay

Natural grasslands (NG) are the major Uruguayan ecosystem and support one of the most important economic activities of the country: livestock production. An extended agronomic practice to increase forage productivity and nutritive value of these natural grasslands is the addition of exotic legumes and P fertilizer (NG+LP). The exotic grass Cynodon dactylon is the most widespread invasive plant species in Uruguays and NG+LP practices promote its invasion. Arbuscular mycorrhiza (AM) play an important role in the establishment and spread of invasive species at local scale, mainly when invasive plants are low dependent on AM symposis. The objective of this work was to evaluate the mycorrhizal status of C. dactylon and to study the effects of NG+LP practices on AM in C. dactylon. C. dactylon roots and leaves were sampled from 3 NG plots and in 3 adjacent NG + LP plots to study total mycorrhizal colonization, colonization by fungi structures and plant nutrient content. AM presence and nutrients contents in C. dactylon were not affected by NG+LP practices. Total mycorrhizal colonization average was 46%, while the fungal exchange structures colonization was, around 1 %, suggesting that this invasive grass would be allocating low energy to mycorrhizal fungi.