The role of Neotyphodium endophytes on the interaction of Bromus auleticus withe the pathogenic smut fungi Ustilago bullata and mycorrhizal fungi.

VIGNALE, M.V; NOVAS M.V; PINGET, A.D; ASTIZ GASSO, M.M; DE BATTISTA, J.P; IANNONE, L.J

Lexington, Kentucky

Simposio; International Symposium on Fungal Endophytes of Grasses; 2010

International Symposium on Fungal Endophytes of Grasses

The interactions among endophytes, their hosts and pathogens or mycorrhizal fungi have been mainly studied in agronomic grasses. However this knowledge is limited in native grasses. Numerous grasses native to Argentina are infected with epichloë-endophytes. Among them, Bromus auleticus is a promising forage grass and different ecotypes are associated with different Neotyphodium species. In this work we study the role of endophytes on the interaction of B. auleticus with a common plant pathogen (the smut: Ustilago bullata) and with root mutualistic fungi (arbuscular mycorrhizal fungi, AMF). To study the resistance to smuts, E+ and E- seeds from two host ecotypes were inoculated with teliospores. Plants germinated from E+ seeds from the ecotype El Palmar (N. tembladerae infected) presented less mortality than the E- ones, but no differences were observed in mortality between E+ (N. pampeanum) infected and E- plants from "La Pampa" ecotype. However, whereas 100% and 30% of the E- plants from El Palmar and La Pampa ecotypes, respectively, developed smut symptoms on the flowers, no disease symptoms were observed in E+ plants. To study how the endophytes and soil fertilization level affect AMF colonization, E+ and E- seeds of both ecotypes were planted in the field and after seedling emergency two fertilization levels were applied. Mycorrhizal colonization was studied on 4 month-old plants. E+ plants from El Palmar presented a significantly higher frequency of mycorrhizal colonization and also a higher frequency of arbuscules than their E- counterparts. No differences were observed between E+ and E- plants infected with N. pampeanum. Fertilization level did not affect mycorrhizal colonization. These results indicate that N. tembladerae and N. pampeanum protect their hosts against smut fungi. Epichloë-endophytes are considered to suppress mycorrhizal colonization in agronomic grasses, however in this wild native host; endophytes promote or do not affect this symbiosis.