FUNGAL SAPROBES AND PATHOGENS AS ENDOPHYTES OF RICE (ORYZA-SATIVA L)

Fungal endophytes have been isolated from inside the leaf blades, leaf sheaths, and roots of six-week-old plants as well as from seeds and ten-day-old seedlings of Oryza sativa (L.). The fungi isolated can be grouped in two categories; one containing organisms known mainly to be saprotrophic and the other comprising potential pathogens. Of the former Alternaria alternata (Fr.) Keissler and Epicoccum purpurascens Ehrenb. ex. Schlecht preferentially colonize the leaf blades of their host, whereas Cladosporium tenuissimum Cooke seems more generally distributed between leaf blades and leaf sheaths. Fusarium equiseti (Corda) Sacc., F. oxysporum Schecht and Phoma sorghina (Sacc. Boerema) are latent in their hosts without causing disease symptoms. A. alternata, E. purpurascens, F. equiseti, and Nigrospora oryzae have also been frequently isolated from seeds and young seedlings and can be considered seed-borne. Principal components analysis has shown a marked tissue specificity among rice endophytes. Leaf sheaths of the rice varieties grown under dry conditions are colonized by endophyte communities different from those of the wet cultivars.