CropsDescription of the fungus
- The perfect shape of Guignardia bidwellii is characterized by spherical perithecia (61-199 µm in diameter) embedded in a stroma (Figures 1 and 2) and opening by a flat ostiole . These perithecia have no paraphyses and contain asques (about 40 to 120 per perithecia). The axes (Figures 3 and 4) are cylindrical and swollen at the apical part (35-72 x 9-17 µm), they contain 8 ascospores (10.6-18.4 x 4.8-9 µm) hyaline, single-celled , oval in shape.
- The imperfect shape produces pycnidia spherical (59-196 µm in diameter), solitary, protruding, black, opened by an ostiole (figures 5 to 9) from which the will escape when ripe pycniospores (figures 10 and 11). These pycniospores are colorless, ovoid (4.5-9.3 x 4.5-5 µm) embedded in a mucilaginous cord (cirrh) of whitish color (figure 7).
On culture medium, the fungus forms a mycelial colony slowly growing black-greenish (Figures 12 and 13). Pycnidia form on the surface of the Petri dish after 10 to 15 days, if the colony is lighted and well attached to the substrate. Finally, these pycnidia sporulate abundantly a week later at 20-25 ° C. Sometimes perithecia can also be obtained in vitro .
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