New host record. Black stem due to Phoma medicaginis on lucerne (Medicago sativa) is especially common in the South Island in crops which have been irrigated. It may be of considerable economic importance.

REPRESENTATIVE CULTURES: PDDCC 6631, 6632.

COLONY MORPHOLOGY OA: Colonies 40-60 mm diam. after 7 days. Mycelium; sparse, cottony, olivaceous or sometimes grey at the centre, yellowish at the edge. Dark agar surface shows through the mycelium. Reverse; grey. ME: Colonies 40-60 mm. Mycelium; sparse to dense, cottony, olivaceous to green-olivaceous, dark agar surface visible. Reverse; dark olivaceous to black with a narrow white border. White crystals form in the agar. The amount and rate of crystal formation varies between isolates and in some, none may have formed after 11 days growth. CHLAMYDOSPORES: Sparse, single or in short chains, often taking several weeks to appear. CONIDIA: Variable in shape and size, unicellular or 1-septate with the degree of septation varying between isolates. (5-)5.5-8(-13) x (1.5-)2.5-3.5(-5) µm. PYCNIDIA: Solitary or aggregated in groups of 2-10 with adjacent pycnidia having confluent walls.

OCCURRENCE: Common, causes leaf spotting and stem blackening of many legumes, especially Medicago sativa.

NOTE: P. medicaginis var. pinodella (L.K. Jones) Boerema, which causes stem-rot of Pisum sativum L. and Trifolium pratense L., may sometimes be found incidently on, and successfully inoculated into, other legumes including Medicago sativa. This species always produces numerous chlamydospores and shows abundant crystal formation after 1 week's growth (Boerema et al. 1965).