A previously unreported lupin disease—anthracnose (Glomerella cingulata (Stoneman) Spauld. & H. Schrenk; anamorph Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz.)—was first encountered in Poland in July 1995 on white lupin (Lupinus albus L.), grown in experimental fields of the Plant Breeding Station at Wiatrowo. Initially the disease was observed on a few plants or small clusters of plants distributed randomly within the field. Distinct symptoms of anthracnose, including bending of the plant terminal and pinkish-brown lesions on stems, were first observed at the early flowering stage. Diseased stems collapsed, displaying characteristic necrotic, crook-shaped distortions. Field surveys in 1996 indicated the rapid spread of the pathogen within white lupin inbred lines, apparently from natural infection in 1995. Later in the season, symptoms of anthracnose also appeared on yellow (L. luteus L.) and narrow-leafed (L. angustifolius L.) lupins in close proximity to white lupin plots. A fungal pathogen was consistently isolated by plating surface-disinfected symptomatic stem segments on water agar. After 7 to 10 days, heavy sporulation was observed from which a single-spore subculture was made on potato dextrose agar (PDA). Conidia were one-celled, hyaline, and oblong with obtuse or rounded ends, and were 16 to 20 μm in length, consistent with the conidial descriptions of C. gloeosporioides (1). Acervuli were mostly single and setae inconspicuous. Six fungal isolates were selected to complete Koch's postulates. Conidia from PDA cultures were suspended in sterile water agar and injected into surface wounds on the main stem of white lupin plants. Moist cotton was fastened to the inoculation area for 24 h, then plants were placed in a glasshouse. Within 5 to7 days, typical lesions resembling natural symptoms developed. Symptoms did not appear on control plants. The teleomorph stage of the pathogen was not observed in the field or on inoculated plants. The potential risk of lupin seed infection by C. gloeosporioides is indicated from our preliminary bioassays. Blotter tests were done by plating surface-disinfected seeds of three white lupin seed lot (super-elite) samples, collected from experimental fields in two consecutive years. The seed-borne infection by C. gloeosporioides in samples from 1996 ranged from 9 to 12%, in comparison with no detection of seed-borne infection in 1995 samples examined. In many phytosanitary inspections of seed production fields in 1997, a high level of anthracnose, including total epiphytotics and widespread disease in lupin crops countrywide, was observed. This is the first documented report of C. gloeosporioides causing anthracnose on lupins in Poland.
Reference: (1) J. A. von Arx. 1987. Plant Pathogenic Fungi. Beihefte zur Nova Hedvigia. Vol. 87. J. Cramer, ed. Berlin. pp. 218, 220.