Leptosphaeria nodorum infection of wheat in New Zealand

Abstract

Perithecia of Leptosphaeria nodorum Müller were found in autumn on leaf debris in stubble of the wheat cultivar Aotea, although no symptoms of Septoria nodorum (Berk.) Berk, apud Berk, and Br., the asexual stage, were found in the growing crop. Volunteer wheat plants did, however, produce symptoms of S. nodorum the following spring but pycnidia were produced only when the infected leaves were excised and placed in detached leaf culture under near ultraviolet light for 12 h per day. Conidia from these pycnidia and ascospores from the perithecia were cultured on a variety of agar media where they all produced cultures and pycnidia were identified as S. nodorum. Inoculation experiments with spore suspensions from both sources were successful and produced typical S. nodorum symptoms. Further tests showed that 18–24°c, light, senescing tissue, and humidity were all important factors governing the appearance of pycnidia in detached leaf cultures.