Results of the first International Scab Resistance Screening Nursery (SRSN) 1985-86

Abstract

Fusarium head scab is a common wheat disease in many parts of the world where the crop is grown at low elevations under wam, humid conditions and lingering cloud cover. The disease is also economically important al high elevations where there is continuous daily rain and predominant doud cover during the wheat growing cycle, especially from flowering to physiological maturity. Scab is caused by various Fusarium species, including F. equiseti, F. culmorum, F. avenaceum, and F. nivale, but it is F. graminearum (perfect stage: Gibberella zeae) that generally causes the major scab epidemics and yield losses. The other species of Fusarium are of lesser importance, and occur only under conditions extremely favorable to their development. Evaluation for resistance to scah disease begant at CIMMYT during the early 1980s. Artificial inoculation methods were developed for the successful generation of artificial epidemics. Thousands of CIMMYT-drived wheats and introduced germplasm were evaluated for resistance under artificially-created epidemics at the Toluca research station of CIMMYT. Germplasm was also especially introduced from those areas where this disease occurs more severely, e.g., China and Brazil. The primary criterion for selecting gennplasm for the Scab Resistence Screening Nursery (SRSN) at this beginning phase was to identify lines with better resistance. This report is a summary of results obtained from the 1st SRSN with respect to various agronomic and disease resistru1ce chamcteristics. It is hoped that some of the material in this nursery will prove to be useful to our cooperators in Scab-endemic regions and the information contained herein will be of service to wheat breeders.