Ascochyta blight development on a new winter pea genotype highly reactive to photoperiod under field conditions

Winter pea suffers from two main types of damage, due to the length of its cycle and climatic conditions (rainfall periods, leaf wetness duration and frost periods): frost and ascochyta blight (Mycosphaerella pinodes). New winter lines resistant to frost (later flowering varieties) are being bred. They can be sown early in autumn, lengthening the crop cycle and thereby increasing target yields. We analysed the reaction of this new type of winter pea (Hr genotype) to ascochyta blight under field conditions, by comparing epidemic disease development on this genotype with that on the classical cultivars Cheyenne and Dove. We also assessed the effect of sowing date (mid-September, mid-October) on ascochyta blight on these genotypes. Field experiments were carried out at five locations (Dijon, Estrees-Mons, Maisse, Rennes, Toulouse). Disease development, assessed on stipules and stems, differed between experimental locations, ranging from mild to very severe epidemics. Disease levels were highest for the first sowing date for each genotype. The Hr genotype had the lowest level of disease at each experimental site. Ascochyta blight was less affected by sowing date in the Hr genotype than in Cheyenne and Dove. Disease affected seed yield differently in the three genotypes. These results have potential implications for the management of disease on winter pea. (c) 2008 Elsevier B.V. All rights reserved.