Effects of Ascochyta blight caused by Mycosphaerella pinodes on the translocation of carbohydrates and nitrogenous compounds from the leaf and hull to the seed of dried-pea

The effects of Ascochyta blight (caused by Mycosphaerella pinodes) on changes in dry weight and in water, carbohydrate, nitrogen and free amino acid contents were studied in the leaf, the hull and the seeds on the second fructifer node of pea (Pisum sativum). Pea plants were grown in a glasshouse and inoculated with various concentrations of conidia at the beginning of seed filling, with uninoculated plants as controls. Disease induced a premature water loss of hulls and leaves, accelerated seed desiccation and reduced seed weight. Biochemical analyses revealed a decline in the carbohydrate content and a lower nitrogen remobilization in diseased leaves and hulls. Thus, Ascochyta blight alters carbohydrate metabolism, protein remobilization and free amino acid translocation from these organs. Disease also reduced carbohydrate and nitrogen content in seeds and, in case of high disease severity, the carbohydrate/nitrogen ratio in the seeds was also affected (seed protein concentration increased and starch concentration decreased).