Effects of pod infection by Mycosphaerella pinodes on yield components of pea (Pisum sativum)

Yield reduction of pea (Pisum sativum) due to various types of infections b y Mycosphaerella pinodes on pods was assessed. A range of disease severitie s was created on pods of pea plants grown in the glasshouse, by painting th e pods with different concentrations of spore suspensions, at three differe nt pod development stages: lag phase, the beginning of seed filling (BSF) a nd mid-filling of the seeds. Seed number at harvest was reduced only if the pods were infected before BS F, as shown previously for whole plant infections. Pod infections led to in dividual seed weight (ISW) losses from zero (for late infections, at mid-fi lling) to 20% (for earlier infections and severe disease). Infection during the lag phase affected ISW by reducing seed growth rate, whereas infection at BSF tended to reduce the duration of seed filling. There was a linear r elationship between the area under the disease progress curve and the perce ntage decrease in ISW. This model should be complemented by the effect of l eaves and stem infections, in order to predict ISW losses in diseased crop conditions, in which epidemics occur on all aerial parts of the pea plant.