IMPORTANCE OF SEED-BORNE INOCULUM IN THE ETIOLOGY OF THE ASCOCHYTA BLIGHT COMPLEX OF FIELD PEAS (PISUM-SATIVUM L) GROWN IN VICTORIA

Fungi associated with the ascochyta blight complex of field peas were isolated from 436 of 691 seedlots tested. Of the fungi detected, 94.8% of isolates were Mycosphaerella pinodes, 4.2% Phoma medicaginis, and 1.0% Ascochyta pisi. The levels of infestation of seed varied consider ably from year to year and between seedlots, depending on the amount o f rainfall between flowering and maturity. Within a particular pea-gro wing region, the level of seed-borne infection was often highest in se ed from crops harvested latest. In addition, crops sown early were usu ally more severely affected by disease than late-sown crops, and this resulted in higher levels of seed infection. There was no correlation between the level of seed infestation by M. pinodes and the severity o f ascochyta blight; however, where the level of seed infection was hig h (>11%) there was a significant reduction in emergence, which caused a reduction in grain yield. It may therefore be possible to use seed w ith high levels of seed-borne ascochyta blight fungi, provided the see ding rate is increased to compensate for poor emergence.