Tw. Bretag et al., IMPORTANCE OF SEED-BORNE INOCULUM IN THE ETIOLOGY OF THE ASCOCHYTA BLIGHT COMPLEX OF FIELD PEAS (PISUM-SATIVUM L) GROWN IN VICTORIA, Australian journal of experimental agriculture, 35(4), 1995, pp. 525-530
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.