EFFECT OF PHAEOSPHAERIA-NODORUM-INDUCED SEED SHRIVELING ON SUBSEQUENTWHEAT EMERGENCE AND PLANT-GROWTH

The bread wheat cultivars Pasqua and Katepwa, and durum wheat cultivar s Kyle and D8257 were used to test the effects of sowing Phaeosphaeria nodorum-shrivelled seed. In a controlled environment, emergence, till ering, and dry weight of seedlings were compared at two sowing depths. Emergence, tillering and plant dry weights were also determined in fi eld plots in 1992 and 1993, as were yield and thousand kernel weight ( TKW) in plants inoculated with P. nodorum. Under controlled conditions the level of shrivelling did not affect emergence at depths of 25 mm and, except for Katepwa, 50 mm. Deeper seeding reduced emergence regar dless of the level of shrivelling. Seeding depth did not affect dry we ight of roots and shoots and the effect on tillering was inconsistent in the two years. Dry root weight was positively correlated with origi nal seed size and decreased with level of shrivelling. In the field, s eedling emergence of severely shrivelled seed was significantly lower in Katepwa and Pasqua. Tillers per plant appeared to increase with inc reased level of shrivelling, but was significant only for D8257 in one year. Dry tiller weight was inversely related to tillering and decrea sed consistently with level of shrivelling. Excepting Pasqua, in one y ear, yield and TKW did not differ between plots originating from plump or shrivelled seed. Inoculation with II nodorum caused a significant reduction in TKW and yield in all cultivars but Kyle. Seed shrivelled due to P. nodorum was in general found to be as suitable as plump seed for growing a wheat crop.