Ba. Peters et al., LEAF DEVELOPMENT IN RELATION TO INFECTION BY STAGONOSPORA-NODORUM ANDSEPTORIA-TRITICI IN WHEAT, Australian Journal of Agricultural Research, 47(7), 1996, pp. 1169-1179
Disease and phenology were compared in 2 wheat cultivars (Aroona and S
pear) differing in disease resistance and maturity, at early (April-Ma
y) to late (June) sowing dates in 1991 and 1992. The cultivars had sim
ilar rates of leaf development but the longer season cultivar Spear av
eraged up to one leaf more on the main stem than the midseason cultiva
r Aroona, depending on sowing date. The extra leaf production which de
layed flag leaf emergence on Spear compared to Aroona at early sowings
was associated with lower disease levels in 1991. The occurrence of l
eaf rust may have diminished this advantage in 1992. Resistance to Sep
toria tritici in Aroona did not affect disease progress compared to Sp
ear. A comparison of disease over a segment of accumulated thermal tim
e revealed that in 1991, under average seasonal conditions, the earlie
st sowing experienced the most disease. In 1992, above average late sp
ring rainfall occurred and time of sowing had little influence on dise
ase over the same segment of thermal time. We conclude that a cultivar
appropriate for early sowing on the south coast should exhibit increa
sing leaf production in response to early sowing. This can result in a
reduction of disease severity on the upper leaves through disease esc
ape.