Cc. Mundt et al., CHOOSING CROP CULTIVARS AND CULTIVAR MIXTURES UNDER LOW VERSUS HIGH DISEASE PRESSURE - A CASE-STUDY WITH WHEAT, Crop protection, 14(6), 1995, pp. 509-515
Four winter wheat cultivars and all possible equiproportional mixtures
among them were grown under low and high severity of Septoria blotch
(caused by Mycosphaerella graminicola and Leptosphaeria nodorum) and e
yespot (caused by Pseudocercosporella herpotrichoides) in each of 3 ye
ars. On average, mixtures provided only a small reduction of Septoria
blotch relative to their component pure stands (27, 9, 15% for the thr
ee seasons), however, mixtures containing both very resistant and very
susceptible cultivars demonstrated larger reductions. Reductions of e
yespot severity due to mixing averaged only 6% in the one mixture eval
uated, and were statistically non-significant. The two most resistant
cultivars yielded less than the two more susceptible cultivars under l
ow disease pressure, while the opposite relationship between yield and
disease resistance was found under high disease pressure. There was c
onsiderable variation among mixtures for yield, and the yield of a mix
ture could generally not be predicted a priori. Some mixtures demonstr
ated high yields over years and under both low and high disease pressu
re. For western Oregon and Washington, the best strategy may be to cho
ose a cultivar with intermediate yield potential and disease resistanc
e or to grow a cultivar mixture with proven yield performance.