RESISTANCE OF EARLY-MATURING EUROPEAN MAIZE INBRED LINES TO SETOSPHAERIA-TURCICA

Breeders lack information on the resistance of European maize to Setos phaeria turcica, the incitant of northern corn leaf blight (NCLB). To assess the variation present in current breeding material and to ident ify new sources of resistance, we tested 133 early-maturing (< FAO 300 ) maize inbred lines (54 flint, 64 dent, and 15 interpool lines) from Germany. France, and Switzerland for their resistance to S. turcica in a disease-prone environment (Cadenazzo, Switzerland) in 1993 and 1994 . NCLB was rated three times (1-9 scale), and the area under the disea se progress curve (AUDPC) was calculated. Differentiation of the mater ial was best at 1-2 weeks after flowering (score 2), Infection was sev ere in 1993 and moderate in 1994 with score-2 means of 6.0 and 3.2, re spectively The average level of resistance was intermediate (overall s core-2 mean 4.6) and the range was wide (1.5 to 7.8). Genetic variatio n for NCLB resistance was significant both in the flint and dent heter otic pools. Several flint and a few dent lines possessed a high level of quantitative resistance, as was confirmed in a greenhouse trial. Wh ile the medians of score 2 and AUDPC were nor different (P<0.05) betwe en the two pools, the genetic variance component for either resistance trait was significantly higher in the flint than in the dent pool (P < 0.01). In either pool, genotype a year interaction was negligible fo r score 2 and moderate but significant for AUDPC. Heritability estimat es were high for score 2 ((h) over cap(2) greater than or equal to 0.7 3) and AUDPC ((h) over cap(2) greater than or equal to 0.73). Resistan ce was only weakly correlated with maturity (days to silking). There w as no significant correlation ((r) over cap(p) = 0.07) between NCLB an d European corn borer (Ostrinia nubilalis) resistance which had been a ssessed in a previous study with the same set of inbred lines. In conc lusion. prospects for effective NCLB resistance breeding in early-matu ring European maize are good.