Wheat (
Triticum aestivum
L.) is the major crop in terms of planted area and presents the largest distribution in the country
covering a wide range of climatic regions. This study assesses the changes of various agronomic traits of winter wheat
cultivars released in Chile between 1920 and 2000. A total of 117 winter accessions, representing 45 old and 72 modern
cultivars were tested in a humid Mediterranean-type climate, with irrigation, in 2003. Old cultivars were those released
before 1960 and modern ones were those released after 1960. Principal component (PC) analysis using 10 agronomic traits
clearly separate modern from old cultivars of winter wheat. Comparing modern cultivars with old ones, plant height have
been reduced by 25.6%, but others traits have increased, like harvest index (21.1%), number of grains per ear (42.6%),
sedimentation value (103%), and grain hardness (32.0%). The variation in plant height was negatively correlated with
harvest index (r = -0.30, p < 0.001). Grain yield, a trait not included in PC analysis, was highly correlated with the second
PC (r = 0.81, p < 0.0001). Significant (p < 0.01) correlations were found between the year of release of cultivars and
agronomic traits: plant height (r = -0.82), harvest index (r = 0.40), number of grain per ear (r = 0.69), sedimentation value
(r = 0.64), and kernel weight (r = -0.46). Those correlations were mostly a consequence of absence or presence of dwarfing
genes in the germplasm. Finally, the yield progress was calculated from yield data of yield trial with 15-25 cultivars and
advanced lines of winter wheat tested almost every year from 1965 to 2001, showed no increase in yield between 1965 and
1975, but an increment of 246 kg ha
-1 per year between 1976 and 1998, representing an annual increase of 2.6%.
