Two trials were conducted at the Mexican National Institute of Agricultural Research (INIFAP) experimental station, Yaqui Valley, Sonora, Mexico, to compare the yield and agronomic traits of 21 Norin 10-derived, high yielding bread wheats (Triticum aestivum L.) adapted in northwestern Mexico. The dwarfing gene composition of each cultivar was determined by test crossing and seedling responsiveness to gibberellic acid. There was no lodging during the 2 years of yield testing. Grain yield levels were appropriately high (mean 7.05 t/ha). Genotypes with Rht1 gave highest yields while the Rht1 + Rht2 group yielded 1.4 % lower and Rht2 3.8 % lower. Similarly, the Rht1 lines had the highest biomass yield, while the Rht1 group and the double-gene dwarfs yielded on the average 5.4 and 9.1 % lower, respectively. However, the double-gene dwarfs had the highest harvest index, while the Rht2 and Rht1 genotypes had 2.5 and 3.2 % lower harvest indexes, respectively. Regarding yield components, the Rht1 genotypes averaged 9.3 % more grains/m2 than the Rht2 and Rht1 + Rht2 groups. Rht1 lines also produced 4.6 and 11.7 % more grains/spike as compared to Rht2 group and the double-gene dwarfs, respectively. However, Rht1+Rht2 and Rht1 genotypes had 37.4 and 22.3 more spikes/m2 than the Rht2 materials. The 1000-grain weight was heaviest in the Rht1+Rht2 group followed by the Rht2 and the Rht1 groups. The Rht2 lines had 0.5-cm longer spikes than the Rht1 lines. Phenotypic correlations calculated based on height gene classification showed a strong negative plant height-grain yield relationship in the single-gene dwarfs. Grain yield's relationship to biomass, grains/m2 and rate of biomass production were all positive and significant.
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