Effect of Lr34 resistance on leaf rust development, grain yield and baking quality in wheat.

The protection provided by the leaf rust resistance gene Lr34 against Puccinia recondita f. sp. tritici was studied in the field over two seasons. In leaf-rust inoculated and fungicide-sprayed control plots, yield of RL6058, the ‘Thatcher’ backcross line with Lr34, was compared to that of the susceptible cultivar ‘Thatcher’. Leaf rust severity remained low on RL6058 in both seasons, but was high on ‘Thatcher’. The latent period of wheat leaf rust isolate 3SA132 in flag leaves of RL6058 was 256 h longer than in ‘Thatcher’. The uredinium density on ‘Thatcher’ was 14.4/cm2, compared to 3.7/cm2 flag leaf surface on RL6058. Leaf rust infection of ‘Thatcher’ reduced the total grain yield per plot by 25.4% and 1,000 kernel mass by 15.6%. Leaf rust caused little or no damage on RL6058 and rusted plots outyielded the control plots by 0.3 %. Seed weight of RL6058 was reduced by 0.7%. Compared to previous greenhouse studies, the adult-plant resistance conferred by Lr34 is more clearly expressed in the field. Evaluation of milling and baking quality characteristics revealed that compared to ‘Thatcher’, RL6058 had a higher flour protein content, but that its milling, dough development and baking properties were inferior.

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