Physiological basis of yield gains in wheat associated with the LR19 translocation from Agropyron elongatum

Abstract

The physiological and genetic basis of yield improvement in wheat isonly partially understood. Nonetheless, a significant increase in yield andbiomass has been observed in several backgrounds when alien chromatinassociated with Lr19 was introgressed from Agropyronelongatum. Theoretically, higher yield and biomass may be achievedthrough (i) greater interception of incident radiation, (ii) increasedradiation use efficiency, (iii) a more optimal source-sink balance permittinghigher sink demand and/or a higher partitioning of assimilates to yield. Theobjectives of the current study were to evaluate the performance of nearisogenic lines differing in Lr19 to observe the physiological basis ofsuperior performance. Lr19 was associated with increases in yield(average 13%), final biomass (10%) and grain number (15%) in allbackgrounds studied. Differences were not associated with improved lightinterception based on measurements of biomass shortly after canopyclosure, nor with improved radiation use efficiency (RUE) prior to grainfilling based on biomass accumulation rate and direct measurement offlag-leaf photosynthetic rate prior to anthesis. Lr19 was associatedwith an increased partitioning of biomass to spike growth at anthesis(13%), a higher grain number per spike, and higher RUE and flag-leafphotosynthetic rate during grain filling. The mechanism causing increasedpartitioning of assimilates to spikes relative to the rest of the plant in Lr19 isolines was apparently not related to phenology or assimilationcapacity.