Physiological performance of synthetic hexaploid wheat-derived populations

Wild ancestors of common wheat (Triticum aestivum L.) have been reported to have higher maximum photosynthetic rates than modern wheat cultivars. Synthetic hexaploids, obtained by crossing tetraploid wheat and Aegilops tauschii Coss., have proven useful as a source of resistance or tolerance to biotic and abiotic stresses. This study was conducted to determine whether synthetic hexaploids also could contribute genetic diversity to enhance leaf photosynthetic rate and other physiological traits. Three different populations of BC2F2:6 synthetic-derived lines were evaluated at the Agricultural Research Center for the Northwest (INIFAP) Experimental Station, near Ciudad Obregon, Sonora, Mexico. Differences in maximum photosynthetic rate were detected among genotypes. Several synthetic-derived lines showed higher photosynthetic rates than their recurrent parent. Staygreen, determined as days between senescence and physiological maturity, of most synthetic-derived lines did not differ from the recurrent parents. Maximum photosynthetic rate was negatively associated with leaf area and positively associated with stomatal and mesophyll conductances, and leaf temperature depression. Mesophyll conductance accounted for 85% of the variation in maximum photosynthetic rate. These results suggest that synthetic-derived wheat can be also a source of genetic diversity for important physiological traits such as enhanced photosynthetic rate.