Evaluating Leaf Wax and Bulk Leaf Carbon Isotope Surrogates for Water Use Efficiency and Grain Yield in Winter Wheat
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Crop Science Society of America. Bulk leaf carbon isotopic composition ( 13 C bulk ) has been widely used to investigate leaf level water use efficiency (WUE l ) in efforts to boost grain yield relative to crop water use. Although widely used for isotopic analyses, the bulk leaf represents a complex mixture of compounds. Single-compound isotopic analyses carry diagnostic advantages over bulk analyses in a range of applications and may also serve as surrogates for WUE l and grain yield in crops. This study tests whether compound-specific carbon and hydrogen isotopes of leaf wax n-alkanes ( 13 C alk and D alk ) and n-alcohols ( 13 C alc ) could be used as surrogates for WUE l and grain yield using conventional 13 C bulk as a reference. Ten winter wheat (Triticum aestivum L.) cultivars were planted under two irrigation treatments (full and deficit irrigation) at Uvalde (wet location) and Amarillo (dry location), TX, during two growing seasons. There were significant relationships between 13 C alk or D alk and 13 C bulk , indicating they can all serve as surrogates for WUE l in most cases. Compared with 13 C bulk , we found stronger relationships between 13 C alk at Uvalde or D alk under deficit irrigation at Amarillo and grain yield. The 13 C alk also had higher broad-sense heritability than 13 C bulk , indicating larger cultivar effects in 13 C alk than in 13 C bulk . In contrast, the 13 C alc was not consistently related with 13 C bulk or grain yield. Our study introduces the idea that 13 C alk and D alk may supplement conventional 13 C bulk with potential to assist in the breeding process when selecting for high-WUE and high-yielding cultivars.
