Identification of QTLs associated with limited leaf hydraulic conductance in soybean

Soybean (Glycine max (L.) Merr.) genotype PI 416937 has been identified as expressing a 'slow-wilting' phenotype in the field and this has been traced to a low hydraulic conductance in its leaves. The transpiration rate of de-rooted shoots of this genotype has been found to be insensitive to the aquaporin inhibitor silver nitrate compared to elite cultivars which are silver nitrate sensitive. These results indicated that PI 416937 might have a unique aquaporin population. The objective of this study was to determine if QTLs could be identified that are associated with the lack of sensitivity in PI 416937 to silver. To identify the genomic locations and genetic bases of this trait, a recombinant inbred line population was derived from a mating between PI 416937 and the cultivar 'Benning'. The RILs were all phenotyped for their response to the silver inhibitor and the results were subjected to a QTL analysis. Four QTL were identified as putatively associated with the silver response (qSV). These QTL explained from 17.7 to 24.7% of the phenotypic variation with qSV_Gm12 explaining the greatest amount of phenotypic variation. The qSV_Gm03 and qSV_Gm10 QTL inherited their positive alleles from PI 416937, while qSV_Gm05 and qSV_Gm12 inherited their favorable alleles from Benning. Co-localized silver nitrate response QTL with other morpho-physiological traits could help to explain soybean plant's ability to tolerate water-deficit stress.