A method to identify early-stage transgenic Medicago truncatula with improved physiological response to water deficit

摘要

Phenotypic screening after transformation experiments aiming to identify lines with the enhanced/desired trait is still a time consuming process for most agricultural crops, especially when dealing with complex physiological responses such as water deficit. In this study we evaluated the suitability of non-destructive leaf gas-exchange analysis and imaging-PAM chlorophyll a fluorescence to select transgenic lines of Medicago truncatula expressing the Trehalose-6-Phosphate Synthase 1 (AtTPS1) from Arabidopsis thaliana with altered response to water deficit (WD) and WD recovery (WDR) in the early stages of the transformation process (T-0). Primary transformants (T-0) with different expression levels of a constitutive AtTPS1 construct were used. Additionally, we evaluated if the expression of the transgene could be correlated with the phenotype assessed. Among tested techniques and parameters measured, the net carbon assimilation (A) from gas-exchange analysis was the best parameter to early detect lines with WD and WDR improved performance, at the earliest stages of the transformation process. With this multidisciplinary approach, we selected 3 transgenic lines TPS7, TPS10 and TPS16 for further studies, which have higher or intermediate expression levels of the transgene and improved response to WD and WDR. This work will contribute to speed-up the identification of elite lines with confidence within a large number of individuals, thus reducing time, cost and labor associated with this plant improvement strategy.