Abstract
Improving drought tolerance of crops has become crucial due to the current scenario of rapid climate change. In particular, development of new maize germplasm with increased drought tolerance is viewed as a major breeding goal to ensure sustainable food and feed production. Therefore, accurate rapid phenotyping techniques for selection of superior maize genotypes are required. The objectives of this study were to determine whether Raman microscopy technique can be applied for accurate assessment of drought-tolerance levels in both genetically diverse and near-isogenic maize lines that differ in their levels of drought-tolerance. Carotenoid degradation is known to be a direct stress response initiated by reactive oxygen species during osmotic stress such as drought. Using Raman mapping, we observed real-time changes in the rate of carotenoid degradation in chloroplasts that was dependent on the strength of osmotic stress. In addition, we showed that the rate of carotenoid degradation as measured by Raman spectroscopy correlates directly with drought tolerance levels of diverse maize genotypes. We conclude that Raman technique is a robust, biochemically selective and non-invasive phenotyping technique that accurately distinguishes drought tolerance levels in both genetically diverse and near-isogenic maize genotypes. We conclude that this technique can be further developed to render it suitable for field-based early assessment of breeding materials with superior drought-tolerance traits.
Highlights
Due to rapidly increasing human population, there is a crucial need to meet global food security needs and satisfy the increasing demand for food, feed, and fuel
Since the major objective of this study was to determine whether Raman spectroscopy can be utilized to distinguish maize genotypes that display diverse levels of drought tolerance, we first aimed to establish whether carotenoid degradation is proportional to the levels of osmotic stress that leaf tissue experiences by using different concentrations of mannitol treatments of leaf disks
To understand the subcellular origin of carotenoids being degraded under osmotic stress, we compared the responses of leaf disks from the chlorophyll-less plants that grew under complete darkness that had few if any mature chloroplasts to those that contain normal levels of fully mature chloroplasts
Summary
Due to rapidly increasing human population, there is a crucial need to meet global food security needs and satisfy the increasing demand for food, feed, and fuel. It is necessary to provide improved plant phenotyping techniques to breeding programs to aid in the development of germplasm of crops that have increased drought tolerance levels, and can help adapt to future. Improving drought tolerance of crops has become one of the significant challenges in global agricultural production and food security (Tilman et al, 2001; Chaves et al, 2003; De La Fuente et al, 2014). A major objective in most breeding programs is to develop superior germplasm that tolerate water stress yet produce a higher yield. This is achieved by employing vastly improved breeding strategies through years of genetic research, including marker assisted selection and hybrid seed production (Fiorani and Schurr, 2013). Genotypes that correlate with improved yield or other agronomic traits must be considered in the contexts of various environments to determine optimum phenotypic responses (Fiorani and Schurr, 2013)
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