Field phenotyping of plant roots by electrical capacitance - a standardized methodological protocol for application in plant breeding: a Review

Due to the absence of a suitable method and standardized procedures, the root systems of plants have been evaluated to a much lesser extent than aboveground organs. The aim of this article is (i) to provide a detailed description and thus standardization of an upgraded procedure of electrical capacitance measurement for evaluating the size of the root system of plants in situ, which allows for a reassessment to be made during the growing season and subsequent harvest of seeds for the planting of selected progenies, (ii) to demonstrate, through a standardized methodological protocol, the applicability of root electrical capacitance measurement as a field phenotyping method for the selection of superior root systems to improve crop abiotic stress tolerance and resource efficiency, (iii) to suggest a standardized methodological protocol for the application of electrical capacitance measurements in breeding nurseries, and (iv) to discuss the methodological aspects, development and limitations of this method. A methodological overview of the use of electrical capacitance to measure plant root systems, which emerged from working groups directed by the author of this unique method, is presented along with a standardized protocol. An overview of the application of electrical capacitance measurements of roots in breeding is shown along with some examples of successful applications