Rapid Differentiation of Closely Related Citrus Genotypes by Fluorescence Spectroscopy

The differentiation of closely related Citrus genotypes is a meticulous, laborious, and time-consuming task that involves the assessment of complex traits such as growth, tolerance to stress, photosynthetic efficiency, yield, and many others. Such a task is generally accomplished either by analyzing specific features of adult plants or by applying molecular markers to young trees. On one hand, only after plants start yielding can distinct genotypes be differentiated by comparing their fruit sizes, shapes, taste, and the number of seeds. On the other hand, molecular markers are expensive, and demand expertise and time for the analysis of a larger number of plants. For these reasons, the development of techniques that could assist in an early, quick and accurate differen-tiation of closely related Citrus varieties is of utmost importance. In this context, laser-induced fluorescence spectroscopy (LIFS) is a promising technique, since it is rapid, highly sensitive, and inexpensive. Previous studies showed that LIFS can differentiate a variety of sweet orange. However, this new study aimed to determine LIFS accuracy in the differentiation and grouping of very closely varieties of four Sunki mandarin selections: Comum, Florida, Tropical, and Maravilha. Furthermore we compared the results with ISSR and SSR molecular markers for the same varieties. LIFS technique distinguished the four selections with accuracy greater than 70%. Only with molecular markers was possible distinguishing clearly Tropical from Maravilha, but not Comum from Florida selections. In this way the results suggest that LIFS may be a sound tool for helping the identification of closely Citrus varieties.