A rapid method for identifying ploidy level in Isatis indigotica Fortune and Isatis tinctoria Linnaeus

The genus Isatis is widely distributed throughout the world. In this work, thirty-two Isatis indigotica Fortune germplasms, collected from different regions and geographical locations in China, were analyzed the ploidy levels by flow cytometry. I. indigotica Fort. and Isatis tinctoria Linnaeus distinguished with root tip chromosome compression staining and cell flow cytometry. Microscopic observation showed that the chromosome numbers of I. indigotica Fort. and I. tinctoria L. were 2n = 14 and 2n = 28, respectively. In order to establish a flow cytometric nuclear experiment system suitable for I. indigotica Fort., the leaves of I. indigotica Fort. were used to prepare nuclear suspension with LB01, OTTO, Tris·MgCl2, patent of Luochang and Galbraith extraction buffer. It was found that the histogram generated by LB01, OTTO, Tris·MgCl2 and Patent of Luochang dissociation solution has poor peak shapes and large CV values, and Galbraith dissociation solution extraction buffer was suitable for extracting nuclei from most germplasms. Flow cytometry proved to be a simple, rapid, and highly accurate method for identifying ploidy levels Isatis species.