Assessment of somaclonal variation during sugarcane micropropagation in temporary immersion bioreactors by intersimple sequence repeat (ISSR) markers

Somaclonal variation refers to the genetic and epigenetic changes in plants regenerated from plant tissue culture. In this study, using intersimple sequence repeat (ISSR) molecular markers, the somaclonal variation during micropropagation of sugarcane using temporary immersion bioreactors (TIBs) was evaluated. Apices of the cultivar Mex 69-290 were established and multiplied by ten subcultures in TIBs. After 30 d in each subculture, the number and length of shoots per explant were recorded. For the molecular analysis, ten plants were taken per subculture, and a total of 109 bands from ten ISSR primers were obtained. For each subculture, the polymorphism (%) was calculated. A dendrogram of genetic distances between subcultures and the donor plant was obtained using a matrix of Nei's genetic distances and the unweighted pair group method with arithmetic mean (UPGMA). The results showed that the production of sugarcane shoots tends to increase until subculture 8, while shoot length decreases. ISSR markers showed the existence of somaclonal variation during micropropagation of sugarcane. The subcultures with the highest percentage of polymorphism (%) and genetic distances (GD) were the 1A degrees, 9A degrees, and 10A degrees (with 10.1, 15.6, and 10.1% and 0.0222, 0.0181, and 0.0181 GD, respectively). The molecular and statistical analysis showed that in vitro establishment and the number of subcultures are both factors that affected the frequency of somaclonal variation during the micropropagation of sugarcane using TIBs. Thus, it is important to determine the optimal number of subcultures that can be made from an explant for each species to be micropropagated.