Effects of different culture media and conditions on biomass production of hairy root cultures in six Mexican cactus species

Abstract

To establish cactus hairy root lines, axenically grown Escobaria chaffeyi, Ferocactus peninsulae, Mammillaria bocasana subsp. bocasana, Turbinicarpus lophophoroides, Turbinicarpus pseudopectinatus, and Turbinicarpus schmiedickeanus subsp. schwarzii explants were inoculated with an Agrobacterium rhizogenes A4 agropine-type strain carrying the ESC4 plasmid, which contains the nptII and gus genes. Cactus hairy roots showed an active branching pattern and fast growth on hormone-free medium. Twelve different basal culture media were tested for biomass production of these six species. Our results showed that medium optimization needs to be performed for each individual species, as growth responses differed among taxa. Maximum hairy root growth was obtained on Driver and Kuniyuki Walnut (DKW) medium for E. chaffeyi and T. schmiedickeanus subsp. schwarzii (3-fold weight increase over starting weight in 30 d for both species). M. bocasana subsp. bocasana responded best when cultured on WPM medium, doubling the initial inoculum weight. F. peninsulae and T. lophophoroides showed a maximum biomass increase when cultured on N6 medium (0.5- and 2-fold increases over starting weight, respectively, in 30 d). T. pseudopectinatus generated callus tissue on all basal media except for Heller medium, on which hairy root weight increased 4-fold over the starting weight in 30 d. Culture medium was also found to affect hairy root morphology of all species tested. Scaling-up of the hairy root cultures was achieved by using the temporary immersion system RITA®.