Use of temporary immersion bioreactors and solid culture medium in the in vitro propagation of pear rootstocks

Micropropagation through the use of temporary immersion bioreactors systems is considered an alternative to increase the efficiency of production of explants in vitro, reducing costs by automating the process. The objective of this study was to compare different techniques of micropropagation of pear tree rootstocks. The experiment was carried out at the plant biofactory of the Santa Catarina State University (UDESC/CAV). Four rootstocks of pear tree were studied: OH×F69; OH×F87; OH×F97 and Pyrodwarf (PDW); and two cropping techniques: temporary immersion systems (TIS) and conventional micropropagation system (solid culture medium), comprising completely randomized design in a factorial scheme 4×2 totalling eight treatments. The explants were cultured for 40 days in Quoirin & Lepoivre (QL) medium, supplemented with 1 mg L^‑1 of benzyl aminopurine (BAP) in both techniques. It was verified that there was statistical difference between the TIS and the solid culture medium for the variable number of shoots among the rootstocks, with OH×F69 being higher in the solid medium (20 shoots) and OH×F87 being higher in TIS (76 shoots). For the variables mean length and greater length of greater bud, rootstocks OH×F69 and PDW differed statistically, being higher in TIS, and OH×F97 was superior in TIS only for the variable length of greater bud. For the number of leaves, there was a statistical difference between the materials in the solid medium, and the best results were obtained in the rootstocks OH×F69, OH×F87 and OH×F97 with values of 136.67, 125.67 and 100.33, respectively. Differences were also observed between the techniques for leaf number, with TIS being superior in the OH×F97 rootstock and the use of the solid culture medium gave better results for the rootstock OH×F69. In general, TIS is recommended for the in vitro propagation of most of the pear tree rootstocks studied.