Micropropagation Technology in Early Phases of Commercial Seed Potato Production

Research was carried out on possibilities to improve methods commonly used in commercial potato tissue culture laboratories, predominantly those in Western Canada. The study included: (1) Photoautotrophic micropropagation, (2) Short-term, low temperature (< 12 weeks) storage of plantlets, (3) Production of microtubers (in vitro tubers) and (4) Utilization of microtubers in greenhouse production of minitubers and Pre-elite tubers in the field. Effects of jasmonic acid (JA) and photoperiod on in vitro tuberization were also tested. Performance of microtubers in production of nuclear (greenhouse) Pre-elite tubers was compared with the industry standard, in vitro plantlets. Six commercial cultivars, ‘Amisk’, ‘Atlantic’, ‘Russet Burbank’, ‘Sangre’, ‘Shepody’ and ‘Umatilla Russet’, were used in the studies. Potato plantlets produced photoautotrophically were either of the same quality or better than conventional cultures. The conventional cultures benefited from CO2 enrichment, over a 4 week period, by a 20% increase in number of nodes and a 50% increase in stem dry weight. Cultures stored for up to 12 weeks in a cold room (4C) on media containing 30 gL sucrose under continuous, low red light (690 nm) at 3 μmolms PPFD maintained high quality, vigor and re-growth capacity. Significantly better production of microtubers (more tubers and weight) was observed on solid agar than on liquid media, under the 8 h photoperiod (SD) compared to no light. Microtubers produced under SD performed better in the field or in the greenhouse than microtubers produced in dark. In most studies, JA conditioned plantlets produced more uniform and larger microtubers, especially under short days conditions (8 h light). Production of microtubers in all three russet varieties tested was superior to that of Shepody and Atlantic. Results with pretreatment of JA in the field production of Pre-elite tubers were inconclusive. Microtubers of russet varieties performed the best and can be recommended for greenhouse production of minitubers but not for direct use in the field. INTRODUCTION In potato, micropropagation became an essential component of seed production systems, providing large numbers of pathogen-free plants in early phases of multiplication. Tissue cultured plantlets are the most common type of propagule used in the seed potato system around the world. Microtubers or in vitro produced tubers are another type of propagule that could also be utilized in the production of pathogen-free seed potato material. Microtubers are small (0.02-0.7 g) tubers produced from nodal cuttings or on complete plantlets using a specific growing medium (Hussey and Stacey, 1984; Estrada et al., 1986; Lillo, 1989; Struik and Lommen, 1990). Despite their advantage over in vitro plantlets in storage and germplasm exchange (Estrada et al., 1986), microtubers have not been accepted as propagules of choice by the industry (Lommen, 1995; Struik and Wiersema, 1999). Recently, several new production protocols have been developed (Struik and Wiersema, 1999). Most of them, however, require either special equipment or frequent media exchanges which increase cost and labour demand and may lead to culture infection (Ranalli, 1997; Struik and Wiersema, 1999). The Proc. XXVI IHC – Potatoes Healthy Food for Humanity