Use of jasmonate for conditioning of potato plantlets and microtubers in greenhouse production of minitubers

American Journal of Potato Research,  May/Jun 2003  by Pruski, K,  Astatkie, T,  Duplessis, P,  Lewis, T,  Et al

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Accepted for publication 19 February 2003.

ABSTRACT

A two-year study was conducted to determine the effects of (1) jasmonic acid (JA) pre-treatment, (2) JA supplement in culture media, (3) cultivar (Amisk, Atlantic, Russet Burbank, Shepody, and Umatilla Russet), (4) light (0 h, 8 h), and (5) dormancy breaking treatment (Rindite, gibberellic acid) on greenhouse production of minitubers from microtubers and in vitro plantlets. The microtubers were produced under short day (8 h) light conditions and in darkness, from stock plantlets pre-treated with JA and untreated, and on tuberization media with or without JA. In vitro plantlets (the industry choice in nuclear seed potato production) of all five cultivars performed well, meeting the standard criteria for greenhouse production of minitubers. Production of minitubers from microtuber-derived plants of cvs Amisk, Russet Burbank, and Umatilla Russet was similar to that of plantlet-derived plants with regard to number of minitubers. Yields (weight), however, were lower than those from plantlets. Microtuber responses to JA varied with cultivar. Amisk produced the highest number of minitubers per plot from microtubers derived from JA pre-treated plantlets. Jasmonic acid-pretreated microtubers also gave significantly more minitubers in Russet Burbank and Umatilla Russet than the microtubers from other treatments. Shepody did not benefit from JA treatments and JA pre-treated Atlantic microtubers performed poorly, producing significantly lower yields of minitubers than other cultivars. Independently of cultivar, microtubers produced under 8-h photoperiod gave significantly higher yields of minitubers than microtubers produced in the dark. Dormancy release was the key factor influencing microtuber performance. Rindite proved to be a much more effective dormancy breaking treatment than gibberellin. JA conditioning of stock plants prior to tuberization is being proposed as a treatment in production of microtubers for greenhouse production of minitubers.

ADDITIONAL KEY WORDS: Gibberellic acid, in vitro tuberization, jasmonic acid, microtubers, minitubers, Rindite, Solanum tuberosum L.

INTRODUCTION

In vitro plantlets are commonly used for speeding up multiplication of disease-free plant material in elite seed potato programs, including greenhouse production of seed tubers, minitubers (also called nuclear tubers), and in vitro production of microtubers (Jones 1988; Lommen 1995; Struik and Wiersema 1999). Although minitubers became the primary choice of nuclear propagules by seed potato growers, several researchers believe that microtubers also have a good potential to be integrated into the seed programs (Lillo 1989; Struik and Lommen 1990; Lommen 1995; Khuri and Moorby 1996; Nasiruddin and Blake 1997; Kim et al. 1999; Struik and Wiersema 1999). Microtubers are considered an alternative to plantlets in germplasm storage and exchange (Estrada et al. 1986), but their use in the production of minitubers in greenhouses and/or pre-elite tubers in the field is still controversial (Ranalli et al. 1994; Ranalli 1997; Coleman et al. 2001) and not adopted by the industry. Most of the commercial production of minitubers is still based on tissue culture plantlets. Limited information on the production of microtubers at commercial scale, suitability of cultivars to specific microtuberization methods, and on their greenhouse and field performance comparisons to plantlets (Joung et al. 1993; Le 1999; Dobranszki et al. 1999) is probably the most critical drawback. Both propagules, plantlets and microtubers, have the same disadvantage in that they require special attention after planting. Moreover, the microtubers vary in size, the length of their dormancy period, and their physiological age (Leclerc et al. 1995; Tabori et al. 1999; Coleman and Coleman 2000). Consequently, not all microtubers uniformly sprout and produce vigorous plants after planting. Adaptation of some newly developed methodologies to mass production of microtubers, i.e., in bioreactors (Yu et al. 2000), may prove that microtubers can be accepted as an alternative to plantlets.

Over the last decade several researchers observed that jasmonic acid (JA), a growth regulator produced by plants exposed to stress (Biondi et al. 2000), is highly effective in the induction of microtubers (Koda et al. 1991; Van den Berg and Ewing 1991; Pelacho and Mingo-Castel 1991; Ravnikar et al. 1992; Pruski et al. 1993; Kreft et al. 1997). In a recent study (Pruski et al. 2002), we found that JA supplement at less than 5 [mu]M in the plantlet multiplication medium generated plantlets with sturdier stems, better developed root systems, and higher root/shoot biomass ratios compared to plantlets grown on conventional media. Nodal explants taken from JA conditioned plantlets also tuberized earlier and more uniformly, giving higher yield of microtubers than controls. A similar stimulation of tuberization was achieved when JA was supplemented directly into the microtuberization media.