In vitro induction of potato tuberization by organic acids

Abstract

SummaryPotato microtubers are usually induced in media containing growth regulators, typically cytokinins and growth retardants. However, since these substances may imbalance the physiology of the cultured explants and cause adverse carry-over effects on the subsequent performance of the microtubers, the potential acid-induction of in vitro-mass tuberization was investigated as an alternative. For this purpose, a range of explant types (stolons, single-node or apex-containing multinodal sections), organic acids (acetic, propionic, ascorbic, acetylsalicylic or salicylic acid), and photoperiods (continuous dark, 8 or 16 h photoperiod) were established. Gellified medium or raft membranes on liquid medium were also tested.Although variations due to explant type, photoperiod, organic acid supplemented, and medium type were found, all organic acids tested under the different experiments caused tuberization. Multiple tuber formation or bigger tubers did not develop on multinodal explants. In terms of tuberization rate and mean tuber weight, gellified medium performed better than liquid medium with rafts. The recently established role of the salicylic and acetylsalicylic acids on tuberization is corroborated by our system. The results with the acetic, propionic and ascorbic acids show that in vitro hormone-free tuberization can be easily and rapidly achieved.

Carboxylic acids affect induction, development and quality of potato (Solanum tuberosum L.) microtubers grown in vitro from single-node explants

“…In comparison to 8% sucrose or formic acid-containing 8% sucrose media, acetic and propionic acids at 6.0 mM induced the smallest microtubers per single-node explant. Our observations are in contradiction to earlier reported roles of carboxylic acids (acetic and propionic acids) in potato microtuberization (Pelacho et al 1999). Using both stolons and single-node explants, the authors detected an enhancement in microtuberization rate as well as microtuber size with acetic (3.0 mM) and propionic (6.0 mM) acids as compared to that with 6% sucrose medium.…”

“…Moreover, the final size of the microtubers grown in medium containing 8% sucrose is larger than of those grown in 4 or 6% sucrose medium (Claassens and Vreugdenhil 2000). Therefore, it is not at all unexpected as to why Pelacho et al (1999) obtained a reduced microtuberization rate or microtuber number per explant in 6% sucrose medium compared to that in acetic/ propionic acid-containing 6% sucrose medium vis-a`-vis a stimulatory effect of carboxylic acids on microtuberization in their experiment. It is well established that the growth retardants, which usually suppress gibberellin synthesis, may act to stimulate microtuberization only under weakly inductive conditions such as in the absence of optimum sucrose concentration or under long days (Stecco and Tizio 1982;Vecchio et al 1994) and on a genotypic-specific basis (Donnelly et al 2003).…”

“…These authors have further shown the superiority of carboxylic acids for microtuber induction over salicylic, acetylsalicylic or ascorbic acid. However, they tested the carboxylic acids at single concentration in combination with 6% sucrose (Pelacho et al 1999), although it is well established that 8% sucrose is the optimum for microtuberization (Harmey et al 1966;Wang and Hu 1982;Koda and Okazawa 1983;Tovar et al 1985;Estrada et al 1986;Garner and Blake 1989;Khuri and Moorby 1995;Sarkar and Naik 1998;Vreugdenhil et al 1998;Xu et al 1998). Since microtuber responses mainly depend upon exogenous sucrose concentration (Garner and Blake 1989;Khuri and Moorby 1995;Xu et al 1998;Donnelly et al 2003), the results reported by Pelacho et al (1999) appear to be inconclusive.…”

“…Organic acids such as salicylic and acetylsalicylic acids have been shown to induce in vitro tuberization (Koda et al 1992;Lopez-Delgado and Scott 1997). In this context, of particular interest is the reported promoting effects of carboxylic acids like acetic and propionic acids on microtuberization (Pelacho et al 1999). These authors have further shown the superiority of carboxylic acids for microtuber induction over salicylic, acetylsalicylic or ascorbic acid.…”

The effects of explant rotation, medium types, JA and GA3 additions on in vitro microtuber production from potato (Solanum tuberosum L.)

“…In another study [50], the development of microtubers in liquid and solid media were compared, and it was observed that cultures incubated in a liquid medium resulted in microtubers with more weight than those incubated in a solid medium. In a study conducted by Pelacho et al [51], however, it was found that a half-solid medium resulted in higher tuberization rates and higher tuber weight values than those obtained from liquid media. A reason for the good results, in regards to tuberization, obtained in our study when a two-phase (solid+liquid) medium was used, might be due to the molecules needed for tuberization found in the medium being able to adsorb more readily on to the plant.…”