Photoperiod Improves Long-term Survival of In Vitro-stored Strawberry Plantlets

Abstract

<jats:p>Cold storage is important for managing in vitro germplasm collections. Strawberry shoot cultures can typically be held at 4 °C for 9 to 24 months before they require repropagation. Concentration of BA in the storage medium, pre-storage cold acclimatization (CA), and exposure to a photoperiod during storage were studied to determine conditions for improved strawberry culture storage. <jats:italic>Fragaria</jats:italic> shoot cultures stored at 4 °C were rated for plantlet condition on a 0-5 scale at 9, 12, and 19 months. Four species were CA and stored on medium with 0, 1, 2.5, or 5 μ<jats:sc>m</jats:sc> BA either in darkness or under a 12-hour photoperiod. Mean ratings over all treatments and genotypes were best at 9 and 12 months (3.4) and declined at 19 months (2.2). BA in the storage medium significantly improved ratings for two species at 9 and 12 months, but ratings were not significantly different at 19 months. At 19 months of storage, shoot cultures stored with a photoperiod were rated significantly better (<jats:italic>P</jats:italic> ≤ 0.05) than those grown in darkness. Five <jats:italic>Fragaria</jats:italic> genotypes stored on medium without BA were used to study the effect of photoperiod and CA on ratings of stored plantlets. CA-shoot cultures stored for 9 or 12 months were rated significantly better than non-CA cultures. After 12 and 19 months storage, three of the five genotypes stored under a 12-hour photoperiod had significantly higher ratings than those stored in the dark (<jats:italic>P</jats:italic> ≤ 0.01), but by 19 months CA was nonsignificant. Overall, the addition of a photoperiod improved the condition of <jats:italic>Fragaria</jats:italic> shoot cultures stored at 4 °C. Chemical name used: <jats:italic>N</jats:italic><jats:sup>6</jats:sup>-benzyladenine (BA).</jats:p>

Efficient Technique for Long-Term &lt;i&gt;in Vitro&lt;/i&gt; Storage of Transgenic Aspen Genotypes

“…. Noteworthy is that earlier methods of long-term storage mostly modified the composition of culture medium[4] [9][19] [23]. Yet, according to our findings, changing the culture medium composition alone is not enough for aspen plants.…”

In Vitro Storage of Hop (Humulus L.) Germplasm

“…Storage followed the technique developed for other genera but with NCGR-HUM medium (Reed, 1999(Reed, , 2002Reed et al, 1998). Plantlets (2 to 3 cm height) were transferred to two 5-chambered semi-permeable tissue-culture bags (Star-pak, Garner Enterprises, Willis, Tex) with 10 ml medium per chamber 3 wk after the last regular subculture.…”

“…Ratings were: 5, dark green leaves and stems, no etiolation, base green; 4, green leaves and stems, little etiolation; 3, shoot tips and upper leaves green, etiolation present, base green; 2, shoot tip green, leaves and stems mostly brown, base may be brown; 1, plantlet mostly brown, only extreme shoot tip green, much of base dark brown; 0, all of plantlet brown, no visible green on shoot tip. Plantlets were removed for repropagation when ratings reached ≤ 2 and the length of storage was noted (Reed, 1999(Reed, , 2002Reed et al, 1998). One storage period was studied for 70 accessions and the 10 plantlets of each accession were treated as a group.…”

“…Long-storing plants remained at the "3" rating level (shoot tips and upper leaves green, etiolation present, base green) for longer periods than the average plant. This technique was originally optimized for Fragaria (18 months ± 6), and was then applied to Rubus (27 months ± 14), and Pyrus (32 months ± 12) (Reed, 1999(Reed, , 2002Reed et al, 1998). Variation also may occur between storage cycles due to many factors.…”

“…It is likely that additional improvements can be made to increase the length of storage for individual Humulus accessions, but for the majority the technique is directly applicable. When optimizing a medium-term in-vitro storage system the age, size and physiology of the plants must be considered as well as temperature of storage, cold acclimation, roots, single or multiple shoots, light intensity and quality and storage medium (Ashmore, 1997;Moriguchi and Yamaki, 1989;Reed, 1999;2002;Reed and Chang, 1997;Reed et al, 1998). Individual factors require long periods of study to fully optimize storage for a genus; however, the standard technique can be used quickly and with generally good results almost immediately following the decision to store a new type of plant.…”