Bert Vandenbussche

Cryopreservation of in vitro sugar beet shoot tips using the encapsulation-dehydration technique: influence of abscisic acid and cold acclimation

Abstract It has been previously shown that shoot tips of in vitro plantlets of sugar beet (Beta vulgaris L. clone SES1) can be cryopreserved using the encapsulation-dehydration technique (survival rate of 37% after freezing). This article reports the influence of abscisic acid (ABA) and cold acclimation on survival after cryopreservation. When ABA was added to the multiplication medium of the plants, the survival rate of shoot tips after cryopreservation was not increased (45%). After cold acclimation of the plants, their growth pattern differed (plants became apically dominant) and the survival rate of the shoot tips after cryopreservation clearly increased (70% survival and 50% plant regeneration after freezing). This improved protocol was successfully applied to three other clones.

Changes in sugar content and fatty acid composition of in vitro sugar beet shoots after cold acclimation: influence on survival after cryopreservation

To cryopreserve sugar beet shoot tips using an encapsulation-dehydration technique, cold hardening of in vitro plants was needed to obtain high survival rates after freezing. Cold acclimation not only enhanced dehydration and freezing tolerance, but also induced several changes in sugar beet shoots. Plants contained greater amounts of sucrose, D-glucose and D-fructose and the fatty acid composition of lipids changed. Furthermore, the unsaturation level of membrane lipids, estimated by the (C18:2 + C18:1)/C16:0 ratio, increased after cold hardening. These changes were correlated with better survival rates after cryopreservation.

Study of ethylene kinetics during and after germination of sugar beet (Beta vulgaris L.) seeds and fruits

The interaction between ethylene production and seed germination of sugar beet ( Beta vulgaris L.) was studied. For intact fruits, deoperculated fruits and true seeds, ethylene was only produced after the start of radicle emergence. Removal of the operculum or the whole pericarp, likely allowing better water uptake and gas exchange by the true seed, actually increased the time span between the start of radicle emergence and the beginning of ethylene production compared to intact fruits. ACC (1-aminocyclopropane-1-carboxylic acid), AOA (aminooxyacetic acid), AIB (2-amino isobutyric acid) and STS (silver thiosulphate) in the imbibition medium did not influence the germination pattern. Based on these findings, the function of ethylene during the germination of sugar beet is uncertain.

Ethylene is differentially regulated during sugar beet germination and affects early root growth in a dose-dependent manner

AbstractMain conclusionBy integrating molecular, biochemical, and physiological data, ethylene biosynthesis in sugar beet was shown to be differentially regulated, affecting root elongation in a concentration-dependent manner. There is a close relation between ethylene production and seedling growth of sugar beet (Beta vulgaris L.), yet the exact function of ethylene during this early developmental stage is still unclear. While ethylene is mostly considered to be a root growth inhibitor, we found that external 1-aminocyclopropane-1-carboxylic acid (ACC) regulates root growth in sugar beet in a concentration-dependent manner: low concentrations stimulate root growth while high concentrations inhibit root growth. These results reveal that ethylene action during root elongation is strongly concentration dependent. Furthermore our detailed study of ethylene biosynthesis kinetics revealed a very strict gene regulation pattern of ACC synthase (ACS) and ACC oxidase (ACO), in which ACS is the rate liming step during sugar beet seedling development.

The Role of Auxin-Ethylene Crosstalk in Orchestrating Primary Root Elongation in Sugar Beet

It is well-established in Arabidopsis and other species that ethylene inhibits root elongation through the action of auxin. In sugar beet (Beta vulgaris L.) ethylene promotes root elongation in a concentration dependent manner. However, the crosstalk between ethylene and auxin remains unknown during sugar beet seedling development. Our experiments have shown that exogenously applied auxin (indole-3-acetic acid; IAA) also stimulates root elongation. We also show that auxin promotes ethylene biosynthesis leading to longer roots. We have further demonstrated that the auxin treatment stimulates ethylene production by redirecting the pool of available 1-aminocyclopropane-1-carboxylic acid (ACC) toward ethylene instead of malonyl-ACC (MACC) resulting in a prolonged period of high rates of ethylene production and subsequently a longer root. On the other hand we have also shown that endogenous IAA levels were not affected by an ACC treatment during germination. All together our findings suggest that the general model for auxin-ethylene crosstalk during early root development, where ethylene controls auxin biosynthesis and transport, does not occur in sugar beet. On the contrary, we have shown that the opposite, where auxin stimulates ethylene biosynthesis, is true for sugar beet root development.

Cryopreservation of Cichorium intybus L. var foliosum (Chicory)

Chicory is a member of the Compositae (or Asteraceae) family and belongs to the genus Cichorium. The genus consists of six different species, but only Cichorium intybus L. and Cichorium endivia L. are economically important. The first species is subdivided in three main groups: C intybus var. intybus (wild form), C. intybus var. foliosum (leaf chicory) and var. sativum (root chicory). Within C. intybus var. foliosum,four different cultivar groups are distinguished, among them Belgian endive or witloof chicory (Vermeulen et al. 1994). Chicory originated from the Mediterranean area and is now widespread over Western, Central and Southern Europe, Northern Africa and temperate regions of Asia.