Early‐stage sugar beet taproot development is characterized by three distinct physiological phases

Abstract

Despite the agronomic importance of sugar beet ( Beta vulgaris L.), the early‐stage development of its taproot has only been poorly investigated. Thus, the mechanisms that determine growth and sugar accumulation in sugar beet are largely unknown. In the presented study, a physiological characterization of early‐stage sugar beet taproot development was conducted. Activities were analyzed for fourteen key enzymes of carbohydrate metabolism in developing taproots over the first 80 days after sowing. In addition, we performed in situ localizations of selected carbohydrate‐metabolic enzyme activities, anatomical investigations, and quantifications of soluble carbohydrates, hexose phosphates, and phytohormones. Based on the accumulation dynamics of biomass and sucrose, as well as on anatomical parameters, the early phase of taproot development could be subdivided into three stages—prestorage, transition, secondary growth and sucrose accumulation stage—each of which was characterized by distinct metabolic and phytohormonal signatures. The enzyme activity signatures corresponding to these stages were also shown to be robustly reproducible in experiments conducted in two additional locations. The results from this physiological phenotyping approach contribute to the identification of the key regulators of sugar beet taproot development and open up new perspectives for sugar beet crop improvement concerning both physiological marker‐based breeding and biotechnological approaches.

Rhizosphere bacterial colonization of beet occurs in discrete phases regardless of bioinoculation with the wild sea beet root community

“…The phases observed here seem to be in line with beet taproot growth phases, our early phase corresponding to transition/secondary growth onset and the late one to the beginning of sucrose storage phase [29]. Therefore, we think that under stable environmental conditions the late phase could last at least until flowering (in the case of a perennial -sea beet) or overwintering (in the case of a bi-annual -sugar beet), which are next major events in beet life.…”

Differential sensitivity of metabolic pathways in sugar beet roots to combined salt, heat, and light stress

“…Sucrose synthase is the main sucrolytic enzyme in sugar beet roots. A developmental study exploring carbohydrate metabolism in sugar beet roots during their first 80 days after sowing revealed a continuous decline of cell wall, vacuolar and cytoplasmic invertase activities reaching very low values at day 53, while sucrose synthase activity increased throughout this time period and particularly steep between days 60 and 80 (Jammer et al, 2020). This comprehensive study only explored control growth conditions addressing a wide range of enzymes and metabolites of carbohydrate metabolism (Jammer et al, 2020) and might be a good blueprint for deeper analyzing the response of carbohydrate metabolism to combined stress scenarios.…”

“…The photosynthetic radiation under control growth conditions was about 80–100 μmol photons m −2 s −1 . This is a low light intensity but not uncommon, for example, Jammer et al (2020) applied >75 to >200 μmol photons m −2 s −1 . The strongest stimulatory effect of the 6 h high light treatment on metabolite contents occurred in low salt control plants.…”

“…This might indicate that sucrose-metabolizing enzymes, especially between days 60 and 80 (Jammer et al, 2020). This comprehensive study only explored control growth conditions addressing a wide range of enzymes and metabolites of carbohydrate metabolism (Jammer et al, 2020) and might be a good blueprint for deeper analyzing the response of carbohydrate metabolism to combined stress scenarios.…”

High stability of genotypic differences in puncture resistance of sugar beet (Beta vulgaris) roots under various growing conditions

“…The early establishment of puncture resistance could be related to the development of the periderm, which takes over the protective function of the primary cortex from ca. 40 days after sowing onwards at a root diameter of approximately 24 mm (Artschwager, 1926; Jammer et al, 2020). For our study, the diameter of the root is more suitable for comparison with other studies than the number of days after sowing.…”