METHOD TO OPTIMIZE THE STORAGE OF HARVESTED SUGAR BEETS

Abstract

A method for predicting the storage ability of sugar beet roots quantifies the mechanical resistance of the root of the sugar beet. A method develops sugar beets with improved resistance, and sugar beets are obtained by this method.

Claims

1. A method for predicting sugar beet resistance to factors causing root damages and/or to factors causing sucrose loss upon storage, comprising quantifying mechanical resistance of a root of a sugar beet.

2. A method for predicting sugar beet resistance to biological factors causing root damages during culture, comprising quantifying mechanical resistance of a root of sugar beets from a same genetic origin.

3. The method of claim 1, wherein the quantification is carried out by penetrometry.

4. The method according to claim 1, wherein the quantification is carried out upon recording force (kg/cm.sup.2) needed to push a probe of a given section through an outer layer of the root.

5. The method according to claim 4, wherein the quantification is a maximal force (kg/cm.sup.2) needed to push the probe of a given section through the root.

6. The method according to claim 5, wherein the sugar beets from several origins are stratified in function of the mechanical resistance of the root of the sugar beets and/or in function of the maximal force needed to push the probe through the root.

7. The method of claim 6, wherein the less resistant sugar beet lots are processed firstly by sugar refineries.

8. The method of claim 6, wherein less resistant sugar beet lots are treated for reducing sucrose losses.

9. The method according to claim 1, wherein factors leading to root damages are sugar beet pathogens and/or parasites, selected from the group consisting of bacteria, fungi, nematodes and larvae thereof, arthropods and larvae thereof, insects and larvae thereof.

10. A method for improving resistance to damage upon storage of a sugar beet comprising the steps of: obtaining sugar beets from different genetic origins, stratifying said obtained sugar beets according to mechanical resistance of a root of said sugar beet from different origins, and selecting most resistant sugar beets.

11. A method for improving resistance of a sugar beet to biological factors causing root damage, comprising the steps of: obtaining sugar beets from different genetic origins, stratifying said obtained sugar beets according to mechanical resistance of a root of the sugar beet from different origins, and selecting most resistant sugar beets.

12. The method of claim 10, wherein the mechanical resistance of the root is measured.

13. The method according to claim 10 further comprising the step of crossing selected more resistant beets from two different origins.

14. A sugar beet, or parts thereof, obtainable by the method of claim 13.

15. A method of using a penetrometer comprising sorting sugar beets according to resistance to sucrose loss upon storage.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0040] FIG. 1. Effect of the number of roots.

[0041] FIG. 2. Penetrometry values in function of the Rot index (Panel A), or of the loss of sucrose (Panel B).

[0042] FIG. 3. Correlation between the mechanical resistance and the outer layer content of hemicellulose (Panel A) and of cellulose (Panel B).

EXAMPLES

Comparative Example

[0043] The inventors have compared the marc content (reflecting the fiber content surrounding the sucrose-containing tissues) of the sugar beet and the rot index (the protocol is detailed in the Example 2) or the loss of sucrose for series of harvested sugar beet varieties. No correlation can be established between the resistance or the density of sugar-containing layers of sugar beet and the rot index or the loss of sucrose.

Example 1

[0044] General Validation of the System

[0045] The inventors have firstly compared penetrometry measurements (PENEFEL penetrometer commercialized by Setop company, Cavaillon, France) performed at different places of a single sugar beet and measured no real difference. As a precautionary measure, the inventors nevertheless propose to establish the measures in the same region of the roots (e.g. at the maximal diameter of the root) and/or to perform several measurements (e.g. at least three) for any root.

[0046] Then the inventors have compared the measurements on a same lot, but taken at different times after harvest.

[0047] Again, no real difference has been measured, though the inventors consider that it is preferable to perform measurements on roots after a constant period after harvest.

[0048] Then the inventors have measured the minimal number of beets to take into account for the intra lot variability (same field conditions, same genetic background). The inventors have noticed a minor variability.

[0049] When performing the measurement on 8 beets, the variability becomes much lower than the variability caused by different genetic origin (see below), and the correlation between the measurements on 8 and on 20 different roots from one lot is excellent; see FIG. 1.

Example 2

[0050] Having validated the system, the inventors then compared the penetrometry data and the rot index or the loss of sugar for series of harvested sugar beet varieties (FIG. 2).

[0051] The maximal force for the insertion of the probe is measured on the basis of three measures per sugar beet root, and of 20 roots per condition. The detection limit is, in this example, of 2 kg/cm.sup.2. A good correlation can be established between the resistance of the beet root and either the rot index or the loss of sucrose (the inter lot variance is 10 or even 50 times bigger than the intra lot variance). The less resistant beets have lost almost twice the amount of sucrose than the most resistant ones.

[0052] More into details, between 60 and 75 manually harvested sugar beet roots from the same lot (genetic origin and, in these settings, field conditions) are separated for three different analysis: the measure of the sugar content at the harvesting time; the conservation analysis and the measure by penetrometry.

[0053] The conservation analysis is carried out after causing a controlled mechanical damage to the manually-harvested roots, aiming at mimicking, in a more homogenous fashion, the damages caused by mechanical harvest, then conservation is done at 12 C. for 7 days, then at 8 C. for 44 days (436 C.*days) with the humidity controlled at 95%, for mimicking the weather conditions during autumn in North-Western Europe.

[0054] Then the sucrose content and the root rot index are measured.

[0055] The root rot index is assessed on the basis of 5 classes: Class 1; healthy beets; Class 2, beets with up to 25% of the surface subjected to rot; Class 3, beets with between 25% and 50% of the surface subjected to rot; Class 4, beets with between 50% and 75% of the surface subjected to rot; Class 5, rotten beets. The index is the averaged sum. The inventors have noticed good homogeneity between lots.

Example 3

[0056] The inventors have then compared in the field the rot index and the insect damages for series of sugar beet varieties.

[0057] Again, there is a negative correlation between these damages and the resistance the root of the sugar beet of the same origin as measured by penetrometry.

Example 4

[0058] The inventors have then developed sugar beets on the basis of the resistance of their roots to the penetrometer. The inventors have stratified sugar beets from the different genetic origins in ten classes according to the measured resistance to the penetrometer of 20 roots per genetic origin. The sugar beets of different origins that have been attributed to the most resistant class have been crossed so as to obtain a progeny with an even more marked resistance phenotype.

Example 5

[0059] Alternative Measurements of the Mechanical Resistance: Chemical Composition of the External Layer

[0060] The inventors have then analyzed the external layer (peel) of sugar beets to determine if their chemical content presents variations and if these variations are correlated either to the direct methods for measuring the mechanical resistance of the outer layer of the sugar beet (as disclosed above), and/or if there is a correlation with the sucrose loss or with the resistance to biological factors during culture.

[0061] To do so, the external peels have been obtained from several sugar beet lots (in practice at least the peels from 4 sugar beets per condition). Then, the peels have been mechanically homogenized (step 1) and their soluble contents (e.g. sugars) are removed with hot water (step 2). A neutral detergent solution is then added on the remaining marc, so as to remove the pectin and the proteins (step 3). Then a first acid solution is added, so as to degrade the hemicellulose (step 4), then a second acid solution (70% H2SO4) is added to degrade the cellulose (step 5), before ashing at 550 C. so as to remove the lignin component and to end with the remaining ashes (step 6). The solid content of the compositions is measured at every step, and the (absolute or relative) abundance of one key component (e.g. cellulose or hemicellulose) is determined by difference (e.g. the hemicellulose content is deduced by subtracting to the solid content after step 3 the solid content after step 4). From these results, the inventors have noticed very good correlations between the hemicellulose (and/or the cellulose) content and the penetrometer measurements (FIG. 3) and/or with the resistance to sucrose loss and/or with the resistance to biological factors during culture. The lignin content, on the other hand, is more constant between lots, and thus a poor readout of the mechanical resistance (R.sup.2 coefficient of about 0.4).

[0062] As a second alternative, homogenized peels (step 1 as above or more preferably, from step 3 as above, after removal of pectin) are analyzed by near-infra red measurements so as to determine their content in hemicellulose and cellulose (the measurement is mainly for =CO and COH residues, abundant in these polymers).

[0063] Again, the inventors have noticed very good correlations between the hemicellulose (and/or the cellulose) content(s) and the penetrometer measurements and/or with the resistance to sucrose loss and/or with the resistance to biological factors during culture.

[0064] In other words, these methods are applied to the external structure of the sugar beet and reflect the mechanical resistance of the sugar beet.