WO1996007319A1

WO1996007319A1 - Improving the yield of plants

Info

Publication number: WO1996007319A1
Application number: PCT/FI1995/000484
Authority: WO
Inventors: Naidu Bodapati; Eija Pehu; Kirsti Jutila
Original assignee: Cultor Oy
Priority date: 1994-09-07
Filing date: 1995-09-07
Publication date: 1996-03-14
Also published as: FI96111C; FI96111B; CA2199368A1; EP0781090A1; BR9508891A; MX9701778A; FI944103A0; PL319031A1; AU3348495A; AU694552B2; CN1159740A

Abstract

The invention relates to the exogenous use of betaine to improve the yield of plants, such as potato and tomato, belonging to the genus Solanum. According to the invention, betaine is used to improve yield especially under stress conditions. The invention also relates to plants of the genus Solanum treated exogenously with betaine, and to products obtained from the plants.

Description

Improving the yield of plants

Technical field The invention relates to the use of betaine to improve the yield of plants. The invention relates especially to the use of betaine to improve the yield of plants belonging to the genus Solanum . According to the invention, the yield can be improved particularly under stress conditions, i.e. when the conditions are poor due to e.g. low temperatures, drought, high salinity or environmental poisons interfering with the growth. The invention also relates to plants of the genus -Solajiuzn treated with betaine and to products obtained from these plants.

Background

The environment and conditions of growth considerably affect the growth result of plants. Optimum growth environment and conditions usually result in a yield that is large in quantity and high in quality. Under poor growth conditions both the quality and the quantity naturally deteriorate.

Several different solutions have been developed to improve the growth conditions and yield of plants. Selecting the right plant for the right growth location is self-evident for a person skilled in the art. During the growing season plants may be protected with mechanical means by utilizing for example different gauzes or plastics or by cultivating the plants in greenhouses. Irrigation and fertilizers are generally used in order to improve the growth. The physiological properties of a plant are manipulated by means of breeding, both with traditional breeding methods and for example with genetic manipulation. The methods are often laborious and impractical, their effect is limited (the economical size of a greenhouse, the limited protection provided by gauzes, etc.), and they are also far too expensive on a global scale. No economically acceptable chemical solutions for protecting plants from environmental stresses have been described so far.

Plants can adapt to some extent to stress conditions. Under these circumstances for example proline and betaine are accumulated in the regions of growth of certain plants. The literature of the art discusses the function and meaning of these accumulated products. On the one hand it has been proposed that the products are by-products of stress and thus harmful to the cells, on the other hand it has been estimated that they may protect the cells (Wyn Jones, R.G. and Storey, R. : The Physiology and Biochemistry of Drought Resistance in Plants , Paleg, .G. and Aspinall, D. (Eds.), Academic Press, Sydney, Australia, 1981).

Zhao et al. (in J. Plant Physiol . 140 (1992) 541 - 543) describe the effect of betaine on the cell membranes of alfalfa. Alfalfa seedlings were sprayed with 0.2M glycinebetaine, whereafter the seedlings were uprooted from the substrate, washed free of soil and exposed to temperatures from -10°C to -2"C for one hour. The seedlings were then thawed and planted in moist sand for one week at which time regrowth was apparent on those plants that had survived. Glycinebetaine clearly improved the cold stability of alfalfa. The effect was particularly apparent at -6^βC for the cold treatment. All controls held at -6^βC for one hour died, whereas 67% of the seedlings treated with glycinebetaine survived.

Itai and Paleg (in Plant Science Letters 25 (1982) 329 - 335) describe the effect of proline and betaine on the recovery of water-stressed barley and cucumber. The plants were grown in washed sand, and polyethylene glycol (PEG, 4000 ol. wt. ) was added to the nutrient solution for four days in order to produce water stress, whereafter the plants were allowed to recover for four days before harvesting. Proline and/or betaine (25 mM, pH 6.2) was sprayed on the leaves of the plant either on the first or third day of the stress or immediately before harvesting. As regards barley, it was noted that betaine supplied either before or after the stress had no effect, whereas betaine added in the end of the stress was effective. Proline had no effect. No positive effect was apparent for cucumber. On the contrary, it was found out that both betaine and proline had a negative effect.

Brief description of the invention

In connection with the present invention it has now surprisingly been found that the yield of plants, such as potato and tomato, belonging to the genus Solanum can be considerably improved by means of exogenously applied betaine. Betaine is especially effective when the plants are subjected to exogenous stress during the growth.

The invention thus relates to the exogenous use of betaine to improve the yield of plants belonging to the genus Solarium. The invention relates especially to the use of betaine to improve the yield of plants under stress conditions.

The invention also relates to plants of the genus Solanum treated exogenously with betaine, to the products of the plants, and to their use as such or as raw material for food industry. The invention also relates to a method of improving the yield of plants of the genus Solanum, in which method growing plants of the genus Solarium are exogenously treated with betaine. The invention further relates to plants of the genus Solanum obtained with the method according to the invention and to the products of these plants.

Betaine is applied to the plant in either one or several successive treatments. The application may be performed for example by spraying together with some other spraying of fertilizers or pesticides, if desired. Betaine utilized according to the invention is transported to the plant cells, actively regulates the osmotic balance of the cells and also participates in other processes of cell metabolism. A cell treated with betaine is more viable even when subjected to exogenous stress factors.

The betaine treatment according to the invention is economically advantageous, and the yield increases in an amount that is economically profitable and significant. The treatment does not produce significantly more work since it may be performed together with other sprayings of fertilizers or pesticides, and it does not require new investments in machinery, equipment or space. It should also be noted that betaine is a non-toxic natural product, which has no detrimental effects on the quality of the yield. Betaine is also a stable substance that remains in the plant cells and thereby has a long-standing effect.

Detailed description of the invention Betaine refers to fully N-methylated amino acids. Betaines are natural products that have an important function in the metabolism of both plants and animals. One of the most common betaines is a glycine derivative wherein three methyl groups are attached to the nitrogen atom of the glycine molecule. This betaine compound is usually called betaine, glycinebetaine or trimethylglycine, and its structural formula is presented below: CH,

CH₃ - N^* - CH-COO-

CH,

Other betaines are for example alaninebetaine and prolinebetaine, which has been reported to for example prevent perosis in chicks. R.G. Wyn Jones and R. Storey describe betaines in detail in The Physiology and Biochemistry of Drought Resistance in Plants (Paleg, L.G. and Aspinall, D. (Eds.), Academic Press, Sydney, Australia, 1981).

Betaine has a bipolar structure and it contains several chemically reactive methyl groups which it can donate in enzyme-catalyzed reactions. Most organisms can synthesize small amounts of betaine for example for the methyl function, but they cannot react to stress by substantially increasing the production and storage of betaine. Best known organisms accumulating betaine are plants belonging to the Chenopodiaceae family, for example sugar beet, and some microbes and marine invertebrates. The main reason for the betaine accumulation in these organisms is probably that betaine acts as an osmolyte and thus protects the cells from the effects of osmotic stress. One of the main functions of betaine in these plants and microbes is to increase the osmotic strength of the cells when the conditions require this, for example in case of high salinity or drought, thus preventing water loss. Unlike many salts, betaine is highly compatible with enzymes, and the betaine content in cells and cell organelles may therefore be high without having any detrimental effect on the metabolism. Betaine has also been found to have a stabilizing effect on the operation of macromolecules; it improves the heat resistance and ionic tolerance of enzymes and cell membranes. Plants of the genus Solanum do not normally store betaine in their cells.

Betaine can be recovered for example from sugar beet with chromatographic methods. Betaine is comπercially available for example under the trademark of BETAFIN, Cultor Oy, Finnsugar Bioproducts. BETAFIN is crystalline water-free betaine of Finnsugar Bioproducts. Other betaine products, such as betaine monohydrate, betaine hydrochloride and raw betaine liquids, are also commercially available and they can be used for the purposes of the present invention.

According to the present invention, betaine is used exogenously in order to improve the yield of plants belonging to the genus Solanum . Betaine is used especially when plants are grown under stress conditions, i.e. when the plants are subjected to periodic or continuous exogenous stress. Such exogenous stress factors include for example drought, humidity, low or high temperatures, high salinity, herbicides, environmental poisons, etc. Treating plants subjected to stress conditions exogenously with betaine for example improves the adaptation of the plants to the conditions and maintains their growth potential longer, thereby improving the yield-producing capacity of the plants. Betaine is also a stable substance that remains in the plant cells. The positive effect of betaine is thereby long-standing and diminishes only gradually due to dilution caused by the growth. Betaine is applied to plants in either one or several successive treatments. The amount used varies depending on the plant variety and the phase of growth. For example in the case of potato, about 0.1 to 20 kg of betaine can be used per hectare. A useful amount is thus for example about 10 kg of betaine per hectare, which corresponds to about 0.01% of the potato biomass. A preferable amount is about 2 to 8 kg of betaine per hectare. For tomato, about 0.1 to 30 kg of betaine per hectare can be used. A preferable amount is about 1 to 6 kg/ha, particularly about 2.5 kg/ha. The amounts given here are only suggestive; the scope of the present invention thus contains all amounts that work in the manner described herein.

Any method suitable for the purpose can be utilized for the application of betaine. Betaine can easily be spread for example through spraying. Such spraying can be performed together with some other spraying of fertilizers or pesticides, if desired. According to the invention, an aqueous solution of betaine is preferably used.

The time of the treatment according to the invention may vary, and a suitable time is determined preferably separately for each plant. If betaine is applied in a single treatment, the treatment is usually performed at an early stage of growth, for example on plants of about 5 to 20 cm. If betaine is applied in two successive treatments, the second spraying is performed preferably in the beginning of flowering or when stress can be forecasted on the basis of the weather. The betaine treatment according to the invention considerably improves the yield of plants belonging to the genus Solanum, for example the amount and quality of the yield. The treatment according to the invention is economically advantageous and the increase in the yield is economically profitable and significant. For example the amount of a potato yield has been increased by more than 30%, and for tomato the amount of yield has been as much as doubled with a suitable application rate of betaine. It must also be noted that a cell treated with betaine or proline remains viable even when subjected to exogenous stress factors, such as low temperatures, drought, high salinity, or the like.

The invention will be described in greater detail by means of the following examples. These examples are only provided to illustrate the invention, and they should not be considered to limit the scope of the invention in any way.

Example 1 The effect of betaine on potato yield was determined under field conditions in two different locations and utilizing four different betaine concentrations: 0 (control), 1.25, 5.0 and 10 kg of betaine per hectare. For the purpose of dosage, an aqueous solution of betaine was prepared, the solution containing 2 ml/1 of non-ionic wetter, Plus-50 (Ciba Geigy), in addition to the desired betaine content. Betaine solution was added in an amount of 640 1/ha at 75% ground cover, and a second application was made during the tuber growing stage. The potato cultivar was Russet Burbank. The places of growth varied for climate, in one ( 1 ) the climate was warmer and drier than in the other (2) where frost occurred^' during the growing season. After the harvesting the tubers were graded into unmarketable (small, green and odd-shaped tubers) and marketable ones, and the weight and number of tubers in the categories were determined. The specific gravity of the tubers was determined with the weight in air-weight in water method. Statistical analysis of the results was performed by means of variance analysis utilizing Genstat statistical package.

In location (1), tuber yield per plant increased from a control value 1.96 kg to 2.42 kg when betaine was used in an amount of 2.5 kg/ha. This was an increase of 23.5% over the control, i.e. about 17 t/ha. The results are shown in Table 1.

Table 1

Effect of betaine on potato yield betaine increase in yield

(kg/ha) (% of the control)

0 100

1.25 112

2.50 123.5

5.00 117.5

10.00 112.5

In location (2), the results deviated to some extent from the results obtained in location (1 ); an increase of more than 10% in the amount of yield over the control was obtained only at the application rates of 5 and 10 kg/ha. The best result was obtained with the application rate of 10 kg/ha, the yield thus increasing 12.6% over the control, i.e. 7.9 t/ha. With the betaine application rate of 10 kg/ha, a clear increase was also detected in the number of marketable tubers per plant. No significant differences were found in the specific gravity of tubers. The values varied between 1.084 and 1.082.

A clear increase in the yield was apparent in both locations in response to exogenous betaine application. However, the yield increase was clearly different in the two locations. The differences may result from two different factors. On the one hand, the stress was different in the locations due to differences in the climate. On the other hand, in location (1) the potato tubers were harvested within one week of the second betaine application, and the second betaine application may not have had any influence on the yield. In location (2 ) betaine was added during the tuber development stage, and the harvesting was performed at maturity about 6 weeks after the application. The results may thus indicate that it is inadvisable to perform the second betaine application within a short span of time.

Example 2

The effect of betaine on potato yield under water stress was determined under field conditions according to the following test arrangement: 1). Normal irrigation (irrigation every 7 days) (WW) 2). Water stress (irrigation every 15 days) (SS) 3). Water stress (irrigation every 15 days) +betaine (SB)

Betaine was added during the flowering of the plants six weeks after planting. The concentration was 0.2M betaine aqueous solution. The solution was sprayed at the rate of moisturizing but not soaking the plants (about 20 ml/plant, i.e. 0.47 g/plant). The potato cultivar was Alpha. The potato was grown in plots of 4.0 x 2.8 m, and the crop was harvested from plots of about 3.0 x 2.1 m. The cultivation proceeded according to normal practice, i.e. fertilizers, insecticides and other pesticides were added, the potatoes were earthed up, etc. The growing time was normal for the location used. The potatoes were harvested 110 days after planting. The results are shown in Table 2. Table 2

Effect of betaine on potato yield under dry conditions

Treatment

Parallel tests ( W) (SS) (SB)

1 16.68 11.16 10.84

11 19.70 11.94 13.70

111 20.66 7.02 14.20

Average 19.01 10.04 12.91

Water stress thus clearly decreased the yield of tubers. On the other hand, the betaine treatment increased the number of tubers considerably under stress conditions. Betaine application performed in a single dose increased the yield of tubers of water-stressed potatoes by 30%.

Example 3

The effect of betaine on tomato yield under water stress was determined under field conditions according to the following test arrangement: 1). Normal irrigation (irrigation every 7 days) (WW) 2). Normal irrigation (irrigation every 7 days)

+ betaine (WB)

3). Water stress (irrigation every 15 days) (SS) 4). Water stress (irrigation every 15 days)

+ betaine (SB)

Betaine was added during the flowering of the plants six weeks after planting. The concentration was 0.2M betaine aqueous solution. The solution was sprayed at a rate of moisturizing but not soaking the plants (about 20 ml/plant, i.e. about 0.47 g/plant). The amount of water added was not essential for the plant's need for water. The cultivation proceeded according to normal practice, i.e. fertilizers, insecticides and other pesticides were added, etc. The growing time was normal for the location used. The results of the tomato cultivation were determined always for ten plants, and the ripe crop was harvested manually during five weeks, beginning eleven weeks after planting. The results are shown in Table 3.

Table 3

Effect of betaine on tomato yield under different conditions

Treatment

Parallel (WW) (WB) (SS) (SB) tests

Average 379 782 492 1,221

Water stress did not produce considerable changes in the tomato yield, on the contrary the stressed plants provided a yield that was 30% larger than that of the normally irrigated plants. On the other hand, the betaine treatment increased the tomato yield considerably; the fruit production of stressed plants more than doubled, and the production of plants growing under normal conditions more or less doubled.

Example 4

The effect of betaine, applied at various stages of growth, on the development and yield of tomatoes was determined as follows. Tomatoes, cv Pacesetter, were planted in single rows 1.5 metres apart. Each row was on a bed ca. 90 cm wide by ca. 20 cm high. The rows were flood irrigated at the frequency of 7 to 14 days during November, 7 to 10 days during December and 5 to 9 days from the start of January until 10 days before harvest. The soil was grey clay loam, pH 5.7.

The trial was laid out as a randomized complete block experiment with 6 blocks, each containing 1 replicate of each treatment. Nineteen untreated control plots were strategically located so that each treated plot was no more than 2 plots removed from an untreated control. The trial occupied an area 10 rows wide (15 metres) by 88 metres long. This was divided into 11 banks of 10 plots, each 8 metres of row. Before the treatments were allocated, each plot was classified according to continuity of the row of plants. Plots with a gap larger than 0.5 metres in length were discarded. The remaining 91 plots were classified into plots with a continuous plant row and plots with 1 or 2 gaps. There were sufficient plots in the first category for 4 blocks and sufficient in the other two categories for 1 block of each.

The betaine glycine used was food grade material, Lot No. 64093334 (21/10/94) and it was supplied by Tall Bennet (Rural) P/L.

The betaine was weighed into 50.0 g and 25.0 g lots and stored in press-capped 250 ml PET containers. Within 1 hour before use, sufficient of these for the application were dissolved in measured volumes of clean water to produce a 200 g/1 solution. These solutions were prepared in 250, 500 or 1000 ml glass-calibrated cylinders and transferred to a 1 litre screw-capped glass bottle. Within 1 hour before use, 25.0 ml of Plus-50 Surfactant (Ciba Geigy) was made up to 250.0 ml with clean water and transferred to a 250 ml screw-capped glass bottle. Depending on the spray volume and swath, 1000, 1500 ml or 2000 ml of spray was prepared for applications 1, 2 and 3 respectively. A 1000 ml glass measuring cylinder with 25 ml graduations was used at all applications. The required volume of the 200 g/1 betaine solution was placed in the cylinder and it was then approximately half filled with water. The required volume of the 10% Spray Plus-50 solution was then added and the cylinder was filled to 1000 ml with water. This mixture was then transferred to a clean PET sprayer bottle with the aid of a funnel. At application 2 a further 500 ml of water was added and at application 3 a further 1000 ml. These volumes were measured using the original 1000 ml cylinder and transferred to the sprayer bottle using the original funnel. The spray was thoroughly mixed by vigorously shaking the PET sprayer bottle. The preparation and application of each spray was accomplished in less than 15 minutes.

Application 1 was made on day 0, at very early flowering. At this stage, the crop was healthy and no stress or pests were evident. Application 2 was made on day 20 at a mid to late flowering stage of the crop, that still was healthy with no considerable signs of stress. Application 3 was made on day 41, the crop being at a very late flowering stage and low levels of Big Bud., Helicoverpa spp . , Tetranychus urticae and Nightshade being observed.

Four doses of betaine were applied in this trial, 1.0, 2.5, 5.0 and 10.0 kg/ha. At application 1 they were designated treatments A, B, C and D respectively.

At application 2 they were designated treatments E, F, G and H respectively. At application 3 they were designated treatments I, J, K and L respectively. Devrinol (napropamide 500 g/kg WP) was applied pre-plant at 6.7 kg/ha for weed control. Throughout the trial a routine programme of fungicides (mancozeb, cupric hydroxide and sulphur) and insecticides (dimethoate and esfenvalerate) was applied. The ripening agent Etherel (400 g/1 ethepon) was applied at ca 1 1/ha on day 75 of this trial. The crop was well supplied with nutrients and it was irrigated frequently. There was never any indication that the crop was subject to more than low levels of stress.

Immediately prior to the first application, all plots were examined and classified according to the continuity of the row in order to block the trial. Additionally, to determine the plant population and crop stage, the plants and plants with flowers were counted in the central 6 metre length of row in each of 12 plots. These plots were selected at random from those that had a continuous plant row.

About 1 hour after application, the height of the crop at each of 10 locations per plot was measured, i.e. at points about 0.8 m apart, starting about 0.8 in from one end. These measurements were repeated 48 and

61 days after the first application (day 48 and day 61).

On day 47 the buds, flowers and fruit on each of 10 plants per plot were counted. The plants selected were at about the same points used for height measurements. It was intended to repeat this assessment at day 60. However, the plants could not be separated without damaging their neighbours, since they were now intertwined. Hence the buds, flowers and fruit in two 40 cm lengths of row were counted. Based on the average plant population of 12 per metre of row this was about the equivalent of 10 plants. Each 40 cm length of row was centred on a point 1.5 metres in from the relevant end of each plot. On day 60 the proportion of red and green fruit was estimated by counting them in 2 partings of row per plot.

Over days 82 and 83 the red and green fruit in a continuous 2 metre length of plant row per plot were counted and weighed.

In 14 plots there were large Nightshade and Wireweed plants. In these instances two 1 metre lengths of row free of weeds and in the centre of ca 2 metres of continuous row were selected.

The 2 or 1 metre lengths of row were measured and the boundaries were cut through to the soil surface with a cane knife. With the 2 metre lengths, cut fruit were discarded. With the 1 metre lengths, the cut fruit from the end nearest an end of the plot were discarded. The cut fruit from the other end were included in the sample and counted as half fruit.

On day 82, before the harvest assessment started, the proportion of foliage damaged by Tetranychus urticae was estimated in 10 quadrats per plot. Each quadrat was 0.5 metres of row and in most plots these were placed edge to edge along the central 5 metres of row. Deviations were necessary where there were gaps in the row or large weeds. The betaine treatment led to a significant increase in the height of the tomato plants between Day 0 and Day 48, due to growth of the plants, and a significant decrease between Day 48 and Day 61. The decrease was doubtless due to the increasing weight of the fruit the plants were bearing.

The betaine treatments had no significant effect on the numbers of buds, flowers or fruit at Day 47 or on the numbers of buds and flowers at Day 61. However, at Day 61 the numbers of fruit varied significantly between treatments as a result of a response to the dose but not to the time of betaine application.

Betaine at 1.0, 2.5 and 10.0 kg/ha significantly increased the yield of red fruit in terms of weight and this appeared to be due to an increase in both numbers and weight per fruit. The yield of the betaine at 5.0 kg/ha was not significantly different from the untreated but was lower than the yield of the other betaine treatments. The response of the green fruit at Day 82 to the dose of betaine was similar to the response of red fruit. But, whereas 1.0 kg betaine/ha produced the greatest increase in the yield of red fruit, 2.5 kg betaine/ha produced the greatest increase in the yield of green fruit. Further, the proportional increase in the yield of green fruit, 109%, was significantly greater than the proportional increase in the yield of red fruit, 13%. The large difference between the effect of betaine on the yield of red and green tomatoes indicated there is a potential to obtain greater increases in the yield of red tomatoes. This is considered most probable in crops that are more stressed than was the crop in this trial.

The results are shown in Table 4.

Under the conditions used, i.e. low levels of stress, the effect of betaine on yield hence varied si¬ gnificantly with dose but not with time of application. Betaine at 1.0, 2.5 and 10.0 kg/ha increased the yield of red tomatoes, while 5.0 kg/ha reduced the yield. The lowest dose gave the greatest increase in yield, 13%. However, 2.5 kg/ha gave the greatest increase in the yield of green fruit, 109%. Totally, the yield was of the order of 80 tonnes per hectare, about 60% more than a well grown commercial crop of this variety is expected to yield.

Betaine applied at mid and late flowering sig¬ nificantly reduced the proportion of foliage exhibiting symptoms of damage by Tetranychus urticae at harvest. The reductions were 11% and 27%, respectively and the trend suggested that higher levels of performance are probable. This therapeutic property of betaine is likely to be useful in IPM programmes. Example 5 This experiment examined whether betaine can be used to protect plants from damage caused by herbicides. The experiment was conducted under field conditions, and metribuzin and cyanazine (Bladex) were used as herbicides and added at a late stage of growing. Five different concentrations of betaine were used: 0 (control), 2, 4, 8 and 12 kg of betaine per hectare. For the purpose of dosage, an aqueous solution of betaine was prepared, and in addition to the desired betaine content the solution contained 1 ml/1 of non-ionic wetter, Plus-50 (Ciba Geigy). Betaine solution was added in an amount of 6401/ha at 25% ground cover. The potato cultivar was Russet Burbank. The location situated at an altitude of 140 m and was periodically plagued by high temperatures and drought. The crop was harvested manually, and the tubers were graded into unmarketable (small, green and diseased tubers) and marketable ones, and the weight and number of tubers in the categories were determined.

In this experiment too, betaine increased the number of tubers. The smallest betaine application rates, 2 to 4 kg/ha, had no significant effect on the yield and the number of tubers. With the highest betaine concentrations the yield and the number of tubers were significantly increased. The number of tubers per hectare increased the most with the betaine concentration of 8 kg/ha, the increase being 21% over the control. The results are shown in Table 5.

Table 5

Effect of betaine on the yield of herbicide- treated potato

Betaine number of tubers (kg/ha) per hectare x 10³ % of the control

0 170 100

2 160 94

4 176 103

8 206 121

12 181 106

Claims

1. Exogenous use of betaine to improve the yield of plants belonging to the genus Solanum.

2. Use according to claim 1, c h a r a c¬ t e r i z e d in that betaine is used in order to improve the yield under stress conditions.

3. Use according to claim 2, c h a r a c- t e r i z e d in that the stress conditions comprise high or low temperatures, drought, excess humidity, or high salinity.

4. Use according to any one of claims 1 to 3, c h a r a c t e r i z e d in that the plant is potato.

5. Use according to claim 4, c h a r a c¬ t e r i z e d in that the potato grows under cold stress.

6. Use according to claim 4, c h a r a c¬ t e r i z e d in that the potato grows under water stress.

7. Use according to any one of claims 4 to 6, c h a r a c t e r i z e d in that betaine is used in an amount of about 0.1 to 20 kg/ha.

8. Use according to claim 7, c h a r a c- t e r i z e d in that betaine is used in an amount of about 2 to 8 kg/ha.

9. Use according to any one of claims 1 to 3, c h a r a c t e r i z e d in that the plant is tomato.

10. Use according to claim 9, c h a r a c- t e r i z e d in that the tomato grows under water stress.

11. Use according to claim 10, c h a r a c¬ t e r i z e d in that betaine is used in an amount of about 0.1 to 30 kg/ha.

12. Use according to claim 11, c h a r a c¬ t e r i z e d in that betaine is used in an amount of about 1 to 6 kg/ha.

13. A method for improving the yield of plants belonging to the genus Solanum, c h a r a c t e r¬ i z e d in that betaine is exogenously applied to a viable plant.

14. A method according to claim 13, c h a r a c t e r i z e d in that betaine is applied to plants growing under stress conditions.

15. A method according to claim 14, c h a r a c t e r i z e d in that the stress conditions comprise high or low temperatures, drought, excess humidity, or high salinity.

16. A method according to any one of claims 13 to 15, c h a r a c t e r i z e d in that betaine is applied once or several times during the growing season.

17. A method according to any one of claims 13 to 16, c h a r a c t e r i z e d in that betaine is applied together with a pesticide, surfactant or fertilizer.

18. A method according to claim 16 or 17, c h a r a c t e r i z e d in that betaine is applied in a single application at an early stage of the growth of the plant.

19. A method according to claim 16 or 17, c h a r a c t e r i z e d in that betaine is applied in successive treatments, the first treatment being made at an early stage of plant growth and the second in the beginning of flowering.

20. A method according to any one of claims 13 to 19, c h a r a c t e r i z e d in that the plant is potato.

21. A method according to claim 20, c h a r a c t e r i z e d in that the potato grows under cold stress.

22. A method according to claim 20, c h a r a c t e r i z e d in that the potato grows under water stress.

23. A method according to any one of claims 20 to 22, c h a r a c t e r i z e d in that betaine is used in an amount of about 0.1 to 20 kg/ha, preferably about 2 to 8 kg/ha.

24. A method according to any one of claims 13 to 19, c h a r a c t e r i z e d in that the plant is tomato.

25. A method according to claim 24, c h a r a c t e r i z e d in that the tomato grows under water stress.

26. A method according to claim 24 or 25, c h a r a c t e r i z e d in that betaine is used in an amount of about 0.1 to 30 kg/ha, preferably about 1 to 6 kg/ha.

27. Plants of the genus Solanum obtained with a method according to any one of claims 13 to 26, and the products thereof.

28. Plants of the genus Solanum treated exogenously with betaine.