GB1583702A - Treating cereal plants with gibberellins - Google Patents

Description

(54) TREATING CEREAL PLANTS WITH GIBBERELLINS (71) We, WALTER WOLFGANG SCHWABE of "Audlea", Bilting, Near Ashford, Kent, England and PETER DAVID HUTLEY-BULL of 37 Newton Road, Faversham, Kent, England, both British subjects, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of treating cereal plants, i.e. monocotyledonous plants of the family Gramineae to increase the yield of harvestable grain.

When cereal crops (e.g. crops of wheat, barley, maize, oats, rye, triticale, rice, sorghum or millett) are grown under normal field conditions, it is frequently found for many varieties that at harvest time, ripe grain-bearing ears are present only on the primary shoot and ripe ear-bearing tillers (i.e. side shoots bearing ripe ears) are absent or present only in small numbers which do not contribute significantly to the amount of grain which can be harvested. (In maize, typically one or two side shoots bear grain and the remainder fail to develop). In cases where significant numbers of tillers are formed spontaneously or are induced artificially, the spikelets on these tillers are usually at much earlier stages of development than the spikelet of the primary shoot and consequently at harvest time, these tillers cannot provide quantities of ripe grain over and above those provided by the primary shoots.

We have now developed a treatment which not only stimulates tiller formation but also advances tiller maturity, thus enabling ripe grain to be derived therefrom.

According to the present invention, there is provided a method of treating cereal plants to increase the yield of harvestable grain, the method comprising (1) applying a gibberellin to an immature growing cereal plant, the gibberellin being applied at a rate of 0.5 to 500 hectare and before the onset of interprimordial elongation in the plant so that the cereal plant produces more ripe ear-bearing tillers which are capable of yielding ripe grain at the same time as the ears of the primary shoots, (2) allowing the cereal plant to grow to maturity and (3) harvesting grain from ears of both said primary shoots and said tillers.

The treatment according to the invention may be advantageously applied to a wide range of cereal cultivars and in particular to cultivars of wheat and barley. Although particularly striking increases in yield have been observed when gibberellins are applied during the early spring to immature plants sown the preceding autumn (i.e. so-called "winter" cultivars) the treatment process of the invention may also be applied to varieties sown in other seasons, e.g. spring-sown varieties.

The timing of the application of gibberellin in accordance with the invention is fairly critical and generally, the gibberellin should be applied only during the early growth phases of the plant.

Any of several developmental parameters may be taken into account to determine a suitable time or times at which the gibberellin should be applied. Thus, for example, the gibberellin may be applied at or around the time when the cereal plants have reached a stage of development indicated by the emergence of the first one or two primary tillers from the sheathing bases of the two lowest leaves. A further indication of a suitable period is that the plants carry three emergent leaves, with the remainder of the leaves eventually borne on the primary shoot being present internally in various stages of development, together with no more than one or two primordial spikelets. Another indication is that at least two secondary tillers are present. one being in the axil of the lowest leaf of each of the two lowest primary tillers. Although not yet emergent, these secondary tillers may easily be seen when the leaves are stripped back. A further morphological indication which may be taken into account in determining when the treatment compositions may be effectively applied is that the apex of the primary shoot above the highest primordium is only slightly elongated, for example with the height being no more that 20% greater than the basal radius. Other developmental parameters may be used to enable an appropriate treatment timing to be selected. Thus the application of gibberellin has been found to be effective up to the time of differentation of glume primordia on the largest spikelets and/or before the onset of interprimordial elongation and/or before differentation of vascular tissue in the spike axis. Preferably the treatment is effected within four weeks of (i.e. not more than four weeks before or after) and most preferably within two weeks of the time when said development parameter or parameters has or have been satisfied.

Although the timing of the application of gibberellins in accordance with the invention is preferably determined by reference to the development of the plants, in practice the treatment may be applied between specified dates. For example in the case of winter-sown cultivars, the treatment of the invention is generally effective when applied in early spring, e.g. in February or March (in the northern hemisphere) and most preferably in March. For spring-sown cultivars, the treatment of the invention is preferably applied in late spring or early summer e.g. in April, May or June (in the northern hemisphere). The particular dates chosen may, of course, vary according to enviromental e.g. climatic conditions and locality.

As indicated above, the method of the invention includes application to cereal plants of a gibberellin. Gibberellins are a known group of plant growth regulators derived commercially from cultures of the fungus Gibberella fujikuroi. These gibberellins include, for example, gibberellin A3, also known as gibberellic acid and on account of its commercial availablility this gibberellin is preferably used in carrying out the method of the invention. However, the use of other gibberellins and mixtures thereorf is included, such as, for example gibberellin A4, gibberellin A7 and mixtures thereof.

The treatment according to the invention has been found to be effective when the gibberellin applied in accordance with step (1) above is used at very low rates of application, and generally application rates in excess of 500g/hectare are considered excessive. Preferably, the gibberellin is applied at a rate of 0.5 to 250g/hectare and most preferably 1 to 200g/hectare, especially 1 to 50g/hectare. For crops grown at conventional densities the optimum treatment rate is 2 to 50, more particularly 2 to 10g/hectare of gibberellin.

Preferably the gibberellins are applied in the form of a composition containing from 5 to 1000 ppm of gibberellin. Particularly outstanding results have been observed when the gibberellins are applied in the form of compositions containing relatively low concentrations of gibberellin particularly concentrations of less than 500 ppm. Preferably these low concentration compositions contain not more than 100 ppm and preferably not more than 50 ppm of gibberellin. Most preferably, the compositions used in the treatment contains less than 20, e.g. from 2 to 20 ppm of gibberellin.

Most preferably, the treatment compositions are applied to the immature growing cereal plants in the form of aqueous or non-aqueous sprays. When such sprays contain gibberellin in the low concentrations stated above, the sprays are preferably applied at a rate of from 0.1 to 0.5 litres/square meter, particularly when crops are grown at conventional densities (e.g. up to 500, more particularly up to 250, and especially from 30 to 100 plants per square metre). Although higher rates of application are not disadvantageous, to avoid waste it is preferred that the spray should not be applied at a rate greater than 0.5 litres per square metre and most preferably at volumes lower than 0.5 litres per square meter.

Where the gibberellin is applied in the form of a spray, the concentration of gibberellin contained in the spray will be dependent on the volume of spray composition to be applied per unit area and vice versa. Thus, for example, where it is desired to apply a spray at a rate of 1000 litre/hectare, the optimum spray concentration is likely to be in the range from 5 to 20 ppm of gibberellin. Where so-called "low volume" spray techniques are used (e.g. at rates of about 250 litre/hectare) the optimum spray concentration is likely to be in the range from 20-80 ppm of gibberellin. Finally, where so-called "ultra-low volume" spray techniques are used (e.g. at rates of about 25 litres/hectare) the optimum spray concentration is likely to be in the range from 200-800 ppm of gibberellin. Thus it will be appreciated that in general. the gibberellin is preferably applied in the form of a spray which, according to its concentration, is applied at a rate of from 0.02 to 0.5 1/square metre.

The amount of gibberellin used can also be expressed in terms of Fg applied per plant.

Thus the preferred quantities of gibberellin applied per plant may be calculated to be from 0.01 to 250 llg most preferably from 0.1 to 100 Fg and especially from 1 to 50 Fg.

Although significant increases in yield have been observed when the treatment composition is applied on only a single occasion. repeated applications, for example two or more applications within the space of a week to 14 days can be advantageous. A particularly pronounced increase in yield has been observed following repeated treatments carried out on consecutive days.

One effect of applying gibberellins in accordance with the invention to immature growing cereal plants is to increase the number of ear-bearing tillers formed per plant. This effect is particularly surprising, especially having regard to the previously observed effects of applying gibberellin to cereal seedlings. Thus, these previously observed effects include stimulation of growth of the primary shoot and suppression of tiller formation. Also, although many cultivars produce tillers spontaneously, the ears on such spontaneously produced tillers frequently do not ripen at the same time as the ears on the primary shoot and hence the grain in the ears on the tillers cannot be harvested. On the other hand, a particularly surprising effect of the method of the invention is that the production of ripe ears on the tillers tends not to occur significantly later than the production of ripe ears on the primary shoot. The mature plants thus not only display a bushier appearance as a result of the increased number of tillers, but additionally have frequently been found to carry a significantly higher number of ears in a condition suitable for harvesting.

Previously known techniques (such as rollering and chemical seed treatments) which promote tillering but without significant achievement of the unexpected effect of the treatment of the invention of advancing tiller maturity, thus enabling the harvesting of ripe grain from ears on tillers contemporaneously with the harvesting of grain from the main ears, may not be utilized in conjunction with the method of the invention. Particularly outstanding results have, however, been observed when gibberellins are the only plant growth regulants applied during the critical growth phases defined herein.

The treatment of cereal plants in accordance with the invention will now be described in more detail by way of example.

Example 1 Two cultivars of wheat (Maris Huntsman and Maris Ranger) and one cultivar of barley (Maris Otter) were grown on respective experimental plots, each having a mean plot size of 15 square metres per plot.

The dates of sowing were as follows: Cultivar Date Sown W. Maris Huntsman 30th October, 1975 W. Maris Ranger 31st October, 1975 B. Maris Otter 1st November, 1975 Additional similar plots of each cultivar were sown on the same dates for use as controls (referred to hereafter as "Local Controls").

A treatment spray which was an aqueous solution of 5 ppm of gibberellic acid and a surface active agent was prepared by dissolving 1 "Berelex" tablet containing 1 gram of gibberellic acid in 200 litres of water and adding thereto 100 ml of "Teepol" surfactant p"Berelex" and "Teepol" are Registered Trade Marks]. Three rates of application were used, namely high (1 litre per square metre), medium (0.75 litres per square metre) and low (0.5 litres per square metre). Plants in separate experimental plots were sprayed on one, two, four and eight successive days at the various treatment rates, the first or sole treatment being applied on 1st March, 1976. The plants on the local control plots received no treatment.

In addition to the Local Controls, one of the wheat cultivars (Maris Huntsman) was grown in a nearby field on Wye College Farm according to standard agricultural practice and the yields in this field were used to provide a standard of comparison for the Local Controls. Additionally, mean control values and sampling ranges were derived from the results obtained in Official Trials carried out in Kent to check both the farm controls and the Local Controls.

On 1st August, 1976 entire plants in the experimental and control plots were harvested and the yield data displayed in the following table determined. The "mean grain dry weight" was measured after oven-drying the grain to constant weight. To provide a valid comparison with "agricultural" yields, a corrected weight allowing for 15% moisture content is given in brackets.

It can be seen from the results given that a startling increase in yield is obtainable using treatment compositions according to the invention, these increases being statistically significant at the 16who and 0.10/c levels. Also correlation coefficients calculated between the treatment levels and earring and yield were of the order of 0.9 and above. These increases in yields are believed to be capable of fully justifying the expense of the treatment.

In the Table, C indicates the Local Control F/C indicates the Farm Control T/C indicates the Official Trial TABLE Cultivar No. of hormone Dry weight Dry grain Adjusted % Yield Ears/ Dry weight/ applications on g/plant yield for 15% increase plant ear successive days tonnes/h moisture content Wheat C 5.41 5.91 (6.68) - 3.90 1.39 (Maris Huntsman) " 1 7.90 8.46 (9.72) 46 4.72 1.67 " 2 8.45 9.04 (10.40) 56 5.50 1.54 " 4 8.84 9.45 (10.86) 63 6.05 1.46 " 8 9.54 10.21 (11.74) 76 6.62 1.44 " F/C 4.55 4.86 (5.59) - 3.52 1.29 " T/C - 4.34 (4.99) - - Wheat C 3.66 3.91 (4.50) - 3.43 1.07 (Maris Ranger) " 1 4.88 5.40 (6.21) 33 4.29 1.14 " T/C - 4.29 (4.93) - - Barley C 4.90 5.25 (6.03) - 6.46 0.76 (Maris Otter) " 1 7.83 8.38 (9.65) 59 9.74 0.80 " 2 8.48 9.09 (10.45) 73 10.34 0.82 " 4 10.20 10.91 (12.51) 108 10.83 0.94 " 8 12.58 13.46 (15.48) 157 12.84 0.98 " T/C - 4.73 (5.44) - - - The data in the Table includes only the results obtained with the lowest of the three rates of application, namely 0.5 litres per square metre, since there was no significant difference between these results and those obtained using the medium and high application rates.

EXAMPLE 2 A. Spring barleyllucerne silage A crop of spring barley intersown with lucerne silage was sown early in April. In the second half of May when the barley had reached the three leaf stage, the crop was treated with an aqueous spray containing 12 ppm gibberellic acid. Sixteen 1/4 acre plots were used in the experiment. Four were sprayed at a rate of 5g/acre of gibberellic acid on only one occasion, four were sprayed on one occasion ten days after the spraying of the first four plots, four were sprayed on both occasions and the remaining four were left unsprayed as controls.

The plants which had received the spray treatments were observed to attain earemergence earlier than the controls.

The field was cut in the third week of July and allowed to wilt for eighteen hours. Then samples were taken and wilted fresh weights estimated. Samples were then dried to obtain a dry weight conversion. The values for the controls were found to be within the normal range for such crops, wilted fresh weight yield being 7.5 tons per acre and dry weight being 39% of wilted fresh weight.

Compared to the controls, the plots treated with gibberellin sprays gave increased yields, expressed in terms of shoots/plant, ears/plant, fresh weight and dry weight as follows: Treatment Percentage Increase over Controls Shoots/Plant Ears/Plant Fresh Weight Dry Weight Early 25% 29% 17% 22% Late 34% 38% 18% 21% Both 55% 59% 40% 38% The spray treatment increased both wilted fresh weight and dry weight yields without significantly affecting fresh weight/dry weight ratios.

B. Winter wheat Part of a ten acre field, sown in the previous autumn with the variety 'Bouquet', was used for this experiment. Ten plots, each of approximately half an acre were used, five being sprayed and five being retained as controls. It was originally intended to spray all five treatment plots twice at a rate of 5g GA/acre/spraying, but with the onset of heavy rain less than four hours after the initial spraying, some doubt existed as to whether the treatment was effective. Consequently, one half of each plot was sprayed once more as intended, whilst the other half received second and third treatments. By the time the field was made available for this experiment the plants had already attained a more advanced state of growth than those treated in the previous year's plot experiments. Consequently this crop provided the opportunity of testing the effectiveness of the spray at a slightly late stage in development but still within the timing parameters defined herein.

Initial treatment responses were apparent within two weeks of the first spraying, shoot elongation and leaf expansion were accelerated and ear emergence was more rapid.

Because of the long, slow growing-season the crop was still standing in the third week of September, when the first analysis of treatment effects was made. This involved removing samples of fifty entire plants from each plot for tiller counts. Because of the advanced state or ripening and the danger of dropping and shedding sampling could not be carried out on a random basis and plants were therefore taken from each side of blind drill rows. A marked treatment effect was apparent in these samples, with increases in the mature ear number of between 30% and 40%. Increased ear number was-reflected in corresponding increases of grain dry weight per plant.

During the last week of September the crop was finally combine-harvested; the grain yield per plot was weighed in the field and individual plot samples were taken for estimation of grain moisture content. The mean yield for the five untreated plots was 1.95 tons/acre (4.9 tonnes/hectare) at low moisture, a good yield for this variety. The mean yield for all ten treated plots was 9.8% higher at 2.14 tons/acre (5.37 tonnes/hectare). A marked fertility gradient was found to exist on the site and the effect of treatment was markedly greater at the more fertile end, i.e. 13% above controls. Throughout, plots receiving three sprays yielded only slightly, though significantly, more than those sprayed twice.

It was found that winter wheat yield can be increased by gibberellin spraying even at a relatively late stage in development, though the gain is smaller than for earlier treatment.

C. Spring wheat Since tillering is known to be affected by plant density and since the winter wheat tested had been sown at the standard rate, a field trial was carried out in which GA sprays were applied to spring wheat, variety 'Sicco', sown at three rates, half, normal and double standard. An area of land of just over an acre was available in the spring, part of which had been treated in the previous autumn with additional phosphorus and potassium fertilizer (P & K fertilizer) was possible also to study at interactions between GA treatment and soil fertility.

Seed was sown in rows which were 7 inches apart in mid-April at the rates of 3/4, 11/2 and 3 cwt/acre, the last being achieved by double-drilling, giving mean spacings in each row of approximately half and twice the standard as well as the standard (1") for this crop. Three blocks were sown, one of these on the P & K treated land, and each block carried all three densities. For spraying, each block was divided into eight plots, each containing three sub-plots at different densities, and four plots in each block were sprayed. The first treatment was applied at the end of May and the three-leaf stage, when each plot received 12 ppm GA equivalent to 5g/acre. The treatment was repeated nine days later during the emergence of the fourth leaf. Microdissections revealed that both sprayings took place during the phase of spikelet initiation, the second shortly before the inception of the terminal spikelet.

Random sampling in mid-September showed that in treated and untreated plots, the numbers of earing and non-earing tillers per plant rose with decreasing plant density, though the increase in the number of ears per plant was insufficient to compensate fully for this and ear density was conseqeuntly reduced. Decreasing plant density was also accompanied by an increase in the number and size of grains in each ear.

A considerable increase in the number of ears per plant was brought about by GA spraying in the least dense sowing, whilst at the standard spacing the number of ears per plant was also increased. At the highest density, where plants were virtually restricted to a single ear, the effect of treatment on ear number per plant was slight. In both treated and untreated plants, grain weight per ear increased as sowing density was reduced, though to a rather smaller extent in treated plants. Nevertheless, the higher ear numbers of treated plants resulted in greater grain yields per plant, the treatment response increasing with decreasing plant density.

The crop was harvested in the last week of September, using a modified 6 ft combine with weighing facilities. After cutting out guard rows, each sub-plot was harvested and weighed individually, giving twelve samples of each density/treatment combination, four from the high P & K land. After correction for moisture contents, which did not differ significantly between treatments, the following values were obtained: Density Treatment Extra P & K tonslacre tonneslhectare %gain Wide (3") Control No 1.39 3.49 GA " ,, 1.63 4.09 17% Control Yes 1.39 3.49 GA " ,, 1.69 4.24 22% Normal (1") Control No 1.40 3.52 GA " 1.52 3.82 8% Control Yes 1.42 3.57 GA " 1.55 3.89 9% Close (3/4") Control No 1.46 3.67 3% GA " 1.50 3.77 Control Yes 1.46 3.67 GA " 1.53 3.84 5% It was apparent from these data that just as in the case of ear number per plant, grain yield was increased by the use of CA sprays. In control plants, grain yield per plant increased with decreasing plant density, but this increase was insufficient to fully compensate for the reduction in plant population and total grain yield therefore fell somewhat. In treated plants, on the other hand, grain yield per plant increased to a greater extent with decreasing plant density and this was sufficient not merely to compensate for the lower plant population but actually brought about an increase in total grain yield as plant density was reduced. Higher P & K levels had no significant effect on yield in untreated plants, but enhanced the effects of GA sprays at all plant densities. Comparison with earing tiller estimates points to a small reduction in grain weight per ear as a result of GA treatment, but this is more than offset by the advantage accruing from increased ear number.

Claims (19)

WHAT WE CLAIM IS:

1. A method of treating a cereal plant to increase the yield of harvestable grain, the method comprising (1) applying a gibberellin to an immature growing cereal plant, the gibberellin being applied at a rate of 0.5 to 500 g /hectare and before the onset of interprimordial elongation in the plant so that the cereal plant produces more ripe ear-bearing tillers which are capable of yielding ripe grain at the same time as the ears of the primary shoots, (2) allowing the cereal plant to grow to maturity and (3) harvesting grain from ears of both said primary shoots and said tillers.

2. A method according to claim 1 wherein the gibberellin is applied to the plant at the time when (a) the first one or two primary tillers have emerged from the sheathing bases of the two lowest leaves, and/or (b) the plants carry three emergent leaves, with the remainder of the leaves eventually borne on the primary shoot being present internally in various stages of development, together with no more than one or two primordial spikelets, and/or (c) at least two secondary tillers are present, one being in the axil of the lowest leaf of each of the two lowest primary tillers, and/or (d) the apex of the primary shoot above the highest primordium is only slightly elongated.

3. A method according to claim 1 or 2 wherein in step (1), the gibberellin is applied at a rate of 0.5 to 250g/hectare.

4. A method according to claim 3 wherein the gibberellin is applied at a rate of 1 to 200g/hectare.

5. A method according to claim 4 wherein the gibberellin is applied at a rate of 1 to 50g/hectare.

6. A method according to claim 5 wherein the gibberellin is applied at a rate of 2 to lOg/hectare.

7. A method according to any one of the preceding claims wherein, in step (1), the gibberellin is applied in the form of a composition containing 5 to 1000 ppm of gibberellin.

8. A method according to claim 7 wherein the gibberellin is applied in the form of a composition containing 5 to 500 ppm of the gibberellin.

9. A method according to any one of the preceding claims wherein the gibberellin is applied in the form of a composition applied at a rate of 0.02 to 0.5 litres/square metre, the composition containing not more than 100 ppm of gibberellin.

10. A method according to claim 9 wherein the composition contains not more than 50 ppm of gibberellin.

11. A method according to claim 10 wherein the composition contains less than 20 ppm of gibberellin.

12. A method according to claim 11 wherein the composition contains 2 to 20 ppm of gibberellin.

13. A method according to claim 9 wherein the composition is applied at a rate of 0. I to 0.5 litres/square metre.

14. A method according to any one of the preceding claims wherein the gibberellin is applied to the plants up to the time of (a) differentiation of glume primordia on the largest spikelets, and/or (b) differentiation of vascular tissue in the spike axis.

15. A method according to any one of the preceding claims wherein the cereal plant is a wheat. barley, oats. rye or triticale cultivar.

16. A method according to any one of the preceding claims wherein the gibberellin is applied on a plurality of occasions within a period of 14 days.

17. A method according to any one of the preceding claims wherein the gibberellin is GA3.

18. A method according to claim 1 substantially as described in any one of the Examples.

19. Grain prepared by a method according to any one of the preceding claims.