Variability in white clover from the Indian Himalaya

by

Dr Sindhu Sareen

Regional Research Centre
Indian Grassland, Fodder and Agroforestry Research Institute
HPKV Campus, Palampur – 176 062 (India)

[Posted February 2003]

 

Introduction

Although a temperate species, found where soil moisture is adequate for growth, white clover is widely adapted to regions from the Arctic to the sub tropics and has a wide altitudinal range, being reported up to 6000m in the Himalayan range of India. The likely centre of origin is the Mediterranean region (Kousnetzoff 1926; Vavilov 1951; Williams 1987) and the indigenous area includes the whole of Europe and Central Asia, west of Lake Baikal as well as areas in North Africa (Figure 1).

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Figure 1. Distribution of white clover (Source, Williams 1987)

It was spread to other continents by colonists. It grows in a wide range of habitats including dry meadows, mud flats, rarely on saline meadows, wood margins, open woods, banks of rivers and brooks, plains, semi desert regions and mountains up to the sub-alpine meadows. It is frequently found on roadsides and in barren areas.

It is one of the most nutritious and widely grown forage legumes in the world. It improves forage quality and has potential to fix nitrogen in the range of 600 – 700 kg N/ha/year (Crush 1987), although the annual nitrogen fixation levels from white clover in grazed pastures are extremely variable, ranging from 17kg N/ha/year in infertile, unimproved hill pastures (Grant and Lambert 1979) to 380 kg N/ha/year in intensively managed pastures (Rumball 1979). Higher clover content in diet increased nutritive value, energy and protein intake (Thomson 1984; Harris et al. 1998). Because of its stoloniferous growth and phenotypic plasticity, it is an ideal companion legume in most grass swards (Woodfield and Caradus 1994). Woodfield and Caradus (1994) reported genetic gain of 6% per decade for its yield, which is higher than rates reported for other forage crops.

Materials and methods

During the present study on variability and evaluation of white clover populations, a part of north-western Himalaya comprising Himachal Pradesh, Jammu & Kashmir and Uttranchal was explored and about two hundred populations were collected. In addition, some twenty exotic lines were procured. These populations were raised under uniform conditions at IGFARI Regional Research Centre, Palampur and were studied for morphological parameters, flowering intensity, pollination, herbage and seed yield and quality parameters. The morphological parameters were studied in field plots, when the plants attained 50% flowering. The flowering intensity was marked visually on a scale of 0 – 5. The herbage and seed yield were extrapolated from the yield of 1 square metre. The fresh weight of herbage was taken in the field plots and later dried and analyzed for quality parameters.

The individual flower heads were bagged to determine selfing. The stigmas from the bagged florets were fixed in fixative consisting of ethyl alcohol and acetic acid in the ratio of 3:1 and then stained with Lewis stain to observe pollen load and self pollen germination.

For cyanogenesis, the picrate paper method was used and the intensity of brown colouration of the paper was marked on a scale of 0-5, with 0 indicating no colour change.

Results and Discussion

The indigenous populations in the present study were highly variable and the extent of morphological variability (Figures 2 & 3) is evident from the data given in Table 1.

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Figure 2. Variation in leaf size in white clover populations.
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Figure 3. Variation in white clover populations.
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The coefficient of variation for nine of the characters studied was close to or more than 50%. The 1000-seed weight parameter was least variable. Considerable variability in white clover populations, landraces and cultivars has been reported. Large intra population variation in natural populations and landraces of Ladino white clover (Annicchiarico 1993; Annicchiarico and Piano 1995) and non-ladino natural populations (Burdon 1980; Caradus and Woodfield 1990) is on record. When grown under favourable conditions, white clover is a long-lived perennial, by virtue of the constant renewal of plantlets that root at the stolon nodes. It has a prostrate growth habit and the individual may spread in diameter up to more than 1m and its height may be more than 1.14m. There are three major types of white clover depending upon the size: small, intermediate and large. The small type is considered as a weedy type, intermediate as common white clover and the large or giant type as Ladino. Yield potential and persistence are two main factors responsible for its adaptation. Leaf size and upright habit (Caradus 1986) and stolon growing points (Williams et al. 1982) contribute to yield potential and persistence. The large leaved upright varieties are higher yielding but less persistent than the small leaved prostrate varieties. The populations in the present study were highly variable for leaf size, plant height, stolon branches and number of growing points. The coefficient of variation for these parameters was more than 30%. The fresh herbage production among these collections varied between 0.10t/ha to 7.88t/ha.

The flowering in white clover is non-synchronous (Figure 4) and the flowering continues throughout the year.

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Figure 4. Non-synchronous flowering in white clover populations
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However, there are two peaks for flowering: the first one is from March to May and second from July to August. The anthesis takes place in the early hours of the day and anther dehiscence takes place within the bud. White clover is self-incompatible and therefore, these pollen grains do not germinate on the stigma. The cross pollination is felicitated predominantly by honey bees (Figures 5a & 5b).

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Figures 5a and 5b. Insect pollination

The bees visit the flowers for nectar present at the base of the staminal tube and during this process cause pollination. Bee visits reach a maximum in the forenoon. Self pollen does not inhibit cross pollen activity but represents a constraint for pollination which demands multiple bee visits to each flower to achieve maximum fertilization (Rodet et al. 1998). Among present collections, a few plants set seed on selfing although seed set was very low in such cases. The seed set on selfing can be increased by rubbing the floret gently between thumb and finger, which causes the same effect as insects. In some populations, in situ pollen germination within anthers (Figure 6) was observed.

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Figure 6. Insitu pollen germination
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These pollen tubes move towards the stigma indicating the possibility of selfing. Seed in white clover is harvested in May depending upon the climatic conditions. The seed formation during the second peak of flowering is very low due to climatic conditions (rainy season) and lack of pollinators. The seed production in white clover is highly erratic. The seed yield among these collections ranged between 0.053 t/ha to 0.8 t/ha. As well as climatic conditions, competition among reproductive organs, pollination success and genetic make up are responsible for low seed harvests. Sareen (2000) evaluated the seed production potential under different light conditions and found that ovule count as well as seed set was more in lower or first formed florets than in upper florets and the populations growing under partial shade set maximum seed. However, it was emphasized that ovule sterility, lack of pollination and post fertilization abortion are responsible for low seed set. These results support the study by Pasumarty and Thomas (1997) that shading reduced ovule fertility, seed number per floret and caused abortion.

The collections of white clover also varied in their nutritive value. The crude protein varied from 15.36% to 26.68%, ADF 42.98% to 53.26% and NDF 33.45% to 42.18% (DM). The collections were also screened for cyanogenesis. Forty-seven percent of these collections were acyanogenic and fifty-three percent were cyanogenic. It is considered that cyanogenesis protects the plant from predators. According to Crush and Caradus (1995) in New Zealand agronomically successful cultivars were highly cyanogenic. However, Coop and Blakely (1950) considered it unwise to breed clovers exceeding 700g HCN/g DM basis.

Conclusions

This study revealed that there exists enormous variability among and within indigenous populations of white clover which should be exploited for improvement of white clover with respect to herbage yield, seed yield and persistency. These collections were grouped into sixteen categories and of these, seven elite lines have been identified which hold promise for pasture improvement.

References

Annicchiarico, P. 1993. Variation for dry matter yield, seed yield and other agronomic traits in ladino white clover landraces and natural populations. Euphytica 71: 131-141.

Annicchiarico, P. and Piano, E. 1995. Variation within and among Ladino white clover ecotypes for agronomic traits. Euphytica 86: 135-142.

Burdon, J.J. 1980. Intraspecific diversity in natural populations of Trifolium repens Journal of Ecology 68: 717-735.

Caradus, J.R. 1986. Variation in partitioning and percent nitrogen and phosphorus content of the leaf, stolon and root of white clover genotypes. New Zealand Journal of Agricultural Research 29: 367-379.

Caradus, J.R. and Woodfield, D.R. 1990. Estimates of heritability for and relationships between root and shoot characters in white clover. I. Replicated Clonal Material. Euphytica 46: 203-209.

Coop, I.E. and Blakley, R.L. 1950. The metabolism and toxicity of cyanogenetic glucosides in sheep III. The toxicity of cyanides and cyanogenetic glucosides. New Zealand Journal of Science & Technology 31: 44-58.

Crush, J.R. 1987. Nitogen fixation. In: M.J. Baker and W.M. Williams (Eds) White Clover, CAB International Wallingford, UK pp 185-201.

Crush, J.R. and Caradus, J.R. 1995. Cyanogenesis potential and iodine concentration in white clover (Trifolium repens L.) cultivars. New Zealand Journal of Agricultural Research 38: 309-316.

Grant, D.A. and Lambert, M.G. 1979. Nitrogen fixation in pasture V. Unimproved North Island hill country, ‘Ballantrae’. New Zealand Journal of Experimental Agriculture 7: 19 – 22.

Harris, S.L., Auldist, M.J., Clark, D.A. and Jansen, E.B.L. 1998. Effects of white clover content in the diet on herbage intake, milk production and milk composition of New Zealand dairy cows housed indoors. Journal of Dairy Research. 65 (3): 389-400.

Kousnetzoff, V.A. 1926. Areas of the geographical distribution of the most important forage species of clover and alfalfa. Bulletin of Applied Botany, Leningrad 16: 55-58.

Pasumarty, S. V. and Thomas, R.G. 1997. Limitations to seed set in white clover (Trifolium repens L.) III. The effect of inflorescence shading on fertility and subsequent seed formation. Journal of Applied Seed Production 15: 29-36.

Rodet, G., Vaissiere, B.E., Brevault,T. and Torre-Grossa, J.P. 1998. Status of self pollen in bee pollination efficiency of white clover (Trifolium repens L.). Oecologia 114 (1): 93 -99.

Rumball, P.J. 1979. Nitrogen fixation in pasture II. Northland warm temperate, Kaikohe. New Zealand Journal of Experimental Agriculture 7: 7-9.

Sareen, S. 2000. Seed production potential of white clover populations growing under different light conditions. Plant Varieties and Seeds 13: 125-128.

Thomson, D.J. 1984. The nutritive value of white clover. British Grassland Society Occasional Symposium 16: 78-92.

Vavilov, N.I. 1951. The origin, variation, immunity and breeding of cultivated plants. Chronica Botanica 13: 116.

Williams, W.M. 1987. Adaptive variation. In: M.J. Baker and W.M. Williams (Eds) White Clover, CAB International Wallingford, UK pp 299-321.

Williams, W.M., Lambert, M.G. and Caradus, J.R. 1982. Performance of a hill country white clover selection. Proc. New Zealand Grassland Association 43: 188-195.

Woodfield, D.R. and Caradus, J. R. 1994. Genetic improvement in white clover representing six decades of plant breeding. Crop Science 34 (5): 1205-1213.

 

 

Table 1. Variability in white clover collections

Character

Range

Average S.D.

CV%

Plant height (cm)

1.65 - 13.90

5.912 2.711

45.86

Mid leaflet (mm)

3.20 - 8.60

4.625 2.374

51.33

Petiole length (cm)

1.28 - 13.60

5.480 2.655

48.45

Stolon branch (cm)

2.08 - 11.62

6.390 1.632

25.54

Stolon diameter (mm)

0.10 - 0.38

0.217 0.048

22.12

No. of stolon branches

2.00 - 16.00

6.352 2.047

32.23

Nodes/stolon branch

1.40 - 8.80

4.976 1.470

29.54

No. of growing points

2.50 - 11.00

5.886 1.709

29.03

Root length(cm)

2.53 - 13.87

6.631 3.093

46.64

No. of roots

3.00 - 46.00

11.017 7.570

68.71

Nodules/root

1.53 - 17.00

4.977 2.597

52.18

Heads/plant

27.00 -153.00

90.846 33.240

36.59

Florets/head

17.50 - 62.00

41.723 10.518

25.21

Seeds / floret

0 - 3.80

2.259 0.835

36.96

Seeds /head

0 -191.00

93.465 47.841

51.19

1000 seed weight (g)

0.53 - 0.56

0.542 0.006

1.11

Peduncle length (cm)

2.56 - 15.30

8.522 3.183

37.35

Peduncle diameter (mm)

0.10 - 0.20

0.121 0.032

26.44

Seed yield (t/ha)

0.053- 0.80

0.218 0.140

64.22

Herbage (t/ha)FW

0.10 - 7.88

5.430 5.520

101.66

Cyanogenesis (0-5 scale)

0 - 4.83

1.646 1.513

91.92

Crude Protein%(DM basis)

15.36 - 26.68

20.045 2.590

12.92

NDF%(DM basis)

42.98 - 53.26

47.418 2.500

5.270

ADF% (DM basis)

33.45 - 42.18

38.019 2.240

5.890