1
A mature rubber plantation
Amazonian accessions of wild
Hevea
germplasm – A potential source of
drought tolerance
M. A. Mercy, D.B. Nair, Meena Singh, T. Meenakumari,
C.P. Reghu and Kavitha K. Mydin
Rubber Research Institute of India, Kottayam – 686 009, Kerala, India
Rubber Board
(Ministry of Commerce & Industry, Government of India)
Email for correspondence:

Introduction
Expansion of
rubber
cultivation from
traditional to
non-traditional
regions in India
2
Introduction contd…
Early detection of stress resistant traits – useful
for the development of location specific clones.
The narrow genetic base of Wickham genepool
and the unidirectional selection for yield limits the
availability of sufficient genetic variability.
1981-IRRDB germplasm collection – a valuable
reservoir of genes for various abiotic stresses.
3
Acre : Brasileia, Feijo, Sena Madureira, Tarauaca, Xapuri

6
7
Morphological Characters
 Scion height (cm)
 Scion basal diameter (mm) at 20 cm
from the bud union
 Number of leaves
 Number of leaf flushes per plant
 Inter-flush distance (cm)
 Single leaflet area (cm2)
 Specific leaf weight (SLW)
Observations
Morphological parameters of selected accessions
Genotypes Plant height
(cm)
Basal diameter
(mm)
No. of
flushes
No. of
leaves
Inter flush
distance
(cm)
Single leaflet
area (cm
2
)
SLW
(g cm

AC 446 115.77
abc
13.49
ab
2.83
abcd
48.47
de
35.26
ab
86.84
a
0.005
a
RRIM 600 104.95
c
11.61
ab
2.28
bc d
51.44
de
22.67
b
58.82
b
0.006
a
Tjir 1 104.9
c

3
abc
77.22
abcd
28.59
ab
60.85
b
0.006
a
MT 66 99.75
c
13.63
ab
2.69
bc d
48.25
de
19.57
b
81.56
a
0.007
a
MT 938 130.67
abc
11.5
ab
2.17
cd

80.44
a
0.006
a
RRII 105 108.31
bc
11.66
ab
2.25
bc d
50.08
de
20.15
b
61.52
b
0.007
a
AC 728 112.29
abc
13.1
ab
2.33
bc d
55.44
cde
24.47
b
90.78
a

MT 3714 Narrow
Curved Nil 100 Medium 84
AC 441 Narrow
Flat Nil 100 Medium 100
MT 81 Broad
Flat Nil 13.75 Medium 8.33
MT 200 Broad
Flat Nil 61.25 High 45
RO 217 Narrow Flat Nil 40.0 High 34
RO 1520 Broad Flat Nil 88 Low 86

Morphological characterization based on drought sensitive parameters
Contd….
9
Acce
ssion
Leaf size Leaf
surface
Wax
coat
Yellowi
ng (%)
Vigour Senesne
nce (%)
MT
1623
Narrow
Curved Nil 7.5 High 0
MT
1681

Rank
No.
Fv/Fm Quantum Yield Fv’/Fm’
1 MT 4713 MT 4859 MT 4787
2 RO 4580 RO 4913 AC 4833
3 MT 4856 AC 4689 MT 4772
4 MT 5100 MT 4788 MT 5152
5 MT 4772 MT 4856 MT 4856
6 MT 5078 MT 4756 MT 5100
7 MT 4802 MT 5078 MT 4713
8 MT 4788 MT 5100 MT 4788
9 MT 5152 MT 5089 AC 4689
10 MT 5114 MT 4747 MT 5078
The chlorophyll fluorescence parameters and
percentage inhibitions in top ranking clones.
Sl.No. Accession % inhibition
in Fv/Fm
% inhibition
in Q.Y.
% inhibition
in Fv’/Fm’
Top ranking germplasm accessions
1 MT 5100 6.0 4.3 4.2
2 MT 5078 12.6 4.5 7.6
3 MT 4788 10.0 8.8 10.7
4 MT 4856 14.0 10.0 20.0
Bottom ranking germplasm accessions
1 MT 4694 54.0 37.0 47.0
2 RO 4615 30.0 30.7 24.5
11

S 2.9 ± 0.92 22.4
__________________________________________________
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AN Leaf water
potential (-Mpa)
(April )
MT 3714 (-2.27)
MT 1631 (-2.4)
MT 48 (-2.67)
MT 1681(-2.93)
MT 1584 (-3.06)
RRII 208 (-3.07)
Tjir 1 (-3.34)
RRIM 600 (-2.8)
RRII 105 (dried)
CD= 0.35 **
** Significant at 1%
Clonal variation in afternoon leaf water potential
Percent leaf yellowing and senescence (ranges) of top,
middle and bottom ranking accessions selected from
source bush nurseries (SBN) by empirical scoring
Germplasm
Nursery
Yellowing (%) Senescence (%)
Top Middle Bottom Top Middle Bottom
SBN 2003
0 -5 14 -15 25 -40 0 -1 10 -15 20-40
SBN 2004
0 -15 40 -45 60 -85 0 -1 15 -20 80 -90
SBN 2005

Total 3772 165 121
No. of wild accessions selected from
germplasm source bush nurseries for
intrinsic tolerance to drought stress
Structural parameters :
Leaf
- Stomatal density- Number of stomata
per mm2 in the abaxial surface
- Thickness of palisade tissue (µm)
- Thickness of mesophyll tissue (µm)
- Mean number of cells in unit length of
the palisade layer
- Leaf lamina thickness ( µm)
- Leaf vein (midrib) diameter (mm)
Stem
- No. of primary xylem points and intra xylary phloem
(from one year old twig)
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Accessions No. of
stomata per
mm
2
Leaf
thickness
(

m)
Midrib
diameter
(

abcd
105.77
fg
310.67
g
48.04
efg
86.35
ef
28.60
de
AC 446
276.69
d
117.90
bcde
371.00
bcd
47.73
efg
84.95
f
30.22
bcd
RRIM 600 356.67
abcd
123.77
abc
352.20
defg

MT 76 357.30
abcd
127.83
a
346.48
defg
59.37
abc
102.78
abcd
31.19
abcd
MT 66 481.48
a
109.43
efg
419.53
a
48.31
efg
88.50
def
34.59
a
MT 938 296.29
cd
121.50
abcd
311.90
fg

RRII 105 427.01
abc
127.27
ab
400.20
abc
58.08
abcd
107.26
abc
32.38
abcd
AC 728 394.34
abcd
113.73
def
318.67
efg
51.64
cdef
92.47
cdef
26.04
ef
Mean 376.19 119.03 361.94 52.5 98.18 31.3
Variability for leaf structural characters of selected
accessions of Hevea brasiliensis
Transverse section of one year old twig of wild Hevea accession
MT 1623 having maximum number of IXP
IXP

MT 3714 74.25 59.25 17.90 3.31
MT 48 54.67 38.79 12.80 3.03
Tjir 1 60.83 30.67 12.50 2.45
RRII 105 48.60 38.20 9.00 4.24
RRII 208 56.00 39.88 11.90 3.35
RRIM 600 57.48 49.15 7.70 6.38
CD **
30.15 30.40 3.88
CV 26.53 42.04 15.08
** Significant at 1%
Potential accessions for structural traits along with twig diameter
Biochemical parameters:
- chlorophyll content
- chlorophyll stability
- wax content
- cell membrane stability
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Clonal variation in leaf chlorophyll content after
drought treatment (C- control, S- drought stressed)
__________________________________________________
Clones Chlorophyll content %Reduction
(mg/g/fw)
__________________________________________________
RRII 105 c 3.67 ± 0.09
S 2.78 ± 0.09 24.5
RRIM 600 C 3.12 ± 0.16
S 2.86 ± 0.03 8.8
MT 4788 C 2.97 ± 0.11
S 2.40 ± 0.13 19.1
MT 5100 C 3.31 ± 0.16

RO 5163 MT 5098
MT 5100
MT 5156
Potential accessions identified for various biochemical parameters
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Accessions % injury Accessions % injury
AC 4677 27.1
MT 5125 19.6
RO 5047 25.6 MT 4740 23.6
MT 4694 17.9 MT 5093 20.3
MT 4878 55.5 RO 4595 32.4
RO 5023 66.6 RO 4620 42.1
AC 4833 55.7 RRII 105 36.9
MT 5156 67.1 RRIM 600 18
CD = 8.95 **
** - Significant at P = 0.01
Variation for cell membrane injury among the
selected accessions
Screening at hot-spot
(RRS, Dapchari)
Maharashtra state in W.India
Weather conditions at RRS, Dapchari
- a drought- prone region experiencing high
temperature (exceeding 40
o
C in April)
- high light intensity
- very low soil moisture during summer months.
- rainfall pattern limited only to four months in a year
- average annual rain fall of 7.5mm per day

5.6
(RO 3660)
3.33 0.92 3.62 4.64 3.78 3.89
No. of leaves 12.0
(MT 195)
71.2
(MT 1623)
42.33 16.87 41.17 62.4 53.44 52.76
No. of leaves
fallen
23.0
(RO 1322)
167.0
(RO 93)
46.86 18.25
41.02
47.1 44.38 54.73
Senescence
(%)
32.74
(MT 4222)
77.37
(RO 93)
52.44 12.86 49.70 42.83 45.27 49.63
First year post- drought data on range and mean of growth
characters in the hot-spot region
Drought tolerant and susceptible accessions
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Accession Test tap yield
(g)of10

hot-spot region
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Mature yield of Amazonian accessions
At RRS, Padiyoor (Northern Kerala)
- summer period (February- May)
- temperature 35
0
C
- rainy days 122/yr.
- high evaporation ( 5- 6 mm/day)
Accessions Summer
season yield
(g/t/t )
Total yield
( g/t/t)
% of the
yield of RRII
105
5
th
yr. 5
th
yr. 5
th
yr.
AC 166 46.03 56.08 91.20
MT 1020 18.00 26.97 43.00
MT 179 14.37 23.57 38.00
RO 2908 16.48 43.78
71.00

region
MT 54, MT 1579, MT 67, MT 1668, MT 1616, MT 1627, MT 1649, MT 80, MT 41, RO
1248, AC 765, RO 2524, MT 945, MT 58, MT 1668, MT 1681, MT 1710, RO
2387,RO 2153, RO 85, MT 4788
Yield (non
traditional)
RO 1769, RO 2976
Yield (traditional) AC 166, MT 1020, MT 179, RO 2908, AC 675
Highlights from various studies
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Conclusions
Genetically divergent Amazonian accessions are an
excellent repository of genes imparting tolerance to
abiotic stress.
A potential source for drought tolerant accessions.
Of the three provenances, accessions from Mato
Grosso are the most promising for developing
drought tolerant clones.
Thank you all