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Frequency Distribution of Growth of All 821 Rubber Seedlings at 15 Years of Age Originating from Rondonia State (Brazil)


fi(%)

































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12


9


6


3


0 cm

30 40 50 60 70 80 90 100 110

Figure 3.11 Frequency distribution of growth of all 821 rubber accessions at 15 years of age originating from Rondonia state (Brazil)

Table 3.22 The most vigorous varieties at age 15 in experiments with a selection ratio of 5%


Breed group

Experiment

Born at 15

Specimen

cm

Compared with control GT1 (%)

RO/A/7/147

RO/A/7

SGLK85

94.7

149.4

RO/A/7/165

RO/A/7

SGLK85

90.6

142.9

RO/A/7/224

RO/A/7

SGLK85

90.4

142.6

RO/A/7/241

RO/A/7

SGLK85

86.8

136.9

RO/A/7/254

RO/A/7

SGLK85

105.1

165.7

RO/A/7/288

RO/A/7

SGLK05

86.3

139.4

RO/A/7/298

RO/A/7

SGLK06

87.8

149.0

RO/A/7/383

RO/A/7

SGLK85

92.9

146.5

RO/A/7/398

RO/A/7

SGLK05

84.3

136.2

RO/A/7/518

RO/A/7

SGLK85

90.9

143.4

RO/C/8/16C

RO/C/8

SGLK05

93.1

150.3

RO/C/8/206

RO/C/8

SGLK85

95.1

149.9

RO/C/8/21

RO/C/8

SGLK85

91.5

144.3

RO/C/8/283

RO/C/8

SGLK85

92.0

145.1

RO/C/8/339

RO/C/8

SGLK04

96.6

176.5


Table 3.22 The most vigorous varieties at age 15 in experiments with a selection ratio of 5% (cont.)


Breed group

Experiment

Born at 15

Specimen

cm

Compared with control GT1 (%)

RO/C/8/435

RO/C/8

SGLK05

91.2

147.3

RO/C/8/47

RO/C/8

SGLK85

96.2

151.7

RO/C/8/59

RO/C/8

SGLK85

88.4

139.4

RO/C/9/290

RO/C/9

SGLK04

83.8

153.1

RO/C/9/33C

RO/C/9

SGLK03

88.4

148.3

RO/C/9/353

RO/C/9

SGLK85

87.0

137.3

RO/C/9/365

RO/C/9

SGLK85

98.4

155.2

RO/C/9/83

RO/C/9

SGLK96

75.9

144.1

RO/CM/10/268

RO/CM/10

SGLK85

99.4

156.7

RO/CM/10/320

RO/CM/10

SGLK85

87.6

138.1

RO/CM/10/481

RO/CM/10

SGLK04

96.0

175.4

RO/CM/10/661

RO/CM/10

SGLK03

86.9

145.8

RO/J/5/69

RO/J/5

SGLK85

90.4

142.6

RO/J/6/104

RO/J/6

SGLK94

90.3

159.8

RO/J/6/23

RO/J/6

SGLK96

80.2

152.1

RO/J/6/49

RO/J/6

SGLK05

84.3

136.2

RO/J/6/57

RO/J/6

SGLK96

81.4

154.4

RO/JP/3/111

RO/JP/3

SGLK94

76.6

135.6

RO/JP/3/334

RO/JP/3

SGLK04

107.0

195.5

RO/JP/3/37C

RO/JP/3

SGLK05

89.9

145.2

RO/JP/3/473

RO/JP/3

SGLK91

77.9

121.4

RO/JP/3/501

RO/JP/3

SGLK04

85.1

155.5

RO/OP/4/100

RO/OP/4

SGLK06

84.4

143.2

RO/OP/4/17C

RO/OP/4

SGLK03

84.2

141.2

RO/OP/4/85

RO/OP/4

SGLK85

86.8

136.9

RO/OP/4/98

RO/OP/4

SGLK85

90.5

142.8


In terms of latex yield, 616 rubber accessions from sub-regions of Rondonia state (Brazil) were capable of producing latex, corresponding to 75% of the 821 accessions evaluated in 8 experiments. The results of the analysis of variance (ANOVA) showed that the latex yield between accessions in the experiments had a significant difference with a probability of P ≤ 0.001 and between groups of accessions from the experiments also had a significant difference with a probability of P ≤ 0.01 (Appendix 11); therefore, the latex yield of accessions in the experiments and between groups of accessions from the experiments was not uniform, so the latex yield data were included in the analysis according to the normal distribution method using the λ 2 test .

The results of the analysis using the multiple-choice test (λ 2 ) obtained in Table 3.23 and Figure 3.12 showed that most of the latex productivity of the samples in the experiments followed the distribution rule with the frequency completely skewed towards one side of low latex productivity and had a significant difference with a probability from P ≤ 0.05 to P ≤ 0.001; the level of variation between the samples in the experiments was very large, reaching from 56% to 124%. However, the samples in the two experiments SGLK96 and SGLK05 did not have a significant difference, but the samples still followed the distribution rule with the frequency of samples skewed towards one side of low latex productivity. Therefore, the average value cannot represent the latex yield of the experimental samples, the average latex yield in the experiments fluctuated from 5.0 g to 16.1 g/c/c with a difference of 3.4 g to 10.4 g/c/c. Similarly, the results presented in Table 3.23 and Figure 3.13 showed that the latex yield characteristics of 616 samples from 8 experiments also followed the general distribution rule with the frequency of samples completely skewed to one side of low latex yield and the difference was very significant at the confidence level P ≤ 0.001; the average latex yield reached 7.9 g/c/c with a difference of 7.1 g and the variation between samples was very large reaching 89.8%, so the average value did not represent the latex yield of the samples. Wild rubber varieties originating from Rondonia state (Brazil) evaluated in experiments mostly had very low latex yield compared to the GT1 control, a clone from Wickham's genetic source. The results in Table 3.24 identified 31 varieties with the best 4-year average latex yield in experiments according to the selection ratio.


Filtered at 5%, the average latex yield over 4 years was from 13.4 g to 63.9 g/c/c, equivalent to 53.1% to 161.2% compared to the GT1 control clone; of which, 7 varieties had very high latex yield, equal to and exceeding 61% compared to the GT1 control clone but only accounted for 1% of the total 616 varieties evaluated.

In general, the wild rubber tree genetic resources from Rondonia state (Brazil) have very low latex yield compared to the clones from Wickham's genetic resources; the distribution characteristics of latex yield of the experimental samples as well as all 616 samples of 8 experiments follow the same general distribution rule with the frequency of samples completely skewed to one side of low latex yield and the difference is very significant, so the average value does not represent the latex yield of the experimental samples, the number of samples with the highest latex yield was determined to include 31 samples and these are very valuable samples for the purpose of growing wood-latex rubber.

Table 3.23 Testing the distribution rule by multiple choice test (λ 2 ) on latex yield of rubber varieties originating from Rondonia state on experiments




Average latex yield 4 years (g/cm/cm)


Experiment

Number of samples


Medium


Smallest


Biggest

Standard deviation (S)

Coefficient of variation (CV%)

Multiple choice (λ 2 )

SGLK85

276

5.0

1.2

30.3

3.4

68.6

53.1 ***

SGLK91

35

7.3

1.5

45.0

9.0

123.9

7.98 **

SGLK94

71

6.0

1.3

28.5

5.0

82.7

6.39 **

SGLK96

33

8.8

2.3

30.9

5.6

64.2

2.43 NS

SGLK03

52

7.7

1.9

38.5

6.7

87.4

6.60 **

SGLK04

48

16.1

3.7

63.9

10.4

64.7

4.45 *

SGLK05

61

14.1

1.3

40.6

7.8

55.5

3.00 NS

SGLK06

40

12.4

4.4

35.9

7.4

59.7

6.52 **

Total

616

7.9

1.2

63.9

7.1

89.8

195.5 ***

NS is a non-significant difference with probability P > 0.05; a significant difference with probability P ≤ 0.05*, P ≤ 0.01** and P ≤ 0.001***.


Figure 3.12 Frequency distribution of the 4-year average latex yield of the varieties originating from Rondonia state (Brazil) evaluated in the experiments


fi(%)















































































30


25


20


15


10


5


0

0 5 10 15 20 25 30 35 40 45 50 55 60 65


g/c/c


Figure 3.13 Frequency distribution of the average 4-year latex yield of 616 rubber accessions originating from Rondonia state (Brazil)

Table 3.24 Varieties with the highest average latex yield over 4 years in experiments at a selection rate of 5%


Breed group

Experiment

Average latex yield 4 years

Specimen

g/c/c

Compared with control GT1 (%)

RO/A/7/15

RO/A/7

SGLK96

30.9

74.3

RO/A/7/298

RO/A/7

SGLK06

32.5

84.7

RO/A/7/307

RO/A/7

SGLK05

24.7

58.8

RO/A/7/75C

RO/A/7

SGLK03

18.3

58.9

RO/C/8/163

RO/C/8

SGLK85

30.3

120.1

RO/C/8/272

RO/C/8

SGLK85

16.9

67.0

RO/C/8/76

RO/C/8

SGLK94

27.7

88.8

RO/C/9/117

RO/C/9

SGLK94

16.7

53.5

RO/C/9/20C

RO/C/9

SGLK05

40.6

96.7

RO/C/9/398

RO/C/9

SGLK05

30.0

71.6

RO/C/9/51C

RO/C/9

SGLK03

27.5

88.3

RO/C/9/72

RO/C/9

SGLK85

13.4

53.1

RO/CM/10/481

RO/CM/10

SGLK04

25.6

64.7


Table 3.24 The varieties with the highest average latex yield over 4 years in experiments with a selection ratio of 5% (cont.)


Breed group

Experiment

Average latex yield 4 years

Specimen

g/c/c

Compared with control GT1 (%)

RO/CM/11/452

RO/CM/11

SGLK04

46.4

117.2

RO/CM/11/6

RO/CM/11

SGLK85

19.4

76.9

RO/CM/12/26

RO/CM/12

SGLK91

45.0

152.9

RO/CM/12/54

RO/CM/12

SGLK91

35.5

120.7

RO/J/5/3C

RO/J/5

SGLK04

28.6

72.2

RO/J/5/42

RO/J/5

SGLK04

31.5

79.6

RO/J/5/44

RO/J/5

SGLK06

22.5

58.6

RO/JP/3/210

RO/JP/3

SGLK06

35.9

93.6

RO/JP/3/24C

RO/JP/3

SGLK03

21.8

69.9

RO/JP/3/334

RO/JP/3

SGLK04

63.9

161.2

RO/JP/3/37C

RO/JP/3

SGLK05

40.2

95.8

RO/JP/3/473

RO/JP/3

SGLK91

17.3

58.6

RO/JP/3/495

RO/JP/3

SGLK85

14.1

55.8

RO/JP/3/61C

RO/JP/3

SGLK03

38.5

123.7

RO/JP/3/73C

RO/JP/3

SGLK05

26.3

62.6

RO/OP/4/100

RO/OP/4

SGLK06

27.2

71.0

RO/OP/4/131

RO/OP/4

SGLK94

28.5

91.5

RO/OP/4/23C

RO/OP/4

SGLK06

27.3

71.1


Comparison of the agronomic value of wild rubber tree genetic resources from Rondonia state (Brazil) conserved in Vietnam with other genetic resources originating from the Amazon basin was evaluated on small-scale experiments in many different countries. The latex yield of wild sources all had very low latex yield, the average latex yield after 4 years was only 32.5% compared to the popular clone RRIM 600 in Thailand (RRIT, 2002) and the average after 3 years of 379 accessions was 25.2% compared to the clone GT 1 in Ivory Coast (Clement-Demange et al., 2002). Evaluation on


In the IRRDB'81 germplasm in Malaysia and Indonesia, the average 8-year latex yield of all cultivar groups from the IRRDB'81 germplasm was lower than that of the Wickham clones, but the germplasm from Rondonia state gave higher latex yield than the germplasm from Acre and Mato Grosso states (Aidi et al., 2002; Ramli et al., 2004); in China, the latex yield of the IRRDB'81 germplasm was only 15.1% - 88.7% compared to the RRIM 600 clone (Hu et al., 2005).

The potential of the rubber germplasm collection was most recently collected in 1995 by the Rubber Research Institute of Malaysia (RRIM) in the state of Amazonas, Brazil. The results of agronomic evaluation of the accessions of 6 species of the genus Hevea in this collection showed that most of the accessions had low latex yield, 81% of the accessions had latex yield lower than 25 g/c/c; however, all agronomic traits of H. brasiliensis were superior to the other 5 species of the genus Hevea , the evaluation of the agronomic characteristics of this genepool is very important to select potential accessions as well as to preserve genetic variation; In addition, the 1995 genetic source has almost good disease resistance, so this new source of material is very valuable for improving varieties and breeding rubber - latex in Malaysia (Adifaiz et al., 2018).

In addition, the evaluation of the IRRDB'81 genetic resources in Africa showed that latex yield had a large variation and the intrinsic nature of the accessions accounted for 81% of the total variation (Clement-Demange et al., 1997); Nkengafac and Nkumbe (2021), analysis of leaf phenotype of accessions from the IRAD Ekona (Cameroon) gene pool collection of 36 accessions showed that all leaf characteristics were different; the proportion of variable components accounted for 88% of the total variation and the accessions were divided into 6 genetic clusters; therefore, research on leaf morphology will also contribute to the assessment of genetic diversity and the expansion of the genetic pool in breeding programs. Similarly, in Vietnam, the IRRDB'81 genetic resource also recorded variation due to the samples themselves with a rate of 83% to 96% and the study suggested that the large variation contributed to enriching the genetic resource and

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