4.3.5 Stress Tolerance Index among Generation
The plant height of all generation was increased from normal condition to stagnant flooding stress. It was indicating that all generation response to water
increasing by stem elongation. Number of productive tiller and grain yield also were decreased from normal to stagnant flooding condition in all generations. Response
of panicle length and weight of 100 grain were varied among the generations.
The STI of F1 was higher than superior parent indicating the presence of over dominant gene action in plant height, panicle length, and grain weight per
plant. Meanwhile, the STI of F1 was higher than mid-parent indicating heterotic in number of productive tiller and weight of 100 grain.
40 Table 4.9 Mean and stress tolerance index STI of P1, P2, F1, F2, BCP1, and BCP2 of rice generation
Generation Plant height cm
No of tiller Panicle length cm
100 grains weight g Grain yield g
Normal SF
STI Normal
SF STI Normal
SF STI Normal
SF STI
Normal SF
STI P1
117 143 1.06
19 11 0.64
24.3 25.2 0.93
2.1 2.34
0.77 14.50
7.33 0.24
P2 129
145 1.18 18
11 0.59 25.7
25.5 1.00 2.83
2.78 1.23
18.15 9.31
0.39 F1
128 150 1.21
18 8
0.43 26.5
25 1.01
2.53 2.63
1.05 29.98
15.61 1.07 F2
125 141 1.11
17 10 0.53
25.6 26.9 1.05
2.49 2.59
1.01 18.86
9.61 0.42
BCP1 126
142 1.12 20
9 0.52
25.9 26.7 1.05
2.45 2.37
0.92 25.52
11.13 0.65 BCP2
130 143 1.18
17 6
0.32 26.0
26.6 1.05 2.73
2.67 1.15
18.36 11.35 0.48
41
4.3.6 Heritability
Broad-sense heritability in stagnant flooding stress was lower than in controlled condition for all traits observed except panicle length. Broad-sense
heritability under stagnant flooding was ranged 0.28 to 0.86, while it was ranged 0.26 to 0.91 under normal condition. Narrow-sense heritability was ranged 0.01 to
0.86 in stagnant flooding stress, and was ranged 0.04 to 0.91 in normal condition. Greater differences between broad and narrow heritability indicating that
environment did influence the genetic variance of the parents and offspring. Lower heritability in the stressed condition also indicating that variation of environment
was greater than normal condition. This phenomenon was also reported in rice traits under iron toxicity Nugraha, 2016, soybean in acidic acid Kuswantoro et al.
2011, and wheat in drought condition Said 2014. Table 4.10 Heritability estimates of some traits of rice under stagnant flooding and
normal condition
Heritability Plant height
No tiller
Panicle length
100 grain weight
Grain yield Stagnant flooding
h
2 bs
0.65 0.51
0.28 0.86
0.51 h
2 ns
0.57 0.09
0.17 0.86
0.01 Normal condition
h
2 bs
0.79 0.65
0.26 0.91
0.78 h
2 ns
0.71 0.56
0.26 0.91
0.60
4.3.7 Correlation of F
2
population
Simple correlation analysis in F2 population showed that plant height was correlated with number of productive tillers and number of filled grain under
stagnant flooding stress. Plant height was only correlated with number of productive tiller in the control site. Grain yield was correlated with weight of 100
grain, number of filled and unfilled grain per panicle under stagnant flooding stress. In normal condition, grain weight per plant was correlated with number of
productive tiller, flowering date, panicle length, weight of 100 grain, and number of filled grain. Negative coefficient of correlation means that the traits have
opposite correlation. Number of filled grain also was positively correlated with panicle length under both of stagnant flooding and normal condition. Meanwhile
number of unfilled grain was negatively correlated with other traits under stagnant flooding and normal condition.
42 Table 4.11 Simple correlation among traits in F2 rice population under stagnant
flooding stress and normal condition
Character PH
PT F50
PL W100
FG UFG
GY PH
1 0.3336 0.068
0.044 0.009 -0.1431
0.078 -0.012
PT 0.284
1 -0.024
-0.042 -0.045
-0.088 -0.026
0.107 F50
-0.018 -0.034
1 0.054
-0.026 -0.023
0.097 -0.046
PL 0.094
0.078 -0.020
1 0.018
0.294 0.106
-0.095 W100
0.050 0.061
-0.175 0.099
1 0.022
-0.189 -0.131
FG -0.046
0.034 0.056
0.200 0.043
1 -0.300
0.166 UNFG
-0.037 -0.178
0.024 -0.134
-0.012 -0.235
1 -0.221 GY
0.076 0.283
-0.040 0.144
0.249 0.410
-0.260 1
Abbreviation: PH, plant height; PT, number of tiller; F50, flowering time; PL, panicle length; W100, weight of 100 grain; FG, number of filled grain; UFG, number of unfelled grain; GY, grain weight
per plant. The r coefficient above are in stagnant flooding stress, and r coefficient under are in normal condition
4.4 Conclusion
The grain yield and its components did not fit to additive-dominant model indicating the presence of non-allelic interaction. Joint scaling test with six
parameter revealed duplicate epistasis were fitted to explain gene action model. Heritability estimates under stress condition were lower compared to those under
normal condition. Suggested strategies for breeding program for improving grain yield under stagnant flooding stress are: 1 delaying selection for several
generations until high level of gene fixation was attained, and 2 involvement of a shuttle breeding approach between stress and optimum environment.
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