Changes in the Panicle-Related Traits of Different Rice Cultivars under High Temperature Condition  

Young-Jun Mo1*, Ki-Young Kim1, Hyun-su Park, Jong-Cheol Ko1, Woon-Chul Shin1, Jeong-Kwon Nam1, Bo-Kyeong Kim1, Jae-Kwon Ko1

1Department of Rice and Winter Cereal Crop, National Institute of Crop Science, Rural Development Administration, Iksan 570-080, Korea

Temperature rise by global warming causes deterioration in rice yield and grain quality. This study was conducted to investigate the changes in rice panicle-related traits under the high temperature condition.

Objective

z Values with a different letter are significantly different at P < 0.05.

A total of 40 Korean rice cultivars including 27 japonica and 13 Tongil-type (japonica-indica cross) were cultivated in two plots in the field. Eight weeks after transplanting, a greenhouse was set over one plot for high temperature treatment. Plants were harvested upon maturity and 13 panicle-related traits were investigated.

Materials and Methods

Group (n)

DateAccumulated temp. during the

treatment (°C) (average temp.) Seeding

(transplanting)Treatment

HarvestAmbient

(a) Treatment

(b) b - a

Ⅰ (5)

Apr 30(May 29)

Jul 24

Sep 111216.4(24.4)

1275.8(25.5)

59.4(1.1)

Ⅱ (9) Sep 281546.3(23.1)

1634.4(24.4)

88.1(1.3)

Ⅲ (12) Oct 51671.3(22.6)

1773.9(24.0)

102.6(1.4)

Ⅳ (14) Oct 121775.8(21.9)

1893.7(23.4)

117.9(1.5)

Table 1. Accumulated and average temperatures in the field and the greenhouse conditions during the high temperature treatment.

Variables Traitsx1 Number of spikelets per paniclex2 Number of rachis-branches per paniclex3 Number of primariy rachis-branches (PRBs) per paniclex4 Number of spikelets on PRBs per paniclex5 Mean number of spikelets on a PRBx6 Number of secondary rachis-branches (SRBs) per paniclex7 Number of spikelets on SRBs per paniclex8 Mean number of spikelets on a SRBx9 Ratio of SRBs to PRBs

x10 Percent ripened grain of PRBsx11 Percent ripened grain of SRBsx12 Percent ripened grain per paniclex13 Head rice percentage

Table 2. Panicle-related traits investigated in this study.

Results

Ecotype(n)

x1 x2 x3 x4 x5 x6 x7

japonica(27)

145.4az

(102~183)37.8a

(26~50)11.3a(9~14)

65a(53~77)

5.8a(5.5~6.0)

26.6a(17~36)

80.4a(49~111)

Tongil(13)

188.8b(149~217)

48.4b(36~59)

11.5a(10~15)

62.1b(49~78)

5.4b(4.7~5.9)

36.9b(25.3~48)

126.7b(87~158)

Total(40)

159.5(102~217)

41.3(26~59)

11.3(9~15)

64.1(49~78)

5.7(4.7~6.0)

29.9(17~48)

95.5(49~158)

Ecotype x8 x9 x10 x11 x12 x13

japonica3.0a

(2.7~3.3)2.3a

(1.6~3.0)96.5a

(93.8~98.8)94.0a

(87.9~97.4)95.1a

(90.6~97.9)90.5a

(67.3~96.5)

Tongil3.4b

(3.0~3.8)3.2b

(2.3~4.2)91.7b

(86.4~96.1)90.6b

(84.6~96.1)90.9b

(86.2~95.9)77.9b

(62.1~90.9)

Total3.2

(2.7~3.8)2.6

(1.6~4.2)95.0

(86.4~98.8)92.9

(84.6~97.4)93.8

(86.2~97.9)86.4

(62.1~96.5)

Table 3. Average and range of the panicle-related traits of 40 rice varieties in ambient condition.

TraitEigenvector

Prin1* Prin2x1 0.35 0.2x2 0.35 0.2x3 0.15 0.55x4 0.03 0.58x5 -0.27 0.1x6 0.35 0.13x7 0.36 0.07x8 0.24 -0.12x9 0.34 -0.09x10 -0.26 0.23x11 -0.24 0.2x12 -0.28 0.25x13 -0.16 0.27Eigenvalue 7.18 2.52Contributaion (%) 55.2 19.4Cumulative contribution (%)

55.2 74.6

Fig. 1. Cluster analysis of 40 rice varieties based on the panicle-related traits in ambient condition.

Fig. 2. Principal component analysis of the 13 panicle-related traits from 40 rice varieties in ambient condition. Three groups show clusters designated in Fig. 1. Prin1 and Prin2 indicate the first and second principal components, respectively.

x2 x3 x4 x5 x6 x7 x8 x9 x10 x11 x12 x13x1 0.97** 0.61** 0.42** -0.36** 0.96** 0.97** 0.58** 0.80** -0.30** -0.30** -0.38** -0.21

x2 0.59** 0.37** -0.46** 0.99** 0.95** 0.42** 0.85** -0.27** -0.32** -0.38** -0.20

x3 0.90** -0.13* 0.47** 0.42** 0.08 0.09 -0.03 -0.02 -0.02 0.10

x4 0.31** 0.25** 0.20** -0.05 -0.13* 0.07 0.05 0.09 0.26*

x5 -0.48** -0.48** -0.25** -0.51** 0.21** 0.17** 0.26** 0.34**

x6 0.97** 0.44** 0.91** -0.29** -0.34** -0.41** -0.23*

x7 0.64** 0.90** -0.34** -0.34** -0.44** -0.30**

x8 0.46** -0.33** -0.19** -0.32** -0.36**

x9 -0.32** -0.40** -0.48** -0.29**

x10 0.37** 0.74** 0.20

x11 0.89** 0.15

x12 0.21

Table 4. Correlation coefficients among the panicle-related traits in ambient condition.

* and ** indicate significance at P < 0.05 and P < 0.01, respectively ..

Ecotype(n)

x1 x2 x3 x4 x5 x6 x7

japonica(27)

151.3az

(111~222)39.4a

(27~57)11.3a(9~14)

65.5a(50~83)

5.8a(5.5~6.1)

28.1a(17~44)

85.8a(51.8~145.5)

Tongil(13)

207.4b(154~258)

52.6b(37~67)

11.9b(10~16)

65.4a(46~88)

5.5b(4.5~6.1)

40.7b(27~55)

142.0b(92~195.7)

Total(40)

169.5(111~258)

43.7(27~67)

11.5(9~16)

65.5(46~88)

5.7(4.5~6.1)

32.2(17~55)

104.1(51.8~195.7)

Ecotype x8 x9 x10 x11 x12 x13

japonica3.0a

(2.7~3.3)2.5a

(1.8~3.4)94.7a

(88.4~98.3)90.6a

(82.8~99)92.4a

(85.8~98.6)76.8a

(62.2~87.1)

Tongil3.5b

(3~3.7)3.5b

(2.2~4.6)85.2b

(71.4~93.5)80.0b

(69.7~90.9)81.6b

(72.5~91.9)71.9b

(50.2~86.4)

Total3.2

(2.7~3.7)2.8

(1.8~4.6)91.6

(71.4~98.3)87.2

(69.7~99)88.9

(72.5~98.6)75.2

(50.2~87.1)

Table 5. Average and range of the panicle-related traits of 40 rice varieties in high temperature condition.

z Values with a different letter are significantly different at P < 0.05.

Fig. 3. Cluster analysis of 40 rice varieties based on the panicle-related traits in high temperature condition.

TraitEigenvector

Prin1 Prin2x1 0.35 0.19x2 0.35 0.15x3 0.16 0.57x4 0.08 0.61x5 -0.21 0.16x6 0.35 0.07x7 0.36 0.05x8 0.28 -0.04x9 0.32 -0.18

x10 -0.25 0.3x11 -0.29 0.16x12 -0.29 0.22x13 -0.1 0.12

Eigenvalue 7.17 2.25Contributaion (%) 55.1 17.3

Cumulative contribution (%)

55.1 72.5

Fig. 4. Principal component analysis of the 13 panicle-related traits from 40 rice varieties in high temperature condition. Three groups show clusters designated in Fig. 3. Prin1 and Prin2 indicate the first and second principal components, respectively.

x2 x3 x4 x5 x6 x7 x8 x9 x10 x11 x12 x13x1 0.97** 0.57** 0.45** -0.28** 0.96** 0.97** 0.69** 0.76** -0.29** -0.44** -0.44** -0.14

x2 0.54** 0.37** -0.42** 0.99** 0.96** 0.55** 0.82** -0.28** -0.41** -0.42** -0.18

x3 0.93** -0.11 0.41** 0.37** 0.14* -0.03 0.02 -0.12 -0.07 -0.04

x4 0.27** 0.24** 0.22** 0.08 -0.19** 0.07 -0.04 0.01 0.07

x5 -0.43** -0.38** -0.11 -0.46** 0.16* 0.18** 0.20** 0.30**

x6 0.98** 0.57** 0.89** -0.30** -0.42** -0.44** -0.19

x7 0.72** 0.88** -0.33** -0.46** -0.49** -0.17

x8 0.55** -0.35** -0.45** -0.48** -0.10

x9 -0.35** -0.41** -0.46** -0.18

x10 0.72** 0.88** 0.13

x11 0.96** 0.14

x12 0.16

Table 6. Correlation coefficients among the panicle-related traits in high temperature condition.

Conclusion

In both conditions, Tongil-type showed higher sink size-related characters than japonica, while japonica had higher percent ripened grain and percentage of head rice than Tongil-type. The number of SRBs per panicle and the number of spikelets on SRBs per panicle were positively correlated with the numbers of spikelets and rachis-branches per panicle (r > 0.95) while negatively correlated with the percent ripened grain (r < -0.40). On ecotype level, numbers of spikelets and rachis-branches per panicle, the number of SRBs per panicle, and the number of spikelets on SRBs per panicle were significantly increased in Tongil-type under the high temperature condition, while those in japonica did not show any significant change. Decrease in the percent ripened grain was more severe in the spikelets on SRBs than PRBs in both ecotypes and Tongil-type showed significantly higher decrease in the percent ripened grain than japonica. Therefore, it is concluded that the sink size of Tongil-type cultivars were increased under the high temperature more than japonica cultivars by the significant increase in SRBs, which caused more severe reduction in percent ripened grain.

* and ** indicate significance at P < 0.05 and P < 0.01, respectively ..

* Corresponding author: Tel. 82-63-840-2158 E-mail: moyj82@korea.kr