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Yearly Variation of Genetic Parameters for Panicle Characters of Japonica Rice (Oryza sativa L.)

Myung Kyu Oh1 , Bo Kyeong Kim2, Mun Sik Shin2, Jin Choung2, Ki Young Kim2, Jong Cheol Ko2, Jae Kweon Ko2, Jae Kil Lee2 and Im Soo Choi1

1National Institute of Crop Science, www.nces.go.kr Email ohmk31@rda.go.kr
2
Honam Agricultural Research Institute, www.nhaes.go.kr Email kimbke@rda.go.kr

Abstract

This study aims to determine the effect of nitrogen level and year on variation for panicle traits in rice. It also aims to examine the desirable panicle structure for rice to ripen better and yield more. Four different panicle types of rice varieties were transplanted under two different nitrogen levels in 2002 and 2003. There were more primary rachis branches (PRBs) per panicle and grains set on Sindongjinbyeo and Iksan#467, but secondary rachis branches (SRBs) per PRB was fewer than in Dongjin#1 and Saegyehwa. Variety year interaction was significant for PRBs and SRBs per panicle. The yearly variation of the number of PRBs per panicle and grains setting on PRB per panicle was not large. The pathway coefficient of panicle characters was not only greatly different with year. The number of PRB per panicle, the number of grains setting on PRB per panicle, and the number of grains setting on SRB simultaneously increased both ripened grain ratio and rice yield. SRB per PRB and grains setting on SRB per PRB decreased ripened grain ratio, although it didn’t decrease rice yield.

Media summary

The yearly variation of the number of PRB per panicle and grains setting on PRB per panicle were not large. The number of PRB per panicle, the number of grains setting on PRB per panicle, and the number of grains setting on SRB simultaneously increased both ripened grain ratio and rice yield. Meanwhile, SRB per PRB and grains setting on SRB per PRB decreased ripened grain ratio, although it didn’t decrease rice yield.

Key Words

Rice, Rachis branch, Panicle type, Ripened grain ratio

Introduction

The large sink size of recent high-yielding rice varieties mainly results from the increased spikelet number setting on secondary rachis branches (SRBs) per panicle. As such, this generally leads to low ratio of completely matured grain. Therefore, tested varieties did not yield as high in potential as expected (Kim et al., 1999). Specifically, the increased spikelet number caused defects such as low ripened grain ratio, regional variation of ripened grain ratio, and eventually unstable rice yield (Takeda et al., 1987; Wang et al., 1997). These results were not caused by independent effect of each yield component, but by the mutual compensatory or contradictory effect among yield components on rice yield. This study explains the stable genetic parameters related to panicle traits, after being subjected to different nitrogen levels within two years.

Methods

Four rice varieties were used for the study: Sindongjinbyeo and Iksan#467, medium large grain; Dongjin#1 and Saegyehwa, with panicle characteristics opposite to the former two. All varieties were transplanted at two different nitrogen levels, and planting densities levels with three seedlings per hill on May 30th of 2002 and 2003. The experiment plots were laid out with split- split design consisting of two nitrogen levels of N110 and N220 as main plots, two planting densities of 3015cm and 1515cm as subplots, and four rice varieties as sub-subplots in three replications.

Results and discussion

Among the genetic parameters related to panicle traits, within two years, year as a source of variation was not significant for PRBs and SRP but variety year was not significant. Also, the yearly variation for the number of primary rachis branch (PRB) per panicle and grains setting on PRB per panicle was not large. Results show that ripened grain ratio was affected by PRB and SRB factors. Therefore, increasing the yielding potential of variety needs more number of primary rachis branches per panicle.

Table 1. Mean squares for PRB, SRB and grains setting on PRB or SRB per panicle across two nitrogen levels and two planting densities.

Source

df

Year 2002

Year 2003

NPRB P1)

NSRB P2)

NGSP 3)

NGSS 4)

NPRBP

NSRBP

NGSP

NGSS

Replication

2

0.241

9.765

22.609

1.281

2.371

104.1

21.09

186.4

Nitrogen levels (NL)

1

0.200ns

51.252 ns

0.390 ns

46.81 ns

0.333 ns

11.11 ns

16.33 ns

242.5 ns

Error

2

0.176

8.285

12.42

112.1

5.102

1.184

1.282

13.84

Planting density (PD)

1

20.67**

55.47 ns

999.1**

231.7 ns

13.23**

563.7**

305.0**

2722.5**

NLPD

1

0.174*

4.947 ns

2.890*

0.416ns

0.140 ns

9.989 ns

2.248 ns

18.36 ns

Error

4

1.985

10.64

0.326

109.6

0.102

7.494

3.167

31.09

Variety (VAR)

3

1.986**

254.3**

223.5**

3878.8**

2.701**

228.9**

101.9**

1595.7**

NLVAR

3

0.414 ns

5.922 ns

27.47 ns

47.59 ns

5.371 ns

0.437 ns

1.253 ns

15.41 ns

PDVAR

3

1.491 ns

1.082 ns

6.067 ns

15.68 ns

0.148 ns

9.597 ns

1.620 ns

37.68 ns

NLPDVAR

3

0.101 ns

1.802 ns

21.57 ns

11.85 ns

0.394 ns

14.10 ns

4.225 ns

34.98 ns

Error

24

0.361

9.552

13.99

88.37

0.193

11.61

3.512

34.78

1) Number of primary rachis branch per panicle, 2) Number of secondary rachis branch per panicle, 3) Number of grain setting on PRB, 4) Number of grain setting on SRB, *, **Significa nt at the 5% and 1% probability level, respectively.

References

Kim BK, Ko JC, Shin MS, Ko JK and Kang HK (1999). Analysis of yield and its associated characters affected by planting density and fertilizer level in heavy-panicle Japonica rice. Korean J. Breed. 31(1): 21-28.

Takeda K, Saito K, Yamazaki T and Mikami T (1987). Environmental response of yielding capacity in isogenic lines for grain size in rice. Jpn. L. Breed. 37: 309-317.

Wang Y, Kuroda E, Hirano M and Murata T (1997). Analysis of high yielding mechanism of rice varieties belong to different plant types. Comparison of growth and yield characteristics and dry matter production. Jpn. J. Crop Sci. 66(2): 293-299.

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