Breeding of Rice Variety(s) for High Yielding and Early Maturity Through aWide Cross and Mutation
Sobrizal
National Nuclear Energy Agency, Center for the Application of Isotopes and Radiation,
Jl. Cinere Pasar Jumat P. O. Box 7002 JKSKL, Jakarta 12070 Indonesia.
Abstract
To fulfill the Indonesian domestic demand in which the annual population growth isstill more than 1.4%, Indonesian rice production should be increased. This can beachieved by increasing rice productivity and harvesting index through growing highyielding and early maturity of rice varieties. In previous research, breeding lines thathave wide genetic diversity have been constructed through Indica-Japonica cross of
IR36/Koshihikari. To gather the desirable characters in one lines some of breeding lines
were crossed each other and some improved lines were obtained. To remove undesirable
characters in improved lines some of these limes were irradiated by gamma ray and 12
promising mutant lines with high yield and early maturities were selected. The growthdurations of these mutant lines were ranging from 93.7 to 99.3 days from sowing toharvesting, significantly shorter than those of original line SKI 88, national leading
variety Ciherang and the early maturity national leading variety INPARI 13. Yield of
most mutant lines were not significantly difference with that of original line, SKI 88
and national leading variety, Ciherang, but significantly higher than that of INPARI 13.
To fulfill the requirement of variety release in Indonesia, other multi-location yieldtrials and other examinations such as pests, diseases as well as other grain quality
examinations should be conducted.
Key words: rice, high yield, early maturity, wide cross, mutation

Introduction
Rice is a staple food of majority Indonesian population. In the mid-1980s Indonesia
firstly achieved self-sufficiency for rice, however the growth of rice production has
slowed down since the 1990s (BAPENAS, 2002). The decline in rice production isfrequently attributed to loss of rice fields caused by conversion to non-agricultural uses,
11and to the declining productivity. To fulfill the domestic demand in which the annual
population growth is still more than 1.4 %, Indonesian rice production should beincreased. This can be achieved by increasing rice productivity and harvesting index
through growing high yielding and early maturity of rice varieties.
Since the release of IR8 varieties in 1966 (Cantrell and Hettel, 2004), the potential
for paddy production has not been significantly increased (Sobrizal and Ismachin, 2006).
The formation of new varieties is only able to maintain the potential of IR8 by
improving the growth duration, grain quality, and its adaptability to environmental
stress. The narrowness of the genetic diversity of the released rice varieties contributes
to the occurrence of slowed down of growth yield potential. Many released rice varieties
are related to each other, so the diversity is less and yield potentials are almost same(Susanto et al., 2003). In 1982 the national average production was 4.04 t / ha, while in2016 it was 5.24 t / ha (BPS, 2017), so the 34-year increase was only 1.20 t / ha. In order
to increase the yield potential for future, different genetic resources are needed in thenew varieties assembly program.
In previous research, breeding lines that have wide genetic diversity have been
constructed through Indica-Japonica cross of IR36/Koshihikari (Sobrizal, 2008). Intra
sub-specific crossing with large genetic distances between the two parents allow for theoccurrence of transgressive segregation so that it will produce a progeny with arelatively large genetic diversity. Transgressive segregation is the emergence of anindividual in a segregated population in which the individual phenotype exceeds that ofboth parental phenotypes and is commonly found in progeny derived from inter andintra-specific crosses (Vega and Frey, 2004). Great genetic diversity will provide
flexibility in selection, including selection towards increased yield potential. The
selected plants are purified to become pure lines, and can be used as breeding materials
in subsequent breeding programs. By using these unique germplasms as well as
mutations 12 rice promising lines with high yield and early maturities have been
constructed. The objective of this research is to develop high yielding and earlymaturities of rice varieties.
Materials and Methods
Construction of Breeding Materials
To increase the genetic variability of breeding materials, IR36 and Koshihikari
were crossed, and developing of pure lines from this cross was conducted as described inSobrizal 2013. To gather desirable characters in a line some of selected pure lines were12

crossed as shown in Fig. 1. From these crosses selected pure lines (SKI 64, SKI 88, SKI
153, and SKI 276) were used as further breeding materials. These lines showed good
performance with high yield potency, but long growth durations. To reduce their growthdurations, 50 gram seeds of each line were irradiated by 200 Gy of gamma ray at Centerfor the Application of Isotopes and Radiation Technology, Pasar Jumat, Jakarta.
Irradiated M1 seeds were sown, and twenty day-old seedlings were transplanted topaddy field by planting a single seedling per hole at experimental field, Sawangan,
Depok with 20 cm spacing between plants.
Five hundred M1 plants were harvested individually to obtain the M2 seeds.
Harvesting was conducted by collecting only one main panicle in each M1 plant. M2
seeds were sown, and 20 M2 plants derived from each M1 plant were transplanted todevelop M2 lines. Selections of early maturity plants were conducted in each M2 lines
and selected plants were harvested individually.
Selected early maturity plants were purified up to M5 generations, then, selected
pure lines were designated as RSKI #. RSKI lines were subjected to yield trials.
Breeding scheme of plant materials used in this study can be shown in Fig. 1.

Fig. 1. Breeding scheme of plant materials used in this study.
Yield trials
Yield trials were conducted using 12 selected early maturity mutant lines, checkvarieties of original line SKI 88, national leading variety Ciherang and national leading
early maturity variety INPARI 13. Seedlings were transplanted to plot with plot size of4 x 5 m and planting spacing of 25 x 25 cm. Experiments were arranged in RBD with 3replications.

13Results and Discussion
In this study, all the F1 plants derived from crosses of KI lines as in Fig. 1 grew welland selection was conducted in F2 population with emphasis on agronomical characters.
Selected plants were purified and selected pure lines were designated as SKI #. Among
selected pure lines, the seeds of SKI 64, SKI 88, SKI 153, and SKI 276 lines wereirradiated by 200 Gy of gamma ray. As much as 500 M1 plants were harvested
individually to obtain M2 seeds. Selection for early maturity was conducted in M2 lines
and 105 selected lines were purified up to M6 generations. From field observation of 105
lines in rainy growing season of 2012/2013, 12 homogeneous early maturity M7 mutantlines were selected. These lines were evaluated for yield performance at Pusakanagara
Experimental Farm in dry growing season of 2013 and wet growing season of 2013/2014.
The results were shown in Table 1.
Table 1. Growth duration and yield of lines/varieties tested.

*) The numbers followed by different characters are significantly different for 5% level.

Table 1 showed that growth durations of mutant lines were ranging from 93.7 to99.3 days from sowing to harvesting. They were significantly shorter than growthdurations of original line SKI 88, national leading variety Ciherang and the earlymaturity national leading variety INPARI 13. The growth duration of SKI 88 was 117.3
days, Ciherang was 118.7 days and INPARI 13 was 103.7 days.
14

Yield of mutant lines were ranging from 7.83 to 9.79 t/ha, while SKI 88 was 9.61
ton/ha, Ciherang was 9.45 ton/ha and INPARI 13 was 8.16 t/ha. The yields of tenmutant lines (RSKI 64-1, RSKI 64-2, RSKI 88-1, RSKI 88-2, RSKI 88-3, RSKI 88-4,
RSKI 88-5, RSKI 88-7, RSKI 153-1, RSKI 276-1, RSKI 276-2) were not significantly
difference with that of original line, SKI 88 and national leading variety, Ciherang, but
significantly higher than that of INPARI 13. More over the growth durations of theseten mutant lines were significantly shorter than that of the national leading earlymaturity, INPARI 13. Performance of mutant RSKI 88-7 and its original plant SKI 88
shown in Fig. 2. Figure 2 shows that the panicles of mutant plants of RSKI 88-7 haveappeared while its original plant of SKI 88 has not appeared yet.

Fig. 2. Comparison of early maturity mutant line of RSKI 88-7 and its original line ofSKI 88.
To confirm the performance of growth duration and yield of selected lines, theselines were evaluated by growing them at farmer field in Musi Rawas District, South
Sumatera and the result sown in Table 2. Table 2 showed that the growth duration of all
selected early maturity lines were significantly shorter than that of original line andCiherang. Even all selected lines were significantly earlier than national early maturity
variety INPARI 13. The yields of some selected early maturity lines (RSKI 64-2, RSKI88-1, RSKI 88-3, RSKI 88-5, RSKI 153-1, RSKI 276-1) were not significantly different
15

from that of national leading early maturity variety INPARI 13. The yields of otherselected early maturity lines were significantly lower than that of national leading earlymaturity variety INPARI 13.
Table 2. Result of yield trial of selected lines in Musi Rawas district.

*) The numbers followed by different characters are significantly different for 5% level.
To further evaluate the yield performances, selected early maturity lines weresubjected to yield trials in five locations. The highest average yield in five locations is8.58 t/ha for RSKI 64-2 and followed by 8.48 t/ha for RSKI 153-1 and 8.48 t/ha for RSKI
276-2, whereas the average yield of an original line SKI 88, a national leading variety
Ciherang, and a national leading early maturity variety were only 8.06 t/ha, 8.22 t/ha,
and 7.54 t/ha, respectively (Table 3). Multi-location yield trials to reach at least 16locations as well as other examinations such as pest and diseases, grain quality should
be continued as a requirement of variety release in Indonesia.

16Table 3. Yield of tested lines in 5 locations of yield trials.

*) The numbers followed by different characters are significantly different for 5% level.
Conclusions
Based on the results it can be concluded as follow;
1.

The growth durations of mutant lines were ranging from 93.7 to 99.3 days fromsowing to harvesting, they were significantly shorter than those of original line SKI
88, national leading variety Ciherang and the early maturity national leading
variety INPARI 13.

2.

Yield of most mutant lines were not significantly difference with that of originalline, SKI 88 and national leading variety, Ciherang, but significantly higher thanthat of INPARI 13.

3.

To fulfill the requirement of variety release in Indonesia, other multi-location yieldtrials and other examinations such as pests, diseases and other grain quality
examinations should be conducted.

Acknowledgement
Thanks to my colleagues at the Division of Irradiation and Instrumentation CAIRT– NNEA for their helps in seed irradiation, and my colleagues at Plant Breeding
Laboratory, CAIRT – NNEA, especially Mr. Carkum, SP., for his excellent technicalassistance.
17

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