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PPS 5(1):17-21 (2002)
Genetic Effect on Amylose and Protein Contents
in the Crossed Rice Seeds
Jong Gun Won, Tomohiko Yoshida* and Yousuke Uchimura**
(Kyongbuk Agriculture Technology Administration, 200 Donghodong, Bukgu, Taegu
702-320, Korea; * Faculty of Agriculture, Utsunomiya University, Utsunomiya 321-
8505, Japan; ** Fukuoka Agricultural Research Center, Chikushino 812-8548, Japan)
Abstract : The nature of gene action may be revealed and desirable parents may be
found by analyzing the combining ability and estimating the degree of heterosis in an
early generation. Currently, varieties with a good eating quality are preferred. This study
was carried out to obtain information on the action of genes using the analysis of
variance components estimated by minimum norm quadratic unbiased estimation
(MINQUE(1)) and to estimate the genetic effects on amylose and protein contents, as
criteria for selection of good eating quality by adjusted unbiased prediction (AUP). The
mean values of amylose content, protein content and grain yield in the parents were
18.4%, 7.78% and 19.8 g plant・, respectively, and those in crossed F1 seeds were 17.4%,
10.8% and 23.6 g plant・, respectively. The effects of additive were significant for both
amylose and grain yield, but not for protein content, indicating the importance of the
additive gene action on amylose content and grain yield. The effects of dominance were
highly significant for amylose content, protein content and grain yield. Especially, the
effect of dominance was greater than that of additive on protein content. The effect of
maternal was detected in only amylose content, and lines 42 and 53 showed significant
and negative maternal effect on amylose content. Ansanbyeo, Hinohikari, L 42 and L 53
exhibited negative additive effects on amylose content, which suggested the possibility
of a decreased amylose content in their crossed progenies. Mid-parent heterosis for
amylose content ranged from ・4.7% (L 42 x Hinohikari) to 32.9% (L 53 x Lemont)
with an average value of ・.2% for all crossed F1 hybrids. However, all of the crossed
seed showed positive mid-parent heterosis for protein content in this study and the
differences were not significant among the hybrids.
Key words : Amylose content, Genetic effect, Heterosis, Protein content, Rice.
Received 23 May 2001. Accepted 25 September 2001.
Corresponding author: T.Yoshida
Consumers in Korea and Japan prefer soft and sticky rice. Various physical and
chemical tests have been devised to measure the cooking and processing characteristics
of these criteria for evaluating the quality. Physicochemical properties of milled rice can
be used to select rice cultivars with good eating quality. Especially, amylose and protein
contents of milled rice are very effective criteria for selection of good eating quality in
early breeding generations (Inatsu, 1998; Sakurai et al., 1988; Tanifuzi et al., 1988).
Since rice with a low amylose content has a high consumer preference, amylose content
can be used as a criterion for selecting highly desirable genotypes (Oosato et al., 1998).
Amylose content is an important factor for predicting processing, cooking and
eating characteristics. The varieties with low amylose and low gelatinization
temperatures tend to be sticky and cohesive when cooked, absorb more water and thus
have a greater volume after cooking (Poehlman, 1987). Amylose content exhibited
negative correlations with the softness, cohesiveness, color and glossiness of cooked rice
(Juliano et al., 1965).
Protein content averages about 8% in brown rice and about 7% in milled rice.
The protein level in rice is low compared to other cereals, but the nutritional value of
protein is high due to the high content and favorable balance of essential amino acids,
including lysine (Poehlman, 1987). Ishima et al. (1974) and Sakuri et al.(1988) also
reported a negative correlation between the overall evaluation of taste and protein
content in milled rice. Amylose and protein are the chemical components which
influence the physical characteristics of cooked rice (Inatsu, 1998; Sakurada et al.,
1988). Therefore, the breeding of high eating牧uality rice has been focused on the low
amylose and protein contents.
Even though, as mentioned previously, the contents of amylose and protein are
very important physicochemical properties for good eating quality of rice, there are few
reports on gene action such as combining ability and heterosis about these properties,
especially, in the crossed F1 rice seeds. Gene action implies the capacity of a parent to
produce superior progenies when crossed with another parents. In breeding programs,
the information on the genetic effects of parents and heterosis in crosses is very
important. By analyzing the genetic effects and estimating the degree of heterosis, the
nature of gene action may be revealed, and desirable parents and important yield traits
may be found (Can et al., 1997). Therefore, it is very important to obtain information on
the gene action on the contents of amylose and protein in order to develop cultivars
including direct seeding rice that have good eating qualities. The objectives of this study
were to analyze the genetic effects of parents and crossed F1 rice seeds on the amylose
and protein contents in several rice cultivars selected for direct-seeding in the flooded
paddy field, and to identify promising parents with good additive gene action for these
physicochemical properties in direct-seeded rice.
Materials and Methods
In the summer of 1998, one 4 x 3 factorial crossing (Design II mating scheme;
Comstock and Robinson, 1948) was completed using seven parents. Four lines selected
for direct-seeding (L 38, L 42, L 53 and L 76) mainly by lodging tolerance, yield and
grain quality (Won et al., 1998) were used as the female parents, and three cultivars,
Ansanbyeo, Hinohikari and Lemont, as the male parents. The seeds of crossed F1 and
parents were stored in the refrigerator at 4 until analysis. First, the contents of amylose
and protein were compared between milled rice and brown single rice seed using parent
rice seeds (Fig. 1). The milled rice was powdered and then 100 mg was treated with 0.5
N NaOH for 2 hours for amylose analysis. For brown rice, we used a single rice seed. It
was once crushed before analysis and treated with 0.5 N NaOH for 6 hours. In protein
analysis, 300 mg of powdered milled rice and a single brown rice seed were used. The
contents of amylose and protein in crossed seeds were analyzed using only a single
brown rice seed. Protein content was calculated by multiplying Kjeldahl nitrogen by
5.95 (the protein factor). Amylose content was measured with an Auto Analyzer II
(BRAN+LUEBBE Co., Ltd.) using a single seed.
The data were analyzed using minimum norm quadratic unbiased estimation
(MINQUE) and adjusted unbiased prediction (AUP). The variance components were
estimated by MINQUE(1) approaches, and random genetic effects were predicted by the
AUP method (Zhu, 1992; Zhu, 1993; Zhu and Weir, 1996). A t-test based on jackknife
variances was used for detecting significance of variation.
Both mid-parent heterosis and high-parent heterosis were calculated as follows;
Mid-parent heterosis (%) = [ (F1MP)/MP ] x 100
High-parent heterosis (%) = [ (F1HP)/HP ] x 100
where F1 is the performance of the hybrid, MP is the average performance of parents and
HP is the performance of the higher parent.
Results and Discussion
Since the amount of crossed rice seeds is limited, it is difficult to analyze amylose
and protein contents using crossed seeds by the standard method. Few studies have been
reported on the genetic effect and heterosis on the rice grain quality of crossed F1 seeds
in the early generation in breeding programs. In the present study, we analyzed the
additive, dominant, and maternal effects and heterosis using crossed F1 seeds, having a
triploid endosperm, 1 n from the male and 2 n from the female parent.
The amylose and protein contents in powdered milled rice and a single brown
rice seed of parents are shown in Fig. 1. The amylose content was higher, and the protein
content was lower in the brown rice seed than in the powdered milled rice. The contents
of amylose and protein in the single brown rice significantly correlated with those in the
powdered milled rice (r = 0.97** for amylose and r = 0.85** for protein). These results
suggest that the analysis of a single brown rice seed for amylose and protein contents
gives results comparable to the standard analysis commonly used. Thus, it is possible to
analyze amylose and protein contents using few crossed F1 seeds.
The mean amylose content was 18.4% for the parents and 17.4% for the hybrids
(Table 1). The mean protein content was 7.78% for the parents and 10.8% for the hybrids.
The mean grain yield per plant was 19.8 g for the parents and 23.6 g for the hybrids.
Generally, the mean content of protein was higher in the hybrid than in the parents, but
the amylose content in the hybrids was lower than that in the parents.
Table 2 shows the results of the variance components estimated by MINQUE(1)
for additive, dominance and maternal effects for all of the traits in this study. The
variance of additive effect was significant for amylose content and grain yield, but not
for protein content. Therefore, the additive genetic effect is very important on these two
traits. Gravois and McNew (1993) reported that if the additive action of genes was
predominant in a self-pollinated species such as rice, the breeder could effectively select
the lines at various levels of inbreeding, because the additive effects were readily
transmissible from one generation to another. The effects of dominance were highly
significant for amylose content, protein content and grain yield. This indicates that these
two traits, amylose content and grain yield, are also controlled by nonadditive gene
actions such as dominant genes. The effect of dominance on protein content was
significant and larger than that of additive, indicating the importance of the dominance
gene action on this trait.
The proportion of the additive effect to the total phenotype variance due to the
cross combination in amylose content and grain yield was 42.7% and 73.1%,
respectively, and that of the dominance effect was 26.4% and 16.7%, respectively
(Table 2), indicating that the nonadditive gene actions also affected yield and other traits
as well. Although additive gene actions accounted for a majority of the genetic variations
among hybrids for most traits (Gravois and McNew, 1993; Won and Yoshida, 2000), the
dominance effect was predominant for protein content (88.5%) in this study. The
maternal effect was detectable only in the amylose content, which account for 27.9% of
total phenotype variance. Among the female parents, L 42 and L 53 showed significant
and negative maternal effects for amylose content, but the other two parents showed
positive maternal effects for amylose content (Table 4). Because the crossed F1 seeds
had a triploid endosperm, the maternal effects were more important for the content of
amylose. Pooni et al. (1992) proposed a model for analyzing the direct seed effects and
maternal/cytoplasm effects of endosperm traits, and reported that amylose content might
be related to the effects of the maternal plant or cytoplasm. Shi et al. (1997) also
reported that main factors in controlling the amylose content were maternal and
cytoplasmic effects, whereas Xu et al. (1995) reported that rice amylose content was
mainly controlled by the triploid endosperm genotype without any cytoplasmic effects.
Ansanbyeo, Hinohikari, L 42 and L 53 exhibited negative additive effects on
amylose content, suggesting the importance of these parents for decreasing the amylose
content (Table 3). The additive effects on protein content were not significant for all the
parents in this study. The additive effects on grain yield were positive in Lemont, L 42
and L 76, indicating the importance of these three parents for higher yield. Hinohikari
and L 53 had negative additive effect on amylose content that affects the cooking quality.
On the other hand Lemont and L 42 had a good additive effect on the grain yield.
Among the 12 cross combinations in the F1 generation, seven combinations
exhibited negative dominance effects on the amylose content, six combinations negative
dominance effects on the protein content, and six combinations positive dominance
effects on the protein content. Larger and negative dominance effects on the amylose
content were observed in L 38 x Lemont, L 42 x Hinohikari, L 53 x Hinohikari and L 76
x Lemont (Table 3). The dominance effects on the protein content in L 38 x Ansanbyeo
and L 53 x Hinihikari hybrids were negative and relatively large. High and positive
dominance effects on the grain yield were observed in L 38 x Lemont, L 42 x Lemont, L
53 x Hinohikari and L 76 x Ansanbyeo. The best general combiner for amylose content,
L 42 in the female parent group, had two negative dominance values out of three and the
best general combiner, Ansanbyeo in the male parent group, had three negative
dominance values out of four. The best general combiner for protein content, L 53 in the
female parent group, had two negative dominance values out of three, and the best
general combiner, Lemont had two negative dominance values out of four. However, the
values for the poorest cultivars showed the opposite tendency for the contents of amylose
and protein in this study. These results indicate that it is probable for parents with a good
additive effect to have a good dominance effect more frequently than parents with a poor
additive effect.
Mid-parent heterosis for amylose content ranged from ・4.7% (L 42 x
Hinohikari) to 32.9% (L 53 x Lemont), with an average value of ・.2% for all hybrids,
and high-parent heterosis for amylose content was somewhat lower (Table 5). Crosses of
L 42 x Ansanbyeo, L 42 x Hinohikari, 53 x Ansanbyeo and L 53 x Hinohikari showed a
large and negative high-parent heterosis value. These four parents, Ansanbyeo,
Hinohikari, L 42 and L 53, also showed negative additive effects (Table 3). However, all
of the crosses showed positive mid- and high- parent heterosis for protein content in this
study and the differences among the hybrids were not so significant except L38 x Lemont.
Certain parents, L 76 and Lemont produced large and positive yield heterosis. The mid-
parent heterosis for yield ranged from ・6.3% (L 42 x Ansanbyeo) to 37% (L 53 x
Hinohikari) with an average value of 17.3% for all hybrids. The high-parent heterosis for
yield ranged from ・9.5% (L 42 x Ansanbyeo) to 34.4% (L 53 x Hinohikari) with an
average value of 3.0% for all hybrids. Crosses of L 42 x Lemont, L 53 x Hinohikari and
L 76 x Hinohikari showed a large and positive high-parent heterosis value.
Even though the sampled parents were few and did not represent the diversity of
rice germplasm, such as indica varieties, the additive effect on amylose content was
more important than the dominance effect. It may be stated that the additive gene action
played a more important role in the inheritance of the amylose content than the dominant
gene action, therefore, the breeders can effectively select this trait at various levels of in
breeding. However, for protein content, the dominance effect is more important than the
additive effect, suggesting that a dominance gene action is more important than the
additive gene action in the inheritance of the protein content. The effect of maternal was
detected on only amylose content, and L 42 and L 53 showed significant and negative
maternal effect. Several varieties exhibited negative additive effects on amylose content,
therefore, they might contribute to reduce the amylose content and increase the eating
quality in their crossed progenies. However, the additive effect on the protein content
was not significant among the varieties and the values were very small. Several varieties
showed a positive additive effect on the grain yield. Thus, L 42 and L 53 showed high
additive effects on the amylose content, and Lemont and L 42 showed a high additive
effect on the grain yield.
Acknowledgement
The authors are grateful to Dr. J. Zhu, Dean & Professor, College of Agriculture &
Biotechnology, Zhejiang Univesity, China, for the valuable software and genetic analysis
of the data.
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* In Japanese with English summary.
** In Japanese with English abstract.
*** Translated from Japanese by the present authors.
Table and Figure caption
Fig. 1. Relationship of the amylose and protein contents between powdered milled rice
and brown rice seed of parents.
Table 1. Mean values of amylose content, protein content
and grain yield in parents and crossed F1 seeds.
Table 2. Variance components estimated by minimum norm
quadratic unbiased estimation (MINQUE(1)) for 4 x 3
factorial corssing (Design II mating scheme).
*, **, ns : Significant at 5%, 1% level and not significant, respectively.
Table 3. Prediction of genetic effects on additive and dominance
effects by adjusted unbiased prediction (AUP) method.
1) Ansanbyeo, 2) Hinohikari, 3) Lemont.
4) Estimate ｱ S.E.
・ *, **, ns : Significant at 10 %, 5 %, 1 % level and not
significant, respectively.
Table 4. Prediction of genetic effects on maternal effects by
adjusted unbiased prediction (AUP) method.
1) Estimate ｱ S.E.
*, ns : Significant at 5% level and not significant, respectively.
Table 5. Estimates of mid-parent and high-parent heterosis (%) for amylose and
protein content in crossed F1 seeds.
1) Ansanbyeo, 2) Hinohikari, 3) Lemont.
* : Mid-parent heterosis calculated from 100 x [(F1MP)/MP], where F1 indicates
performance of hybrid. MP indicates average performance of parents.
** : High-parent heterosis calculated from 100 x [(F1HP)/HP], where F1 indicates
performance of hybrid. HP indicates average performance of higher parents.
Won et al.・Genetic Effect on Amylose and Protein Contents in Rice