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Inheritance of Kernel Elongation in Rice

Golam Faruq1, O. Mohamad2, K. Hadjim3 and Craig Meisner4

1,2 School of Environmental Science and Natural Resource Science, Faculty of Science and Technology, Universiti Kebangsaan Malaysia 43600, Bangi, Selangor, Malaysia E-mail: faruqwrc@hotmail.com
3
Malaysian Agricultural Research Development Institute
4
International Maize and Wheat Improvement Centre (CIMMYT)

Abstract

An investigation was made to understand the inheritance of cooked kernel elongation in crosses using the rice cultivar Mahsuri Mutant. In the all three Mahsuri Mutant crosses, the frequency distribution of kernel elongation ratio of segregating populations formed a bimodal curve. However, in crosses of Mahsuri Mutant and Mahsuri (and its reciprocal cross) the bimodal curve was skewed towards lower kernel elongation. This suggests that this character may be governed by 1 or 2 loci. However, in crosses of Mahsuri Mutant and 9192 a very smaller peak compared to the other was noted, which denotes the predominance of one major gene along with few modifier genes.

Media summery

Mutant Mahsuri has excellent kernel elongation during cooking when it is properly aged. Analysis of the progeny from crosses with this variety suggest that it is controlled by 1 or 2 major genes and influenced by a number of modifier genes.

Key Words

Mahsuri Mutant, inheritance of cooked kernel elongation.

Introduction

Linear elongation of kernel on cooking is one of the major characteristics of fine rice (Sood et al., 1979). Genetic evaluation of kernel appearance and cooking quality form important objectives in rice grain quality improvement programs. Grain size and shape largely determine the market acceptability of rice, while cooking quality is influenced by the properties of starch. Some varieties expand more in size than others upon cooking. Lengthwise expansion without increase in girth is considered a highly desirable trait in high quality rices (Khush et al., 1979; Sood et al., 1983). Juliano (1972) considered kernel elongation as a physical phenomenon and reported it to be influenced by gelatinization temperature. Grain elongation of pre-soaked milled rice was associated with intermediate-amylose and low-gelatinization temperature. (Juliano and Perez, 1984). Varieties of Indian and Pakistani Basmati, Afghanistan’s Sadri and Myanmar’s D25-4 (Nga Kyee) rice possess the capacity for elongation of cooked grains. The variety Mahsuri Mutant, developed by Universiti Kebangsaan Malaysia and Malaysian Agricultural Research Institute, was initially developed as a blast resistant line. It has subsequently become popular for its high cooked kernel elongation ratio (Hadjim et al., 1994 and Faruq et al., 2003). Interestingly, it is only after aging that this variety demonstrates good kernel elongation. According to Sood and Siddiq’s (1980) classification the degree of kernel elongation of Mahsuri mutant can be considered high (proportionate change 0.57-0.74) like several Basmati-type rice varieties. But without aging this mutant does not show high kernel elongation, and cooked grains have elongation similar to the Thai Jasmine and other basmati-type rice varieties from Pakistan and India. The nature of kernel elongation in Mahsuri Mutant may be quite different to other high quality rice varieties. In the present work we studied the segregation pattern of cooked kernel elongation ability in F2 populations of three Mahsuri Mutant crosses.

Methodology

Three crosses were made among Mahsuri Mutant, Mahsuri and 9192. F1 and F2 populations were raised at Malaysian Agricultural Development Research Institute. Kernel elongations of F2 populations were measured following a partially modified protocol of Sood and Siddiq (1980). About 210 plants representing F2 generation of each cross were analyzed to study the segregation pattern of kernel elongation. It was not possible to measured elongation ratio in F1 seeds, because of their weak stature.

Results and discussion

Elongation ratio and grain shape of the parental materials are described in Table 1. The observed and expected segregation ratios based on Mendelian inheritance pattern of these crosses are shown in Table 2.

Table 1: Cross descriptions

Cross

Elongation ratio

Grain shape

Mahsuri Mutant Mahsuri

Mahsuri Mutant 9192

Mahsuri Mahsuri Mutant

High Low

High Medium

Low High

Long Short

Long Long

Short Long

Define long and short grain in terms of brown or milled rice grain length in mm

Table 2: Mode of segregation of kernel elongation ratio in F2 populations of Mahsuri Mutant crosses


Cross

Observed segregation

Expected ratio

χ2

P

Elongation



Mahsuri Mutant Mahsuri

High

148

161

153

Low

60

Very Low

1



3:1



2.17



0.10-0.25

Mahsuri Mutant 9192

49

-

3:1

0.69

0.25-0.50

Mahsuri Mahsuri Mutant

57

-

3:1

0.51

0.25-0.50

Table 3: Mean and range of kernel elongation ratio of parents and F2 populations

Parents / Cross

Mean

Range

Variance

CV

Mahsuri

1.70

1.55 - 1.86

0.00

1.5

Mahsuri Mutant

2.14

2.00 - 2.31

0.00

2.1

9192

1.92

1.73 - 2.29

0.02

1.8

F2 of Mahsuri Mutant Mahsuri

2.04

1.65 - 2.31

0.07

11.3

F2 of Mahsuri Mutant 9192

2.07

1.78 - 2.28

0.09

10.6

F2 of Mahsuri Mahsuri Mutant

2.02

1.62 - 2.30

0.02

6.9

Cross-of Mahsuri Mutant Mahsuri

This cross of Mahsuri Mutant and Mahsuri involved high and low kernel elongation ratio parents. The mean elongation ratio was between the parents and the range of variation was greater in the F2 population, indicating significant variation for this grain quality character (Kernel elongation ratio). The frequency distribution of this character in F2 generation was bimodal (Figure 1) and skewed towards low kernel elongation, suggesting the predominance of major genes in controlling this trait. The mean elongation ratio of the F2 populations was (2.04), where as the lowest and the highest values observed in parental lines, Mahsuri and Mahsuri Mutant, were 1.70 and 2.14 respectively (Table 3). The ranges of the F2 populations were 1.65 - 2.31, whereas the ranges of 2.00-2.31 and 1.55-1.86 were observed in parental lines (Table 3).

Cross-of Mahsuri Mutant 9192

This cross involved high and medium kernel elongation ratio parents. The range of variation in F2 was confined between parental limits, indicating the absence of transgressive segregation. The frequency distribution of this character in F2 generation was also bimodal (Figure 2) and one of the peaks was smaller than the other, suggesting the action of one major gene along with few modifier genes. The mean elongation ratio of the F2 population was 2.07, whereas the elongation ratios of the parental lines were 2.14 and 1.92, respectively. The ranges of the F2 populations were 1.78-2.28, whereas the ranges in parental materials were 2.00-2.31 and 1.73-2.29 respectively (Table 3). The coefficient of variation in the F2 was highest for kernel elongation (11.3) in Mahsuri Mutant/Mahsuri, followed by 10.6 in Mahsuri Mutant/9192 and 6.9 in Mahsuri/Mahsuri Mutant.

Cross-of Mahsuri Mahsuri Mutant

This was the reciprocal of the first cross. Here the mean elongation ratio was also within the parental limits. The range of variation was higher in the F2 population than for the parents, indicating generation of significant variation for kernel elongation ratio. The frequency distribution of this character in F2 generation was also bimodal (Figure 3) with the frequency skewed towards low kernel elongation, again suggesting the action of one major gene in controlling this trait. Hadjim et al. (1994) noted that in the Mahsuri Mutant the low kernel elongation ratio was dominant over higher kernel elongation ratio. The mean elongation ratios of the F2 populations were 2.02, whereas the highest and lowest elongation ratios observed in parental lines were 2.14 (Mahsuri Mutant) and 1.70 (Mahsuri), respectively. The range within the F2 population was 1.62-2.30, whereas the 2.00-2.31 and 1.55-1.86 were observed in parental lines (Table 3).

Figure 1: Frequency distribution of kernel elongation ratio in F2 Populations of the cross Mahsuri Mutant Mahsuri

Figure 2: Frequency distribution of kernel elongation ratio in F2 populations of the cross, Mahsuri Mutant 9192

Figure 3: Frequency distribution of kernel elongation ratio in F2 populations of the cross Mahsuri Mahsuri Mutant

Conclusion

From the observations, it is suggested that kernel elongation ratio is controlled by 1 or 2 major genes and those were influenced with few modifier genes. However, it is noted that the nature of kernel elongation of Mahsuri Mutant is different to that of Basmati-type rices as high kernel elongation of the Mahsuri Mutant is only achieved after the rice is aged.

References

Faruq, G., O. Mohamad, K. Hadzim and M.A. Craig, 2003. Optimization of Aging Time and Temperature of Four Malaysian Rice Cultivars. Pakistan Journal of Nutrition 2 (3): 125-131

Khush, G. S., C.M. Paule, and N.M. Delacruz, 1979. Rice grain quality evaluation and improvement of IRRI. In Proc.on Workshop of Chemicals Aspects of Rice Grain Quality. pp.21-31. Los Banos, Philippines.

Hadjim, K., N.H. Ajimilah, O. Othman, N.T. Arasu, A. Latifah, and A. Saad. 1994. Mahsuri Mutant: Baka untuk beras bermutu. Teknol. Padi (MARDI), Jil. 4:7-13.

Juliano, B.O. 1972. Physico-chemical properties of starch and protein and their relation to grain quality and nutritional value of rice. Rice Breeding. International Rice Research Institute, Los Banos, Philippines.

Juliano, B.O and C.M. Perez, 1984. Result of a collaborative test on the measurement of grain elongation of milled rice during cooking. J. Cereal Sci.2: 281-292.

Sood, G.B. and E.A. Siddiq, 1979. Geographical distribution of kernel elongation gene (s) in rice. Indian J. Genet. Plant Breed 40:439-442.

Sood, G.B and E.A. Siddiq, 1980. Studies on component quality attributes of basmati rice, Oryza sativa L. Z. Pflanzenziichtg. 84:294-301.

Sood, G.B., E.A. Siddiq and Zaman, U.F. 1983 Genetic analysis of kernel elongation in rice Indian J. Genet. Plant Breed.43:40-43

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