The Scientific World Journal
Volume 2016 (2016), Article ID 2796720, 14 pages
http://dx.doi.org/10.1155/2016/2796720

Research Article

Variability Assessment of Aromatic and Fine Rice Germplasm in Bangladesh Based on Quantitative Traits

M. Z. Islam,¹ M. Khalequzzaman,¹ M. K. Bashar,² N. A. Ivy,³ M. M. Haque,³ and M. A. K. Mian³

¹Genetic Resources and Seed Division, Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh
²CIAT, HarvestPlus, Banani, Dhaka 1213, Bangladesh
³Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur 1706, Bangladesh

Received 20 September 2015; Revised 2 February 2016; Accepted 29 February 2016

Academic Editor: António Amorim

Copyright © 2016 M. Z. Islam et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

The study was conducted to investigate genetic variability among 113 aromatic and fine local rice genotypes of which five were exotic in origin. The test genotypes were evaluated for 19 growth traits, yield components, and yield. All the quantitative traits varied significantly among the test genotypes. High heritability along with high genetic advance was observed for flag leaf area, secondary branches per panicle, filled grains per panicle, grain length, grain breadth, grain length breadth ratio, and 1000 grain weight. Such findings suggested preponderance of additive gene action in gene expression for these characters. Grain yield was significantly and positively correlated with days to flowering, days to maturity, panicle length, filled grains per panicle, and 1000 grain weight. According to cluster analysis, 113 test genotypes formed 10 clusters. Selection of parents from the clusters V and X followed by hybridization would possibly result in desirable heterosis for the development of heterotic rice hybrids. Finally, molecular characterizations of the studied germplasm are required for high resolution QTL mapping and validating the presence of candidate genes responsible for valuable characters.

1. Introduction

Bangladesh is mainly a country of rice based cropping system, where thousands of local rice varieties are being cultivated from the time immemorial [1]. To date, farmers across the country are used to cultivate different local varieties or landraces particularly in the unfavourable ecosystems. Local variety including aromatic rice genotypes occupied about 12.16% of the rice growing areas in Bangladesh [2]. Many of these local varieties have some special characteristics such as aroma, better taste, and higher cooking quality which also provide additional value in socioeconomic aspects. Moreover, aromatic rice constitutes a special group of rice genotypes well known in many countries across the world for their aroma and/or super fine grain quality [3]. Bangladesh has a stock of above 8,000 rice germplasms of which nearly 100 are aromatic [1, 4]. It is worthwhile to mention that aromatic rice is closely related to the social and cultural heritage in Bangladesh and it is consumed during weddings and other festivals [5]. Aromatic and fine rice germplasm native to Bangladesh generally have short bold and medium bold grain type with mild to strong aroma [6, 7]. In Bangladesh, among the different aromatic rice varieties, Chinigura is the predominant one that covers more than 70% of rice farms in the northern districts of Naogaon and Dinajpur. Other important aromatic rice varieties are Kalijira (predominantly grown in Mymensingh) and Kataribhog (mainly cultivated in Dinajpur) [8]. Most of the aromatic rice varieties in Bangladesh are of locally adapted, photoperiod-sensitive, and grown during Aman season under rainfed lowland ecosystem. The production cost of aromatic and fine rice is low compared to that of coarse rice. Therefore, the income potential is higher with aromatic fine rice cultivation, since its cultivation does not usually require additional expenditures on fertilizer, pesticides, and irrigation. However, the average yield of high yielding rainfed lowland rice is 3.4 t/ha, whereas that of aromatic rice is 2.0–2.3 t/ha [9].

Knowledge on genetic diversity among crop populations and its quantitative assessment usually helps a breeder to select suitable parents to be utilized in breeding programmes [10–15]. Among the different cereal crops, rice is (Oryza sativa) one of the best models to undertake the study of genome structure and genetic diversity. Its diploid genome is relatively smaller in size (430 Mb) with a significant level of genetic polymorphism and a large amount of well-conserved genetically diverse material [16–18].

In a breeding programme, genetic improvement primarily depends upon the amount of genetic variability present in the population. In many cases, characters are mostly governed by poly genes which are highly influenced by the environment. Therefore, it is difficult to predict whether the existing variability is heritable or not. Furthermore, heritability of a genetic trait is very important in determining the response to selection because it implies the extent of transmissibility of that trait into next generations [19, 20]. In addition, high genetic advance coupled with high heritability offers the most effective condition for selection for a specific character [21].

These days, plant breeders usually evaluate genetic diversity on the basis of morphological traits because they are more economic, faster, and easier to score compared to the molecular traits [22, 23]. Investigation to these traits also does not require any sophisticated procedure or advanced equipment. In addition, these traits can be transmitted without adapting any special biochemical or molecular techniques. The rice plant is morphologically diverse, especially in terms of the vegetative traits such as plant height and leaf length. Our previous studies involving local aromatic and nonaromatic rice germplasm from Bangladesh using morphological, physicochemical, and molecular markers revealed high genetic diversity [6, 24–28]. However, such investigations on aromatic and fine rice genotypes are not yet to be conducted. Therefore, the present study was undertaken to assess the genetic diversity of aromatic and fine rice genotypes in Bangladesh.

2. Materials and Methods

2.1. Experimental Site

The experiment was conducted at the research farm of Bangladesh Rice Research Institute (BRRI), Gazipur, during July to December (T. Aman season), 2011. Geographically, the place is located at about 24.00°N latitude and 90.25°E longitude with an elevation of 8.4 meters from the sea level and is characterized by subtropical climate. The soil of the experimental site was clay loam in texture.

2.2. Plant Materials

A total of 113 aromatic and fine rice genotypes (Table 1) were selected from BRRI genebank. Pregerminated seeds were sown in the seed bed.

Table 1: Information on place of collection, source, and local name of the aromatic and fine rice accessions.

Sl. No.
Genotypes
Acc. No./source
Place of collection
Kernel size and shape
1.7% KOH (aroma)

1
Sakor
197
Mymensingh
Short, bold
Lightly scented

2
Sagardana
229
Mymensingh
Short, medium
Lightly scented

3
Nunia
233
Mymensingh
Short, medium
Lightly scented

4
Chini Sagar ()
245
Mymensingh
Short, medium
Scented

5
Meny
288
Gaibandha
Short, bold
Scented

6
Tilkapur
296
Gaibandha
Short, medium
Lightly scented

7
Binnaphul
315
Gaibandha
Short, medium
Lightly scented

8
Kalobhog
318
Gaibandha
Short, medium
Scented

9
Jabsiri
331
Gaibandha
Short, medium
Scented

10
Kalgochi
352
Gaibandha
Short, bold
Scented

11
Chinisakkor
387
Rajshahi
Short, medium
Scented

12
Chiniatob
399
Rajshahi
Short, medium
Scented

13
Noyonmoni
461
Rajshahi
Short, medium
Scented

14
Saubail
873
Sylhet
Short, medium
Scented

15
Chinniguri
1880
Kishoreganj
Short, bold
Scented

16
Kalomala
1886
Kishoreganj
Short, medium
Scented

17
Begunmala
1896
Kishoreganj
Short, medium
Scented

18
Gopalbhog
1938
Kishoreganj
Short, medium
Scented

19
Tulsimoni
1980
Jamalpur
Short, medium
Scented

20
Jirabuti
1984
Mymensingh
Short, bold
Scented

21
Khirshabuti
1996
Tangail
Short, medium
Scented

22
Rajbut
1999
Tangail
Short, medium
Scented

23
Soru kamina
2015
Satkhira
Short, bold
Lightly scented

24
Kamini soru
2027
Satkhira
Short, bold
Lightly scented

25
Doiarguru
2037
Khulna
Short, bold
Lightly scented

26
Premful
2041
Satkhira
Short, medium
Scented

27
Begun bichi
2073
Kishoreganj
Short, bold
Lightly scented

28
Elai
2423
Dhaka
Long, slender
Nonscented

29
Gua masuri
3666
Sherpur
Short, medium
Nonscented

30
Luina
3676
Netrokona
Short, medium
Scented

31
Lal Soru
4135
Dinajpur
Short, medium
Scented

32
Chini Kanai
4356
Khulna
Short, bold
Scented

33
Kalijira (short grain)
4357
Khulna
Short, bold
Scented

34
Rajbhog
4360
Khulna
Short, medium
Scented

35
Philippines Kataribhog
4365
Dinajpur
Short, medium
Scented

36
Baoibhog
4813
Kurigram
Short, medium
Scented

37
Baoijhaki
4826
Dinajpur
Short, medium
Lightly scented

38
Jirabhog (Bolder)
4828
Dinajpur
Short, bold
Lightly scented

39
Chinigura
4867
Mymensingh
Short, bold
Scented

40
Tulsimala
4870
Mymensingh
Short, bold
Scented

41
Bashmati 370
4904
Pakistan
Medium, slender
Scented

42
Uknimodhu
5083
Rangpur
Short, medium
Scented

43
Ranisalut
5286
Khulna
Short, bold
Lightly scented

44
Jira dhan
5313
Khulna
Short, bold
Scented

45
Gandhakusturi
5319
Bagerhat
Short, bold
Nonscented

46
Sakkorkhora
5347
Barguna
Short, bold
Scented

47
Badshabhog
5349
Bagerhat
Short, bold
Scented

48
Jirakatari
5975
Dinajpur
Short, bold
Scented

49
Desikatari
5978
Dinajpur
Short, medium
Scented

50
Thakurbhog
5983
Sylhet
Short, medium
Nonscented

51
Tulsimaloty
6638
Tangail
Short, bold
Scented

52
Raduni pagal
6711
Rajshahi
Short, medium
Scented

53
Sugandhi dhan
7063
Nawabganj
Short, medium
Nonscented

54
Kalijira (long grain)
4358
Khulna
Short, medium
Scented

55
Jesso balam TAPL-25
2454
GRSD, BRRI
Short, medium
Scented

56
Dakshahi
983
Khulna
Short, bold
Nonscented

57
Hatisail TAPL-101
2528
GRSD, BRRI
Short, bold
Scented

58
Khasa
682
Comilla
Short, medium
Scented

59
Buchi
369
Gaibandha
Short, bold
Scented

60
Awned TAPL-545
2939
GRSD, BRRI
Short, bold
Scented

61
Black TAPL-554
2947
GRSD, BRRI
Short, bold
Scented

62
Straw TAPL-500
2898
GRSD, BRRI
Long, slender
Scented

63
Dubsail
4840
Satkhira
Short, bold
Scented

64
Duksail
2028
Satkhira
Short, bold
Nonscented

65
Khaskani
4341
Jessore
Short, medium
Scented

66
Khazar
4921
Iran
Long, slender
Nonscented

67
Basmati Sufaid 106
4498
Pakistan
Medium, slender
Lightly scented

68
BR5
4343
GRSD, BRRI
Short, bold
Scented

69
BRRI dhan34
7093
GRSD, BRRI
Short, medium
Scented

70
BRRI dhan37
7094
GRSD, BRRI
Short, medium
Scented

71
BRRI dhan38
7095
GRSD, BRRI
Medium, slender
Scented

72
BRRI dhan50
6882
GRSD, BRRI
Long, slender
Lightly scented

73
Khasa Mukpura
7586
Khagrachhari
Short, medium
Scented

74
Uknimodhu
298
Gaibandha
Short, bold
Scented

75
Bawaibhog-2
301
Gaibandha
Short, medium
Scented

76
Chiniatob-2
398
Rajshahi
Short, bold
Scented

77
Tilokkachari
758
Chittagong
Short, bold
Scented

78
Begunbichi-2
508
Rangpur
Short, bold
Scented

79
Chinairri
764
Chittagong
Short, bold
Scented

80
Bhatir chikon
774
Chittagong
Short, medium
Scented

81
Gordoi
1908
Kishoreganj
Short, bold
Nonscented

82
Dolagocha
451
Rajshahi
Short, bold
Nonscented

83
Kalonunia
537
Rangpur
Short, medium
Lightly scented

84
Dhan chikon
538
Dinajpur
Short, medium
Lightly scented

85
Badshabhog-2
03
Dhaka
Short, bold
Scented

86
Thakurbhog-2
872
Sylhet
Short, bold
Nonscented

87
Khuti chikon
4107
Comilla
Short, bold
Lightly scented

88
Sunduri samba
4803
Rajshahi
Short, medium
Nonscented

89
Basmati
4754
Barguna
Short, bold
Scented

90
Basmati 37
4491
India
Long, slender
Lightly scented

91
Basnatu sufaid 187
4499
Pakistan
Long, slender
Lightly scented

92
Tulsimala-2
7342
Sherpur
Short, bold
Lightly scented

93
Chinisail
7343
Sherpur
Short, medium
Lightly scented

94
Malshira
7347
Sherpur
Short, bold
Lightly scented

95
Sadagura
—
Khagrachhari
Short, medium
Lightly scented

96
Modhumadab
7352
Habiganj
Short, medium
Lightly scented

97
Parbatjira
7351
Habiganj
Short, bold
Lightly scented

98
Chinikanai-2
7350
Dinajpur
Short, bold
Lightly scented

99
Meedhan
7537
Habiganj
Short, medium
Lightly scented

100
Gobindhabhog
—
Jessore
Short, medium
Lightly scented

101
Kataribhog
7082
Dinajpur
Short, medium
Scented

102
Fulkari
7531
Habiganj
Short, bold
Lightly scented

103
BU dhan2R
7413
GRSD, BRRI
Long, slender
Lightly scented

104
Padmabhog
4812
Kurigram
Short, medium
Lightly scented

105
Dudsail
4840
Satkhira
Short, medium
Lightly scented

106
Sakkorkhana
4761
Barguna
Short, medium
Scented

107
Maloti
169
Tangail
Short, medium
Lightly scented

108
Bashful
4215
Kishoreganj
Short, medium
Scented

109
Kalijira TAPL-64
2492
GRSD, BRRI
Short, medium
Scented

110
Oval TAPL-2990
2990
GRSD, BRRI
Short, medium
Lightly scented

111
Kalijira TAPL-68
2496
GRSD, BRRI
Short, medium
Scented

112
Kalijira TAPL-74
2501
GRSD, BRRI
Short, bold
Scented

113
Kalobakri
2108
Narsingdi
Short, bold
Scented

2.3. Experimental Design and Setting the Experiment

The experiment was conducted following a randomized complete block design with three replicates for each treatment. Thirty-day-old seedlings of each test genotypes were transplanted on the 15th August, 2011 using single seedling per hill in 2.4 m² plot with 25 cm and 20 cm space between rows and plants, respectively.

2.4. Intercultural Operations

Fertilizers were applied @ 80 : 60 : 40: 12 kg N : P : K : S per hectare. However, except N, the other fertilizers were applied at final land preparation. Nitrogen was applied in three equal splits, at 15 days after transplanting (DAT), at 35 DAT, and just before flowering. Intercultural operations and pest control measures were done as and when necessary.

2.5. Data Collection

Data were collected on culm diameter (mm), flag leaf area (cm²), plant height (cm), days to flowering, days to maturity, effective tiller number (ET No.), panicle length (cm), primary branch length (cm), secondary branch length (cm), primary braches per panicle, secondary branches per panicle, number of filled grains per panicle, number of unfilled grains per panicle, grain length (mm), grain breadth (mm), grain length breadth ratio, 1000-grain weight (g), grain yield per hill (g), and harvest index (HI). Kernel quality was determined using dehusked grains. Kernels were classified on the basis of length (size) and for ratio (shape) following classification described by Cruz and Khush [29] (Table 2).

Table 2: List of quantitative traits of 113 aromatic and fine rice genotypes.

Traits
Method of evaluation

Culm diameter (CD, mm)
Outer diameter internodes of the 10 culms were measured and averaged

Flag leaf area (FLA, cm²)
Flag leaf area (cm²) = flag leaf length (cm) × maximum width (cm) × 0.75

Plant height (PH, cm)
The average of height from the base to the tip of last leaf (flag leaf)

Days to flowering (DF, days)
The number of days from seeding to flowering day

Days to maturity (DM, days)
The number of days from seeding to maturing day

Effective tiller number (ET No.)
Counting of effective tiller per hill

Panicle length (PL, cm)
Distance between apex of the panicle (excluding awn) and top most node (neck node) of the culm

Primary braches per panicle (PBP, no.)
Primary branches were counted from 5 randomly selected panicles and averaged

Primary branch length (PBL, cm)
Lengths of the primary branches present in a panicle were measured (cm) from five panicles and averaged

Secondary branches per panicle (SBP, no.)
Secondary branches were counted from 5 randomly selected panicles and averaged

Secondary branch length (SBL, cm)
Length (cm) of the 30 random secondary branches from five randomly selected panicles and averaged

Filled grains per panicle (FGP, no.)
Number of filled grains per panicle was counted from 10 randomly selected panicles and averaged

Unfilled grains per panicle (UFGP, no.)
Number of unfilled grains per panicle was recorded from 10 randomly selected panicles and averaged

Grain length (GL, mm)
Length (mm) of a grain was measured by a digital slide caliper from 10 randomly selected fertile grains excluding awn and averaged

Grain breadth (GB, mm)
Breadth of a grain (mm) was measured form 10 randomly selected fertile grains by a digital slide caliper and averaged

Grain length breadth ratio (GLBR)
Dividing grain length by grain breadth and averaged

1000-grain weight (TGW, g)
200 grains were weighted then 1000-weight grains were calculated from these weights

Yield per plant (GYP, g)
Ten randomly selected plants per replication and averaged

Harvest index (HI)
Ratio of grain yield to biological yield

2.6. Aroma Test

Aroma was detected by sniffing and was scored as nonscented, lightly scented, and scented following 1.7% KOH based method [30] (Table 2).

2.7. Statistical Analysis

Univariate analysis of the individual character (ANOVA) including the estimation of mean, range, and coefficient of variation (CV%) was conducted using a statistical software package MstatC. The test of significance was performed using Fisher’s () test. Multivariate analysis was conducted using another statistical software package GENSTAT version 5.5. Genetic parameters were also estimated to understand genetic variations among the test genotypes and to determine genetic and environmental effects on different characters. These genetic parameters were calculated using the following formula [31–33]. These parameters include the following:

(a)Genotypic variance, , where GMS is the genotypic mean sum of squares, EMS is the error mean sum of squares, and is number of replication.(b)Phenotypic variance, , where is the genotypic variance and is the mean squares of error.(c)Genotypic coefficient of variation , where is the genotypic variance and is the mean of character.(d)Phenotypic coefficient of variation , where is the phenotypic variance and is the mean of trait.(e)Heritability (broad sense) , where is the genotypic variance and is the phenotypic variance.(f)Expected genetic advance (GA): , where GA is a percent of the mean assuming selection of the superior 5% of accession: , where is a constant, is the phenotypic standard deviation, is the heritability, and is the mean of traits.

3. Result

3.1. Variation in Grain Diversity and Genetic Parameters among Accessions

The grain morphology varied considerably in genotypes collected from BRRI genebank (Figure 1) with respect to awning, colour and size of awns, lemma and palea with presence or absence of coloured furrows and spots, pubescence, and varied coloured apiculus and sterile lemma. Analysis of variance of 19 quantitative characters based on individual sample means showed highly significant () variations among the genotypes for all the characters outlined in Table 3. The range, mean, standard error, coefficients of variation, and value of 19 characters are presented in Table 4. The coefficient of variation ranged from 1.69 to 35.81% which indicates considerable variation among the character studied. Out of 19 traits, unfilled grains per panicle, harvest index, yield per plant, filled grains per panicle, primary branches per panicle, and secondary branches per panicle found with relatively higher coefficient of variation (35.81, 20.45, 18.70, 16.79, 11.61, and 11.03%, resp.) than the other traits. These possibly occurred because of sampling error and/or characters were more influenced by the environmental factors. In this study, most of the growth traits showed higher PCV compared to yield and yield component traits. However, lower PCV belonged to days to maturity (5.79%) while unfilled grains per panicle (46.57%) were recorded with higher value. Secondary branches per panicle (34.95%), 1000 grain weight (34.20%), and filled grains per panicle (29.32%) were recorded with higher values of PCV. However, panicle length (6.31%), days to flowering (7.40%), and plant height (10.04%) were found with lower values. The higher GCV was associated with 1000-grain weight (33.18%) whereas the value was fairly low in case of panicle length (5.06%). Results also showed narrow differences between PCV and GCV for most of the traits. Heritability ranged from 29.03 to 97.44%. The highest and the lowest amount of heritability were recorded at grain length and yield per plant, respectively.

Table 3: Analysis of variance for different quantitative characters in 113 aromatic and fine rice genotypes.

(a)

Source of variation
df
CD (mm)
FLA (cm³)
DF
DM
PH (cm)
ET No.
PL (cm)
PB No.
PBL (cm)
SB No.

Replication
2
1.173
32.105
0.51
1.507
250.964
28.769
15.972
4.975
0.081
38.629

Genotype
112
1.422
155.904
170.559
164.857
615.038
5.491
7.455
5.129
3.825
365.148

Error
224
0.158
17.342
2.257
4.951
16.130
1.156
1.164
1.441
0.593
12.993

CV%

8.60
11.70
2.10
2.69
2.78
10.93
3.77
11.61
7.71
11.03

(b)

Source of variation
SBL (cm)
FGP
UFGP
GL (mm)
GB (mm)
GLBR
TGW (g)
YP (g)
HI

Replication
0.044
3274.094
544.179
0.234
0.039
0.107
35.785
18.735
0.016

Genotype
0.228
4828.209
741.844
5.412
0.423
1.48
58.883
11.961
0.005

Error
0.034
675.308
241.344
0.047
0.017
0.03
1.206
1.624
0.002

CV%
6.66
16.79
35.81
3.06
5.58
5.55
8.31
18.70
20.44

indicates significance at 1% level of probability.

CD: culm diameter (mm), FLA: flag leaf area, DF: days to flowering, DM: days to maturity, PH: plant height, ET No.: effective tiller number, PL: panicle length, PB No.: primary branches per panicle, PBL: primary branch length, SB No.: secondary branches per panicle, SBL: secondary branch length, FGP: filled grains per panicle, UFGP: unfilled grains per panicle, GL: grain length, GB: grain breadth, GLBR: grain length breadth ratio, TGW: 1000-grain weight, Y/P: yield per plant, and HI: harvest index.

Table 4: Variability in different quantitative characters in 113 aromatic and fine rice genotypes.

Characters
Range
Mean
SE
CV%
-value

CD (mm)
3.14–7.50
4.63
0.065
8.60
8.98

FLA (cm³)
21.94–54.43
35.28
0.599
11.70
8.99

DF
76.00–125
100.5
0.709
2.45
75.58

DM
102–150
126.00
0.697
1.69
33.30

PH (cm)
79.00–179.00
129.00
1.382
2.74
38.13

ET No.
4.00–13.87
9.84
0.127
10.39
4.75

PL (cm)
24.13–33.00
28.62
0.149
3.77
6.40

PB No.
6.33–13.33
10.34
0.123
11.61
3.56

PBL (cm)
8.84–14.62
10.75
0.106
7.71
6.45

SB No.
12.20–65.67
32.67
1.038
11.03
28.10

SBL (cm)
1.95–3.58
2.75
0.026
6.66
6.79

FG/P
79.00–262.00
170.50
3.774
16.79
7.15

UFG/P
4.00–74.00
39.00
1.479
35.81
3.07

GL (mm)
5.62–12.24
7.11
0.126
3.06
114.34

GB (mm)
1.68–3.60
2.33
0.035
5.58
24.95

GLBR
1.97–5.60
3.10
0.066
5.55
49.59

TGW (g)
7.70–28.33
13.22
0.417
8.31
48.81

YP (g)
6.47–17.45
12.38
0.188
18.70
2.23

HI
0.16–0.34
0.24
0.004
20.45
1.93

indicates significance at 1% level of probability.

CD: culm diameter (mm), FLA: flag leaf area, DF: days to flowering, DM: days to maturity, PH: plant height, ET No.: effective tiller number, PL: panicle length, PB No.: primary branches per panicle, PBL: primary branch length, SB No.: secondary branches per panicle, SBL: secondary branch length, FGP: filled grains per panicle, UFGP: unfilled grains per panicle, GL: grain length, GB: grain breadth, GLBR: grain length breadth ratio, TGW: 1000-grain weight, YP: yield per plant, and HI: harvest index.

Figure 1: Variation in grain morphology of some aromatic and fine rice genotypes.

Days to flowering, grain breadth, grain length breadth ratio, plant height, and days to maturity were highly heritable, all with an estimated whereas other characters showed relatively low heritability. GA ranged from 0.03% for harvest index to 48.19% for filled grains per panicle. The genetic advance as percent of mean (GA%) ranged from 6.41% in panicle length to 50.85% in 1000 grain weight. In this study, flag leaf area, secondary branches per panicle, filled grains per panicle, grain length, grain breadth, grain length breadth ratio, and 1000-grain weight showed high heritability and high genetic advance indicated the presence of additive genes controlling these characters (Table 5).

Table 5: Estimation of genetic parameters of different quantitative characters in 113 aromatic and fine rice genotypes.

Character

GCV (%)
PCV (%)
(%)
GA (%)
GA in % of mean

CD (mm)
0.42
0.58
14.03
16.45
72.73
0.87
18.91

FLA (cm³)
46.19
63.53
19.10
22.40
72.70
9.16
25.73

DF
56.10
58.36
7.25
7.40
96.13
11.60
11.24

DM
53.30
58.25
5.53
5.79
91.50
11.03
8.36

PH (cm)
199.64
215.76
9.65
10.04
92.53
21.47
14.67

ET No.
1.45
2.60
12.22
16.39
55.56
1.42
14.39

PL (cm)
2.10
3.26
5.06
6.31
64.31
1.83
6.41

PB No.
1.23
2.67
10.72
15.80
46.04
1.19
11.50

PBL (cm)
1.08
1.67
9.66
12.03
64.50
1.32
12.26

SB No.
117.39
130.38
33.17
34.95
90.03
16.24
49.72

SBL (cm)
0.06
0.10
9.24
11.41
65.54
0.33
11.82

FG/P
1384.30
2059.61
24.04
29.32
67.21
48.19
31.14

UFG/P
166.83
408.18
29.77
46.57
40.87
13.05
30.08

GL (mm)
1.79
1.84
18.82
19.07
97.44
2.09
29.36

GB (mm)
0.14
0.15
15.78
16.74
88.84
0.55
23.50

GLBR
0.48
0.51
22.35
23.04
94.16
1.07
34.27

TGW (g)
19.23
20.43
33.18
34.20
94.10
6.72
50.85

YP (g)
2.19
7.55
11.96
22.20
29.03
1.26
10.18

HI
0.00
0.00
13.40
23.21
33.33
0.03
12.22

CD: culm diameter (mm), FLA: flag leaf area, DF: days to flowering, DM: days to maturity, PH: plant height, ET No.: effective tiller number, PL: panicle length, PB No.: primary branches per panicle, PBL: primary branch length, SB No.: secondary branches per panicle, SBL: secondary branch length, FGP: filled grains per panicle, UFGP: unfilled grains per panicle, GL: grain length, GB: grain breadth, GLBR: grain length breadth ratio, TGW = 1000 grain weight, YP: yield per plant, HI: harvest index, = genotypic variance, = phenotypic variance, (GCV) % = genotypic coefficient of variation,(PCV) % = phenotypic coefficient of variation, (%) = heritability (broad sense), and GA (%) = genetic advance.

3.2. Association between Traits

Pearson’s correlation coefficient was computed between 19 quantitative traits among 113 accessions of aromatic and fine rice genotypes (Table 6). Culm diameter was significantly and positively correlated with flag leaf area, days to flowering, days to maturity, plan height, and primary branches per panicle. Plant height showed highly significant positive correlation with culm diameter, days to flowering, days to maturity, and panicle length. Grain yield was highly significant () and positively correlated with days to flowering (), days to maturity (), filled grains per panicle (), primary branch length (), secondary branch length (), and 1000-grain weight () and positively correlated with panicle length () and secondary branches per panicle ().

Table 6: Pearson’s correlation coefficient among 19 quantitative traits of aromatic and fine rice genotypes.

CD
FLA
DF
DM
PL
ET No.
PH
FG
UFG
GL
GB
GLB
PB No.
PBL
SB No.
SBL
TGW
YP
HI

CD
1.00

FLA
0.471
1.00

DF
0.270
−0.061
1.00

DM
0.223
−0.129
0.978
1.00

PL
−0.036
0.004
0.123
0.187
1.00

ET No.
−0.441
−0.242
−0.057
−0.029
0.069
1.00

PH
0.266
−0.073
0.268
0.306
0.265
−0.007
1.00

FG
−0.007
−0.267
0.230
0.272
0.178
0.012
0.123
1.00

UFG
−0.103
−0.242
−0.143
−0.118
−0.012
0.017
0.062
0.288
1.00

GL
0.153
0.342
−0.270
−0.334
−0.068
−0.012
−0.244
−0.595
−0.258
1.00

GB
0.152
0.409
0.014
0.004
0.204
−0.101
0.064
−0.335
−0.018
0.148
1.00

GLB
0.047
0.048
−0.237
−0.286
−0.190
0.049
−0.264
−0.312
−0.239
0.763
−0.511
1.00

PB No.
0.413
0.115
0.168
0.160
−0.140
−0.231
0.135
0.081
0.053
−0.060
−0.020
−0.055
1.00

PBL
−0.285
0.085
−0.204
−0.171
0.359
0.243
−0.229
0.218
−0.071
0.039
−0.043
0.083
−0.383
1.00

SB No.
−0.116
−0.218
0.038
0.075
0.107
0.044
−0.013
0.784
0.351
−0.534
−0.301
−0.267
0.011
0.345
1.00

SBL
−0.109
0.125
−0.299
−0.316
0.093
0.268
−0.198
0.115
0.032
0.286
−0.087
0.295
−0.319
0.598
0.283
1.00

TGW
0.108
0.479
−0.041
−0.058
0.200
−0.066
−0.154
−0.491
−0.421
0.651
0.501
0.249
−0.245
0.266
−0.445
0.250
1.00

YP
0.143
0.042
0.407
0.431
0.190
0.118
−0.023
0.267
−0.141
−0.001
0.016
−0.003
−0.073
0.324
0.231
0.324
0.258
1.00

HI
−0.140
−0.152
0.025
0.043
0.056
0.048
−0.216
0.343
0.008
−0.194
−0.282
0.034
−0.120
0.390
0.436
0.324
−0.112
0.545
1.00

and indicate significance at 1% and 5% level of probability, respectively.

CD: culm diameter (mm), FLA: flag leaf area, DF: days to flowering, DM: days to maturity, PL: panicle length, ET No.: effective tiller number, PH: plant height, FGP: filled grains per panicle, UFGP: unfilled grains per panicle, GL: grain length, GB: grain breadth, GLBR: grain length breadth ratio, PB No.: primary branches per panicle, PBL: primary branch length, SB No.: secondary branches per panicle, SBL: secondary branch length, TGW: 1000-grain weight, YP: yield per plant, and HI: harvest index.

3.3. Principal Component Analysis (PCA)

Eigen values (latent roots) of 19 principal component axes and percentage of total variation accounted for them obtained from component analysis are presented in Table 7. The result revealed that the first axis largely accounted for the variations observed among the genotypes (48.8%) followed by the second axis (10.37%). The first nine axes accounted for about 90% of the total variations among the 19 characters describing 113 aromatic and fine rice genotypes where only 59.17% variation was accounted for the first two axes.

Table 7: Latent roots (eigen values) and their variation in 19 quantitative characters in 113 aromatic and fine rice genotypes.

Principal component axes
Latent roots
Variation (%)
Cumulative% of variation

I
2.731
13
48.8

II
2.178
10.37
59.17

III
1.613
7.68
66.85

IV
1.219
5.81
72.66

V
1.01
4.81
77.47

VI
0.791
3.76
81.23

VII
0.669
3.19
84.42

VIII
0.654
3.12
87.54

IX
0.551
2.62
90.16

X
0.476
2.26
92.42

XI
0.372
1.77
94.19

XII
0.293
1.4
95.59

XIII
0.258
1.23
96.82

XIV
0.22
1.05
97.87

XV
0.176
0.84
98.71

XVI
0.151
0.72
99.43

XVII
0.096
0.46
99.89

XVIII
0.014
0.08
99.97

XIX
0.007
0.03
100

3.4. Cluster Analysis

The pattern of distribution of 113 aromatic and fine rice genotypes were grouped into 10 clusters shown in Table 8. The number of genotypes ranged from 3 to 19 in different cluster. The distribution pattern indicated that the maximum number of test genotypes (19) was grouped into the cluster I followed by 18 in clusters VIII, 17 in clusters III, 13 in clusters IV, 11 in clusters II, 10 in clusters X, 8 in clusters V and IX, and 6 in cluster VII. Cluster VI contained the lowest (3) number of genotypes.

Table 8: Distribution of 113 aromatic and fine rice genotypes into ten clusters.

Cluster
Number of genotypes
% total
Name of genotypes

I
19
16.81
Nunia, Chini Sagar (), Tilkapur, Kalobhog, Jabsiri, Chinisakkor, Noyonmoni, Tulsimoni, Khirshabuti, Gua masuri, Rajbhog, Baoijhaki, Tulsimala, Desikatari, Thakurbhog, Tulsimaloty, Radunipagal, Khasa, and Kataribhog

II
11
9.73
Begun bichi, Elai, Bashmati 370, Sugandhi dhan, Khazar, Basmati Sufaid 106, BRRI dhan50, Basmati 37, Basnatu sufaid 187, BU dhan2R, and Bashful

III
17
15.04
Jirabuti, Soru kamina, Kamini soru, Doiarguru, Luina, Kalijira (short grain), Philliphine kataribhog, Jirabhog (Bolder), Uknimodhu, Jira dhan, Badshabhog, Kalijira (long grain), Jesso balam, Dakshahi, Straw, Dubsail, and Sunduri samba

IV
13
11.50
Sagardana, Kalgochi, Chiniatob, Gopalbhog, Hatisail, Buchi, BRRI dhan38, Gordoi, Basmati, Padmabhog, Oval TAPL-2990, Kalijira TAPL-74, and Kalobakri

V
8
7.08
Saubail, Begunmala, Rajbut, Ranisalut, Gandhakusturi, Jirakatari, Awned TAPL-545, and Black TAPL-554

VI
3
2.65
Sakkorkhana, Kalijira TAPL-64, and Kalijira TAPL-68

VII
6
5.31
Chini Kanai, Chinigura, Khaskani, BRRI dhan34, BRRI dhan37, and Chinisail

VIII
18
15.92
Chinniguri, Premful, Baoibhog, Sakkorkhora, BR5, Uknimodhu, Chiniatob-2, Begunbichi-2, Bhatir cikon, Dolagocha, Dhan chikon, Badshabhog-2, Malshira, Sadagura, Chinikanai, Meedhan, Gobindhabhog, and Fulkari

IX
8
7.08
Sakor, Binnaphul, Lal Soru, Duksail, Tilokkachari, Chinairri, Kalonunia, and Thakurbhog-2

X
10
8.85
Meny, Kalomala, Khasa Mukpura, Bawaibhog-2, Khuti chikon, Tulsimala-2, Modhumadab, Parbatjira, Dudsail, and Maloti

Results of 10 higher and 10 lower intergenotypic distances estimated from distant matrix of Principal Coordinate Analysis are shown in Table 9. Highest intergenotypic distance was 2.274 observed between Gopalbhog and Kalobakri followed by the distance of 2.126 observed between Haitsail TAPL101 and Kalobakri. The 10th highest distance of 1.522 was observed between Jirabuti and Straw TAPL554 followed by 1.528 observed between Ranisaluit and Jirakatari. The lowest distance was calculated (0.299) between Doiagura and Jiradhan followed by the distance of 0.301 observed between Kamini soru and Jirabhog (bolder).

Table 9: Ten higher and ten lower intergenotypic distances among the 113 aromatic and fine rice genotypes.

Sl. No.
Genotypic combination
Distances

(a) Ten higher intergenotypic distance

01
Gopalbhog-Kalobakri
2.274

02
Haitsail TAPL101-Kalobakri
2.126

03
Buchi-BU dhan 2R
1.836

04
Kalgochi-Kutichikon
1.832

05
Begun Mala-Elai
1.779

06
BRRI dhan50-Bashful
1.632

07
Elai-Khazar
1.589

08
Khasa Mukpura-Dudsail
1.580

09
Ranisalut-Jirakatari
1.528

10
Jirabuti-Straw TAPL-554
1.522

(b) Ten lower intergenotypic distance

01
Doiagura-Jiradhan
0.299

02
Kamini soru-Jirabhog (bolder)
0.301

03
Kutichikon-Parbatjira
0.318

04
Chinisagor ()-Khasa
0.321

05
Tilkapur-Guamasuri
0.333

06
Kalobhog-Noyonmoni
0.341

07
Noyonmoni-Rajbhog
0.356

08
Chinisagor ()-Jabsiri
0.361

09
Jabsiri-Chinisakkor
0.362

10
Tilkapur-Kalobhog
0.374

Intra- and intercluster distances value are presented in Table 10. There were marked variations in intracluster distances which ranged from 0.61 in cluster VI to 1.27 in cluster II indicating homogeneous nature of the genotypes within the cluster. The highest intracluster distance was computed for cluster II (1.27) which was comprised of eleven genotypes followed by cluster IV (1.01) with thirteen genotypes. The genotypes under cluster II (with the highest intracluster mean) were most heterogeneous and genotypes under cluster VI (with the lowest intracluster mean) were comparatively homogenous.

Table 10: Average intra- (bold) and intercluster distances () for 113 aromatic and fine rice genotypes.

Cluster
I
II
III
IV
V
VI
VII
VIII
IX
X

I
0.68
7.499
3.710
4.274
4.807
7.332
3.975
7.592
4.895
12.119

II

1.27
9.438
7.161
8.645
10.77
9.681
12.206
9.087
15.791

III

0.65
6.288
7.713
6.876
4.332
4.799
3.775
9.087

IV

1.01
4.46
6.946
5.365
8.983
4.908
13.609

V

0.96
9.198
6.713
11.435
7.951
16.116

VI

0.61
7.524
7.896
6.498
10.93

VII

0.75
6.461
5.036
11.064

VIII

0.71
4.78
5.294

IX

0.79
9.256

X

0.90

The intercluster distances ranged from 3.710 to 16.116. Regarding the intercluster distance, the highest value was found between clusters V and X (16.116) followed by clusters II and X (15.791) and so on. On the other hand, the lowest intercluster distance was observed between clusters I and III (3.710) followed by clusters III and IX (3.775) indicating that genotypes of these clusters were genetically closed.

The mean values for all of 19 characters along with the marking of the highest () and lowest () for each of the cluster are presented in Table 11. Differences in cluster means existed for almost all the characters. Genotypes of cluster VI produced the highest mean for days to flowering (DF), days to maturity (DM), plant height (PH), and yield per plant (Y/P). Genotypes in cluster II had higher mean values for flag leaf area (FLA), secondary branch length (SBL), grain length (GL), grain length breadth ratio (GLBR), and 1000-grain weight (1000). Higher mean values for panicle length (PL), secondary branches per panicle (SB No.), filled grains per panicle (FG/P), and harvest index (HI) were recorded in cluster X whereas those for effective tiller (ET No.) per plant and grain breadth (GB) were recorded in cluster IV.

Table 11: Cluster means for 19 quantitative characters in 113 aromatic and fine rice genotypes.

I
II
III
IV
V
VI
VII
VIII
IX
X

CD (mm)
4.57
4.75
4.97
4.53
4.61
5.86 (H)
4.42
4.16 (L)
4.2
5.08

FLA (cm³)
33.37
43.25 (H)
35.12
35.77
36.82
40.16
33.45
33.89
30.95 (L)
34.2

DF
101
90.33 (L)
102.5
107.56
106.75
120.11 (H)
107.8
104.7
103.7
104.03

DM
130.1
118.2 (L)
131.1
136.13
135.12
146.67 (H)
135.8
133.7
132.9
133.07

PH (cm)
152
125.2 (L)
158.4
138.5
157.56
168 (H)
131.2
143.7
142.1
146.39

ET No.
9.99
9.15
9.08 (L)
10.44 (H)
10.33
9.19
9.92
10.21
9.96
9.8

PL (cm)
28.67
27.57
28.56
28.99
28.81
27.95
27.4 (L)
28.98
28.85
29.28 (H)

PB No.
10.67
9.80 (L)
10.85 (H)
10.15
9.82
11.22
10.58
9.83
10.61
10.4

PBL (cm)
10.25
11.28
10.11 (L)
10.85
10.26
10.15
10.45
11.42 (H)
11.02
11.40

SB No.
28.38
22.96
35.44
23.83
18.97 (L)
25.78
37.56
42.53
34.06
49.5 (H)

SBL (cm)
2.72
3.03 (H)
2.65
2.61
2.60 (L)
2.58
2.74
2.83
2.65
2.99

FG/P
135.5
98.84 (L)
162.9
125.96
102.69
158.11
156.3
198.3
162.2
232.2 (H)

UFG/P
53.41
28.3
51.78
27.46
43.45
13.89 (L)
65.44 (H)
47.91
28.91
46.31

GL (mm)
7.36
9.67 (H)
6.81
7.26
7.71
6.34
6.57
6.13 (L)
6.61
6.32

GB (mm)
2.31
2.33
2.36
2.42 (H)
2.84
1.89 (L)
2.36
2.21
2.34
2.13

GLBR
3.21
4.28 (H)
2.91
3.12
2.81
3.36
2.8
2.79 (L)
2.91
3.0

TGW (g)
11.83
19.03 (H)
11.59
15.49
17.46
12.28
11.02 (L)
11.16
13.17
11.25

YP (g)
11.02 (L)
11.59
11.96
13.29
11.78
14.06 (H)
13.94
12.77
12.42
13.60

HI
0.22
0.22
0.23
0.24
0.21 (L)
0.23
0.26
0.25
0.24
0.27 (H)

CD: culm diameter (mm), FLA: flag leaf area, DF: days to flowering, DM: days to maturity, PH: plant height (cm), ET No.: effective tiller number, PL: panicle length (cm), PB No.: primary branches per panicle, PBL: primary branch length (cm), SB No.: secondary branches per panicle, SBL: secondary branch length (cm), FGP: filled grains per panicle, UFGP: unfilled grains per panicle, GL: grain length (mm), GB: grain breadth (mm), GLBR: grain length breadth ratio, TGW: 1000-grain weight (g), YP: yield per plant (g), and HI: harvest index.

4. Discussion

During the current study, all traits showed highly significant () variations among 113 accessions, which originated in Bangladesh except Khazar, Basmati 37, Basmati 370, Basmati Sufaid 106, and Basmati Sufaid 187 genotypes. Our results are in close agreement with those of Pandey et al. [34] who recorded highly significant variability among the different rice genotypes. Similarly the finding of Wang et al. [35] also gives support to the current findings. The findings of Chandra et al. [36] and Abarshahr et al. [37] further strengthen the current findings, who also found valuable and highly significant and positive variability among their studied genotypes.

The dependence of grain yield on other traits has been reported for many crops [38]. As mentioned, in this study, yield of plant had positive correlation with 8 quantitative traits. Lasalita-Zapico et al. [39] studied correlation coefficient of 10 quantitative traits for 32 upland rice varieties. In this distinguished significant positive correlation the majority of the morphological traits was recorded except flag leaf angle that had negative correlation with most of characters such as panicle length, leaf length, leaf width, ligule length, leaf area, and culm length. In our studies, grain yield positively correlated with panicle length. The findings indicate that plants with high panicles have high number of filled grains thereby increasing rice yield. Similar correlations were reported by Zafar et al. [40].

The calculation of heritability and genetic advance are used to help the breeder to select traits that are highly heritable as compared to a trait which is less heritable [33]. Both high heritability and genetic advance value obtained in this study, flag leaf area, secondary branches per panicle, filled grains per panicle, grain length, grain breadth, length breadth ratio, and 1000-grain weight indicated reasonable variation for this traits. This suggests that selection can be easily practiced by using these traits to improve grain yield in aromatic rice genotypes. The results support the findings of Sedeek et al. [41], Laxuman et al. [42], and Pandey et al. [34] who reported such type of heritability in rice.

In the present study, 113 aromatic and fine rice genotypes were clustered into ten groups based on 19 quantitative traits. This result supports the findings of Singh et al. [43] and Rao et al. [44] who reported ten clusters in rice genotypes. Ahmadikhah et al. [38] clustered 58 rice varieties into four groups based on 18 morphological traits and genetic distance was around 0.75. Group A was comprised of only one genotype and groups B, C, and D contained 14, 20, and 23 genotypes, respectively. Veasey et al. [45] computed clustering for 23 populations of rice by 20 morphological characteristics. So the varieties were clustered into 10 groups; the last group was the biggest group with seven members and groups 1, 2, 7, and 8 were the smallest groups including only one variety. So, genotypes having distant clusters could be hybridized to get the higher heterotic responses. The similar findings were also reported in a number of previous studies [18, 46–48].

Principal component analysis indicated diversity among 113 aromatic and fine rice genotypes. “Proper values” measure the importance and contribution of each component to total variance, whereas each coefficient of proper vectors indicates the degree of contribution of every original variable with which each principal component is associated. The higher the coefficients are, regardless of the direction (positive or negative), the more effective they will be in discriminating between accessions. In the present study, the first three axes accounted for about 66% of the total variations. Lasalita-Zapico et al. [39] computed approximately 82.7% of total variation among 32 upland rice varieties, 66.9% variation for PC1, and 15.87% for PC2. Rajiv et al. [49] reported the first two principal components accounting for 82.1% of total variation in control and 68.6% in the stress induced genotypes. To obtain greater heterosis, genotypes having distant clusters could be used as parents for hybridization program. In Bangladesh, most of the aromatic rice genotypes are traditional, photoperiod-sensitive, tall stature, and lower yields with mild to strong aroma and also they showed high variability (6, 28). In the present study, it was observed that the genotypes in clusters V and X (16.116) were more diverse than the genotypes of clusters I and III (3.710). Considering cluster distance and cluster mean, the highest mean value for panicle length (cm), secondary branch length (cm), filled grains per panicle, and harvest index was observed in cluster X, which means that those traits might be selected for their high heterosis. Therefore, selection of parents for hybridization program from clusters V and X may result in the desirable heterosis for heterotic rice hybrids. Genotypes under cluster II may also give higher heterosis, if crossing is done within the genotypes of this cluster due to high value of intracluster distance.

5. Conclusion

In the present study, flag leaf area, secondary branches per panicle, filled grains per panicle, grain length, grain breadth, grain length breadth ratio, and 1000-grain weight showed high heritability and high genetic advance in percent of mean had high heritability and high genetic advance. Yield of plant had positively correlated with days to flowering, days to maturity, panicle length, filled grains per panicle, and 1000-grain weight. The cluster analysis placed 113 aromatic and fine rice genotypes into ten groups. The highest intercluster distance was observed between clusters V and X followed by clusters II and X. The maximum value of intercluster distance indicated that the genotypes belonging to cluster V were far diverged from those of cluster X. So, it is expected in our results that parent’s selection for hybridization from the clusters V and X may give the desirable heterosis for heterotic rice hybrids. Finally, molecular characterizations of the studied germplasm are required for high resolution QTL mapping and validating the presence of candidate genes responsible for valuable characters.

Competing Interests

The authors declare that they have no competing interests.

Acknowledgments

The authors are highly grateful to the collaborative research project entitled “Genetic Enhancement of Local Rice Germplasm towards Aromatic Hybrid Rice Variety Development in Bangladesh” funded by the NATP: Phase I of PIU, Bangladesh Agricultural Research Council (BARC), for providing all necessary supports.

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