157cultural practices that can influence its contents.3 .4 Amino acid content and Amino acid score
Box plot showing distribution of various amino acids
in 42 high yielding rice cultivars is shown in Figure 1.
The total essential amino acids made up 39% of the
total amino acids. Lysine content ranged from
3.42g/100g in AP 41 Kanchana to 4.2g/100g in AP 71
Pratap with a mean of 3.76 ± 0.20 g/100g protein.
Shekar and Reddy (1982) has also reported wide vari-
ation in lysine content (2.82 to 4.86g/100g protein) in
scented rice varieties. In contrast low lysine content
(2.8g/100g protein) was observed in Mexican and
Malaysian rice varieties (Roohinejad et al 2009; Sotelo
et al, 1994). In the present study besides AP71 Pratap
another two varieties AP 8 5 Sarala and AP106 also
had lysine content above 4 g/100g protein. Wide ge-
netic variability for lysine content in Indian rice vari-
eties has been reported (Banerjee et al, 2011). The
mean ± SD of threonine content, the second limiting
amino acid in rice was 3.45 ± 0.21 g/100g protein. The
lowest threonine content of 3.03 g/100g protein was
observed in IR 64 while the highest content of 3.86
g/100g protein was found in AP 85 Sarala. After lysineand threonine, isoleucine is the only amino acid that
can sometimes be limiting in rice protein. Isoleucine
content ranged from 3.02 – 4.59 g/100g protein with
mean content of 3.91 ± 0.39 g/100g protein. The
savoury amino acids glutamate and aspartate was the
major amino acids constituting 19.36 ± 0.39 and 8.91
± 0.38 g/100g protein respectively. The sweet amino
acids glycine and alanine was as high as 4.51±0.20
and 6.01±0.29 g/100g protein respectively. The range
of the different essential amino acids expressed in
g/100g protein was 1.32 – 1.54 for tryptophan, 1.51 –
3.04 for cysteine, 4.05 – 6.92 for valine, 1.11 – 2.40 for
methionine, 7.23 – 8.73 for leucine, 5.12 – 5.75 for
phenylalanine, 2.23 – 2.73 for histidine and 7.53 – 8.6 2
for arginine. There was reasonable level of variation
for all the amino acids indicating that genetic gain by
means of selection is likely.
Compared to the WHO/FAO/UNU (1985) amino acid re-
quirement for 2-5 years old child the amino acid score
ranged from 59 to 73 with a mean of 65 ± 3.42. Com-
pared to lysine content in rice varieties from other
studies (Hegsted and Julaino 1974; Sotelo et al 1994;
Tobekia et al, 1981), generally higher lysine content
was observed in the present study. Despite observingTable 5. Correlation among amino acids and protein content in 42 high yielding Indian rice cultivars
Try Asp Thr Ser Glu Pro Gly Ala Cys Val Met Ile Ley Tyr Phe His Lys Arg
Asp 0.368*
Thr 0 .175 0. 800
Ser 0.21 5 0.7 5 6 0.84 5
Glu 0.126 0.1 37 0.146 0. 3 90*
Pro 0.222 -0.076 -0.0 54 0.11 5 0.264
Gly 0.199 0.742 0.816 0.581 0.009 -0.214
Ala 0.149 0.711 0.8 3 2 0.681 0.227 -0.224 0.794
Cys 0.466 0.513 0.412 0.455* 0.147 0.042 0.332 0.412
Va -0.0 33 -0. 5 49 -0.490 -0. 5 21 0.060 0.211 -0. 35 7 -0. 3 91 -0.14 3
Met 0. 3 29* 0. 55 8 0. 5 24 0.446 0.141 0.200 0. 5 12 0.4 5 0* 0. 33 0 -0.26 4
Ile 0.14 5 -0.274 -0.249 -0.488 -0.1 55 -0.012 -0.040 -0.090 0.060 0.7 35 -0.042
Ley 0.012 0-.503 -0.487 -0.375* 0.280 0.261 -0.474* -0.381 0.002 0.905 -0.309 .564
Tyr 0.434 0.313 0.169 0.228 0.373 0.120 0.139 0.264 0.313 -0.208 0.286 0.138 -0.073
Phe 0. 303 0.022 -0.071 -0.067 0. 3 47* -0.02 5 0.1 50 0.102 -0.011 0.4 53 0.049 0.420 0.416 0. 3 64
His 0.190 0.430 0.486 0.193 -0.123 -0.200 0.570 0.403 0.277 0.094 0.336 0.435 -0.012 0.032 .0208
Lys 0.044 0.343 0.333 0.081 -0.354* -0.075 0.413 0.199 0.257 0.234 0.278 0.419 0.041 -0.134 0.127 0.603
Arg 0.242 0.204 0.241 0.200 -0.025 0.159 0.357 0.047 0.101 0.108 0.353 0.188 -0.010 0.248 0.186 0.251 0.405
Protein -0.281 -0.789 -0.676 0-.475 0.173 0.225 -0.658 -0.620 -0.310 0.843 -0.557 0.286 0.881 -0.452* 0.206 -.0332 -0.169 -0.17 4
*. Correlation is significant at the 0.05 level (2-tailed). **. Correlation is significant at the 0.01 level (2-tailed).