Rice Genetics Newsletter, Vol. 18

Rgn18

19.	Variation of three important starch characters in Myanmar local rice cultivars for cooking and eating quality
	PA PA AUNG, T. KUMAMARU and H. SATOH Laboratory of Plant Genetic Resources, Kyushu University, Faculty of Agriculture, Hakozaki, Fukuoka, 812-8581 Japan

The cooking and eating quality preferences vary with the country (Azeez and Shafi, 1966). Gelatinization temperature, amylose content and gel consistency are important starch properties in rice, because these traits influence the cooking and eating characteristics.

In the present study, the magnitude of variations in three starch characters among the Myanmar local rice cultivars were investigated to make a breeding program for improving grain quality of rice.

One hundred and fifty local rice cultivars from six distinct regions, provided by the Seed Bank of Myanmar, were analyzed. The alkali spreading score was measured for each grain using the method of Little et al. (1958). Amylose content was estimated by using the DU

7500 spectrophotometer (Beckman) according to Satoh et al. (1990). The gel consistency was determined using the method of Cagampang et al. (1973).

Alkali digestibility score is the indicator determining the cooking quality because of its close linkage with gelatinization temperature of starch. Of the 150 cultivars, 94 showed low scores for alkali digestibility ranging from 1 to 3,53 showed intermediate scores ranging from 4 to 6, and 3 showed high scores ranging from 7 to 9 (Table 1). Most of Myanmar local rice cultivars were more resistant and undecomposable to alkali.

Amylose contents of Myanmar local rice cultivars ranged from 0 to 30% (Table 2). A wide range of regional variation in amylose content was observed.

Varieties having same amylose content may differ in tenderness and therefore, the cooked rice may be differentiated by the gel consistency test (Cagampang et al., 1973). The gel consistency test is based on the consistency of rice paste. A wide range of variation in gel consistency value among Myanmar local rice cultivars was also found, ranging from 5 to 100 mm (Table 3). Myanmar local rice cultivars were different in cooked rice texture and their patterns of consumer tastes and preferences also varied widely.

These results indicate that Myanmar rice genetic resource is very wide for the three starch characters. This is due to that Myanmar has a wide range of the agroecological condition and ethnological complexity. A wide range of regional variation in three starch characters among the Myanmar local rice cultivars is valuable for the grain quality improvement as a breeding material.

References

Azeez, M.A., and M. Shafi, 1966. Quality in rice. Dep. Agr. West Pakistan Tech. Bull. No. 13 pp 50.

Cagampang, G.B., C.M. Perez and B.O. Juliano, 1973. A gel consistency test for eating quality of rice. J. Sci. Food Agr. 24: 1589-1594.

Little, R.R., G.B. Hilder and E. H. Dawson, 1958. Differential effect of dilute alkali on 25 varieties of milled white rice. Cereal Chem. 35: 111-126.

Satoh, H., H.M. CHING' ANG' A, D. ILAILA and T.C. Katayama, 1990. On amylose content of cultivated rice collected in Tanzania, 1998. Kagoshima Univ. Res. Center S. Pac., Occ. Papers, 18: 92-100.