Variation in seed morphology of Sang Yod rice variety from southern Thailand

Abstract

Rice variety “Sang Yod” has become popular among health-conscious consumers as it has premium cooking quality and provides a rich source of nutrients. Difference in grain morphology are commonly observed by consumers, particularly the presence of opaque seed within and between populations collected from different fields. This study evaluated the variation in seed morphological characteristics of Sang Yod from southern Thailand. Samples (22) of Sang Yod rice were collected from farmer’s fields in Nakhon Si Thammarat, Phatthalung and Songkhla provinces. Seeds of each sample were planted to evaluate seed morphological characters, including pericarp color, seed size, seed shape, 100 seed weight, whiteness, translucency, endosperm type, and the percentage of opaque and translucent seed. Variation in seed morphology was found within and between populations collected. The diversity index (H’) of pericarp color observed by naked eyes ranged from 0 to 0.3. The proportion of opaque and translucent seeds in milled rice also differed among the samples collected. There was wide variation in seed weight among samples, ranging from 1.61 to 1.83 g for paddy rice and from 1.24 to 1.43 g for brown rice. After separated into opaque and translucent grain, the seed weight of the opaque grain was significantly lower than translucent grain for all samples, but there was no difference in seed size. For brown rice, there was a positive relationship between 100 seed weight and the percent of translucent seed (r=0.50, P<0.05), whereas there was a negative relationship between 100 seed weight and the percentage of opaque seed (r=-0.50, P<0.05). The same relationships were also found in paddy rice. The loss of seed weight in the presence of the opaque character affects the net price of rice and it may also have a negative effect on rice grain quality. Investigation into the seed structure is needed to determine the underlying anatomical causes of opaque and translucent seed characters in Sang Yod.