Songklanakarin J. Sci. Technol. 38 (5), 495-500, Sep. - Oct. 2016 http://www.sjst.psu.ac.th Original Article New data on the domestication of the two subspecies indica and japonica of the Asian cultivated rice (Oryza sativa) during the Dvaravati Period in Thailand and Lao PDR Preecha Prathepha* Department of Biotechnology, Faculty of Technology, Mahasarakham University, Kantharawichai, Maha Sarakham, 44150 Thailand. Received: 21 October 2015; Accepted: 21 January 2016 Abstract Rice hull imprints on bricks of the Dvaravati Period from four historical sites in Thailand and Lao PDR were measured and classified. In addition, a collection of traditional rice landraces from northern, central, northeastern regions of Thailand, Lao PDR, Vietnam and Cambodia were used to examine rice grain shapes and to test phenol reaction response of rice hulls. The results show that rice hulls in bricks from the Dvaravati Period may be classified into three types of cultivated rice grain shapes, i.e., round, large, and slender types. With the combined methods in archaeology, physiology and ecotype, the present domesticated rice landraces have been combined and by implication, can be possibly traced to types of rice in the Dvaravati Period. It is now suggested that the subspecies indica and japonica of Asian cultivated rice were domesticated at that time. Keywords: rice domestication, historical sites, Dvaravati Period 1. Introduction Rice cultivation in mainland Southeast Asia rice appears by 2000 BC, especially associated with the lower reaches of the The Asian cultivated rice (Oryza sativa L.) may have Red River (Vietnam), the Mekong River (Cambodia) and Chao been domesticated from the wild progenitor (O. rufipogon) Phraya (Thailand) (Fuller et al,. 2010). Based on fundamental dated approximately 10,000-20,000 BP (Jiang and Liu, 2006; questions of when rice cultivation began in Thailand archaeo- Wu et al., 2012). Based on morphological, biochemical, and logical evidence for rice cultivation have been studied at three molecular data, Asian cultivated rice is classified into two archaeological sites (i.e., Pung Hung cave in the northern, subspecies, i.e. japonica and indica (Oka and Morishima, Non Nok Tha in the northeastern, and Kok Phanom Di in the 1982). In eco-geographical terms, the subspecies indica have central region). It appears that around 1,800 to 2,500 years grown throughout tropical Asia at low latitudes and low ago rice cultivation originated in Thailand (Bayard, 1970; elevations, while the subspecies japonica are typically found Solheim, 1970; Watabe et al., 1970). in temperate East Asia, Southeast Asia, and South Asia at Watanabe et al. (1963) reported grain morphology high latitudes and high elevations (Cai et al., 2007). Rice from rice husk contained in bricks of cultivated rice distri- scientists now accept that rice was originally domesticated buted in Thailand during four periods (6th-11th, 11th-15th, 15th- at the Yangtze River area in China (Gross and Zhao, 2014). 18th, and after the 18th century). Grain types were classified into three types, i.e. round, slender, and large types. During the 6th-11th centuries (i.e., Dvaravati Period) in Thailand, rice * Corresponding author. grains with three types were found, with the round type as the Email address: [email protected]; dominant type. In this report, the round type is designated [email protected] as “japonica” or “japonica-like” rice, while the large type of 496 P. Prathepha / Songklanakarin J. Sci. Technol. 38 (5), 495-500, 2016 grains are of the upland variety and are presumably of the domesticated in the Dvaravati Period of Thailand. It is glutinous upland variety. For the slender type, most of the proposed that the study of the morphology of rice grains varieties were probably of the non-glutinous lowland variety. through the comparison of grain morphology of old speci- It is not unlikely that the round type belonged to the gluti- mens with those of the present varieties or rice landraces will nous-lowland variety. This means that the rice grown since identify the specimens of each type and reconstruct the long the 6th century was both glutinous (large type) and non- history of rice-growing societies in Thailand. Thus, the objec- glutinous (slender type). tives of the present study are to classify the grain morpho- Oka and Chang first reported a japonica type of logy of rice hulls imprinted on bricks dated to the Dvaravati cultivated rice found in northern Thailand (Oka and Chang, Period and to survey the phenol response in traditional rice 1963). These rice varieties consisted of both glutinous and landraces and then to determine whether the associations non-glutinous rice. From the geographical distribution, it between grain morphology and the phenol response can be became apparent that the indica type was grown in lowlands, demonstrated in the two subspecies indica or japonica. whereas the japonica type was found in high altitude areas (Vaughan et al., 2008). 2. Materials and Methods Japonica is now subdivided into two subgroups called temperate japonica and tropical japonica or javanica During 2014-2015, several surveys were conducted (Oka, 1988). Temperate japonica rice varieties are distributed to search for bricks that contained molds (or imprint) of rice mainly in the islands of Western Pacific, from Indonesia to grains at selected historical sites in Thailand and Laos PDR. Japan, and in certain parts of the continent in China and Some bricks were collected or their photographs taken from Korea, while tropical japonica rice varieties are distributed on three historical sites of Thailand, all of which are registered mountainous regions at low medium elevations in equatorial at The Fine Arts Department: the Phrathatyaku (No.0003338, area (Oka and Chang, 1963). These two subspecies of Asian 16°19’12"N, 103°31’12"E) in Kalasin province; Umyaku cultivated rice can be distinguished using classical diagnos- (No. 0002909, 16°18’36"N, 103°18’00"E) in Mahasarakham tic traits, including seedling resistance to KClO3, seedling province, both in the northeastern region; and Uthong survival in cold temperatures, grain apiculus hair length, and ancient city (No. 0004914, 14°22’12"N, 99°53’24"E) in phenol reaction (Morishima et al., 1992). The phenol reaction Suphanburi province, central region. In the Lao PDR, some test showed that rice hulls and grains turn dark in color after bricks of the Old Vientiane Wall (17°54’05"N, 102°39’03"E), exposure to a 1-2% aqueous phenol solution; japonica type registered at the Department of Information and Culture in the showed no color change (or a negative response), whereas Vientiane capital, were sampled and photographed. Figure 1 the hull of indica type showed positive response (i.e., a color shows the specimens of imprints of rice husk on bricks from change from yellow to dark brown or black) (Oka and Chang, these historical sites. In addition, a collection of rice landraces 1961). from northern, central, northeastern regions of Thailand, Lao Dvaravati is a culture that the Dvaravati Culture were PDR, Vietnam and Cambodia were used to examine phenol regarded as the first historic culture of present-day Thailand reactions of rice hulls. Samples of 20 rice hulls found in a and has been roughly dated to c. 600-1,000 CE and it is clear cave of an archeological site in Lao PDR were used to analyze that the Dvaravati Period marked a period of cultural growth, grain shape and to examine the phenol reaction. Rice hull social complexity, and incipient urbanization ranging from shapes (length and width and L/W ratio) were analyzed by locations such as Thung Sethi in the upper peninsula, north using VISA Lab’s A-VIS 4.0 (Amornsin, A. 2008. VISA Lab’s to Nakhon Pathom, U-Thong, and then across the central AVIS Software, Mahasarakham University, Thailand, personal plains into the Korat Plateau in the northeast (Glover, 2011). communication). In each of the historical site, 25 good shapes Around 257-357 CE, the communities in the area of the Chao Phraya River developed the highest civilization in the region, with easy access to the sea and settling in a habitat in a river basin suitable for agriculture (Glover, 2011). Since 1968, no investigation had been conducted so far to identify which subspecies of these rice grains had been cultivated during the Dvaravati Period. It is therefore of particular interest to classify the Asian cultivated rice at the subspecies level. Archaeological evidences would address big questions about the past that in most cases cannot be ascertained as written records are absent or limited. This study allows us to formu- late a tentative hypothesis that can be further explored and makes some general conclusions on the history of rice agri- culture in Thailand. Half a century of scientific research has reached no Figure 1. Example of imprints of rice husks on bricks from four conclusions on the subspecies of cultivated rice which were historical sites dated to the Dvaravati Period. P. Prathepha / Songklanakarin J. Sci. Technol. 38 (5), 495-500, 2016 497 of rice hulls imprinted on bricks and 20 rice hulls from a cave width from 1.8 mm to 3.4 mm. The length/width ratio of these in a historical site in Lao PDR were selected to measure grain rice husks examined ranged from 2.42 to 4.5 (Table 1). It is length and width. The ratios of length to width were calcu- suggested that the rice husks examined may be divided into lated and grain shapes were then classified into round (short), three types, i.e. round, large and slender types, each cor- large (medium) and slender (long) types, based on the responding to japonica-like rice, tropical japonica and methods formulated by the International Rice Research indica, respectively.