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THOUGHTS ABOUT THE DOMESTICATION OF RICE Liu, Zh iyi, Zhuzhou Industry Institute, Zhuzhou, Hunan Province:PR Ch ina (Agricultural Archaeology 2000(1):122-128. Transl. by Li Lin; ed. by B. Go rdon) 1. An issue worth notice: manner of domestication There is no single solution on the origin of paddy rice agriculture because it involves many factors, rice origin, and farmers and their planting, environ ment and period. Fortunately, researchers of rice historiography, archaeology, biology, molecular genetics, historical geography, palaeoclimatology and linguistics are consistent on common issues; e.g., cultivated rice derives fro m co mmon wild rice ( Oryza sativa f. spontanea Roschev), not medicinal or verrucous wild rice ((Oryxa officinalis Wall or Oryza meyeriana Baill). Its orig in is not India but Ch ina on the middle Yangtze River, not Yungui Antiplano, etc. But many variat ions remain on some issues; e.g., some insist perennial co mmon wild rice first evolved to annuals before domestication (Zhang Deci, 1981)(1). Others think the perennial was direct ly domesticated to cultivated rice, with annual wild rice a hybrid of perennial wild and cultivated rices (Gang Yanyi, 1988) (2). Later, Y. Sano, Hiroko Morishima and Hilo-Ishi Oka discovered osculant common wild rice in Thailand midway between perennial and annual common wild rice, concluding cultivated rice derives fro m osculant common wild rice (Sano, 1980)(3). Others have different opinions on indica and japonica origins of cultivated rice; e.g.s, (a ) both are monogenetic (monophyletic); i.e., co mmon wild rice and hu man habitation differ due to diverse climate and environment at different latitudes and elevations. Co mmon wild rice does not differentiate into indica and japonica (Gang Yanyi, 1988)(4) ; (2) both are genetically independent, indica from India (Second, G. 1982)(5), japonica from China. But, isoenzy me and molecular genetics of Chinese perennial rice shows common wild rice has indica and japonica differentiation, but it is tiny and elementary co mpared to cultivated rice (Wang Xiangkun et al., 1994)(6). Research on 10,800 year-o ld ancient Yuchanyan site cultivated rice fro m Dao County, Hunan Province, shows ancient cultivated rice with wild, indica and japonica traits (Zhang Wenxu & Yuan Jiarong, 1998)(7). Some issues appear to agree but are not fully understood, e.g., change fro m wild to cultivated rice. Researchers now believe rice was first planted by direct sowing, but replaced by seedling transplant due to disease, low unstable productivity, etc. (Chinese Rice Science, ed. by Chinese Agricultural & Scientific Institute, 1986)(8). When ancient rice evolved into dry and paddy rice, paddy rice was in itially cu ltivated by direct sowing in the south and north. In the south, the ancient land was fertilized by burning straw and weeds and watering the land (You Xiuling, 1995)(9). We don’t know clearly why direct sowing was used rather than transplanting. Actually, the method of domestication is key. Co mmon wild rice evolved fro m perennial into annual, and then cultivated. Later, it differentiated to indica and japonica, with direct consequences on the method of domestication. This remains unclear. 2. Does ancient rice excavation s upport direct sowing theory? In 1997-8, Chengtoushan site ancient rice in Li County, Hunan, was excavated by Hunan Institute of Archaeology. Partial observations extending timewise confirm its direct sowing (10). Chengtoushan paddy occupied ca. 2 qiutian (90 sq. m) and included an original irrigating system of ditches and ponds. In 1992-1995, Cao xieshan site paddy, Suzhou, was excavated by the Nanjing Museum under the direction of Prof. Tengyuang Hongzhi, Agriculture Dept., Japanese Guanqi Un iversity, with outside help fro m Suzhou Museum, Wuxian Cu ltural Administrative Co mmittee, Jiangsu Agricultural Scientific Institute, Zuozuo Mugaoming, Gongle Shantong, Douchu Bilu zhi and Liuze Yinan. The 6000 year-o ld Cao xieshan site has 44 ancient paddyfields, 2 ponds, 6 ditches and 10 wells. The paddyfield rows are fro m SW to NE, with rectangular, elliptical or irregular pits 0.9 -12.5 sq. m in area, but co mmonly 3-5 sq. 1 m(11), with total area ca. 150 sq. m. Without observing sections, floors, footprints or seedling holes (12), we cannot deduce direct seeding or transplanting. Cao xieshan and Chengtoushan planting may have been alike because the former is only 300-500 years younger and japonica was jointly planted. Jian xiang Gu said carbonized rice size and weight in Cao xieshan level 4 resembles modern rice, while that in levels 6-8 are s maller. Rice width in d ifferent levels is similar, but weight variance coefficient and standard deviation rises with ascending level (8 to 4), wh ile type variance resemb les weight over time; i.e., level 4 carbonized cult ivated rice, while level 6-8 rice is transitional fro m wild to cultivated. Gu believes wild rice evolved to cultivated rice 6300-5500 years ago. Chengtoushan rice was in the init ial trans ition stage of incomp lete domestication, and it is hard to say of broadcast sowing was used because there are no footprints or seed holes. Although its flat excavation surface had dry and wet parts, we cannot understand their meaning. It is hard to say if it was due to a dry over a wet level. We suggest Chengtoushan and Cao xieshan used broadcast sowing of annual wild or cult ivated rice grain, its germinating success and survival already achieving broadcast sowing needs. This happened 6500 -6000 years ago, 4500-5500 years later than Yuchanyan ancient rice. It is worth carefu l consideration to see if broadcast sowing was used in >5000 years domestication of wild rice. Although common wild rice reproduced perennially, it also reproduced sexually by flowering o r annually by seeding. After initial do mestication, perennial co mmon wild rice may have mutated or hybridized between perennial wild and cultivated rice. There are minor d ifferences between bi-peaked phytoliths of Yuchanyan cultivated rice, Jiangyong common wild rice and Dao County japonica (13), as well as modern cultivated rice Xiangzhong indica type II and Chaling common wild rice (14). Both Yuchanyan ancient cultivated rice and Dao County white husk rice were domesticated fro m Jiangyong common wild perennial rice, wh ile Xiangzhong indica type II was domesticated fro m Chaling co mmon wild perennial rice, not fro m annual co mmon wild rice, because Jiangyong and Chaling do not have annual common wild rice. Thus, 10,000 year-old Yuchanyan rice was not cultivated fro m seed, but perennially. Chengtoushan and Cao xieshan broadcast sowing displays practical agriculture, but cannot prove this technique occurred at Yuchanyan. 3. Weak germination does not support direct seeding theory It was difficult or impossible for fresh mature harvested perennial wild rice seed to germinate normally under deep dormancy. As it always dropped when mature, it was impossible to broadcast sow in the first domesticated stage. Deep dormancy and weak germination with litt le success was due to (1) husk blocking germination and (2) poorly or undeveloped seed. Unhusked perennial wild rice germination is very weak or non -existent at 9ºC. Under ideal conditions (40ºC day/30ºC night), germination is also weak, a v iability of 1.3-18.3 and success of 0.7-29.3% - too lo w fo r cultivation.(15) Easy grain casting under irrigation makes poorly or undeveloped germinal buds, with no germination. (16) So, it is impossible to domesticate co mmon wild rice by perennial seed broadcast with evolution to cultivated rice. What about annual wild rice? We also think it is impossible. Previous research shows annual wild rice evolved more than perennial, with more germinat ion success and viability. Its reproduction relied on powerfu l seed, not stalks, suggesting broadcast sowing existed. 2 But, China has no natural annual wild rice because it dispersed as weedy rice within cult ivated rice. Another reason was the impossibility of ancient farmers collecting sufficient weedy rice seed to domesticate by broadcast sowing. Academics believe weedy rice did not evolve direct ly fro m perennial wild rice, but by crossbreeding perennial wild and early cultivated rice (You Xiuling, 1990)(17). Other theories are: (1) wild or reverted type via cross or genetic recomb ination in cult ivated rice; (2) pro ximate ancestral annual of cu ltivated rice via seed reproduction, crossbreeding and accompanying species, and (3) offspring-generation remains crossbred by wild rice and cultivated rice (Yu Cong & Wu Wanchun, 1996)(18); i.e., annual wild rice fro m the crossbred of perennial wild and domesticated original or modern cult ivated rice, but not through natural evolution (first orig inal o r modern cultivated rice, then annual wild rice), its traits fro m original or modern cultivated rice genes. Another reason is that cultivated rice d id not come fro m seed broadcasting. Weedy rice seed dormancy period is strong and irregular, experiments showing Hainan weedy rice period is between indica and wild rice. Under the same situation, indica-like Birui 1d and Fen ziman 5d have lo wer germination (only 22.5%), slowly germinating for 3 months and then decomposing. At 25ºC they germinate after 3 months and will not decompose in 2 cm water, but dormancy lengthens like wild rice (Xu Cong & Wu Wanchun, 1996), making it impossible for ancient people to use this type of seed broadcast. In sum, whether perennial or annual, wild rice germination was weak and not used for broadcasting the earliest domesticated wild rice. 4. Wild Rice Transplanting is the Earliest Domestication Method As stem preservation was its main reproduction, transplanting was the first domestication mode to convert perennial co mmon wild rice to annual cult ivated rice. Ancient farmers had to transplant peren nial common wild rice by seed stem to provide seed production and food. The main reason for transplanting this way was flooding. Field investigation shows transplanting was the earliest form of do mestication; e.g., the Ximengwa minority in Yunnan Province “transplant wild potato by excavating the tuber, cutting it and retaining its bud, and replanting it there or a new p lace, with the remainder eaten. It became domesticated over lengthy transplanting in their gardens. Although its root and leaves resemble wild potato, root hairs were less.” (19) “Ximengwa dry rice evolved directly fro m wild rice, not paddy, although some dry rice variet ies can be planted in paddy, while the latter cannot be planted as dry rice. After (1949) liberat ion of Masan Stockade Vil lage, new paddy fields were in low-lying wet p laces and plowed by humans or water buffalo. It was first hoed then ploughed, while stony areas were plowed twice, then dry seeded.” (20) Perennial co mmon wild rice is a marsh plant, not dry land, while dry rice rose after lengthy paddy rice domestication and then dry land transplanting. Thus, dry rice survives in paddies, while paddy rice cannot survive without much water. That dry rice possibly evolved fro m wild rice is wo rth discussion, but the Wa minority transplant dry rice rather than broadcast seedling, wh ich demonstrates original rice domestication. Transplanting traits are: (1) paddy seedlings have few roothairs like potato; (2) early stem gro wth is slow, late is fast, and (3) leaf emergence rate mirrors leaf size, with lengthy growth and high yield (21); i.e., perennial co mmon wild rice t raits change as it was domesticated to annual rice. Sown rice roots are shallow, often horizontal and scattered with much root hair, wh ile transplanted rice roots first grow horizontally, then vertically, an important reason why paddy rice initially falls easily. This phenomenon results from stem propagation; more vert ical and less lateral roots in transplanted rice are used in reconstructing wild rice. The weakness of stem propagation is increased seed production. Slowly, perennial rice developed into annual rice. As root damage while transplanting directly affects survival, length of greening, etc., detecting the original root system of wild rice is crucial. Often, washing of the transplant causes much damage, longer greening period and 3 less grain than direct seeding, an average production loss of 2.1-2.7 %. (22) While we are discussing modern cultivated transplants, it also applies to original domesticated perennial wild rice. Ancient perennial common wild rice was domesticated by transplanting seedlings, ensuring higher survival, shorter greening period and more grain, resulting in a good harvest in the following year. 5. Transplanting Incentive and its Ethnological Evidence Why did our ancestors transplant perennial co mmon wild rice? Main ly due to disastrous floods. The Rice Derivation chapter in the ancient classic Brief Description of the Origin of Species mentions five floods in the sky and five major grains in the earth. East, west and south, grain was cultivated fro m seedlings. First, grain was used as food, then seed, and finally in other products, which s urvived to the present.” (23) The five sky floods signify disastrous flood following heavy rain as the reason to transplant perennial co mmon wild rice. Co mmon wild rice usually gro ws in shallow marshes 30-50 cm deep because depth >1 m is too great, while >2 m drowns it. As heavy flood washes away seedlings, ancient farmers transplanted common wild rice to higher ground, building irrigation wo rks (ponds, ditches & wells) for survival. As the above only mentions east, west and south, we can infer the northern absence of rice. The above classic’s Buckwheat Derivation chapter said “buckwheat preceded the five majo r grains, broadcasting its seed which grew lu xu riantly. It was food before other grain.” (24) Its Seed Origin chapter said “Gouade, the first artisan and sky god, opened a sky door and threw seed to earth, where it grew to trees atop mountains, buckwheat on flat land and hemp in the foothills. (25)” Unlike buckwheat, hemp and trees which rely on seed propagation, paddy rice was cultivated by transplanting. Finally cultivate has an ancient Chinese meaning, its meaning in Yi dialect is “pile or roll up” (move, hole, domesticate)(26); i.e., transplanting common wild rice with earth adhering to root (pile is earth up, move or transplant and hole is the initial shape of the paddy field. Do mestication is concious cultivation. In ancient Yi, “p lant”, “transplanted rice seedlings” and “paddy field” have the same pronunciation (t 33 pron. “de”), wh ile “cutting transplant” is tshou (pron. “chou”), “broadcast” is SI55 & Si33 (pron. “xing” or “si”), “dig” is du 21 (pron. “du”), “bury” is du 55 (pron. “du” like “plant”), “rice seedling transplant” and paddy field” is t 33 , remote fro m “broadcast” SI55 or Si33 , meaning digging or burying, not broadcasting. “Pile” is bury, “roll” is digging; transplanting rice seedlings means burying them, and plant is bury and dig (dig first and then bury). The same source for ancient Yu or Zhuang language says “plant” is ndaem (pron. “dai mu”). “Plant and grow” is also ndaem, “plant and cultivate” is ung or gang (ung means plant, gang means catch up) ; “transplant rice seedlings” is ndaemnaz (pron. “dai mu na”); “transplant cutting” is baek (pron. “bai”); “interrupt a conversation” is cabbak (pron. “cha ba”); “transplant” is senjndaem (pron. “shen dai mu”); “move” is daen or ndaem; sen j; coek; nod; doeng; soenh; gyod, etc., and “field” is naz (pron. “na”). Thus, the earliest paddy rice cultivation was by “seedling transplant”, not “broadcast”. Because “scatter” is vang (pron. “wang”), “broadcast” is vangdoek (pron. “wang duo”), comp letely different fro m daem of “plant”, “plant and cultivate”, “transplant seedlings” and “transplant”.(27) Daem in Zhuang and t33 in Yi mean “dig” or “bury”, but “dig” in Zhuang is Vat (pron. “wa”) and “bury” is man (pron. “man”), different fro m Yi. As daem in Zhuang came fro m Yi, paddy rice cultivation is prior to Yi, then spread to Yu. Some scholars believe early rice fa rmers were Yiyang speakers of the Tongtai minority of ancient Yu. (28)But according to words like “plant”, “planting seedlings”, “scatter”, “dig” or “bury” in Yiyang (Yilao, buyang), there are too many differences with Yi; e.g., “p lant seedlings” was obviously transmitted with “plant”, “dig”, “bury”, and “transplant seedlings”. (29) English Yil ao Buyang AncientYi 4 plant tsha 42 Pak55 tshou33 seedlings thang 35 ?dam24 t 33 transplant tse35 fi:u 24 tsA21(tsi55) broadcast sa 42 ta:n 55 SI55(si33) dig hai42(tau 33) ?ba:k 11 du 21 bury phang 42 puk 55 du 55 plant tan 35 tam33 t 33 cultivate tan 35 tam33 t 33 field zung 13 na 33(?ong32) t 33 Ancient Yi d ifferentiation is lowest, Yilao highest and Buyi mid way. “Plant”, “seedlings” and “cultivate” in the latter two were obviously borrowed fro m Yi. We deduce early rice farmers were 10,000 y ear-old Yi people, not ancient people fro m Yiyang or Yu 6,000 years ago. References: (1) Zhang, Deci: Morphological Research on Asian Rice and its Wild Species as well as Identification in the Australian New Co mmun ity. Agricultural Science and Technology Translation Collection, 1984(2). Transl. by Xu Yunbi, Zhejiang Agricu lture Un iversity. Orig inal text : N.Q.Ng & T.T.Chang. Biological J. of the Linnean Society (1981)16. (2)(4) Oka, H.I. 1998. Origin of Cultivated Rice, Chapter 7. (3) Sano, Y.; H.Morishima & H.I.Oka. Intermediate Perennial - Annual Population of O. perennis found in Thailand and its Evolutionary Significance, Botany Magazine, Tokyo 93:291-305, 1980. (5) Second (Sai, Kongde), G. 1982. Orig in of the Genetic Diversity of Cult ivated Rice. Study of the Poly morphism Scored at 40 Isozy me Loci. Japanese Journal of Genetics, 57:25-27. (6) Xiangkun Wang, Hongwei Cai, Chuanqing Sun, Zhenshan Wang & Hanhua Pang: Origin of Ch inese Co mmon Wild Rice and Discussion on some Differentiation between Indica and Japonica. Orig inally in Chinese Rice Science 1994, 8(4):205-210, now Origin and Evolution of Chinese Cultivated Rice (ed. by Xiangkun Wang & Chuanqing Sun), Chinese Agriculture University Publishers, 1996:101-106. (7)(13) Wen xu Zhang & Jiarong Yuan: Init ial Research on Ancient Cultivated Rice in Yuchanyan, Dao County, Hunan Province. Crops Academic Journal 1998, 4:416-420. (8)(21)(22)(27) Ed. by Chinese Agricultural Scientific Institution: Chinese Rice Culture, Agriculture Publishers, 1986:685; 692-697;500; 692-697. (9) Xiu ling You : Chinese Rice Culture History, Chinese Agriculture Publishers 1995:149. (10) Hunan Archeological Research Institute: Chengtoushan Site, Li County, 1997-1998 Su mmary of Annual Excavation. Cultural Products 1999, 6:4-17. (11) Jiang xiang Gu, Houben Zou, Minchang Li, Linghua Tang, Jinlong Ding & Qinde Yao: In itial Finding of Rice Crop Agricu lture in Majiabing Cultural Period, Cao xieshan Site. Eastern Culture 1998, 3:15-24. (12) Jiang xiang Gu; letter to the author, August 10, 1999. (14) Wenxu Zhang. Observed Traits of Chaling Co mmon Wild rice (O. ru fipogon), Hunan. Papers of 3rd International Academic Conference on Agricultural Archaeology. Rice a nd Yen Ti Culture. 1999, Zhu zhou. (15) Jiaq iu Chen, Zhao xin Hou, Chugong Tan & Xiucheng Ning: Research on Improving Germination of Wild Rice (ed. by Miaole Wu). Papers of Wild Rice Resource Research, Ch inese Science and Technology Publishers 1990:170-173. (16) Shiy ing Zhao, Liq in Huang & Xiaofeng Mao: Research on Improving Seed Germination of Wild Rice (ed. Miaole Wu). Papers of Wild Rice Resource Research, Chinese Science and Technology Publishers, 1990:167-169. (17) Xiuling You: Discussion of Wild Rice Recorded in Ancient Ch inese Books (ed. M iaole Wu). Papers of Wild Rice Resource Research, Ch inese Science and Technology Publishers, 1990:174-179. (18) Cong Xu & Wangchun Wu: Ecological Investigation and Identification of Weedy Rice on Hainan Island. China Paddy Rice Science, 1996, 10(4):247-249. (19)(20) Genpan Li & Xun Lu: Ximengwa Agriculture involving Kn ives and Hoes. Agricultural Archaeology, 1985, 1:358-370. (23) Bijie Area M inority Affairs Co mmittee, Gu izhou Province, Translated by Yi Language Transla tion Group: Brief Description of the Origin of Species, Vol. 2, Sichuan Ethnic Publishers, 1991:216-17 (24) Brief Description of the Origin of Species, Vo l. 3, Sichuan Ethnic Publishers, 1993:255-259. (25) Brief Description of the Origin of Species, Vo l. 1, Sichuan Ethnic Publishers, 1990:24-27. 5 (26) Ed. by Literature and History Research Office, Lunanyi Ethnic Autonomous County, Yunnan Province: Yi-Chinese Concise Dictionary, Yunnan Ethnic Publishers, 1984:292; 8. (27) Ed. by Minority Language and Character Work Co mmittee Research Office, Zhuang Ethnic Autonomous Region, Guangxi Province: Chinese-Zhuang Dictionary, original edition, Guang xi Ethnic Publishers, 1983. (28) Jin fang Li: New Linguistic Ev idence of the Origin of Chinese Rice Culture. Ethnic Languages, 1999, 3:35-41. (29) Jin fang Li, Guoyan Zhou & Xiaoban Longyi: Yiyang Language Dictionary, Guizhou Ethnic Publishers, 1998. 6