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Perennial rice are varieties of long-lived rice that are capable of regrowing season after season without reseeding; they are being developed by plant geneticists at several institutions. Although these varieties are genetically distinct and will be adapted for different climates and cropping systems, their lifespan is so different from other kinds of rice that they are collectively called perennial rice. Perennial rice—like many other perennial plants—can spread by horizontal stems below or just above the surface of the soil but they also reproduce sexually by producing flowers, pollen and seeds. As with any other grain crop, it is the seeds that are harvested and eaten by humans. Perennial rice is one of several perennial grains that have been proposed, researched or are being developed,〔Wagoner, P. (1990)Perennial grain development: past efforts and potential for the future. Critical reviews in plant sciences. 9(5):381-408〕 including perennial wheat, sunflower, and sorghum. Agronomists have argued that increasing the amount of agricultural landscapes covered at any given time with perennial crops is an excellent way to stabilize and improve the soil, and provide wildlife habitat.〔Reviewed in (Cox, T.S., et al. (2002) Breeding Perennial Grain Crops. Critical Reviews in Plant Science. 21(2):59-91. ).〕 Perennial rice breeding was initiated at the International Rice Research Institute, Philippines〔International Rice Research Institute, 1988. pp. 66 in IRRI toward 2000 and beyond. IRRI, Manila, Philippines.〕 and are currently being developed at the Yunnan Academy of Agricultural Sciences, People's Republic of China, and other institutions, but are not yet available for distribution. ==Perennial and annual rice== Domesticated Asian〔African rice, ''Oryza glaberrima'' is another domesticated rice. Its ancestor is strictly annual. The vast majority of the rice grown in the world—even in Africa—is Asian rice so, henceforth, "rice" in this article will refer only to Asian rice.〕 rice, ''Oryza sativa'' is a short-lived plant. Most cultivars die after producing seeds, though some can regrow ((ratoon )) and produce a second crop under favorable conditions.〔Chauhan, J.S, B. S. Vergara, and F.S.S. Lopez. 1985. Rice ratooning. IRRI Res. Paper Ser. 102. IRRI, Manila, Philippines〕 In regions with mild climates, two or three crops of rice may be grown each year. Except for ratoon crops, this means that the dead stalks must be removed, the soil cultivated, and new seed sown every few months. In contrast, the wild ancestor of Asian rice, ''Oryza rufipogon'', often lives for many years, setting seed each year and spreading vegetatively.〔Kush, G.S. 1997. Origin, dispersal, cultivation and variation of rice. Plant Mol. Biol. 35:25-34〕 In addition to these perennial types, some ''O. rufipogon'' populations are annuals or intermediate in lifespan〔Morishiima, H., Y. Sano, and H.I. Oka. 1984. Differentiation of perennial and annual types due to habitat conditions in the wild rice ''O. perennis''. Plant Syst. Evol. 114:119-135〕 Other wild species in the genus ''Oryza'' are also perennial. While perennial ''Oryza rufipogon'' spreads vegetatively by above-ground stems (stolons), ''O. longistaminata'', ''O. officinalis'', ''australiensis'', ''O. rhizomatis'' spread by underground stems (rhizomes). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Perennial rice」の詳細全文を読む スポンサード リンク
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