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Rice regrowing from rhizomes

Two types of plants could be called perennial rice: (1) wild, perennial species in the genus Oryza and (2) grain-yielding varieties of domestic rice that have been been bred for longer lifespan. In this article, the first will be referred to by their latin names; the term perennial rice will only be used for the second group.


Perennial rice varieties were initiated at the International Rice Research Institute, Philippines [1] and are currently being developed at the Yunnan Academy of Agricultural Sciences, People's Republic of China, but are not yet available for distribution.


Perennial rice is one of several perennial grains that have been proposed, researched or are being developed [2] , 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. [3]


Perennial and annual rice

Seed heads of annual Asian rice

Domesticated Asian [4]Rice, Oryza sativa is a short-lived plant. Most cultivars die after it producing seeds, though some can regrow (ratoon) and produce a second crop under favorable conditions [5]. 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.[6]. In addition to these perennial types, someOryza rufipogon populations are annuals or intermediate in lifespan [7]


Other wild species in the genus Oryza are also perennial. While perennial Oryza rufipogon spreads vegetatively by above-ground stems (stolons), Oryza longistaminata, O. officinalis, O. australiensis, O. rhizomatious spread by underground stems (rhizomes).

Potential benefits

Rice is an important world crop

Rice is most economically important crop in the world according to the Food and Agriculture Organization of the United Nationsdatabase [8]. Rice is the number one cereal in the human diet, supplying humanity with 23% or its calories [9] . Slightly more maize is produced globally (791 vs. 659 million megatonnes in 2007), but while 40-80% (61% average) of maize is fed to animals less than one percent of rice is used as animal feed. [10]

Perennial plants can reduce soil erosion

Farm fields, especially those in the humid tropics [11], that have been cleared of vegetation or recently plowed are highly vulnerable to soil and nutrient loss through wind or water erosion, soil compaction, and decline in soil organic matter and microbes. Eroded fields become less productive and the soil particles and dissolved nutrients cause environmental problems downstream, including hypoxia in oceans and rivers and the silting of reservoirs and waterways.[12] "By all accounts erosion is the most serious natural resource and environmental consequence of rainfed upland rice production." [13]."


Perennial plants regrow quickly after being harvested, re-establishing a protective cover. The fields do not need to be plowed after the initial planting.[14]"A dense stocking of perennial plants-whether trees, shrubs, or herbs-in an agroecosystem increases the likelihood that the soil will be covered continuously, moderating oscillations in temperature and humidity that can damage the soil."[11] Researchers at The International Rice Research Institute (IRRI) believed that perennial rice would "improve the sustainability of food production in the hilly uplands and downstream." [15]

Other potential benefits of perennial crops

  • Drought resistance: Annual rice has a shallow root system and is very drought susceptible.[16] A long-lived plant has time to develop a deep and extensive root system making it theoretically capable of accessing more moisture than an annual plant[14]. Tilled soil dries out more quickly than untilled [17]
  • Resist weed invasion: Weed pressure has increased in upland rice systems as the fallow period has shortened [18]. Ecologist Jack Ewel wrote: "Weeds are widely recognized as a major impediment to continuous cropping in the humid tropics, and fields are often abandoned more because uncontrollable weed populations are anticipated than because of declining fertility or pest buildups." [11] Grassland restoration with perennials results in fewer annual weeds [19] and perennial grasses, sown at appropriate densities, can out-compete even perennial weeds once they are established. [20]
  • Plant nutrition: While shallow rooted species, such as rice [16] obtain most of their nutrients from the topsoil, deep rooted perennials can obtain significant proportion of their phosphorus from the subsoil[11]. "Deep roots are especially important in nutrient-poor substrates because they increase the volume of soil exploited by the vegetation"[11].

Target environments for perennial rice

Upland rice

Upland rice is grown on more than 7.5 million acres in the highlands of southern China and across southeast Asia. Because it is grown on steeply sloping soil without terracing, severe erosion results, and a given patch of land can produce rice for only a year or two before it is allowed to return to natural vegetation—only to be cleared and re-sown to rice a few years later. This is a potent recipe for soil degradation. Were rice a perennial rather than an annual species, its continuously living roots and thick cover of vegetation would prevent such erosion, just as a planting of grass can prevent a roadside slope from washing away. Perennial rice could, conceivably, produce critically needed food year after year on the same plot of land without degrading the soil.

Rainfed paddy rice

[38 million ha (26%) of total land in rice and for 88 millions t (17%) of total production.][21]

While upland rice production systems were the initial target for the perennialization of rice, the perennial habit may prove to have benefits in paddy systems where erosion is less of a concern. Faced with drought one year and flooding the next, "...the rainfed rice farmer can usefully be thought of first as a manager of risk and uncertainty [22]." Given the erratic moisture, many farmers do not used purchased fertilizers. With deforestation, manure may be used as cooking fuel making fertility a key problem. Where fertilizers are purchased, flooding can result in fertilizer runoff contaminating water systems [23]."

Rice with deeper roots, as would be predicted with perennial rice, could exploit the moisture and nutrients in a greater soil volume than short-rooted types (discussed above). The perennial habit could reduce the uncertainty of planting and transplanting with erratic rainfall patterns. Rhizomes would simply lie dormant until temperature and moisture conditions were adequate for emergence.

Irrigated paddy rice

Irrigated rice is very productive and this production method must be fairly sustainable, as it has been practiced in China for millenia [24] however, high yielding rhizomatous rice varieties may still have some advantages, according to Dr. Dayun Tao [25]

  • Fixing hybrid vigor: The first generation hybrids between two particular lines or individuals may be exceptionally good, but may be almost impossible to re-create. If the exceptional individual was perennial and rhizomatous, millions of genetically identical plants (clones) could be made from pieces of the rhizomes.
  • Expediting the production of inbred lines: Even if the final propagule for the farmers' fields is hybrid seed, not hybrid clones, the parents of exceptional F1 hybrids could be immediately clonaly propagated if they were rhizomatous. These genetic replicas could be maintained indefinitely and crossed afresh each year to produce new F1 hybrid seed. Normally, re-creating parents using sexual reproduction requires many generations of inbreeding.
  • Ratoon cropping: In some environments, additional grain crops could be harvested each year if the plants ratooned quickly. Shoots growing from the mature plant can reach the reproductive stage more quickly than shoots growing from seed. Transplanting seedlings is faster than sowing seed, but still requires time and labor intensive field preparation and, of course, a large supply of labor for transplanting.

Other benefits can be imagined in this environment:

  • Reduce the need for transplanting, weeding, and other backbreaking labor. Because of migration to cities, many rural parts of Asia actually suffer from severe labor shortages.
  • More efficient use of applied fertilizer

History of perennial rice research

Interspecific hybridizationa and embryo culture, Thailand, early 1990s

Drs Dayun Tao and Prapa Sripichitt, working at the Department of Agronomy, Kasetsart University, Bangkok, made numerous crosses between rice and wild, rhizomatous species[25]. The difficulty of this work is illustrated by the case of the single successful hybrid they obtained between Oryza sativa and O. longistaminata. To get this one plant, 119 rice florets were pollinated, which produced 51 seeds. Of these seeds, 33 had culturable embryos, and only one of these embryos developed into a viable plant. Put another way, this hybridization was relatively easy: over 3000 pollinations had to be made between rice and O. rhizomatis to get a single viable plant. It was a fortunate cross in other respects: the hybrid was healthy and rhizomatous (it is still alive) and partially fertile allowing F2 seed to be obtained.

Perennial Upland Rice program, Philippines, 1990-2001

To address the problem of erosion in upland rice-growing regions, the International Rice Research Institute (IRRI) initiated a breeding program for perennial upland rice in the mid-1990s[26]. Within just a few years, the program achieved significant progress. The Perennial Upland Rice project team used populations derived from crossing the rice plant Oryza sativa with two different distantly related perennials in the hopes that at least one of these strategies would enable genes from the perennial to be moved to the cultivated rice gene pool.

    • O. rufipogon as donor of perenniality traits. Fertility of the progeny families was generally good, as might have been predicted, given that O. rufipogon is the ancestor of cultivated rice. Many families were perennial, and some of the highest yielding families were the most perennial, suggesting that breeding for both yield and perenniality is feasible. [15]
    • O. longistaminataas donor of perenniality traits. This African species is genetically diverse, strongly perennial and rhizomatous. Rhizomes may be able to survive and spread in drier conditions than stolons. The downside of this donor is that it is more distantly related to cultivated rice and the crosses and backcrosses are much more difficult to make. Descendents of the few successful crosses are mostly infertile, and few were perennial. Interestingly, many of the perennial plants lacked rhizomes. Rhizomes may not be essential for survival, but they may help plants survive stress and they certainly help them spread. [27] [28]

Mapping rhizome genes, China, 1999-2001

Hu Fengyi, now deputy director of the Food Crops Institute at YAAS, worked on the IRRI perennial-rice project and was senior author of the paper that first reported on mapping of genes for rhizome production in rice. [29]. Using the F2 population derived from the Oryza sativa/O. longistaminata cross, two dominant-complimentary genes, rhz2 and rhz3 controlling rhizomatousness were mapped. These were found to correspond with two QTLs associated with rhizomatousness in the genus Sorghum, suggesting that the evolution of the annual habit occurred independently, long after these species diverged. Efforts to map these genes in rice more finely are ongoing. Although other genes undoubtedly contribute to perenniality and rhizomatousness, these two are required in rice. Breeders use markers for these genes to assist in identifying potentially perennial individuals.

Breeding population development, China, 2007-present

The IRRI project was terminated in 2001 because of budget cuts, but the Yunnan Academy of Agricultural Sciences (YAAS) in Kunming has continued the research. In order to obtain rhizomes, they focused on populations derived from crosses with O. longistaminata. As Eric Sacks and colleagues found at IRRI, the plants in these populations mostly lack rhizomes and have a high level of sterility. Finding the extremely rare plants with both rhizomes and fertility has required screening large populations. Ongoing projects include[30]:

  • Mapping genes that cause partial to complete sterility in many interspecific hybrids. As many as 35 such genes have been mapped in Oryza, and sterility is a big problem in the perennial rice program.
  • Marker assisted selection: large numbers of plants are being screened for rhizome markers. In the field, plants are evaluated first for rhizome production, then for seed fertility, and finally for pollen viability through staining.
  • Back-crossing: Using these tricks, out of thousands of F2 plants, a few have been found that are self-fertile and have 60 to 70% seed set (he says 80% would be acceptable to farmers). These are self-pollinated those to increase seed and crossed them back to several annual varieties.
  • Recombinant inbred lines: more than 250 lines which have all combinations of genes at the rhizome marker loci and are true-breeding. These will be highly valuable for mapping.


References

  1. ^ International Rice Research Institute, 1988. pp. 66 in IRRI toward 2000 and beyond. IRRI, Manila, Philippines.
  2. ^ Wagoner, P. (1990)Perennial grain development: past efforts and potential for the future. Critical reviews in plant sciences. 9(5):381-408
  3. ^ Reviewed in Cox, T.S., et al. (2002) Breeding Perennial Grain Crops. Critical Reviews in Plant Science. 21(2):59-91..
  4. ^ 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.
  5. ^ Chauhan, J.S, B. S. Vergara, and F.S.S. Lopez. 1985. Rice ratooning. IRRI Res. Paper Ser. 102. IRRI, Manila, Philippines
  6. ^ Kush, G.S. 1997. Origin, dispersal, cultivation and variation of rice. Plant Mol. Biol. 35:25-34
  7. ^ Morishiima, H., Y. Sano, and H.I. Oka. 1984. Differentiation of perennial and annual types due to habitat conditions in the wild rice Oryza perennis. Plant Syst. Evol. 114:119-135
  8. ^ FAOSTAT
  9. ^ Khush G, Productivity improvements in rice. Nutrition Reviews 61:S114-S116 (2003).
  10. ^ Calculated from FAOSTAT's 2003 data for China, USA, India, Brazil and Mexico. Online database: http://faostat.fao.org/site/355/default.aspx#ancor
  11. ^ a b c d e Ewel, J.J. (1986) DESIGNING AGRICULTURAL ECOSYSTEMS FOR THE HUMIDTROPICS. Ann. Rev. Eeol. Syst. 17:245-71
  12. ^ Pimental, D., et al. (1987) World agriculture and soil erosion. Bioscience 37:277-283.
  13. ^ Crosson, P. (1995)Natural resource and environmental consequences of rice production. In Fragile Lives in Fragile Ecosystems Proceedings of the International Rice Research Conference 13-17 February 1995. International Rice Research Institute, Los Baños, Laguna,Philippines http://books.irri.org/9712200736_content.pdf
  14. ^ a b Glover, J.D. (2005) The necessity and possibility of perennial grain production systems. Renewable Agriculture and Food Systems. 20:1-4
  15. ^ a b Sacks, E.J., J.P. Roxas, and M. T. Cruz (2003) Developing Perennial Upland Rice I: Field Performance of Oryza sativa/O. rufipogon F1, F4 and BC1F4 Progeny. Crop Science. 43:120-128.
  16. ^ a b Bernier, J. (2008)Breeding upland rice for drought resistance. Journal of the Science of Food and Agriculture. 88(6):927-939.
  17. ^ Blevins, R.L., et al.(1971) Influence of No-tillage on Soil Moisture. Agronomy Journal. 63:593-596
  18. ^ Roder, W., Phengchanh, S. and Keoboulapha, B. (1997) “Weeds in slash-and-burn rice fields in Northern Laos”. Weed Research 37: 111-119.
  19. ^ Blumenthal, D. M., N. R. Jordan, and E. L. Svenson (2003) Weed control as a rationale for restoration: the example of tallgrass prairie. Conservation Ecology 7(1): 6. [online] URL: http://www.consecol.org/vol7/iss1/art6
  20. ^ Darwent, A. L., and C. R. Elliott (1979) Effect of Grass Species and Row Spacing on Dandelion Establishment and Growth. Canadian Jouranal of Plant Science 59:1031-1036
  21. ^ Crosson, P. (1995)Natural resource and environmental consequences of rice production. In Fragile Lives in Fragile Ecosystems Proceedings of the International Rice Research Conference 13-17 February 1995. International Rice Research Institute, Los Baños, Laguna,Philippines http://books.irri.org/9712200736_content.pdf
  22. ^ Anderson, J.R. (1995) Confronting uncertainty in rainfed rice farming: research challenges. In Fragile Lives in Fragile Ecosystems Proceedings of the International Rice Research Conference 13-17 February 1995. International Rice Research Institute, Los Baños, Laguna, Philippineshttp://books.irri.org/9712200736_content.pdf
  23. ^ Crosson, P. (1995)Natural resource and environmental consequences of rice production. In Fragile Lives in Fragile Ecosystems Proceedings of the International Rice Research Conference 13-17 February 1995. International Rice Research Institute, Los Baños, Laguna,Philippines http://books.irri.org/9712200736_content.pdf
  24. ^ King, F.H. (1911) Farmers of Forty Centuries, or Permanent Agriculture in China, Korea and Japan. Democrat Printing Co., Madison WI.available on Google Books
  25. ^ a b Tao Dayun1 and Prapa Sripichitt (2000) Preliminary Report on Transfer Traits of Vegetative Propagation from Wild Rice Species to Oryza sativa via Distant Hybridization and Embryo Rescue. Kasetsart J. (Nat. Sci.) 34 : 1 - 11. Available online
  26. ^ http://www.irri.org/publications/program/pdfs/97ProgramReport/Upland.pdf
  27. ^ Sacks, E.J., J.P. Roxas, and M. T. Cruz (2003) Developing Perennial Upland Rice II: Field Performance of S1 Families from an Oryza sativa/O. longistaminata Population. Crop Science. 43:129-134.
  28. ^ Sacks, E. J. et al, 2006. Breeding for perennial growth and fertility in an Oryza sativa/O. longistaminata population. Field Crop Res. 95:39-48.
  29. ^ F. Y. Hu* et al. (2003) Convergent evolution of perenniality in rice and sorghum. PNAS. 100 no. 7 4050-4054 Available from PNAS
  30. ^ Personal communication with Mr. Fengyi Hu, Yunnan Academy of Agricultural Sciences, Kunming, PRC

See also

  • Valentin, C., 'et al'.(2008)Runoff and sediment losses from 27 upland catchments in Southeast

Asia: Impact of rapid land use changes and conservation practices. Agriculture, Ecosystems and Environment 128:225–238 [http://digital.upbatam.ac.id/elibrary/Library/Agricultur_Ecosystems/Valentin_Runoff.pdf

  • de Rouw, A, Soulileuth, B., Phanthavong, K., Dupin, B., 2005. The adaptation of

upland rice cropping to ever-shorter fallow periods and its limit. In: Bouahom, B., Glendinning, A., Nilsson, S., Victor, M. (Eds.), Poverty reduction and shifting cultivation stabilisation in the uplands of Lao PDR: technologies, approaches and methods for improving upland Livelihoods – Proceedings of a workshop held in Luang Prabang, Lao PDR, January 27–30, 2004. National Agriculture and Forestry Research Institute. Vientiane, Lao PDR, pp. 139–148.PDF available

  • Schmit, V., 1996 Improving sustainability in the uplands through the development of a perennial upland rice, pp. 265-273 in Upland Rice Research in Partnership, Proceedings of the Upland Rice Consortium Workshop, edited by Piggin C., B. Courtois, V.Schmit. 4-13 January 1996; Padang, Indonesia.
  • Tao, D., F. Hu, Y. Yang, P. Xu. J. Li, E. Sacks, K. McNally, P. Scripichitt. 2000 Rhizomatous individual was obtained from inerspecific BC1F1 progenies between Oryza sativa and O. longistaminata, in The abstract of International Rice Genetic Symposium. 22-27 October 2000. International Rice Research Institute, Los Bnaos, Philippines.
  • Tao, D., F. Hu, E. Sacks, K. McNally et al., 2001 Several lines with Rhizomatous were obtained from interspecific BC2F1 progenies of RD23/O.longistaminata backcrossed to RD23, in Division Seminars of PBGB, International Rice Research Institute, Los Banos, Philippines.
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