7(1&2): AgBioForum, 31-35. 2004 AgBioForum.
Rice Biotechnology: A Need for Developing Countries
Swapan K. Datta
International Rice Research Institute, Manila, Philippines Rice, the most important food crop of the developing world, feeds more than two billion people as a staple food. Its improvement since the Green Revolution has been enormous, and biotechnology in the genomics era offers unique scope for further improvement to attain environmentally friendly sustainable agriculture. Nutritious rice with high iron and beta carotene in polished seeds has been developed with genetic engineering technology. It is now possible to use Bt or Xa21 rice in farmers' fields with reduced pesticide use. Farmers can produce more rice with built-in plant protection at a reduced cost. Policymakers should look into the potential use of biotechnology, provide access to intellectual property rights (IPR), and make improved rice seeds available free of IPR for resource-poor farmers. Key words: biotechnology, genetic engineering, nutritious rice, plant protection, rice.
Introduction: The Importance of Rice
Rice feeds more than two billion people worldwide and is the number one staple food in Asia, where it provides 4070% of the total food calories consumed. Rice is also used for animal feed and provides the major source of income for rural people; high-quality rice brings in additional income. Due to the Green Revolution, a quantum leap in rice yield took place over the past three decades, although increased food production did not eliminate poverty and hunger. The yield increase did help to avert famine and prevent a greater disruption of the food supply in Asia--unlike in some countries of Africa, where a lack of infrastructure and political will resulted in the failure to take advantage of Green Revolution techniques. Today's global population of six billion is expected to reach eight billion by 2020. We must therefore produce 2540% more rice with less land and water and with a reduced use of agrochemicals. Rice yield has been stagnant for the last three decades, despite the improved varieties and technologies in place. Therefore, biotechnology--particularly genetic engineering--may provide ample scope for enhancing rice yield and plant protection, enable rice to grow in drought and saline conditions, and lead to more nutritious rice for reducing malnutrition.
candidate genes. Cultivated rice has evolved for centuries through domestication, which preferentially narrowed the diversity of genetic resources. It is also important to explore wild rice species and characterize their genes for further use rather than storing them in a gene bank. The recent rice genome sequences developed by Monsanto, Syngenta, and the Beijing Genomics Institute (BGI), along with ongoing research in the International Rice Genome Sequencing Project (IRGSP), have accelerated gene discovery and rice improvement. However, advances in plant biotechnology must be deployed for the benefit of developing countries using a strong public-sector agricultural research effort (Conway & Toenniessen, 1999; Beachy, 2003). Recognizing the tremendous value of genomics research for rice improvement, the International Rice Research Institute advocates broad collaboration in rice research involving the private and public sectors, with emphasis on the need to provide the best science to serve the poor (Cantrell & Reeves, 2002).
The Green Revolution and Genetic Engineering
The International Rice Research Institute released IR8, the first high-yielding modern rice cultivar for irrigated tropical lowlands. Since then, efforts to improve the rice plant for higher yield and desirable characteristics continue, but innovations are needed to break the yield barrier (Figure 1; Datta & Khush, 2002). Genetic engineering provides an efficient and precise breeding tool in which genes of interest (such as Xa21 for bacterial blight resistance, cry for stem borer resistance,
Genomics and Biotechnology
Genomics refers to DNA sequencing, the routine use of DNA microarray, and proteomics. Genomics-based strategies for gene discovery, coupled with the validation of transgenes by genetic transformation, have accelerated the identification of a functional profile of
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18 16 14 Potential yield (t/ha) 12 10 8 6 4 2 0 1900 1930 1950 1965 1990 1995 2000 2005 2010 2015
Figure 1. Progress in the yield potential of rice.
ORF2 for virus resistance, DREB/TPSP for drought and salinity tolerance, chi11, RC7, and NPR1 for fungal resistance, psy and crtI for provitamin-A biosynthesis, glgc for higher grain filling, and PEPC for C4 photosynthesis) have been incorporated in rice and have shown excellent performance in most cases (Table 1). Pyramiding of Xa genes by marker-assisted breeding has also been shown to work well in rice; this technique is now extensively used in India, Philippines, China, Indonesia, and Thailand under the Asian Rice Biotechnology Network (ARBN) program. I have summarized a few selected examples of the development of transgenic rice and its potential use in developing countries (Table 1) and emphasized two potential areas--plant protection and nutrition improvement--for immediate use. Plant Protection Farmers in developing countries do not capture a significant portion (2070%) of the potential yield in favorable ecosystems primarily because of biotic and abiotic stresses. Losses caused by weeds, yellow stem borer, leaffolder, sheath blight, blast, bacterial blight, and various abiotic factors have remained largely undiminished despite considerable investment in cultivar improvement. Limitations in conventional breeding arise because of the lack of resistance genes in cultivated rice germplasm (Oryza sativa L.) and inadequate understanding of phenotypic variability. Hence, transgenic research offers unique opportunities to overcome these problems and to produce improved cultivars with
Figure 2. Transgenic Bt rice (MH63) showing healthy growth (T). Control MH63 (C) shows natural infestation of leaffolder.
reduced yield gaps. Bt rice has now been field evaluated for several years in China (Figures 2, 3, & 4; Tu, Zhang, et al., 2000; Ye, Tu, Hu, Datta, & Datta, 2001) and has shown resistance against several insect pests--the striped stem borer (Chilo suppressalis), yellow stem borer (Scirpophaga incertulas), pink stem borer (Sesamia inferens), leaffolder (Cnaphalocrocis medinalis), and green semilooper (Naranga anescens)--and excellent agronomic performance (28% higher yield than that of seed-derived control plants). The second generation of Bt rice with multiple cry genes with different receptor-binding protein is now in progress; this may delay
Datta -- Rice Biotechnology: A Need for Developing Countries
AgBioForum, 7(1&2), 2004 | 33 Table 1. Transgenic rice developed with genes of agronomic importance. Gene Xa21 Trait Resistance to bacterial leaf blight Cultivar IR72, IR64, IR68899B, MH63, BPT5204, Pusa Basmati-1, IR50, CO39 Remarks IR72 field-evaluated in China, India, and Phillipines IR72 and MH63 field-evaluated Hybrid Bt rice now grown in China
Bt (cry1Ab, cry1Ac, cry1Ab+cry1Ac), cryIIA Chitinase (chi11, RC7), tlp D-34 Xa21 + Bt + PR genes
Resistance to insect pests IR72, IR64, MH63, IRRINPT, Vaidehi Sheath blight resistance Resistance to bacterial blight, stem borer, and sheath blight Resistance to herbicides C4 rice Resistance to rice yellow mottle virus Abiotic stress tolerance
IR72, IR64, CBII, Swarna Transgenics showed enhanced protection against fungus IR72 Transgenics showed broad-spectrum multiple resistance
PPT PEPC ORF2a for serine protease and RNA-dependent RNA polymerase TPSPb, DREB psy, crtI, lcy
IR72, Koshihikari, NHCD, Works very well under field conditions etc. IR68899B ITA 212 (FARO 35), Bouak 189, BG90-2 PB-1, BR29, IR68899B Enhanced photosynthetic efficiency Transgenics showed resistance against lowand high-dose virion and RYMV RNA inocula Transgenic rice showed tolerance for drought, salt, and low-temperature stress
Provitamin-A biosynthesis T-309, IR64, BR29, Nang Transgenics showed yellow-colored Hong Cho Dao, Mot Bui, endosperm by beta-carotene accumulation IR68899B, Immeyobaw Iron storage IR68144, BR29 Transgenic lines showed increased iron and zinc accumulation in seeds
ferritin
Note. Data modified from and Datta Khush, 2001. a Data from Pinto et al., 1991. b Data from Garg et al., 2003.
Figure 3. Transgenic MH63 (T) showing resistance to YSB and control MH63 (C) showing YSB symptoms.
Figure 4. Transgenic (T) hybrid Bt rice Shan you 63 showing resistance and control (C) showing susceptibility to pest attacks.
Datta -- Rice Biotechnology: A Need for Developing Countries
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Figure 5. Transgenic homozygous IR72 (T) showing resistance reaction against bacterial leaf blight with much less lesion length than nontransformed control (C) under field conditions at Wuhan, China.
Figure 7. IR64 Golden rice seeds (right) showing beta-carotene expression, control (left) showing no expression after polishing.
Figure 8. Transgenic rice seeds with high iron (left) and control (right) after polishing.
Nutrition Improvement Eight hundred million people worldwide live below absolute poverty levels, and the majority of these women and children are malnourished as they do not have access to the essential food basket. It might take another 50 years or more to reduce their poverty or improve their economic growth, which depends on political will, population control, and social reforms. Availability of nutritious rice may force governments to prioritize decisions to distribute more nutritious rice free or at a minimal cost, which will benefit poor people (Datta, 2001). Rice engineered with genes for -carotene biosynthesis (Ye et al., 2000) resulted from an intellectual property donation from several multinational companies, including Syngenta, Monsanto, Bayer, and Mogen. These genes are now used in developing tropical elite indica rice using the nonantibiotic selectable marker pmi (phosphomannose isomerase) gene (Figure 7; Datta et al., 2003), which might be able to reduce vitamin A deficiency. Moreover, iron has been enhanced in indica rice by introducing the ferritin gene driven by the
Datta -- Rice Biotechnology: A Need for Developing Countries
Figure 6. Transgenic IR72 with Xa21 showing bacterial blight resistance with excellent agronomic performance under field conditions in the Philippines.
pest evolution even longer. Xa21 rice, initially reported by P. Roland's group from the University of CaliforniaDavis (Song et al., 1995) is now further developed in several indica backgrounds and is being field evaluated in the Philippines, China (Tu, Datta, Khush, Zhang, & Datta, 2000), and India (Figures 5 & 6). Yellow mottle virus-resistant rice, herbicide-resistant rice, sheath blight-resistant rice, and abiotic stress tolerant rice have been reported by several groups (Table 1; Datta, Datta, Soltanifar, Donn, & Potrykus, 1992; Datta, Baisakh, Thet, Tu, & Datta, 2002; Pinto, Kok, & Baulcombe, 1999; Lin et al., 1995; Garg et al., 2002), including our unpublished work with the DREB gene (in collaboration with Dr. Shinozaki's group).
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endosperm-specific promoter (Figure 8; Vasconcelos et al., 2003). It is also possible to improve the essential amino acids (such as lysine) in rice; work is in progress in collaboration with DuPont. As we have shown by pyramiding transgenes (Xa21, Bt, PR-protein genes) functioning in a homozygous single elite cultivar (Datta et al., 2002), it might be possible to incorporate the genes for -carotene and enhancement of iron and protein in a single rice variety to achieve the "dream rice" for those who need it most.
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