Global hybrid rice: progress, issues and challenges
D.V. Tran and V.N. Nguyen
Crop and Grassland Service, Plant Production and Protection Division, FAO
Rice is the world's most important food crop: in 1995, more than 3 billion people depended on rice for food energy and protein. The international effort in rice varietal improvement during the 1950s and 1960s led to International Rice Research Institute's development of the semi-dwarf indica, nitrogen-responsive and lodging-resistant variety, IR8, in the late 1960s. This was followed by the green revolution in many rice-producing countries, which enabled global rice production to meet the demand of the world's increasing population and save millions of people in several developing countries from starving. The world's population (currently 5.9 billion) is still growing at a relatively fast rate and is projected to reach 9 billion by 2030. World rice production, therefore, must increase.
In Asia, which accounts for about 90 percent of the world's rice area, production and consumption, most of the land suitable for rice production has been exploited. Also, the water used in rice production is being competed for by the production of other crops as well as industry and urbanization. Land and water for rice production may be available in other continents such as Africa and Latin America, but the costs of conversion may be too high for rice production to be profitable. Meanwhile, the potential yields of the modern semi-dwarf rice varieties released after IR8 are more or less the same as, if not lower than, that of IR8, showing a yield plateau or ceiling. Increasing attention, therefore, has been given to the development of new-generation rice varieties. Hybrid rice varieties have a yield advantage of about 15 to 20 percent or more over the best conventionally bred varieties. China's success in commercial hybrid rice production clearly demonstrates that hybrid rice, at present, is the only practical tool for increasing world production. The cultivation of hybrid rice has enabled China to save more than 2 million ha of land for agricultural diversification. Also, the intensive labour utilization in commercial and F1 hybrid seed production has created rural employment opportunities and increased farmers' incomes. This technology, therefore, is very important for rice-consuming countries where arable land is becoming scarce, population is increasing at an alarming rate, labour is cheap and population densities are low.
The successful exploitation of hybrid rice in China has encouraged many rice-producing countries (e.g. Bangladesh, Brazil, Colombia, Egypt, France, India, Indonesia, Japan, the Republic of Korea, Myanmar, the Philippines, Thailand, the United States) to carry out hybrid rice studies. Hybrid rice technology, however, is rather complicated and time-consuming, requiring skill in breeding and F1 seed production. Successful development and use of hybrid rice needs commitment from scientists, support from governments and cooperation between research programmes and seed production sectors. Therefore, FAO, in collaboration with IRRI, Japanese scientists, the China National Hybrid Rice Research and Development Centre (CNHRRDC) and other selected national research centres, initiated its global hybrid rice programme in 1986 to expedite the widespread use of hybrid rice technologies outside China.
PROGRESS IN THE WORLD'S HYBRID RICE
Adoption of hybrid rice
Heterosis in crops other than rice, especially maize, has been exploited for commercial production. China began exploiting heterosis in rice in 1976 after Yuan Long Ping and his team developed the first set of stable and high-yielding three-line hybrid rice varieties. Since then, the area planted to hybrid rice in China has rapidly increased - in 1995 it was about 17 million ha. Hybrid varieties outyield the commercial check varieties by 15 to 30 percent in farmers' fields. For example the average yield of rice planted in Sichuan Province in 1989, where about 2.62 million ha were planted to hybrid rice, is about 8.25 tonnes/ha (Lin and Pingali, 1994). The rice team of the Rice Research Station at Beaumont in Texas (United States) reported that the highest yield of 13 800 kg/ha was obtained from a hybrid rice variety over a three-year testing period. The high productivity of hybrid rice has enabled China to reduce its cultivation area from about 34.4 million ha in 1978 to about 31.9 million ha in 1988 and, at the same time, increase its rice production from 136.9 million to 169.1 million tonnes during the same period (FAOSTAT data, 1997). This reduction of area planted to rice not only promoted the diversification in rice-based production systems, increased incomes and mitigates production risks, but also helped to minimize the country's emission of greenhouse gases such as methane and nitrous oxide. In addition, the exploitation of hybrid rice technology has increased rice farmers' incomes and created rural employment opportunities, since its yield is high and its seed production labour-intensive. The exploitation of hybrid rice technology, therefore, not only improves rice production but also reduces rural poverty at the same time as being environmentally friendly.
Outside China, the hybrid rice area was about 11 000 ha in 1992, increasing to 34 000 ha in 1993 and 102 000 in 1996 in Viet Nam, with an average yield of 6.5 tonnes/ha (15 to 30 percent higher than the best commercial varieties). Hybrid varieties are mostly planted in northern Viet Nam, where they have helped some provinces such as Thai Binh, Nam Dinh to produce a surplus for the first time. In India, farmers cultivated about 65 000 ha of hybrid rice in 1996. Limited commercial cultivation of hybrid rice was also reported in Bangladesh, the People's Democratic Republic of Korea and Myanmar.
Three-line hybrid technology
After the discovery of the wild rice plant with abortive pollen in 1970, Chinese scientists developed a number of cytoplasmic-genetic male sterile (CMS) lines (A lines), their corresponding maintainer lines (B lines) and fertility restorer lines (R lines) for the production of three-line hybrid rice varieties. The first set of three-line varieties were developed in 1974, including: Wei-you 2, Wei-you 3, Wei-you 6, Shan-you 2, Shan-you 3, Shan-you 6, Nan-you 2, Nan-you3, Nan-you 6, Si-you 2, Si-you 3 and Si-you 6. Commercial hybrid rice cultivation began in China in 1976 (Mao, 1993). After nearly three decades, considerable progress in hybrid rice research and development has been made, notably in the breeding of parental lines, development of hybrid varieties and improvement of F1 seed production.
Diversification of CMS sources. The first set of stable WA-type CMS lines was developed using cytoplasm from the wild rice plant found in Hainan. This set comprises Zhenshan 97A, V20A, Erjiu Ai 4A, Erjiu Nan 1A, V41A (Mao, 1993). In order to diversify the genetic sources of hybrid rice, the breeding programmes in China developed other CMS sources. At present, three-line hybrid rice varieties planted in China are developed from this diversified pool of CMS sources, including WA, DA, D and ID.
Outside China, IRRI used CMS sources from V20A, Kaliya 1, ARC and Gambiaka to develop CMS lines such as IR58025A, IR68275A, 68281A, IR68273A, IR68888A, IR68891A, IR68893A. Also, CMS lines have been developed with sources of cytoplasm in Oryza perennis (e.g. IR66707A) and O. rufipogon (e.g. OMS1) (Virmani, 1996). The genetic base of three-line hybrid rice varieties has therefore been greatly broadened and diversified.
Hybrid rice varieties. In addition to those developed in China, a number of three-line hybrid rice varieties have been developed and released for cultivation by IRRI. The public and private sectors in India released a dozen three-line varieties in 1996 while, in Viet Nam, UTL 1 and UTL 2 were released in the early 1990s and, more recently, Trang Nong 15 and Trang Nong 16 were released by a private seed company. In the Philippines, hybrid rice varieties developed by IRRI have been widely tested and one hybrid rice variety, Maggat, was released by the Cargill seed company. The hybrid rice varieties recently released in China, India and Viet Nam are more resistant to insects and diseases.
Grain quality. Grain quality is one major factor limiting the adoption of hybrid rice. Grain quality of three-line hybrid rice varieties has been improved remarkably in China. High-yielding three-line hybrid varieties such as Boyou 64, Xieyou 63 and Xieyou 64 have good grain quality and You I 63 and You I 64 have a medium to long grain. Together they occupied about 8 percent of the total area planted to hybrid rice in China in 1992. Recently, aromatic indica CMS and maintainer lines, e.g. Xiang A and B, have been developed. Three-line hybrid combinations such as Xiang A/PH137, Xiang A/F50 and Xiang A/F117 have a high percentage of aromatic grains and yields which are similar to most of the non-aromatic hybrid rice varieties planted at present (Zhou, 1995). The hybrid rice varieties developed by IRRI and India also have acceptable grain quality (Ahmed, 1997).
F1 seed yield. In China, F1 seed yield increased from 0.41 tonnes/ha in 1976 to 0.67 tonnes/ha in 1981, 1.29 in 1983, 1.99 in 1986, 2 in 1989, 2.25 in 1991 and 2.5 in 1995 (Yuan and Fu in FAO, 1995; Zhou, 1995). In Viet Nam, yields of F1 seeds have increased from about 302 kg/ha in 1992 to about 1 751 kg/ha in 1996 (Quach, 1997). During 1996, about 1 300 tonnes of hybrid rice seed were produced in India (Ahmed, 1997). The increase in F1 seed yields is attributable to improved seed production technology, seed producers' increased experience with parental lines and the improved selection of location and season for F1 seed production.
Field area ratios. The field area ratio between CMS line multiplication, hybrid seed production and commercial production of three-line hybrid rice varieties in China has steadily increased as a result of a seed yield increase from 1:30:1 000 in the 1970s to 1:50:3 000 in the 1980s, 1:50:5 000 in the early 1990s and 1:50:6 000 in 1995 (Mao, 1993; Zhou, 1995).
Crop management techniques in commercial hybrid rice production. Location-specific packages of production techniques have been developed for high yields of commercial hybrid rice cultivation. Agronomic practices developed and recommended for commercial hybrid rice cultivation include: close spacing; timely application of nitrogen fertilizers; improved nursery bed management techniques; deep irrigation (about 20 cm) at 20 days after panicle initiation to depress unproductive tillers; and application of about 10 to 20 percent of the total nitrogen dose at the heading stage.
Two-line hybrid technology
In China, to break the yield ceiling of three-line hybrid rice varieties, research and development on two-line hybrid rice has been initiated. In 1983, the photoperiod-induced male sterility in rice was found in Hubei Province (China) and, in 1987, the wild compatibility gene between japonica and indica rice was found in Japan. About 11 usable S lines (two japonica PGMS and nine indica TGMS) have been developed and registered and five two-line hybrid rice varieties have been released for cultivation in China. The area under two-line hybrid rice varieties in China increased from about 60 000 ha in 1994 to about 330 000 ha in 1996 (Yuan, 1996). The two-line hybrid varieties have a yield advantage of 5 to 10 percent over the commercially cultivated three-line hybrid varieties, i.e. about 20 to 30 percent over the best modern rice varieties.
The F1 seed yield of two-line hybrid rice varieties ranges from 2.25 to 3 tonnes/ha. In the two-line system, there is no need for a maintainer line. The field area ratio between CMS line multiplication, hybrid seed production and commercial production of two-line hybrids is therefore much higher than that of three-line hybrid rice varieties (1:100:15 000 for two-line varieties compared with 1:50:6 000 for three-line hybrids). This lowers the cost of F1 seed production. The key point in two-line hybrid seed production is to determine the time when the PGMS or TGMS line will show complete sterility for about one month at a given location. For varieties developed from a TGMS line, seed production should be carried out in areas or zones with one month of stable temperatures of about 22°C or less in temperate climates and about 24°C or less in subtropical conditions. This is to prevent the development of fertile pollens in flowers of temperature-induced male sterile lines and thus a low percentage of F1 seeds (Yuan, 1996).
In tropical countries, TGMS hybrid rice varieties appear to be more promising than PGMS lines. In these countries the variation in day length is not substantial whereas the difference in temperature owing to differences in latitude and altitude is substantial. The TGMS gene of the IRRI mutant, IR32364 TGMS, was found to be non-allelic to the TGMS genes identified in China (tms 1) and Japan (tms 2). IRRI has developed several two-line hybrid rice varieties from the tms 2 gene for countries in tropical Asia (Lu, Virmani and Yang, 1996).
Development of one-line hybrids
Apomixis. Apomixis or one-line hybrids would enable farmers to use their own seed for the successive crops without experiencing genetic segregation or depression. However, the evolution and wide application of this innovative technology are not likely to occur in the next decade.
Other developments in hybrid rice technology
Increased heterosis. Most of the released hybrid rice varieties are intervarietal, e.g. indica x indica, japonica x japonica. The finding of the wide compatibility (WA) gene (S-5n) by Ikehashi and Araki in 1984, together with embryo rescue techniques, has facilitated intersubspecies hybridization, for example japonica x indica. Heterosis in hybrid rice varieties has the following order: indica x japonica> indica x javanica> japonica x javanica> indica x indica> japonica x japonica (Yuan, 1996). The hybrid rice lines resulting from the cross between indica and temperate japonica still have to be improved from the point of view of plant height, sterility and growth duration. Considerable advances, however, have been obtained by IRRI in the development of tropical japonica (javanica) rice varieties.
Rice biotechnology. Progress has been made in the establishment of a high-density map of about 2 000 molecular markers; the preparation of a physical map of the rice genome; and the establishment of an international database of rice genes (IRRI, 1995). These achievements will undoubtedly facilitate the understanding of rice genetics, i.e. the inheritance of important traits in both cultivated and wild rice species, and may also lead to the development of new sources of cytoplasmic sterility, the breeding of B and R lines and the new generation of hybrid rice varieties. Studies have also been done on factors affecting male sterility and wild compatibility in cultivated and wild rice species that are geographically distant as well as the molecular transfer of male sterility to cultivated rice varieties. Progress has been made in the development of transgenic rice plants with a high level of resistance to insects (stem borer, brown planthopper); diseases (tungro virus, rice yellow stunt virus, blast, bacterial blight); herbicide (Glufosate); and abiotic stresses (salinity and drought); as well as better nutritional value (e.g. glutelin, vitamin A) and higher yield. Some transgenic rice plants have already been subject to evaluation under field conditions; however, techniques and approaches to molecular breeding still need to be perfected and made more efficient, accurate and less costly, especially for indica rice. Scientists have made great contributions to the development of innovative rice technologies, but the concrete outcome of these efforts will only be seen at the beginning of the next century.
WORLD'S HYBRID RICE DEVELOPMENT AND USE
Bangladesh
The Bangladesh Rice Research Institute (BRRI) started hybrid rice research and development in 1993. In the boro season of 1996/97, BRRI found IR67684A, IR68281A, IR68275A to be stable (Julfiquar et al., 1997). A number of hybrid rice varieties developed in India have been widely evaluated under field conditions by the extension service in the country. The hybrid programme at BRRI has been assisted by the FAO project TCP/BGD/6613 (T) - Development and Use of Hybrid Rice.
Brazil
EMBRAPA/CNPAF began to explore the prospects and problems of hybrid rice in 1984 in a programme based on the three-line method, using wild abortive cytoplasm and the long stigma traits transferred from O. longistaminata A Chev. to improve cross pollination. The CMS line, 0461, with good allo-gamic trait and good agronomic properties and several hybrid rice varieties were developed (Guimaraes et al., 1996).
Colombia
Research began in 1983 in cooperation with IRRI. CMS lines and hybrid rice lines developed by IRRI and to a lesser extent by China were evaluated and an attempt is being made to transfer cytoplasmic male sterility in Zhenshan 97A and V20A to Colombia 1, a local élite variety. The objectives of Colombia's hybrid rice programme are to develop hybrid rice with a 15 to 20 percent yield advantage, good grain appearance and good cooking quality (Munoz, Guitierrez and Corredor, 1996).
Ecuador
The national hybrid rice programme was started in 1995 by testing hybrid lines and CMS lines provided by IRRI through an FAO-assisted regional working group (Nguyen, 1996).
Egypt
Hybrid rice research began in 1982, and studies revealed that Egyptian japonica has little or no fertility-restoring ability in the WA CMS. Yields of hybrid rice lines tested between 1986 and 1994 were either comparable or inferior to those of local high-yielding varieties. In 1995, however, some hybrid rice lines were found to have a yield advantage of about 5 to 16 percent over the best local varieties. The national average yield in 1995 was more than 8 tonnes/ha (Bastawisi et al., 1996).
France
French hybrid rice research has been carried out by CIRAD/IRAT, which started in 1981 at Montpellier and continued from 1984 to 1989 in a project in Goiânia, Brazil, in collaboration with EMBRAPA/CNPAF. Further work was started in 1990 in French Guiana. The hybrid rice programme aimed at developing varieties for irrigated conditions in tropical countries of South America and in countries with a Mediterranean climate. Hybrid seed production is done in cooperation with private companies (Taillebois et al., 1994).
India
Efforts to develop and use hybrid rice were initiated in the 1970s and have been systematized since 1989. Under the leadership of the Director-General of the Indian Council of Agricultural Research (ICAR), hybrid breeding and seed production research is being carried out by a network of 12 agricultural research institutes throughout the country, and activities have been strengthened by an FAO/UNDP-funded project. A dozen three-line hybrid rice varieties have been released by the public and private sectors for commercial cultivation and more than 80 000 ha were planted to hybrid rice in 1997. Seed production technology has been developed and demonstrated on a wide scale, with seed yields in the range of 1 to 1.5 tonnes/ha, and about 1 300 tonnes of F1 seeds were produced during the 1996 dry season. Research on two-line breeding and development of intersubspecific indica x tropical japonica hybrid rice varieties have been initiated (Ahmed, 1997).
Indonesia
The hybrid rice programme began in 1983, and Chinese CMS varieties such as Zhenshan 97, V20A, and V41A were found to be stable for pollen sterility, although they are susceptible to most insects and diseases, particularly sheath rot. The CMS varieties introduced by IRRI are more stable but have poor combining ability, outcrossing rates and unstable sterility. Several Indonesian CMS lines such as IR79774A, IR19809A, Tondano A and M8601 A have been developed, while the hybrid lines IR58025A/IR53942 and IR58025A/BR827 have been proposed for multilocational evaluation (Suprihatno, Satato and Harahap, 1997).
Japan
Hybrid rice has been studied since the 1950s. Cytoplasmic male sterility is obtained from Oryza sativa spontanea and an indica variety, namely Chinsurah Boro II. The Ministry of Agriculture, Forestry and Fisheries started its hybrid rice programme in 1983 and the National Federation of Agricultural Cooperative Associations (Zen-Noh) and several private companies are also developing hybrid rice varieties.
The national programme aims at producing high and stable indica x japonica and japonica x japonica hybrid rice varieties that satisfy Japanese cooking quality requirements (Ton That, 1994).
People's Democratic Republic of Korea
The development of intersubspecific hybrid rice was initiated in 1983 and research concentrated on problems of nuclear sterility, cold damage, poor grain quality and early senility in F1 generations and low F1 yields in seed production (Lee and Mun, 1996).
Republic of Korea
The country's breeding programme began in 1982 and a Korean-IRRI collaborative project on hybrid rice was established in 1984. The top experimental hybrid rice lines have yielded 9.1 to 12.1 tonnes/ha over the last ten years, with an advantage of 21 percent over leading check varieties. Cytoplasmic male sterile lines have been developed by transferring WA-CMS and COA-MS sources into Korean varieties. Some Tongil-type cultivars and lines are good maintainers for both WA-CMS and COA-MS but no japonica has been identified as a restorer. An attempt has been carried out to develop japonica restorer lines by anther culture (Moon, Heu and Kim, 1994).
Malaysia
Hybrid rice research was initiated in 1984 by the MARDI. Local CMS lines were by backcrossing and two hybrid rice lines, IR62829A/IR46R and MH841-1A/MR 167, were found to have a yield advantage of about 24 to 26 percent over the best local check in 1995/96. An effort is being made to produce large quantities of CMS and F1 seeds for cultivation (Guok et al., 1997).
Myanmar
Myanmar's hybrid rice research started in 1991. CMS lines IR 62829A and IR58025A were identified as adaptable to local conditions and have high and stable sterility. The programme was recently assisted by the FAO project TCP/MYA/6612 (T) - Training in hybrid rice technology (Tin Win, 1997).
The Philippines
In 1989, the Philippine Rice Research Institute started a hybrid rice breeding project with the objective of developing hybrid varieties with a yield advantage of 15 percent or more over the best pure lines. IR58025A and IR 62829A, developed by IRRI, were found to have good adaptability and stability of pollen sterility. CMS lines of Dian, STB and ZTB types were recently introduced from China and the hybrid variety, Maggat, was released by the private company Cargil in the early 1990s. More recently, the National Technical Working Group for Rice to the National Seed Industry Council recommended IR 68284H (IR58025A/IR3486-179-1-2-1R) for release to farmers (Redoña et al., 1997).
Sri Lanka
The main activities of the country's hybrid rice research programme started in the 1980s, including the evaluation of promising CMS lines introduced from IRRI and from other countries and the transfer of cytoplasmic male sterility from IRRI-developed lines to Sri Lankan lines (Abeysiriwardena, Abeysekera and Dhanapala, 1997).
Thailand
Hybrid rice research started in 1979, and cytoplasmic male sterility from IRRI's CMS was transferred to Thai varieties. Hybrid rice lines from China and IRRI were also tested (Amorsilpa, Potipibool and Noojoy, 1994).
United States
Both the public and private sectors are involved in hybrid rice research, which has focused on evaluating levels of heterosis, developing seed production systems and searching for apomixis. As the three-line system is too laborious, priority has been given to the development of two-line hybrid varieties, especially using PGMS lines created through mutation breeding. The EUI (elongated uppermost internode or recessive tall) gene was identified for breeding the pollinator parent to facilitate outcrossing (Mackill and Rutger, 1996).
Venezuela
The hybrid rice programme started in 1996 with the testing of hybrid rice lines and CMS lines provided through the Working Group on Hybrid Rice in Latin America and the Caribbean (GRUTHA), in collaboration with IRRI (Nguyen, 1996) .
Viet Nam
Hybrid rice research began in 1983 with the objective of evaluating CMS lines, identifying respective maintainer and restorer lines; improving F1 seed production; and evaluating hybrid rice varieties developed in China and by IRRI. In the late 1980s, the national hybrid rice programme was placed under the leadership of the Minister of Agriculture and Rural Development. In addition to two FAO TCP projects, the government has provided a budget of about US$300 000 annually. Hybrid rice varieties such as Shanyou 63, Shanyou gui 99, Jinyou 63, Boyou 64, Trang Nong 15 were released for commercial cultivation. The area planted to hybrid rice increased from about 11 000 ha in 1992 to about 102 000 ha in 1996. Progress was also made in F1 seed production. Seed production increased from about 302 kg/ha in 1992 to about 1 751 kg/ha in 1996 (Quach, 1997).
Common constraints
Most of the national hybrid rice development programmes outside China, with the possible exception of India's, still have inadequate human resources, expertise and funding. The scientists and researchers deployed to hybrid rice development programmes are rather limited in number and their expertise on hybrid rice breeding and F1 seed production still needs to be improved through training. Funding for hybrid rice research and development in many countries is still low.
Also, the adoption of hybrid rice for commercial cultivation in many Asian countries is still constrained by the absence of a vigorous seed production sector. The collaboration between public research, seed production and extension institutions and private seed production companies in these countries needs to be encouraged. The Indian experience has indicated that well-organized farmers' associations and agriculturally oriented non-governmental organizations could effectively contribute to the F1 seed production provided that training programmes are available to them.
FAO'S GLOBAL HYBRID RICE ACTIVITIES
The programme before the 18th Session of the IRC
Initial phase. Since 1979, FAO has monitored the development and use of hybrid rice technologies in China. In 1983, FAO discussed the development of japonica hybrid rice technologies in the United States with the staff of the rice programme in Beaumont, Texas. At the 16th Session of the International Rice Commission (IRC) (the Philippines, 1985) and the 17th Session of the IRC (Brazil, 1990), FAO presented documents and drew the attention of the world's rice community to the feasibility of hybrid rice in closing the gap between production and demand, particularly in overpopulated and land-scarce countries. In 1989, FAO assisted the formulation of a project on hybrid rice technology development and use in India which was implemented in 1991 with UNDP financial support.
1990-1991. FAO assisted the Cuu Long Rice Research Institute in the Mekong Delta and Viet Nam Agricultural Science Institute in the Red River Delta to test stable CMS, maintainers, restorers and hybrid rice varieties developed by IRRI. The Organization fielded three consultancies to promote the innovative two-line breeding method in Indonesia, Viet Nam, Colombia and Brazil and provided technical assistance in hybrid rice development and use in Viet Nam and Indonesia.
1992-1993. FAO assisted EMBRAPA in Brazil to refine the CMS system in connection with IRAT/EMBRAPA's research and, through a TCP project, supported the training of Vietnamese rice scientists in hybrid rice breeding and seed production at various rice institutes in China. It also provided support to the hybrid rice development programme in Egypt, and, in collaboration with national programmes, set up GRUTHA.
18th Session of the IRC
The delegates at the 18th Session of the IRC, which took place in Rome, Italy from 5 to 9 September 1994, recommended that:
The programme after the 18th Session of the IRC
Since then the promotion of hybrid rice development and use outside China has become the most important component of FAO's rice programme and covers the following areas:
Field projects. FAO continued to provide technical assistance through the project IND/91/008 - Hybrid Rice Development and Use Technologies in India. It funded consultancy missions to review the hybrid rice development programme in Bangladesh and Myanmar, resulting in two TCP projects: TCP/BGD/6613 (T) - Development and Use of Hybrid Rice in Bangladesh and TCP/MYA/6612 (T) - Training in Hybrid Rice Technology in Myanmar. It also organized the project TCP/VIE/6614 (T) - Strengthening National Capacity for Hybrid Rice Research and Hybrid Seed Production Technology in Viet Nam, and set up the project TCP/PHI/8813 to provide support for the development and use of hybrid rice in the Philippines.
Support to national programmes and regional and international networks. FAO provided contractual services to assist national hybrid rice programmes in Brazil and Viet Nam and supported study tours for rice breeders in Colombia and Brazil to observe hybrid rice development in China. It participated in and provided technical and financial support to the Third International Symposium on Hybrid Rice, held in Hyderabad, India, as well as the second meeting of the Working Group on Hybrid Rice in Latin America and the Caribbean (GRUTHA) in Colombia in 1996 and the First International Workshop on Hybrid Rice Development and Use Outside China, organized by the Ministry of Agriculture and Rural Development of Viet Nam in May 1997 in Hanoi.
Establishment of the International Task Force on Hybrid Rice (INTAFHOR). In collaboration with national programmes, in 1995 FAO and IRRI established INTAFHOR, which met for the first time in India in 1996. In collaboration with FAO, IRRI formulated a project to support activities in hybrid rice development and use in some Asian members of INTAFHOR. Financing for this project has been approved by the Asian Development Bank and will soon be implemented by IRRI, FAO and member countries.
Provision of technical guidelines. FAO has published Technology of hybrid rice production, by Long-ping Yuan and Xi-Qin Fu, and Global assessment of hybrid rice technologies for breeding and seed production, by K.R. Chopra, to provide guidelines on hybrid rice breeding and seed production to breeders of national programmes in FAO member countries.
PROMOTING HYBRID RICE OUTSIDE CHINA: LESSONS LEARNED
The success of a national hybrid rice programme is usually determined by developmental and technological factors (Tran, 1997).
Developmental issues
Strong government support. As seen in the implementation of the hybrid rice programmes in Viet Nam and India, an enthusiastic high-ranking person in the national research or development agency concerned could provide strong support in terms of personnel and finance and also moral support in this activity. In Viet Nam, the Ministry of Agriculture and Rural Development and Minister Nguyen Cong Tan have always supported the promotion of hybrid rice in the country. In India, R.S. Paroda, Director-General of ICAR, has provided strong support to the hybrid rice research programme coordinated by the Directorate of Rice Research and has encouraged the participation of private seed companies in this area. UNDP funding through the five-year project IND/91/008 - Development and Use of Hybrid Rice Technologies has also contributed to the success of the hybrid rice programme in India.
Strong linkage between hybrid rice research, F1 seed production and extension. At the initial stage of hybrid rice programmes, research plays an important role in the development of technologies for breeding and F1 seed production. When the programme enters the expansion phase with large-scale production, the multiplication of parental lines and F1 seed production - especially for foundation and registered seeds - will become more demanding. Extension delivery services will be essential for promoting farmers' participation in the hybrid rice programme.
Strengthened national capacity in hybrid breeding and F1 seed production. A successful hybrid rice programme requires adequately skilled human resources specializing in hybrid rice breeding as well as F1 seed production. Hence, training activities should always be given high priority and be aimed at upgrading the national capacity in this field. This could be facilitated using technical cooperation among developing countries in the framework of the FAO/TCDC programme.
Strong F1 seed production industry. The widespread expansion of hybrid rice programmes requires a strong domestic seed industry. The government should create incentives so that private seed companies alleviate its burden of having to produce a large amount of F1 seeds.
Technological issues
Superiority of hybrid rice varieties. Hybrid rice varieties should demonstrate heterosis clearly and consistently, give superior yields to those of common semi-dwarf varieties, have an acceptable level of resistance to the main insects and diseases found in the cultivation area, and have a grain quality that is acceptable to the local population.
Stable hybrid rice varieties and F1 seeds. It is known that the purity of parental lines and F1 seeds is the most important factor determining the retention of heterosis in hybrid rice. It has been reported that every percentage point of genetic impurity in F1 seeds could reduce hybrid rice yields by about 100 kg (Yuan, 1985). The rigorous maintenance of genetic purity in parental lines and F1 seeds is essential to safeguard the heterotic superiority of rice hybrids and high seed yields.
Reasonable price of F1 seeds. The high price of F1 seeds is the major obstacle to the adoption of hybrid rice technologies by farmers, especially those who are poor. F1 seed production, therefore, has to be continually improved with the aim of obtaining higher yields and lower prices of F1 seeds. The use of gibberellin (GA3) chemical and other techniques such as heading synchronization are particularly important in seed production. The development of two-line methods using the environment-sensitive genic male sterility (EGMS) system will increase the heterosis of hybrids and reduce the costs of hybrid seed production, encouraging farmers' wide adoption.
Hybrid rice technology still has the opportunity to reach higher yield levels by using the two-line method, intersubspecific hybrids and the new plant type (or super rice). However, many national hybrid rice programmes have experienced technological difficulties in trying to maintain the purity of CMS and maintainer lines for the large-scale production of breeder and foundation seeds, and also in the organization of F1 seed production. The challenges for hybrid rice specialists are how to maintain and increase heterosis, simplify hybrid seed production technologies and increase F1 seed yields as well as to win the government's attention and the participation of private seed companies.
Most of the national hybrid rice development programmes outside China still have inadequate human resources and expertise. More national and international efforts and resources, especially for the training of national programme staff, should be directed towards the development and use of hybrid rice.
REFERENCES
Abeysiriwardena, D.S. de Z., Abeysekera, S.W. & Dhanapala, M.P. 1997. Current status of research and development of hybrid rice technology in Sri Lanka. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Ahmed, M.I. 1997. Development and use of hybrid rice technology - Lessons learned from the Indian experience. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Amorsilpa, S., Potipibool, S. & Noojoy, S. 1994. Hybrid rice research in Thailand. In S.S. Virmani, ed. Hybrid rice technology: new developments and future prospects, p. 213-216. Los Baños, the Philippines, IRRI.
Bastawisi, I.R., Aidy, El-Mowafy, H.F. & Maximos, M.A. 1996. Current status of research and development of hybrid rice technology in Egypt. Paper presented at the Third International Symposium on Hybrid Rice, 14-16 November 1996, Hyderabad, India.
FAO. 1995. Technology of hybrid rice production. By L.P. Yuan & X.Q. Fu. Rome. 84 pp.
Guimaraes, V., Dos, Cutrim, A. & Mendonca, J.A. 1996. Hybrid rice development in Brazil: methodology, highlights and prospects. Paper presented at the Third International Symposium on Hybrid Rice, 14-16 November 1996, Hyderabad, India.
Guok, H.P., Kato, H., Azlan, S. & Ku Yahaya, K.H. 1997. Progress in the development and use of hybrid rice technologies in Malaysia. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Hiei, Y. & Komari, T. 1996. Stable inheritance of transgenes in rice (Oryza sativa L.) plants transformed by Agrobacterium tumefaciens. In Proceedings of the Third International Rice Genetics Symposium, IRRI, Los Baños, Philippines, p. 131-142.
Ikehashi, H. & Araki, H. 1984. Varietal screening of compatibility types revealed in F1 fertility of distant crosses in rice. Jap. J. Breed., 34: 304-313.
IRRI. 1995. Rice Genetics III. Los Baños, the Philippines. 1011 pp.
Julfiquar, A.W., Haque, M.M., Enamul Haque, A.K.G.M., Bashar, M.K. & Rashid, M.A. 1997. Hybrid rice research in Bangladesh. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Lee, U.B. & Mun, J.W. 1996. Current status of exploring intersubspecific hybrid rice in the People's Democratic Republic of Korea. Paper presented at the Third International Symposium on Hybrid Rice, 14-16 November 1996, Hyderabad, India.
Lin, J.Y. & Pingali, P.L. 1994. Economic assessment of the potential for hybrid rice in tropical Asia: lessons from the Chinese experience. In S.S. Virmani, ed. Hybrid rice technology: new developments and future prospects, p. 131-142. Los Baños, the Philippines, IRRI.
Lu, X., Virmani, S.S. & Yang, R. 1996. Advance in two-line hybrid rice breeding. Paper presented at the Third International Symposium on Hybrid Rice, 14-16 November 1996, Hyderabad, India.
Mackill, D. & Rutger, J.N. 1996. Current status of research on hybrid rice technology in USA. Paper presented at the Third International Symposium on Hybrid Rice, 14-16 November 1996, Hyderabad, India.
Mao, C.X. 1993. Hybrid rice production in China - New successes, challenges and strategies. Paper presented at the FAO Regional Expert Consultation on Hybrid Seed Production, Development and Security of Major Cereal Crops, 9-12 November 1993, Bangkok, Thailand.
Moon, H.P., Heu, M.H. & Kim, C.H. 1994. Hybrid rice research in the Republic of Korea. In S.S. Virmani, ed. Hybrid rice technology: new developments and future prospects, p. 217-226. Los Baños, the Philippines, IRRI.
Munoz, P., Guitierrez & Corredor, E. 1996. Current status of research and development of hybrid rice technology in Colombia. Paper presented at the Third International Symposium on Hybrid Rice, 14-16 November 1996, Hyderabad, India.
Nguyen, T.H. 1997. Current status of hybrid rice research and development in Viet Nam. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Nguyen, V.N. 1996. Report - Mission backstopping GRUTHA. November 1996.
Pham, T.H. 1997. Results of Trang Nong Hybrid Rice Development Programme in Central and South Viet Nam. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Quach, N.A. 1997. Some experience in the development of hybrid rice production in Viet Nam. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Redoña, E.D., Malabanan, F.M., de la Cruz, I.A, Ablaza, S.M.F., de Leon, J.C. & Obien, S.R. 1997. Current hybrid rice work issues and opportunities in the Philippines. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Suprihatno, B., Satato & Harahap, Z. 1997. Progress of research and development of hybrid rice technology in Indonesia. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Taillebois, J., Jacquot, M., Clement, G., Guideroni, E., Courtois, B., Seguy, L. & Bouzinac, S. 1994. Hybrid rice research at CIRAD/IRAT. In S.S. Virmani, ed. Hybrid rice technology: new developments and future prospects, p. 253-256. Los Baños, the Philippines, IRRI.
Tin Win. 1997. Prospects of hybrid rice in Myanamar. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Ton That, T. 1994. FAO's contribution to hybrid rice development. In S.S. Virmani, ed. Hybrid rice technology: new developments and future prospects, p. 267-274. Los Baños, the Philippines, IRRI.
Tran, D.V. 1997. FAO global hybrid rice development programme. Paper presented at the International Workshop on Progress in the Development and Use of Hybrid Rice Outside China, 28-30 May 1997, Hanoi, Viet Nam.
Virmani, S.S. 1996. Hybrid rice. Adv. Agron., 47: 377-462.
Yuan, L.P. 1985. A concise course in hybrid rice. China, Hunan Science and Technology Publishing House.
168 pp.
Yuan, L.P. 1996. Hybrid rice in China. In Hybrid rice technology, p. 51-54. Hyderabad, India, DRR.
Zhou, K.L. 1995. The latest achievements in hybrid rice research and extension in China. Changsha, Hunan, China National Hybrid Rice Research and Development Centre. 5 pp. (monograph)
Le riz hybride dans le monde: progrès, problèmes et défis
Les bons résultats de la production commerciale de riz hybride en Chine montrent clairement que cette solution est actuellement la seule qui permettra d'accroître le niveau stationnaire des rendements. L'exploitation des techniques d'obtention de riz hybride améliore la production, réduit la pauvreté rurale tout en respectant l'environnement. Le Viet Nam a planté récemment du riz hybride sur quelque 102 000 ha, et l'Inde sur 65 000 ha en 1996. Des progrès considérables ont été réalisés dans la sélection des lignées parentales, la mise au point des variétés hybrides et l'amélioration du rendement de la production de semences F1. Les variétés de riz hybride récemment mises au point ont des origines génétiques plus diversifiées, des rendements élevés et stables et une qualité de grain acceptable. En Chine, le rendement des semences F1 est passé de 0,41 tonne à l'hectare en 1976 à environ 2,5 tonnes à l'hectare en 1995. Au Viet Nam et en Inde, les rendements des semences F1 étaient d'environ 1,5 tonne à l'hectare en 1996. Des variétés obtenues par hybridation double, qui ont un rendement supérieur de 5 à 10 pour cent à celui des variétés à hybridation triple actuellement cultivées, ont été mises au point et commercialisées avec succès en Chine.
Des efforts de mise au point et d'utilisation des technologies d'hybridation ont également été entrepris dans des pays autres que la Chine, en particulier le Bangladesh, le Brésil, la Colombie, l'Egypte, la France, l'Inde, l'Indonésie, le Japon, la République de Corée, le Myanmar, les Philippines, la Thaïlande, les Etats-Unis, le Viet Nam, etc. Cependant, ces technologies sont assez complexes et longues à mettre au point et nécessitent de grandes compétences en matière de sélection des hybrides et de production de semences F1. L'élaboration et l'utilisation fructueuses du riz hybride nécessitent un fort appui des gouvernements, un engagement de la part des scientifiques, une coopération entre les programmes de recherche, les secteurs de la production semencière et de la vulgarisation, et une collaboration internationale. C'est pourquoi, en 1986, la FAO a mis au point son programme mondial sur le riz hybride pour accélérer l'utilisation généralisée des technologies d'hybridation hors de Chine. Ces technologies pourraient encore permettre d'obtenir des rendements plus élevés. Mais, dans la plupart des pays (Chine exclue), ces programmes manquent de personnel et de compétences. Il faudrait consacrer davantage d'efforts et de ressources aux plans national et international pour soutenir l'élaboration et l'utilisation de riz hybride, notamment par la formation du personnel des programmes nationaux et l'amélioration des systèmes de production et de multiplication des semences F1.
Progresos, problemas y desafíos del arroz híbrido en el mundo
El éxito de la producción comercial de arroz híbrido en China demuestra claramente que en la actualidad el arroz híbrido es el único instrumento práctico para aumentar el rendimiento del arroz ahora estabilizado. La utilización de la tecnología del arroz híbrido permite aumentar la producción arrocera y reducir la pobreza rural y no tiene efectos para el medio ambiente. Fuera de China, se han plantado recientemente unas 102 000 ha en Viet Nam y unas 65 000 ha en la India en 1996. Se han realizado progresos notables en la selección de líneas parentales, la obtención de variedades híbridas y el aumento del rendimiento de la producción de semillas F1. Las variedades de arroz obtenidas últimamente tienen orígenes genéticos más diversificados, rendimientos altos y estables y una calidad de grano aceptable. En China, el rendimiento de las semillas F1 aumentó de 0,41 t/ha en 1976 a unas 2,5 t/ha en 1995. En Viet Nam y la India, los rendimientos de las semillas de F1 fueron de unas 1,5 t/ha en 1996. En China se han creado y cultivado comercialmente con éxito variedades híbridas de dos líneas con un rendimiento superior en un 5-10 por ciento al de las variedades híbridas de tres líneas actualmente cultivadas.
También se están realizando crecientes esfuerzos para fomentar y utilizar tecnologías de arroz híbrido en otros países como Bangladesh, Brasil, Colombia, Egipto, Estados Unidos, Filipinas, Francia, India, Indonesia, Japón, Mianmar, República de Corea, Tailandia, Viet Nam, etc. Sin embargo, la tecnología del arroz híbrido es compleja y lenta y exige conocimientos muy especializados de selección de híbridos y producción de semillas F1. Para obtener y utilizar con éxito el arroz híbrido es necesario un firme apoyo de los gobiernos, un compromiso de los científicos, una cooperación entre programas de investigación, sectores de producción de semillas y servicios de extensión, y una colaboración internacional. Por consiguiente, la FAO inició en 1986 su programa mundial para acelerar la aplicación generalizada de tecnologías de arroz híbrido fuera de China. Esta tecnología sigue ofreciendo oportunidades para conseguir rendimientos más altos. Sin embargo, casi todos los programas nacionales de fomento del arroz híbrido fuera de China adolecen todavía de falta de personal y de competencia técnica. Serán necesarios más esfuerzos y recursos nacionales e internacionales para impulsar la obtención y utilización de arroz híbrido, especialmente mediante la capacitación de personal de programas nacionales y la mejora de los sistemas de multiplicación y producción de semillas F1.
