Hybrid rice: progress, issues and outlook
for Bangladesh

M.A. Hamid Miah^a and N.P. Sarma^b

^a Bangladesh Rice Research Institute, Dhaka, Bangladesh; ^b Directorate of Rice Research, Hyderabad, India

Today's world population of 5.9 billion people is expected to reach 9 billion within a quarter of a century from now. Global food production needs to be doubled in order to feed this escalating population. Rice provides food and livelihood security in many Asian countries, including Bangladesh, where it is the principal staple food of the people. Soon the demand for rice in these countries will outstrip production. The current level of foodgrain production in Bangladesh is about 20.3 million tonnes, of which rice alone accounts for 18.04 million tonnes. With declines in the growth of rice production over the years, the country already has a foodgrain deficiency of 2 million tonnes and, to balance the food budget with the growing population, growth in rice production at a rate of at least 2.5 percent per annum is needed. The rice production scenario in other major rice growing countries, with the exception of China, is no different.

In Asian countries, which account for 90 percent of world rice area and production, most of the arable land suitable for rice cultivation has been exploited. Land and water for rice production may still be available in Africa and Latin America. With no possibility to extend the land frontier in Asia, there is some scope for production advances in rice through further expansion of high-yielding variety (HYV) coverage (Pakistan, India and Thailand), expansion of area under irrigation (Bangladesh, Cambodia, India, Myanmar, the Philippines, Thailand and Viet Nam) or expansion of boro rice cultivation (India, Bangladesh and Myanmar). Pingali, Hossain and Gerpacio (1997) describe how productivity gains from the exploitation of green revolution technologies are close to exhaustion and an upward shift in rice yields is necessary if future rice requirements are to be met and rice farming sustained as a profitable enterprise. The technological options for such a shift in yield frontier or for raising the genetic yield ceiling are: exploitation of hybrid vigour, improvement of plant types, identification and utilization of favourable quantitative trait locus (QTL) genes for yield, and engineering of increased starch biosynthesis.

Recent breakthroughs in tropical hybrid rice technology provide an economically viable option for raising the yield and sustaining future production growth. The hybrid rice technology developed in China and being adopted elsewhere has proved beyond doubt that hybrid rice has the potential to increase yields by 15 to 20 percent over those of conventionally bred varieties. This technology helped China, not only to produce more rice in a matter of two decades (Table 1), but also to save land for crop diversification. Major rice producing countries outside China are now trying to adopt the technology, and countries such as India and Viet Nam have already made headway in the development and large-scale cultivation of hybrid rice. The new technology is, therefore, very important for rice growing countries where the population is high, there is no future scope for the expansion of arable land and labour costs are still manageable. A country such as Bangladesh, where there is an acute shortage of land and a dire need to transform from monocrop rice-rice cultivation to more diversified cropping systems, should carefully weigh the options and scope for adopting frontier technologies, beginning with hybrid rice technology for increasing rice production.

Hybrid vigour, or heterosis, is the basis for the yield advantage of hybrids over conventional varieties. Vigour at the initial growth stage is the principal trigger of heterosis. It is the ability of a hybrid to absorb and synthesize assimilates more efficiently that causes its superior growth and yield. Stronger and more active root systems and early vegetative vigour may also confer advantage under situations of abiotic stress.

The development of hybrid rice involves evaluation of the degree of heterosis for yield; development of hybrid combinations and testing; and development of parental lines and techniques for seed production. Cultivated rice has traditionally been improved as a self-pollinated plant. In nature heterosis occurs primarily in cross-pollinated plants and its evolution is considered to be a heterozygous advantage. The heterosis that is observed in hybrids of improved rice cultivars might be a relic of the long evolution of cross-pollinated wild rices prior to domestication (Fujimaki and Matsuba, 1997). Heterosis in open-pollinated crops such as maize, sorghum and pearl millet was exploited much earlier, owing to the obvious advantage of these crops' pollination systems for the production of hybrids on a commercial scale. Although heterosis was reported in several intervarietal crosses of rice, the self-pollinating system of the rice plant, with its tiny florets, did not facilitate the production of hybrid seed in bulk in the absence of a genetic emasculation technique.

To produce hybrids on a commercial scale, it is essential to change the function of the male and female reproductive system of rice plants. Seed parent cultivars need to be male-sterile (i.e. no functional pollen). F₁ hybrids should exhibit a high level of fertility. The pollen parent of the hybrid should have the genetic ability of rendering the male sterility of the seed parent ineffective, i.e. the capability to restore complete fertility in the hybrid (restoration). A breakthrough came with the discovery and development of the cytoplasmic-genetic male sterility system from a wild rice in 1964 (Yuan, 1966). The genetic tools essential for production of hybrid rice - male sterile (A) line, maintainer (B) line and restorer (R) line - were developed in 1973 in China, and in 1976 the first batch of hybrid rice was released.

China's success with hybrid rice encouraged the development of this technology for the tropics. Realizing that hybrid rice technology was an important option for increasing rice yields, the International Rice Research Institute (IRRI) relaunched its research into hybrid rice development for the tropics. Outside China, 17 countries are now endeavouring to develop hybrid rice. IRRI has been instrumental in developing and sharing commercially usable, stable cytoplasmic male sterile (CMS) lines adopted in the tropics, and in imparting training in hybrid rice seed production technology for many of the rice growing countries in Asia. As a result, countries such as India, Viet Nam and the Philippines have made good progress in commercializing hybrid rice. Several other countries are on the verge of developing hybrid rice technology. The opportunities for hybrid rice technology outside China, the anticipated area coverage of hybrids and the expected gains in rice production are shown in Table 2.

FAO saw hybrid rice technology as an important avenue for increasing global rice production. In collaboration with IRRI, the China National Hybrid Rice Research Development Centre (CNHRRDC) and other national programmes, the Organization initiated a global hybrid rice programme in 1986 to expedite the widespread use of hybrid rice technology outside China. (Tran, 1997). The activities under this programme include United Nations Development Programme (UNDP) support for the development and use of hybrid rice technology in India; the provision of consultancy and training assistance to countries such as Viet Nam and Myanmar; and the provision of support, through technical cooperation programmes (TCPs) to Bangladesh and the Philippines. IRRI and FAO in association with national agricultural research systems (NARS) also established an International Task Force on Hybrid Rice (INTAFOHR) with the objectives of:

• promoting the free exchange of registered germplasm, information and data from ongoing research and development (R&D) programmes on hybrid rice among interested partners;
• strengthening national systems' capabilities for applied and strategic research so that they can develop hybrid rice technology expeditiously;
• intensifying collaborative strategic research on hybrid rice by establishing effective regional and interregional collaboration on hybrid rice R&D;
• assisting member countries to formulate policy incentives for hybrid rice development and use;
• strengthening the hybrid seed industry and linkages between it and hybrid rice research centres.

PROGRESS IN HYBRID RICE DEVELOPMENT FOR THE TROPICS

Hybrid rice for the tropics was first developed in 1993. A set of tropical rice hybrids developed at IRRI was released in Viet Nam as UTL 1 and UTL 2 for the Mekong Delta (Luat et al., 1993). India released four rice hybrids - APHR-1, APHR-2, MGR-1 and KRH-1 - in 1994, and another hybrid, CNRH-3, for the boro season in West Bengal, in 1995. To date, as many as 12 public sector rice hybrids have been released for cultivation in different states of India (Table 3). Some private companies in India, most prominently Hybrid Rice International (HRI), PHI Biogen and MAHYCO, have also released additional rice hybrids developed by them for commercial cultivation (Table 4). The area coverage of hybrids is estimated to be close to 100 000 ha in India and a little more than 100 000 ha in Viet Nam. India and Viet Nam had targets of 2 million and 0.5 million ha, respectively, for 2000.

CONSTRAINTS AND CHALLENGES:

In the last two decades, great progress has been witnessed in the commercial exploitation of heterosis. Nevertheless, the technology is still being refined and the following constraints have been responsible for the slow pace of development and widespread adoption of the technology (Virmani, 1996):

• slow and inadequate investment in developing the technology;
• limited yield of heterosis in commercial hybrids;
• inadequate human resources, both qualitatively and quantitatively;
• lack of effective coordination among national agencies involved in hybrid rice research and development;
• lack of strong seed production infrastructure.

The success of hybrid rice development is largely determined by efforts to overcome the major constraints and the following developmental and technological issues are considered important (Tran and Nguyen, 1998):

• Developmental issues:
• policy support and full commitment;
• linkage and coordination among technology development centres, seed production agencies and extension agencies;
• capacity building to develop critical mass in hybrid rice breeding and seed production through training;
• partnership between public sector research and the domestic seed industry to share the bulk of hybrid seed production.
• Technological issues:
• development of superior-yielding hybrids with acceptable grain quality and adequate level of resistance to major insect pests and diseases;
• ensuring genetic purity of hybrid seed for stable expression of heterosis in rice hybrids;
• reducing the cost of hybrid seed.

For harnessing the full potential of heterosis, more innovative ways need to be adopted in hybrid rice breeding methods. Such methods could include replacing the unitary system of CMS with environmentally induced environmental genetic male sterility (EGMS) or genetically engineered male sterility systems; fixing heterosis through self-perpetuation of apomictic hybrids; and further enhancement of the magnitude of heterosis through generating interracial, interspecific and intergeneric hybrids. A phased strategy for the development of hybrid rice breeding outlined by Yuan (1998) includes:

• Breeding methodology:
• three-line method or currently used CMS system;
• two-line method or EGMS system;
• one-line method or apomixis system.
• Enhancing the degree of heterosis:
• intervarietal hybrids;
• intersubspecific hybrids;
• interspecific and intergenetic hybrids.

It is anticipated that each phase would lead to a breakthrough in hybrid rice breeding, contributing to step-by-step genetic enhancement of the yield of hybrids.

HYBRID RICE PROSPECTS FOR BANGLADESH

In considering the prospects for hybrid rice in Bangladesh, valuable lessons can be drawn from Chinese, Indian and Vietnamese experience. A review of the development and adoption of hybrid rice technology (HRT) in these countries reveals that China, which was the first to develop HRT, is now reaping the benefits by increasing rice production with a concomitant reduction in rice area. In tropical Asia, India and Viet Nam are successful in the development and cultivation of hybrid rice in farmers' fields. The lack of strong expression of heterosis among the early varieties grown as first crop in the double-cropped areas of Yangtse valley limited further extension of hybrid rice in China. India has selected rice hybrids for highly productive irrigated areas and favourable shallow lowlands. The hybrids released were of early medium duration, 125 to 135 days, and the hybrids developed are yet to have an impact in the high productive areas of northwest India and the river basins of peninsular India. Viet Nam has adopted, initially, IRRI-bred hybrids for the Mekong delta and has also introduced hybrids from China on a large scale for cultivation in northern areas of the country. In the Mekong delta of Viet Nam, most of the rice grown is direct-seeded and, as such, the spread of HRT may be difficult in this area.

Against the backdrop of these developments in China, India and Viet Nam, and in weighing the options for introducing or developing HRT for Bangladesh, it is important to understand the conditions under which hybrid rice would be profitable relative to inbred modern varieties (MVs) and also to make a realistic appraisal of the opportunities and constraints associated with developing and adopting HRT. The Chinese experience shows that there have been yield increases from hybrids in irrigated environments. However, in irrigated areas the high genetic potential of hybrid rice is likely to be appreciated only when the potential of semi-dwarf HYVs has been completely exhausted (Pingali, Mozris and Moya, 1996). In the rice production ecosystems of Bangladesh, adoption of semi-dwarf rice varieties was unsuccessful, and conventionally bred MVs are all of intermediate stature with growth duration ranging from 140 to 160 days. A serious issue to be considered is, therefore, an examination of the extent to which MVs' potential has been harnessed, especially in high-production environments such as during the boro season. There is concern that MV yields have been declining since their introduction in the early 1970s. Valid explanations for such apparent declines in yield could be the expansion of MV cultivation to less favourable and marginal areas where rice culture is under low input management, many biotic and abiotic factors, and lack of attention to the full utilization of the management package.

Hybrid rice technology has two major components - research and seed production. Hybrid seed production is not only technically complex but also labour-intensive and, hence, hybrid seed costs are very high. Labour wages, the availability of skilled labour, labour-land ratios and the extent of the irrigated rice area for adoption of hybrid rice are some of the factors that influence the cost of hybrid seed. In Bangladesh, the labour-land ratio is high, but irrigation is largely limited to the boro crop (Table 5).

Another important issue is the target environment and areas for adoption of hybrid rice technology. Targets for hybrid rice cultivation should be focused, not only by season, but also in locations (niches) of high productivity that are showing signs of yield plateaus. Furthermore, as the degree of heterosis expression is also influenced by the growth duration of parental lines, the development of heterotic hybrids of specific durations for targeted locations is needed. In Bangladesh, boro crop productivity is high relative to other crop seasons. There are prospects for growing early-maturing MVs as transplanted rice in the aman season with supplementary irrigation at critical stages of crop growth. Obviously, the first choice for adoption of HRT is in areas where irrigation is assured and the productivity of MVs is relatively high. It is important, therefore, to identify such areas in the thanas (subdistricts) for adoption of HRT in the first phase. The locations of compact block demonstrations, organized for maximizing yields under the Thana Cereal Technology Transfer and Identifications (TCTTI) project, should be the guiding factors in such areas for the implementation of hybrid rice programmes, with the expectation that the product used in the demonstration cannot be distributed for use as seeds, but that farmers should be motivated to buy their own hybrid rice seeds.

Proposed organizational structure for hybrid rice research and development for Bangladesh (National Network)

In such countries as India and Viet Nam it is clear that strong leadership and authority have provided the necessary impetus for the promotion of hybrid rice research and development. In Bangladesh, there is full support and encouragement of hybrid rice programmes from government policy-makers and senior functionaries. The Bangladesh Agricultural Research Council (BARC), the premier agency responsible for agricultural research and coordination of NARS, is fully committed to supporting hybrid rice research. The Bangladesh Agricultural Development Corporation (BADC), a public sector agency, has the necessary infrastructure for large-scale seed production. The Department of Agriculture Extension (DAE) is actively involved in the transfer of technology and has conducted a large number of demonstrations and on-farm trials of hybrids introduced from India and China. It is supported by an ongoing TCTTI project. The Bangladesh Rice Research Institute has the necessary expertise and commitment for hybrid rice research and development and can play an effective key role in technology generation and training provision.

The agencies responsible for technology generation, large-scale seed production and technology testing and transfer need to be brought into close functional linkage through well-defined time-bound activities accountable to a coordinating agency - the Hybrid Rice Task Force (HRTF) of the Ministry of Agriculture - which is headed by a senior functionary. A proposed organizational structure for a national hybrid rice research and development network for Bangladesh is shown in the Figure. In order to expedite HRT, the Government of Bangladesh has permitted the introduction and testing of selected rice hybrids developed by the private and public sectors in India and China. However, it is more important that the genetic superiority of hybrids over the best varieties be demonstrated unequivocally under identical conditions of crop management in high-production environments and locations before any exotic hybrid variety is imported for large-scale adoption in farmers' fields. Attempts must be made to produce F1 seeds in Bangladesh, but only when the variety has been proved to be superior.

REFERENCES

Fujimaki, H. & Matsuba, K. 1997. Characteristics of hybrid rice. In T. Matsuo, Y. Fustsuhara, F. Kikuchi and H. Yamaguchi, eds. Science of rice plant, Volume 3, Genetics. Tokyo, Japan, Food and Agriculture Policy Research Centre.

Lin, J.Y. & Pingali, P.L. 1994. An economic assessment of the potential for hybrid rice in tropical Asia: lessons from Chinese experience. In S.S. Virmani, ed. Hybrid rice technology - new developments and future prospects. Manila, the Philippines, IRRI.

Luat, N.V., Mui, H.T., Voc, P.C., Hung, V.M., Bong, B.B. & Virmani, S.S. 1993. Two promising IRRI rice hybrids named in Viet Nam. Intl. Rice Res. Newsletter, 18(2): 22.

Pingali, P.L., Mozris, M. & Moya, P. 1996. Prospects for hybrid rice in tropical Asia. In Proceedings of the 3rd International Symposium on Hybrid Rice, 14 to 16 Nov. Hyberabad, India.

Pingali, P.L., Hossain, M. & Gerpacio, R.V. 1997. Asian rice bowls: the returning crisis? Los Baños, the Philippines and Wallingford, UK, CAB International.

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 to 30 May 1997, Hanoi, Viet Nam.

Tran, D.V. & Nguyen, N.V. 1998. Global hybrid rice: progress issues and challenges. IRC Newsletter, 47: 16-27.

Virmani, S.S. 1996. Hybrid rice research and development in the tropics. In Proceedings of the 3rd International Symposium on Hybrid Rice, 14 to 16 Nov. Hyberabad, India.

Yuan, L.P. 1966. A preliminary report on male sterility in rice. Sci. Bull., 4: 32-34.

Yuan, L.P. 1998. Hybrid development and use: innovative approach and challenges. IRC Newsletter, 47: 7-15.

Riz hybride - évolution, problèmes et perspectives pour le Bangladesh

Au Bangladesh, le riz permet d'assurer la sécurité alimentaire et les moyens d'existence de la population. Actuellement, la production de céréales vivrières au Bangladesh s'élève à environ 20,3 millions de tonnes dont 18,04 millions de tonnes de riz. Avec le recul de la croissance de la production rizicole au fil des ans, la production de céréales vivrières est déjà déficitaire de 2 millions de tonnes et, pour équilibrer le budget de l'alimentation avec l'accroissement démographique, un taux de croissance d'au moins 2,5 pour cent de la production de riz est nécessaire. Hormis la Chine, les principaux pays producteurs, comme l'Inde et le Viet Nam, ont déjà entrepris de mettre au point et de cultiver du riz hybride à grande échelle. Cette technologie est donc très importante pour le Bangladesh où le nombre d'habitants est élevé, où il n'existe aucune possibilité d'expansion des terres arables et où le coût de la main-d'_uvre est encore raisonnable. Il est important évidemment d'en comprendre les avantages par rapport aux variétés modernes autofécondées pour pouvoir en évaluer de manière réaliste les possibilités et les limitations. Évidemment, c'est dans les régions irriguées où la productivité des variétés modernes a atteint un plateau (comme pour le riz boro) que l'adoption du riz hybride est tout indiquée.

Les pouvoirs publics ont autorisé l'introduction au Bangladesh de certains riz hybrides mis au point par les secteurs privé et public en Inde et en Chine, ainsi que les tests pertinents. Le Conseil de la recherche agricole du Bangladesh, qui est chargé de la recherche dans le pays, participe activement aux travaux en faveur du riz hybride. Le pays dispose d'institutions capables d'entreprendre la mise au point et le transfert du riz hybride. Il s'agit notamment de l'Institut de la recherche sur le riz du Bangladesh pour les technologies, de la Coopération pour le
développement agricole au Bangladesh aux fins de la production à grande échelle de semences, et du Département de la vulgarisation agricole pour le transfert de technologies. Dans des pays comme l'Inde et le Viet Nam, il est clair que des structures solides et un pouvoir fort ont fourni l'élan nécessaire à la promotion de la recherche et de la mise au point du riz hybride. Il est très important pour les programmes concernant le riz hybride de bénéficier d'une bonne organisation et du soutien inconditionnel et des encouragements des décideurs et des hauts fonctionnaires. À cet effet, il a été proposé de créer une structure pour la recherche nationale sur le riz hybride et le Réseau de développement au Bangladesh, pour assurer une coordination réelle des activités entre ces institutions, ainsi qu'entre celles-ci et les organisations non gouvernementales et les agriculteurs.

Arroz híbrido: avances, problemas y perspectivas para Bangladesh

El arroz proporciona seguridad alimentaria y de subsistencia a la población de Bangladesh.
El nivel actual de producción de cereales para alimentación humana en Bangladesh es de unos 20,3 millones de toneladas, de cuya cantidad el arroz por sí solo constituye 18,04 millones de toneladas. Al descender con los años el aumento de la producción de arroz, el país es deficiente ya en 2 millones de toneladas de cereales de consumo humano, y para equilibrar el presupuesto alimentario con una población que crece constantemente, se necesita una tasa de crecimiento de al menos un 2,5 por ciento en la producción de arroz. Los principales países arroceros fuera de China como la India y Viet Nam se han abierto ya paso en el desarrollo en gran escala de arroz híbrido y su cultivo. Por eso, dicha tecnología es muy importante para Bangladesh, donde hay una elevada población sin posibilidades de ampliar en el futuro las tierras de labranza y donde el costo de la mano de obra sigue siendo tolerable. Es importante que Bangladesh conozca las condiciones en que el arroz híbrido sería rentable frente a las variedades modernas endogámicas y se percate de las oportunidades y limitaciones que entrañan el desarrollo y la adopción de una tecnología de arroz híbrido. Desde luego, la primera opción que se ofrece para adoptar el arroz híbrido es que se lleve a cabo en zonas donde el riego esté asegurado y la productividad de variedades modernas alcance un cierto grado como el del cultivo de arroz boro.

Las autoridades de Bangladesh han permitido la introducción y ensayo de algunos híbridos selectos de arroz desarrollados por sectores privados y públicos tanto en la India como también en China. El Consejo de Investigaciones Agrícolas de Bangladesh, que es el que se ocupa de las investigaciones agrícolas del país, está plenamente comprometido en apoyar las investigaciones de arroces híbridos. El país cuenta con instituciones en condiciones de llevar a cabo el desarrollo de arroz híbrido y su transferencia. Entre ellas está el Instituto de Investigaciones Arroceras de Bangladesh para la generación de tecnología, la Compañía de Desarrollo Agrícola de Bangladesh para la producción de semillas en gran escala y el Departamento de Extensión Agrícola para la transferencia de tecnología. En países como India y Viet Nam es evidente que un fuerte liderazgo y autoridad imprimen el impulso necesario para promover las investigaciones y el desarrollo de arroz híbrido. Es sumamente importante que haya un fuerte liderazgo y un pleno apoyo y estímulo por parte de las autoridades políticas y el alto funcionariado a un programa de arroz híbrido. En ese sentido se propuso una estructura organizativa para una red nacional de investigación y desarrollo de arroz híbrido para Bangladesh con objeto de que se coordinen eficazmente las actividades que se llevan a cabo entre esas instituciones así como entre ellas y organizaciones no gubernamentales y el agricultor.