Progress in submergence, drought, and salinity tolerance in rice at IRRI
Channel: International Rice Research Institute
Date: 2009-09-15

Also see: http://irri.org/index.php?option=com_k2&view=item&id=9017:raising-productivity-in-rainfed-environments-attacking-the-roots-of-poverty-program-1&lang=en

IRRI scientists discuss recent progress on research to develop rice varieties that have tolerance to flooding, drought, and salinity.

Rainfed rice accounts for approximately half of the rice area of tropical Asia, where productivity is low and variable because of uncertain rainfall and infertile and toxic soils. This area is home to millions of the world's poorest farmers. Although the program has emphasized the vast rainfed areas of South and Southeast Asia, we have begun to engage with Africa, where about four-fifths of the total rice area is rainfed.

In rainfed lowland and upland environments, abiotic stresses are a major constraint, and most of the highly popular varieties are susceptible to these stresses. A major objective of the program is to develop improved tolerant varieties, along with complementary management practices and improved cropping systems.

This year's theme, from lab to field, reflects the broad range of activities in the program, extending from identifying and manipulating genes for stress tolerance to dissemination to farmers of the products of laboratory and field-based breeding. Exciting progress has been made on developing rice varieties with tolerance of drought, submergence, and salinity.

The submergence-tolerant Sub1 varieties, developed by marker-assisted backcrossing of the SUB1 gene into mega-varieties, are now undergoing intensive seed multiplication to meet heavy demand from farmers. Similar products for salt tolerance are nearing the testing phase. Quantitative trait loci (QTLs) conferring tolerance of drought are now being discovered, but varieties developed by standard breeding practices have performed well under drought. The drought-tolerant variety Sahbhagi dhan (R74371-70-1-1) was released in India following its promising performance in farmers' fields.

The work of program scientists has attracted significant funding from donors such as the Generation Challenge Program, the German government (BMZ), the International Fund for Agricultural Development, and the Japanese government. The large project Stress-Tolerant Rice for Poor Farmers in Africa and South Asia (STRASA), funded by the Bill & Melinda Gates Foundation, passed its first year and has made noteworthy progress. This project ties together stress-tolerance breeding with participatory varietal selection with farmers and seed dissemination and uptake. With strong support from national and regional governments, farmers' organizations, and nongovernment organizations, we have been able to take the best products to the farm. This represents a significant expansion of our collaboration beyond public research institutions to new partners.

Some additional highlights of the program research include the expansion of drought-screening activities, the identification of drought-tolerance QTLs in Asian mega-varieties, development of a decision support system for nutrient management of rainfed lowland rice, the identification of root-rotting fungus and nematodes as a cause of yield decline in aerobic rice, development of improved nursery and field management practices for submergence-prone and salt-affected conditions, new cultivars and cropping/aquaculture systems for salt-affected coastal areas, and the development of guidelines for integrated crop management that increased yields in the rainfed lowland conditions of Cambodia.

Even with more than three decades of intensive research on rainfed rice, most of the cultivars grown in rainfed lowland areas are high-yielding varieties developed for irrigated systems. This is expected to change soon, with stress-tolerant varieties becoming widely available to farmers in rainfed areas. These varieties, coupled with improved management methods, will extend the benefits of the Green Revolution to the farmers in these unfavorable environments.