Yield improvement of rainfed lowland rice in drought-prone areas of Thailand and Laos

• Rice Research Institute, Thailand
• Department of Agriculture and Extension, Laos

Rice is a staple food in Thailand and Laos and a major export commodity in Thailand. Of the four rice culturesrainfed lowland, irrigated lowland, upland and deepwaterrainfed lowland rice occupies the largest area in both countries. However, because drought is common across northeastern and northern Thailand and in Laos, the yield of rainfed lowland ricedependent on rain quantity and distribution in the growing seasonis poor compared to that of an irrigated crop, and largely accounts for the variable rice production of these countries.

This ACIAR project will gather data to assess the value of a rice-breeding program to increase yield of rainfed lowland rice in drought-prone areas of Thailand and Laos. It will also identify strategies for increasing rice yields through genetic improvement.

The effect of drought on rainfed lowland rice will be studied, as well as the nature of the genotypic variation of drought-tolerant cultivars used in the northeast and northern regions of Thailand and the rainfed lowland rice-growing areas of Laos. In addition, the current method for screening drought-resistant cultivars at the Rice Research Institute of the Thai Department of Agriculture will be evaluated, and, if necessary, improved.

Complementary research will assist Australia's rice industry. In Australia, rice is grown under full irrigation, which is costly. However, recent research suggests that 30% less water is required by a new method of saturated soil culture. Here plants develop water stress in the early stages of growth, but recover to yield only slightly less grain than plants grown under full irrigation. The researchers will investigate genotypes that produce the best yields in the saturated soil culture system and evaluate promising cultivars.

The commissioned organisation, the University of Queensland (UQ), has a strong team of crop physiologists and plant breeders in the Department of Agriculture who are experienced in the improvement of drought tolerance in cereals including rice. The project will be an extension of the team's research activities.

In conjunction with their developing country collaborators, the UQ researchers will conduct experiments at different locations in Thailand and Laos and investigate the results using a simple simulation model with rainfall inputs from the past 30 years and pattern-analysis methodology developed at UQ. They will grow some 25 widely different genotypes (glutinous and non-glutinous types) under both rainfed lowland conditions and fully irrigated conditions.

About 10 genotypes from each experiment will be selected for drought tolerance and 5 for drought susceptibility. Then a number of methods to improve screening for drought tolerance will be examined at UQ by testing genotypes and measuring the heritability of important characters. Promising genotypes from these tests will be further evaluated in Thailand.

Australian scientists will visit Thailand and Laos regularly, but their overseas collaborators will work only in their own countries. The only exceptions may be post-graduate students awarded AIDAB or IDP scholarships to study at UQ.

To identify rice cultivars for water stress tolerance in Australia, the Australian team will develop a screening method and initially test a large number of cultivars and genotypes at UQ for suitability to saturated-soil culture.

By defining physiological criteria for improving the genotypic adaptation of cultivars to drought, the research program is expected to lead to a sound plant breeding program for rainfed lowland rice in drought-prone areas of Thailand and Laos. Eventually this should provide new, higher yielding cultivars that will stabilise yields from year to year and improve the welfare of subsistence farmers in the target regions.

Suitable cultivars may also be identified for the new method of rice culture in Australia, which would reduce the irrigation water required to grow a crop.