Soybean variety adaptation and improvement in Vietnam and Australia

• Vietnam Agricultural Science Institute, Vietnam
• Institute of Agricultural Sciences of South Vietnam, Vietnam
• Thai Nguyen University, Vietnam
• James Cook University, Australia
• CSIRO Plant Industry, Australia
• Hanoi Agricultural University, Vietnam
• Hanoi Agricultural University, Vietnam

Productivity of soybeans in Asia, and particularly Vietnam, is low compared with elsewhere in the world. Vietnam's average yields are 1t/ha compared with 1.3 t/ha in Thailand, 1.75 t/ha in Brazil and 2.25 t/ha in the USA. This low productivity is a problem because Vietnam needs more soybeans to satisfy a growing demand for stockfeed and to improve the nutrition of the human population.
The reasons for poor production in Vietnam have been clearly identified. One of the most significant is the fact that the varieties grown in summer have a growing period too short to produce the maximum yield possible for the season. The high seasonal rainfall usually occurs when crops are maturing and this causes poor seed quality. In addition, these poorly-adapted varieties are grown at low densities to reduce the problem of lodging (plants falling or bending and becoming tangled).
Moreover, soybean is invariably treated as secondary to rice, and so receives less research attention, less fertiliser input, and less effort at insect control. This is made worse by the existing poor yields. It simply does not appear worthwhile to invest in a crop that gives poor financial returns. For this reason, soybean is grown using natural rainfall, and short-duration varieties that make use of this are chosen. These varieties naturally have a low yield potential. Higher-yielding varieties, better suited to the conditions in the growing areas of Vietnam, were seen as one of the main ways of solving this problem. At the same time, superior varieties and greater knowledge would benefit the small soybean-growing operation in Australia and expand the experience of the Australian project team gained in an earlier soybean improvement project in Thailand.

The project aimed to enhance the yield and quality of soybeans in Vietnam and Australia by developing suitable cultivars for immediate use by growers, along with improved agronomic management methods.

The project gained access to germplasm with desirable traits such as tolerance to extreme temperatures and to acid soils, from breeders around the world. Following evaluation and study in Australia, the best lines were introduced into Vietnam. Varieties previously evaluated in Thailand - and found to be well-adapted to the Asian tropics - along with other varieties already developed in Australia were also taken to Vietnam.
In Vietnam, the team evaluated selected traits - in particular, those useful for growth of the winter crop in northern Vietnam. Then, the scientists introduced desirable traits into existing lines through hybridisation. Lines with potential for cultivar development were evaluated in both Vietnam and Australia, covering a range of growing conditions, locations and seasons.
Promising lines were used for farm demonstration trials that would encourage acceptance and adoption of the new cultivars. These trials also produced seed for cultivar release
At the same time, the project team studied current agronomic regimes to discover what needed changing in order to accommodate the requirements for the new cultivars. A series of replicated field trials was conducted.

This project connected CSIRO Tropical Agriculture/Plant Industry and James Cook University in Australia formally with the Vietnam Agricultural Sciences Institute, the Institute of Agricultural Science, Thai Nguyen University of Agriculture and Forestry, also informally with the Hanoi #2 Agricultural University, the Oil Plant Institute and Can Tho University in Vietnam.

The thrust in Vietnam was to improve varieties and production methods for summer soybean production in the northern hill and mountain regionsthe source of more than 40% of national production in the Red River Delta (which produces about 20% of the crop, mostly in winter) and in the upland regions of southern Vietnam (which produces about 20%).

There were several key elements to the project. The first was to introduce and evaluate elite varieties from the Australian program for yield and adaptation in Vietnam. Concurrently, physiological and agronomic research was undertaken to explore and where possible to minimise limitations to improving adaptation and increasing yield in Vietnam. The research in Australia complemented that in Vietnam, with applied varietal improvement emphasis on tropical adaptation, tolerance to weathering and food quality attributes. Basic research focused on strategies to broaden the gene pool, especially for tolerance to environmental stresses and use of the 'long juvenile' trait to extend duration without increasing photoperiod sensitivity.

The use of extreme-short duration varieties was confirmed as a key limitation to yield in the north of Vietnam. Hitherto, short duration has been necessary to achieve the low day-length sensitivity necessary for one variety to be adapted to the spring, summer and winter cropping seasons. The requirement for one variety to be reasonably adapted to all three cropping seasons was in turn necessary to ensure supplies of fresh planting seed, because of the short time that soybean seed remains viable under local conditions.

During the project, varieties were introduced to Vietnam with medium duration, but with appropriate day-length sensitivity that enabled successful cropping in all three seasons. The combination of varieties with high yield potential and medium duration led to increases in yield over that of check varieties of up to 98, 34 and 49% in the spring, summer and winter seasons, respectively. As a result of these findings, it is likely that one or more lines introduced through the project will be released for commercial production in Vietnam.

The saturated soil culture technique for irrigation of soybean and intercropping soybean with paddy rice was also introduced and tested in the lowland conditions of the Red River Delta. Yield increased by up to 250 per cent through the combination of this technology with introduced varieties with higher yield potential.

The research in Australia identified and introduced to the breeding program new sources of tolerances to cold, drought and pre-harvest weathering of grain. In a linkage with the national breeding program in Australia, a new tropical variety, YY, was released for commercial production. New technologies to identify genes responsible for drought response and for culinary quality were also developed. For the first time, genetic material from the wild perennial relatives was introduced into soybean through somatic hybridisation.

Key outputs from the project have therefore been improved varieties and agronomic management, enhanced understanding of constraints to wider adaptation and higher yields, and new techniques for enhancing the germplasm base available to breeders. In addition to the direct benefits from the project to both the Vietnamese and Australian researchers, the skills base of the Vietnamese researchers was improved through four short-term visits and one long-term training visit to Australia, and the training of several postgraduate research students in Vietnamese universities. In addition, the project facilitated applications that appear likely to enable two project staff to come to Australia and one to the USA for higher degree studies.