Adaptation of low-chill temperate fruits to Australia, Thailand, Laos and Vietnam

• Research Institute of Fruit and Vegetables, Vietnam
• Plant Protection Research Institute, Vietnam
• National Agriculture and Forestry Research Institute, Laos
• Southern Fruit Research Institute, Vietnam
• Department of Agriculture, Thailand

This project extends previous research investigating the development of a sustainable temperate fruit industry in Thailand. Temperate fruit industries in Thailand are in the early stages of development, but high prices are paid for temperate fruits in Thai domestic markets. The production of high-value temperate fruits would raise living standards of hill tribe people and encourage them to use sustainable cropping systems. There is also an export market window into other Asian countries from March to May.

Vietnam already grows many fruit crops and the average revenue from fruit production is two to three times higher than that of rice. It is estimated that many more areas are suitable for temperate fruit production. Laos only grows poor-quality local varieties but has other suitable areas to grow low-chill temperate fruit. The problems for growing temperate fruits in Vietnam and Laos are similar to those that have been identified in Thailand: development of insect pests and diseases during high humidity, lack of knowledge on how to select the best varieties and manage the crops, lack of nurseries, and lack of marketing studies or plans.

The project aims to establish and develop sustainable low-chill temperate fruit industries (stone, pomegranate fruit and persimmon) in Thailand, Laos and Vietnam through the identification of appropriate sites and varieties and through the implementation of best management practices at the farm level.

The researchers continued the evaluation of suitable varieties of stone fruit, pome fruit and persimmon for Thailand and Australia, and established experimental sites to start evaluating these fruits in Laos and Vietnam. They also collected suitable low-chill fruit varieties in Laos and Vietnam and incorporated superior qualities into collections.
The team finalised orchard management studies in Thailand and Australia on the use of rest-breaking chemicals and growth-control techniques in regions that lack sufficient chilling, and incorporated the results into a decision support manual. They also set up similar orchard studies in Laos and Vietnam.
The team completed a decision support system for growers and training extension agents in Thailand. They set up demonstration blocks, developed manuals and ran training workshops in Thailand, Laos and Vietnam to train selected growers. Finally, they completed plans for marketing produce into domestic and export markets.

Over 1300 stonefruit trees of 25 varieties of peach, plum, nectarine, persimmon have been sent to Vietnam and Laos. This is in addition to the 2000 trees sent to Thailand in the previous ACIAR project PN 94/947. About 70% of the trees sent to Lao and Vietnam have survived field-planting (at two arboreta sites in Lao and four arboreta sites in Vietnam). These sites have a wide range of chilling;

Vietnam
Moc Chau 150 chill units
Bac Ha (350 chill units)
Sapa (700 chill units)
Dalat (100 chill units)

Laos
Nonghet (300 chill units)
Ponsavan (150 chill units)

In addition to growing low-chill temperate fruits, the scientists have identified that Vietnam can also grow high quality medium-chill cultivars of stonefruit. They observed that high quality medium-chill plum cultivars Black Amber, Simca and Fortune are performing well at Sapa. Under good management systems these varieties should produce late-season fruit in July and will complement the early-season production (March-May) from the lower-chill regions.

Non-astringent persimmon has been identified as a potential new commercial crop for Vietnam, Laos and Thailand. Better-adapted rootstocks have been identified in Vietnam. These appear better suited to the red ferralitic soils than the commonly used Australian rootstocks, which have failed to establish quickly in Thailand on similar soil types. The cv. Fuyu has been identified as the best variety for commercial production.

Important temperate fruit germplasm has been identified in Laos and Vietnam. Many local selections have resistance or tolerance to some of the major leaf diseases. Germplasm of two selections has been imported in Australia and will be incorporated into the low-chill peach-breeding program.

A range of plum and nectarine varieties was identified as having tolerance to drought. These varieties were better adapted to low-input systems found in these countries.

New orchard management technologies Key management practises for growing temperate fruits in Thailand, Laos and Vietnam have now been developed.

A complete management decision package has been developed for growing temperate fruits (persimmon and stonefruit) under subtropical environments of Australia and Asia. User-friendly, basic and advanced manuals have been written for both the farmer and for the extension officers to assist in the transfer of new technologies. These manuals summarise over 20 years of research and development into these fruits.

Low-input technologies for growing stonefruit and persimmon have been developed for Thailand, Laos and Vietnam. These include:
deficit irrigation
mulching
new orchard hygiene systems eg spot spraying
new tree training and management systems eg post-harvest topping
use of exclusion netting and fruit bagging to eliminate fruit fly.

Low-chill stonefruits, when grown under subtropical environments, often make excessive vegetative growth, and this reduces yield and fruit quality. Fruit size can be increased by as much as 30% where shoot extension growth is restricted to <10 cm at stone hardening. Studies showed that a new growth retardant prohexadione - Ca (Regalis) - is highly effective in restricting growth and improving fruit quality. It overcomes the disadvantage of soil-applied growth retardants such as paclobutrazol, which are not effective on some soil types and can result in residue build up. Studies also showed that control of shoot extension growth and improved tree nutrition (in particularly nitrogen) could significantly increase the level of crop loading.

New systems for training the trees have been trialled in Thailand and Australia. In Australia the open Tatura trellis system is giving exceptionally high yield and fruit quality. In Thailand, the palmette and pillar systems produce high quality fruit and the trees are easy to manage. The ethylene inhibitor, AVG, was highly effective in increasing fruit firmness and sugar concentrations. The chemical must be applied within 1 week of first harvest. Further research is needed to develop `super sweet' fruit using new varieties, exclusion netting, open Tatura trellising system, growth retardants and ethylene inhibitors.

In Thailand, Laos and Vietnam, soil moisture stress during the early stages of the fruit development period appears to significantly restrict growth and, provided the level of stress is not too great, can have a similar effect to using growth retardants. However, excessive stress can reduce fruit size. In Thailand, exclusion netting appears to have reduced water usage, leading to improved tree health particularly under drought conditions experienced in 2004.

New pest and disease control strategies The major pests and diseases identified are similar to those found in Australia. Senior research and extension staffs in the collaborating agencies in Thailand, Laos and Vietnam have been trained to identify the most serious pest and disease problems and to undertake appropriate control programs.

Exclusion netting proved to be highly effective in eliminating fruit fly and a wide range of other pests form the orchard. It also had the additional benefit of improving sugar concentrations of the fruit by as much as 40%, presumably due to the higher heat units accumulated under the netting and better partitioning of carbohydrates to the fruit. In Thailand and Vietnam, bait programs were highly successful in controlling the most serious pest, fruit fly.

Commercialisation and economic performance Commercialisation of temperate fruit production in Thailand is progressing. The peach cv. Tropic Beauty has performed well and is being commercially produced by hill tribe villagers near Ang Kang and Khun Wang. Recently established cool storage facilities in Ang Kang and the use of refrigerated trucks to transport the fruit to the larger cities of Chiang Mai and Bangkok has ensured that high quality fruit is reaching the consumer. Agro-tourism is also being successfully developed in these regions with temperate fruits being a major tourist attraction. Vietnam is aiming to double its temperate fruit production area to 10,000 hectares within the next 5-10 years.

The second extension of the project demonstrated that with new varieties and management systems that high returns can be achieved from temperate fruits in warm subtropical regions of Asia. Varieties introduced from Australia as part of the ACIAR project are receiving double the price of locally produced varieties, because of their higher quality. For example, in Lao PDR, farmers achieved incomes of about $A6000-8000 per hectare from low-chill peach and nectarine production - about 20-30 times greater than their usual annual income of $A300 from growing upland rice and corn.

At Ang Kang in northern Thailand, trees of peach cv. Tropic Beauty produced 120-150 fruit per tree with an estimated yield of 8-10 tonnes per hectare. Fruit quality was excellent with average fruit weights of 150 g and high sugar content. Using an average price of 80 baht per kg, we demonstrated that farmers could achieve gross returns of $A25,000 per hectare even in very steep, marginal country.

In Lao PDR, the project successfully extended temperate fruit production systems to four new districts in Xiengkhouang Province and the nearby province of Huaphan. A small nursery, near the Regional Agricultural Office in Ponsavan, has been established to propagate temperate fruit and other subtropical fruit species. Due to the success of the project, the Lao Ministry of Agriculture is now actively promoting temperate fruit production in cooler regions of the country.

In Thailand, the Thai DOA has established stonefruit demonstration orchards at 20 farmer sites in Khun Wang, Ang Kang and Chiang Rai Provinces. Tree age varies from 3 to 5 years of age. Older trees have commenced cropping. Peach cv. Tropic Beauty has produced high quality fruit. For example, one farmer has achieved yields on 4-year-old peach trees of about 120 fruit (18-20 kg per tree). Because the quality of fruit was high, with about 30% of the fruit extra grade, this farmer received on average 80 baht/kg ($A3 per kg).

Although the temperate fruit growing regions of both Thailand and Lao PDR have a plentiful supply of water, which is held in small dams, farmers lack expertise and funding in designing and installing suitable irrigation systems. In Lao PDR, the project successfully installed a minisprinkler irrigation system, the first of its type in this country, at one commercial farmer's orchard.

Extension, farmer training and communication channels
At the commencement of the project extension, an extension methodology workshop was held in Chiang Mai Thailand to examine ways of improving delivery of temperate fruit methodologies to farmers. As a consequence, an improved understanding on the best extension methodologies was developed. Excellent communication links have now been established between Australian, Thai and Lao researcher and extension officers.

Marketing In Thailand, sensory evaluation studies were conducted at both Royal Ang Kang and Khun Wang Research Stations. Analyses showed that four of the newly introduced stonefruit varieties are well accepted by Thai consumers. Other studies showed that both Thai and Lao PDR consumers prefer large, highly coloured fruit with high sugar concentrations and low acid.