A DURIAN INDUSTRY IN AUSTRALIA
SCIENTIFIC NAME: Durio zibethinus
FAMILY: Bombacaceae
ABSTRACT
The market for fresh durian in Australia is very receptive due to current quarantine regulations preventing fruit importation except in frozen, dried or processed form.
The limitations to a potential industry at present are the unknown factors of economics, particularly the price x yield relationship; incomplete screening of suitable productive and quality cultivars for northern Australian conditions and a relatively long lead in period to production after screening and recommendation. Also, pest problems are likely to be significant.
The natural production period in north Queensland is October to April, with a peak in January/February. However, the crop is very responsive to paclobutrazol and production periods can be shifted to some extent, giving at least 6 months cropping and with less of a peak.
INTRODUCTION
The development of a successful durian industry in Australia is dependent on a number of factors:
• Satisfactory production of quality fruit, preferably over at least 5 months of the year.
• Satisfactory production x price relationship.
• Development of' packaging concepts to allow transport and marketing of the product without general public objection to odour.
• The continuation of quarantine embargo preventing or restricting importation of fresh unfrozen fruit.
INDUSTRY STATUS AND MARKET POTENTIAL
Planting of durian has occurred on a number of properties in north Queensland on the coastal strip from Tully to Bloomfield River. Committed (in excess of 0.4 ha.) growers number only three, although another 12 to 15 growers of miscellaneous tropical fruit also have small plantings. Total area is estimated at 7 ha. Northern Territory plantings in the Darwin area are also small, but increasing. Considering the unknown factors in production and, unknown economic viability of operations, slow development of the industry is probably appropriate.
Present market opportunity is mainly with the ethnic Asian population ex Malaysia, Indonesia, Thailand, Laos, Vietnam, Philippines and Hong Kong. There is also, however, a significant ethnic European population with a taste for the fruit. Total market volume size is difficult to estimate, particularly since frozen fruit import information is not accessible from Commonwealth statistics.
However there is undoubtedly a market to absorb production from at least 100 hectares. The frozen product is regarded as satisfactory but purists in the market place prefer fresh fruit. A considerable amount of the frozen product is presently converted to an ice cream flavouring, carried out in the purchasers' homes.
Thailand is the main source of imported frozen aril sections and whole frozen fruit at present. That country's industry has expanded greatly in the past 20 years. Annual production was circa 469,000 tonnes in 1975 and now probably surpasses 550,000 tonnes.
Export market potential is difficult to postulate, particularly in view of good domestic prices in Australia and the requirement for quality in Asian and other markets. The possible off season advantage Australia may have been negated by future developments in Indonesia (which has a similar season to us) and, the use of growth regulators in spreading production season in Thailand, Malaysia, etc.
CULTIVAR INTRODUCTIONS
The essence of success in durian production and marketing in Australia lies in the combination of tree productivity and fruit quality. Imported frozen products are generally of high quality - cultivars Mon Tong, Gaan Yaow, Chanee, etc. are picked and processed at optimum time for quality freezing.
The introduction of a comprehensive range of good cultivars has been a slow process due to difficulty of access (Thai embargo on release of material), problems with establishment in quarantine, and little subjective data on production and quality characteristics of the Asian gene pool. Further, some cultivars introduced (eg. D16, D123 and Sitebel) are obviously not true to name.
The following list denotes successful importations listed under country of origin - which is not necessarily the country imported from. Those incorrectly named are included.
| Thailand | Malaysia | Indonesia | Philippines |
| Mon Tong | D2 | Cipaku | Sitebel |
| Chanee | D7 | Parung | |
| Chompoo See | D24 | Sunan | |
| Gaan Yaow | D16 | Hepe | Singapore |
| KK8 (Kradoom Tong) | D96 | Petruk | |
| Gob Yaow | D98 | Jurong | |
| Luang | D102 | ||
| D123 | |||
| Hew 3 | |||
More recent introductions which may be successful are Hew 1, 2, 4, 5, 7 and 8, D6 and D20.
TEMPERATURE LIMITATIONS
Of major interest is the effect low temperature is likely to have on production. At Kamerunga Research Station, minimum temperatures in the range of 7.2 to 9.0°C in June and July have resulted in some leaf fall but not total defoliation. However, in at least one other location with temperatures down to 6°C there has not been a massive defoliation on vigorous young trees. Leaf fall may be largely dependent on tree vigour (general health) and thus absolute effects at low temperatures are difficult to predict. Some plantings of very young trees recently established and with relatively poor growth have been known to die following temperatures down to 4 and 5°C. At this stage commercial production is not recommended in areas with any records of temperatures below 5°C.
In common with our experience with rambutan, there is a surprising diversity in reaction to low temperatures within the gene pool. North Queensland has not experienced extremely low temperatures since 1984 and thus many cultivars have not been tested. However of the group Chanee, Mon Tong, Sitebel, D96, D16, and Chompoo See, the latter proved most susceptible to leaf fall in the 7 to 10°C temperature range.
The critical factor is whether leaf fall reduces production in the following summer, or causes flower and fruit drop from trees induced to flower in the April/June period.
FLOWERING AND FRUITING PERIODS
Flower bud formation occurs some 2 to 8 months before inflorescence development. Inflorescence growth takes approximately 2 months up to flower opening, but longer if in cool periods of the year. In north Queensland some flowering occurs as early as July, but predominantly in September-December and usually peaking in November for the bulk of cultivars. The period of anthesis to fruit maturity (fall) in summer is recorded with cultivars from 130 to 150 days (Mon Tong) 115 to 140 days (Chompoo See) and 120 to 135 days (Chanee). There is considerable spread in the development period of fruit on any one tree under our conditions. This may possibly be conditioned by the crop load - usually the greater number of fruit, the smaller the average size of the fruit, but there is considerable variation. There is as yet insufficient data taken to date to relate to development period in respect to fruit size.
PRECOCITY
The Thais describe a roughly linear relationship between years to first bearing and the development period (anthesis to maturity) of fruit (1).
| Early cultivars - | 4 to 5 years to bearing and 95-105 days fruit development e.g. Luang, Chanee, Kradoom, Chompoo See. |
| Medium cultivars - | 5 to 6 years and 105 to 120 days fruit development e.g. Gaan Yaow, Mon Tong, Kob, etc. |
| Late cultivars - | more than 6 years to bearing and 120 days plus fruit development e.g. E-Nak, Gumpun, Kob Lebyiew, etc. |
At Kamerunga, first harvest was Chompoo See and Hew 3 - year 6, Chanee - year 7, and Mon Tong - year 8. Earlier yields may possibly be achieved if trees are very well-grown. Some other cultivars' precocity date has been compromised by paclobutrazol studies (described later).
In general, durians flower the year previous to achieving a crop but invariably any fruit set usually abort at up to 75 mm length.
POLLINATION
Durians are usually regarded as requiring cultivar outcrossing to achieve pollination and fruit development. However the Thais may have unintentionally selected for a higher degree of self-compatibility. Prabhadhapongsee (pers. comm.) maintains that planting a number of cultivars in one block is not necessary for achieving good yields in Thailand. However the author observed few, if any, plantings which were not blocks of mixed cultivars there. Flower opening occurs in the late afternoon and the stigma is receptive after 5.00 p.m. (2). However the stigma is obviously receptive for at least 24 hours before that time, and at Kamerunga we have successfully pollinated flowers up to 2 days before normal flower opening.
Anther dehiscence does not occur until 7 p.m. but varies considerably with cultivars in a 1- 3 hour time span at Kamerunga, with Chanee being the latest. By about 11 p.m. the anther lobes fall off.
A standard technique developed at Kamerunga to avoid hand pollination at night is to take flowers at between 4.00 and 6.00 p.m. and stand in water overnight. The following morning, flowers due to open the same day (evening) are pollinated. Best effective pollination has come from outcrossing cultivars, and selfing is not recommended.
A comparison of hand pollination at -2, -1 days before anthesis (approximately 32 and 8 hours previous) and +1 after anthesis (approximately 12 hours after) is shown from Kamerunga work in Table 1.
TABLE 1.
HAND POLLINATION
KAMERUNGA HORTICULTURAL RESEARCH STATION October/November 1987
| No. of pollinations Successful * | |||||
| Pollinated cv. | -2 | -1 | +1 | -1 | +1 |
| Hew 3+ | 3 | 9 | 15 | 1 | |
| Montong | 1 | 10 | 10 | 1 | 1 |
| Chompoo See | 2 | 16 | 15 | 5 | 3 |
| Chanee | 32 | 19 | 8 | 3 | |
| * = fruit harvested | |||||
| + = Hew 3 in first flowering | |||||
A number of pollinator cultivars were used including Chanee, Mon Tong, Chompoo See, D16, Hew 3 and D123. All were successful in producing at least one fruit, but Chompoo See appeared most successful.
Overall observations on time of year for successful pollination indicate preferred periods from October to May. Hand or natural pollination between July and August appears generally unrewarding, and it is not known if this is due to lower temperatures and humidity or other factors. Hand pollination is not required to achieve satisfactory crops from October to May anthesis at Kamerunga, and in fact hand pollination trials are restricted to the lower 2 to 3 metres of trees. There has been adequate set above this height. Pollinating bats have been observed through evidence of flower damage, but it is not determined whether either of or both the Queensland blossom bat, Syconyeteris australia, and the northern blossom bat, Macroglossus minimus, are probably involved. Richards (pers. comm.) states that the Queensland blossom bat is more numerous (by 10 to 1) in the area.
FRUIT CHARACTERISTICS
Suitable fruit quality characteristics are all important to the Asian consumer (4). Generally Thais prefer a deep yellow aril flesh, high aril recovery, small seed size and dryish texture. The most highly priced cultivar, Mon Tong, has all these characteristics. Malaysians on the other hand, appear not so concerned about dryish texture, possibly the result of a lesser degree of sophistication and a shorter time period of active cultivar selection and assexual propagation.
Fruit characteristics from Kamerunga are shown in Table 2.
TABLE 2.
FRUIT CHARACTERISTICS - DURIAN CULTIVARS - K.H.R.S. 1987/88 SEASON
| Cultivar | Mean Fruit Weight | Mean Pericarp % Weight | Mean Seed % Weight | Mean Aril % Weight | Mean Full Locule No. + | Aril Colour # | Aril Texture |
| Chanee | 1.95 | 61.2 | 9.3 | 29.5 | 3.9 | pale yellow | mod. firm |
| Chompoo See | 1.30 * | 51.2 | 14.5 | 34.3 | 3.3 | yellow | soft |
| Mon Tong | 2.36 | 58.9 | 4.5 | 36.6 | 4.2 | deep yellow | v. firm |
| Hew 3 | 1.00 | 57.0 | 14.1 | 28.9 | 4.0 | yellow | firm |
| D16 | 0.53 * | 78.6 | 9.7 | 11.1 | 1.9 | pale yellow | firm |
| D98 | 3.30 | 58.5 | 9.5 | 32.0 | 5.0 | yellow | firm |
| D123 | 1.02 | 77.7 | 9.8 | 12.5 | 2.3 | pale yellow | firm |
| Cipaku | 1.10 | 61.9 | 11.5 | 16.6 | 3.0 | yellow | soft |
| Sitebel | 2.10 | 73.1 | 8.8 | 18.1 | 3.0 | pale yellow | soft |
| + Number of locules with aril (perfect fruit has 5 full locules) | |||||||
| * Fruit size smaller and fruit number greater than usual due to flower induction with paclobutrazol. | |||||||
| # When fruit picked or fall fully mature. | |||||||
Aril recovery from D16, D123, Cipaku and Sitebel was judged unacceptable for commercial cultivars.
Total fruit number and weight per tree in the 1987/88 season is shown in Table 3.
TABLE 3.
TREE YIELDS, SELECTED CULTIVARS, KAMERUNGA 1987/88 SEASON
| Cultivar | Tree No. | Tree Age | Number of Fruit | Mean Fruit Weight (kg) | Total Yield (kg) |
| Chanee | 113 | 9 | 42 | 1.77 | 74.4 |
| Chanee | 103 | 9 | 43 | 2.07 | 89.1 |
| Chompoo See | 106 * | 8 | 94 | 1.45 | 136.0 |
| Chompoo See | 104 | 8 | 50 | 1.09 | 54.7 |
| Mon Tong | 115 | 8 | 20 | 2.36 | 47.2 |
| D16 | 109 * | 6 | 156 | 0.42 | 65.5 |
| D16 | 108 * | 6 | 31 | 0.5 | 18.4 |
| * = Paclobutrazol treated. | |||||
Individual fruit weights ranged up to 3.9 kg each for Chompoo See, Chanee and Mon Tong but in previous years, maximum weight has been 4.2, 6.3 and 6.2 kg respectively. Fruit size/weight is correlated inversely to fruit numbers.
PESTS AND DISEASES
No Phytophthora species (P. cinnamoni or P. palmivora) have been isolated from Kamerunga trees, although tree decline with some cultivars (particularly D2 and D24) has been associated with Macrophomina phaseoli and Botryodiplodia theobromae. Phosphorous acid and potassium hydroxide injections have (10% each) brought back to health all trees treated for decline. Bark splitting coupled with gum excretion, followed by healing without treatment, is fairly common on branches of Chanee cultivar.
Fruit rots on the base of Chanee fruit, in particular, is evident in wet periods and may be associated with insect damage. However no primary pathogen has yet been isolated. Of the three major cultivars, Mon Tong is least susceptible.
The fruit spotting bug, Amblypelta lutescens, is the most important insect pest, feeding off flowers, young developing fruit and fruit right up to maturity. It may well be responsible for initiation of fruit rots. Thrips and mites are evident on very young developing fruit in hot dry periods. Rhyparida beetles are a significant problem on foliage of young trees, but after 3 to 4 years of age percentage damage decreases.
POST HARVEST HANDLING
Studies in post-harvest handling will have the greatest significance in any potential durian production in Australia.
The Thai system of harvest is to pick fruit which are physiologically mature and will ripen with satisfactory aril colour, but not ripen too quickly. Judging fruit to be in this condition is more an art than a science; however, obviously factors such as records from previous years, records on time of peak fruit set as well as fruit appearance are taken into account. Mon Tong cultivar has good latitude in harvest in that even fruit picked 10 days before normal drop will develop satisfactory deep yellow aril colour and are unlikely to be sour.
Chanee and Chompoo See, however, require to be picked within 4 to 5 days of fruit drop in order to develop satisfactory aril colour and sweetness. Additionally, Mon Tong will carry without odour if picked outside 2 days before normal drop, but there is less latitude with Chanee and Chompoo See. A trial conducted at Kamerunga on Chompoo See cultivar in January 1987 compared three maturity grade judgements based on fruit appearance and very subtle pericarp colour changes. Fruit were picked then sorted and allowed to ripen. Maturity grades were M1 (least mature) M2 and M3 (most mature). On opening, fruit aril colour was judged Y3 (best yellow development, Y2 and Y1 (palest colour). Results are shown in Table 4.
TABLE 4.
FRUIT MATURITY JUDGEMENT K.H.R.S.
Chompoo See cv.
GRADING AND NUMBER OF FRUIT
| Y3 | Y2 | Y1 | |
| M3 | 7 | 1 | 1 |
| M2 | 4 | 4 | 1 |
| M1 | - | 4 | 5 |
The results indicate a fair appreciation of maturity based on fruit appearance, even when carried out by unskilled staff.
The trial also incorporated ethylene and Ethrel ripening. In general, both ethylene and Ethrel advanced ripening of fruit significantly, but did not influence aril colour development.
In Indonesia and Malaysia, fruit are traditionally allowed to fall and then marketed. This gives high sugar levels for customers, but the fruit has a very short shelf life of only 1 to 3 days at ambient temperatures before spoiling.
In Australia, obviously, only fruit without odour will be allowed to be transported by conventional means and this will require expertise on maturity status by growers. The situation leans heavily to choosing cultivars with the characteristics of Mon Tong if whole fruit marketing is to be entertained.
The alternative system is to allow fruit to drop, then cool to firm up the aril before dissecting. Aril segments can then be taken out, punnet-packed and film-wrapped. D.P.I. trials to date indicate an acceptable 3 to 4 weeks shelf Iife for fresh aril segments in the temperature range of 5 to 15°C. Temperatures down to 2°C may even be acceptable. Moisture loss from fruit is very significant if not film-wrapped. Transport of chilled ripe aril segments still presents a transport problem, which may possibly only be overcome by special containers, or, production on such scale that bulk rail containers can be utilized on their own. Wholesale and retail outlets will also have problems to solve in relation to 'pollution control'. Freezing of arils, whole fruit and ice cream manufacture is perhaps the other alternative, but would have to compete with imported products. Aril segments can be kept in excellent condition up to 3 months by quick freezing and maintenance at minus 24°C without changes in flavour, although not in texture (3).
TREE MANIPULATION
Phenological cycling in durian is not understood, particularly in relation to the interaction between vegetative growth and flower bud initiation. In West Malaysia, generally 2 crops are carried each year, one in July and the other in December, with the latter usually, but not always, the smallest. Recent evidence (Chan Ying Kwok pers. comm.) indicates a high level of nitrogen assimilation in periods other than directly after harvest, leads to smaller and less frequent flowerings.
In Australia and Thailand, generally one crop is produced each year following a spring/early summer flowering. Until recently, spread of cropping has been achieved by cultivar range, giving up to 5 months in Thailand from early season flowering and short fruit development period of Kradoom Tong, through to late season flowering and long fruit development period of E-Nak, etc.
K.H.R.S. trees were collar-drenched with paclobutrazol in early February 1987 at rates of approximately 3 ml a.c. per 100 cm2 of trunk cross-sectional area. Flower bud initials were apparent in April, and flower opening commenced in May, running into late June.
Fruit harvest commenced in early October 1987, some 2 to 3 months prior to the start of the normal season. Paclobutpazol rates applied were far in excess of requirements, and may be more appropriate at 1 to 2 ml a.c. per 100 cm2 of trunk cross-sectional area. A number of trees expressed extreme nodal shortening and are still not flushing normally some 16 months after application.
Durian is obviously very sensitive to paclobutrazol, and its effects are both an immediate flower inductant and vegetative growth modifier. A Chompoo See Tree (106) treated In February produced a good crop the following October and then immediately flowered again to produce a normal crop in January-February 1988. Total yield was 94 fruit for 136 kg. Management of paclobutrazol* treatment will require developing an understanding of the tree's capacity to bear without inducing decline in tree health. It may well be, however, that the trees' capacity to bear is much greater than that achieved through normal growth patterns.
FUTURE WORK
Areas of concern or potential are seen as:
• Further importation and screening of quality cultivars.
• Developing an understanding of the tree's phenological cycling and the influence of fertilizer timing on carbohydrate status, flower development and yield.
• Pollination inhibition in 'cool' months.
• Management of paclobutrazol concentration and timing and long term yield effects.
• Study of fruit spotting bug, mite and thrip activity.
• Study of fruit rots, tree and trunk borers.
• Development of maturity parameters.
• Development of 'odour barrier' packaging.
• Development of fresh aril packaging, marketing and consumer feedback.
* PACLOBUTRAZOL not registered and thus not recommended for use on durian at present.
REFERENCES
(1) Vangnai, V (1980). Fruit Crops Germplasm in Thailand, IBPGR/TN-PGRES/TISTR/NADC. 36 pp.
(2) Valmayor R.V., Coronel R.E. and Ramirez, D.A. (1965). Studies of Floral Biology, Fruit Set and Development in Durian. Philipp.Agrst. 48 (8-9) : 355-366.
(3) Bachau, P. C. (1972). Utilization of local Malaysian Fruits. F.A.O. Work. Pop. No. 69 22 pp.
(4) Watson, B.J. (1982). The Durian. Australian Horticulture (July) 109 - 115.
(5) Malo, S.F. and Martin, F.W. (1979). Cultivation of Neglected Tropical Fruits with Promise. Part 7. The Durian. USDA Sci. and Ed. Admin 15 pp.
DATE: March 1988
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