Research Situation of Cattleya, Dendrobium, Oncidium Orchids in Vietnam

( Oncidium ), Dendrobium , Cattleya and some other orchid species, bring huge economic benefits to the orchid production industry in countries such as the Netherlands, China, Taiwan, Thailand...

1.3.1.1 Studies on technical measures

Along with research on creating new varieties, technical measures for each orchid species are also of great interest to authors around the world, focusing on helping plants grow and develop well, increasing productivity and flower quality.

* Research on growing media

Maybe you are interested!

With the desire to find a suitable substrate to replace fiber fern and seaweed in growing Cattleya intermedia orchids at the seedling stage, Lone, AB (2008) [96] experimented with substrates such as fiber fern, seaweed, burnt rice husk, pine bark + coconut fiber in a ratio of 1:1, pine bark and coconut fiber. The results of monitoring after 10 months showed that coconut fiber and the mixture of pine bark + coconut fiber are ideal alternative substrates for Cattleya intermedia orchids .

When studying suitable substrates for transplanting Dendrobium officinale Kimura et Migo orchids after tissue culture, Guo YiHong, Sun HongJie, Shi JiQing, Wu Ya (2010) [85] concluded that the substrate consisting of peat + bark + wood chips in a ratio of 2:4:4 is most effective for the growth and development of Dendrobium officinale Kimura et Migo orchids at the seedling stage.

Supinrach, S. and Supinrach, I. (2011) [110] studied the effect of growing media on the growth of Cattleya brassolaelio Chia lin orchids at the seedling stage and determined that among 5 types of growing media: seaweed, coconut fiber, charcoal, baked clay and volcanic rock, charcoal gave the best effect on the growth of Cattleya brassolaelio Chia lin orchid stems and leaves.

Research on growing media for Cattleya orchids at the seedling stage, Júnior and Venturieri (2011) [107] studied the effects of four growing media: peat, gravel, a mixture of gravel + peat in a ratio of 3:1 and ferns on Cattleya forbesii and Laelia purpurata at the post-tissue culture stage. The results showed that ferns were the best growing media for C. forbesii and the mixture of gravel + peat was the most suitable for Laelia purpurata .

By comparing the growth and development of plants on two substrates, gravel No. 2 and gravel No. 2 + peat, the author confirmed the importance of organic matter for these orchid species.

* Fertilizer research

In 1992, Supaporn and Pornprasit [109] studied the effects of fertilizers and growth regulators on the growth and quality of Dendrobium ekapol “Panda no.1” orchids and concluded that fertilizing with 20-20-20 increased the number of pseudobulbs, increased the number of flowers and prolonged the durability of cut flowers. Adding 5 ppm α-NAA, 20 ppm vitamin B1 or 1% Liquinox-Start once a week for 1 month had the best effect on pseudobulb growth. Adding 1000 ppm Paclobutrazol once a week for 1 month had the effect of increasing the height of Dendrobium ekapol “Panda no.1”.

Yin-Tung Wang (1995) [115] studied the effects of fertilizers on the growth and development of Dendrobium orchids and concluded that Dendrobium Linapa “No.3” potted with small pine bark substrate and fertilized with N:P:K 20:8.6:16.6 at a concentration of 1 g/liter promoted the appearance and development of pseudobulbs, prolonged the life of roots, promoted flower bud formation and increased the number of flowers.

In order to determine the best N:P:K ratio for potted Dendrobium nobile Lindl., in 2008, Rebecca G. Bichsel et al. [102] studied the N and K ratios of 0; 50; 100; 200; 400 mg/liter, the P ratio of 0; 25; 50; 100; 200 mg/liter and confirmed that the N:P:K ratios of 100 mg/liter, 50 mg/liter, and 100 mg/liter, respectively, were most suitable for Dendrobium nobile Lindl orchids, helping to increase plant height, increase pseudobulb size, increase the number of flowers and flower quality.

According to Rech, AR et al (2010) [103], among the 5 light intensities tested including 12800, 8300, 6200, 5600 and 4500 lux, Dendrobium phalaenopsis compactum is most suitable for an intensity of 8300 lux. When growing orchids at this light intensity, combined with fertilizing twice a week in the summer and once every 2 days in the winter with N:P:K = 7:7:7, the plants grow well, develop well, and have high quality flowers.

In 2009, Zhang Taolil et al. [117] studied the effect of nitrogen sources in fertilizers on the growth and development of Oncidium orchids . The experiment was arranged with different ratios between NO3 - and NH4 + in fertilizers: 1:0; 2:1; 4:1; 6:1; 10:1

and 0:1. The results showed that nitrogen fertilization with a ratio of 10:1 is best for the growth and development of Oncidium orchids , nitrogen from NO3 - increases the ability to absorb Ca and Mg of Oncidium roots .

To find the most suitable fertilizer content of GaviotaTM (19-19-19) for Cattleya orchids in the seedling stage, Carnette C. Pulma et al. [65] in 2010 studied 5 fertilizer contents of 0.5; 1; 2; 3; 4 g/liter and confirmed that Cattleya seedlings grew well when fertilized with GaviotaTM (19-19-19), the number of leaves did not differ between fertilizer contents but leaf length, plant height, number of roots and fresh weight were highest when fertilized with 2-3 g/liter. The authors concluded that fertilizing with GaviotaTM (19-19-19) at a content of 2-3 g/liter helped Cattleya orchids in the seedling stage grow and develop best.

* Studies on flowering control techniques

In 1978, Goh, CJ and Yang, AL [82] when studying the effects of growth regulators (BA, GA3, IAA) on the development of Dendrobium hybrid flower branches ( D. Lady Hochoy, D. Buddy Shepler x D. Peggy Shaw) found that flowering in Dendrobium requires cytokinin (BA), while GA3 slightly increases the effect of BA, and IAA enhances the effect of BA. Goh, CJ in 1979 [83] also studied hormones regulating the flowering process in Dendrobium Luisae orchids and showed that flowers only appear after the end of the vegetative growth stage in the pseudobulb. In mature pseudobulbs, cytokinin (BA) stimulates flowering. Gibberelic acid enhances the effect but itself is not effective in stimulating flowering. Specifically, BA at a concentration of 10-3 M , the number of mature flower buds was 6 compared to BA at a concentration of 10-4 M which was 4, the total number of flowering plants was 80%. But when combining BA (10-4 M ) and GA3 (10-4 M ), the number of mature flower buds was 7, the total number of flowering plants was 100%, at the same time the length of the flower branch was longer and the flower branch development time was about 1-2 days shorter (7-8 days). While the untreated control had no ability to flower.

Vichiato, MR de M. et al (2007) [111] studied the stem elongation of Dendrobium nobile Lindl. by spraying Gibberililic Acid (GA3) to help the plant grow quickly. The results showed an increase in height of 64.08% and leaf length of 44.27%, while reducing pseudobulb diameter by 50% and leaf width by 56.09%. Content

GA3 can be used from 50-400 mg/liter.

Also in 2007, the group of authors Guek Eng Sim, Chiang Shiong Loh, Chong Jin Goh [84] studied the ability of early flowering in vitro of Dendrobium Madame Thong-In and demonstrated that BA promoted flowering and flower bud formation. Similarly, Kim Hor Hee, Chiang Shiong Loh, Hock Hin Yeoh (2007) [89] also determined that the concentration of BA 11.1µM helped induce flowering after 6 months of in vitro cultivation in Dendrobium Chao Praya Smile.

* Research on pests and diseases

Pedroso de Moraes et al. (2011) [101] studied the response of hybrid Cattleya species to bacterial wilt caused by Fusarium oxysporum f. sp. Cattleyae Foster and found that 6 out of 7 hybrid Cattleya varieties were infected with the disease at different levels. Only the hybrid BrassoCattleya Orquidacea's Melody was not found to be infected with wilt. The reason for the immunity was found to be due to evolutionary adaptation, environmental factors and mainly due to the gene combination during hybridization. Therefore, these disease-resistant plants should be used for breeding to obtain genetically resistant lines in the future.

In the same year, Chung, WC et al. [73] isolated Fusarium solani bacteria causing yellow leaf disease from diseased Phalaenopsis plants in Taiwan and tested it on different orchid species including Oncidium sp., Dendrodium sp., Cattleya sp. It was observed that the F. solani strain did not show symptoms on Oncidium , Dendrobium , Cattleya . Molecular analysis showed that the F. solani strain from Phalaenopsis was different from F. solani isolated from other species.

1.3.1.2 Other studies

* Studies on reproduction by sexual hybridization

In 1844, Newman - a French gardener germinated orchid seeds by sprinkling seeds on clods of soil around the base of large orchid plants. This success spread widely but there was no specific explanation. In 1904, Noel Bernard carried out the method of sowing seeds in symbiosis with fungi to induce germination [62]. In 1909, Hans Burgeff germinated Laelio , Cattleya seeds on a nutrient medium containing 0.33% sucrose in complete darkness [64]. In 1922, Lewis

Knudson, an American scientist, was successful in sowing seeds in agar media [90], [91]. He also found that seed germination also depends on the time of fruit harvest.

In nature, for orchid seeds to germinate, they need the support of a parasitic fungus. Bernard (1904) [62] found several species of fungi that can help germinate orchid seeds, each species has an effect on certain orchid species such as:

- Rhizoctonia repens helps germination in Cattleya , Laelia , Angraecum , Paphiopedium .

- Rhizoctonia mucoroides helps germination in Vanda , Phalaenopsis .

- Rhizoctonia lanuginosa helps germination in Oncidium , Dendrobium , Miltonoa

and Odontoglossum .

* Studies on propagation by tissue culture

Morel (1960) [98] used Cymbidium apical buds inoculated into Knudson III (C) medium to produce protocorms. In 1964 [99], he continued his experiment of cutting the protocorm into small pieces and re-inoculating it into the medium. From one protocorm, more than 4,000 seedlings/year could be produced. From Morel's experimental results, many multi-stemmed orchid varieties were successfully asexually propagated, such as Cattleya (Scully, 1967) [106] , Dendrobium (Sagawa 1984 [105]).

To improve the orchid tissue culture process, researchers have studied in depth the effects of some additives on callus and protocorm formation such as the effects of coconut water (Goh 1970, 1973; Goh et al., 1975) [79], [80], [81] with concentrations of 10-25%, tomato solution (Loh et al., 1978) [95], the effects of carbon sources and inorganic compounds (He, SL et al., 2003) [86].

From 1999 to 2002, Chen, JT et al. [68], [69], [70], [71] concluded that the environment

½ MS supplemented with 10-20 g/ liter sucrose, 170 mg/ liter NaH 2 PO 4 and 0.5 g/ liter peptone is most suitable for direct embryogenesis from On. Gower Ramsey orchid explants.

In 2009, José Geraldo [87] and Rezende [104] studied the effects of different concentrations of sucrose and GA3 on the development of protocorms from germinated seeds of the orchid Cattleya loddigesii sp. and concluded that concentrations of 0 mg M-1 GA3 and

60 mg M -1 sucrose gave the best root number and root growth of Cattleya loddigesii sp.

Dai Chuan Yun et al. (2011) [74] studied and determined the optimal environment for rapid multiplication of protocorm of orchid Dendrobium candidum Wall. ex Lindl. is 1/2MS + 6-BA 2mg/l + αNAA 0.5mg/l + KT 1mg/l. This study has provided a scientific basis for industrial-scale production of protocorm and high-quality propagation of D. candidum .

* Research on the application of biotechnology to create new varieties

Applying biotechnology in orchid breeding, some authors have successfully transferred genes into orchid varieties at the protocom stage such as Dendrobium (Chia TF (1994) [72], Wang, Y. et al. (2005) [112]), C.hybridium ( Kyaw Thu Moe (2010) [93]). In the same year, Belarmino and Mii successfully transferred genes into Phalaenopsis orchids using Agrobacterium bacteria [61]. Also using this type of bacteria, Yu H. (2001) transferred the DOH1 gene into the Dendrobium Madame Thong-In orchid variety to create multi-stem plants in an environment containing 50 mg/liter of carbenicillin [116]. In 2004, Sai Minh Luong concluded that after injecting into protocoma and culturing with Pcambia 1300- SmGFP and LBA4404 of gfp and hpt genes, transgenic plants could be obtained [67].

Benner (1995) [97], Chyi Chen (2000) [77], Khosravi (2009) [88] used RAPD markers to analyze polymorphism and genetic relationships of the genera Cattleya, Dendrobium, Oncidium and established DNA polymorphism maps, facilitating the identification of the characteristics of the above orchid species.

The above results show that there have been many research projects in the world on orchids in general and Cattleya, Dendrobium, Oncidium orchids in particular. The research has focused on a number of areas such as breeding, propagation, technical measures and measures to prevent pests and diseases, etc.

These results are important in helping orchid researchers and producers in our country inherit experience, save time and money to bring high efficiency in orchid breeding and cultivation in Vietnamese conditions.

1.3.2 Research situation of Cattleya, Dendrobium, Oncidium orchids in Vietnam

1.3.2.1 Studies on collection and evaluation of varieties

In Vietnam, there are also many studies on collecting and preserving native and imported orchid gene sources. In 1991, the Dalat Institute of Biology collected wild orchids from Lam Dong including Dendrobium , Cattleya , and Cymbidium . These orchid species were brought back to be planted to monitor biological characteristics (flowering season, morphology, color, and fragrance) and to build an orchid collection to preserve gene sources, as a source of materials for the selection and breeding of precious orchid varieties to serve the needs of consumption and export.

Researching the collection, evaluation and selection of some imported Dendrobium orchid varieties in the Northern Delta region, Pham Thi Lien and colleagues (2009) collected 6 Dendrobium orchid varieties from Thailand, including 3 varieties originating in Bangkok, 2 varieties in Chiang Mai and 1 variety in Chiang Rai. The varieties all have high productivity, beautiful flowers, and are currently very popular in the domestic and foreign markets. Based on the evaluation of the agrobiological characteristics, cold tolerance, recovery ability and disease resistance of the 6 Dendrobium orchid varieties, the authors selected 3 varieties: White Purple ( D. sonia 18), White Tuyen ( D. mee white) and White Purple Lips ( D. woon leng) for high productivity and flower quality, suitable for the ecological conditions of the Northern Delta region and are continuing to research the breeding process to develop widespread production [22].

According to Duong Hoa Xo, the Ho Chi Minh City Biotechnology Center has implemented the project "Collecting, importing, testing and propagating orchid varieties", from 2005 to present, it has collected more than 285 orchid varieties belonging to 12 different groups ( Mokara , Dendrobium , Phalaenopsis , Oncidium ...), to serve the work of preserving gene sources and breeding varieties, especially including more than 80 precious wild orchid varieties, which can serve the work of breeding orchid varieties. In addition, the Center has imported 14 Mokara orchid varieties , 13 Dendrobium varieties , 5 Cattleya varieties for testing and rapid propagation to serve production requirements [58]. Not only state research facilities invest in developing orchid production

Many provinces and cities such as Hanoi, Quang Ninh, Bac Ninh, Lao Cai, Vinh Phuc, Son La, Hai Duong, Thai Binh, Hung Yen, Thua Thien Hue, Quang Nam, Binh Dinh, Phu Yen... have also invested funds and coordinated with the Institute of Agricultural Genetics, the Institute of Vegetable and Fruit Research, the Institute of Biology - Hanoi University of Agriculture to collect and preserve native and imported orchid species [47].

1.3.2.2 Studies on technical measures

* Research on growing media

The substrate is the living environment of orchids, depending on each orchid species and growing conditions to choose the appropriate substrate. According to Phan Thuc Huan (1989) [12], the most commonly used substrate in growing orchids in general and Cattleya, Dendrobium, Oncidium orchids in particular includes coconut fiber, pumice, charcoal, wood, bricks, fern rhizomes, water hyacinth roots, seaweed, etc. The substrate for growing orchids is very different from other plants, they are used to improve humidity and mechanical effects rather than providing nutrients. The structure of the substrate is the condition that determines the growth of orchids, the grafting method on living and dead tree trunks, the substrate is the bark of the host trunk. If planted in pots, the substrate must be very airy at the bottom to avoid waterlogging. In cold areas like Da Lat, the structure of the substrate is too airy, which is disadvantageous for the growth of the plant because the cold temperature at night damages the roots. Therefore, a closed substrate will help the roots have conditions to develop, fern chips are effective in this condition.

- Coconut fiber: Is an important component in orchid growing media. According to Minh Tri, Xuan Giao (2010) [40], coconut fiber has the characteristics of absorbing water slowly but retaining moisture for a long time, draining water, containing many minerals to nourish orchids, however, when using it, it is necessary to soak it in water to reduce the amount of salt and pay attention to the watering regime, do not let it be flooded causing the substrate to rot.

- Bark: Tran Van Bao (2001) [1] confirmed that many types of bark can be used as a growing medium for orchids, but you should choose bark that does not rot for a long time to prevent water from stagnating in the orchid pot, causing root rot. Bark is also a habitat for many pests, diseases, and snails, so it is necessary to check the growing medium regularly to change the pot and growing medium for the orchid.

- Charcoal: Is a cheap material, commonly used in cultivating Cattleya and Oncidium species . Charcoal contains few pathogens and is non-toxic .

Comment