Identification of Disease and Efforts to Protect Natural Orchid Plants Against Fungi Infection in the Liwa Botanical Garden

Liwa Botanical Garden is located in West Lampung Regency which has an area of 86.6 hectares and is one of the conservation of ornamental plants that presents the flora of the Bukit Barisan Selatan National Park. One of the flagship collections of this botanical garden is a native orchid. Disease infection is still a major obstacle in the cultivation and development of native orchid potential at Liwa Botanical Garden. Based on the results of previous studies, it is known that several individual natural orchid collections from Liwa Botanical Garden showed symptoms of fungal disease infections. Disease infections can inhibit plant growth and resistance and reduce the aesthetic value periodically. Symptoms of infection include necrotic patches on the upper surface of the leaf. This research was conducted to determine the identification of diseases and efforts to protect native orchids against fungal infections at Liwa Botanical Garden through a collection of samples that showed symptoms of infection, analysis of disease symptoms, and analysis of disease resistance levels. The results showed that the response of the native orchid at Liwa Botanical Garden to fungal infections was showed symptoms of wilting in the leaves, namely in the orchids Eria sp., Dendrobium sp., and Cymbidium sp. turns black on the edge of the leaf, Thrixspermum sp. The type of orchid most commonly infected with fungus is Cymbidium sp. a total of 8 samples, and Thrixspermum sp. 3 samples, Eria sp. as many as 4 samples, Dendrobium sp. and Calanthe triplicata as many as 6 samples. The type of native orchid that is most susceptible to fungal infections is Dendrobium sp. and Eria sp. with disease intensity of 74.11% and 22.3%. The results of this activity are expected to be basic information in efforts to protect plants against diseases to support the application of conservation of native orchids on Liwa Botanical Garden.


Introduction
Liwa Botanical Garden is located in Kubu Prahu Village, Balik Bukit District, Liwa-West Lampung Regency. This botanical garden has an area of 86.6 hectares which is one of the conservation of ornamental plants that presents the rich flora of the Bukit Barisan Selatan National Park [21], one of which is natural orchids. The native orchid collection at the Liwa Botanical Garden was obtained from exploration and donation activities. Until November 2013 there were 384 exploration numbers and 41 donation numbers from the Bogor Botanical Gardens [3]; [5]; [17].
Disease infection is still a major obstacle in the cultivation and development of natural orchid potential at Liwa Botanical Garden. Based on the results of previous studies, it is known that several individual natural orchid collections from Liwa Botanical Garden showed symptoms of fungal disease infections. Disease infections can inhibit plant growth and resistance and reduce the aesthetic value periodically. Symptoms of infection include necrotic patches on the upper surface of the leaf [2]; [8]; [9]. Plant diseases caused by fungi generally spread through the soil. The fungus can infect the root area and base of the stem, as a result the plant will experience wilting, seedling / sprout (damping-off), root rot, or root neck [4]; [10]; [11]; [12]; [14]; [15].
To facilitate the control of fungal diseases, an inventory of data is first carried out as basic information regarding the infection of the disease. Recognition of symptoms as an infection response is the first data in disease identification [16]. The data is used to determine disease intensity and plant resistance and control. Based on the above it is necessary to conduct research activities related to the identification of diseases and efforts to protect natural orchid plants against fungal infections at Liwa Botanical Garden. The results of this study are expected to be basic information in efforts to protect orchids to support the application of conservation at Liwa Botanical Garden.

Sample Collection
Sample collection was carried out on orchid leaves in Liwa Botanical Garden which showed symptoms of being infected with a virus. All samples were tabulated and documented with photos.

Analysis of Disease Symptoms
This analysis is done by matching the sample documentation with the literature that has been previously reported. The literature used is [17].

Disease Intensity Analysis
This stage is done to determine the severity of the disease (disease severity). Disease intensity is the proportion of infected hosts to the total observed surface area of the host. Calculation of disease intensity analysis is done using the method of [20] and the scale of disease intensity refers to [17].

Plant Resistance Level
Determination of the level of resistance of orchids to disease follows the method of [17].

Sample Collection
The sample collection stage is conducted in the second week of January to the second week of February 2020. Samples are randomly selected from orchid individuals who show symptoms of fungal infection at the Liwa Botanical Garden green house. Based on the collection results obtained 21 samples from 5 types of orchids, i.e: Eria sp., Thrixspermum sp., Cymbidium sp., Dendrobium sp., Calanthe triplicata. The type of orchid that is most infected with fungi is Cymbidium sp. as many as 8 samples. Furthermore orchid Eria sp. 4 samples, Thrixspermum sp. as many as 3 samples, while Dendrobium sp. and Calanthe triplicata with 6 samples. Overall data collection results are shown in Table 1. The selection of sampling locations is based on previous research [17] which reported a fungal infection in the native orchid collection at Liwa Botanical Garden in August and December 2019. Types of orchids infected with fungi are Cymbidium and Corynborsis with mixed virus symptoms, fungus, and bacteria. In this study, Cymbidium sp. being the most orchid-infected type of orchid. This shows that this type of orchid is the most vulnerable host infected with pathogenic fungi. Apart from that are orchids Eria sp., Thrixspermum sp., Dendrobium sp., Calanthe triplicata. Other studies also report the presence of fungal infections with symptoms of wilting in 3 types of Dendrobium stratiotes, Dendrobium moschatum, Dendrobium concinnum, and Pteroceras unguiculatum at Bogor Botanical Gardens [1]. [7] also reported infection with Phalaenopsis sp. in Lembang, West Bandung with symptoms of fungus spots. Some research also shows that orchids in some locations are infected by fungus. Anita [1] reports that on Dendrobium sp. also showed a fairly severe fungal infection at Bogor Botanical Garden. Thrixspermum sp. symptoms caused by the leaves turn black on the edge of the leaf, looks like a spot. In Dendrobium sp. symptoms caused by all parts of the leaves withering yellow, the fungus that infects this orchid is Sclerotium rolfsii. On Eria sp. and Cymbidium sp. have the same symptoms, namely the leaves become dry brown there is the middle to the tip of the leaf. The fungus that infects this orchid is Phytoptora palmivora. In contrast to Calanthe triplicata the symptoms caused by this orchid are black spots on the flower. This infecting fungus is Botrytis cinerea. Whereas in Calanthe triplicata the infected part is a part of the flower. The symptoms that arise are black spots on the flower petals.

Analysis of Disease Symptoms
The difference in symptoms caused by several factors, one of which is the type of orchid. Each type of orchid shows a different character from one another [18]; [19]; [23]. The habitat of the orchid plant influences the growth of orchids such as the influence of sunlight, climate conditions, temperature, humidity and the availability of nutrients that support the growth of orchids, and affect the quality and quantity of flowers produced [6]; [13]; [22]; [24]. Overall symptoms of fungal diseases infecting natural orchids at Liwa Botanical Garden are showed on Fig. 2.

Disease Intensity
The results of analysis of disease intensity of fungal diseases on native orchids at Liwa Botanical Garden, obtained the percentage of intensity as showed at Table 2.

Plant Resistance
The results of the analysis of the level of resistance to fungal diseases in native orchids in Liwa Botanical Garden are showed on Table 3. On Dendrobium sp. has a resistance level that is vulnerable because it has an incidence of more than 40%, while other orchids have a rather resistant level.

Conclusion
Response of the native orchid at Liwa Botanical Garden to fungal infections was showed symptoms of wilting in the leaves, namely in the orchids Eria sp., Dendrobium sp., and Cymbidium sp. turns black on the edge of the leaf, Thrixspermum sp. The type of orchid most commonly infected with fungus is Cymbidium sp. a total of 8 samples, and Thrixspermum sp. 3 samples, Eria sp. as many as 4 samples, Dendrobium sp. and Calanthe triplicata as many as 6 samples. The type of native orchid that is most susceptible to fungal infections is Dendrobium sp. and Eria sp. with disease intensity of 74.11% and 22.3%. The results of this activity are expected to be basic information in efforts to protect plants against diseases to support the application of conservation of native orchids on Liwa Botanical Garden.