Cataloguing and documentation of diseases of sympodial orchids in kerala
| dc.contributor.advisor | Deepa, James | |
| dc.contributor.author | Anjali, P | |
| dc.contributor.author | KAU | |
| dc.date.accessioned | 2024-08-23T06:14:33Z | |
| dc.date.available | 2024-08-23T06:14:33Z | |
| dc.date.issued | 2023-07-15 | |
| dc.description.abstract | Orchids are valued for their exotic beauty and long vase life, making them one of the most popular cut flowers and ornamental plants worldwide. Currently, orchids hold sixth position among the top ten cut flowers in the world, among which, sympodial orchids rank higher in the export market. However, orchid cultivation is challenged by many biotic factors especially fungal, bacterial and viral diseases, which reduce production potential and economic value. Hence, the present study, ‘Cataloguing and documentation of diseases of sympodial orchids in Kerala’ was proposed with the objective to document various diseases affecting sympodial orchids in Kerala. A purposive sampling survey in orchid growing areas of three districts viz., Thrissur, Ernakulam and Thiruvananthapuram conducted revealed the incidence of leaf blight, leaf spot, wilt, black rot, soft rot, twig blight, petal blight and flower spot diseases in four different sympodial orchids such as Dendrobium spp., Cattleya spp., Oncidium spp. and Spathoglottis spp. Among the 49 diseased samples collected from eight different locations, 21 diseased samples were obtained from Dendrobium spp., 16 from Oncidium spp., six from Cattleya spp. and six from Spathoglottis spp. PDS and PDI were calculated for each symptom from Dendrobium spp., and the highest PDI and PDS were recorded for VY DLB (76.47 %) and MT DLB1 (36.67 %) respectively. In Cattleya spp. highest PDI and PDS were recorded for VY CLS (70.80 %) and VP CSR (48.5 %) respectively. In Cattleya spp. highest PDI and PDS were recorded for VY CLS (70.80 %) and VP CSR (48.5 %) respectively. In Oncidium spp., the highest PDI and PDS were recorded for VK OLS1 with 76.92 per cent and 46.90 per cent respectively. In Spathoglottis spp., highest PDI (48.0 %) and PDS (29.79 %) were recorded for MT SLB1. From the PDS and PDI data, it was found that, leaf blight symptoms were more common and severe in Dendrobium spp. whereas leaf spot symptoms were more severe in Oncidium spp. In Cattleya spp., leaf spot symptoms were most frequently noticed, and soft rot symptom showed highest disease severity. In Spathoglottis spp., leaf blight symptoms were most frequent and severe. PDS and PDI values were correlated with light intensity at different survey locations, and a negative correlation was observed. Isolation of pathogens from diseased samples yielded 52 fungal isolates and one bacterial isolate from different sympodial orchids. A total of 21 fungal isolates were obtained from Dendrobium spp.,18 fungal isolates from Oncidium spp., five fungal isolates and one bacterial isolate from Cattleya spp. and nine fungal isolates from Spathoglottis spp. All the isolates showed different symptoms upon artificial inoculation and these isolates could be reisolated and confirmed as pathogens. The pathogens were identified at generic level based on cultural and morphological characteristics. Different fungal isolates, such as Fusarium spp. (9 nos.), Colletotrichum spp. (6 nos.), Alternaria spp. (2 nos.), Sclerotium spp. (2 nos.), Phytophthora sp. (1 no.) and Curvularia sp. (1 no.) were obtained from various symptoms collected from Dendrobium spp. The pathogens isolated from Oncidium spp. were Colletotrichum spp. (11 nos.), Diplodia sp. (1 no.), Diaporthe sp. (1 no.), Pestalotia sp. (1 no.), Alternaria sp. (2 nos.), Phytophthora sp. (1 no.) and Fusarium sp. (1 no.). Fungal isolates such as Colletotrichum spp. (2 nos.), Fusarium sp. (1 no.), Lasiodiplodia sp. (1 no.), and a bacterial isolate, Pectobacterium sp. were isolated from Cattleya spp, and Colletotrichum spp. (7 nos.), Fusarium sp. (1 no.) and an unidentified fungal culture were obtained from Spathoglottis spp. Molecular characterisation of major pathogens from Dendrobium spp., Oncidium spp., Cattleya spp. and Spathoglottis spp. was done for species level identification. Leaf blight pathogens, VL DF1, VY DF, IK DF1 and MT DF1 were identified as Colletotrichum boninense, Fusarium proliferatum, Fusarium oxysporum and Sclerotium rolfsii respectively, and the leaf spot pathogen, VP DF1 was identified as Alternaria alternata. The leaf spot pathogens, VK OF3 and IK OF1 from Oncidium were identified as Colletotrichum sp. and Diaporthe tulliensis respectively. The isolate, VY CF2 causing leaf spot disease in Cattleya was identified as Lasiodiplodia theobromae and the fungus MT SF1, causing leaf blight symptom in Spathoglottis was identified as Colletotrichum gloeosporioides. The bacteria (VP CB) causing soft rot symptom in Cattleya was identified as Pectobacterium aroidearum. In vitro studies were carried out using chemicals and biocontrol agents against seven fungal pathogens and one bacterial pathogen. Based on the data, hexaconazole was the most effective among the systemic fungicides, which showed 100 per cent inhibition of Colletotrichum boninense (VT DF1), Fusarium proliferatum (VY DF), Sclerotium rolfsii (MT DF1), Alternaria alternata (VP DF1) and Colletotrichum gloeosporioides (MT SF1) at all three doses. The fungicide also showed 100 per cent inhibition of Lasiodiplodia theobromae (VY CF2) at higher dose, while it was least effective (38.33-79.58 %) against Colletotrichum sp. (VK OF3). Bordeaux mixture (1 %) was found to be the most effective contact fungicide, which showed complete inhibition of all pathogens under study except Alternaria alternata (76.25 %). Among two combination fungicides evaluated, carbendazim 12 % + mancozeb 63 % could inhibit all fungal pathogens except Alternaria alternata (52.91 to 65 %). Among the chemicals evaluated against Pectobacterium aroidearum, copper hydroxide showed a maximum per cent inhibition (25.92 %) followed by 1 % Bordeaux mixture (15.5 %) while streptocycline showed per cent inhibition ranging from 0-16.67 per cent. Among the biocontrol agents evaluated, PGPM showed maximum inhibition per cent against the fungal pathogens (60.41-100 %) followed by PGPR-II (50.41-100 %) and Trichoderma asperellum (20.41-91.16 %), while Pseudomonas fluorescens was found to be least effective. In the case of Pectobacterium aroidearum, no inhibition was found when evaluated with P. fluorescens, PGPR-II and PGPM. However, Trichoderma asperellum exhibited a lower inhibition percentage (26.67 %) against the bacterial pathogen. Bioassay studies revealed that carbendazim 12 % + mancozeb 63 % was highly effective against Colletotrichum boninense (VT DF1), followed by Fusarium proliferatum (VY DF), S. rolfsii (MT DF1) and Colletotrichum sp. (VK OF3), whereas the fungicide was found least effective in controlling Lasiodiplodia theobromae (VY CF2) under in planta condition. Hence the study has thrown light upon the diseases affecting sympodial orchids in Kerala and disease management by chemicals and biocontrol agents under in vitro condition. | |
| dc.identifier.uri | https://krishikosh.egranth.ac.in/handle/1/5810213624 | |
| dc.keywords | Department of plant pathology | |
| dc.keywords | Orchids | |
| dc.keywords | Diseases of sympodial orchids | |
| dc.language.iso | English | |
| dc.pages | 192p. | |
| dc.publisher | Department of plant pathology,Vellanikkara | |
| dc.sub | Plant Pathology | |
| dc.theme | Orchids are valued for their exotic beauty and long vase life, making them one of the most popular cut flowers and ornamental plants worldwide. Currently, orchids hold sixth position among the top ten cut flowers in the world, among which, sympodial orchids rank higher in the export market. However, orchid cultivation is challenged by many biotic factors especially fungal, bacterial and viral diseases, which reduce production potential and economic value. Hence, the present study, ‘Cataloguing and documentation of diseases of sympodial orchids in Kerala’ was proposed with the objective to document various diseases affecting sympodial orchids in Kerala. | |
| dc.these.type | M.Sc | |
| dc.title | Cataloguing and documentation of diseases of sympodial orchids in kerala | |
| dc.type | Thesis |