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Antifungal Activity and Phytochemical Analysis of Myrtaceae Leaf Extracts including the Induction of Defense Enzymes in Lettuce against Alternaria Leaf Spot
(2025-01-01)
Somnuek, Suriyasit
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Thipmanee, Kamronwit
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Jaenaksorn, Tanimnun
To avoid the risk of harmful effects from synthetic fungicides on human and natural environments, our study aimed to evaluate the potential use of the indigenous Thai Myrtaceae plants as a harmless means for controlling the plant diseases. Four Myrtaceae extracts showed no phytotoxicity towards lettuce cultivated in hydroponic conditions, with notable plant-growth-promoting potential observed in lettuce treated with Callistemon viminalis (EECV). With regard to a direct effect, Melaleuca cajuputi (95% EEMC) showed the strongest inhibition of mycelial growth of A. brassicicola (85–100%), followed by 95% EECV (40–63%), while both extracts significantly inhibited spore germination (80–100%). A GC/MS and LC/MS analysis revealed terpenoids as the predominant compounds at approximately 55% and 37% in EEMC and EECV, respectively, with high concentrations of phytol (14%) and 1,8-cineole (14%) being particularly notable. As an inducer of an indirect effect of the plant extracts, the results from the experiment with 95% EEMC (15,000 and 50,000 ppm) as well as 50 and 95% EECV (15,000 and 50,000 ppm) applications was in good agreement, demonstrating significant reductions in disease severity in hydroponically grown lettuce ranging from 50 to 70% together with the induction of defense enzymes (specifically β-1,3-glucanase, chitinase, and peroxidase) compared to those in the inoculated control and fungicide treatment groups. Furthermore, a correlation analysis revealed a negative correlation between disease severity and the three defense enzymes. Our findings underscore the considerable efficacy of the three botanical fungicides tested here (i.e., 95% EEMC as well as 95% and 50% EECV) for the management of Alternaria leaf spot in lettuce.
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Non-Pathogenic Pythium Induced the Resistance in Hydroponic Lettuce Against Root Rot Disease
(2024-05-01)
Talubnak, Chulalak
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Parinthawong, Nonglak
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Schoonbeek, Henk Jan
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Jaenaksorn, Tanimnun
Hydroponics is a common soilless type of culture. It is clean and gives high-yield crop production. Lettuce is the most widely grown leafy vegetable in hydroponics. The Pythium species causes root rot, a serious disease in lettuce. In this study, we investigated an effective elicitor to promote resistance in lettuce after pathogen infection. To evaluate the plant defense gene response profile, the expression stability of five candidate genes was studied using RT-qPCR. The LsPR1 and LsLTC2 gene expression were higher in lettuce leaves treated with non-pathogenic Pythium PyASR23 than in roots compared to untreated plants. To assess the disease, the rate of relative gene expression of LsLTC2, LsPR-1b like, LsERF, LsAOS, and LsDEF was associated with Pythium root rot pathogenesis. As a result, it was revealed that alterations in these gene expressions were a defense response to Pythium infection, which increased after pre-treatment with various elicitors for 24 hours. When the chemically stimulated lettuce was infected with pathogenic PySR31, the expression of these genes increased dramatically. These results suggested that non-pathogenic PyASR23 might be employed as an elicitor in lettuce roots and contribute to disease control by activating plant defense gene expression against the Pythium pathogen.
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Cross-Resistance to Benzimidazole Group and Mancozeb Fungicides in Colletotrichum spp. Causing Anthracnose Disease
(2022-10-01)
Kongtragoul, Pornprapa
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Somnuek, Suriyasit
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Udompongsuk, Mongkutkarn
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Prasom, Panisa
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Jaenaksorn, Tanimnun
Anthracnose is considered to be one of the most serious diseases for major crops cultivated in Thailand. Although chemical fungicides and newer chemicals have been recommended and used for disease management, it is still difficult to control. Thus, the monitoring of fungicide resistance development is required and very important for the success of disease control strategies. In this study, a total of 34 isolates of Colletotrichum spp. were successfully collected from anthracnose diseased plants in central Thailand. Of these isolates, 16 were collected from mango, and 2 from crinum lily or orchid and were morphologically identified as C. gloeosporioides, while the other 16 isolates from chili were morphologically identified as C. capsica. Then, all isolates were evaluated in vitro against 3 fungicides to determine their sensitivity. The results showed that 25 isolates were cross-resistant to both benomyl and carbendazim, as the 50% effective concentration (EC<inf>50</inf>) of each fungicide was >100 mg L<sup>-1</sup>. All isolates were resistant to mancozeb. Nine out of 16 isolates from mango anthracnose were confirmed as C. gloeosporioides by the sequence of internal transcribed spacer (ITS) and 5. 8S regions of rDNA. Eight cross-resistant isolates were not controlled by the treatment with 100 mg L<sup>-1</sup> of benomyl or carbendazim on ‘Nam Dok Mai’ mango fruits, but sensitive isolate was better controlled at 79.33% and 85.11%, respectively. Our results indicated that cross-resistant strains are present in the populations of anthracnose fungi in central Thailand.
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Morphological and Molecular Identification of Pythium spp. from Hydroponically-Grown Lettuce
(2022-01-01)
Talubnak, Chulalak
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Schoonbeek, Henk Jan
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Parinthawong, Nonglak
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Jaenaksorn, Tanimnun
Herein, hydroponic Pythium communities in Thailand were investigated. The 38 Pythium isolates from asymptomatic and symptomatic lettuce roots were identified using morphological and molecular features. The data indicated that P. aphanidermatum and P. myriotylum were the predominant species. Regarding the rDNA-ITS study, all isolates were identified as P. aphanidermatum, P. myriotylum, P. deliense, or an unidentified Pythium species. The reconfirmation of the three unidentified Pythium isolates using the cytochrome oxidase subunit I (COI) gene in comparison to the representative isolates was achieved using P. aphanidermatum and P. myriotylum. The COI phylogenetic trees were similar to that of the ITS tree. Additionally, pathogenicity of the Pythium representative isolates to plant seeds was evaluated in a laboratory assay. The seedlings suffered serious symptoms from P. myriotylum SR31 infection, with 90-100% disease severity. The other isolates presented disease severity of less than 20% when compared with uninoculated control. This study provides a comprehensive identification of Pythium root rot in lettuce grown on hydroponics in Thailand and provides information on beneficial microorganisms and a resistance inducer in lettuce root rot.
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Effect of crude ethanolic extracts from bottle brush (Callistemon viminalis) against leaf spot fungi and their phytotoxicity on lettuce (lactuca sativa l.)
(2020-01-01)
Somnuek, Suriyasit
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Jaenaksorn, Tanimnun
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Laosinwattana, Chamroon
In response to the public concern about environmental problems as well as fungicide residues on agricultural produces especially leaf vegetables, we investigated the potential use of crude extracts from bottle brush (C. viminalis) leaves against leaf spot fungi and their phytotoxicity on lettuce grown in hydroponics. Yield, total phenolic and flavonoid contents of the extract were also evaluated. Regarding the in vitro antifungal assay using poisoned food technique, 3×3 factorial in Completely Randomized Design (CRD) was employed with three replicates. Factor A was 3 crude extracts (50% ethanol, 70% ethanol and 95% ethanol crude extract) while factor B was the 3 concentrations (0, 5,000 and 50,000 ppm) of crude extracts. Results showed that all three crude extracts were significantly effective in inhibiting the mycelial growth and sporulation of leaf spot fungi (Alternaria sp. and Curvalaria sp.). There was a significant interaction between all extracts and their concentration regarding inhibition percent. Increase in crude extract concentrations resulted in a marked increase in their inhibition. The 50,000 ppm gave the highest effectiveness. For phytotoxicity test, all tested crude extracts did not give any negative effects either on seed germination or growth of lettuce grown in hydroponics. Interestingly, growth promotion about 30 percent was achieved on this regard. Based on quantitative assay, the highest yield of crude extract was obtained from 95% ethanol solvent. Highest total phenolic and flavonoid contents were detected at the highest concentration of all crude extracts.
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Phytoalexin production of lettuce (Lactuca sativa L.) grown in hydroponics and its in vitro inhibitory effect on plant pathogenic fungi
(2017-09-01)
Talubnak, Chulalak
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Parinthawong, Nonglak
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Jaenaksorn, Tanimnun
A series of experiments were conducted to investigate phytoalexin production from five varieties of lettuce in hydroponics using abiotic (2.5, 5% CuSO<inf>4</inf>; 0.5, 1% AgNO<inf>3</inf>) and biotic elicitors (non-pathogenic Pythium sp.) at different plant ages. It showed that phytoalexin was successfully induced in tested lettuce grown in hydroponics after elicitation with abiotic elicitors throughout the trial. Phytoalexin showed yellow fluorescent spot under 365 nm UV light with R<inf>f</inf> 0.45-0.48 and clear inhibition zone where Aspergillus niger failed to develop on TLC plate. For biotic elicitors, no yellow fluorescent spot on TLC plate was observed from tested lettuce varieties however inhibition zone at R<inf>f</inf> 0.9 was detected at 8-9 weeks from red oak, green oak, and red coral. Moreover, crude extract of lettuce elicited with abiotic elicitors possessed in vitro antifungal activity against C. gloeosporioides, C. lunata, F. oxysporum, and P. aphanidermatum probably due to phytoalexin (lettucenin A) in the extract.
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Fusarium oxysporum (F221-B) as biocontrol agent against plant pathogenic fungi in vitro and in hydroponics
(2017-01-01)
Thongkamngam, Titi
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Jaenaksorn, Tanimnun
Efficacy of non-pathogenic Fusarium oxysporum (F221-B) was assessed as a possible biocontrol agent against fungal pathogens, namely Curvularia lunata (C11, C12), F. semitectum (F113), F. oxysporum f.sp. lactucae (F221-R, F442-G), Rhizoctonia solani (R11, R12), Rhizoctonia sp. (R111, R112, R113) in vitro, while F221-B showed a moderate ability to inhibit the mycelial growth of tested fungi about 36–56%. Then, F221-B was further evaluated for its ability of controlling lettuce root rot and wilt caused by F442-G in hydroponics. It was revealed that F221-B reduced disease incidence and severity about 60–80% compared to the inoculated control and significantly promoted the growth of 3 lettuce varieties. Interestingly, using only F221-B gave the significantly highest fresh weight (twice over the healthy control). Conclusively, this study provides an important suggestion for further development of F221-B since it showed the ability of biocontrol agent and plant growth promoting fungus.
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Problems and countermeasures in the re-use of the nutrient solution in soilless production
(2002-06-30)
Ikeda, Hideo
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Koohakan, Prommart
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Jaenaksorn, Tanimnun
In this report, problems of pathogen contamination in nutrient solution, imbalance of the minerals, pH and EC control, and accumulation of phytotoxic substances in the solution and the countermeasures for these problems are reviewed. Also, the growing system and the technique of the nutrient solution management for the zero run-off are proposed.
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