• Journal of Bio-Environment Control
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• v.25 no.4
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• pp.351-358
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• 2016

This study investigated the effect of different relative humidity (RH) regimes on graft healing of grafted seedlings of watermelon (Citrullus vulgaris Schrad.). Two watermelon cultivars ('Speed' and 'Sambok Honey') were grafted onto the 'RS-Dongjanggun' bottle gourd rootstock (Lagenaria siceraria Stanld.) and the grafted seedlings were maintained under one of three relative humidity regimes, 95-96% [1.1-0.8 (day) or $0.8-0.6(night)\;g{\cdot}m^{-3}$ vapor pressure deficit (VPD)], 97-98% [ 0.7-0.4 (day) or $0.5-0.3(night)\;g{\cdot}m^{-3}$ (VPD)], or 99-100% [0.3-0.0 (day) or $0.2-0.0(night)\;g{\cdot}m^{-3}$ (VPD)] according to the Mollier diagram based on the air temperature of $25^{\circ}C\;day/18^{\circ}C\;night$ with 16 h photoperiod per day. Among the RH treatments, 97-98% significantly increased plant height and fresh weight of the rootstock and scion of the 'Speed' and it also enhanced the graft union connection of both cultivars after two days of grafting. However, plant height and thickness of the scion of 'Sambok Honey' was increased by the 99-100% RH treatment. Furthermore, both cultivars grown in the 95-96 and 97-98% RH treatments consisted of lower levels of endogenous $H_2O_2$ and less activities of antioxidant enzymes which illustrated the occurrence of less oxidative stress. Hence, the results of this study identified the optimal RH level for the graft healing of watermelon seedlings.

• Korean Journal of Environmental Agriculture
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• v.31 no.1
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• pp.60-67
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• 2012

BACKGROUND: Anthracnose disease caused by Collectotrichum spp. is one of the most important worldwide devastating diseases in red pepper plants. Fungicides using plant extracts have several advantages, compared to synthetic chemical fungicides, because they are naturally occurring compounds, are usually safe for agricultural environment and are used for producing highly valuable agricultural products. Efforts for seeking an anti-fungal activities using naturally occurring compounds were mostly conducted from medicinal plant extracts. Sap of Rhus verniciflus was known to have healing effects on several human diseases. Recently, the extracts of Rhus verniciflus were actively tested for anti-cancer, anti-oxidative, and anti-fungal effects. In this study, the extract of Rhus verniciflus was tested for anti-fungal activity against Colletotrichum spp., which cause anthracnose in red-pepper. METHODS AND RESULTS: After neutralizing extracts of Rhus verniciflus (urushiol contents 70%) with autoclave, the crude extracts were used to investigate inhibitory effects for mycelial growth and spore germination of Colletotrichum spp. on PDA media. The mycelial growth and spore germination of Colletotrichum spp. were inhibited 18-39% and over 50% in response to crude extract of R. verniciflus (1.0 mg/mL). After spraying the extracts at the same concentrations above and then artificially inoculating Colletotrichum spp. on blue and red-pepper fruits, in vitro inhibition effects were examined. At 1.0 mg/mL, the crude extract of R. verniciflus showed inhibition activity in anthracnose incidence on blue- and red-pepper as 68.1-75.0%, through a artificial inoculation of Colletotrichum spp. in a laboratory. For in vivo inhibitory effects, the extracts (1.0, 0.1, and 0.01 mg/mL) were treated on red-pepper plants grown in green house 3 times at the interval of 1 week. Then inhibitory effects were determined by counting diseased fruits at 1 week after final treatment. The incidence of anthracnose was inhibited over 60% in the greenhouse by treatment of crude extract of R. verniciflus (1.0 mg/mL). CONCLUSION(s): Extracts of Rhus verniciflus were shown to have inhibitory effects on mycelial growth, spore germination of Colletotrichum spp. in vitro and on occurrence of anthracnose on pepper fruit in green house.