• Research in Plant Disease
• /
• v.20 no.2
• /
• pp.126-128
• /
• 2014

This study was carried out to assay the disease incidence degree of Sclerotium rot caused by Sclerotium rolfsii in sixteen most popular commercial cultivars of sweet potato (Ipomoea batatas) in Republic of Korea. The degree of disease incidence was evaluated on pot experiments. In pot experiments using artificial inoculation, the Sclerotium rolfsii caused a stem rot on seedling of sweet potato plants and causes a crown rot on lower stems near or at the soil line at favorable environmental conditions. White mycelial mats and sclerotia were formed at the infection sites. Plants severely infected were fell over or died because lower stems near soil surface were rotten. The degree of disease incidence was varied according to cultivars. Two cultivars, Bio-mi and Deayumi, were very resistant, while five cultivars, Shinjami, Shingeonmi, Hongmi, Yeonjami, and Shinhung-3 were highly susceptible.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.39 no.4
• /
• pp.68-75
• /
• 2007

In order to supplement insufficient nutrients of paper sludges, additional materials such as saw dust and rice husk were added during preparation of bed soils. Rice husk was more finely ground, compared to saw dust. The fine particles of the rice husk prevented their flow in a barrel of the expander. The mixed additives with paper sludges could be used to control the quantity of required nutrients for raising plants. That is, except for potassium and manganese, most of nutrients were decreased with adding the additives to paper sludge. The acidity of the paper sludges mixed with the saw dust or the rice husk was a little decreased with the increased amount of the additives. Differently from the bulk density of the paper sludges, the moisture content and the water absorption rate of the paper sludges were incremented with increasing the additives.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.15
• /
• pp.115-121
• /
• 1974

Artificial induction of nitrogen deficiency symptoms (leaf chlorosis) with two root respiratory inhibitors(DNP and Na$_2$S) was studied and regarded to be the same characteristic to red discoloration in rice var. Tongil seedling leaves as well as adult ones. Tongil(IR 667) was shown to be more nitrogen sensitive and have more distinctive appearance of the leaf discoloration than Punggwang(a native Japonica-type varity.) Conclusions were drawn from the present data that so-called red discoloration of Tongil under the natural field conditions is brought about either by insufficient nitrogen supply in soils or certain factors which may limit at any time the root absorption of nitrogen (low temperature, toxic gases or substances, poor drainage, around roots, etc.) in soils even with ample supply of it.

• Journal of Forest and Environmental Science
• /
• v.25 no.3
• /
• pp.167-175
• /
• 2009

An exploratory study was conducted in Juri Forest Range-2, a proposed biodiversity conservation area of Bangladesh to explore the present growing stock of tree, regeneration condition and status of non-timber forest products (NTFPs). This conservation area contains both natural and artificial plantation was selected by using multistage random sampling method. For determination of plot size and sampling methods, the quadrate size ($10m{\times}10m$) for tree stock measurement, ($2m{\times}2m$) for regeneration survey, ($20m{\times}20m$) for NTFPs survey was determined. Regarding tree stock survey, 14 species under eight families were found where Tectona grandis shows average number of stem/ha was 624 and basal area/ha was (10.36 $m^2/ha$) followed by Acacia auriculiformis (0.2 $m^2/ha$ and 637 stem/ha), Gmelina arborea (0.2 $m^2/ha$ and 600 stem/ha). In regeneration survey, 14 species were found belonging to 9 families where Alstonia scholaris shows highest (3,750) seedling per hectare. Regarding NTFPs, bamboo and cane are the most common resources. In last ten years, the total timber output was 1,28,596.14 cubic feet and total amount of revenue was 4,64,434 US$. The vacant area is 1,335.5 acre which contains 14% of total area. If this vacant area is planted with suitable species and take proper steps for appropriate management of this species it will be a good biologically diversified area.

• Journal of Aquaculture
• /
• v.12 no.1
• /
• pp.39-45
• /
• 1999

In order to obtain the basic biological data for artificial seedling production of sea cucumber, Stichopus japonicus, the influence of water temperature and air dry for spawning induction, egg development and larvae rearing was investigated during the period from April, 1995 through September, 1995. Spawning induction rate by the water temperature was 6.0~17.5% and air dry was responsed 1.4~4.0%. Number of eggs spawned of Stichopus japonicus were $50~500\times10^4$ individuals, the fertilization and hatching rate were ranged 84.0~96.0%, 71.4~84.6% respectively. The fertilized egg of Stichopus japonicus appeared mean diameter of $154{\mu}m$. At a constant water temperature of $23^{circ)C$, it become 4 tell stage from fertilization after 2 hours 10 minutes, hatching larvae after 14 hours half, auricularia larvae after 3 days, doliolaria larvare after 11 days and pentactula larvae after 15 days ready for settlement. The suitable food in the larvae reared for 17 days after fertilization were shown the best growth and survival in the larvae food of Chaetoceros calcitrans. Optimum density for larvae rearing were maintained of the larval density lower than 2 individuals/ml.

• Korean Journal of Microbiology
• /
• v.33 no.2
• /
• pp.105-110
• /
• 1997

Ustilago maydis strains (A-series and SH-series) containg virus or viral dsRNAs were artificially mated in corn seedling to generate 6 progeny strains, designated A23, A45, A21l, A31O, SH24 and SH61O. The dsRNA patterns of progeny strains were identical to those of the parental strains and there was no molecular exclusion mechanism among dsRNAs of parental strains. Virus particles were purified from 6 progeny strains and viral dsRNAs were analyzed on 5% PAGE. There was no mixed encapsidation between virus or dsRNAs of parental strains. Progeny strain SH6l4 produced toxin which inhibits the growth of SH9, SHIO and SH11. Likewise, toxins from A310 and SH24 inhibited growth of the SH11 strains. These results indicate that the presence of different types of dsRNA does not interfere the expression of toxin gene.

• Research in Plant Disease
• /
• v.12 no.2
• /
• pp.125-128
• /
• 2006

Downy mildew caused by Pseudoperonospora cubensis (Berkeley & Curtis) occurred on the cotyledon of gourd (Lagenaria leucantha cv. Sambokkkul) and scion of watermelon (cv. FR couple) in commercial nursery around Jinju city, Gyeongnam province in Korea in 2005 and 2006. The disease symptoms usually started with water-soaking lesions on cotyledon and then the infected leaves became withered and eventually died. The sporangia of the pathogen were one-celled, ovoid to ellipsoid in shape, pale grayish in color, and $20{\sim}32{\times}14{\sim}18{\mu}m$ in size. Sporangiophores were errect, branched, and $140{\sim}380{\times}4{\sim}8{\mu}m$ in size. Pathogenicity of the causal organism was proved according to artificial inoculations. Although the virulence of the causal fungus on the host plants was not strong, it produced typical symptoms. The causal organism was identified as Pseudoperonospora cubensis (Berkeley & Curtis) based on the mycological characteristics of the fungus and pathogenicity. This is the first report on downy mildew of watermelon caused by P. cubensis in Korea.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.37 no.3
• /
• pp.242-247
• /
• 2017

Humic acid (HA) is a complex organic matter found in the environments, especially in grassland soils with a high density. The bioactivity of HA to promote plant growth depends largely on its extraction sources. The quality-control of HA and the quality improvements via an artificial synthesis are thus challenging. We recently reported that a polymeric product from fungal laccase-mediated oxidation of catechol and vanillic acid (CAVA) displays a HA-like activity to enhance seed germination and salt stress tolerance in a model plant, Arabidopsis. Here, we examined whether HA or CAVA enhances the growth of Italian ryegrass seedling. Height and fresh weight of the plant with foliar application of HA or CAVA were bigger than those with only water. Interestingly, enhanced root developments were also observed in spite of the foliar treatments of HA or CAVA. Finally, we proved that HA or CAVA promotes the regrowth of Italian ryegrass after cutting. Collectively, CAVA acts as a HA mimic in Italian ryegrass cultivation, and both as a biostimulant enhanced the early growth and regrowth after cutting of Italian ryegrass, which could improve the productivity of forage crops.

• Journal of Forest and Environmental Science
• /
• v.37 no.4
• /
• pp.323-330
• /
• 2021

Zygotic embryo culture was performed to propagate evergreen oak, Quercus myrsinifolia, which has recalcitrant seeds and is difficult to propagate by cuttings. Zygotic embryos appeared in WPM medium after 14 days, and after 56 days, they developed into complete plants with cotyledons and roots. The medium suitable for zygotic embryo culture was 1/4 WPM medium, showing a shoot growth of 2.43 cm and root growth of 8.7 cm after 8 weeks of culture. As a result of investigating the effect of GA₃ on the growth of plants germinated from zygotic embryos through GA₃ treatment, the best growth was shown in 0.5 mg/l GA₃ treatment. The in vitro rooting and growth of IBA-treated zygotic embryo-derived plants were good in the 0.5 mg/l IBA treatment and rooting and shoot growth were not observed at higher concentrations. And the callus induction rate also increased as the concentration of IBA increased. Plants grown in vitro were transferred to a plastic pot containing artificial soil and acclimatized in a greenhouse for about 4 weeks, resulting in more than 90% survival. As a result of this study, the zygotic embryo culture method was confirmed to be effective for mass propagation of Q. myrsinifolia. The results of this study are expected to contribute significantly to the mass propagation of elite Q. myrsinifolia.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.31 no.1
• /
• pp.78-83
• /
• 1986

To obtain the information about the reasons why hulless barley varieties generally have poor germination and emergence rate in the field, hulled and hulless isogenic lines were bred and used. The germination rates of hulless isogenic lines were 4-6 percent lower than those of hulled lines at artificial precipitation treatment, and seriously dropped down at 5 day precipitation treatment. As the thresher rotation speeds up 600 to 1,000 rpm, the differences of germination rate were 10 percent in hulled, but 22 percent in hulless lines. Also emergence rates of hulless lines became seriously low at deep seeding. The emergence rates of hulless isogenic lines became low in the order of deep seeding, high speed thresher, and rain-fall. These results suggest that barley breeders especially for hulless varieties should plan their breeding programs to improve the emergence rate or seedling vigour in the field.