Methods for Improving the Germination of Rhodotypos scandens (Thunb.) Makino Seeds through Endocarp Removal.

Rhodotypos scandens (Thunb.) Makino is known to have a seed dispersal that is thick and stony (endocarp + seeds) and has potential as a landscaping tree seed. In several Rosaceae species, seeds are covered with a hard endocarp, making the internal seeds water-impermeable and germination difficult. Here, we analyzed the morphoanatomical traits and germination properties of R. scandens seeds. To identify ideal seed propagation conditions, we immersed R. scandens seeds in sulfuric acid for varying durations and subjected them to phytohormone (gibberellic acid A3 and fluridone) and a cold stratification (CS) (5 °C) treatment after endocarp removal (ER). The R. scandens stony seeds did not increase in mass by ≥25.0%. Following ER, the seed mass increased by ≥50.0% with water absorption when compared to the initial dry mass. Seed surfaces showed damage and cracks through scarification after 1 h of immersion in sulfuric acid, failing to germinate. A combination of ER, phytohormone treatment, and CS improved seed germination compared to ER alone (26.0 ± 5.3%). Overall, R. scandens seeds showed a dispersal with a hard endocarp from the parent plant, and a pre-treatment with ER, phytohormones, and CS was required for effective seed propagation.

Dormancy-release and germination improvement of Korean bellflower (Campanula takesimana Nakai), a rare and endemic plant native to the Korean peninsula.

Korean bellflower (Campanula takesimana Nakai) is a rare and perennial herb with medicinal and ornamental values, is endemic to the Ulleung Island of Korea. In this study, we investigated the dormancy-release and germination characteristics of C. takesimana (Campanulaceae) seeds by subjecting them to varying temperatures (5, 10, 15, 20, and 25°C and diurnal/nocturnal temperatures of 15/6, 20/10, and 25/15°C), cold stratification periods (0, 4, 8, or 12 weeks at 5°C), and gibberellic acid (GA3) concentrations (0, 10, 100, or 1,000 mg·L-1 at 15/6°C and 25/15°C) to identify the ideal seed propagation conditions. The seeds were stimulated to germinate (at 25°C, 12-h photoperiod with fluorescent lamps at 40 ± 10 µmol∙m-2∙s-1) after cold stratification. To examine the germination characteristics, the seeds were tested for water imbibition and found to readily absorb water. The seeds exhibited underdeveloped embryos during dispersal, showed final germination of 37.00% ± 4.43 at 25°C and were not influenced by temperature. The seeds subjected to 0, 4, 8, or 12 weeks of cold stratification germinated at a success rate of 22.00% ± 4.76, 87.00% ± 6.80, 79.00% ± 2.52, and 77.00% ± 1.91, respectively. Additionally, the germination characteristics, which were based on final germination, mean germination time, and germination velocity (Timson index), were significantly greater in the seeds pretreated with 1,000 mg·L-1 GA3 at 25/15°C than in seeds pretreated with 0 mg·L-1 GA3. Overall, the seeds broke dormancy with GA3 and short-term cold stratification. Therefore, we concluded that C. takesimana seeds have non-deep, simple, morphophysiological dormancy, and pretreatment with cold stratification and GA3 is required for effective seed propagation.

The complete chloroplast genomes of Allium sacculiferum, A. thunbergii, and A. taquetii (Amaryllidaceae) from Korea.

The genus Allium comprises some of the most commonly consumed food crops worldwide. The chloroplast genomes of A. sacculiferum, A. thunbergii, and A. taquetii are 152,444, 153,459, and 154,056 bp circular molecular genomes, respectively. The annotation results revealed the presence of 132 (89 protein-coding, 35 tRNA, and eight rRNA), 132 (86 protein-coding, 38 tRNA, and eight rRNA), and 132 (86 protein-coding, 38 tRNA, and eight rRNA) genes with 36.78%, 36.83%, and 36.88% total GC content in each genome, respectively. The chloroplast genome of each Allium species contains an 81,254, 82,473, and 83,068 bp LSC region, an 18,176, 18,006, and 17,958 bp SSC region, and a pair of 26,507, 26,490, and 26,515 bp IR regions, respectively. Phylogenetic analysis based on the 21 complete chloroplast genomes indicates that A. sacculiferum is closely related to A. koreanum; A. thunbergii and A taquetii are closely related to A. hookeri. This study shows that the three Allium species are Korean crop wild relatives that may be used to develop new Allium varieties in the future.

Complete Genome Sequences of Two Apple Stem Grooving Viruses in Cnidium officinale in Korea.

We determined the whole-genome sequences of two apple stem grooving viruses (ASGV) detected in infected Cnidium officinale plants. The analyzed ASGV genomes were 6,494 nucleotides long and encoded two overlapping open reading frames. Phylogenetic analysis revealed the two ASGV isolates to be most closely related to the ASGV isolate Xinjiang-3.

Non-Deep Simple Morphophysiological Dormancy and Germination Characteristics of Gentiana triflora var. japonica (Kusn.) H. Hara (Gentianaceae), a Rare Perennial Herb in Korea.

This study investigated the kind of seed dormancy and seed germination of Gentiana triflora var. japonica (Kusn.) H. Hara for developing a seed propagation method. The seeds were collected in October 2020 from plants at Mt. Sobaeksan, Korea. In a water imbibition experiment, seed weights increased by >101.9% of their initial masses over 12 h. Effects of incubation temperature (5, 15, 20, 25, 15/6, or 25/15 °C), cold stratification period (5 °C; 0, 4, 8, or 12 weeks), and gibberellic acid (GA3; 0, 10, 100, or 1000 mg∙L-1) and potassium nitrate treatment (KNO3; 0, 1000, 2000, or 4000 mg∙L-1) on seed germination were investigated to characterize seed dormancy. These seeds exhibited underdeveloped embryos during seed dispersal. The seeds failed to reach the final germination of 15.0% after treatment at 5, 15, 20, 25, 15/6, or 25/15 °C. After cold stratification for 8 weeks, the germination increased dramatically by >90.0% compared to that at 0 weeks. After the GA3 treatment, the germination reached >80.0% within 5 days. The final germination was 90.0% in the 100 mg∙L-1 GA3 treatment group. However, the KNO3 treatment had no effect on seed germination. Therefore, the G. triflora var. japonica seeds exhibited non-deep simple morphophysiological dormancy.

Improving Restoration Efficiency by Modeling Optimal Sowing Periods: A Case Study of Two Native Plants and Restoration of a Site.

Efficient ecological restoration techniques are urgently required to minimize seed consumption and labor requirements. Here, we determined the optimal sowing period for two native species, Agastache rugosa (Korean mint) and Astilbe rubra (False goat's beard), toward their use for ecological restoration of Mt. Gariwang, a site damaged by the 2018 PyeongChang Winter Olympics' activities. We investigated the effects of daily mean temperature (DMT) and daily temperature range (DTR) on seed germination percentage, which decreased for both species with decreasing DTR and was optimal at a DMT of 25 °C and 17.5 °C for A. rugosa and A. rubra, respectively. We developed a single multiple regression equation that evaluated the effects of DMT and DTR simultaneously and determined the temperature scores when the germination percentage reached 85%. We applied the developed multiple regression equation by analyzing the temperature data of the restoration site. In addition, precipitation data analysis was added to set the optimal sowing period. As a result, the optimal sowing period for the two species was determined from May 21 to the end of May. This makes it possible to minimize seed consumption and labor requirements when sowing seeds. The model developed herein will be useful not only to guide the ecological restoration of Mt. Gariwang, but also for other regions using site-specific temperature data.

First Complete Genome Sequence of Barley Virus G Identified from Proso Millet (Panicum miliaceum) in South Korea.

The complete genome sequence of an Uiseong isolate of barley virus G (BVG) on proso millet plants in a field in South Korea was determined by RNA sequencing and Sanger sequencing. To our knowledge, this is the first complete genome sequence report of BVG infecting proso millet in South Korea.

Development of multiplex rt-PCR for simultaneous detection of garlic viruses and the incidence of garlic viral disease in garlic genetic resources.

Garlic generally becomes coinfected with several types of viruses belonging to the Potyvirus, Carlavirus, and Allexivirus genera. These viruses produce characteristically similar symptoms, they cannot be easily identified by electron microscopy (EM) or immunological detection methods, and they are currently widespread around the world, thereby affecting crop yields and crop quality adversely. For the early and reliable detection of garlic viruses, virus-specific sets of primers, including species-specific and genus-specific primers were designed. To effectively detect the twelve different types of garlic viruses, primer mixtures were tested and divided into two independent sets for multiplex polymerase chain reaction (PCR). The multiplex PCR assays were able to detect specific targets up to the similar dilution series with monoplex reverse transcription (RT)-PCR. Seventy-two field samples collected by the Gyeongbuk Agricultural Technology Administration were analyzed by multiplex RT-PCR. All seventy two samples were infected with at least one virus, and the coinfection rate was 78%. We conclude that the simultaneous detection system developed in this study can effectively detect and differentiate mixed viral infections in garlic.

Development of the large-scale oligonucleotide chip for the diagnosis of plant viruses and its practical use.

A large-scale oligonucleotide (LSON) chip was developed for the detection of the plant viruses with known genetic information. The LSON chip contains two sets of 3,978 probes for 538 species of targets including plant viruses, satellite RNAs and viroids. A hundred forty thousand probes, consisting of isolate-, species- and genus-specific probes respectively, are designed from 20,000 of independent nucleotide sequence of plant viruses. Based on the economic importance, the amount of genome information, and the number of strains and/or isolates, one to fifty-one probes for each target virus are selected and spotted on the chip. The standard and field samples for the analysis of the LSON chip have been prepared and tested by RT-PCR. The probe's specific and/or nonspecific reaction patterns by LSON chip allow us to diagnose the unidentified viruses. Thus, the LSON chip in this study could be highly useful for the detection of unexpected plant viruses, the monitoring of emerging viruses and the fluctuation of the population of major viruses in each plant.

Biological and molecular characterization of Soybean yellow common mosaic virus, a new species in the genus Sobemovirus.

A novel soybean-infecting sobemovirus termed Soybean yellow common mosaic virus (SYCMV) was characterized. The virus has a single, positive-strand RNA genome of 4152 nucleotides. The virus contains four putative open reading frames encoding P1 (78-566 nt), polyprotein ORF2a (524-2248 nt), polymerase domain ORF2b (1852-3417 nt), and CP (3227-4030 nt). The entire nucleotide sequence of SYCMV showed 31.2-71.3% nucleotide identity with the previously known eleven species of sobemovirus. In host range analysis of SYCMV, in which twenty one species and three different Nicotiana tabacum cultivars belonging to seven families were inoculated with the virus, SYCMV had a narrow host range, infecting only Glycine max and G. soja. Based on the obtained sequence, full-length clones of SYCMV were constructed. Symptoms produced by inoculation with clones were indistinguishable from those produced by inoculation with sap from symptomatic plants. Viral RNA accumulation of SYCMV was detected in the upper leaves by Northern blotting. This indicated that full-length clones of SYCMV were sufficient to produce disease symptoms. Genomic organization, the predicted amino acid sequence, and phylogenetic analyses with known sobemoviruses confirmed the assignment of SYCMV as a new member of the genus Sobemovirus.