Influence of ß-Ionone in the Phytotoxicity of the Rhizome of Iris pallida Lam.

Iris pallida Lam., also known as Sweetie Iris, is a perennial ornamental and medicinal plant that produces a wide range of secondary metabolites. The Sweetie Iris was recently reported to have high allelopathic properties with the potential to be explored in sustainable weed management. This study aimed to identify and evaluate the contributions of compounds involved in the inhibitory effects of the rhizome of Sweetie Iris. High-performance liquid chromatography (HPLC) analysis was used to determine the content of ß-ionone in the rhizome of Sweetie Iris. The phytotoxicity of ß-ionone was evaluated on lettuce (Lactuca sativa L.) and other test plants. The content of ß-ionone in the crude extract of Sweetie Iris rhizome was found to be 20.0 mg g-1 by HPLC analysis. The phytotoxicity bioassay showed that ß-ionone had strong inhibitory activity on the growth of lettuce (Lactuca sativa L.) and the other test plants, including Taraxacum officinale, Stellaria media, Eleusine indica, Amaranthus hybridus, Vicia villosa, and Brassica napus. At a concentration of 23.0 µg mL-1, ß-ionone inhibited the growth of all test plant species treated. Therefore, ß-ionone is an active compound among the other allelopathic substances contained in the rhizome of Sweetie Iris.

Identification of Genomic Regions for Deep-Water Resistance in Rice for Efficient Weed Control with Reduced Herbicide Use.

Deep-water (DW) management in rice fields is a promising technique for efficient control of paddy weeds with reduced herbicide use. Maintaining a water depth of 10-20 cm for several weeks can largely suppress the weed growth, though it also inhibits rice growth because the DW management is usually initiated immediately after transplanting. Improving the DW resistance of rice during the initial growth stage is essential to avoid suppressing growth. In this study, we demonstrate a large genetic variation in the above-ground biomass (AGB) after the end of DW management among 165 temperate japonica varieties developed in Japan. Because the AGB closely correlated with plant length (PL) and tiller number (TN) at the early growth stage, we analyzed genomic regions associated with PL and TN by conducting a genome-wide association study. For PL, a major peak was detected on chromosome 3 (qPL3), which includes a gene encoding gibberellin biosynthesis, OsGA20ox1. The rice varieties with increased PL had a higher expression level of OsGA20ox1 as reported previously. For TN, a major peak was detected on chromosome 4 (qTN4), which includes NAL1 gene associated with leaf morphological development and panicle number. Although there was less difference in the expression level of NAL1 between genotypes, our findings suggest that an amino acid substitution in the exon region is responsible for the phenotypic changes. We also found that the rice varieties having alternative alleles of qPL3 and qTN4 showed significantly higher AGB than the varieties with the reference alleles. Our results suggest that OsGA20ox1 and NAL1 are promising genes for improving DW resistance in rice.

Mating Types of Ustilago esculenta Infecting Zizania latifolia Cultivars in Japan Are Biased towards MAT-2 and MAT-3.

Zizania latifolia cultivars infected by the endophytic fungus Ustilago esculenta develop an edible stem gall. Stem gall development varies among cultivars and individuals and may be affected by the strain of U. esculenta. To isolate haploids from two Z. latifolia cultivars in our paddy fields, Shirakawa and Ittenkou, we herein performed the sporadic isolation of U. esculenta strains from stem gall tissue, a PCR-based assessment of the mating type, and in vitro mating experiments. As a result, we obtained heterogametic strains of MAT-2 and MAT-3 as well as MAT-2, but not MAT-3, haploid strains. Another isolation method, in which we examined poorly growing small clusters of sporidia derived from teliospores, succeeded in isolating a MAT-3 haploid strain. We also identified the mating types of 10 U. esculenta strains collected as genetic resources from different areas in Japan. All strains, except for one MAT-1 haploid strain, were classified as MAT-2 haploid strains or heterogametic strains of MAT-2 and MAT-3. The isolated strains of MAT-1, MAT-2, and MAT-3 mated with each other to produce hyphae. Collectively, these results indicate that the mating types of U. esculenta infecting Z. latifolia cultivars in Japan are biased towards MAT-2 and MAT-3 and that U. esculenta populations in these Japanese cultivars may be characterized by the low isolation efficiency of the MAT-3 haploid.

Pyramiding of multiple strong-culm genes originating from indica and tropical japonica to the temperate japonica rice.

Severe lodging has recurrently occurred at strong typhoon's hitting in recent climate change. The identification of quantitative trait loci and their responsible genes associated with a strong culm and their pyramiding are important for developing high-yielding varieties with a superior lodging resistance. To evaluate the effects of four strong-culm genes on lodging resistance, the temperate japonica near isogenic line (NIL) with the introgressed SCM1 or SCM2 locus of the indica variety, Habataki and the other NIL with the introgeressed SCM3 or SCM4 locus of the tropical japonica variety, Chugoku 117 were developed. Then, we developed the pyramiding lines with double,triple and quadruple combinations derived from step-by-step crosses among NIL-SCM1-NIL-SCM4. Quadruple pyramiding line (NIL-SCM1 + 2 + 3 + 4) showed the largest culm diameter and the highest culm strength among the combinations and increased spikelet number due to the pleiotropic effects of these genes. Pyramiding of strong culm genes resulted in much increased culm thickness, culm strength and spikelet number due to their additive effect. SCM1 mainly contributed to enhance their pyramiding effect. These results in this study suggest the importance of identifying the combinations of superior alleles of strong culm genes among natural variation and pyramiding these genes for improving high-yielding varieties with a superior lodging resistance.

L-Canavanine, a Root Exudate From Hairy Vetch (Vicia villosa) Drastically Affecting the Soil Microbial Community and Metabolite Pathways.

L-Canavanine, a conditionally essential non-proteinogenic amino acid analog to L-arginine, plays important roles in cell division, wound healing, immune function, the release of hormones, and a precursor for the synthesis of nitric oxide (NO). In this report, we found that the L-canavanine is released into the soil from the roots of hairy vetch (Vicia villosa) and declines several weeks after growth, while it was absent in bulk proxy. Hairy vetch root was able to exudate L-canavanine in both pots and in vitro conditions in an agar-based medium. The content of the L-canavanine in pots and agar conditions was higher than the field condition. It was also observed that the addition of L-canavanine significantly altered the microbial community composition and diversity in soil. Firmicutes and Actinobacteria became more abundant in the soil after the application of L-canavanine. In contrast, Proteobacteria and Acidobacteria populations were decreased by higher L-canavanine concentration (500 nmol/g soil). Prediction of the soil metabolic pathways using PICRUSt2 estimated that the L-arginine degradation pathway was enriched 1.3-fold when L-canavanine was added to the soil. Results indicated that carbon metabolism-related pathways were altered and the degradation of nitrogen-rich compounds (i.e., amino acids) enriched. The findings of this research showed that secretion of the allelochemical L-canavanine from the root of hairy vetch may alter the soil microbial community and soil metabolite pathways to increase the survival chance of hairy vetch seedlings. This is the first report that L-canavanine acts as an allelochemical that affects the biodiversity of soil microbial community.

Evaluation of Growth, Yield, and Biochemical Attributes of Bitter Gourd (Momordica charantia L.) Cultivars under Karaj Conditions in Iran.

Vegetative and reproductive characteristics, fruit yield, and biochemical compounds of six bitter melon cultivars (Iranshahr, Mestisa, No. 486, Local Japanese, Isfahan, and Ilocano) were evaluated under Karaj conditions in Iran. The phytochemical properties of the cultivars were evaluated using both shade-dried and freeze-dried samples at three fruit developmental stages (unripe, semi-ripe, and ripe). There were significant differences in the vegetative and reproductive characteristics among cultivars, where cv. No. 486 was superior to most vegetative attributes. The fruit yield of cultivars varied from 2.98-5.22 kg/plant. The number of days to male and female flower appearance ranged from 19.00-25.33 and from 25-33 days, respectively. The leaf charantin content was in the range of 4.83-11.08 µg/g. Fruit charantin content varied with developmental stage, drying method, and cultivar. The highest charantin content (13.84 ± 3.55 µg/g) was observed at the semi-ripe fruit stage, and it was much higher in the freeze-dried samples than the shade-dried samples. Cultivar No. 486 had the highest (15.43 ± 2.4 µg/g) charantin content, whereas the lowest charantin content (8.51 ± 1.15 µg/g) was recorded in cultivar cv. Local Japanese. The highest total phenol content (25.17 ± 2.27 mg GAE/g) was recorded in freeze-dried samples of ripe fruits of cv. No. 486, whereas the lowest phenol content was detected in the shade-dried samples of semi-ripe fruits of Isfahan. cv. Flavonoid content was higher with the shade-drying method, irrespective of cultivar. In conclusion, considering the fruit yield and active biological compounds in the studied cultivars, cv. No. 486 should be grown commercially because of its higher yield and production of other secondary metabolites.

Metabolome Analysis Identified Okaramines in the Soybean Rhizosphere as a Legacy of Hairy Vetch.

Inter-organismal communications below ground, such as plant-microbe interactions in the rhizosphere, affect plant growth. Metabolites are shown to play important roles in biological communication, but there still remain a large number of metabolites in soil to be uncovered. Metabolomics, a technique for the comprehensive analysis of metabolites in samples, may uncover the molecules that intermediate these interactions. We conducted a multivariate analysis using liquid chromatography (LC)-mass spectrometry (MS)-based untargeted metabolomics in several soil samples and also targeted metabolome analysis for the identification of the candidate compounds in soil. We identified okaramine A, B, and C in the rhizosphere soil of hairy vetch. Okaramines are indole alkaloids first identified in soybean pulp (okara) inoculated with Penicillium simplicissimum AK-40 and are insecticidal. Okaramine B was detected in the rhizosphere from an open field growing hairy vetch. Okaramine B was also detected in both bulk and rhizosphere soils of soybean grown following hairy vetch, but not detected in soils of soybean without hairy vetch growth. These results suggested that okaramines might be involved in indirect defense of plants against insects. To our knowledge, this is the first report of okaramines in the natural environment. Untargeted and targeted metabolomics would be useful to uncover the chemistry of the rhizosphere.

Completely engaged three-dimensional mandibular gear-like structures in the adult horned beetles: reconsideration of bark-carving behaviors (Coleoptera, Scarabaeidae, Dynastinae).

Adult horned beetles (Coleoptera, Scarabaeidae, Dynastinae) such as Trypoxylusdichotomus (Linnaeus, 1771) exhibit bark-carving behaviors to feed on tree sap, in part by using small projections of the clypeus. However, in the present experiments, adult horned beetles (T.dichotomus and Dynasteshercules (Linnaeus, 1758)) used their mandibles and not the projections of the clypeus to carve bark. Our findings show the presence of completely engaged mandibular interlocking, gear-like surface structures in molar areas that guide mandible opening and closure, and lead to completely synchronous movements of adult horned beetle mandibles. Three-dimensional shapes of these mandibular gear-like structures are complex and remained in contact after the death of a beetle. Moreover, adult horned beetles often performed bark-carving behaviors using only the mandible of one side, suggesting that the primary role of the mandibular gear-like structure is to prevent breakage of the mandible by transmitting load from one mandible to the other. Among the 22 Dynastinae and 16 other beetle species examined (not Dynastinae), the gear-like structure was found in all the Dynastinae species and in no other species.

Precise estimation of genomic regions controlling lodging resistance using a set of reciprocal chromosome segment substitution lines in rice.

Severe lodging has occurred in many improved rice varieties after the recent strong typhoons in East and Southeast Asian countries. The indica variety Takanari possesses strong culm characteristics due to its large section modulus, which indicates culm thickness, whereas the japonica variety Koshihikari is subject to substantial bending stress due to its thick cortical fibre tissue. To detect quantitative trait loci (QTLs) for lodging resistance and to eliminate the effects of genetic background, we used reciprocal chromosome segment substitution lines (CSSLs) derived from a cross between Koshihikari and Takanari. The oppositional effects of QTLs for section modulus were confirmed in both genetic backgrounds on chromosomes 1, 5 and 6, suggesting that these QTLs are not affected by the genetic background and are controlled independently by a single factor. The candidate region of a QTL for section modulus included SD1. The section modulus of NIL-sd1 was lower than that of Koshihikari, whereas the section modulus of NIL-SD1 was higher than that of Takanari. This result indicated that those regions regulate the culm thickness. The reciprocal effects of the QTLs for cortical fibre tissue thickness were confirmed in both genetic backgrounds on chromosome 9 using CSSLs.

Increased lodging resistance in long-culm, low-lignin gh2 rice for improved feed and bioenergy production.

Lignin modification has been a breeding target for the improvements of forage digestibility and energy yields in forage and bioenergy crops, but decreased lignin levels are often accompanied by reduced lodging resistance. The rice mutant gold hull and internode2 (gh2) has been identified to be lignin deficient. GH2 has been mapped to the short arm of chromosome 2 and encodes cinnamyl-alcohol dehydrogenase (CAD). We developed a long-culm variety, 'Leaf Star', with superior lodging resistance and a gh phenotype similar to one of its parents, 'Chugoku 117'. The gh loci in Leaf Star and Chugoku 117 were localized to the same region of chromosome 2 as the gh2 mutant. Leaf Star had culms with low lignin concentrations due to a natural mutation in OsCAD2 that was not present in Chugoku 117. However, this variety had high culm strength due to its strong, thick culms. Additionally, this variety had a thick layer of cortical fiber tissue with well-developed secondary cell walls. Our results suggest that rice can be improved for forage and bioenergy production by combining superior lodging resistance, which can be obtained by introducing thick and stiff culm traits, with low lignin concentrations, which can be obtained using the gh2 variety.

Behavior of simetryn and thiobencarb in the plough zone of rice fields.

The behavior of simetryn and thiobencarb in flooded rice soil was investigated in a 2-year study. The concentrations of simetryn and thiobencarb were in the hundreds of µg kg−1 in the top soil layer (0­5 cm) and became significantly lower in tens of µg kg−1 in the deeper soil layers (5­10 and 10­15 cm). The half-lives of the two herbicides were also shorter (36 and 17 days for simetryn and thiobencarb, respectively) in the top soil layer, as they were most affected by environmental conditions, compared with corresponding values of 82 and 69 days in the 5­10 cm soil layer. Simetryn concentration was stable, while thiobencarb's half-life was 165 days in the 10­15 cm layer. About 35% of the applied mass of simetryn and thiobencarb were found in the rice soil compartment.

Suppressive effect of magnesium oxide materials on cadmium accumulation in winter wheat grain cultivated in a cadmium-contaminated paddy field under annual rice-wheat rotational cultivation.

The effectiveness of two kinds of magnesium oxide (MgO) materials, commercial MgO (2250 kg ha(-1)) and a material derived from MgO and magnesium silicate minerals named 'MgO-SH-A' (2250 and 4500 kg ha(-1)1), in suppression of uptake and accumulation of cadmium (Cd) into grain of winter wheat (Triticum aestivum L. cv. Ayahikari) was examined in a Cd-contaminated alluvial paddy field under annual rice-wheat rotational system. The MgO materials were mixed into the plough-layer soil only once prior to the preceding rice cultivation. Cadmium concentration in wheat grain produced from the non-amendment control exceeded the maximum limit of Cd in wheat grain adopted by FAO/WHO (0.2 mg kg(-1)). All of the treatments with the MgO materials significantly lowered plant available Cd fraction in the plough-layer soil. However, only the treatment with the commercial MgO at 2250 kg ha(-1) produced wheat grain whose Cd concentration was not only significantly lower than that from the control but also less than 0.2 mg kg(-1). It is suggested that the significant suppressive effect of the commercial MgO on Cd accumulation in wheat grain would be mainly attributed to its high soil neutralizing capacity as compared to that of MgO-SH-A.

Suppressive effects of magnesium oxide materials on cadmium uptake and accumulation into rice grains II: Suppression of cadmium uptake and accumulation into rice grains due to application of magnesium oxide materials.

The objective of this study is to assess the applicability of a commercial magnesium oxide (MgO) and a composite material containing MgO and natural minerals ('MgO-SH-A') as the soil amendments for suppression of cadmium (Cd) uptake and accumulation into rice grains. A cultivation experiment of rice plants (Oryza sativa L. cv. Kinuhikari) was conducted in an actual Cd-contaminated alluvial paddy field to evaluate the effectiveness of these materials. The 'plant available' fractions of Cd in the paddy soil significantly decreased by application of commercial MgO at 2250 kg ha(-1) or MgO-SH-A at 4500 kg ha(-1). These decreases would be primarily attributed to the increase in soil pH due to applications of the MgO materials because these soil Cd fractions were significantly negatively correlated with the soil pH. Even under a suppressive condition for Cd uptake by rice plants, i.e., continuous flooding of the paddy field around the heading stage, applications of these materials further reduced Cd concentration in brown rice as compared to that from the control. It was concluded that the two MgO materials examined would be effective in preventing Cd contamination of rice grains grown in Cd-polluted paddy fields.

The input-output balance of cadmium in a paddy field of Tokyo.

Field monitoring was practiced from 2001 to 2003 to evaluate the input (irrigation, atmospheric deposition, and fertilizer application) and the output (uptake and accumulation into the above-ground biomass of rice plants and leaching) of cadmium (Cd) in a contaminated paddy field in Tokyo. The cadmium concentrations of irrigated water, open-bulk precipitation, soil solution (leaching water), rice plants collected at the harvesting stage and the chemical fertilizer and the cow manure compost applied were determined. The Cd flux of each factor was calculated by multiplying the Cd concentration by the volume or mass of the media. The annual input-output balance of Cd in the paddy field in 2001 and 2002 was estimated to be -5.44 [corrected] g ha(-1) and -2.01 [corrected] g ha(-1), respectively, indicating the loss of Cd from the paddy field, although the losses accounted for only 0.24% [corrected] and 0.089% [corrected] of the total amount of Cd in the ploughed layer soil in 2001 and 2002, respectively. Among the factors involved, the input from fertilizers (including manure compost) and the output due to the uptake by rice plants played a major role in the balance. The former largely depended on the types and amounts of fertilizers applied, and the latter on the water management practices in the paddy field, such as flooding and drainage of the surface water.