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Monochoria vaginalis (Burm. f.) C. Presl is a dominant weed in paddy rice cultivation, significantly threatening productivity and farming sustainability. In Subang, Indonesia, synthetic auxin and acetolactate synthase (ALS) inhibitors are commonly used to control M. vaginalis. However, farmers have currently reported declining efficacy of these herbicides. Therefore, this study aimed to confirm the resistance of M. vaginalis to the early post-emergence application of synthetic auxin and ALS inhibitors. Plant bioassays were conducted using the pot test method to determine resistance level. Herbicides were applied 2 weeks after planting M. vaginalis at 0.25, 0.5, 1.0, 2.0, 4.0, and 8.0 times the recommended dose, and untreated plants as control. Herbicides tested were 2,4-D, bensulfuron-methyl, bispyribac sodium, penoxulam, and sulfentrazone. The results obtained based on resistance index values (RI) showed that M. vaginalis populations from Kediri and Gandasari, Subang, had moderately to high resistance to 2,4-D (RI: 8.15 and 13.0) and bensulfuron-methyl (RI: 205.61 and 21.80). Weed was moderately resistant to bispyribac sodium (RI of Kediri biotype: 8.79) and had low to moderate resistance to penoxulam herbicides (RI: 8.94 and 3.56). In contrast, M. vaginalis-resistant biotypes remained susceptible to sulfentrazone (protoporphyrinogen oxidase/PPO inhibitors) herbicide. A significant increase in GR50 was observed between 28 and 56 days after herbicide application, signifying enhanced regrowth. The resistance of M. vaginalis to synthetic auxin and ALS inhibitors presents the need for farmers to consider alternative herbicides, such as PPO inhibitors, to prevent the development of resistant weeds.

We evaluated the allelopathic potential of allelochemicals present in the swamp rice (Oryza sativa L.) varieties. The effects of 10-swamp rice varieties (Inpara 1, Inpara 2, Inpara 3, Inpara 4, Inpara 5, Inpara 6, Inpara 7, Inpara 8 Agritan, Inpara 9 Agritan and Inpara 10 BLB) were studied on two weeds (Echinochloa crus-galli and Monochoria vaginalis). The allelochemicals released as root exudates from these swamp rice varieties were quantified in root and soil samples with high-performance liquid chromatography (HPLC). The results showed that the swamp rice varieties differed in inhibiting the growth of E. crus-galli and M. vaginalis. The variety Inpara 7 caused maximum growth suppression of E. crus-galli (23.9 %) and M. vaginalis (29.3 %) than other varieties. Furthermore, Inpara 3, 4, 6, 7 and 8 varieties also suppressed the growth of test weeds. HPLC analysis indicated that the allelochemicals concentration was significantly higher in roots than in soil, depending on the variety. The p-hydroxybenzoic acid content in the roots was higher than ferulic and p-coumaric acids, but the release of p-coumaric acid contents into the soil was higher than other compounds. The Inpara 3 roots contained higher contents of ferulic and pcoumaric acids than other varieties, while the highest p-hydroxybenzoic content was found in Inpara 2. The ferulic and p-coumaric acids were significantly correlated with weed growth variables. These compounds may play important roles in regulating rice allelopathy. [ABSTRACT FROM AUTHOR]

Monochoria vaginalis is one of the dominant weeds in rice crop fields of Central Java and East Java Indonesia and it failed to be controlled by herbicides with the active ingredient bensulfuron-methyl. The research was carried out using split plotdesign with the dosage of bensulfuron-methyl as a main plot (0, 80, 160, 320, 640 and 1280 g a.i. ha-1 ) and Monochoria vaginalis from 5 areas as a subplot. The research was done from January until August 2019. Resistance ratio test of Monochoria vaginalis was performed using the whole plant pot test method. Results showed that Monochoria vaginalis originating from Kedaton, Tambakrejo, and Plumpang villages Indonesia was confirmed to have developed into weeds resistant to the methyl bensulfuron herbicide.

Rice bran application is practically used by Japanese organic rice farmers as a common measure in controlling Monochoria vaginalis, a known weed in organic rice production. To elucidate the inhibitory mechanisms of rice bran application on M. vaginalis germination, we focused on volatile fatty acids (VFAs) and aromatic carboxylic acids (ACAs) as organic acids produced through rice bran decomposition in the soil, which can possibly suppress M. vaginalis germination. Both solo solutions of 1 mM VFAs (propionic or isobutyric acid) and 0.2 mM ACAs (3-phenylpropionic or 4-phenylbutyric acid) exhibited M. vaginalis germination suppression, especially at pH 4.6, the lowest pH tested. In the 0.5–3 mM VFA solutions at pH 4.6, germination was strongly suppressed in the order of isobutyric > propionic > butyric > acetic acid. With the 0.05–0.2 mM ACA solutions at pH 4.6, the germination was strongly suppressed in the order of 3-phenylpropionic > 4-phenylbutyric > 2-phenylpropionic acid. Benzoic acid did not exhibit significant germination suppression. The solutions of 0.5 mM VFAs and 0.05 mM ACAs exhibited no suppression when applied separately; however, the certain mixture of a VFA and an ACA at the aforementioned concentration, for example, 0.5 mM isobutyric acid and 0.05 mM 3-phenylpropionic acid, exhibited significant germination suppression. These results showed the several combinations of VFAs and ACAs at even non-effective concentrations synergistically suppressed M. vaginalis germination. Abbreviations:2PPA: 2-phenylpropionic acid; 3PPA: 3-phenylpropionic acid; 4PBA: 4-phenylbutyric acid; ACA: aromatic carboxylic acid; EC: electrical conductivity; M. vaginalis: Monochoria vaginalis; VFA: volatile fatty acid

In organic paddy fields, one of the toughest weeds to control is Monochoria vaginalis (Burm. f.) Kunth. The application of fresh rice (Oryza sativa L.) bran to soil suppresses the germination of this weed. In stark contrast, the scarcely decomposable component of this material stimulates the germination. This review focuses on the elucidation of these conflicting traits. One of the chemical factors for the suppression is toxic substances such as organic acids. In addition, rice bran application enhances the piling of small soil particles by tubificids on the soil surface. This layer acts as a physical factor that slows germination, presumably because its fine grains prevent light from reaching the seed. The newly accumulated soil with small particle was sampled for the analysis of the settled soil volume in water (SSVW). This value corresponds to the mud volume in water per dry weight. The electrical conductivity (EC) of the soil solution and the SSVW of the soil surface are useful indicators to evaluate the chemical and physical factors that control germination, respectively. EC and SSVW have been traced in paddy fields where rice bran was applied. The chemical and physical factors were active during the earlier and latter halves of the month after transplanting, respectively. These factors worked in a complementary manner. Paddy soil is typically equipped with the ability to reduce oxygen (O2). This trait enhances the number of M. vaginalis plants because hypoxic conditions are preferable for germination. Anaerobic soil conditions are not required for the expression of O2-reducing power. A long-term application of rice bran might intensify this power because a scarcely decomposable component of rice bran contains a significant amount of O2-reducing substances. The presence of conflicting factors that suppress and enhance germination might destabilize the efficacy of the rice bran. [ABSTRACT FROM AUTHOR]

Organic paddy rice (Oryza sativa L.) cultivation can be negatively impacted because of the weeds growth like Monochoria vaginalis. Although the rice bran application is useful in combating weed, its performance is not consistent. In this study, laboratory experiments were conducted to elucidate the effects of rice bran on the suppression and promotion of germination of M. vaginalis. Suppression experiments involved incubating mixtures of flooded soil and rice bran. This was followed by a germination experiment in the collected soil solutions. A negative and significant correlation was observed between germination and the electric conductivity (EC) of the solution. None of the seeds germinated when the EC of the Gray Lowland soil was over 130 mS m−1. Conversely, the seeds in the Andosols’ solution germinated even when EC was over 130 mS m−1. Thus, the solutions of the Andosols had different mechanisms of suppression than the Gray Lowland soils. To understand the promotion of germination, air-dried soil was prepared after the flooded incubation of rice bran and soil mixture, simulating a long-term application of rice bran. Germination was analyzed in a filtrate of the mixture of air-dried soil and distilled water. The addition of rice bran significantly promoted germination. There was a negative and significant correlation between germination and dissolved oxygen (DO) suggesting that hardly decomposable components like antioxidants in rice bran decreased O2 and stimulated germination because the seeds of M. vaginalis require very little O2 for germination.

Monochoria vaginalis is one of the dominant weeds in rice crop fields of Central Java and East Java Indonesia and it failed to be controlled by herbicides with the active ingredient bensulfuron-methyl. The research was carried out using split plotdesign with the dosage of bensulfuron-methyl as a main plot (0, 80, 160, 320, 640 and 1280 g a.i. ha-1) and Monochoria vaginalis from 5 areas as a subplot. The research was done from January until August 2019. Resistance ratio test of Monochoria vaginalis was performed using the whole plant pot test method. Results showed that Monochoria vaginalis originating from Kedaton, Tambakrejo, and Plumpang villages Indonesia was confirmed to have developed into weeds resistant to the methyl bensulfuron herbicide. [ABSTRACT FROM AUTHOR]

Summary: The evolution of herbicide resistance in weeds is an example of parallel evolution, through which genes encoding herbicide target proteins are repeatedly represented as evolutionary targets. The number of herbicide target‐site genes differs among species, and little is known regarding the effects of duplicate gene copies on the evolution of herbicide resistance.We investigated the evolution of herbicide resistance in Monochoria vaginalis, which carries five copies of sulfonylurea target‐site acetolactate synthase (ALS) genes. Suspected resistant populations collected across Japan were investigated for herbicide sensitivity and ALS gene sequences, followed by functional characterization and ALS gene expression analysis.We identified over 60 resistant populations, all of which carried resistance‐conferring amino acid substitutions exclusively in MvALS1 or MvALS3. All MvALS4 alleles carried a loss‐of‐function mutation. Although the enzymatic properties of ALS encoded by these genes were not markedly different, the expression of MvALS1 and MvALS3 was prominently higher among all ALS genes.The higher expression of MvALS1 and MvALS3 is the driving force of the biased representation of genes during the evolution of herbicide resistance in M. vaginalis. Our findings highlight that gene expression is a key factor in creating evolutionary hotspots. [ABSTRACT FROM AUTHOR]

Rice bran application is practically used by Japanese organic rice farmers as a common measure in controlling Monochoria vaginalis, a known weed in organic rice production. To elucidate the inhibitory mechanisms of rice bran application on M. vaginalis germination, we focused on volatile fatty acids (VFAs) and aromatic carboxylic acids (ACAs) as organic acids produced through rice bran decomposition in the soil, which can possibly suppress M. vaginalis germination. Both solo solutions of 1 mM VFAs (propionic or isobutyric acid) and 0.2 mM ACAs (3-phenylpropionic or 4-phenylbutyric acid) exhibited M. vaginalis germination suppression, especially at pH 4.6, the lowest pH tested. In the 0.5–3 mM VFA solutions at pH 4.6, germination was strongly suppressed in the order of isobutyric > propionic > butyric > acetic acid. With the 0.05–0.2 mM ACA solutions at pH 4.6, the germination was strongly suppressed in the order of 3-phenylpropionic > 4-phenylbutyric > 2-phenylpropionic acid. Benzoic acid did not exhibit significant germination suppression. The solutions of 0.5 mM VFAs and 0.05 mM ACAs exhibited no suppression when applied separately; however, the certain mixture of a VFA and an ACA at the aforementioned concentration, for example, 0.5 mM isobutyric acid and 0.05 mM 3-phenylpropionic acid, exhibited significant germination suppression. These results showed the several combinations of VFAs and ACAs at even non-effective concentrations synergistically suppressed M. vaginalis germination. Abbreviations:2PPA: 2-phenylpropionic acid; 3PPA: 3-phenylpropionic acid; 4PBA: 4-phenylbutyric acid; ACA: aromatic carboxylic acid; EC: electrical conductivity; M. vaginalis: Monochoria vaginalis; VFA: volatile fatty acid [ABSTRACT FROM AUTHOR]

Organic paddy rice (Oryza sativa L.) cultivation can be negatively impacted because of the weeds growth like Monochoria vaginalis. Although the rice bran application is useful in combating weed, its performance is not consistent. In this study, laboratory experiments were conducted to elucidate the effects of rice bran on the suppression and promotion of germination of M. vaginalis. Suppression experiments involved incubating mixtures of flooded soil and rice bran. This was followed by a germination experiment in the collected soil solutions. A negative and significant correlation was observed between germination and the electric conductivity (EC) of the solution. None of the seeds germinated when the EC of the Gray Lowland soil was over 130 mS m−1. Conversely, the seeds in the Andosols' solution germinated even when EC was over 130 mS m−1. Thus, the solutions of the Andosols had different mechanisms of suppression than the Gray Lowland soils. To understand the promotion of germination, air-dried soil was prepared after the flooded incubation of rice bran and soil mixture, simulating a long-term application of rice bran. Germination was analyzed in a filtrate of the mixture of air-dried soil and distilled water. The addition of rice bran significantly promoted germination. There was a negative and significant correlation between germination and dissolved oxygen (DO) suggesting that hardly decomposable components like antioxidants in rice bran decreased O2 and stimulated germination because the seeds of M. vaginalis require very little O2 for germination. [ABSTRACT FROM AUTHOR]

Monochoria vaginalis (Burm. f.) C. Presl, belonging to the family Pontederiaceae, is an aquatic herbaceous plant, native to temperate and tropical Asia. The species often occurs in paddy fields as a noxious weed in East Asia, and in the USA, and causes a significant reduction in rice production. The objective of the present research was the evaluation of the resistance levels of M. vaginalis against three chemical groups of acetolactate synthase (ALS)-inhibitor herbicides and other two different groups of herbicides, and the investigation of the mutations in the ALS gene of the resistant biotype of M. vaginalis. Herbicide dose–response experiments showed that the resistant biotype of M. vaginalis was highly resistant to bensulfuron-methyl, moderately resistant to bispyribac-sodium, had low resistance to penoxsulam and 2,4-D dimethyl ammonium, and was susceptible to sulfentrazone. The nucleotide sequences of the ALS gene of resistant and susceptible biotypes showed 14 base substitutions, which caused two amino acid substitutions: Val-143-Ile and Val-148-Ile. It is the first report of the substitutions of amino acids Val-143-Ile and Val-148-Ile in ALS protein. Those mutations may give different resistance spectra against three ALS-inhibitor herbicides: bensulfuron-methyl, bispyribac-sodium, and penoxsulam. Further research is needed to elucidate the molecular basis of target-site resistance mechanisms such as the transformation of the ALS gene of M. vaginalis. It is also necessary to evaluate herbicide mixtures and/or the rotation of herbicide sites of action to control the resistant biotype of M. vaginalis.

We investigated the effect of poultry manure (PM) on the occurrence and early growth of Monochoria vaginalis in relation to soil solution electrical conductivity (SSEC). PM was applied at rates corresponding to 0 g of nitrogen (N) m−2 (PM-0), 1 g N m−2 (PM-1), 3 g N m−2 (PM-3), and 5 g N m−2 (PM-5). At 7 d post-seeding, the soil solution was sampled to measure EC, and also the emergence and growth of M. vaginalis were evaluated. The emergence rate of M. vaginalis decreased with increasing application rate of PM and SSEC. SSEC was significantly negatively correlated with the emergence rate of M. vaginalis seedlings. The average leaf number and length of M. vaginalis did not differ between PM-0, PM-1, and PM-3, but were significantly lower in PM-5. In summary, PM would allow to better control the emergence and early growth of M. vaginalis.

Field experiments were conducted to analyze the relationship between the settled soil volume in water (SSVW) and the growth of Monochoria vaginalis (Burm. f.) Kunth under organic farming conditions. SSVW corresponds to the mud volume per dry matter weight. Soil was sampled from the superficial layer of the topsoil (

Growth of the weed Monochoria vaginalis (Burm. f.) Kunth under the conditions of organic rice production is a serious problem. The reason for the growth of M. vaginalis being dominant, especially in organic rice production, is not fully understood. In this study, laboratory experiments were conducted to analyze soil and seed factors in relation to the promotion of germination. (1) After incubation of flooded soil with or without the addition of rice bran (0.3%, 0.6%, and 0.9% in an air-dried soil basis), soil solutions were recovered and seeds of M. vaginalis were incubated in the soil solutions. Germination in the soils solutions without and with 0.3% rice bran was greater than that in distilled water. However, germination was suppressed in the presence of 0.6% and 0.9% of rice bran. These findings indicate that the solution from the soils with rice bran has different effects that may either increase or decrease germination. (2) A mixture of air-dried soil and distilled water was filtered to obtain a soil solution. Seeds were incubated in the soil solution (same as above). Environmental and physiological factors affected germination: exposure of seeds to light was an environmental factor and high germination activity and shallow dormancy of seed were physiological. The recovered soil solution promoted germination when these factors were not optimized. (3) There was a negative and significant correlation between dissolved oxygen (DO) in the soil solution and germination, indicating that a low content of DO was a promotive factor for germination. (4) Based on an experiment using pH buffers, germination increased with decrease in pH of soil solution, as long as the pH ranged from 4.0 to 7.0. This finding indicates that pH is also a factor that promotes germination. [ABSTRACT FROM AUTHOR]

The genus Monochoria is represented in Sri Lanka by only two species, M. hastata and M. vaginalis. Of the two species M. vaginalis exhibits a high morphological diversity. A morphometric analysis was performed on the Sri Lankan members of the genus Monochoria to evaluate the morphological diversity exhibited by comparing 34 vegetative, anatomical and reproductive characters. Both cluster and principal coordinate analyses resulted in four clusters of which one corresponded to M. hastata, while M. vaginalis was divided into three phenetic groups indicating that the Sri Lankan M. vaginalis is a species complex involving more than one taxon. The length ratio of the lower spathe petiole to inflorescence stalk was identified as an informative character in delimiting the phenetic groups, a character that has not been considered before. Further, the occurrence of sub-palisade cavities that are filled with a red colored liquid in the leaves of two phenetic groups was a novel character for the genus as well as the family Pontederiaceae. [ABSTRACT FROM AUTHOR]

We investigated the effect of poultry manure (PM) on the occurrence and early growth ofMonochoria vaginalisin relation to soil solution electrical conductivity (SSEC). PM was applied at rates corresponding to 0 g of nitrogen (N) m−2(PM-0), 1 g N m−2(PM-1), 3 g N m−2(PM-3), and 5 g N m−2(PM-5). At 7 d post-seeding, the soil solution was sampled to measure EC, and also the emergence and growth ofM. vaginaliswere evaluated. The emergence rate ofM.vaginalisdecreased with increasing application rate of PM and SSEC. SSEC was significantly negatively correlated with the emergence rate ofM. vaginalisseedlings. The average leaf number and length ofM.vaginalisdid not differ between PM-0, PM-1, and PM-3, but were significantly lower in PM-5. In summary, PM would allow to better control the emergence and early growth ofM. vaginalis. [ABSTRACT FROM PUBLISHER]

The primary challenge in organic rice farming in Japan and other Asian countries is to control Monochoria vaginalis, one of the most common and troublesome broadleaved weeds. Azolla is a genus of floating aquatic ferns, used for many centuries as a green manure in traditional rice production. Loach ( Misgurnus anguillicaudatus) is a freshwater fish that was once widely spread in Asian rice paddies, but has disappeared in modern conventional rice paddies due to use of synthetic agrichemicals. The objective of this study was to assess the effects of individual and combined use of Azolla filiculoides and loach to suppress M. vaginalis emergence and increase rice yield in organic rice farming. This study was designed with four treatments-control (with neither Azolla nor loach), Azolla ( Azolla alone), loach (loach alone), and Az + Lo (combined Azolla and loach)-with three replications each. The results showed a partial suppression of M. vaginalis and improved rice yield with Azolla and loach. The combined use of Azolla and loach had more positive effect on weed suppression and 131 % increase in rice yield over the control treatment. This study indicated that combined use of Azolla and loach as a valuable approach in organic rice farming, especially in organically farmed rice paddies with high densities of M. vaginalis seeds. This combined use of Azolla and loach provides dual benefit of weed control and N supply without the use of synthetic N fertilizer. [ABSTRACT FROM AUTHOR]

The seeds of Monochoria vaginalis require light to germinate. However, they are able to germinate in darkness in the presence of rice hulls. The mechanism of this phenomenon was investigated in this study, in which only the unsterilized seeds of Monochoria were induced to germinate by the presence of a rice hull extract. The rice hull extract was able to be replaced by either a mixture of amino acids and phosphate or a yeast extract. The culture media in which germination was observed always showed turbidity, indicating the propagation of bacteria, which were identified as Bacillus sp., Pedobacter sp., Pantoea sp. and Sphingomonas sp. Treatment with the individual bacterial species or combinations of these bacteria induced Monochoria seed germination when added to the media containing the rice hull extract. It was concluded that the rice hull extract accelerates the propagation of bacteria, which in turn digest the seed coat of Monochoria, facilitating its germination. [ABSTRACT FROM AUTHOR]

Monochoria vaginalis is an herbaceous medicinal plant used to treat, liver problems India. Acetaminophen is a commonly used analgesic and antipyretic agent which, at high doses, causes liver and kidney necrosis in man and animals. The aim of the present study is to evaluate phytoconstituents and investigate the nephroprotective & antioxidant activities of the ethanol extract of Monochoria vaginalis on acetaminophen induced toxicity in rats. Phytoconstituents like n-hexadecanoic acid, 3-methyl- acetate-1-butanol, 1,1,3-triethoxy- propane, Z,Z,Z-1,4,6,9 - nonadecatetraene, undecanoic acid, 3-trifluoroacetoxy penta decane and 4-ethyl-5-octyl-2,2-bis (trifluoromethyl) - cis-1,3-dioxalone were identified from ethanol extract of Monochoria vaginalis by using a gas chromatograph-mass spectrograph (GC MS). Biochemical studies show that there is an increase in the levels of serum urea and creatinine along with an increase in the body weight and reduction in the levels of uric acid in acetaminophen induced groups. These values are retrieved significantly by treatment with Monochoria vaginalis extracts at two different doses. The antioxidant studies reveal that the levels of renal SOD, CAT, GSH and GPx in the APAP treated animals are increased significantly along with a reduced MDA content in ethanol extract of Monochoria vaginalis treated groups. Apart from these, histopathological changes also reveal the protective nature of the Monochoria vaginalis extract against acetaminophen induced necrotic damage of renal tissues. In conclusion, these data suggest that the ethanol extract of Monochoria vaginalis can prevent renal damage from APAP induced nephrotoxicity in rats and it is likely to be mediated through active phytoconstituents and its antioxidant activities. [ABSTRACT FROM AUTHOR]

Abstract: Acetolactate synthase (ALS) genes from Monochoria vaginalis resistant (R) and susceptible (S) biotypes against ALS inhibitors found in Korea revealed a single amino acid substitution of Proline (CCT), at 169th position based on the M. vaginalis ALS sequence numbering, to serine (TCT) in conserved domain A of the gene (equal to the proline 197 in Arabidopsis thaliana ALS gene sequence). A. thaliana plants transformed with the single mutated (Pro169 to Ser) M. vaginalis ALS gene (including transit signal peptide) showed cross-resistance patterns to ALS-inhibiting herbicides, like as sulfonylurea-herbicide bensulfuron methyl (R/S factor of 9.5), imidazolinone-herbicide imazapyr (R/S factor of 5.1), and triazolopyrimidine-herbicide flumetsulam (R/S factor of 17.6) when measuring hypocotyls’ length of A. thaliana. The ALS activity from the transgenic A. thaliana plants confirmed the cross-resistance pattern to these herbicides like as R/S factor of 8.3 to bensulfuron methyl, 2.3 to imazapyr, and 13.2 to flumetsulam. [Copyright &y& Elsevier]

Abstract: All living organisms spontaneously generate ultraweak photon emissions, which originate from biochemical reactions in cells. Current research uses the ultraweak photon emission from organisms as a novel indicator in nondestructive analyses of an organisms living state. This study indicates that ultraweak photon emissions from Monochoria vaginalis are different between resistant biotypes (R) to sulfonylurea (SU) and susceptible biotypes (S). In SU-R biotypes, distinct increases in photon emissions were observed, but there was little increase in SU-S biotypes. In addition, photon emissions from the resistant biotypes of M. vaginalis were suppressed by treatment with P450 inhibitors. This suggests that cytochrome P450 monooxygenase, which plays a crucial role in the metabolic detoxification of SUs, could be associated with the generation of ultraweak photon emissions. Ultraweak photon emissions have a potential use in a novel diagnosis system as an indicator in a nondestructive testing of weeds resistant to SUs. [Copyright &y& Elsevier]

Monochoria vaginalis (Burm. f.) C. Presl, belonging to the family Pontederiaceae, is an aquatic herbaceous plant, native to temperate and tropical Asia. The species often occurs in paddy fields as a noxious weed in East Asia, and in the USA, and causes a significant reduction in rice production. The objective of the present research was the evaluation of the resistance levels of M. vaginalis against three chemical groups of acetolactate synthase (ALS)-inhibitor herbicides and other two different groups of herbicides, and the investigation of the mutations in the ALS gene of the resistant biotype of M. vaginalis. Herbicide dose–response experiments showed that the resistant biotype of M. vaginalis was highly resistant to bensulfuron-methyl, moderately resistant to bispyribac-sodium, had low resistance to penoxsulam and 2,4-D dimethyl ammonium, and was susceptible to sulfentrazone. The nucleotide sequences of the ALS gene of resistant and susceptible biotypes showed 14 base substitutions, which caused two amino acid substitutions: Val-143-Ile and Val-148-Ile. It is the first report of the substitutions of amino acids Val-143-Ile and Val-148-Ile in ALS protein. Those mutations may give different resistance spectra against three ALS-inhibitor herbicides: bensulfuron-methyl, bispyribac-sodium, and penoxsulam. Further research is needed to elucidate the molecular basis of target-site resistance mechanisms such as the transformation of the ALS gene of M. vaginalis. It is also necessary to evaluate herbicide mixtures and/or the rotation of herbicide sites of action to control the resistant biotype of M. vaginalis. [ABSTRACT FROM AUTHOR]

Monochoria vaginalis is one of the most serious weeds of rice fields in Asia. The species has both chasmogamous (CH) and cleistogamous (CL) flowers on individual plants. The objective of this study is to clarify the reproductive characteristics that affect the selfing rate of M. vaginalis. An emasculation experiment revealed that the CH flowers emasculated just after flower opening produced seeds. The seed production in the flowers emasculated just after flower opening was less than that of the flowers emasculated and hand-pollinated with pollen from another plant. These results indicate that, although self-pollination before anthesis occurs, cross-pollination also can produce seeds. An experimental manipulation of light and the emergence time of the plants revealed that more than half of the flowers produced were CL flowers and the CH/CL ratio decreased with reduced light availability. The plants that emerged later produced as many CH flowers as those that emerged earlier. There was no significant difference between the CH and CL flowers in the seed number per fruit and the seed mass. These results suggest that M. vaginalis has reproductive characteristics that make the selfing rate high; however, outcrossing also can occur. Under favorable light intensity conditions, such as on the edges of paddy fields or in fallow fields, M. vaginalis will produce more CH flowers and will have a higher outcrossing rate than in shaded conditions. [ABSTRACT FROM AUTHOR]

It has been only recently that the biological control of weeds by insects was practiced in Korea. Since the diverse crop farming practices in relatively small farms, it has been underestimated by the chemical control practice. The need to find alternative methods from the presence of herbicide-resistant weeds and growing ecological concern requires immediate action to be followed. The Integrated Weed Management Laboratory at the National Institute of Agricultural Science and Technology at the Rural Development Administration was set up to initiate weed biological control research. Since then, four research projects on weed biological control by insects were carried out. The target weed species were as follows: Rumex obtusifolius, Ambrosia trifida, Acalypha australis, and Monochoria vaginalis. In this review, some of the findings both published and unpublished were presented to show the status of the weed biological control by insects in Korea. [ABSTRACT FROM AUTHOR]

The inheritance of sulfonylurea (SU) resistance in Monochoria vaginalis was investigated based on the bensulfuron-methyl response phenotypes of F1 plants between SU-resistant (R) and -susceptible (S) and segregation analysis in F2 progenies. Differences of SU resistance between SU-R biotypes and F1 plants at the recommended field dose were also investigated by comparing shoot dry weight. All F1 plants survived the treatment with 25 g a.i. ha−1 bensulfuron-methyl, one-third of the recommended field dose, and showed similar responses to SU-R plants. Conversely, all F1 plants died or showed extreme necrosis at 225 g a.i. ha−1, three times the recommended field dose, as SU-S plants. F2 plants were classified as either R or S phenotype. Segregation for resistance to bensulfuron-methyl in F2 families did not differ from the expected 3:1 (R:S) ratio at 25 g a.i. ha−1. At 225 g a.i. ha−1, the F2 families segregated in a 1:3 (R:S) ratio. These results suggest that SU resistance in M. vaginalis is controlled by a single nuclear allele with resistance being dominant at low dose and susceptibility dominant at high dose. Moreover, F1 plants died or were extremely injured after application of bensulfuron-methyl at the recommended field dose, although SU-R biotypes grew normally. [ABSTRACT FROM AUTHOR]

Monochoria vaginalis is one of the most serious weeds of rice fields in Asia. The species is predominantly selfing. To reveal the potential for multiple mutational events, outcrossing and gene flow in the sulfonylurea-resistant (SU-R) M. vaginalis populations, we investigated (i) if each SU-R population was a single SU-R biotype or a mixture of several SU-R biotypes using restriction analysis or direct sequencing of acetolacatate synthase (ALS) genes and (ii) genetic diversity of SU-R and -susceptible (S) populations using amplified fragment length polymorphism (AFLP) analysis. Nineteen or 20 individuals were sampled from four SU-R and five SU-S populations respectively. Amino acid substitutions conferring resistance in the SU-R populations were Pro197Ser in the ALS1 or ALS3, or Asp376Glu in the ALS1 and each SU-R population was composed of a single SU-R biotype. In cluster analysis each SU-R individual formed a cluster, whereas the individuals from a SU-S population belonged to different clusters. Some SU-R populations showed polymorphic AFLP loci. The results indicated that these SU-R biotypes emerged from a single mutational event and any gene flow of SU-R genes from adjacent populations did not occur. A low level of outcrossing and recombinations of SU-R genes occurred within some SU-R populations of M. vaginalis. [ABSTRACT FROM AUTHOR]

Two molecular genetic screening techniques, RAPD (random amplified polymorphic DNAs) and ISSR (inter-simple sequence repeats), were applied to detect the level and pattern of genetic diversity of Monochoria vaginalis, a common weed of rice fields, in seven populations from southern China. Among these populations, 116 bands were amplified by 18 RAPD primers, of which 34 bands (29.31%) were polymorphic, and 14 ISSR primers produced 111 bands with 87 polymorphic bands (78.38%). Within each population, a relatively low level of genetic diversity was detected by both RAPD and ISSR analyses, with a mean genetic diversity ( H) of 0.0348 and 0.0551 respectively. Analysis of molecular variance of the data from the RAPD and ISSR markers detected that the majority of total genetic variation existed among populations (73.50% and 76.70% respectively) and only minor genetic variation within populations (26.50% and 23.30% respectively). Cluster analysis divided the seven populations into two groups, indicating that the genetic relationships among populations have relatively low correlation with their geographical distribution (Mantel test; r = 0.45 and 0.48 respectively). Our results indicated that both RAPD and ISSR markers were effective and reliable for accurately assessing the degree of genetic variation of M. vaginalis. Comparing the two techniques, ISSR markers were more efficient than the RAPD assay. The Mantel test gave r = 0.16, suggesting no correlation between these two molecular markers. [ABSTRACT FROM AUTHOR]

Acetolactate synthase (ALS) is the target enzyme for four distinct families of compounds: sulfonylureas (SUs), imidazolinones, triazolopyrimidine sulfonanilides, and pyrimidinyl oxybenzoates. We cloned and sequenced the fragments encoding ALS genes from biotypes of Monochoria vaginalis susceptible (S) and resistant (R) to SU-herbicides. The nucleotide sequences of the 39 bp Domain A region for R M. vaginalis biotype differed from that of the S biotype by a single nucleotide substitution at variable Pro codon of Domain A (CCT to TCT), predicting a Pro in the S but a Ser in the R biotype. No nucleotide differences between S and R M. vaginalis were observed in Domain D. We suggest that the amino acid substitution at Domain A region is responsible for resistance to SU-herbicides in M. vaginalis collected from Ushiku City, Ibaraki Prefecture, Japan. [Copyright &y& Elsevier]

Field experiments involving eight cultivars were conducted in 1998 and 16 cultivars in 1999 to study the ability of rice (Oryza sativa L.) to suppress Monochoria vaginalis (Burm. f ) Kunth through light competition. Dry weights of M. vaginalis shoots in early season culture exceeded those in normal season culture of any rice cultivars. The relative photosynthetic photon flux density (R-PPFD), which was calculated as the ratio of the photosynthetic photon flux density (PPFD) below the rice canopy to that measured above the rice canopy, varied according to rice cultivar. A strong linear correlation was observed between the mean R-PPFD at 29–35 days after transplanting (DAT) (r [sup 2] = 0.80; p < 0.01 in 1998; r [sup 2] = 0.63, p < 0.001; and r [sup 2] = 0.93, p < 0.001 in 1999), or 36–42 DAT (r [sup 2] = 0.66, p < 0.05 in 1998; r [sup 2] = 0.72, p < 0.001; and r [sup 2] = 0.97, p < 0.001 in 1999), and the dry weight of M. vaginalis shoots at approximately 60 DAT. Data from the three experiments could be pooled into one regression line because intercepts and regression coefficients were not significantly different. The r [sup 2] values of the combined regression were highest when R-PPFD was expressed as the mean of measurements taken during 14 days (from 29 to 42 DAT; r [sup 2] = 0.81, p < 0.001). The shortest period for measuring mean R-PPFD in order to obtain a meaningful relationship with M. vaginalis shoot dry weight was 7 days (from 29 to 35 DAT; r [sup 2] = 0.78, p < 0.001). For that same period, relationships between M. vaginalis shoot dry weight at 60 DAT and rice tiller number or leaf area index (LAI) at ground level were weak. However, there were negative relationships between M. vaginalis shoot dry weights at 60 DAT and rice LAI measured 20 cm above the ground, plant heights or rice shoot dry weight, but these coefficients of determination were smaller than those calculated by R-PPFD for the same period. Thus, the ability of rice to suppress M. vaginalis can be evaluated more accurately by measuring mean R-PPFD below the rice canopy for 7 days (from 29 to 35 DAT) than by measuring rice LAI, plant height and shoot dry weight. [ABSTRACT FROM AUTHOR]

Abstract: Monochoria vaginalis is one of the most common and troublesome annual broadleaved weeds in rice paddies in Asia. It competes with rice for N uptake. Recent studies suggest that some plants can produce CH4 under aerobic conditions and some can produce N2O during nitrate assimilation. To test whether M. vaginalis emits either gas and hence is a significant contributor to greenhouse gas emissions, we grew plants in pots filled with paddy soil. CH4 and N2O emissions were not detected both from the M. vaginalis–soil system and from the aboveground plant tissues during 30- and 60-min sampling. In a 1-day incubation experiment in bottles, leaves, stems, and roots of M. vaginalis obviously emitted N2O but not CH4. Roots produced more N2O than leaves and stems, possibly owing to associated nitrifying or denitrifying bacteria. Therefore, we found no evidence of CH4 production, and possible evidence of slight N2O production in the tissues of M. vaginalis. [Copyright &y& Elsevier]