Red Rice Control Research Articles

Mixture interactions of quizalofop and reduced rates of halosulfuron

AbstractA field study was conducted in 2017 and 2018 at the Louisiana State University Agricultural Center H. Rouse Caffey Rice Research Station near Crowley, LA, to evaluate the impact of reduced rates of halosulfuron on quizalofop activity in Louisiana rice production. Halosulfuron and a prepackaged mixture of halosulfuron plus thifensulfuron were evaluated at 0, 17, 35, or 53 g ai ha−1 and 34 or 53 g ai ha−1, respectively, in a mixture with quizalofop at 120 g ai ha−1. Control of barnyardgrass, red rice, and two non-acetyl-CoA carboxylase resistant rice lines, CL-111 and CLXL-745, were recorded at 14 and 28 d after treatment (DAT). The red rice, CL-111, and CLXL-745 represented a weedy rice population. Across all species evaluated at 14 DAT, all mixtures containing halosulfuron and halosulfuron plus thifensulfuron resulted in antagonism with an observed control of 79% to 90%, compared with an expected control of 96% to 99%. At 28 DAT, all mixtures containing halosulfuron resulted in neutral interactions for barnyardgrass control. Quizalofop mixed with halosulfuron plus thifensulfuron at the lower rate of 34 g ha−1 was able to overcome the antagonism compared with the higher rate of 53 g ha−1 for barnyardgrass control at 28 DAT. Both the high and the low rate of halosulfuron plus thifensulfuron resulted in antagonistic interaction for red rice, CL-111, and CLXL-745 control at 28 DAT. This research suggests that mixing quizalofop with halosulfuron plus thifensulfuron should be avoided, especially at the higher rate of 53 g ha−1.

A, The ALLELOPATHIC EFFECT OF AQUEOUS EXTRACT OF CARTHAMUS TINCTORIUS ON GERMINATION AND INITIAL SEEDLING GROWTH OF ORYZA PUNCTATA

ABSTRACT Chemical weed control method creates environmental hazards and residual effects in crops and soil. Alternate approach to control weeds is getting attentions in sustainable production system. Aqueous extract of crop is an important technique to control weed and also environment friendly and cheap. To investigate the herbicidal potential of aqueous extract of winter crop Carthamus tinctorius (safflower) on summer weed Oryza punctata (red rice) seed germination and initial seedling growth, a study was planned in Weed Science Laboratory. In this study, seeds of C. tinctorius were incubated in seven concentrations (0, 0.25, 0.50, 1, 2, 4, and 8%) of different parts i.e. leaves, stem, flower of C. tinctorius. All the tested concentrations of various plant parts of C. tinctorius significantly inhibited the mean emergence time, germination index, germination percentage (%), time taken to 50% germination as well as growth of O. punctata weed. However, maximum mean emergence time (4.73 days), time taken to 50% germination (4.19 days) was noted at 8% concentration and germination index of O. punctata was noted at 0.25% concentration when flower extract was applied. Leaf aqueous extract at the concentration 8% caused the lowest root length (1.53 cm), shoot length (4.51 cm) and fresh weight (54.72 g) of O. punctata. Results suggested leaf and flower extract of C. tinctorius at concentration (8%) can be used potential bio-herbicide for the control of red rice. Key words: Allelopathy, seedling growth, inhibitory, weed growth, plant parts, promotor

Evaluation of sequential applications of quizalofop-p-ethyl and propanil plus thiobencarb in acetyl-coA carboxylase inhibitor–resistant rice

AbstractA field study was conducted in 2015 and 2016 at the H. Rouse Caffey Rice Research Station near Crowley, Louisiana, to evaluate the interactions of quizalofop and a mixture of propanil plus thiobencarb applied sequentially or mixed to control weedy rice and barnyardgrass. Visual weed control evaluations occurred at 14, 28, and 42 d after treatment (DAT). Quizalofop was applied at 120 g ai ha−1 at 7, 3, and 1 d before and after propanil plus thiobencarb were each applied at 3,360 g ai ha−1. In addition, quizalofop was applied alone and in a mixture with propanil plus thiobencarb at day 0. Control of red rice ‘CL-111’ and ‘CLXL-745’ was greater than 91% when quizalofop was applied alone at day 0, similar to control for quizalofop applied 7, 3, and 1 d prior to propanil plus thiobencarb at all evaluation dates. Control of the same weeds treated with quizalofop plus propanil plus thiobencarb applied in a mixture at day 0 was 70% to 76% at each evaluation date, similar to quizalofop applied 1 or 3 d after propanil plus thiobencarb. A similar trend in control of barnyardgrass by 88% to 97% occurred when quizalofop was applied alone and by 48% to 53% at 14, 28, and 42 DAT when the mixture was used. ‘PVL01’ rough rice yield was 4,060 kg ha−1 when treated with quizalofop alone; however, yield was reduced to 3,180 kg ha−1 when it was treated with quizalofop mixed with propanil plus thiobencarb at day 0, similar to PVL01 rice treated with quizalofop 1 or 3 d following the propanil plus thiobencarb application.

Quizalofop-p-ethyl application in water-seeded coenzyme A carboxylase–inhibiting herbicide-resistant rice with different flood systems

AbstractA field study was conducted during the 2016 and 2017 crop seasons at the LSU AgCenter H. Rouse Caffey Rice Research Station to evaluate weed control and rice yield after quizalofop-p-ethyl applications in water-seeded coenzyme A carboxylase (ACCase)–resistant ‘PVLO1’ long-grain rice production utilizing different flood systems, application timings, and quizalofop rates. The initial application of quizalofop was applied at five timings beginning when ‘PVLO1’ rice was at the coleoptile stage (PEG) through the one- to two-tiller stage. A total quizalofop rate of 240 g ai ha–1 was split into two applications: 97 followed by 143 g ha–1 or 120 followed by 120 g ai ha–1 in both pinpoint and delayed flood water-seeded management systems. A second quizalofop application was applied 14 d after initial treatment (DAIT). At 14 DAIT, a reduction in control of barnyardgrass and red rice was observed by delaying the initial quizalofop application to the two- to four-tiller stage compared with rice treated at earlier growth stages. At 42 DAIT, control of barnyardgrass was 94% to 96%, and red rice was 98% following the second application of quizalofop, regardless of initial application timing. Rice treated with quizalofop at the PEG and two- and three-leaf stage resulted in a rice height of 104 cm at harvest compared with 96 to 100 cm when the initial application of quizalofop was delayed to later growth stages. Applying the initial application of quizalofop to rice at the PEG timing in the pinpoint or the delayed flood system resulted in a total gross value per hectare of $450 and $590, respectively. Within each flood system, delaying the initial application of quizalofop to the one- to two-tiller stage resulted in a gross per-hectare value reduction of $100 ha-1 in the pinpoint flood and $110 ha-1 in the delayed flood.

Do adjuvants reduce the antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na?

AbstractAcetyl co-enzyme A carboxylase (ACCase)-resistant rice allows quizlaofop-p-ethyl to be applied as a POST control of troublesome grass weeds. A field study was conducted in 2017 and 2018 at the H. Rouse Caffey Rice Research Station near Crowley, LA, to evaluate the influence of a crop oil concentrate (COC), a silicon-based surfactant plus a nitrogen source (SNS), or a high-concentrate COC (HCOC) in overcoming the grass weed control antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na. Quizalofop-p-ethyl was applied at 120 g ai ha−1, bispyribac-Na was applied at 34 g ai ha−1, and all adjuvants were applied at 1% vol/vol. Antagonistic interactions were observed at 14 d after treatment (DAT) when quizalofop-p-ethyl was mixed with bispyribac-Na with no adjuvant for control of barnyardgrass, the non–ACCase-tolerant rice cultivars ‘CL-111’ and ‘CLXL-745’, and red rice. At 14 DAT, antagonism of quizalofop-p-ethyl for control of barnyardgrass was observed when mixed with bispyribac-Na plus COC, SNS, or HCOC, with an observed control of 43%, 63%, and 86%, respectively, compared with an expected control of 95% for quizalofop-p-ethyl alone. However, the antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na plus HCOC for barnyardgrass control at 14 DAT was overcome by 28 DAT, with an observed control of 91%, compared with an expected control of 97%. Synergistic or neutral interactions were observed at 14 and 28 DAT when COC, SNS, or HCOC was added to a mixture of quizalofop-p-ethyl plus bispyribac-Na for CL-111, CLXL-745, and red rice control. According to the results of this study, HCOC is the most effective adjuvant for quizalofop-p-ethyl and bispyribac-Na mixtures for control of weedy rice and barnyardgrass.

Diversification of Crops and Conservation Management in Lowland Soils of Rio Grande do Sul

The lowland soils in Rio Grande do Sul occupy an area of approximately 5.4 million hectares of the state. They are flat to mildly hilly topography soils, developed, under varied conditions of drainage deficiency (hydromorphism). In this ecosystem, the extensive productive livestock system and irrigated rice were developed, used successfully for many decades. However, its characteristics and peculiarities have contributed to the cost of production, disseminate weed seeds in the crops and degrade the physical state of the lowland soils, due to this, the interest arose for the use of new alternatives that were, at the same time, efficient in the control of red rice, economically viable and able to maintain or even recover soil quality. The search for practices capable of increasing the productivity of irrigated rice and, especially, its sustainability over time has been the focus of several studies, so the objective of this review was to present aspects related to crop diversification and conservation management of lowland soils, mainly in relation to rotation and succession practices.

Quizalofop interactions when mixed with clomazone and pendimethalin in acetyl coenzyme A carboxylase–inhibiting herbicide-resistant rice

AbstractA study was conducted in 2017 and 2018 at the H. Rouse Caffey Rice Research Station near Crowley, LA, to evaluate quizalofop at 120 g ai ha−1 applied independently or in a mixture with clomazone, pendimethalin, clomazone plus pendimethalin, or a prepackaged mixture of clomazone plus pendimethalin when PVLO1 rice reached the two- to three-leaf stage. A second application of quizalofop at 120 g ha−1 was applied 21 d after the initial application. At 7 days after treatment (DAT), antagonism of quizalofop occurred when mixed with clomazone at 334 g ai ha−1, clomazone at 334 g ai ha−1 plus pendimethalin at 810 g ai ha−1, or a prepackaged mixture of clomazone plus pendimethalin at 334 plus 810 g ai ha−1, respectively, when applied to barnyardgrass. At 7 DAT, a neutral interaction occurred with a mixture of quizalofop plus pendimethalin at 810 g ha−1. These data indicate the antagonism of quizalofop was overcome at 14, 28, and 42 DAT with a neutral interaction for barnyardgrass control, 94% to 98%, with all herbicide mixtures evaluated. A neutral interaction occurred for CL-111, CLXL-745, and red rice control when treated with all the herbicide mixtures evaluated across all evaluation dates. Rice yield decreased when not treated with the initial quizalofop application.

Efficacy of fall-applied residual herbicides on weedy rice control in rice (Oryza sativa L.)

AbstractField experiments were initiated near Colt, AR, in the fall of 2016 and continued through the summer of 2018 to evaluate rice tolerance and weedy (or red) rice control after fall-applied very-long-chain fatty acid (VLCFA)-inhibiting herbicides. A split-plot design was used for the experiment, with the whole-plot factor being winter condition (flooded or non-flooded) and the split-plot factors being herbicide and rate. Herbicide treatments included acetochlor, dimethenamid-P, pethoxamid, pyroxasulfone, andS-metolachlor applied at 1,050, 525, 420, 205, and 1,070 g ai ha−1and at 2,100, 1,050, 840, 410, and 2,140 g ha−1for low rates and high rates, respectively. Herbicides were applied in the fall, then ‘CL172’ rice was drill seeded in the spring of the following calendar year. Weedy rice control differed between years, but acetochlor and pyroxasulfone consistently provided the greatest levels of control across rates and flood conditions. Consequently, herbicides that best controlled weedy rice also caused the greatest injury to cultivated rice. Rice injury did not exceed 13% regardless of herbicide treatment at 3 wk after planting (WAP). However, the high rate of pyroxasulfone caused 20% rice injury at 5 WAP in 2018. Although it was expected that winter condition may affect residual activity of the VLCFA-inhibiting herbicides, herbicide selection and application rate both had much greater effects on rice injury and on weedy rice control. Based on these results, rice injury would be minimal or nonexistent after fall applications of the tested VLCFA inhibitors, and intermediate levels of weedy rice control may be achieved. The implementation of VLCFA-inhibiting herbicides in rice production systems would offer a novel herbicide site of action and offer a degree of selective control of weedy rice.

Spatial and temporal evolution of imidazolinone-resitant red rice in 'Clearfield' rice cultivations

Abstract: The objective of this work was to evaluate the distribution of imidazolinone-resistant (IMI-R) red rice (Oryza sativa) populations, the frequency of alleles conferring resistance to IMI, and the adoption of agronomic practices applied to red rice control, across growing seasons and production regions of the state of Rio Grande do Sul (RS), Brazil. In the experiment, 1,008 red rice populations were screened for resistance to IMI, 760 IMI-R red rice plants were genotyped for the acetolactate synthase (ALS) alleles conferring resistance to IMI, and 40 'Clearfield' rice growers were surveyed. IMI-R red rice populations were widespread throughout RS since the 2006/2007 growing season, with a higher initial frequency in the Depressão Central and Fronteira Sul production regions. The occurrence of IMI-R red rice ranged from 1.6 to 3.5 years after 'Clearfield' rice release. Gly654Glu was the most frequent ALS mutation in IMI-R red rice populations, which shows a gene flow from the most used 'Clearfield' rice cultivars to the red rice plants. Crop rotation systems and certified seed were used by only 30% of the surveyed growers of 'Clearfield' rice, with lower percentages in the production regions where IMI-R red rice appeared faster.

Imazethapyr plus Propanil Mixtures in Imidazolinone-Resistant Rice

AbstractA study was conducted in three locations in Louisiana to evaluate interactions of imazethapyr at 0 and 70 g ai ha−1mixed with propanil at 0, 1,120, 2,240, 3,360, and 4,480 g ha−1for the control of red rice, barnyardgrass, and hemp sesbania. According to Blouin’s modified Colby’s, a synergistic response occurred for red rice treated with imazethapyr mixed with propanil at 4,480 g ha−1for all evaluations. Observed control was 93% to 95% compared with expected control of 81% to 87%. An antagonistic response occurred for barnyardgrass control with imazethapyr mixed with propanil at 1,120 g ha−1at 35 and 49 d after treatment (DAT), with control of 75% and 64%, respectively, compared with expected control of 89% and 78%. However, a neutral response occurred for barnyardgrass control when treated with all other imazethapyr plus propanil combinations. An antagonistic interaction occurred for hemp sesbania when treated with imazethapyr plus propanil at 3,360 and 4,480 g ha−1at 21 DAT with an observed control of 89% compared with an expected control of 96%; however, a neutral response occurred at all other evaluation dates. An increase in rice yield was observed with an imazethapyr plus propanil at 4,480 g ha−1mixture compared with a single application of imazethapyr or propanil at any rate evaluated.

Synergism with Imazamox Co-applications for Red Rice Control

A study was conducted at three locations in Louisiana to evaluate the interactions of imazamox at 44 g ai ha−1mixed with propanil, thiobencarb, or with a prepackaged mixture of propanil plus thiobencarb. A synergistic response was observed for red rice control for all treatments at 14 days after treatments (DAT); however, at 21 DAT a neutral response was observed for imazamox mixed with propanil or thiobencarb. A synergistic response occurred for red rice control when imazamox was mixed with propanil plus thiobencarb at 3360 g ai ha−1for all evaluation dates; however, imazamox mixed with propanil plus thiobencarb at 1680 g ha−1resulted in synergism at the same evaluations except at 35 DAT with neutral response. Synergism was observed for barnyardgrass control with imazamox mixed with propanil plus thiobencarb at 3360 g ha−1at 35 and 49 DAT. The only antagonism observed for barnyardgrass control was at 42 DAT with imazamox plus propanil at 840 and 1680 g ha−1or mixed with the prepackage mixture at 1680 g ha−1. Rice treated with imazamox mixed with propanil plus thiobencarb at 3360 g ha−1yielded 5770 kg ha−1.

PERSISTENCE OF IMIDAZOLINONES IN SOILS UNDER A CLEARFIELD SYSTEM OF RICE CULTIVATION

ABSTRACT The commercial mixture of imazethapyr and imazapic herbicides has been used for the control of red rice and several other species of weeds found in rice crops; this system called Clearfield. However, its use may limit the succession of non-tolerant crops for long residual activity. The research objective with this work was to determine the persistence of imazethapyr, imazapic and their mixture in three soils in the Brazilian state of Tocantins. Three experiments were conducted in a completely randomized design with four replications, each corresponding to the evaluated soil (Haplic Plinthosol (FX), red-yellow Latosol (LVA) and Haplic Gleysol (GX)). The treatments were arranged in a split plot design, with the allocated plots herbicides (imazethapyr and imazapic alone and commercial mixture) and the plots allocated the 11 evaluation times (1, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150 days after treatment (DAT)), and a control without application. Contacted up long residual effect of imazethapyr and commercial mixture of imazethapyr and imazapic, regardless of assessed soil. After 150 days of applying herbicides or the commercial mixture, their residues in the soil also inhibited approximately 94% of the mass of the dry matter accumulation of the indicator plants. When imazapic was applied alone, there was a higher dry matter accumulation of the indicator plants, indicating less residual effect of this herbicide in the soil and this was attributed to the lower dose of this herbicide applied. The attributes of the soil pH, texture and iron oxides were what most affected the persistence of the herbicides. It can be concluded that the persistence of imazethapyr and imazapic is too long in the Brazilian state of Tocantins soils and the use of these herbicides in the region should be avoided due to the high risk of the occurrence of carryover,or be well planned, as land use in rotation for susceptible crops.

Imazamox Plus Propanil Mixtures for Grass Weed Management in Imidazolinone-Resistant Rice

A study was established to evaluate interactions between imazamox at 0 and 44 g ai ha−1mixed with propanil at 0, 1,120, 2,240, 3,360, and 4,480 g ai ha−1for the control of red rice and barnyardgrass. Blouin's Modified Colby's procedure was used to test for interactions. At 7 d after treatment (DAT), a synergistic response occurred for red rice treated with imazamox at 44 g ha−1mixed with propanil at 3,360 and 4,480 g ha−1by increasing expected control of 62% to an observed control of 67 and 75%, respectively, and the synergistic response continued across all evaluations through 49 DAT. No antagonism occurred for any imazamox plus propanil mixture for red rice control. An antagonistic response was shown for barnyardgrass control with imazamox at 44 g ha−1mixed with any rate of propanil, at 7 DAT. However, imazamox plus propanil at 4,480 g ha−1resulted in a neutral response at 14 through 49 DAT. Rice treated with imazamox plus propanil at 4,480 g ha−1plus imazamox resulted in a yield of 6,640 kg ha−1. The synergistic response observed for red rice control with a mixture of imazamox plus propanil can benefit producers by increasing control of red rice, and this mixture contains two different modes of action that can be part of an overall resistance management strategy.

Imazethapyr Co-Application Interactions in Imidazolinone-Resistant Rice

A study was conducted to evaluate interactions of imazethapyr co-application with propanil, thiobencarb, or a prepackaged mixture of propanil plus thiobencarb. At 7, 14, 21, and 49 d after treatment (DAT), synergism occurred for red rice treated with imazethapyr at 70 g ai ha−1mixed with propanil plus thiobencarb at 1,680 and 3,360 g ai ha−1. A synergistic response was also observed with imazethapyr at 70 g ha−1mixed with propanil at 1,680 g ha−1; however, all other co-applications evaluated resulted in a neutral response with no antagonism observed. At 7 DAT, antagonism was observed for barnyardgrass when treated with imazethapyr at 70 g ha−1mixed with propanil plus thiobencarb at 1,680 g ha−1, propanil at 840 g ha−1, or thiobencarb at 840 and 1,680 g ha−1; however, a synergistic response occurred for barnyardgrass control at 14, 21, and 49 DAT with imazethapyr at 70 g ha−1mixed with propanil plus thiobencarb at 3,360 g ha−1. The synergistic response observed for red rice and barnyardgrass control with a mixture of imazethapyr plus propanil plus thiobencarb can benefit producers by increasing control of red rice and barnyardgrass, and this mixture contains three herbicides with three different modes of action, which can be part of an overall resistance-management strategy in imidazolinone-resistant (IR) rice.

Sensitivity of imidazolinone-resistant red rice (Oryza sativa L.) to glyphosate and glufosinate

<p>Dose-response experiments were carried out to evaluate the sensitivity of imidazolinone-resistant red rice to nonselective herbicides currently used in rice-soybean rotation in Rio Grande do Sul. Two red rice biotypes previously identified as resistant and susceptible to the imidazolinone herbicides were treated with imazapic plus imazapic, glyphosate and glufosinate under nine herbicide rates. A non-linear log-logistic analysis was used to estimate the herbicide rate that provided 50% red rice control and dry weight reduction (GR<sub>50</sub>). Imidazolinone-resistant red rice exhibited greater GR<sub>50</sub> values than imidazolinone-susceptible biotype for imazapyr plus imazapic. In contrast, both imidazolinone-resistant and susceptible red rice showed similar GR<sub>50</sub>values for glyphosate and glufosinate. These results indicate that glyphosate and glufosinate effectively control imidazolinone-resistant red rice at similar herbicide rates used to control imidazolinone-susceptible; however, integrated weed management practices must be adopted in rice-soybean rotation to delay resistance evolution of red rice populations to glyphosate and glufosinate</p>

Red Rice Control and Soybean Tolerance to <i>S</i>-Metolachlor in Association with Glyphosate

Red rice is one of the major troublesome and difficult weeds to control in rice production regions. The introduction of the Clearfield&#174 technology allowed producers to control red rice using rice genotypes tolerant to the imidazolinone herbicides. However, because the consecutive use of this technology red rice biotypes have evolved resistance to imidazolinone herbicides, the rice-soybean rotation has been an alternative used by producers to control this weed. This system allows the use of herbicides with different modes of action to control red rice, such as S-metolachlor. Thus, greenhouse and field experiments were carried out during the 2011 to 2012 and 2012 to 2013 growing seasons to evaluate: 1) sensitivity of imidazolinone-resistant red rice to S-metolachlor; 2) red rice control and soybean tolerance in response to associations of S-metolachlor and glyphosate. In greenhouse, S-metolachlor effectively controlled both susceptible and imidazolinone-resistant red rice in preemergence. In field, preemergence applications of S-metolachlor provided greater red rice control in comparison to S-metolachlor alone in early postemergence. The association of S-metolachlor with glyphosate did not improve red rice control in preemergence application. However, association of S-metolachlor with glyphosate significantly improved red rice control in early postemergence applications. S-metolachlor injury to soybean increased with early postemergence applications. These results indicate that S-metolachlor effectively control imidazolinone-resistant red rice in rice-soybean rotation.

Associação de glyphosate e imidazolinonas no controle de arroz-vermelho em arroz Clearfield®

O objetivo do presente trabalho foi o de avaliar os efeitos da utilização de glyphosate e herbicidas imidazolinonas, em aplicações isoladas ou associadas, sobre o controle de arroz-vermelho (Oryza sativa) e produtividade de grãos de arroz Clearfield®. O experimento foi conduzido a campo na safra 2007/08, em Cachoeirinha, RS, Brasil, com delineamento em blocos ao acaso e tratamentos dispostos em arranjo fatorial (2x6), usando-se quatro repetições. O fator A constou de dois níveis do herbicida glyphosate, aplicados no subperíodo semeadura-emergência da cultura por ocasião do início da emissão do coleóptilo do arroz (ponto de agulha); o fator B constou de seis tratamentos com imazethapyr+imazapic, aplicados em associação ao glyphosate ou quando a cultura atingiu o estádio de três folhas expandidas. As três variáveis explicativas analisadas foram a população de plantas de arroz e arroz-vermelho, a eficácia do controle de arroz-vermelho e a produtividade de grãos da cultura. O uso de glyphosate no ponto de agulha reduziu em 75% a população do arroz-vermelho e aumentou em 40% a produtividade de grãos de arroz, em relação à testemunha. O uso isolado de herbicidas imidazolinonas e sua associação com o dessecante proporcionou controle eficaz do arroz-vermelho e incrementou a produtividade de grãos, em comparação à situação sem controle da infestante, independente da dose e do sistema de aplicação.

Effects of irrigated rice sowing season and imazapyr + imazapic time of application on rice grain yield and red rice management

Irrigated rice sowing season and red rice competition are among the main factors affecting grain yield. The objective of this work was to evaluate the sowing date of irrigated rice and moments of application of the herbicide imazapyr + imazapic to control red rice management and irrigated rice grain yield. Eight experiments were performed at the following dates (09/30, 10/19, 11/08 and 12/01) for the 2010/2011 harvest season and (09/27, 10/17, 11/08 and 12/05) for the 2011/2012 harvest season. The treatments were: application of the herbicide imazapyr + imazapic at doses of 105+35 g ha-1 in pre-emergence (PRE); 52.5+17.5 g ha‑1 in pre-emergence and 52.5+17.5 g ha-1 in post-emergence (PRE + POST); and 105+35 g ha-1 in post- emergence (POST), and a control without application and no weeding. The cultivar Puitá Inta CL was used and a randomized block design with four replicates. A joint analysis of the experiments was carried out. There was less emergence of red rice and higher grain yield of the irrigated rice at the early periods (09/30/10 and 09/27/11), with 10,578 and 8,653 kg ha-1, respectively. At the end of the season (12/01/10 and 12/05/11), there was greater reduction of the red rice seed bank. Sowing at the beginning of the recommended period provided more irrigated rice grain yield. The application of imazapyr + imazapic at a dose of 52.5+17.5 g ha-1 in PRE + 52.5+17.5 g ha-1 POST, and 105+35 g ha-1 only in PRE and POST was effective in the control of red rice.

Characterization and simultaneous determination of immunosuppressive decalins in red yeast rice by ultra-high-performance liquid chromatography hyphenated with mass spectrometry

Decalins are secondary metabolites of red yeast rice with immunosuppressive effects on human T cell proliferation. In this study, ultra-high-performance liquid chromatography hyphenated with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) was employed for elucidation of the mass fragmentation patterns of decalins by collision-induced dissociation tandem mass spectrometry (CID-MS/MS). Based on the MS/MS fragmentation patterns of the authentic decalin standards as well as high mass accuracy, a new decalin in the crude extract of red yeast rice was further putatively identified. Moreover, a quantitative analysis method of five immunosuppressive decalins by ultra-high-performance liquid chromatography hyphenated with triple quadrupole tandem mass spectrometry (UHPLC–QQQ-MS) under multiple reaction monitoring (MRM) mode was developed and validated. This method exhibits limits of detection from 0.44 to 1.96mg/kg, and precision variations were less than 3.2%, and the recovery was in the range of 82 and 105% with RSD less than 5.4%. This method was successfully applied in the quantitative analysis of decalins in different types of red yeast rice. The results showed that decalins only exist in functional red yeast rice but not in the common one. The study demonstrated that UHPLC-Q-TOF-MS and UHPLC–QQQ-MS methods described in this paper are powerful and reliable tools for the quality control of red yeast rice.

Red rice (Oryza sativa) cross-resistance to imidazolinone herbicides used in resistant rice cultivars grown in northern Greece

A putative resistant red rice (Oryza sativa) accession, an imidazolinone-resistant rice cultivar (Clearfield), a susceptible red rice accession and a susceptible rice cultivar were evaluated for cross-resistance to imazamox and imazethapyr in a whole-plant response experiment and seed bioassay. Additionally, a 210-bp fragment of the ALS gene was sequenced to identify mutations responsible for resistance. Also, a 574bp of the ALS gene was sequenced and PCR for detection of the ‘Clearfield allele’ was conducted by the Andalusian Institute of Agricultural Research and Training (IFAPA, Spain). In the whole-plant response experiment, the putative resistant red rice was >23 and >21 times more resistant to imazamox and imazethapyr than the susceptible accession, respectively, whereas the respective resistance factor values based on seed bioassay were 86.4 and 141.7. Also, the respective resistance factor values for the Clearfield rice cultivar were similar with those calculated for putative resistant red rice. Additionally, the sequence of the 210bp ALS gene fragment from the putative resistant red rice and Clearfield rice cultivar revealed the same amino acid substitution of Ser653Asn in both alleles (homozygous). Furthermore, the sequence of a 574bp ALS gene fragment and the PCR for detection of the ‘Clearfield allele’ confirmed that the putative resistant red rice is homozygous mutant for the Ser653Asn mutation and provided additional evidence that its genetic background matches that of Clearfield rice. These findings indicate clearly that the insufficient control of the putative resistant red rice with imazamox was due to target-site resistance and particularly due to a point mutation at the Ser653 codon, which is positively identified as having been derived from the Clearfield rice cultivar.