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Barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is a problematic weed in rice (Oryza sativa L.) fields. Overapplication of herbicides causes environmental pollution and the emergence of resistant weeds, and integrated weed management methods can reduce dependence on herbicides. The growth of E. crus-galli and rice seedlings was shown to be significantly inhibited by high concentrations of fulvic acid (FA, C14H12O8) under flooding conditions (HF, 0.80 g L−1) (P < 0.05). In contrast, seedling growth was promoted by the application of very low concentrations of FA (LF, 0.02 g L−1). The activities of glutathione S-transferase (GST) and antioxidant enzymes, including total superoxide dismutase (T-SOD), peroxidase (POD), and catalase (CAT), in E. crus-galli seedlings were enhanced by the LF treatment; while POD activity decreased and GST, T-SOD, and CAT activity was not significantly altered by the HF treatment. The metabolomic and transcriptomic analyses showed that FA regulated E. crus-galli seedling growth by affecting the synthesis of indole derivatives and flavonoid compounds. Compared with the blank control (CK, 0 g L−1), the levels of four indole derivatives were upregulated under the HF treatment, and the indole derivatives were slightly downregulated under the LF treatment. The flavonoids, including naringenin, naringenin chalcone, eriodictyol, kaempferol, and epigallocatechin, were downregulated under HF treatment, and the growth of E. crus-galli was reduced. In contrast, the metabolism and transcription of flavonoids were not significantly altered by the LF treatment. The addition of 0.80 g L−1 FA obviously inhibited the growth of newly sprouted E. crus-galli, whereas rice growth was significantly promoted 8 d after rice planting (P < 0.05). The application of FA, therefore, might be a potential integrated weed management method to control the damage caused by E. crus-galli in paddy fields.

Barnyardgrass [Echinochloa crus-galli(L.) P. Beauv] is the foremost weed in rice (Oryza sativaL.) systems, and its control is crucial to successful rice production. Quinclorac, a synthetic auxin herbicide, has been used effectively to manageE. crus-galli. However, occurrences of quinclorac-resistant genotypes are frequently reported, and its resistance evolution has led to questions about the continued utility of quinclorac for grass control. Identification of the resistance mechanism(s) of resistant genotypes will facilitate development of integrated weed management strategies that sustain quinclorac use for management ofE. crus-galli. We evaluated the responses to quinclorac of two contrasting genotypes: E7 (resistant, R) and LM04 (susceptible, S). Quinclorac induced ethylene and cyanide biosynthesis in the S-genotype. Both genotypes responded similarly to an increasing application of exogenous 1-carboxylic acid aminocyclopropane (ACC) and potassium cyanide, and their growth was inhibited at higher doses. The key mechanism for cyanide (HCN) detoxification in plants, β-cyanoalanine synthase (β-CAS) activity, was evaluated in both genotypes, and no significant difference was observed in the basal activity. However, quinclorac significantly induced β-CAS–like activity in the S-genotype, which is consistent with the increased synthesis of ethylene and cyanide. This work suggests that the resistance to quinclorac of the E7 R-genotype is likely related to an alteration in the auxin signal transduction pathway, causing a lower stimulation of ACC synthase and, therefore, limited synthesis of ethylene and HCN after quinclorac treatment.

DOR: 98.1000/2383-1251.1398.6.151.12.2.1575.41 Extended abstract Introduction: Due to their aggressive and competitive habits, weeds inhibit the growth of valuable plants. Interference in plants includes environmental competition and allelopathy (Autotoxicity and hetrotoxicity). In hetrotoxicity, chemical compounds released from plants are able to effect the neighboring plants. Proper management of weeds and the exploitation of their hetrotoxicity potential can reduce losses caused by weeds. This could also represent an effective step towards the reduction of the use of herbicides. Therefore, the purpose of this study was to evaluate the effect of hetrotoxicity potential of aqueous extract of various organs of Malva sylvestris L. weed on traits of germination and photosynthetic pigments of Echinochloa crus-galli L. Material and Methods: An experiment was conducted to evaluate the effect of hetrotoxicity potential of aqueous extract of Malva sylvestris L. weed including the stem, leaf and flower as well as their mixture on traits of germination and photosynthetic pigments of Echinochloa crus-galli L. as a completely randomized design in three replications in Weeds Science Laboratory of Gonbad Kavous University in 2017. For this experiment, aerial parts of M. sylvestris were first collected at the flowering stage from Ramian field. They were subsequently separated with great care and were powdered. Then from them, 5% suspensions (weight/volume) were prepared, using distilled water. Finally, the extract of each organ of M. sylvestris was added to Petri dishes containing E. crus-galli seeds. After the 7th day, traits such as rate and percentage of germination, radical and shoot elongation, vigor index, total content of chlorophyll a and b and carotenoids were measured. Results: The results showed that various organs of M. sylvestris and their mixture had different inhibitory effects on traits of germination and seedling length of E. crus-galli weed. The highest inhibition effects on rate and germination percentage and elongation of radical and shoot of E. crus-galli were obtained using leaf extract of M. sylvestris about 64.04, 64.37, 87.69, 62.81%. In this study, radical length is more affected under hetrotoxic compounds of various organs of M. sylvestris, as compared with shoot length. Based on the results, various organs of M. sylvestris and their mixture also have different inhibitory effects on chlorophyll and carotenoid content of E. crus-galli weed. It seems that the differential effects among different organs of M. sylvestris are a function of the threshold concentration of allelochemicals to hetrotoxic compounds of the organs, which causes various response by E. crus-galli. Conclusion: Given the evidence for the effect of hetrotoxicity potential of various organs of M. sylvestris on traits of germination and pigments of chlorophyll and carotenoid of E. crus-galli and huge biomass generated, it is advisable to exploit allelochemical compounds of this plant as bio-herbicides. Highlights: 1- Study of the the effect of hetrotoxic potential of Malva sylvestris weed on germination characteristics and photosynthetic pigments of Echinochloa crus-galli in Ramian field. 2- E. crus-galli weed exhibits great sensitivity to hetrotoxic compounds of various organs of M. sylvestris, especially the leaves. 3- Allelopathic characteristics of M. sylvestris weed have huge potentials for the production of bio-herbicides.

The present study was aimed at investigating the allelopathic effects of a crude extract from Chromolaena odorata (L.) R.M.King and H.Rob. (Siam weed). The effects of 70% crude ethanol extract from the whole plant, leaf, stem, and root on the germination and growth of Echinochloa crus-galli and Amaranthus viridis seedlings were evaluated using Petri-dish tests under laboratory conditions. Crude extracts from the leaf showed the highest inhibitory activity. The leaf extract (OR) was further separated by sequential solvent extraction to provide hexane (HX), ethyl acetate (ET), and butanol (BU) fractions, which were also evaluated using Petri-dish tests. The hexane fraction was significantly the most active, therefore, it was selected for formulation in a concentrated suspension and tested for its herbicidal characteristics. The formulation showed greater early post-emergence than post- and pre-emergence activities, respectively. The physiological mechanism of the formulation was tested against E. crus-galli and showed that chlorophyll a and b and the carotenoid contents of the leaf dramatically decreased when the concentration was increased, suggesting its ability to disrupt the process of photosynthesis. As thiobarbituric acid reactive substances also occurred in the leaf of E. crus-galli, this suggests lipid peroxidation and cell disruption. These results represent the possibility that C. odorata extract contains inhibitory compounds with herbicidal activity and could be used as an early post-emergence herbicide for weed control.

A better understanding of weed seed production is a key element for any long-term management allowing some weeds to shed seeds. The challenge with measuring seed production in weeds is the large effort required in terms of time and labour. For the weed species Echinochloa crus-galli, it was tested whether the number of seeds per panicle dry weight or per panicle length can be used to estimate seed production. Experiments were conducted in three maize fields in north-eastern Germany. The effect of factors that could influence this relationship, such as the time of seedling emergence, the density of E. crus-galli, the control intensity of other weeds, seed predation and field, was included. A few days before maize harvest, all panicles were removed and weighed, panicle length was measured, and for a subsample of 178 panicles, the number of seeds was counted manually. Panicle dry weight predicted the number of seeds per panicle better (R2 = 0.92) than did panicle length (R2 = 0.69). The other factors except for ‘field’ and ‘seed predation’ had no effect on these relationships. The relationships between seed number and panicle dry weight found in this study closely resembled those reported in an earlier study. Based on our results, we conclude that both plant traits are appropriate for the estimatation of seed production, depending on required level of precision and availablilty of resources for the evaluation of sustainable weed management strategies.

Echinochloa crus-galli is a major weed in rice fields in China, and quinclorac has been long used for its control. Over-reliance of quinclorac has resulted in quinclorac resistance in E. crus-galli. Two resistant (R) E. crus-galli populations from Hunan, China were confirmed to be at least 78-fold more resistant to quinclorac than the susceptible (S) population. No difference in foliar uptake of 14C-labelled quinclorac was detected between the R and S plants. However, a higher level of 14C translocation and a lower level of quinclorac metabolism were found in the R plants. Basal and induced expression levels of β-cyanoalanine synthase (β-CAS) gene and β-CAS activity were not significantly different between the R and S plants. However, the induction expression of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO1) gene by quinclorac treatment was evident in the S plants but not in the R plants. Quinclorac resistance in the two resistant E. crus-galli populations was not likely to be related to foliar uptake, translocation or metabolism of quinclorac, nor to cyanide detoxification via β-CAS. Thus, target-site based quinclorac signal reception and transduction and regulation of the ethylene synthesis pathway should be the focus for further research. Keywords: Echinochloa crus-galli, Quinclorac resistance, Quinclorac metabolism, β-cyanoalanine synthase, 1-aminocyclopropane-1-carboxylic acid synthase, 1-aminocyclopropane-1-carboxylic acid oxidase, Rice

Barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is one of the most troublesome and competitive weed species in rice (Oryza sativa L.) grown under conventional flood (FLD) irrigation and is expected to be similarly damaging under alternate-wetting-and-drying (AWD) irrigation. Several indica rice genotypes have been shown to suppress E. crus-galli under FLD management, but very little is known about the nature and potential of weed suppression using AWD irrigation. In this 3-yr field study, we evaluated seven diverse rice genotypes for their weed suppression and grain yield potential under FLD and AWD irrigation. The E. crus-galli dry biomass at midseason was 11% less under AWD compared with FLD. Overall, plots of an indica variety and a hybrid resulted in less E. crus-galli dry biomass under AWD compared with FLD. Grain yield in weed-free AWD plots averaged 12% less than in weed-free FLD plots. Grain yield of the tropical japonica (TRJ) type, ‘Bengal’, was 32% lower under AWD than FLD, whereas grain yields of the two indica genotypes, PI 312777 and ‘Rondo’, and a hybrid were similar in both irrigation systems. Grain yield reduction in E. crus-galli–infested AWD plots averaged greater than 90%. Thus, E. crus-galli greatly reduced the grain yield of all rice genotypes tested in both FLD and AWD systems in this study. Grain yield of the indica and hybrid genotypes was relatively less affected by the AWD treatments compared with the TRJ genotypes, particularly with Bengal, suggesting that the weed-suppressive genotypes, PI 312777 and Rondo, would be better suited to AWD irrigation systems and for inclusion in weed-suppression rice-breeding programs in the southern United States.

Competition for shared above-ground (e.g. light) and below-ground (e.g. water and nutrients) resources among neighbouring plants is one of the main processes that affect cropping systems. This study aimed to evaluate the effects of weed shading on growth and yield production of bean plants when grown in weedy condition without below-ground competition. The experiments were organized as a split plot design with three replications. The main plots consisted of the nitrogen application rates including of 0, 70, 140 and 280 kg N ha−1 and the sub plots consisted of barnyardgrass densities including 0 (D0), 2 (D2) and 20 (D20) plants m−2. The N application rates were 0 (N0), 25 (N25), 50 (N50), 100% (N100) and 200% (N200) of the recommended N rate on the basis of seed yield goal. Biomass of common bean decreased by 30% for N0, 41% for N50, 35% for N100 and 38% for N200, as weed pressure increased from D0 to D20.. Mean reduction in 100-seed weight, seed number and seed yield caused by high weed pressure was 11, 20 and 41% compared with weed free, respectively. The weed biomass and N uptake increased by 66 and 159% as the nitrogen dose increased from N0 to N200. The highest biomass and N uptake was obtained from N200 treatment. We conclude that agronomically optimum N rates for seed yield was obtained at 140 kg N ha−1 within the range of N fertilization rates used across all weed pressure levels.

Alternative irrigation systems are viable options to reduce water footprint in rice; however, it could increase the difficulty of controlling weeds, as the water layer prevent weed emergence. Despite the environmental importance, there is no knowledge regarding effective chemical control of Echinochloa crus-galli (L.) P. Beauv. under contrasting field layouts and irrigation systems in dry-seeded rice. In this study, we quantified the efficacy of some pre-emergence (PRE) and post-emergence (POST) herbicide sequences and tank mixtures to control E. crus-galli under continuous and intermittent irrigation at two different field layouts. The experiment was conducted during three growing seasons between 2012 and 2014, in two edaphoclimatic regions of Uruguay. The rice yield was directly related to the efficacy of controlling of E. crus-galli at flowering (R2 ≈ 0.60). The efficacy of chemical options to control E. crus-galli was not affected by the irrigation or the field layout system. Clomazone PRE followed by penoxsulam was the most effective option (80% weed control). The results suggest that chemical options are available to control E. crus-galli when applying alternative field layout and irrigation systems that promote improved water efficacy in rice. We expect this new approach to control E. crus-galli be useful in reducing water needs, and hence making rice production more sustainable.

Barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is acknowledged to be the most troublesome weed in rice fields in Anhui and Jiangsu provinces of China. It cannot be effectively controlled using certain acetolactate synthase (ALS)-inhibiting herbicides, including penoxsulam. Echinochloa crus-galli samples with suspected resistance to penoxsulam were collected to identify the target site–based mechanism underlying this resistance. Populations AXXZ-2 and JNRG-2 showed 33- and 7.3-fold resistance to penoxsulam, respectively, compared with the susceptible JLGY-3 population. Cross-resistance to other ALS inhibitors was reported in AXXZ-2 but not in JNRG-2, and occasionally showed higher sensitivity than JLGY-3. In vitro ALS activity assays revealed that penoxsulam concentrations required to inhibit 50% of ALS activity were 11 and 5.2 times greater in AXXZ-2 and JNRG-2, respectively, than in JLGY-3. DNA and predicted amino acid sequence analyses of ALS revealed Ala-205-Val and Ala-122-Gly substitutions in AXXZ-2 and JNRG-2, respectively. Our results indicate that these substitutions in ALS are at least partially responsible for resistance to penoxsulam.

Laboratory analyses using the 1st generation bioassay were conducted in the years 2013-2014 to investigate the allelopathic potential of wateralcoholic and aqueous extracts from dry weight of rhizomes and roots as well as stems and leaves of Solidago gigantea. Analysed acceptors were two weed species, i.e. monocotyledonous Echinochloa crus-galli and dicotyledonous Amaranthus retroflexus. When the acceptors (E. crus-galli and A. retroflexus) reached the 2-leaf stage (BBCH 12) they were sprayed with wateralcoholic and aqueous extracts (at concentrations of 12.5%, 10%, 5% and 2.5%) obtained from the donor, i.e. S. gigantea. Results indicate an inhibitory effect of wateralcoholic extracts from aboveground parts (leaves and stems) of S. gigantea in relation to dry weight of E. crus-galli and A. retroflexus. The volume of dry weight reduction in acceptors was dependent on the concentration of extracts produced from the donor plant S. gigantea. Dry weight of E. crus-galli and A. retroflexus was reduced most effectively by two concentrations: 12.5% and 10%. In turn, aqueous extracts from rhizomes and roots of S. gigantea, irrespective of the applied concentration, caused an increase in dry weight of E. crus-galli and A. retroflexus. Only aqueous extracts produced from leaves and stems of S. gigantea, irrespective of their concentration, reduced dry weight in only E. crus-galli., W badaniach laboratoryjnych przeprowadzonych z użyciem biotestu I generacji w latach 2013-2014, porównywano potencjał allelopatyczny wyciągów wodnoalkoholowych oraz wodnych uzyskanych z suchej masy kłączy i korzeni oraz łodyg i liści Solidago gigantea. Akceptorami były dwa gatunki chwastów: jednoliścienny Echinochloa crus-galli oraz dwuliścienny Amaranthus retroflexus. W monecie uzyskania przez akceptory (E. crus-galli i A. retroflexus), fazy 2 liści właściwych wykonano oprysk wyciągiem wodno-alkoholowym oraz wodnym, o stężeniu 12,5%, 10%, 5% i 2,5%, otrzymanym z donora, którym było S. gigantea. Uzyskane wyniki badań wskazują na efekt inhibicyjnego odziaływania wyciągów wodno-alkoholowych sporządzonych z nadziemnych części roślin (liści i łodyg) S. gigantea w odniesieniu do suchej masy E. crus-galli oraz A. retroflexus. Wielkość redukcji suchej masy akceptorów uzależniona była od stężenia wyciągów sporządzonych z rośliny donorowej S. gigantea. Najefektywniej suchą masę E. crus-galli oraz A. retroflexus redukowały dwa stężenia: 12,5% oraz 10%. Natomiast wyciągi wodne sporządzone z kłączy i korzeni S. gigantea, niezależnie od zastosowanego stężenia, powodowały zwiększenie suchej masy E. crus-galli oraz A. retroflexus. Jedynie wyciągi wodne otrzymane z liści i łodyg S. gigantea, niezależnie od stężenia, powodowały redukcję suchej masy E. crus-galli.

The aim of the study was to evaluate the occurrence and development of weed species as actual weed infestation of maize in sustainable farming systems. The specific goals of the study were to assess the dynamics of occurrence of each weed species in integrated and ecological farming systems, and to evaluate the impact of farming system, manure or fertiliser application and year on the presence of weeds in maize stands from 2014 to 2016. In the integrated non-fertilised maize cropping system, the following weed species were dominant in the spring: Amaranthus retroflexus, Cirsium arvense, Chenopodium album, Persicaria maculosa and Echinochloa crus galli. In the integrated fertilised maize cropping system, the following weed species were dominant in the spring: Amaranthus retroflexus, Chenopodium album, Cirsium arvense, Echinochloa crus galli, Convolvulus arvensis and Cardaria draba. In the integrated maize cropping system, Silybum marianum occurred as a weed at medium density. Silybum marianum was cultivated two years ago and its seeds were in a state of dormancy for that time. The efficacy of the herbicide treatment in the integrated system was excellent. In the ecological non-fertilised maize cropping system, the following weed species were dominant in the spring: Amaranthus retroflexus, Chenopodium album, Cirsium arvense, Avena fatua and Sonchus oleraceus. In the ecological fertilised maize cropping system, the following weed species were dominant in the spring: Amaranthus retroflexus, Chenopodium album, Echinochloa crus galli, Avena fatua, Persicaria maculosa, Cirsium arvense and Convolvulus arvensis. In the ecological farming system, due to insufficient mechanical weed control, a higher level of maize infestation with Avena fatua as an annual grass weed species was detected.

Echinochloa crus-galli (L.) Beauv. and Echinochloa colona (L.) Link have ranked as the world’s third and fourth worst weeds, respectively. They infest several crops in several countries causing a significant reduction in crop production and necessitating to undertake appropriate management measures. They cooccur and are most dominant in rice agroecosystems across the globe. However, E. colona tends to dominate in rainfed agriculture. The plasticity in morphology, phenology, rapid growth, prolific seed production, seed dormancy, and adaptability to a wide range of environments contribute to the success of these species in agroecosystems. The herbicides continue to play a major role in managing both species. The heavy reliance upon and repeated use of herbicides in crops have led to the evolution of herbicide resistance, in both Echinochloa species, whereas E. crus-galli was included as one of the world’s most serious herbicide-resistant weeds. To mitigate rapid resistance evolution under the changing climate, the herbicides must be used in rotations and integration with other nonchemical methods. The development and implementation of location-specific integrated weed management strategies would help in the sustainable management of these two problematic weed species.

Echinochloa crus-galli (L.) P. Beauv. is the most common monocotyledonous weed in maize crops in Croatia. Crop–weed interference is influenced by weed emergence patterns, and knowledge of the timing of weed emergence is crucial for the development of an efficient integrated weed-management program. Therefore, two-year field experiments were conducted in a maize crop sown in early May in continental Croatia to determine the emergence pattern of E. crus-galli from natural seedbank. In laboratory studies, the estimated base temperature and base water potential for the Croatian ecotype of E. crus-galli were 10.8 °C and −0.97 MPa, respectively. Then, the estimated germination parameters were compared with the values embedded in the AlertInf model from Italy (Veneto) to calibrate this hydrothermal model. The estimated hydrothermal units were around 28 for the onset (10%) and 93 for the middle (50%) emergence of E. crus-galli. Our findings showed that the AlertInf model satisfactorily simulated the emergence of E. crus-galli in maize crop in Croatia (EF = 0.97 in 2019 and 0.98 in 2020), indicating its potential use in other geographical areas

The genus Echinochloa (Poaceae) includes orphan crops and important agricultural weeds. Here, we assembled the complete chloroplast genome of a diploid Echinochloa species (E. haploclada). The chlo...

The hexaploid species Echinochloa crus-galli is one of the most detrimental weeds in crop fields, especially in rice paddies. Its evolutionary history is similar to that of bread wheat, arising through polyploidization after hybridization between a tetraploid and a diploid species. In this study, we generated and analyzed high-quality genome sequences of diploid (E. haploclada), tetraploid (E. oryzicola), and hexaploid (E. crus-galli) Echinochloa species. Gene family analysis showed a significant loss of disease-resistance genes such as those encoding NB-ARC domain-containing proteins during Echinochloa polyploidization, contrary to their significant expansionduring wheat polyploidization, suggesting that natural selection might favor reduced investment in resistance in this weed to maximize its growth and reproduction. In contrast to the asymmetric patterns of genome evolution observed in wheat and other crops, no significant differences in selection pressure were detected between the subgenomes in E. oryzicola and E. crus-galli. In addition, distinctive differences in subgenome transcriptome dynamics during hexaploidization were observed between E. crus-galli and bread wheat. Collectively, our study documents genomic mechanisms underlying the adaptation of a major agricultural weed during polyploidization. The genomic and transcriptomic resources of three Echinochloa species and new insights into the polyploidization-driven adaptive evolution would be useful for future breeding cereal crops.

Barnyardgrass (Echinochloa crus-galli) is one of the most problematic weeds on rice crop. The research was to evaluate the response of several barnyardgrass biotypes from Greece to profoxydim and evaluate the role of different rates and growth stages on the overall effectiveness. Three experiments were conducted in 2018. The response of the several biotypes had high variability (20-100%), with the most susceptible biotypes originating from regions in which crop rotation is a common practice (Fthiotida). Moreover, dose-response experiments showed that the rate of profoxydim required to adequately control the resistant population G17 was 4-times higher than the maximum recommended dose. Concerning the phenology effect on profoxydim effectiveness, This study revealed a higher efficacy at the earlier growth stage BBCH 13 (15-50% higher than growth stages BBCH 22 and 30), probably it was due to the smaller size and the higher growth rate of the younger plants. Consequently, the significant effect of weed growth stage on the effectiveness of profoxydim implies that application of the herbicide at earlier growth stages could optimize herbicide use and result in a better control with the condition of avoidance crop injuries.

Salinity is one of the major abiotic stresses that may affect yield and quality of crops. Salinization, in combination with the presence of aggressive weeds, such as barnyard grass (Echinochloa spp.), can be considered one of the factors responsible for reducing yield in rice fields. The aims of the study were to evaluate the salt effect on germination and first seedling growth of six different Italian common barnyard grass (E. crus-galli) populations (three sensitive and three resistant to ALS-inhibitor herbicides) and to verify the presence of differences in salt response between populations sensitive and resistant to the ALS-inhibitor herbicides. Germination tests were conducted under nine different NaCl concentrations (from 0 mM to 400 mM). Significant differences in germination capacity were found between sensitive and resistant populations from 0 mM to 250 mM NaCl; in particular, germination capacity of the sensitive populations was higher (up to 90%) than that of the resistant ones (about 70%). The increase in salinity over 250 mM reduced progressively the germination capacity: from 300 mM onwards, no significant differences were found between sensitive and resistant populations and the germination resulted inhibited for two of them (one sensitive and one resistant). Speed of germination and root and shoot length of seedlings were also inversely related to salt concentration. Time required for achieving 50% of final germination capacity was extended from about three days at 0 mM NaCl up to about 10-12 days at 400 mM NaCl. Root length and shoot length ranged from 9.88 cm and 6.16 cm, at 0 mM NaCl, to 0.36 cm and 0.41 cm, at 400 mM NaCl. According to the results, there is no a clear evidence that response to saline conditions was related to resistance towards ALS-inhibitor herbicides, as in some cases significant differences were found between populations showing a similar herbicide sensitivity. Responses of barnyard grass to salinity are may play a role in the importance of this weed in future scenarios of salt intrusion: for example, a lower speed of germination at increasing salt levels could suggest a delayed emergence of this weed during crop establishment and first growth. To evaluate the real consequences in terms of competitions towards the crop, future studies are needed for assessing the response to salinity of the main rice varieties cultivated in the environment in which the E. crus-galli populations tested in this study were collected.

Barnyardgrass (Echinochloa crus-galli) seed samples were collected in rice fields in different locations at Mekong delta in Vietnam for herbicide resistance tests. The ALS-resistant and synthetic auxin-resistant E. crus-galli were confirmed at several locations in the Mekong Delta. The average LD90 value of bispyribac, penoxsulam and quinclorac for assessed weed populations was 33.1, 15.1 and 550.2 g a.i.ha−1 respectively. There were cross resistant barnyardgrass populations to bispyribac and penoxsulam, the LD90 value of the two ALS inhibitors for E. crus-galli was positively correlated at R2=0.39, the cross resistant population was 33.3% of total sample. The correlation analysis was not useful to evaluate the multiple resistance between quinclorac and the two ALS inhibitors, the R2 value was lower than 0.05, however, the percentage of multiple resistance weed was 36.2% of population. There was no cross resistance or multiple resistance among the 3 tested herbicides and the new synthetic auxin herbicide Rinskor™. All tested weed samples, including quinclorac-resistant populations, were effectively controlled by Rinskor™. There was no difference between control from Rinskor™ in the different herbicide resistant populations. Average LD90 value of Rinskor™ in all tested barnyardgrass was 17.1 g a.i ha−1.

Different weeding frequencies (WFs)―0WF, 2WF, 4WF, 6WF, and 8WF―were adopted in an organic rice field to investigate their influence on weed types, rice and weed biomass, rice tiller and weed number, N concentration, and N uptake. The study field was located in Tsuruoka, Yamagata, Japan. Rice (cv. Sasanishiki) was planted from May to September 2019, and all weeding events were carried out until 49 days after transplantation (DAT) using a rotary weeder. Rice and weed samples were collected at 60, 88, and 110 DAT. Echinochloa crus-galli (E. crus-galli), Schoenoplectus juncoides, and Monochoria vaginalis (Burm. f.) were the most commonly found weeds. High weed diversity was observed at both 6WF and 8WF, E. crus-galli was the dominant weed at 0WF. Compared to 0WF, 2WF displayed a significantly decreased weed biomass. However, at 8WF, the weed biomass was reduced by 79.0%, the rice biomass was increased by 277%, and the rice tiller number was almost three times higher than that at 0WF and 110 DAT. Compared to 0WF, a significantly increased rice N uptake was observed at 4WF, and rice N uptakes achieved at 6WF and 8WF were two and four times higher than those at 0WF, respectively. Higher weeding frequencies provide notable benefits in suppressing weeds and supporting rice growth, especially in N uptake competition with weeds.

Managing weed seed production may help in reducing weed emergence and biomass in successive seasons in dry-seeded rice. Field experiments were conducted in 2012 and 2013 to ascertain the effect of delayed weed emergence, i.e., 0, 14, 28, 42, 56, and 70 days after sowing (DAS) on seed production ability of Digitaria ciliaris and Echinochloa crus-galli in two rice cultivars (PR115 with 125 days duration and PR114 with 145 days duration). Emergence of E. crus-galli was similar in both the cultivars, except at 42 DAS, where the emergence was higher in PR114 than PR115 during 2012. In PR114, D. ciliaris continued to emerge up to 56 DAS, although the increase was significant up to 28 DAS; the increased emergence of this weed was noticed up to 14 DAS in PR115. Weed biomass was also higher in PR114, although the rate of the decrease with respect to emergence time was similar in both the rice cultivars. D. ciliaris, when emerged with the crop, produced 11,820 seeds per plant in PR114, but seed production reduced by 25% in PR115. However, differences in seed production of E. crus-galli were noticed when this weed emerged between 14 and 42 DAS. An exponential model predicted that, for a 99% reduction in seed production of D. ciliaris, 42–45 days of crop advancement, while, for E. crus-galli, 21–33 days of crop advancement was required. Our study suggests that delaying the weed emergence in the crop and/or adopting better competitive rice cultivars can reduce the weed seed production substantially.

Two field experiments were conducted at Rice Research and TrainingCenter, Sakha, Kafr El-Sheikh, Egypt during 2015 and 2016 seasons to detect the effect of water regime and weed control treatments on weeds, growth and yields of hybrid rice (Sk2034H). Water regime (4-days on and 6-days off, saturation and continuous flooding) were allocated in main plots while weed control treatments were Thiobencarb 50% EC at three rates; 1.8 , 2.4 and 3.6 kg ai ha-1 in addition to weedy check were distributed in sub-plots. Weed species and hybrid rice yields were greatly influenced by water regime and weed control treatments. Echinochloa crus-galli and total weeds dry weights were significantly reduced under flooded or saturated plots than under shortage of water (4-days on + 6-days off). In different response, Cyperus difformis considerably reduced under the water shortage than saturated or flooded plots. The highest values of panicles per hill and grain yield of hybrid rice were recorded under flooding conditions followed by saturated soil. The application of Thiobencarb 50% EC at the high rate (3.6 kg ai h-1) resulted in the best weed control and highest grain yield followed by the application of 2.4 kg ai ha-1 from the same compound, while weedy check plots recorded the highest in weed presence and the lowest in rice yields. For the interaction, the lowest dry weights of Echinochloa crus-galli, Cyperus difformis and total weeds, also the largest weed control efficiency (%), number of panicles per hill and the highest rice grain yields were obtained under flooded plots treated with Thiobencarb at both rates of 2.4 and 3.6 kg ai ha-1. This trend was true under all treatments even the weedy check plots except for Cyperus difformis which increased significantly by soil saturation or flooding in un-treated plots.

Harvest weed seed control is an alternative non-chemical approach to weed management that targets escaped weed seeds at the time of crop harvest. Relatively little is known on how these methods will work on species in the US. Two of the most prominent weeds in soybean production in the midsouthern US are Palmer amaranth and barnyardgrass. Typically, when crop harvesting occurs the weed seed has already either shattered or is taken into the combine and may be redistributed in the soil seedbank. This causes further weed seed spread and may contribute to the addition of resistant seeds in the seedbank. There is little research on how much seed is retained on different weed species at or beyond harvest time. Thus, the objective of this study was to determine the percentage of total Palmer amaranth and barnyardgrass seed production that was retained on the plant during delayed soybean harvest. Retained seed over time was similar between 2015 and 2016, but was significantly different between years for only Palmer amaranth. Seed retention did not differ between years for either weed species. Palmer amaranth and barnyardgrass retained 98 and 41% of their seed at soybean maturity and 95 and 32% of their seed one month after soybean maturity, respectively. Thus, this research indicates that if there are escaped Palmer amaranth plants and soybean is harvested in a timely manner, most seed will enter the combine and offer potential for capture or destruction of these seeds using harvest weed seed control tactics. While there would be some benefit to using HWSC for barnyardgrass, the utility of this practice on mitigating herbicide resistance would be less pronounced than that of Palmer amaranth because of the reduced seed retention or early seed shatter.

Post-emergent herbicides were evaluated in a series of field experiments for control of weeds in rice nursery as well as, direct seeded and transplanted rice during the kharif seasons of 2014 and 2015. Results of one of the studies showed that flucetosulfuron at 25-30 g ha-1 applied at 15-18 DAS (days after sowing) was effective for control of many broad-leaved weeds and some grass weeds [Echinochloa crus-galli (L.) Beauv.]. However, flucetosulfuron was not reasonably effective against major upland rice weeds namely Dactyloctenium aegyptium (L.) Willd and Digitaria sanguinalis (L.) Scop. infesting rice nursery and direct seeded rice (DSR). Under puddle transplanted rice (PTR) conditions, flucetosulfuron 25-30 g ha-1 applied at 15-19 days after transplanting had similar weed control levels and rice grain yields as obtained with bispyribac-Na at 20 g ha-1 and azimsulfuron at 35 g ha-1. However, in the DSR, weed control and rice grain yields with flucetosulfuron were poorer to that observed with application of azimsulfuron 35 g ha-1. In another field study, ready-mixture of penoxsulam + bentazone (1:36) at 840-1110 g ha-1 as post-emergent (18 DAS or 20 DAT) option was evaluated against weeds in DSR and PTR along with standard check herbicides, azimsulfuron 35 g ha-1, and cyhalofop-p-butyl 80 g ha-1. Penoxsulam + bentazone at 925-1110 g ha-1 was very effective for control of grass weed, E. crus-galli (98-100% control) and many broad-leaved weeds but was not effective against D. aegyptium and D. sanguinalis found in DSR. Consequently, the poor weed control (508-524 g m-2 total weed dry weight) with application of penoxsulam + bentazone combination at 925-1110 g ha-1 resulted in 1.45-1.48 t ha-1 lesser grain yield compared to azimsulfuron 35 g ha-1 (218.2 g m-2 total weed dry weight). Under puddle transplanted conditions, penoxsulam + bentazone combination and azimsulfuron 35 g ha-1 provided significantly better weed control than cyhalofop-p-butyl. The weed competition caused higher rice grain yield reductions in DSR (86-100%) than PTR conditions (25-52%). The results indicated azimsulfuron as better herbicide option for DSR than flucetosulfuron, penoxsulam, penoxsulam + bentazone and bispyribac-Na due to diverse weed flora control. Also, pot studies indicated that flucetosulfuron and azimsulfuron should be applied with cationic surfactant at 1000 ml ha-1 for better weed control efficacy. DOI: http://doi.org/10.25174/2249-4065/2019/96493

In greenhouse and controlled environment experiments, disease development and mortality of Echinochloa crus-galli, E. colona, and E. glabrescens caused by Exserohilum monoceras were affected by duration, frequency, and timing of dew period, as well as by dew-period temperature and post-dew temperature. When adequate dew was provided, 100% mortality occurred for all three Echinochloa spp. over the broad dew-period temperature range of 20 to 30°C. The effect of post-dew temperature on disease development varied with the initial dew period. The minimum dew period to achieve 100% mortality was 16 h for E. colona, 12 h for E. crus-galli, and 8 h for E. glabrescens. Increasing dew period enlarged the range of temperature for maximum efficacy, whereas the use of optimum dew-period temperature decreased the dew period requirement. Delaying the initiation of the dew period by 24 h did not adversely affect disease development. Increased disease development occurred for inoculated seedlings treated with repetitive dew periods of shorter duration than the optimal period. These findings characterize one of the epidemiological requirements, i.e., dew requirement, needed to assess the potential of E. monoceras for the control of Echinochloa spp. in rice.

Isolates of Colletotrichum graminicola were obtained from barnyard grass showing anthracnose symptoms and the fungus was evaluated as a potential biocontrol agent. C. graminicola KA001 was highly pathogenic to two varieties of barnyard grass in a wide range of growth stages, with the most damage at the three- to four-leaf stages. Disease severity of barnyard grass increased with the increase of the inoculum density from 1 × 104 to 1 × 105 conidia/ml, but inoculum density above 1 × 106 conidia/ml did not increase disease severity. A total of 13 rice cultivars tested showed no disease symptoms when inoculated with this fungus. Appressoria were formed on both barnyard grass and rice leaves, but infection hyphae were only found in the cells of barnyard grass. The fungus grew and sporulated in a wide range of temperature regimes, with optimal temperature at 27 to 30°C. These data suggest that C. graminicola KA001 has potential as a mycoherbicide to control barnyard grass with a safe selectivity in rice fields.

Since 2005, the evolution and spread of herbicide-resistant Echinochloa crus-galli biotypes have posed a serious threat to crop production in the Philippines. A comprehensive knowledge of E. crus-galli ecology and fecundity is fundamental in managing different biotypes of this weed. It was hypothesized that (a) high weed plant density produces more biomass and fertile seeds per unit area, (b) rice interference reduces the biomass and fecundity of the weed, and (c) a delay in weed emergence reduces the soil seed bank. In 2013, experiments were conducted in the wet season (WS) and dry season (DS), to understand the effect of E. crus-galli densities (40 and 80 plants m −2 ) on its growth, survival, and fecundity, with varying emergence times of 2, 15, 30, and 45 d after rice emergence (DARE). Relative to the weed plants grown without rice interference, E. crus-galli growth and seed production was lower in the presence of rice. Percent survival and plant height of E. crus-galli declined in a linear manner in the DS, and declined in a quadratic manner in the WS. Tiller number, inflorescence number, inflorescence biomass, and shoot biomass per plant declined in an exponential manner, with a delay in emergence of each cohort relative to rice. Across rice seeding rate, weed density, and emergence time, there was a linear relationship ( y = 110 x − 272 in the DS and y = 100 x − 220 in the WS) between E. crus-galli shoot biomass and the number of seeds plant −1 . Relative to the late-emerging weed cohorts, E. crus-galli seed production (1320–1579 seeds plant −1 ), 1000-seed weight (2.2–2.9 g), and seed yield (2808–2334 kg ha −1 ) were higher when seedlings emerged with the crop (2 DARE). None of the seedlings that emerged 45 DARE produced viable seeds. Seed germination of the first two cohorts (2 and 15 DARE) ranged from 84 to 91%. The delay in emergence of E. crus-galli beyond 30 DARE reduced the percentage of germinable and viable seeds, and increased the percentage of non-viable seeds produced plant −1 . The results suggest that cultural weed management approaches that delay the emergence of E. crus-galli can reduce weed biomass and seed production, and is thus valuable for preventing seed rain to the seed bank by noxious weed biotypes in the field.

Coumarin is a natural compound well known for its phytotoxic potential. In the search for new herbicidal compounds to manage weeds, three synthetic derivatives bearing the coumarin scaffold (1–3), synthesized by a carbonylative organometallic approach, were in vitro assayed on germination and root growth of two noxious weeds, Amaranthus retroflexus and Echinochloa crus-galli. Moreover, the synthetic coumarins 1–3 were also in vitro assayed on seedlings growth of the model species Arabidopsis thaliana to identify the possible physiological targets. All molecules strongly affected seed germination and root growth of both weeds. Interestingly, the effects of synthetic coumarins on weed germination were higher than template natural coumarin, pointing out ED50 values ranging from 50–115 µM. Moreover, all synthetic coumarins showed a strong phytotoxic potential on both Arabidopsis shoot and root growth, causing a strong reduction in shoot fresh weight (ED50 values ≤ 60 µM), accompanied by leaf development and a decrease in pigment content. Furthermore, they caused a strong alteration in root growth (ED50 values ≤ 170 µM) and morphology with evident alterations in root tip anatomy. Taken together, our results highlight the promising potential herbicidal activity of these compounds.

Summary Echinochloa crus-galli is an important maize weed withsignificant variation in herbicide sensitivity. This differ-ential response may reflect differences in selection pres-sure caused by years of cropping system-relatedherbicide usage. The herbicide sensitivity of E. crus-galli populations from three divergent cropping sys-tems was evaluated in dose–response pot experiments.Populations were collected from sandy fields with (i) along-term organic cropping system, (ii) a conventionalcropping system with maize in the crop rotation or(iii) a conventional cropping system with long-termmonocropping of maize. Each cropping system wasrepresented by six E. crus-galli populations. The effec-tiveness of three foliar-applied maize herbicides(nicosulfuron, cycloxydim and topramezone) and twosoil-applied maize herbicides (S-metolachlor and dime-thenamid-P) was tested at three doses and two runs.Foliar-applied herbicides were applied at the three trueleaves stage. Soil-applied herbicides were appliedimmediately after sowing. The foliage dry weight perpot was determined 4 weeks after treatment. Plantresponses were expressed as biomass reduction. Herbi-cide sensitivity was consistently lowest for populationsfrom maize monocropping systems. Compared withpopulations from organic cropping systems, popula-tions from monocropping systems showed 6.9%, 9.8%and 29.3% lower sensitivity to cycloxydim, topramez-one and nicosulfuron respectively. Populations fromthe conventional crop rotation system showed interme-diate sensitivity levels, which did not significantly dif-fer from sensitivity levels of populations from theother cropping systems. Sensitivity to dimethenamid-Pand S-metolachlor was not affected by cropping sys-tem. Environmental conditions influenced herbicidalresponse. This study indicated that integrated weedmanagement may be necessary to preserve herbicideefficacy over the long term.Keywords: barnyard grass, selection pressure, croprotation, monocropping, organic farming, maize.C

Biotypes of Echinochloa crus-galli var. formosensis with resistance to cyhalofop-butyl, an acetyl-CoA carboxylase (ACCase) inhibitor, have been found in dry-seeded rice fields in Okayama, Japan. We collected two lines with suspected resistance (Ecf27 and Ecf108) from dry-seeded rice fields and investigated their sensitivity to cyhalofop-butyl and other herbicides. Both lines exhibited approximately 7-fold higher resistance to cyhalofop-butyl than a susceptible line. Ecf108 was susceptible to penoxsulam, an acetolactate synthase (ALS) inhibitor. On the other hand, Ecf27 showed resistance to penoxsulam and two other ALS inhibitors: propyrisulfuron and pyriminobac-methyl. The alternative herbicides butachlor, thiobencarb, and bispyribac-sodium effectively controlled both lines. To examine the molecular mechanisms of resistance, we amplified and sequenced the target-site encoding genes in Ecf27, Ecf108, and susceptible lines. Partial sequences of six ACCase genes and full-length sequences of three ALS genes were examined. One of the ACCase gene sequences encodes a truncated aberrant protein due to a frameshift mutation in both lines. Comparisons of the genes among Ecf27, Ecf108, and the susceptible lines revealed that none of the ACCases and ALSs in Ecf27 and Ecf108 have amino acid substitutions that are known to confer herbicide resistance, although a single amino acid substitution was found in each of three ACCases in Ecf108. Our study reveals the existence of a multiple-herbicide resistant biotype of E. crus-galli var. formosensis at Okayama, Japan that shows resistance to cyhalofop-butyl and several ALS inhibitors. We also found a biotype that is resistant only to cyhalofop-butyl among the tested herbicides. The resistance mechanisms are likely to be non-target-site based, at least in the multiple-herbicide resistant biotype.

Climate change is predicted to result in rising temperatures which directly influence weed growth. Moreover, alterations in farming practice and variations in the timing of maize sowing affect weeds also indirectly. The main objective of this study was to establish the methodological concept of time-for-climate substitution for use in applied research. For this purpose, a semi-field experiment was conducted with the three important maize weeds Amaranthus retroflexus, Echinochloa crus-galli and Setaria viridis, which were cropped together with maize. In four treatments sowing of weeds was delayed in order to use naturally raising temperatures. This study focusses on late weed growth properties such as tillers, panicles, seeds and biomass as they allow important demographic conclusions for long-term weed population development. Over the season, temperature was continuously monitored with data loggers and growing degree days were calculated in order to relate the late growth properties to the climatic conditions the weeds experienced during early growth in the four treatments. The results from this study suggest that the tested weeds may benefit in two ways: (1) From warmer conditions during seedling emergence and early growth with enhanced vegetative growth and seed set; (2) from more growing degree days available as a result of earlier maize sowing and related extended cropping seasons. We conclude that our methodology is suitable to investigate climate change effects on weeds for applied questions. In order to limit weed growth and weed seed set under future conditions, management measures such as herbicide treatments at later growth stages and earlier harvest of maize should be explored. Furthermore, we suggest that functional relationships between late weed growth properties such as fecundity and different climatic conditions can be used to improve the accuracy of demographic and bioclimatic models.

Barnyard grass (Echinochloa crus-galli (L.) P.Beauv) is a major C4 weed in rice fields. We aimed to explore a management strategy to reduce its competition with rice (Oryza sativa L.) (C3) in low-phosphorus (P) soil with varying soil moisture availability. Therefore, we investigated the effect of P placement at different depths. The main experiment was conducted in pots (15 cm diameter, 70 cm height) filled with P-deficient soil as a replacement series with different plant combinations (rice and barnyard grass monocultures; four plants per pot, and a mixture of rice and barnyard grass; two plants of each species per pot) with two P placement depths (0–5 and 15–20 cm from the soil surface) and three moisture treatments (continuous flooding - CF, alternate wetting and drying - AWD, and top soil drying - TSD from flowering). The pots were maintained until crop maturity. A rhizobox experiment supplemented the main experiment to study the root system plasticity during the initial growth stages (i.e., after 14 and 28 days of growth). Placement of P in a deeper soil layer (15–20 cm) reduced the growth and P uptake of barnyard grass by over 70 and 80 %, respectively, irrespective of the plant combination, and moisture treatments, while such reductions were not observed in rice. Reduced growth and P uptake of barnyard grass were associated with the arrested root elongation even from the very early growth stages failing to search for P applied to 15–20 cm soil layer. In contrast, root elongation of rice increased from early growth stages when P was applied at 15–20 cm soil depth and reached the P-supplied soil layer to ensure P uptake. Average root diameter decreased by 12 %, and the percentage fine root production (i.e., < 0.4 mm diameter) increased by 8 % when P was applied at 15–20 cm deep compared with those at 0–5 cm depth. Phosphorous placement at 15–20 cm soil depth reduced the competitive ability of barnyard grass over rice in P-deficient soils, irrespective of the soil moisture management method.

Summary The effects of herbicide dose on rice-weed competition were investigated to develop a combined model, which can be utilised to estimate an optimum herbicide dose for a given weed density in paddy rice cultivation. Field studies were conducted in Suwon for rice-Echinochloa crus-galli competition and Iksan for rice-Eleocharis kuroguwai during 2007. The competitive effect of the weeds E. crus-galli and E. kuroguwai decreased with increasing doses of flucetosulfuron and azimsulfuron, respectively, in the same manner as the standard dose–response curve. The combination of the rectangular hyperbolic model and the standard dose–response curve adequately described the complex effects of herbicide dose and weed competition on rice yield. Parameter estimates were used with the model to predict rice yield and estimate the doses of flucetosulfuron and azimsulfuron required to restrict rice yield loss caused by E. crus-galli and E. kuroguwai, respectively, to an acceptable level. For a rice yield of 5.0 t ha−1, the model recommended flucetosulfuron doses of 8.7, 13.4 and 20.1 g a.i. ha−1 when infested with E. crus-galli at 12, 24 and 48 plants m−2 respectively. For a rice yield of 5.2 t ha−1, the model recommended azimsulfuron doses of 3.9, 7.5 and 12.6 g a.i. ha−1 when infested with E. kuroguwai at 24, 48 and 96 plants m−2 respectively. The theoretical outputs of the combined model appear robust and indicate there are opportunities for reduced herbicide use in the field. These now require evaluation under field conditions.

Herbicide-resistant barnyardgrass has become widespread in the rice production systems of the midsouthern United States, leaving few effective herbicide options for controlling this weed. The acetolactate synthase (ALS)- and acetyl-CoA carboxylase (ACCase)-inhibiting herbicides remain largely effective in Clearfield®rice production, but strategies need to be developed to protect the long-term utility of these options. A two-trait model was developed to understand simultaneous evolution of resistance in barnyardgrass to the ALS- and ACCase-inhibiting herbicides in Clearfield rice. The model was used to predict resistance under a number of common weed management scenarios across 1,000 hypothetical rice fields in the Mississippi Delta region and answer some key management questions. Under an ALS inhibitor–only program consisting of three annual applications of imidazolinone herbicides (imazethapyr or imazamox) in continuous Clearfield rice, resistance was predicted within 4 yr with 80% risk by year 30. Weed management programs that consisted of ALS- and ACCase-inhibiting herbicides such as fenoxaprop and cyhalofop greatly reduced the risk of ALS-inhibiting herbicide resistance (12% risk by year 30), but there was a considerable risk for ACCase resistance (evolving by year 14 with 13% risk by year 30) and multiple resistance (evolving by year 16 with 11% risk by year 30) to both of these mechanisms of action. A unique insight was that failure to stop using a herbicide soon after resistance evolution can accelerate resistance to the subsequent herbicide option. Further, a strong emphasis on minimizing seedbank size is vital for any successful weed management strategy. Results also demonstrated that diversifying management options is not just adequate, but diversity combined with timely herbicide applications aimed at achieving high efficacy levels possible is imperative.

The stimulation of seed germination by smoke and aqueous smoke extracts from the combustion of plant material has recently received a great deal of attention. This study was conducted to assess the effects of smoke on the weed species Echinochloa crus-galli (barnyard grass). Plant-derived smoke was produced from Bauhinia variegata using a newly designed furnace and then applied to the weed species. The results showed that plant-derived smoke solution significantly increased the germination rate (70–92.3%), germination percentage (31–47%), fresh weight (30–69%), shoot and root length (10–14.9%, 35–44%), germination index (50–100%) and vigour index (114–157%) of barnyard grass relative to the control. Treatment with plant-derived smoke solution also significantly reduced the endogenous abscisic acid of seeds, while α-amylase activity increased significantly compared to the control. Overall, these findings indicate that stimulation and quick emergence from a dormant soil seed bank of barnyard grass can be in...

The specific conditions in habitats in the immediate vicinity of roads provide a suitable environment for noxious weeds and invasive species that spread through them to the landscape. Echinochloa crus-galli and Digitaria sanguinalis are problematic weeds of wide-row crops. The field experiment focused on the impact of the roadside habitat salinization on the occurrence, growth and reproduction of these two species. Quantitative vegetative and generative characteristics of the plants were determined. Measurements were carried out at three distances from the edge of the road and on control plots. The results showed that the growth and reproduction of E. crus-galli and D. sanguinalis occur in the period when the values of soil environmental variables correspond to values of non-saline soil according to the criteria for soil salinity assessment. Despite this fact, the average salinity of soil along roadside was still higher than in soil of further distances and we found these levels of salinity to be well tolerated by the study species. Therefore, we conclude that roadsides with the same or higher salt content represent a suitable location for the occurrence and reproduction of E. crus-galli and D. sanguinalis, thus being temporary locations that enable their further spreading to the countryside.

Natural, essential oil-based emulsions could be in future an alternative for synthetic herbicides. In this study, the possibility that foliar-applied caraway or peppermint essential oils (EO) can selectively inhibit the growth of Echinochloa crus-galli (L.) P. Beauv. (barnyardgrass, a typical maize weed) but not that of maize plants was tested, in attempt to develop an eco-friendly botanical herbicide. The phytotoxic potential of oil-in-water emulsions of each EO with addition of commercial adjuvant, mainly composed of fatty acids methyl esters, was examined. Their effect on visible plants injuries, biomass accumulation, chlorophyll a fluorescence and changes to biochemical patterns of both the main crop (maize) and barnyardgrass via an untargeted metabolomic approach were studied. It was found that oil-in-water emulsion containing 2.5% of adjuvant and of caraway EO did not affect significantly the growth of maize plants, did not induce foliar symptoms and did not alter the status of the photosynthetic apparatus, as revealed by chlorophyll a fluorescence. On the contrary, this emulsion exerted significantly negative effects against barnyardgrass growth, inducing foliar injuries and reducing the photosynthetic efficiency of photosystem II. It was also found that the studied emulsions caused a series of biochemical changes in the plant tissues, with caraway emulsion being more phytotoxic, as compared to the peppermint EO-emulsion. In conclusion, oil-in-water emulsion containing 2.5% of caraway EO could be used in future as a foliar-applied botanical herbicide against barnyardgrass in maize cultivation.

Direct-seeded rice systems are increasing in Asia as farmers respond to the high labor cost and shortage of water. Echinochloa crus-galli is one of the most problematic and competitive weeds in direct-seeded rice systems. Because of concerns about excessive herbicide use, there is an interest in developing cultural weed management strategies. However, the design of such strategies requires a better understanding of the weed response to crop density, nutrition, and water regime. A study was therefore conducted in pots to determine the effect of water (flooded and aerobic), nitrogen (N) fertilization (0, 100, and 200 kg N ha −1 ), and rice density [0, 4 rice plants (≈20 kg seed ha −1 ), and 16 rice plants (≈80 kg seed ha −1 )] on the growth and reproduction of E. crus-galli . When grown alone, the growth and seed production of E. crus-galli were higher in flooded conditions than in aerobic conditions. However, no such differences were observed when E. crus-galli was grown with rice interference. E. crus-galli growth and seed production increased with increases in N rate. Irrespective of water regime and N rate, the growth and seed production of E. crus-galli declined with increases in rice density. At 100 kg N ha −1 , for example, E. crus-galli shoot biomass and seed production decreased by 84–86% and 82–87%, respectively, when grown with 16 rice plants compared with its growth without rice interference. The results suggest that growth and seed production of E. crus-galli can be greatly reduced by increasing rice seeding rate. However, there is a need to involve other weed management strategies to achieve complete control of E. crus-galli and other weed species.

During the 2006/07 and 2008/09 growing seasons in Southern Brazil, we evaluated crop selectivity and weed control efficacy of clomazone on rice when applied alone or in a mixture with other pre- and post-emergence herbicides (BRS Querencia variety). All herbicide treatments caused some degree of rice injury during both years; however, in no case was the injury still visible 21 days after application. Rice injuries were observed when application rates exceeded the recommended dose, and particularly when the herbicide was applied pre-emergence. Density reduction and panicle sterility served as measures of rice injury. Echinochloa crus-galli was the primary weed; it reduced rice yields by approximately 50% compared treated plots. In both growing seasons, clomazone herbicide (400 g ai ha−1) controlled the weed 87.0%–99.6%, and it provided 8.06 t ha−1 to 9.44 t ha−1 of rice yield.

Alternatives to commercial chemical herbicide are currently being searched and tested due to the numerous adverse effects of commercially available herbicides to the environment. Barnyardgrass (Echinochloa crusgalli) is an important weed species around the world, especially in paddy rice fields. This study focuses on the favorable effects of mixing pyroligneous acids with commercial liquid herbicides. Seedlings were transplanted and grown under greenhouse conditions. The effect of treatment time or leaf-stage on herbicide-pyroligneous acid efficacies was checked, coupled with isolation and quantification of biochemical compounds. Results revealed that herbicide treatment at early post emergence (2~3 leaf stage) of Echnochloa crus-galli leads to effective control. Both liquid herbicides affected fatty acid, protein, and amino acid syntheses as reflected on their contents. The influence of wood vinegar (WV) or rice vinegar (RV) on these compounds was not thoroughly verified due to lack of information on the pyroligneous products. We observed that mixing WV or RV with BCB (bentazone + cyhalof-butyl) gives more favorable results than BUC (butachlor + clomazone), mixed with WV or RV. The result would indicate the potential of mixing pyroligneous acid in reducing herbicide application rate.

Abutilon theophrasti and Barnyardgrass (Echinochloa crus-galli) are major weeds that affect cropping systems worldwide. Laboratory and greenhouse studies were conducted to determine the effects of temperature, pH, water and salinity stress, and planting depth on seed germination and seedling emergence of Velvetleaf and Barnyardgrass. For Velvetleaf, the base, optimum and ceiling germination temperatures were estimated as 5, 35 and 48 ºC, respectively. Seed germination was sensitive to drought stress and completely inhibited by a potential of -0.6 MPa, but it was tolerant to salinity. Salinity stress up to 45 mM had no effect on the germination of Velvetleaf, but germination decreased with increasing salt concentration. Drought and salinity levels for 50% inhibition of maximum germination were -0.3 MPa and 110 mM, respectively. Seed germination of Velvetleaf was tolerant to a wide range of pH levels. For Barnyardgrass, the base, optimum and ceiling germination temperatures were estimated as 5, 38 and 45 ºC, respectively. Seed germination was tolerant to drought stress and completely inhibited by a potential of -1.0 MPa. Salinity stress up to 250 mM had no effect on seed germination. Drought and salinity levels for 50% inhibition of maximum germination were -0.5 MPa and 307 mM, respectively. A high percentage of seed germination was observed at pH=5 and decreased to 61.5% at acidic medium (pH 4) and to 11% at alkaline medium (pH 9). Maximum seedling emergence of Velvetleaf and Barnyardgrass occurred when the seeds were placed on the surface of the soil or at a depth of 1 cm.

The negative effects of competition from barnyardgrass are generally accepted as an important cause of decreased rice growth and grain yield. However, little is known about the impact of barnyardgrass infestation on rice growth in paddy fields in relationship to contrasts in allelopathic traits and soil microbial community composition. We studied the response of rice growth and microbial feedback to barnyardgrass infestation using the allelopathic rice line PI312777 and the nonallelopathic cultivar Liaojing-9 grown with barnyardgrass and in barnyardgrass-infested soil in the field. Barnyardgrass infestation positively affected rice growth and reproduction in PI312777, but it did not do so in Liaojing-9. The chemical and biogeochemical characteristics of the soil did not differ significantly between the treatments and the controls. However, barnyardgrass infestation and mixed culture altered the microbiological properties of the soil, especially microbial biomass and community structure. The total PLFA concentration in Liaojing-9 and PI312777 in the barnyardgrass-infested soil and in mixed culture was higher than that of the control. The same trend occurred in the values of the bacteria: fungi ratio, Gram−:Gram+ ratio, stress level, and Shannon–Wiener index. A principal component analysis of the PLFA clearly separated the treatments. Our findings indicate that shifts in microbial community composition induced by barnyardgrass infestation may generate positive feedback on rice growth and reproduction in a given paddy system. From the perspective of plant–microbe–soil interactions, we should further evaluate the overall effect of barnyardgrass infestation on productivity and diversity in the paddy ecosystem.

Weed-suppressive rice cultivars hold promise for improved and more economical weed management in rice. Interactions between roots of rice and weeds are thought to be modulated by the weed-suppressive activity of some rice cultivars, but these phenomena are difficult to measure and not well understood. Thus, above-ground productivity, weed suppression, and root distribution of 11 rice cultivars and two weed species were evaluated in a drill-seeded, flood-irrigated system at Stuttgart, Arkansas, USA in a two-year study. The allelopathic cultivars, PI 312777 and Taichung Native 1 (TN-1), three other weed-suppressive cultivars, three indica-derived breeding selections, and three non-suppressive commercial cultivars were evaluated in field plots infested with barnyardgrass (Echinochloa crus-galli (L.) Beauv.) or bearded sprangletop (sprangletop, Leptochloa fusca (L.) Kunth var. fascicularis (Lam.) N. Snow). The allelopathic cultivars produced more tillers and suppressed both weed species to a greater extent than did the breeding selections or the non-suppressive cultivars. 13C isotope discrimination analysis of mixed root samples to a depth of 15 cm revealed that the allelopathic cultivars typically produced a greater fraction of their total root mass in the surface 0–5 cm of soil depth compared to the breeding selections or the non-suppressive cultivars, which tended to distribute their roots more evenly throughout the soil profile. These trends in root mass distribution were apparent at both early (pre-flood) and late-season stages in weed-free and weed-infested plots. Cultivar productivity and root distribution generally responded similarly to competition with the two weed species, but barnyardgrass reduced rice yield and root mass more than did sprangletop. These findings demonstrate for the first time that roots of the allelopathic cultivars PI 312777 and TN-1 explore the upper soil profile more thoroughly than do non-suppressive cultivars under weed-infested and weed-free conditions in flood-irrigated U.S. rice production systems. They raise the interesting prospect that root proliferation near the soil surface might enhance the weed-suppressive activity of allelochemical exudates released from roots. Plant architectural design for weed suppressive activity should take these traits into consideration along with other proven agronomic traits such as high tillering and yield.

Echinochloa species are problematic weed species in direct-seeded rice systems in Asia. Because of concern about the continuous use of single herbicides, cultural weed management strategies need to be developed to maintain the sustainability of direct-seeded rice systems. However, the design of such strategies requires an understanding of the differential responses of weeds to shade caused by crop interference. The effects of shade on growth and seed production of Echinochloa colona, Echinochloa crus-galli, and Echinochloa glabrescens were determined. Weeds of three Echinochloa species were grown continuously in full sunlight or in 50% or 25% of full sunlight, or started in full sunlight and transferred to 50% or 25% of full sunlight at 21 days after sowing. The results suggested that changes in shade regime did not affect the plant height of E. colona and E. glabrescens; however, shade reduced the height of E. crus-galli. Compared with the plants grown in full sunlight, 75% of continuous shade reduced E. crus-galli height by 22%. Shade reduced leaf, total shoot, and root biomass and seed production in all the weed species, if occurred during the early growth of the weeds. The weeds responded with increased leaf biomass ratio when grown in shade. Compared with full sunlight, continuous shade of 75% increased leaf biomass ratio by 90% in E. colona and this value was 25% in the other two species. The results of this study show that shade can reduce weed growth and seed production of Echinochloa species but it should not be considered as a stand-alone strategy to manage these weeds in rice. This highlights the need for the integration of other weed management strategies to achieve complete control of these species.