Rice (Oryza sativa L.) agriculture of the southern United States is plagued by strong biotic competition with several species in the Echinochloa genus. Despite clear genomic differences between barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.] and junglerice (Echinochloa colona (L.) Link], the two major Echinochloa agricultural weeds are nearly indistinguishable phenotypically. This inability to reliably differentiate the species has led farmers to treat the group as a single species, often resulting in ineffective weed control efforts. In this study, we first develop a simple chloroplast-anchored PCR-based restriction enzyme assay to differentiate between E. colona and the other Echinochloa species of agricultural concern. Applying this assay, we identify a strong bias towards E. colona in 2024 rice field collections from eastern Arkansas. Finally, we evaluate anecdotal reports of interspecific hybridization between species and find no evidence. Despite the drawbacks of the maternally inherited nature of the chloroplast, the availability of this species determinant assay will help USDA and academia extension agents and stakeholders to make educated, species-specific decisions about precision chemical weed control and field management.

Species in the genus Echinochloa present a major management challenge in rice production worldwide. Understanding the herbicide resistance status of Echinochloa is crucially necessary for raising awareness and developing effective management programs. This study investigated the status of herbicide resistance by junglerice, the predominant Echinochloa species in Texas rice fields. A total of 58 junglerice populations collected during a field survey (2015–2016) of Texas rice fields were screened with two preemergence herbicides; quinclorac (Group 4) and clomazone (Group 13); and four postemergence herbicides: fenoxaprop (Group 1), imazethapyr (Group 2), quinclorac (Group 4), and propanil (Group 5). At 21 d after application (DAA) of herbicide treatments, percent survival, and percent visible injury data were recorded. Based on the injury levels observed, the populations were categorized into being either putative resistant (≤50% injury), less sensitive (51% to 90% injury), or susceptible (≥91% injury). Results showed that herbicide resistance is widespread among the junglerice populations surveyed in Texas. About 5% of the populations showed multiple resistance to all four postemergence herbicides that were evaluated. Dose-response assays were conducted on the populations with the lowest injury ratings to determine the extent of resistance and revealed a >70-fold resistance to imazethapyr, a >15-fold resistance to propanil, and a 3-fold resistance to fenoxaprop, compared with a susceptible check. The results suggested that integrated management practices are needed to manage junglerice in Texas rice production.

The recommended method of control for glyphosate-resistant (GR) Italian ryegrass in Mississippi is to apply residual herbicides in the fall; however, these treatments may negatively affect rice performance. This study was conducted to evaluate rice performance following fall-applied treatments of residual herbicides + flumioxazin at different rates. Pooled over with and without flumioxazin and herbicide rates, clomazone and dimethenamid-P caused <10% injury 28 d after emergence. Acetochlor delayed rice maturity by 2 d to clomazone, dimethenamid-P, and flumioxazin. Rice density was reduced ≥4 plants m−2 following fall-applied acetochlor and dimethenamid-P compared to nontreated plants. Rough rice yields were reduced by ≥670 kg ha−1 with fall-applied acetochlor alone and dimethenamid-P compared to nontreated plants. Acetochlor should not be used as a fall-applied treatment in areas where rice is scheduled to grow the following season. Given current label restrictions and rice injury caused by acetochlor and dimethenamid-P, clomazone remains the only viable option for controlling GR Italian ryegrass where rice is scheduled to be planted the following spring.

The genus Aphelenchoides Fischer, 1894, encompasses nearly 200 species with significant ecological and economic importance, yet its taxonomy remains complex due to morphological similarities among species and limited molecular data. In this study, we describe a new species, Aphelenchoides vinhphucensis sp. n., collected from the rhizosphere of rice (Oryza sativa L.) in Vinh Phuc Province, Vietnam. The new species is distinguished by its morphological characteristics, including a slender stylet (9.6–12.7 μm), distinct lateral fields with four lines, a conical tail with a pointed mucro, and a well-developed post-uterine sac. Males feature three pairs of caudal papillae and arcuate spicules. Scanning electron microscopy provided detailed insights into surface features, complementing light microscopy observations. Molecular analyses of the D2-D3 regions of 28S rRNA and 18S rRNA supported the distinct phylogenetic placement of Aphelenchoides vinhphucensis sp. n., differentiating it from closely related species. Bayesian phylogenetic analysis confirmed its divergence, contributing to our understanding of biodiversity of the genus Aphelenchoides. This integrative approach highlights the importance of combining classical morphological methods with modern molecular tools for accurate species identification. The discovery of Aphelenchoides vinhphucensis sp. n. underscores the nematode diversity in Vietnam, especially those associated with rice cultivation.

Rice cultivated under furrow irrigation faces weed management challenges due to the aerobic conditions that favor the emergence of terrestrial weeds such as Palmer amaranth. Fluridone was recently registered for use in rice production, offering an alternative site of action for Palmer amaranth control. Four site-years of field experiments were conducted in 2022 and 2023 in furrow-irrigated rice to assess Palmer amaranth control and crop tolerance to fluridone applied preemergence alone or with various postemergence treatments. The experiment was a randomized complete block design with a split-plot arrangement and four replications. The whole-plot factor was the postemergence treatment, while the subplot factor was fluridone applied preemergence at 0, 84, 168 (1× labeled rate), and 336 g ai ha−1. Postemergence treatments included no herbicide, a single florpyrauxifen-benzyl application at 6 wk after rice emergence(WAE), and a weed-free control. The 2× rate of fluridone caused the greatest visual injury compared with the 0.5× rate across site-years at 2 and 5 WAE, ranging from 8% to 34%. The 1× and 2× rates of fluridone provided the greatest reduction in Palmer amaranth density 4 wk after treatment (WAT). However, the effect diminished or became less prominent by 8 WAT. Palmer amaranth density at rice harvest was reduced in most instances after a follow-up application of florpyrauxifen-benzyl, and seed production had diminished by ≥94% compared to its absence. Regardless of the fluoridone rate, rough rice grain yield was not affected under weed-free conditions. These findings suggest that integrating fluridone with a subsequent florpyrauxifen-benzyl application enhances Palmer amaranth management in furrow-irrigated rice compared to using fluridone alone. However, sequential applications are needed for successful Palmer amaranth control.

The genetic basis of rapid and uniform seed germination and its associated traits is crucial for improving seed vigour and seedling establishment for higher productivity in direct-seeded rice (DSR) systems. This study investigates the phenotypic diversity and genetic architecture of germination traits in 163 rice genotypes, using a genome-wide association studies (GWAS). An association panel of 163 diverse rice genotypes, including varieties, germplasm and breeding lines, was evaluated for seed germination traits over 2 years (2022 and 2023). The panel was genotyped using 295 simple sequence repeat (SSR) markers, including 80 random SSRs and 215 candidate gene SSRs linked to seed traits and morphological attributes. The genotyping of 163 lines with 295 markers revealed a range of genetic diversity, with polymorphic information content values between 0.04 and 0.93. Population structure analysis indicated the presence of two groups and four sub-groups. GWAS identified 80 significant marker-trait associations (MTAs) across 12 chromosomes at P ≤ 0.05, which narrow down to 18 MTAs at P ≤ 0.01. Twelve candidate genes are identified which were related with multiple traits, linked to important functions, such as seed-size regulation, nutrient mobilization and plant growth. Candidate gene-based SSR (cgSSR) markers such as M169 (OsMIK), M57 (THIS1), M66 (GW2), and M18 (OsBAK1), displayed pleiotropy including rapid and uniform germination (germination index, germination rate index and mean germination time) traits. The newly identified candidate gene markers associated with seed rapid and uniform germination traits can be leveraged in marker-assisted breeding programs to introduce diverse alleles for enhanced seed vigour and crop establishment. Markers closely linked to multiple traits hold significant potential for the simultaneous improvement of several traits.

The stock-to-use ratio (STU) is a widely utilized indicator to assess market conditions and forecast price movements for agricultural commodities. However, before drawing any conclusions, it is essential to empirically investigate the relationship between STU and commodity prices. Using rice as a case study, this research examines the empirical linkage between rice prices and STU, both collectively and individually across 16 leading rice-producing and consuming countries. To do so, the study first employs the panel vector autoregression approach to capture the dynamic interrelationships in a panel data setting, followed by vector autoregression estimation at the individual country level. The results suggest an inverse relationship between rice prices and STU: higher rice prices are associated with lower STU levels (i.e., higher scarcity), and vice versa. Furthermore, the Toda-Yamamoto Granger causality tests indicate that monitoring the STU levels of a select group of influential countries can yield significant insights into global rice export price dynamics. In addition, the analysis highlights the pivotal role of urea fertilizer in maintaining the stability of global rice prices. These findings are particularly relevant in the context of strong government intervention in managing rice stocks in several key rice markets.

Tetflupyrolimet is a novel herbicide that inhibits dihydroorotate dehydrogenase in susceptible weeds, including those in warm-season turfgrass and rice. Given that warm-season species are managed alongside cool-season species that may be sensitive to tetflupyrolimet, research on its lateral movement within turfgrass is warranted. Field experiments were conducted in spring 2023 and 2024 at North Carolina State University to evaluate the potential downslope movement of tetflupyrolimet (400 g ai ha−1) compared with that of pronamide (1,160 g ai ha−¹), an herbicide that is known to move downslope. The studies took place on a 9.5% sloped plot of hybrid bermudagrass that had been established on Cecil sandy loam soil, under two moisture regimes at application: field capacity (≈34% volumetric water content) and saturation (≈46% volumetric water content). Before experimentation, the aboveground hybrid bermudagrass canopy was mechanically removed, and perennial ryegrass was planted as an indicator species. Herbicides were applied to treated areas (2.2 m2) upslope of data collection areas (8.6 m2), with subsequent irrigation and rainfall (2.5 cm total) 24 h after application. Downslope movement was assessed at 2, 4, 6, and 8 wk after treatment via perennial ryegrass mortality assessments made via grid (15 cm2) count. Downslope distances associated with a 50% probability of perennial ryegrass mortality (mortality50) were 1.2 to 3.6 times greater for pronamide compared to tetflupyrolimet. The maximum distance tetflupyrolimet moved was 1.1 m (regardless of soil moisture condition) each year. Comparatively, maximum downslope movement distances for pronamide were 1.5 to 1.65 m under saturated conditions and 1.5 to 1.8 m at field capacity. Overall, these findings suggest a 1.1-m buffer from sensitive species is likely sufficient to prevent undesirable injury following tetflupyrolimet applications to hybrid bermudagrass under conditions similar to this study.

This study was designed to explore changes in soil bulk density (BD), soil organic carbon (SOC) content, SOC stocks, and soil labile organic carbon (C) fractions after 5 years of soil tillage management under the double-cropping rice system in southern of China. The experiment included four soil tillage treatments: rotary tillage with all crop residues removed as a control (RTO); conventional tillage with crop residues incorporation (CT); rotary tillage with crop residues incorporation (RT); and no-tillage with crop residues retention. Our results revealed that soil tillage combined with crop residue incorporation (CT and RT) significantly decreased BD at 0–20 cm soil layer compared to RTO treatment. SOC content and stocks were increased with the application of crop residues. Compared with RTO treatment, SOC content and stocks were increased by 16.8% and 9.8% in CT treatment, respectively. Soil non-labile C content and proportion of labile C were increased due to crop residue incorporation. Compared with RTO treatment, soil proportion of C mineralisation (Cmin), permanganate oxidisable C (KMnO4), particulate organic C (POC), and microbial biomass C (MBC) was increased by 196.1%, 41.4%, 31.4%, and 17.1% under CT treatment, respectively. These results were confirmed by the carbon management index, which was significantly increased under soil tillage with crop residue incorporation. Here, we demonstrated that soil tillage and crop residue incorporation can increase the pool of stable C at surface soil layer while increasing labile C content and proportion. In conclusion, conventional or rotary tillage combined with crop residue incorporation is a soil management able to improve nutrient cycling and soil quality in paddy fields in southern China.

Introducing new herbicides requires a comprehensive understanding of how crops respond to various herbicide-related factors. Fluridone was registered for use in rice production in 2023, but research on rice tolerance to this herbicide is lacking. Hence, field research aimed to 1) evaluate the effect of fluridone application timing on rice tolerance and 2) assess rice response to fluridone in a mixture with standard rice herbicides applied to 3-leaf rice. Both experiments were conducted in a delay-flooded dry-seeded system using a randomized complete block design, with four replications. Treatments in the first experiment included a nontreated control and 10 application timings, ranging from 20 d preplant to postflood. The second experiment had a two-factor factorial structure, with factor A being the presence/absence of fluridone, and factor B being herbicide partners, including bispyribac-sodium, fenoxaprop, penoxsulam, propanil, quinclorac, quizalofop, and saflufenacil. In the first experiment, the maximum injury in 2022 was 28%, caused by the preemergence treatment. In 2023, fluridone applied preemergence caused the greatest injury (42%) 2 wk after flood establishment, declining to 37% in late season (13 d before rice reached 50% heading). Yield reductions of 21% occurred with the delayed preemergence treatment in 2022 and 42% with the preemergence treatment in 2023. Mixing fluridone with standard herbicides increased rice injury by no more than eight percentage points compared with the herbicides applied alone. Additionally, no adverse effects on rice groundcover or grain yield resulted from fluridone in the mixture. These results indicate a need to avoid fluridone applications near planting because of negative impacts on rice. Furthermore, fluridone can be mixed with commonly used rice herbicides, offering minimal risk to rice.

Purple witchweed is a hemiparasitic plant that significantly affects sorghum yields in semiarid regions. It also affects crops such as corn, millets, and rice. Developing purple witchweed-resistant sorghum varieties is an essential element in integrated purple witchweed management. This study evaluated the response of 48 sorghum genotypes to purple witchweed grown both in pots and in field conditions. Resistant varieties (Berhan and Framida) and susceptible varieties (Assosa-1, Adukara, and ETSL102967) were used as controls. The findings revealed substantial variability among the sorghum landraces in their response to purple witchweed. Purple witchweed density was less when seeds were grown with early maturing sorghum genotypes, while late-maturing genotypes were more susceptible to the weed. Notably, the ETSL102969 landrace showed strong resistance, comparable to that of Berhan. Additionally, the ETSL102970 landrace demonstrated superior resistance to purple witchweed compared to Framida. Based on these results, ETSL102969 and ETSL102970 are recommended as valuable sources of resistance for breeding programs aiming to improve sorghum resistance against purple witchweed in Ethiopia.

Systematically monitoring the baseline sensitivity of troublesome weeds to herbicides is a crucial step in the early detection of their market lifespan. Florpyrauxifen-benzyl is one of the most important herbicides used in rice production throughout the world, and has been used for 5 yr in China. Barnyardgrass is one of the main targeted weed species of florpyrauxifen-benzyl. In total, 114 barnyardgrass populations were collected from rice fields in Jiangsu Province, China, and using whole-plant bioassays they were screened for susceptibility to florpyrauxifen-benzyl. The GR50 values (representing the dose that causes a 50% reduction in fresh weight of aboveground parts) of florpyrauxifen-benzyl for all populations ranged from 1.0 to 34.5 g ai ha−1, with an average of 6.8 g ai ha−1, a baseline sensitivity dose of 3.3 g ai ha−1, and a baseline sensitivity index of 34.5. Twenty-one days after treatment with florpyrauxifen-benzyl at the labeled dose (36 g ai ha−1), 90% of the barnyardgrass populations exhibited >95% reductions in fresh weight of aboveground parts. Compared with the baseline sensitivity dose, 63, 44, and 7 populations had, respectively, no resistance (55%), low resistance (39%), and moderate resistance (6%) to florpyrauxifen-benzyl. Furthermore, the GR50 distribution of barnyardgrass populations did not show a significant correlation with collection location, planting method (direct-seeding or transplanting), or rice species (Oryza sativa L. ssp. indica or ssp. japonica) at any of rice fields where seeds had been collected (P > 0.05). In conclusion, florpyrauxifen-benzyl remains effective for barnyardgrass control in rice fields despite serious resistance challenges.