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Plant cell surface receptor-like kinases (RLKs) mediate the signals from microbe-associated molecular patterns (MAMPs) that induce immune responses. Lipopolysaccharide (LPS), the major constituent of the outer membrane of gram-negative bacteria, is a common MAMP perceived by animals and plants; however, the plant receptors/co-receptors are unknown except for LORE, a bulb-type lectin S-domain RLK (B-lectin SD1-RLK) in Arabidopsis. OsCERK1 is a multifunctional RLK in rice that contains lysin motifs (LysMs) and is essential for the perception of chitin, a fungal MAMP, and peptidoglycan, a bacterial MAMP. Here, we analyzed the relevance of OsCERK1 to LPS perception in rice. Using OsCERK1-knockout mutants (oscerk1), we evaluated hydrogen peroxide (H2O2) production and gene expression after LPS treatment. We also examined the LPS response in knockout mutants for the B-lectin SD1-RLK genes in rice and for all LysM-protein genes in Arabidopsis. Compared with wild-type rice cells, LPS responses in oscerk1 cells were mostly diminished. By contrast, rice lines mutated in either of three B-lectin SD1-RLK genes and Arabidopsis lines mutated in the LysM-protein genes responded normally to LPS. From these results, we conclude that OsCERK1 is an LPS receptor/co-receptor and that the LPS perception systems of rice and Arabidopsis are significantly different.

Global warming may reduce rice yield through poor pollination caused by high temperatures at flowering. The dominant parameter controlling the pollination stability in rice cultivars at high temperatures was studied. We examined the effects of a high daytime temperature (35.0ºC, 37.5ºC, 40.0ºC) and its duration (1, 3, 5 days) on the percentage of dehisced thecae, the length of dehiscence in the basal part of the theca for pollen dispersal, and pollination stability. The percentage of sufficiently pollinated florets (%SPF) decreased with the increase in daytime temperature and the duration of treatment. At a daytime temperature of 37.5ºC, %SPF varied widely among the cultivars and was highly correlated with the length of dehiscence formed at the basal part of the theca (r=0.930, P<0.01, n=6) and the percentage of dehisced thecae (r=0.868, P<0.05, n=6). The factor that better explained the variation in %SPF shifted from the length of the basal dehiscence to the percentage of dehisced thecae with increasing duration of high-temperature treatment. Thus, the process preventing pollination shifted from pollen release to anther dehiscence with the increase of exposure to a high temperature.

Herbicide-resistant barnyardgrass and weedy rice control, without crop injury, is a challenge for rice producers in the United States. Herbicides not initially labeled for rice, such as oxyfluorfen, are now being evaluated as new tools for weed control. The ROXY® trait allows for the use of oxyfluorfen in rice for weed control preemergence and postemergence. Experiments were initiated in 2021 and 2022 to evaluate (1) the effectiveness of preemergence- and postemergence-applied oxyfluorfen on barnyardgrass and weedy rice, (2) the sensitivity of oxyfluorfen-resistant rice to oxyfluorfen as a function of application timing, and (3) the influence of soil moisture on oxyfluorfen-resistant rice sensitivity to oxyfluorfen. In the field, a rate response was observed for oxyfluorfen applied to weedy rice when averaged over application timings of 1-leaf, 2-leaf, 3-leaf, and tillering, with oxyfluorfen at 1,680 g ai ha–1 resulting in 81% and 72% control 7 d after application (DAA) in 2021 and 2022, respectively. Under greenhouse conditions, barnyardgrass and weedy rice control averaged by the rate of oxyfluorfen was ≥85 and ≥70%, respectfully, 7 DAA for the 1-, 2-, and 3-leaf rice growth stage timings. Preemergence applications of oxyfluorfen under 100% soil saturation resulted in 75% injury to oxyfluorfen-resistant rice, greater than all other soil moisture at 7 DAA. All postemergence applications of oxyfluorfen resulted in 63% to 70% injury to oxyfluorfen-resistant rice at 7 DAA, regardless of soil moisture. Barnyardgrass and weedy rice control with oxyfluorfen is achieved with timely applications; however, injury to oxyfluorfen-resistant rice is likely. Nomenclature: Oxyfluorfen; barnyardgrass, Echinochloa crus-galli (L.) P. Beauv.; weedy rice, Oryza sativa L.; rice, Oryza sativa L.

Many problematic weeds have evolved resistance to herbicides in mid-southern U.S. rice fields. With the lack of new effective herbicides, rice producers seek alternatives that are currently not labeled for rice production. Inhibitors of very-long chain fatty acid elongase (VLCFA) are currently not labeled for use with U.S. rice crops but are labeled for use in other U.S. row cropping systems and rice production in Asia. Previous research has demonstrated the utility of VLCFA inhibitors for weed control in rice; however, these herbicides induce variable amounts of injury to the crop when applied early in the growing season. Experiments were initiated in 2020 and 2021 at the Rice Research and Extension Center near Stuttgart, AR, to evaluate rice tolerance and weed control with acetochlor and seed treatment with a herbicide safener, fenclorim. Three rates of a microencapsulated formulation of acetochlor (630, 1,260, and 1,890 g ai ha-1), four application timings (preemergence, PRE; delayed-preemergence, DPRE; spiking; and 1-leaf), and without or with the fenclorim seed treatment (2.5 g kg–1 of seed) were used to evaluate rice tolerance, weedy rice control, and barnyardgrass control. Acetochlor applied DPRE at 1,260 g ai ha-1 provided better weedy rice and barnyardgrass control than applications at the 1-leaf stage at the same rate. Acetochlor rates of 1,260 and 1,890 g ai ha-1 reduced barnyardgrass and weedy rice densities by more greater than the 630 g ai ha-1 rate. The fenclorim seed treatment did not influence weedy rice or barnyardgrass control but did reduce injury for DPRE acetochlor applications. Based on these results, acetochlor can be safely applied to rice DPRE (≤19% injury) at 1,260 g ai ha-1 when the seed is treated with fenclorim, leading to ≥88% barnyardgrass and ≥45% weedy rice control 28 d after treatment. Nomenclature: Acetochlor; fenclorim; barnyardgrass, Echinochloa crus-galli (L.) P. Beauv; weedy rice, Oryza sativa L.; rice, Oryza sativa L.

Information on performance of sequential treatments of quizalofop-P-ethyl with florpyrauxifen-benzyl on rice is lacking. Field studies were conducted in 2017 and 2018 in Stoneville, MS, to evaluate sequential timings of quizalofop-P-ethyl with florpyrauxifen-benzyl included in preflood treatments of rice. Quizalofop-P-ethyl treatments were no quizalofop-P-ethyl; sequential applications of quizalofop-P-ethyl at 120 g ha–1 followed by (fb) 120 g ai ha–1 applied to rice in the 2- to 3-leaf (EPOST) fb the 4-leaf to 1-tiller (LPOST) growth stages or LPOST fb 10 d after flooding (PTFLD); quizalofop-P-ethyl at 100 g ha–1 fb 139 g ha–1 EPOST fb LPOST or LPOST fb PTFLD; quizalofop-P-ethyl at 139 g ha–1 fb 100 g ha–1 EPOST fb LPOST and LPOST fb PTFLD; and quizalofop-P-ethyl at 85 g ha–1 fb 77 g ha–1 fb 77 g ha–1 EPOST fb LPOST fb PTFLD. Quizalofop-P-ethyl was applied alone and in mixture with florpyrauxifen-benzyl at 29 g ai ha–1 LPOST. Visible rice injury 14 d after PTFLD (DA-PTFLD) was no more than 3%. Visible control of volunteer rice (‘CL151' and ‘Rex') 7 DA-PTFLD was similar and at least 95% for each quizalofop-P-ethyl treatment. Barnyardgrass control with quizalofop-P-ethyl at 120 fb 120 g ha–1 LPOST fb PTFLD was greater (88%) in mixture with florpyrauxifen-benzyl. The addition of florpyrauxifen-benzyl to quizalofop-P-ethyl increased rough rice yield when quizalofop-P-ethyl was applied at 100 g ha–1 fb 139 g ha–1 EPOST fb LPOST. Sequential applications of quizalofop-P-ethyl at 120 g ha–1 fb 120 g ha–1 EPOST fb LPOST, 100 g ha–1 fb 139 g ha–1 EPOST fb LPOST, or 139 g ha–1 fb 100 g ha–1 EPOST fb LPOST controlled grass weed species. The addition of florpyrauxifen-benzyl was not beneficial for grass weed control. However, because quizalofop-P-ethyl does not control broadleaf weeds, florpyrauxifen-benzyl could provide broadspectrum weed control in acetyl coenzyme A carboxylase–resistant rice. Nomenclature: Florpyrauxifen-benzyl, quizalofop-P-ethyl; barnyardgrass, Echinochloa crus-galli L. Beauv. ECHCG; volunteer rice, Oryza sativa L. ORYSA; rice, Oryza sativa L. ‘PVL01'

*Ÿ Rice microbiota responded to lindane pollutant was studied spatiotemporally. *ŸŸ Growth time, soil types and rhizo-compartments had significant influence. Ÿ Lindane stimulated the endosphere microbiota of rice which was highly dynamic. *ŸŸ Root-soil-microbe interactions induced an inhibited redox-coupled lindane removal. *ŸŸ This work was beneficial to better regulation of plant growth against adversity. Soil-derived microbiota associated with plant roots are conducive to plant growth and stress resistance. However, the spatio-temporal dynamics of microbiota in response to organochlorine pollution during the unstable vegetative growth phase of rice is not well understood. In this study, we focused on the rice ( Oryza sativa L.) microbiota across the bulk soil, rhizosphere and endosphere compartments during the vegetative growth phase in two different soils with and without lindane pollutant. The results showed that the factors of growth time, soil types and rhizo-compartment had significant influence on the microbial communities of rice, while lindane mostly stimulated the construction of endosphere microbiota at the vegetative phase. Active rice root -soil -microbe interactions induced an inhibition effect on lindane removal at the later vegetative growth phase in rice-growth-dependent anaerobic condition, likely due to the root oxygen loss and microbial mediated co-occurring competitive electron-consuming redox processes in soils. Each rhizo-compartment owned distinct microbial communities, and therefore, presented specific ecologically functional categories, while the moderate functional differences were also affected by plants species and residual pollution stress. This work revealed the underground micro-ecological process of microbiota and especially their potential linkage to the natural attenuation of residual organochlorine such as lindane.

● AOM input elevates water-soluble cysteine and labile DOM fractions in soil. ● AOM input fuels potential Hg methylators and non-Hg methylators in soil. ● Decayed algal aggregate is Hg methylating “hotspot” and MeHg source in soil. ● AOM-driven SDOM variations elevate soil MeHg production and bioaccumulation in rice. Algal-derived organic matter (AOM) regulates methylmercury (MeHg) fate in aquatic ecosystems, whereas its role in MeHg production and bioaccumulation in Hg-contaminated paddies is unclear. Pot and microcosm experiments were thus performed to understand the response characteristics of MeHg concentrations in soil and rice in different rice-growing periods to algal decomposition. Compared to the control, algal decomposition significantly increased soil water-soluble cysteine concentrations during the rice-tillering and grain-filling periods ( P < 0.05). It also significantly lowered the molecular weight of soil-dissolved organic matter (SDOM) during the rice-tillering period ( P < 0.05) and SDOM humification/aromaticity during the grain-filling period. Compared to the control, AOM input increased the abundance of potential Hg and non-Hg methylators in soil. Furthermore, it also greatly increased soil MeHg concentrations by 25.6%–80.2% and 12.6%–66.1% during the rice-tillering and grain-filling periods, with an average of 42.25% and 38.42%, respectively, which were significantly related to the elevated cysteine in soil and the decrease in SDOM molecular weight ( P < 0.01). In the early stage (within 10 days of microcosm experiments), the MeHg concentrations in decayed algal particles showed a great decrease ( P < 0.01), suggesting a potential MeHg source in soil. Ultimately, algal decomposition greatly increased the MeHg concentrations and bioaccumulation factors in rice grains, by 72.30% and 16.77%, respectively. Overall, algal decomposition in Hg-contaminated paddies is a non-negligible factor promoting MeHg accumulation in soil-rice systems.

High-energy ion beams are known to be an effective and unique type of physical mutagen in plants. However, no study on the mutagenic effect of argon (Ar) ion beam radiation on rice has been reported. Genome-wide studies on induced mutations are important to comprehend their characteristics for establishing knowledge-based protocols for mutation induction and breeding, which are still very limited in rice. The present study aimed to investigate the mutagenic effect of three ion beams, i.e., Ar, carbon (C) and neon (Ne) on rice and identify and characterize heritable induced mutations by the whole genome sequencing of six M4 plants. Dose-dependent damage effects were observed on M1 plants, which were developed from ion beam irradiated dry seeds of two indica (LH15, T23) and two japonica (DS551, DS48) rice lines. High frequencies of chlorophyll-deficient seedlings and male-sterile plants were observed in all M2 populations (up to ~30% on M1 plant basis); plants from the seeds of different panicles of a common M1 plant appeared to have different mutations; the whole genome-sequencing demonstrated that there were 236–453 mutations in each of the six M4 plants, including single base substitutions (SBSs) and small insertion/deletions (InDels), with the number of SBSs ~ 4–8 times greater than that of InDels; SBS and InDel mutations were distributed across different genomic regions of all 12 chromosomes, however, only a small number of mutations (0–6) were present in exonic regions that might have an impact on gene function. In summary, the present study demonstrates that Ar, C and Ne ion beam radiation are all effective for mutation induction in rice and has revealed at the genome level the characteristics of the mutations induced by the three ion beams. The findings are of importance to the efficient use of ion beam radiation for the generation and utilization of mutants in rice.

The current study investigated the effects of nano-silicon (Si) and common Si on lead (Pb) toxicity, uptake, translocation, and accumulation in the rice cultivars Yangdao 6 and Yu 44 grown in soil containing two different Pb levels (500 mg∙kg–¹ and 1000 mg∙kg–¹). The results showed that Si application alleviated the toxic effects of Pb on rice growth. Under soil Pb treatments of 500 and 1000 mg∙kg–¹, the biomasses of plants supplied with common Si and nano-Si were 1.8%–5.2% and 3.3%–11.8% higher, respectively, than those of plants with no Si supply (control). Compared to the control, Pb concentrations in rice shoots supplied with common Si and nano-Si were reduced by 14.3%–31.4% and 27.6%–54.0%, respectively. Pb concentrations in rice grains treated with common Si and nano-Si decreased by 21.3%–40.9% and 38.6%–64.8%, respectively. Pb translocation factors (TFs) from roots to shoots decreased by 15.0%–29.3% and 25.6%–50.8%, respectively. The TFs from shoots to grains reduced by 8.3%–13.7% and 15.3%–21.1%, respectively, after Si application. The magnitudes of the effects observed on plants decreased in the following order: nano-Si treatment>common Si treatment and high-grain- Pb-accumulating cultivar (Yangdao 6)>low-grain-Pbaccumulating cultivar (Yu 44) and heavy Pb stress (1000 mg∙kg–¹)>moderate Pb stress (500 mg∙kg–¹)>no Pb treatment. The results of the study indicate that nano-Si is more efficient than common Si in ameliorating the toxic effects of Pb on rice growth, preventing Pb transfer from rice roots to aboveground parts, and blocking Pb accumulation in rice grains, especially in high-Pbaccumulating rice cultivars and in heavily Pb-polluted soils.

Heading date (HD) is one of the agronomic traits that influence maturity, regional adaptability, and grain yield. The present study was a follow-up of a previous quantitative trait loci (QTL) mapping study conducted on three populations, which uncovered a total of 62 QTLs associated with 10 agronomic traits. Two of the QTLs for HD on chromosome 7 (qHD7a and qHD7b) had a common flanking marker (RM3670) that may be due to tight linkage, and/or weakness of the statistical method. The objectives of the present study were to map QTLs associated with HD in a set of 76 chromosome segment substitution lines (CSSLs), fine map and validate one of the QTLs (qHD7b) using 2997 BC5F2:3 plants, and identify candidate genes using sequencing and expression analysis. Using the CSSLs genotyped with 120 markers and evaluated under two short-day and two long-day growing conditions, we uncovered a total of fourteen QTLs (qHD2a, qHD4a, qHD4b, qHD5a, qHD6a, qHD6b, qHD7b, qHD7c, qHD8a, qHD10a, qHD10b, qHD11a, qHD12a, and qHD12b). However, only qHD6a and qHD7b were consistently detected in all four environments. The phenotypic variance explained by qHD6a and qHD7b varied from 10.1% to 36.1% (mean 23.1%) and from 8.1% to 32.8% (mean 20.5%), respectively. One of the CSSL lines (CSSL52), which harbored a segment from the early heading XieqingzaoB (XQZB) parent at the qHD7b locus, was then used to develop a BC5F2:3 population for fine mapping and validation. Using a backcross population evaluated for four seasons under different day lengths and temperatures, the qHD7b interval was delimited to a 912.7-kb region, which is located between RM5436 and RM5499. Sequencing and expression analysis revealed a total of 29 candidate genes, of which Ghd7 (Os07g0261200) is a well-known gene that affects heading date, plant height, and grain yield in rice. The ghd7 mutants generated through CRISPR/Cas9 gene editing exhibited early heading. Taken together, the results from both the previous and present study revealed a consistent QTL for heading date on chromosome 7, which coincided not only with the physical position of a known gene, but also with two major effect QTLs that controlled the stigma exertion rate and the number of spikelets in rice. The results provide contributions to the broader adaptability of marker-assisted breeding to develop high-yield rice varieties.