Monocot Crops Research Articles

Novel resources to investigate leaf plasmodesmata formation in C3 and C4 monocots.

Plasmodesmata (PD) are nanochannels that facilitate cell-to-cell transport in plants. More productive and photosynthetically efficient C4 plants form more PD at the mesophyll (M)-bundle sheath (BS) interface in their leaves than their less efficient C3 relatives. In C4 leaves, PD play an essential role in facilitating the rapid metabolite exchange between the M and BS cells to operate a biochemical CO2 concentrating mechanism, which increases the CO2 partial pressure at the site of Rubisco in the BS cells and hence photosynthetic efficiency. The genetic mechanism controlling PD formation in C3 and C4 leaves is largely unknown, especially in monocot crops, due to the technical challenge of quantifying these nanostructures with electron microscopy. To address this issue, we have generated stably transformed lines of Oryza sativa (rice, C3) and Setaria viridis (setaria, C4) with fluorescent protein-tagged PD to build the first spatiotemporal atlas of leaf pit field (cluster of PD) density in monocots without the need for electron microscopy. Across leaf development, setaria had consistently more PD connections at the M-BS wall interface than rice while the difference in M-M pit field density varied. While light was a critical trigger of PD formation, cell type and function determined leaf pit field density. Complementary temporal mRNA sequencing and gene co-expression network analysis revealed that the pattern of pit field density correlated with differentially expressed PD-associated genes and photosynthesis-related genes. PD-associated genes identified from our co-expression network analysis are related to cell wall expansion, translation and chloroplast signalling.

TFIIS is required for reproductive development and thermal adaptation in barley

Key messageBarley reproductive fitness and efficient heat stress adaptation requires the activity of TFIIS, the elongation cofactor of RNAPII.Regulation of transcriptional machinery and its adaptive role under different stress conditions are studied extensively in the dicot model plant Arabidopsis, but our knowledge on monocot species remains elusive. TFIIS is an RNA polymerase II-associated transcription elongation cofactor. Previously, it was shown that TFIIS ensures efficient transcription elongation that is necessary for heat stress survival in A. thaliana. However, the function of TFIIS has not been analysed in monocots. In the present work, we have generated and studied independent tfIIs-crispr-mutant barley lines. We show that TFIIS is needed for reproductive development and heat stress survival in barley. The molecular basis of HS-sensitivity of tfIIs mutants is the retarded expression of heat stress protein transcripts, which leads to late accumulation of HSP chaperones, enhanced proteotoxicity and ultimately to lethality. We also show that TFIIS is transcriptionally regulated in response to heat, supporting a conserved adaptive function of these control elements for plant thermal adaptation. In sum, our results are a step forward for the better understanding of transcriptional machinery regulation in monocot crops.

Overexpression of plant chitin receptors in wheat confers broad-spectrum resistance to fungal diseases.

Wheat (Triticum aestivum L.) is a globally staple crop vulnerable to various fungal diseases, significantly impacting its yield. Plant cell surface receptors play a crucial role in recognizing pathogen-associated molecular patterns (PAMPs) and activating PAMP-triggered immunity, boosting resistance against a wide range of plant diseases. Although the role of plant chitin receptor CERK1 in immune recognition and defense has been established in Arabidopsis and rice, its function and potential agricultural applications in enhancing resistance to crop diseases remain largely unexplored. Here, we identify and characterize TaCERK1 in Triticeae crop wheat, uncovering its involvement in chitin recognition, immune regulation, and resistance to fungal diseases. By a comparative analysis of CERK1 homologs in Arabidopsis and monocot crops, we demonstrate that AtCERK1 in Arabidopsis elicits the most robust immune response. Moreover, we show that overexpressing TaCERK1 and AtCERK1 in wheat confers resistance to multiple fungal diseases, including Fusarium head blight, stripe rust, and powdery mildew. Notably, transgenic wheat lines with moderately expressed AtCERK1 display superior disease resistance and heightened immune responses without adversely affecting growth and yield, compared to TaCERK1 overexpression transgenics. Our findings highlight the significance of plant chitin receptors across diverse plant species and suggest potential strategies for bolstering crop resistance against broad-spectrum diseases in agricultural production through the utilization of plant immune receptors.

Characterization of switchgrass (Panicum virgatum L.) PvKSL1 as a levopimaradiene/abietadiene-type diterpene synthase.

The diverse class of plant diterpenoid metabolites serves important functions in mediating growth, chemical defence, and ecological adaptation. In major monocot crops, such as maize (Zea mays), rice (Oryza sativa), and barley (Hordeum vulgare), diterpenoids function as core components of biotic and abiotic stress resilience. Switchgrass (Panicum virgatum) is a perennial grass valued as a stress-resilient biofuel model crop. Previously we identified an unusually large diterpene synthase family that produces both common and species-specific diterpenoids, several of which accumulate in response to abiotic stress. Here, we report discovery and functional characterization of a previously unrecognized monofunctional class I diterpene synthase (PvKSL1) via in vivo co-expression assays with different copalyl pyrophosphate (CPP) isomers, structural and mutagenesis studies, as well as genomic and transcriptomic analyses. In particular, PvKSL1 converts ent-CPP into ent-abietadiene, ent-palustradiene, ent-levopimaradiene, and ent-neoabietadiene via a 13-hydroxy-8(14)-ent-abietene intermediate. Notably, although featuring a distinct ent-stereochemistry, this product profile is near-identical to bifunctional (+)-levopimaradiene/abietadiene synthases occurring in conifer trees. PvKSL1 has three of four active site residues previously shown to control (+)-levopimaradiene/abietadiene synthase catalytic specificity. However, mutagenesis studies suggest a distinct catalytic mechanism in PvKSL1. Genome localization of PvKSL1 distant from other diterpene synthases, and its phylogenetic distinctiveness from known abietane-forming diterpene synthases, support an independent evolution of PvKSL1 activity. Albeit at low levels, PvKSL1 gene expression predominantly in roots suggests a role of diterpenoid formation in belowground tissue. Together, these findings expand the known chemical and functional space of diterpenoid metabolism in monocot crops.

Bridging photosynthetic worlds: Creating C4-CAM chimeras through embryo grafting in maize and orchids

Traditional grafting practices exclude monocots due to their physical incompatibilities. Their distinct anatomical features, such as scattered vascular bundles and parallel venation and lack of vascular cambium, don't allow for graft healing. The recent development of embryonic grafting has disapproved the requirement of vascular cambium for grafting, instead relying on undifferentiated tissue. We grafted the embryos of two photosynthetically different plants- Zea mays (C4) and Dendrobium ovatum (CAM). We successfully generated grafts through a ‘whole embryo-protocorm’ method. The grafts showed multiple morphological characteristics, which included curling of leaves, stunted growth, and callus-like structure. We did an anatomical analysis to confirm graft union and vascular connectivity. The grafts showed over an 80 % survival rate across all morphology 30 days after grafting. The embryonic meristematic cells proliferated and healed the graft junction, thus allowing the grafted embryo to grow as an individual plant. This technique opens avenues for trait transfer between monocot crops.

Plant regeneration in the new era: from molecular mechanisms to biotechnology applications.

Plants or tissues can be regenerated through various pathways. Like animal regeneration, cell totipotency and pluripotency are the molecular basis of plant regeneration. Detailed systematic studies on Arabidopsis thaliana gradually unravel the fundamental mechanisms and principles underlying plant regeneration. Specifically, plant hormones, cell division, epigenetic remodeling, and transcription factors play crucial roles in reprogramming somatic cells and reestablishing meristematic cells. Recent research on basal non-vascular plants and monocot crops has revealed that plant regeneration differs among species, with various plant species using distinct mechanisms and displaying significant differences in regenerative capacity. Conducting multi-omics studies at the single-cell level, tracking plant regeneration processes in real-time, and deciphering the natural variation in regenerative capacity will ultimately help understand the essence of plant regeneration, improve crop regeneration efficiency, and contribute to future crop design.

A method for separating tonoplast from wheat

Vacuoles account for 90% of plant cell volume and play important roles in maintaining osmotic pressure, storing metabolites and lysosomes, compartmentalizing harmful ions, and storing and reusing minerals. These functions closely relay on the ion channels and transporters located on the tonoplast. The separation of intact vacuoles from plant cells is the key technology utilized in the study of tonoplast-located ion channels and transporters. However, the current vacuole separation methods are available for Arabidopsis and some other dicotyledons but are lacking for monocot crops. In this study, we established a new method for the vacuole separation from wheat mesophyll cells and investigated the transmembrane proton flux of tonoplasts with non-invasive micro-test technology (NMT). Moreover, our study provides a technology for the study of vacuole functions in monocot crops.

Drought stress-inducible synthetic promoters designed for poplar are functional in rice.

Water deficit-inducible synthetic promoters, SD9-2 and SD18-1, designed for use in the dicot poplar, are functional in the monocot crop, rice.

Selective herbicide safening in dicot plants: a case study in Arabidopsis.

Safeners are agrochemicals co-applied with herbicides that facilitate selective control of weeds by protecting monocot crops from chemical injury through enhancing the expression of detoxifying enzymes such as glutathione transferases (GSTs). Even though the application of safeners causes the induction of genes encoding GSTs in model dicots such as Arabidopsis thaliana, safeners do not protect broadleaf crops from herbicide injury. In this study, we proposed that the localized induction of Arabidopsis GSTs and the fundamental differences in their detoxifying activity between dicot and monocot species, underpin the failure of safeners to protect Arabidopsis from herbicide toxicity. Using the herbicide safener, isoxadifen-ethyl, we showed that three tau (U) family GSTs namely AtGSTU7, AtGSTU19 and AtGSTU24 were induced with different magnitude by isoxadifen treatment in root and rosette tissues. The higher magnitude of inducibility of these AtGSTUs in the root tissues coincided with the enhanced metabolism of flufenacet, a herbicide that is active in root tissue, protecting Arabidopsis plants from chemical injury. Assay of the recombinant enzyme activities and the significant reduction in flufenacet metabolism determined in the T-DNA insertion mutant of AtGSTU7 (gstu7) in Arabidopsis plants identified an important function for AtGSTU7 protein in flufenacet detoxification. In-silico structural modeling of AtGSTU7, suggested the unique high activity of this enzyme toward flufenacet was due to a less constrained active site compared to AtGSTU19 and AtGSTU24. We demonstrate here that it is possible to induce herbicide detoxification in dicotyledonous plants by safener treatment, albeit with this activity being restricted to very specific combinations of herbicide chemistry, and the localized induction of enzymes with specific detoxifying activities.

Coordinated Transcriptome and Metabolome Analyses of a Barley hvhggt Mutant Reveal a Critical Role of Tocotrienols in Endosperm Starch Accumulation.

Tocotrienols and tocopherols (vitamin E) are potent antioxidants that are synthesized in green plants. Unlike ubiquitous tocopherols, tocotrienols predominantly accumulate in the endosperm of monocot grains, catalyzed by homogentiate geranylgeranyl transferase (HGGT). Previously, we generated a tocotrienol-deficient hvhggt mutant with shrunken barley grains. However, the relationship between tocotrienols and grain development remains unclear. Here, we found that the hvhggt lines displayed hollow endosperms with defective transfer cells and reduced aleurone layers. The carbohydrate and starch contents of the hvhggt endosperm decreased by approximately 20 and 23%, respectively. Weighted gene coexpression network analyses identified a critical gene module containing HvHGGT, which was strongly associated with the hvhggt mutation and enriched with gene functions in starch and sucrose metabolism. Metabolome measurements revealed an elevated soluble sugar content in the hvhggt endosperm, which was significantly associated with the identified gene modules. The hvhggt endosperm had significantly higher NAD(H) and NADP(H) contents and lower levels of ADPGlc (regulated by redox balance) than the wild-type, consistent with the absence of tocotrienols. Interestingly, exogenous α-tocotrienol spraying on developing hvhggt spikes partially rescued starch accumulation and endosperm defects. Our study supports a potential novel function of tocotrienols in grain starch accumulation and endosperm development in monocot crops.

Enhancing wheat regeneration and genetic transformation through overexpression of TaLAX1

In the realm of genetically transformed crops, the process of plant regeneration holds utmost significance. However, the low regeneration efficiency of several wheat varieties currently restricts the use of genetic transformation for gene functional analysis and improved crop production. This research explores overexpression of TaLAX PANICLE1 (TaLAX1), which markedly enhances regeneration efficiency, thereby boosting genetic transformation and genome editing in wheat. Particularly noteworthy is the substantial increase in regeneration efficiency of common wheat varieties previously regarded as recalcitrant to genetic transformation. Our study shows that increased expression of TaGROWTH-REGULATING FACTOR (TaGRF) genes, alongside that of their co-factor, TaGRF-INTERACTING FACTOR 1 (TaGIF1), enhances cytokinin accumulation and auxin response, which may play pivotal roles in the improved regeneration and transformation of TaLAX1-overexpressing wheat plants. Overexpression of TaLAX1 homologs also significantly increases the regeneration efficiency of maize and soybean, suggesting that both monocot and dicot crops can benefit from this enhancement. Our findings shed light on a gene that enhances wheat genetic transformation and elucidate molecular mechanisms that potentially underlie wheat regeneration.

Invasion of fall armyworm, (Spodoptera frugiperda, J E Smith) (Lepidoptera, Noctuidae) on onion in the maize–onion crop sequence from Maharashtra, India

IntroductionClimate change affects geographical distribution of insect pests which poses threats to the environment, as well as agricultural productivity and production worldwide. Spodoptera frugiperda is commonly known as fall armyworm (FAW), a potential insect pest of monocot crops like maize, wheat, rice and sorghum globally. Among these, maize is the most preferred host crop while worldwide there are very few reports on onion being a host of fall armyworm.MethodsThe fall armyworm (FAW) was identified by examining the morphological characteristics of its immature and mature stages, as well as by analyzing the mitochondrial cytochrome oxidase 1 (COX1) gene. Further, the strain identity was confirmed through multiple sequence alignment with previously identified S. frugiperda strains from corn and rice. Also studied the biology and damage symptoms caused by FAW in onion crops.ResultsDuring our experiments, the incidence of FAW ranged from 5 to 20 percent in different plots. The highest incidence was observed in young crops (30–45 days after transplanting) that were sown in November 2020. The FAW larvae exhibited six instars, with a total larval duration of 22.2 ± 0.37 days. The pest had multiple generations per year. The fully developed larvae formed earthen cocoons in the soil for pupation, with a pupal duration of 8.0 ± 0.45 days. The male adults had a recorded longevity of 6.4± 0.40days, while the female adults lived for approximately 9.2 ± 0.37 days. The COX1 gene sequencing revealed its 100% similarity with Spodoptera frugiperda and the comparison of sequences among FAW infecting rice and maize by using multiple sequence alignment showed differences at 11 positions.DiscussionThe present study is the first report of FAW invasion in onion in India and provides basic ideas about FAW characteristics which will help to control this new invasive pest in onion. In tropical regions with multiple cropping system and seasons, it becomes very important to investigate invasive pests as well as its host range in order to forecast its potential damage and devise suitable control measures.

Differential biochemical and metabolic responses of contrast rice cultivars (<i>Oryza sativa</i> L.) under salt stress

More than half of the global population uses rice as the fundamental staple food; therefore, it is one of the most popular crops in the world. However, it is susceptible to salt stress, particularly among monocot crops, which reduces rice cultivation yield and threatens global food security. This research investigates the role of some factors, including amino acids, antioxidant enzymes, and sugars, in the response to the salinity stress of three contrasting rice cultivars, Dai Thom 8 (salt-sensitive), OC 10 (moderately salt-tolerant), and OM 9577 (salt-tolerant) in the seedling stage. The salt-tolerant varieties exhibited remarkable differences in physiological and biochemical traits, including enhancement of growth capacity, reduction of cell membrane damage via lowering lipid peroxidation, minimization of ROS generation, enhancement of free radical scavenging activity, and SOD, POD, and CAT enzyme activities. Additionally, the study analyzed the presence of 13 sugars using GC-MS and found that all three rice cultivars shared seven common sugars in similar quantities. However, OM 9577 had a higher content of the other six sugars compared to OC 10 and Dai Thom 8. It is one of the important biochemical factors responsible for the difference in the response mechanism to NaCl stress among rice varieties, specifically lyxofuranose (3.268%), a-D-xylopyranose (5.727%), mannopyranose (12.86%), α-D-glucopyranose (6.399%), ß-D-glucopyranose (5.509%), and D-arabinose (1.512%). Furthermore, the quantification of 20 amino acids through HPLC-DAD revealed that the salt-tolerant rice cultivars had higher concentrations of 11 amino acids than the salt-sensitive ones, including proline, isoleucine, serine, ornithine, histidine, glutamic acid, asparagine, alpha-alanine, aspartic acid, glutamine, and valine. These findings provide promising biochemical indicators for selecting salt-tolerant rice cultivars or improving existing varieties through traditional hybridization or gene transfer methods. Understanding these responses can significantly contribute to enhancing rice cultivation and ensuring food security in regions facing salinity challenges.

Three R2R3-MYB transcription factors from banana (Musa acuminata) activate structural anthocyanin biosynthesis genes as part of an MBW complex

ObjectiveBananas are one of the most popular fruits in the world, providing food security and employment opportunities in several developing countries. Increasing the anthocyanin content of banana fruit could improve the health-promoting properties. Anthocyanin biosynthesis is largely regulated at the transcriptional level. However, relatively little is known about the transcriptional activation of anthocyanin biosynthesis in banana.ResultsWe analysed the regulatory activity of three Musa acuminata MYBs that were predicted by bioinformatic analysis to transcriptionally regulate anthocyanin biosynthesis in banana. MaMYBA1, MaMYBA2 and MaMYBPA2 did not complement the anthocyanin-deficient phenotype of the Arabidopsis thaliana pap1/pap2 mutant. However, co-transfection experiments in A. thaliana protoplasts showed that MaMYBA1, MaMYBA2 and MaMYBPA2 function as components of a transcription factor complex with a bHLH and WD40 protein, the so called MBW complex, resulting in the activation of the A. thaliana ANTHOCYANIDIN SYNTHASE and DIHYDROFLAVONOL 4-REDUCTASE promoters. The activation potential of MaMYBA1, MaMYBA2 and MaMYBPA2 was increased when combined with the monocot Zea mays bHLH ZmR instead of the dicot AtEGL3. This work paves the path towards decoding the MBW complex-mediated transcriptional activation of anthocyanin biosynthesis in banana. It will also facilitate research towards increased anthocyanin content in banana and other monocot crops.

Monocot crop-aphid interactions: Plant resilience and aphid adaptation.

Globally, aphids cause immense economic damage to several crop plants. In addition, aphids vector several plant viral diseases that accelerate crop yield losses. While feeding, aphids release saliva that contains effectors, which modulate plant defense responses. Although there are many studies that describe the mechanisms that contribute to dicot plant-aphid interactions, our understanding of monocot crop defense mechanisms against aphids is limited. In this review, we focus on the interactions between monocot crops and aphids and report the recently characterized aphid effectors and their functions in aphid adaptation to plant immunity. Recent studies on plant defense against aphids in monocot-resistant and tolerant crop lines have exploited various "omic'' approaches to understand the roles of early signaling molecules, phytohormones, and secondary metabolites in plant response to aphid herbivory. Unraveling key regulatory mechanisms underlying monocot crop resistance to aphids will lead to deeper understanding of sap-feeding insect management strategies for increased food security and sustainable agriculture.

Current advances in the molecular regulation of abiotic stress tolerance in sorghum via transcriptomic, proteomic, and metabolomic approaches.

Sorghum (Sorghum bicolor L. Moench), a monocot C4 crop, is an important staple crop for many countries in arid and semi-arid regions worldwide. Because sorghum has outstanding tolerance and adaptability to a variety of abiotic stresses, including drought, salt, and alkaline, and heavy metal stressors, it is valuable research material for better understanding the molecular mechanisms of stress tolerance in crops and for mining new genes for their genetic improvement of abiotic stress tolerance. Here, we compile recent progress achieved using physiological, transcriptome, proteome, and metabolome approaches; discuss the similarities and differences in how sorghum responds to differing stresses; and summarize the candidate genes involved in the process of responding to and regulating abiotic stresses. More importantly, we exemplify the differences between combined stresses and a single stress, emphasizing the necessity to strengthen future studies regarding the molecular responses and mechanisms of combined abiotic stresses, which has greater practical significance for food security. Our review lays a foundation for future functional studies of stress-tolerance-related genes and provides new insights into the molecular breeding of stress-tolerant sorghum genotypes, as well as listing a catalog of candidate genes for improving the stress tolerance for other key monocot crops, such as maize, rice, and sugarcane.

Foxtail mosaic virus: A tool for gene function analysis in maize and other monocots.

Many plant viruses have been engineered into vectors for use in functional genomics studies, expression of heterologous proteins, and, most recently, gene editing applications. The use of viral vectors overcomes bottlenecks associated with mutagenesis and transgenesis approaches often implemented for analysis of gene function. There are several engineered viruses that are demonstrated or suggested to be useful in maize through proof-of-concept studies. However, foxtail mosaic virus (FoMV), which has a relatively broad host range, is emerging as a particularly useful virus for gene function studies in maize and other monocot crop or weed species. A few clones of FoMV have been independently engineered, and they have different features and capabilities for virus-induced gene silencing (VIGS) and virus-mediated overexpression (VOX) of proteins. In addition, FoMV can be used to deliver functional guide RNAs in maize and other plants expressing the Cas9 protein, demonstrating its potential utility in virus-induced gene editing applications. There is a growing number of studies in which FoMV vectors are being applied for VIGS or VOX in maize and the vast majority of these are related to maize-microbe interactions. In this review, we highlight the biology and engineering of FoMV as well as its applications in maize-microbe interactions and more broadly in the context of the monocot functional genomics toolbox.

Functional dissection of rice jasmonate receptors involved in development and defense.

The phytohormones, jasmonates (JAs), mediate many plant developmental processes and their responses to important environmental stresses, such as herbivore attack. Bioactive JAs are perceived by CORONATINE INSENSITIVE (COI)-receptors, and associated JAZ proteins, to activate downstream responses. To date, the JA receptors of the important monocot crop plant, rice, remain to be explored. Here, we studied all three rice COI proteins, OsCOI1a, OsCOI1b, and OsCOI2, by ligand binding, genome editing, and phenotyping and examining some of the responsible mechanisms for the different responses. OsCOI2 binds to most individual OsJAZs in the presence of endogenous JA ligands, as OsCOI1a /1b do, albeit with greater partner selectivity. Single mutants of each OsCOI and OsCOI1a/1b double mutants were constructed by CRIPSR-Cas9-based genome editing and used to phenotype developmental and defense responses. OsCOI1b is involved in root growth and grain-size control and plays overlapping roles with OsCOI1a in spikelet development, while OsCOI2 regulates leaf senescence, male sterility, root growth, and grain size. All OsCOIs mediated resistance to the devastating rice pest, the brown planthopper. However, the defense sectors regulated by OsCOI1a/1b and OsCOI2 clearly differed. Our results revealed that all three OsCOIs are functional JA receptors that play diverse roles in regulating downstream JA responses.

Estimation of Off-Target Dicamba Damage on Soybean Using UAV Imagery and Deep Learning.

Weeds can cause significant yield losses and will continue to be a problem for agricultural production due to climate change. Dicamba is widely used to control weeds in monocot crops, especially genetically engineered dicamba-tolerant (DT) dicot crops, such as soybean and cotton, which has resulted in severe off-target dicamba exposure and substantial yield losses to non-tolerant crops. There is a strong demand for non-genetically engineered DT soybeans through conventional breeding selection. Public breeding programs have identified genetic resources that confer greater tolerance to off-target dicamba damage in soybeans. Efficient and high throughput phenotyping tools can facilitate the collection of a large number of accurate crop traits to improve the breeding efficiency. This study aimed to evaluate unmanned aerial vehicle (UAV) imagery and deep-learning-based data analytic methods to quantify off-target dicamba damage in genetically diverse soybean genotypes. In this research, a total of 463 soybean genotypes were planted in five different fields (different soil types) with prolonged exposure to off-target dicamba in 2020 and 2021. Crop damage due to off-target dicamba was assessed by breeders using a 1-5 scale with a 0.5 increment, which was further classified into three classes, i.e., susceptible (≥3.5), moderate (2.0 to 3.0), and tolerant (≤1.5). A UAV platform equipped with a red-green-blue (RGB) camera was used to collect images on the same days. Collected images were stitched to generate orthomosaic images for each field, and soybean plots were manually segmented from the orthomosaic images. Deep learning models, including dense convolutional neural network-121 (DenseNet121), residual neural network-50 (ResNet50), visual geometry group-16 (VGG16), and Depthwise Separable Convolutions (Xception), were developed to quantify crop damage levels. Results show that the DenseNet121 had the best performance in classifying damage with an accuracy of 82%. The 95% binomial proportion confidence interval showed a range of accuracy from 79% to 84% (p-value ≤ 0.01). In addition, no extreme misclassifications (i.e., misclassification between tolerant and susceptible soybeans) were observed. The results are promising since soybean breeding programs typically aim to identify those genotypes with 'extreme' phenotypes (e.g., the top 10% of highly tolerant genotypes). This study demonstrates that UAV imagery and deep learning have great potential to high-throughput quantify soybean damage due to off-target dicamba and improve the efficiency of crop breeding programs in selecting soybean genotypes with desired traits.

Pipecolic acid synthesis is required for systemic acquired resistance and plant-to-plant-induced immunity in barley.

Defense responses in plants are based on complex biochemical processes. Systemic acquired resistance (SAR) helps to fight infections by (hemi-)biotrophic pathogens. One important signaling molecule in SAR is pipecolic acid (Pip), accumulation of which is dependent on the aminotransferase ALD1 in Arabidopsis. While exogenous Pip primes defense responses in the monocotyledonous cereal crop barley (Hordeum vulgare), it is currently unclear if endogenous Pip plays a role in disease resistance in monocots. Here, we generated barley ald1 mutants using CRISPR/Cas9, and assessed their capacity to mount SAR. Endogenous Pip levels were reduced after infection of the ald1 mutant, and this altered systemic defense against the fungus Blumeria graminis f. sp. hordei. Furthermore, Hvald1 plants did not emit nonanal, one of the key volatile compounds that are normally emitted by barley plants after the activation of SAR. This resulted in the inability of neighboring plants to perceive and/or respond to airborne cues and prepare for an upcoming infection, although HvALD1 was not required in the receiver plants to mediate the response. Our results highlight the crucial role of endogenous HvALD1 and Pip for SAR, and associate Pip, in particular together with nonanal, with plant-to-plant defense propagation in the monocot crop barley.