First report of rice bacterial leaf blight disease caused by Pantoea ananatis in the United States.

In August 2021, bacterial leaf blight-like symptoms were observed on 14 out of 570 rice genotypes (Oryza sativa) in research field plots of global rice germplasm grown in Arkansas (eXtra Figure S1. A & B). The disease was characterized by spreading lesions on leaves, panicle sterility and reduced yield in highly susceptible, mature rice germplasm. No spread of disease to nearby plants was observed. Isolations were performed at Colorado State University, where soakates from symptomatic leaves were spread onto nutrient agar. After 72 h at 28°C, uniform, distinct, yellow-colored bacterial colonies were observed. To screen for the presence of common rice bacterial pathogens, PCR amplification directly from colonies or from DNA isolated from symptomatic field-collected leaves was performed. Primers specific for Xanthomonas oryzae pvs. oryzae and oryzicola (Lang et al., 2010), Burkholderia glumae (Echeverri-Rico et al., 2021), and Pseudomonas fuscovaginae (Ash et al., 2014) did not amplify indicating these organisms were not present. Sequencing of 16S rRNA gene (Weisburg et al., 1991) amplicons suggested the bacteria belonged to the genera Pantoea and Sphingomonas (NCBI accession no. OP683332 and OP683333, respectively). Amplicons resulting from primers specific to the gyrB gene region of P. ananatis (Kini et al., 2021) were sequenced and the fragment was compared to the P. ananatis PA13 reference genome using a BLAST analysis. One candidate (AR358) showed 100% identity with the P. ananatis gyrB region. Primers specific for Sphingomonas sp. (Bangratz et al., 2020) confirmed the second candidate (AR359) as a Sphingomonas sp. The identity of P. ananatis was confirmed by the Plant Pathogen Confirmatory Diagnostics Laboratory (Beltsville, MD, USA). To determine pathogenicity, leaves from 7-day-old seedlings of rice (Oryza sativa) cultivar Kitaake were scissor-clip inoculated (Kauffman et al., 1973) with four different treatments and compared to control leaves inoculated with sterile water. Treatments for the experiment consisted of bacterial suspensions (108 CFU/ml) of the two candidate organisms, P. ananatis (strain AR358) or Sphingomonas sp. (strain AR359), individually or in a 1:1 ratio of P. ananatis:Sphingomonas sp., or soakate from infected field tissue. Lesions similar to those observed in the field were only detected on leaves inoculated with P. ananatis or infected field tissue soakate at 7-days post-inoculation (eXtra Figure S1. C). Bacteria were recovered from the leaves of the artificially inoculated seedlings from three treatments (P. ananatis, P. ananatis:Sphingomonas sp. and soakate from the infected field tissue) and were determined to be P. ananatis based on colony morphology, amplification of 16s rRNA, and gyrB sequence data. Our results confirm the pathogenicity of P. ananatis to rice and fulfill Koch's postulates. P. ananatis was also recovered from several similarly diseased rice breeding lines at the University of Arkansas System Division of Agriculture Rice Research and Extension Center. We conclude that P. ananatis is the causal pathogen for leaf blight-like symptoms observed in the global rice cultivars grown in Arkansas. P. ananatis was previously reported as a pathogen on rice in several rice growing regions, including China (Yu et al., 2021), India (Reshma et al., 2022), and Africa (Kini et al., 2017), however, this is the first report of P. ananatis as a pathogen of rice in the United States.

Complete Genome Sequence of Xanthomonas arboricola pv. pruni Strain Xcp1 Isolated in 1984 from a Bacterial Spot Spring Canker on Prunus persica var. nucipersica cv. "Redgold".

Xanthomonas arboricola pv. pruni is an important plant pathogen and the causal agent of bacterial spot of stone fruits (Prunus spp). Here, we report a complete genome of X. arboricola pv. pruni strain Xcp1 generated from hybrid PacBio Sequel and Illumina NextSeq2000 sequencing.

3'-(Phenyl alkynyl) analogs of abscisic acid: synthesis and biological activity of potent ABA antagonists.

We report here the synthesis and biological testing of 3'-(phenyl alkynyl) abscisic ABA analogs, a new class of potent ABA antagonists. These ABA analogs incorporate a rigid framework of eight carbon atoms attached at the 3'-carbon atom of ABA that prevents folding of the ABA analog-bound receptor required for ABA signalling. The two-step synthesis is based upon the optimized conversion of natural (S)-ABA to 3'-iodo ABA which can be coupled to phenyl acetylenes using Sonogashira conditions, or to styryl compounds through Suzuki chemistry. The parent 3'-(phenyl alkynyl) ABA analog 7 was obtained in 29% yield, 74% yield based on recovered starting material. In a lentil seed germination assay, compound 7 was found to have more potent activity than other known 3'-substituted ABA antagonists to date. In a structure activity study parasubstituted phenyl alkynyl analogs had comparable activity to the analog 7 while the 3'-styryl ABA 18 was only slightly less active. Analog 7 overcame ABA inhibition of germination and seedling growth in a wide range of mono and dicot plant species, including canola, lentil, soybean, rice, wheat, barley, cannabis and canary seed. 3'-(Phenyl alkynyl) ABA analogs have numerous potential practical agricultural applications including promoting ripening of crops, dormancy breaking of seeds and woody perennials, as well as promoting seed germination, and growth under stress conditions as demonstrated in this report.

The Complete Genome Sequence of Xanthomonas theicola, the Causal Agent of Canker on Tea Plants, Reveals Novel Secretion Systems in Clade-1 Xanthomonads.

Xanthomonas theicola is the causal agent of bacterial canker on tea plants. There is no complete genome sequence available for X. theicola, a close relative of the species X. translucens and X. hyacinthi, thus limiting basic research for this group of pathogens. Here, we release a high-quality complete genome sequence for the X. theicola type strain, CFBP 4691T. Single-molecule real-time sequencing with a mean coverage of 264× revealed two contigs of 4,744,641 bp (chromosome) and 40,955 bp (plasmid) in size. Genome mining revealed the presence of nonribosomal peptide synthases, two CRISPR systems, the Xps type 2 secretion system, and the Hrp type 3 secretion system. Surprisingly, this strain encodes an additional type 2 secretion system and a novel type 3 secretion system with enigmatic function, hitherto undescribed for xanthomonads. Four type 3 effector genes were found on complete or partial transposons, suggesting a role of transposons in effector gene evolution and spread. This genome sequence fills an important gap to better understand the biology and evolution of the early-branching xanthomonads, also known as clade-1 xanthomonads.

High-Quality Genome Resource of Xanthomonas hyacinthi Generated via Long-Read Sequencing.

The bacterial plant pathogen Xanthomonas hyacinthi is the causal agent of yellow disease of Hyacinthus and other ornamental plant genera. There is no available complete genome for X. hyacinthi, limiting basic research for this pathogen. Here, we release a high-quality complete genome sequence for the X. hyacinthi type strain, CFBP 1156. Single-molecule real-time (SMRT) sequencing with a mean coverage of 306× revealed two contigs of 4,918,645 and 44,381 bp in size. This was the first characterized plant-disease-causing species of Xanthomonas and this genome provides a resource to better understand the biology of yellow disease of hyacinth.

Complete Genome Sequence of Pandoraea pnomenusa TF-18, a Multidrug-Resistant Organism Isolated from the Rhizosphere of Rice (Oryza sativa L. subsp. japonica).

Pandoraea pnomenusa strain TF-18 was isolated from the roots of rice seedlings on selective medium containing four classes of antibiotics for isolation of Burkholderia pseudomallei Using Pacific Biosciences (PacBio) single-molecule real-time (SMRT) sequencing technology, we report here a complete genome of 5,499,432 bases, a GC content of 64.8%, and 4,849 coding sequences.

Genome Resource of Barley Bacterial Blight and Leaf Streak Pathogen Xanthomonas translucens pv. translucens strain UPB886.

Xanthomonas translucens pv. translucens causes bacterial leaf streak and bacterial blight diseases of barley. This pathogen limits barley production globally but remains understudied, with limited genomic resources. To better understand the biology of this X. translucens subgroup, we sequenced the complete genome of the X. translucens pv. translucens strain UPB886.

Interactions of free-living amoebae with the rice fungal pathogen, Rhizoctonia solani.

OBJECTIVE: Rhizoctonia solani is a soil-borne fungal pathogen of many important crop plants. In rice, R. solani causes sheath blight disease, which results in devastating grain yield and quality losses. Few methods are available to control this pathogen and classic single gene resistance mechanisms in rice plants have not been identified. We hypothesize that alternate means of control are available in the environment including free-living amoebae. Amoebae are soil-, water- and air-borne microorganisms that are predominantly heterotrophic. Many amoeba species are mycophagous, and several harm their prey using mechanisms other than phagocytosis. Here, we used light and scanning electron microscopy to survey the interactions of R. solani with four amoeba species, with the goal of identifying amoebae species with potential for biocontrol. RESULTS: We observed a wide range of responses during interactions of R. solani with four different free-living amoebae. Two Acanthamoeba species encyst in co-cultures with R. solani at higher rates than medium without R. solani. Vermamoeba vermiformis (formerly Hartmanella vermiformis) attach to R. solani mycelium and are associated with mycelial shriveling and perforations of fungal cell walls, indicating an antagonistic interaction. No phenotypic changes were observed in co-cultures of Dictyostelium discoideum and R. solani.

Temperature Limits for the Brown Wheat Mite, in Colorado.

Brown wheat mites, Petrobia latens (Müller 1776, Acari: Tetranychidae), are sporadic yet economically damaging pests of winter cereals. In Colorado, their life history is closely tied to the development of winter wheat, where they are present in the field from crop planting in late September through harvest in early June. In order to withstand winter months, these mites are able to survive cold temperatures. However, the mechanisms of cold hardening and their temperature limits are unknown. This research documents the seasonal supercooling points of the brown wheat mite. Their seasonal average supercooling point stayed consistent throughout the year, never varying more than a degree from the overall average supercooling point of -17°C. The greatest variation in supercooling point was seen in the spring, during which supercooling point temperatures ranged from -9.2 to -25.5°C. We also documented the upper and lower lethal temperatures for the brown wheat mite. When comparing small nymphs to large nymph and adult stages, small nymphs were slightly more cold tolerant (lethal temperature estimates required to kill 99% of the population [LT99] were -30.8 and -30.6°C, respectively), but less heat tolerant (LT99 was 50 and 56°C, respectively).

Comparative Rice Bran Metabolomics across Diverse Cultivars and Functional Rice Gene⁻Bran Metabolite Relationships.

Rice (Oryza sativa L.) processing yields ~60 million metric tons of bran annually. Rice genes producing bran metabolites of nutritional and human health importance were assessed across 17 diverse cultivars from seven countries using non-targeted metabolomics, and resulted in 378⁻430 metabolites. Gambiaka cultivar had the highest number and Njavara had the lowest number of metabolites. The 71 rice bran compounds of significant variation by cultivar included 21 amino acids, seven carbohydrates, two metabolites from cofactors and vitamins, 33 lipids, six nucleotides, and two secondary metabolites. Tryptophan, α-ketoglutarate, γ-tocopherol/ß-tocopherol, and γ-tocotrienol are examples of bran metabolites with extensive cultivar variation and genetic information. Thirty-four rice bran components that varied between cultivars linked to 535 putative biosynthetic genes using to the OryzaCyc 4.0, Plant Metabolic Network database. Rice genes responsible for bran composition with animal and human health importance is available for rice breeding programs to utilize in crop improvement.

Virulence of Genetically Distinct Geosmithia morbida Isolates to Black Walnut and Their Response to Coinoculation with Fusarium solani.

Geosmithia morbida is well documented as the causal agent of thousand cankers disease of black walnut trees. However, it is not well understood how G. morbida strains differ in virulence and how their interactions with co-occurring pathogens contribute to disease severity. In this study, we systematically investigated virulence of genetically distinct G. morbida strains. Overall, we found varying degrees of virulence, although differences were not related to genetic groupings. Furthermore, the pathogen Fusarium solani is also commonly isolated from thousand canker-diseased trees. The degree of disease contribution from F. solani is unknown, along with interactions it may have with G. morbida. This research shows that coinoculation with these pathogens does not yield a synergistic response.

Erwinia iniecta sp. nov., isolated from Russian wheat aphid (Diuraphis noxia).

Short, Gram-negative-staining, rod-shaped bacteria were isolated from crushed bodies of Russian wheat aphid [Diuraphis noxia (Kurdjumov)] and artificial diets after Russian wheat aphid feeding. Based on multilocus sequence analysis involving the 16S rRNA, atpD, infB, gyrB and rpoB genes, these bacterial isolates constitute a novel clade in the genus Erwinia, and were most closely related to Erwinia toletana. Representative distinct strains within this clade were used for comparisons with related species of Erwinia. Phenotypic comparisons using four distinct strains and average nucleotide identity (ANI) measurements using two distinct draft genomes revealed that these strains form a novel species within the genus Erwinia. The name Erwinia iniecta sp. nov. is proposed, and strain B120T ( = CFBP 8182T = NCCB 100485T) was designated the type strain. Erwinia iniecta sp. nov. was not pathogenic to plants. However, virulence to the Russian wheat aphid was observed.