Douglas G. Luster

Boxwood blight threatens the United States’ leading evergreen ornamental shrub and the broader green industry it supports. This study synthesizes 4 years of research from the Boxwood Blight Insight Group (BBIG), a transdisciplinary consortium that developed diagnostics, risk tools, resistant cultivars, microbiome-based interventions, and best management practices. We quantified the economic, environmental, and societal returns from these innovations using several analytical tools. These include a structured benefit inventory that avoids double-counting, empirically grounded adoption curves, and standard public-sector discounting at 3%. We also monetized externalities such as the social cost of carbon. The analysis translates over 66 documented journal articles and impact statements into defensible monetary values. Direct producer benefits total to a net present value (NPV) of $1.2 billion over 10 years. These benefits include higher net margins, avoided crop losses, and lower input costs. The largest contributions come from cultivar resistance, precision sanitation, and weather-based spray optimization. When we add monetized environmental and regulatory savings, the NPV increases by $180 million. Including consumer and societal spillovers raises the aggregate benefits to $1.6 to 2.1 billion. Even under conservative assumptions—30% adoption and excluding “soft” benefits—the program yields a 21:1 benefit–cost ratio relative to cumulative research investment. These findings demonstrate that embedding economic analyses within plant health R&D can accelerate adoption and guide policy design. This approach also helps safeguard an iconic landscape plant whose wholesale value exceeds $140.9 million annually and supports a much larger downstream market. The BBIG provides a repeatable template for integrating disease biology with economic evaluation to capture the full public return to specialty-crop research. [ ] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a persistent threat to Ethiopian wheat production, posing risks to food security. This study evaluated the virulence and genotypic diversity of the Pgt population following the stem rust epidemic in 2013, and the vulnerability of Ethiopian bread wheat cultivars to the newly identified Pgt races. We analyzed 639 stem rust samples collected between 2014 and 2022 in Ethiopia and identified 21 Pgt races from 722 single-pustule isolates. The Ethiopian Pgt population has undergone significant temporal shifts driven by exotic race introductions and possibly by selection pressure. Race TKTTF (clades IV-A and -B) dominated in 2014-2016 seasons but was largely replaced by races TTRTF (clade III-B) and TKKTF (clade IV-F) from 2017 onward. Since 2020, races TTKTT (clade I) and TTKTF (clade IV-F) were detected with increasing frequencies, emerging alongside TKKTF as the predominant races by 2022. All major races from genetic clades III and IV detected in Ethiopia exhibit a similar, broad geographic distribution with a likely origin in the Caucasus region. All five variants in the Ug99 race group (clade I) observed in Ethiopia were previously detected in Kenya, suggesting a potential incursion from this bordering country. Races BKBJC and BKGKC with distinct avirulence and genotypic profiles were derived from a sample collected near the alternate host Berberis holstii, suggesting that these avirulent isolates likely originated through sexual recombination. Seedling assays of 101 Ethiopian bread wheat cultivars against six prevailing races showed varying resistance, with only 36% and 48% resistant to race TTKTT and TTKSK, respectively. Although resistance genes deployed in Ethiopian cultivars do not appear to have exerted significant selection pressure favoring races TTRTF and TKKTF, the increased deployment of Sr24 in recent years may have contributed to the establishment and dissemination of race TTKTT. Our findings emphasize the need for breeding wheat cultivars with pyramided effective resistance genes and continuous pathogen surveillance to preempt future stem rust epidemics in Ethiopia and beyond.

Although WSR has been commonly observed and studied in the Middle East, in Jordan the last reports date from the late 1980s. The objectives of this research were to conduct a national survey of WSR in Jordan, assess the race composition and genotypic diversity of the Pgt population and to evaluate a 162 durum wheat genotypes for stem rust response against isolates of two major Pgt races recovered from stem rust samples collected in this study. A total of 78 WSR live samples and 74 dead samples from 49 fields were collected in 2018. In addition, three historical samples were analyzed. One hundred Pgt isolates derived from the live samples were race-typed and 14 representatives of the identified races were genotyped with a 17 core SNP assay that distinguish major genetic clades. The dead and the historical Pgt samples were all SNP genotyped. Five races were identified from the live samples: PKTTF, TKFTF, TKFTP, TKKTF, and TTRTF. The most frequent race was TKKTF (75%) followed by TKFTF (14%), and TTRTF (9%), whereas races PKTTF and TKFTP were detected from only one isolate each. Selected Pgt isolates representing the five races identified were differentiated into five known genetic clades/sub-clades: III-B, race TTRTF; IV-C, race PKTTF; IV-E.1, race TKFTP; IV-E.2, race TKKTF; and IV-F, race TKFTF. The dead samples were genotyped as clades: IV-E.2 (73.7%), III-B (18.1%), and IV-E.1, IV-F, and Co-A22 at frequencies less than 4%. Minor allelic variations at one or two SNP loci were observed among the dead samples. The dead sample genotyped as Co-A22 was identical to European reference isolates from the early 1980s. From the 36 single uredinial pustules derived from the historical samples, two genotypes were detected: clade III-A and, Co-A22. Seedling resistance was observed in durum wheat landraces and cultivars to two of the major races identified in Jordan, as 52 (32.1%) and 99 (61.1%) genotypes evaluated exhibited a resistant response to races TTRTF and TKKTF, respectively. Infection types in the range of ‘2-’ to ‘2+’ were predominant in this germplasm. Forty-six (28.4%) accessions were resistant to both races, including 1 cultivar and 45 landraces.

To have confidence that results from diagnostic assays for plant pathogens are accurate and to identify potential problems with false negatives and false positives, it is essential that the appropriate control reactions are included in the assay design. This review discusses control reactions that, depending on the technology used, should be either run in parallel or multiplexed with the diagnostic assay to ensure accuracy. The discussion includes immunoassays such as enzyme-linked immunosorbent assay and lateral flow devices, as well as molecular diagnostic techniques including PCR, isothermal technologies (recombinant polymerase amplification and loop-mediated isothermal amplification), and high-throughput sequencing. Additional details are provided for RNA virus assays that account for the need for a control reaction during the generation of complementary DNA. Although concepts of control reaction design and the reasons for their inclusion are discussed, the reader is directed to the Diagnostic Assay Validation Network website hosted on the American Phytopathological Society website for specific examples of control reactions reported in the literature that may be useful to consider when designing new diagnostic assays. [ ] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

This study evaluated the progress in validating plant pathogen diagnostic assays by comparing recent literature (2023 to 2024) with previous assessments, particularly following the recommendations of Sharma and Luster (2023). Diagnostic accuracy relies on metrics such as analytical and diagnostic specificity, sensitivity, repeatability, and reproducibility, essential for robust diagnostics and effective disease management. Our analysis of recent publications shows increased emphasis on analytical specificity and sensitivity, reflecting improvements, although consistent application of comprehensive validation remains limited. Technologies such as real-time PCR and loop-mediated isothermal amplification (LAMP) continue to be prominent, while emerging methods such as recombinase polymerase amplification (RPA)-CRISPR/Cas12a show potential for rapid, sensitive detection. The findings underscore the need for more uniform validation practices, statistical rigor, and inclusion of all metrics to enhance the reliability, reproducibility, and field utility of diagnostic tools. This continued focus is crucial for advancing plant health management and meeting diverse diagnostic demands. [ ] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Phytophthora ramorum is an invasive, federally regulated pathogen in the United States, with at least 75 confirmed hosts and over 100 associated hosts. The movement of ornamental plants infected with P. ramorum, as a regulated pathogen, across the United States resulted in a surge of samples experienced by diagnostic laboratories, underscoring the need for a specific and rapid screening assay. This work adapted and validated a previously published P. ramorum recombinase polymerase amplification (RPA) diagnostic tool for commercial application. This assay was validated through inclusivity testing for the four P. ramorum lineages and exclusivity testing on a panel of Phytophthora species and other commonly detected oomycetes. The reformulated assay demonstrated sensitive and specific detection of P. ramorum down to 1 fg for each lineage, without cross-reacting with over 100 different oomycetes across at least 30 hosts. The RPA assay underwent three tiers of validation. In Tier 1, a single-lab, multi-operator validation, it achieved diagnostic specificity and sensitivity of 100 and 92%, respectively, with 100% reproducibility and repeatability among operators. Tier 2 validation, performed on a blind sample set at two independent labs, resulted in 100% diagnostic specificity and sensitivity. Tier 3 involved a blind performance study across five independent labs using multiple fluorescent cycler platforms and operators. The reformulated RPA assay offers a rapid and simple approach for the molecular detection and identification of P. ramorum. [ ] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Phyllosphere colonizers, including bacteria and fungi, are critical for plant growth and health. However, how they are affected simultaneously by the host plant cultivar, local environment, and agricultural practices was not well understood. We used boxwood, an iconic landscape plant and a major evergreen shrub crop in the United States nursery industry, as a model plant and sequenced 16S rRNA and ITS amplicons to examine the assemblages of endophytic bacteria and fungi in the shoots of four cultivars representing three levels of boxwood blight resistance under two distinct climates and production systems in Oregon and Virginia. Cultivar and local environment were the two main drivers shaping the composition and structure of the boxwood endophytic microbial community, particularly the fungal community. Three bacterial and seven fungal genera were consistently identified with high prevalence and abundance as the core taxa from four cultivars and two locations across three sampling times. The microbial composition varied among the levels of boxwood blight resistance, and taxa specific to the tolerant cultivar were fewer compared to the susceptible one. Identification of these microbial indicators, along with the core taxa, is foundational for developing a microbiome-based plant breeding program and a systems approach to improve boxwood health and production under a changing climate. [ ] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Red leaf blotch is a severe soybean disease caused by the select agent fungal pathogen Coniothyrium glycines. With little information about the pathogen, no molecular detection methods are available. Here, we report genome assemblies of five isolates, including reference isolates. These datasets provide a valuable resource for ongoing studies that include marker development, diagnostics, and population diversity. [ ] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .