Manistee is a round white chip-processing potato (Solanum tuberosum) variety developed for long-term storage. Evaluated as MSL292-A, Manistee is a selection from a cross between Snowden and the chip-processing breeding line MSH098-2. The tubers of Manistee are compressed, round with shallow eyes and early to mid-season maturity. Field testing and on-farm trials show that this variety has high yield potential with specific gravity comparable to Snowden and similar to better tolerance to blackspot bruise. Manistee was formally released in 2013 and has demonstrated reliable and excellent long-term storage chip-processing quality up to eight months post-harvest which extends the chip-processing storage season beyond Snowden. Furthermore, preliminary studies with Manistee, Snowden, Lamoka and Pike tuber disks demonstrated that Manistee started the wound healing process faster than Lamoka and Pike and slightly faster than Snowden which supports observations of stable and reliable commercial storage of the tubers for chip-processing.

New fungicide modes of action are needed for fungicide resistance management strategies. Several commercial herbicide targets found in fungi that are not utilized by commercial fungicides are discussed as possible fungicide molecular targets. These are acetyl CoA carboxylase, acetolactate synthase, 5-enolpyruvylshikimate-3-phosphate synthase, glutamine synthase, phytoene desaturase, protoporphyrinogen oxidase, long-chain fatty acid synthase, dihydropteroate synthase, hydroxyphenyl pyruvate dioxygenase, and Ser/Thr protein phosphatase. Some of the inhibitors of these herbicide targets appear to be either good fungicides or good leads for new fungicides. For example, some acetolactate synthase and dihydropteroate inhibitors are excellent fungicides. There is evidence that some herbicides have indirect benefits to certain crops due to their effects on fungal crop pathogens. Using a pesticide with both herbicide and fungicide activities based on the same molecular target could reduce the total amount of pesticide used. The limitations of such a product are discussed.

The Oomycete plant pathogen, Phytophthora capsici, causes root, crown, and fruit rot of winter squash (Cucurbita moschata) and limits production. Some C. moschata cultivars develop age-related resistance (ARR), whereby fruit develop resistance to P. capsici 14 to 21 days postpollination (DPP) because of thickened exocarp; however, wounding negates ARR. We uncovered the genetic mechanisms of ARR of two C. moschata cultivars, Chieftain and Dickenson Field, that exhibit ARR at 14 and 21 DPP, respectively, using RNA sequencing. The sequencing was conducted using RNA samples from ‘Chieftain’ and ‘Dickenson Field’ fruit at 7, 10, 14, and 21 DPP. A differential expression and subsequent gene set enrichment analysis revealed an overrepresentation of upregulated genes in functional categories relevant to cell wall structure biosynthesis, cell wall modification/organization, transcription regulation, and metabolic processes. A pathway enrichment analysis detected upregulated genes in cutin, suberin monomer, and phenylpropanoid biosynthetic pathways. A further analysis of the expression profile of genes in those pathways revealed upregulation of genes in monolignol biosynthesis and lignin polymerization in the resistant fruit peel. Our findings suggest a shift in gene expression toward the physical strengthening of the cell wall associated with ARR to P. capsici. These findings provide candidate genes for developing Cucurbita cultivars with resistance to P. capsici and improve fruit rot management in Cucurbita species.

Armillaria root rot (ARR), caused by Armillaria species and Desarmillaria tabescens , is a severe disease that affects stone fruit trees in the United States. One strategy to mitigate the impact of this disease is to develop ARR-resistant rootstocks. However, current techniques to screen Prunus species for resistance to ARR are time-consuming, labor-intensive, and may not fully replicate field conditions. To address these limitations, we developed a new rapid in vitro screening assay, which uses roots of 2-year-old Prunus rootstock genotypes. We screened 12 Prunus genotypes against Armillaria mellea , Armillaria solidipes , and Desarmillaria tabescens in vitro. Freshly excavated root segments were placed next to or on top of fungal cultures. After 21 days, the circumferential percentage and horizontal length of the fungal colonization and the ability of the fungus to enter through root periderm were evaluated. The root tissue surrounding the infection was also evaluated to assess any response reactions against the ARR pathogens. Our results showed that inoculated root tissues displayed signs of fungal infection, and infection and host responses varied among the Prunus genotypes. Host responses similar to those observed in the field, such as compartmentalization of infected tissue with barrier zones, necrophylactic periderm formation, and callus formation on root surfaces, were observed and were more evident in less susceptible genotypes. In conclusion, our newly developed assay, which uses freshly excavated roots from 2-year-old rootstocks, can rapidly screen Prunus genotypes for resistance to ARR.

Armillaria root rot (ARR) is a major threat to the long-term productivity of stone fruit and nut crops across the major production areas in the US. There are no efficient methods of eradicating the long-lived inoculum buried in the soil before replanting, nor are there therapeutic methods to offset reduced productivity and tree death. Loss of productive land for the stone fruit and nut producers due to ARR is already happening. Without immediate short- and long-term actions, prime Prunus orchard land will be permanently out of production, resulting in a devastating effect on the industries and local communities. Causal pathogenic fungi consist of three geographically isolated species: Armillaria mellea in California, A. solidipes in Michigan, and Desarmillaria tabescens in the southeastern US. The most economical and sustainable approach to prevent the loss of peach, cherry, and almond production due to Armillaria infection is to develop ARR-resistant, horticulturally acceptable rootstocks. A trans-disciplinary, multi-crop, multi-institutional team of researchers, growers and nursery representatives are dedicated to finding short- and long-term solutions for the ARR replant issue affecting the US stone fruit industry. This project will provide the 'building blocks' needed to enable and accelerate on-going Prunus breeding programs, as well as support the testing of cultural practices for short-term solutions to increase tree longevity on replant sites.

Age-related resistance (ARR), or ontogenic resistance, is associated with host developmental stages. Winter squash fruit (Cucurbita moschata) develops resistance to the oomycete plant pathogen, Phytophthora capsici, as they mature. ARR in winter squash to P. capsici could be exploited to assist growers in limiting crop loss due to fruit rot. The objective of this study was to determine whether preformed or pathogen-induced antifungal activity during fruit development is correlated with ARR. We examined fruit peel methanol/ethanol extracts of three cultivars of C. moschata at different developmental stages with and without P. capsici inoculation. Results indicated the presence of compounds with antifungal activity in all fruit ages tested, but the antifungal activity decreased with age indicating a lack of association between preformed antifungal activity and ARR in winter squash. In addition, no significant change was detected in the antifungal activity among fruit ages that were inoculated with P. capsici and examined at different times post inoculation, suggesting no association between the induced antifungal activity and ARR in winter squash.

Wounding during mechanical harvesting and post-harvest handling results in tuber desiccation and provides an entry point for pathogens resulting in substantial post​-harvest crop losses. Poor wound healing is a major culprit of these losses. Wound tissue in potato (Solanum tuberosum) tubers, and all higher plants, is composed of a large proportion of suberin that is deposited in a specialized tissue called the wound periderm. However, the genetic regulatory pathway controlling wound-induced suberization remains unknown. Here, we implicate two potato transcription factors, StMYB102 (PGSC0003DMG400011250) and StMYB74 (PGSC0003DMG400022399), as regulators of wound suberin biosynthesis and deposition. Using targeted metabolomics and transcript profiling from the wound healing tissues of two commercial potato cultivars, as well as heterologous expression, we provide evidence for the molecular-genetic basis of the differential wound suberization capacities of different potato cultivars. Our results suggest that (i) the export of suberin from the cytosol to the apoplast and ligno-suberin deposition may be limiting factors for wound suberization, (ii) StMYB74 and StMYB102 are important regulators of the wound suberization process in tubers, and (iii) polymorphisms in StMYB102 may influence cultivar-specific wound suberization capacity. These results represent an important step in understanding the regulated biosynthesis and deposition of wound suberin and provide a practical foundation for targeted breeding approaches aimed at improving potato tuber storage life.

Plant diagnostic laboratories (PDLs) are at the heart of land-grant universities (LGUs) and their extension mission to connect citizens with research-based information. Although research and technological advances have led to many modern methods and technologies in plant pathology diagnostics, the pace of adopting those methods into services at PDLs has many complexities we aim to explore in this review. We seek to identify current challenges in plant disease diagnostics, as well as diagnosticians' and administrators'perceptions of PDLs' many roles. Surveys of diagnosticians and administrators were conducted to understand the current climate on these topics. We hope this article reaches researchers developing diagnostic methods with modern and new technologies to foster a better understanding of PDL diagnosticians' perspective on method implementation. Ultimately, increasing researchers' awareness of the factors influencing method adoption by PDLs encourages support, collaboration, and partnerships to advance plant diagnostics.

The introduction of pharmaceuticals into agricultural lands from the application of biosolids and animal manure, and irrigation with treated wastewater has led to concern for animal and human health after the ingestion of pharmaceutical-tainted agricultural products. In this study, the uptake and accumulation of cephalexin, a commonly prescribed antibiotic, was compared in three common vegetables (lettuce, celery, and radish) grown in nutrient solution for 144 h. During the uptake experiments, cephalexin concentration in the nutrient solution decreased in the order of radish > celery > lettuce, while the accumulation of cephalexin in vegetable roots followed the rank of lettuce > celery > radish. The accumulation of cephalexin was below the limit of detection in radish roots. No accumulation of ceph-alexinwas observed in the shoots of all three vegetables. The behaviors of cephalexin in vivo were further elucidated using in vitro measurements of cephalexin sorption by vegetable roots and transformation in plant enzyme extracts. The affinity of cephalexin to lettuce > celery > radish roots, and the respective sorption coefficients of 687, 303, and 161 mL g(-1), coupled to the transformation of cephalexin in root enzyme extracts with estimated reaction rate constants of 0.020, 0.027 and 0.024 hr(-1) for lettuce, celery and radish, could help elucidate the accumulation observed in the in vivo experiments. Overall, sorption by plant roots (affinity) and reaction with plant enzymes could collectively influence the uptake and accumulation of cephalexin in vegetables. (C) 2020 Elsevier Ltd. All rights reserved.

The National Plant Diagnostic Network (NPDN), comprising diagnostic professionals from more than 70 pathology, entomology, and nematology laboratories, safeguards U.S. plant systems through accurate diagnosis and effective communications with clients, partners, and stakeholders. As a USDA-NIFA extension program built on the land-grant university system, the network has dual responsibilities to extension clientele such as farmers and the green industry, as well as state and federal regulatory agencies. Following strategic planning in 2019, the network emerged with a concise plan and strong committees of network participants to enhance and sustain service to NPDN clientele and partners, even through significant disruptions like the 2020 coronavirus pandemic. The commitment to building diagnostic capacity and expertise across the country allows these plant clinics to assist during a response to detections of high-consequence plant pathogens by clearing healthy plants for commerce while identifying potential positives for regulators to quarantine and/or eradicate, similar to the test and trace efforts for human diseases such as COVID-19. In this review, we describe the network's recent activities to protect U.S. plant agriculture and natural ecosystems and its plans to improve and expand capacity for national plant biosecurity.

Common scab of potato caused by pathogenicStreptomycesspecies poses an economic burden to commercial potato cultivation. Despite decades of research, no molecular markers linked to this trait are currently available, making the development of scab resistant potato varieties inefficient. We evaluated common scab lesion type and tuber coverage in 198 individuals segregating for common scab resistance in replicated field trials with high natural disease pressure over two growing seasons. To identify genetic features associated with resistance, we genotyped the tetraploid (4x) population and parental lines (Kalkaska and Tundra) using the Illumina Infinium 8303 Potato Array and conducted genome-wide association analysis. Here, we report two significant single nucleotide polymorphism (SNP) markers on chromosome 1 associated with both scab traits in both years as well as a SNP marker on chromosome 2 associated with scab tuber coverage. Gene expression profiling of the parents of this population in response to Thaxtomin A treatment revealed differential expression of genes in tubers putatively involved in cell wall biosynthesis and hormone signaling.

Variation in susceptibility of 28 Prunus rootstock genotypes to the causal agents of Armillaria root rot, Armillaria mellea , A. solidipes, and Desarmillaria tabescens , were studied by conducting in vitro root screening assays. Root segments with wounded and intact periderm were placed next to and on the top of the fungal cultures. At day 21, the percent success of fungal penetration and the circumferential and longitudinal lengths of fungal growth were measured. A parallel investigation using the inoculated root segments was carried out to characterize the active host defense mechanisms involved, including anatomical responses in bark and wood. Overall, the success of penetration and the longitudinal and circumferential spread of Armillaria spp. and D. tabescens were significantly different among various Prunus rootstock genotypes. None of the tested rootstock genotypes were completely resistant to infection. However, plum and plum derived rootstocks, and some of the cherry genotypes were less susceptible to infection compared to the peach genotypes. The host’s ability to limit infection by Armillaria spp. and D. tabescens was not limited to a single mechanism but appeared to be regulated by several collective nonspecific host responses acting together. Differential levels of a series of non-specific coordinated events were triggered in Prunus genotypes such as the formation of new callus tissue on the root surface, a colored reaction zone, necrophylactic periderm, new cells, and new vascular cambium to compartmentalize the pathogen. The host responses were elevated in the genotypes with low level of infection as compared to highly infected genotypes.

Armillaria mellea and A. solidipes are two of the primary causal agents of Armillaria root rot (ARR) in over 500 woody hosts. Although extensive research on this disease has been conducted over the past few decades, finding controls for ARR has been challenging. This is largely due to the lack of knowledge of the fungal infection and host response processes. It is important to understand the infection process in order to develop new strategies to control the disease. In this review, the initial steps of the infection process of A. mellea and A. solidipes are discussed, with focus on fungal attachment and penetration. A mucilaginous substance produced at the rhizomorph tip is thought to aid attachment of the pathogen to host. Toxins and cell wall degrading enzymes produced by the fungus together with mechanical pressure generated by the rhizomorph is speculated to support fungal penetration. However, a detailed description of the Armillaria spp. infection process is lacking in the literature, and this illustrates the need for further studies.