Crop rotations are key to conditioning the soil biotic community that underpins agricultural productivity. For instance, mustards and pearl millet have the potential to alter soil biota and suppress soil diseases prior to a cash crop. Here we explore the effects of various combinations of brown mustard and pearl millet rotational treatments on potato yield, soil and root associated biota. Brown mustard (var. Caliente-199) and pearl millet (var. CFPM-101) were grown in all possible pairwise rotational combinations and in mixtures two years prior to potato to assess their impact on root lesion nematodes (RLN) and Verticillium dahliae in the soil and the root microbiome of potato. Treatments included an intensive two-year potato-barley rotation and two-year perennial reduced tillage treatments of barley underseeded with a red clover–timothy mixture and a diverse crop mixture. Potato yield increased significantly with greater aboveground biomass of pearl millet produced in previous years. The potato root associated microbiome varied among cropping treatments which strongly corresponded with both potato yield and pearl millet biomass. V. dahliae was highest and the potato disease symptoms progressed faster in soils following potato. RLN only increased in both the two-year perennial treatments, likely due to the presence of host crops which resulted in the lowest potato yield. Pearl millet grown within two years prior to potato can significantly support potato yields by limiting RLN population growth and conditioning the potato root associated microbiome.

Conservation tillage has shown potential to improve soil health and enhance crop productivity in various cropping systems. Moldboard plowing (MP) in the fall prior to the potato phase is a conventional practice in Prince Edward Island (PEI), Canada, which leaves the soil prone to erosion and soil organic matter decline. Potato early dying disease complex (PED) is a major yield limiting factor in potato production in PEI. The objective of this four-year (2019–2022) study conducted in 14 commercial fields was to determine the effect of non-inversion shallow tillage (ST) in comparison with MP on PED pathogen population density in the spring at potato planting time and in the fall post-potato harvesting, and on PED disease severity. Root lesion nematodes (Pratylenchus spp., RLN) were detected in all fields. Verticillium dahliae was the predominant species in all fields, while V. albo-atrum was sporadically detected in a few samples. The population density of the RLN and V. dahliae varied among the fields. In the spring samples, V. dahliae density was significantly higher in 5 of the 14 fields with the ST treatment compared with MP. RLN density was significantly higher in one of the 14 fields with the ST. When averaged across all fields, V. dahliae density was 1.8-fold higher with ST than with MP (p = 0.018), but no differences were detected for RLN density between ST and MP. In the fall after the potato harvest, only two fields had significantly higher V. dahliae density with the ST than with MP, and no differences were detected for RLN density between ST and MP. When combined data across all fields were analyzed, no differences in pathogen population levels were detected between ST and MP for both V. dahliae and RLN. Higher PED severity was detected in three fields associated with ST. However, when disease ratings were averaged across all fields, no PED severity difference was detected between ST and MP. The PED severity was significantly positively related to the spring population density of V. dahliae and RLN, but not with the tillage regimes in this study. Further study is needed to determine the long-term effect of tillage regimes on soil health, disease development, soil disease suppressiveness, pathogen population dynamics and PED development in potato production.

Potato (Solanum tuberosum L.) production often requires intensive tillage with the moldboard plow (MP), which involves deeper soil tillage and turning of the soil to provide enough loose soil for proper tuberization. Although tillage with the MP allows better potato seedbed preparation and lower weed pressure, it is also associated with increased soil compaction, soil aggregate destruction, and increased soil organic matter (SOM) mineralization. The objective of this four-year (2019–2022) study conducted in 14 commercial fields was to compare the use of MP with primary non-inversion shallow tillage (ST) in terms of their effect on selected soil health indicators, soil moisture, potato petiole nitrate concentration, potato yield, and specific gravity. Commercial fields ranged from 1.5 ha to 19 ha where the main field was split in half, with one side tilled using MP (22.5–30 cm plowing depth) and the other half using ST (15–30 cm plowing depth). Soil and plant tissue samples were taken within four sub-replicates (91 m2) created per each treatment per each site and three to four sites were used as replicates per each year. Compared to MP, ST increased active carbon by an average of 9%, soil respiration by an average of 26%, and aggregate stability by an average of 8%. Biological N availability (BNA) increased by an average of 20% with ST, and the effect was statistically significant in three out of four years. Soil moisture at 20 cm depth tended to be higher with MP than ST in three out of four years. Although not statistically significant, when averaged across four years, potato petiole nitrate concentrations were 5% and 12% higher with ST than MP in samples collected at the flowering and post-potato flowering stages, respectively. Total and marketable potato yields, along with specific gravity, were comparable for the two tillage regimes. Signs of soil improvement were observed at the early stages of ST adoption. Marketable yield was negatively correlated with the soil nitrate levels measured during the growing season but was positively correlated with active carbon, aggregate stability, and soil moisture. Future studies could compare both tillage regimes over multiple growing seasons to assess their impacts over a full cycle of rotation. The novelty of the present study was that it was conducted in real-life conditions across large growers’ fields with different conditions and across four years.

A survey of New Brunswick (NB) and Prince Edward Island (PEI) potato fields in crop rotation phase prior to potato production was conducted in fall (October and November) between 2017 and 2021. A total of 113 and 126 fields for NB and PEI, respectively, were surveyed with 20 to 35 fields each year tested in each province. Root lesion nematodes (RLN, Pratylenchus spp.) were detected in 99 and 98% of the fields for NB and PEI, respectively, and two root lesion nematode species, P. crenatus and P. penetrans, were identified in both provinces from 2017 to 2021. Based on 2019 and 2020 results, all surveyed fields in NB and PEI were detected with P. crenatus, while only 29 and 43% of the fields in NB and PEI were detected with P. penetrans, respectively. P. crenatus accounted for 96 and 89% of the populations for NB and PEI, respectively, while P. penetrans accounted for 4 and 11% in commercial fields, respectively. In a single in-depth sampled experimental field with a history of severe potato early dying complex in 2018 in NB, P. crenatus accounted for 88% and P. penetrans was 12%. Verticillium dahliae was detected in 94 and 92% of potato fields in NB and PEI, respectively. All isolates obtained from potato cv. "Russet Burbank" in a baiting trial were V. dahliae, belonging to two lineages. V. albo-atrum was detected in a few fields at very low level, except two fields in NB where V. albo-atrum was predominating over V. dahliae. Rotation crops did not affect V. dahliae population densities for NB and PEI, and did not affect RLN population in NB, but significantly affected RLN in PEI. Fall green cover crop did not affect the populations of RLN and V. dahliae in PEI. The present study revealed that the potato pathogenic root lesion nematode P. penetrans was present in less than 50% of surveyed fields and accounted for around 10% of root lesion nematode population in NB and PEI, and V. dahliae was the dominant species and was present in greater than 90% of surveyed fields in both provinces.

Verticillium dahliae is an important soilborne pathogen causing Verticillium wilt. It is also the primary causal agent of potato early dying, a disease complex involving the root-lesion nematode. Here, we report the whole-genome sequencing of 192 isolates of V. dahliae originating from the major potato production areas across Canada. Our results yielded a resource of 277,010 genetic variations that will be useful for genetic analyses and revealed the presence of two major lineages, both present in all provinces but exhibiting differences in regional prevalence. [Formula: see text] Copyright © 2023 His Majesty the King in Right of Canada, as represented by the Minister of Agriculture and Agri-Food Canada. This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Disease suppressive crops grown prior to a cash crop is an ecological strategy to promote cash crop yields through soil biome conditioning. We investigated whether combining such crops in mixtures and rotational sequences is an effective tool for soil biome conditioning to promote potato yield. Mustard and millet were selected for the control of two devasting potato diseases – root lesion nematode (RLN) and Verticilium. These disease suppressive crops were used in monocultures, rotational combinations, and mixtures over the two years prior to a potato cash crop. Both crops were associated with reduced Verticilium abundance, but Verticillium was not abundant in our system. Millet sown in greater abundance prior to potato was positively associated with yield which could in part be linked to its targeted effect on RLN reduction. Importantly, millet had the strongest positive legacy effect on yield through non-targeted effects on the bacterial and fungal communities that associated with the succeeding potato cash crop roots. These results show that while these crops may be used to target specific soil pathogens, there are several non-targeted effects on the soil biome that contribute to a strong legacy effect on yield. These findings further infer that millet can be used to engineer a beneficial soil microbiome for potato crop production. However, its inclusion in mixtures at lower seeding rates within a rotation may diminish its beneficial effects.

A survey on field pea (Pisum sativum) root rot was carried out in Prince Edward Island (PEI) and New Brunswick (NB), Canada, between July and August, 2018. The average disease incidence was 75% and 78%, and severity was 3.5 and 2.8 on a 1 to 7 scale for NB and PEI, respectively (Schneider and Kelly 2000). Symptoms included seedling stunting, root rot, and wilting. Surface sterilized diseased root segments were incubated on water agar at 25°C for 5 days. Pure isolates were obtained by single spore culturing. A total of 210 isolates were identified as Fusarium spp. Five isolates were identified as F. commune by morphological and molecular characteristics (Leslie and Summerell, 2006; Skovgaard et al. 2003). The isolates on Potato Dextrose Agar produced whitish fluffy mycelia on the upper surface and grayish yellow coloration on the bottom surface of the colony cultured at 25°C in darkness. The isolates on carnation leaf agar at 25°C in darkness formed abundant chlamydospores and macroconidia but rare microconidia with 0 to1 septa, measuring 6.2 to 12.5 x 2.7 to 3.6 µm (n = 5). Macroconidia were typically fusiform with a slightly curved apical cell and a foot-shaped basal cell, bending equally toward both ends. Three-septate conidia were 26.8 to 39.3 x 3.6 to 4.5 µm (n = 20) and five-septate conidia were 56.2 to 64.3 x 4.5 to 5.4 µm in size (n = 10). Chlamydospores were smooth, terminal, and single, 7 to 12.5 µm in diameter (n = 20). Genomic DNA of the five isolates were used to amplify and sequence the translation elongation factor 1α (TEF-1α) and the mitochondrial small subunit ribosomal DNA (mtSSU rDNA) using EF1/EF2 and NSM1/NSM2 primer pairs (White et al 1990; O'Donnell et al 2000), respectively, which were used to define the F. commune (Skovgaard et al. 2003). The mtSSU rDNA sequences were deposited in GenBank, OP752229 to OP752232 and OP752234 for isolates GR11-8, GR11-9, GR1-21, FRDC11-1 and FRDC11-2, respectively, and the TEF-1α sequences were assigned OP831956 to OP831959 and OP831961 for GR11-8, GR11-9, GR1-21, FRDC11-1, and FRDC11-2, respectively. The sequence similarities of the five isolates with ex holotype culture NRRL 31076 ranged from 98.69% to 99.79% for the TEF-1α (AF362263.1), with the matching base pairs of 526/533, 523/528, 483/484, 497/502 and 527/533, respectively, and 99.83 to 100% for the mtSSU rDNA (AF362279.1), with the matching base pairs of 633/634, 633/634, 600/601, 633/634, and 621/621, respectively. The sequences of mtSSU rDNA and TEF-1α for the F. commune type species and related Fusarium species were retrieved from NCBI. A phylogenetic tree constructed using the combined sequences of mtSSU rDNA and TEF-1α showed the five isolates clustered with F. commune. Three isolates (GR11-8, GR11-9, GR1-21) were used for pathogenicity testing with four replicates of four plants each and the trial was repeated twice. Seeds of field pea (CDC Limerick) were soaked in 2% sodium hypochlorite for 2 minutes, washed three times with sterilized distilled water, and then were soaked in conidial suspension at 2 × 106 conidia / mL or in sterilized distilled water as a control for 16 h in darkness at 20°C. Seeds were placed in sterilized vermiculite in a greenhouse at 24 / 18°C day / night temperature with a 16 h photoperiod. Three weeks after planting, the tested isolates were observed to cause seed decay, root rot, and seedling stunting, with disease severity ranging from 5 to 7 based on 1 to 7 scale in repeated trials. No symptoms were observed on the control plants. F. commune isolates were re-isolated and confirmed by sequencing the mtSSU rDNA and TEF-1α. F. commune was reported in Alberta causing soybean root rot (Zhou et al. 2018) but this is the first report of F. commune causing root rot of field pea in Canada. Considering its high pathogenicity in field pea and in soybean, the prevalence, host range and geographic distribution of this pathogen need further study.

Biofumigation has been proposed as an alternative to soil fumigation to manage soil-borne diseases including potato early dying disease complex (PED). This study examined the potential of using brown mustard (Mustard juncea) biofumigation to manage PED under rain-fed potato production in New Brunswick, Canada in two trials between 2017 and 2020 in comparison with chloropicrin fumigation and a conventional barley rotation. Biofumigation increased yield in one trial, but not in a second trial where the potato crop experienced severe drought, whereas chloropicrin fumigation increased yield in both trials. Biofumigation was effective in suppressing root-lesion nematode (RLN, Pratylenchus spp.) counts in both trials, but was ineffective in suppressing V. dahliae population density. Chloropicrin fumigation was effective in suppressing RLN counts and V. dahliae population density only in the hill where injected, but the effect was short-lived as the population density of V. dahliae in the hill increased to the level of the control in one potato growing season. Biofumigation may be an alternative to chloropicrin fumigation in managing PED, particularly in fields with high RLN population but relatively low Verticillium population density. However, neither biofumigation nor fumigation used alone may be sustainable in the short-term potato rotations commonly used in New Brunswick, and additional beneficial practices are required to sustain productivity in the long-term.

Under intensive low residue agricultural systems, such as those involving potato (Solanum tuberosum L.)-based systems, stagnant crop yields and declining soil health and environmental quality are common issues. This study evaluated the effects of pen-pack cow (Bos Taurus) manure application (20 Mg·ha−1) and cover crops on nitrate dynamics and soil N supply capacity, subsequent potato yield, selected soil properties, and soil-borne disease. Eight cover crops were tested and included grasses, legumes, or a mixture of legumes and grasses, with red clover (Trifolium pratense L.) used as a control. Forage pearl millet (Pennisetum glaucum L.) was associated with highest dry matter. On average, red clover had 88% higher total N accumulation than the treatments mixing grasses and legumes, and the former was associated with higher soil nitrate in fall before residue incorporation and overwinter, but this was not translated into increased potato yields. Pearl millet and sorghum sudangrass (Sorghum bicolor × sorghum bicolor var. Sudanese) were associated with lower soil nitrate in comparison to red clover while being associated with higher total potato yield and lower numerical value of root-lesion nematodes (Pratylenchus penetrans), although this was not statistically significant at 5% probability level. Manure incorporation increased total and marketable yield by 28% and 26%, respectively, and increased soil N supply capacity by an average of 44%. Carbon dioxide released after a short incubation as a proxy of soil microbial respiration increased by an average of 27% with manure application. Our study quantified the positive effect of manure application and high-residue cover crops on soil quality and potato yield for the province of Prince Edward Island.

Fusarium dry rot (FDR), caused by Fusarium species is an important potato disease world-wide and causes post-harvest rotting and seed-piece decay after planting. In this study, we compared two inoculation methods - cork borer wounding (CBW) and plastic screw wounding (PSW) – for consistent and reproducible disease development in potatoes. A plastic screw was used as a tool to make nearly identical wounds and simultaneously deliver similar quantities of inoculum into tubers, while at the same time sealing the wound in a single step. The PSW method resulted in tuber dry rot severities comparable to that obtained using the traditional CBW method. Tuber rot severities obtained using the two methods were highly correlated in the same sets of tubers, among the three inoculations conducted at different time periods (r values ranging from 0.56–0.95; p < 0.001) for both years of the study. The PSW inoculation method condensed the wounding, inoculum delivery and wound sealing into a single step, thus saving considerable time when compared to the CBW inoculation method. The single use of individual plastic screws can also prevent cross-contamination from non-target microorganisms, which may reside inside the surface-sterilized tubers. The PSW method can be efficiently used to screen potato breeding lines for resistance to Fusarium dry rot.

In this study, a set of duplex reverse transcription PCR (RT-PCR)-mediated high-resolution DNA melting (HRM) analyses for simultaneous detection of potato mop-virus (PMTV) and its protist vector, Spongospora subterranea f. sp. subterranea (Sss), was developed. The infestation of soil by PMTV was detected with a tobacco-based baiting system. Total RNA extracted from the soil led to successful RT-PCR gel electrophoresis detection of both PMTV and Sss. To facilitate more efficient detection, newly designed primer pairs for PMTV RNA species (i.e., RNA-Rep, RNACP, and RNA-TGB) were analyzed together with the existing Sss primers via real-time RT-PCR. The resulting amplicons exhibited melting profiles that could be readily differentiated. Under duplex RT-PCR format, all PMTV and Sss primer combinations led to successful detection of respective PMTV RNA species and Sss in the samples by HRManalyses. When the duplex HRM assay was applied to soil samples collected from six fields at four different sites in New Brunswick, Canada, positive detection of PMTV or Sss was found in 63 to 100% samples collected from fields in which PMTV-infected tubers had been observed. In contrast, the samples from fields where neither PMTV- nor Sss-infected tubers had been observed resulted in negative detection by the assay. Bait tobacco bioassay for PMTV and Sss produced similar results. Of the soil samples collected from PMTV-infested fields, 63 to 83% and 100% led to PMTV and Sss infections in the bait tobacco plants, respectively, whereas no PMTV- or Sss-infected plants were obtained from soil samples collected from PMTV- and Sss-free fields.

The p27(KIP1) and p57(KIP2) proteins belong to the CIP/KIP family of cyclin-dependent kinase inhibitors involved in the growth arrest and cellular senescence. High levels of p27(KIP1) unexpectedly have been detected in invasive malignant melanomas (MM), whereas the role of p57(KIP2) in melanocytic lesions is unknown. We therefore chose to study the expression of p27(KIP1) and p57(KIP2) in melanocytic neoplasms.The expression of p27(KIP1) and p57(KIP2) were examined by immunohistochemistry in 40 melanocytic neoplasms and by Western blot analysis in cultured human melanocytes.Expression of both nuclear p27(KIP1) and p57(KIP2) (> 10% of cells with nuclear labeling) was observed in most cases with non-proliferating melanocytes (8/10, benign nevi and 9/10 DN, dysplastic nevi), but in only a few cases containing proliferating melanocytes (3/11 RN, recurrent nevi and 2/9 MM, melanoma) (p < 0.002). In proliferating melanocytes, there was an inverse correlation of nuclear expression of p27(KIP1) and p57(KIP2) in both RN (p27(KIP1) = 3/11 RN and p57(KIP2) = 8/11 RN) and MM (p27(KIP1) = 7/9 MM and p57(KIP2) = 2/9 MM) (p < 0.05). Western blot analysis detected p57(KIP2) only in proliferating melanocytes. p27(KIP1) was detected in both proliferating and senescent melanocytes.The difference in expression patterns of p27(KIP1) and p57(KIP2) in proliferating and senescent melanocytes suggests the interplay between these proteins may play a functional role in melanocytic tumorigenesis.Curry JL, Richards HW, Huttenbach YT, Medrano EE, Reed JA. Different expression patterns of p27(KIP1) and p57(KIP2) proteins in benign and malignant melanocytic neoplasms and in cultured human melanocytes.J Cutan Pathol 2009; 36: 197-205. (C) 2008 Blackwell Munksgaard.

Immunohistochemical analysis has consistently shown that cyclin E is up-regulated in human malignant melanomas in vivo. Here we analyzed such expression in more detail and show that cyclin E is overexpressed and present in low molecular weight (LMW) isoforms in metastatic melanoma and in a subset of primary invasive melanoma tumor tissues, but not in benign nevi. Human metastatic melanoma cell lines, but not normal melanocytes, also expressed the LMW cyclin E forms. The biological significance of these findings was established by showing that overexpression of two LMW cyclin E forms named cyclin E truncated 1 [cyclinE(T1)] and cyclin E truncated 2 [cyclinE(T2)] in a low tumorigenic and non-metastatic primary cutaneous melanoma cell line generated angiogenic tumors with prominent perineural invasion compared with full-length cyclin E. In addition, cyclin E(T1)- and cyclin E(T2)-expressing melanoma cells displayed a dramatic increase in the incidence and number of metastases in an experimental lung metastasis assay. Together, these results indicate that the LMW cyclin E forms are functional and likely act as regulators of human melanoma tumor progression and invasion.

The population structure of the blast pathogen, Pyricularia grisea, was analyzed at two field sites used for evaluating blast resistance in rice. During 1992, 1,516 monoconidial isolates of the pathogen were collected from 38 rice cultivars and lines from the blast nursery of the international Rice Research Institute (IRRI-BN) and from the upland screening site at Cavinti. Each isolate was subjected to DNA fingerprinting and phenetic analysis using the probe MGR586. Nine lineages were detected at Cavinti during the wet season. Although the same four lineages were collected from the IRRI-BN during the dry and wet seasons, the relative abundance of lineages differed in the two collections. While the lineage diversity was greater at Cavinti than at the IRRI-BN in either season, the haplotypic diversities of the collections were similar. Generic differentiation and chi-square analysis indicated that populations of the fungus were differentiated geographically and temporally. The largest proportion of differentiation was attributable to host selection (G(ST) = 0.39). To assess how well field infection reflected compatibility, a subset of isolates was inoculated on their hosts of origin. Isolates were often unable to reinfect their hosts of origin, especially isolates belonging to the dominant pathogen lineage and when collected from young seedlings and those with low diseased leaf area. Our results provided insight into pathogen population structure, and provided useful information for rice improvement and management.