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Simple Summary: Ginseng replant disease is associated with root rot caused by the soil-borne fungus, Ilyonectria mors-panacis, which is believed to be due to the combination of the pathogen with unknown host-related factors found in soil after harvesting ginseng. One candidate for the host-related factor was described in a prior report where methanol extracts from previous ginseng soil increased root lesion sizes during Ilyonectria mors-panacis infections associated with suppression of ginseng disease defense gene expression. As treatment of ginseng with ginseng root extract did not have these effects, it was unclear what was the source of this bioactivity in soil. This study showed that a soil bacterium, Pseudomonas plecoglossicida, isolated from soil previously used for ginseng production, can convert ginseng root compounds in culture into compounds able to increase infections by Ilyonectria mors-panacis, demonstrating a possible way that a host factor of ginseng replant disease is produced by microbial conversion of root materials in previous ginseng soils. A prior report showed that soil previously planted with American ginseng (Panax quinquefolius) contained compound(s) which could reduce ginseng resistance to root infection by Ilyonectria mors-panacis, and this was not found in extracts from ginseng roots or soils not previously planted with ginseng. However, the origin of this ginseng-related factor in ginseng soils is unknown. An isolate of Pseudomonas plecoglossicida obtained from soil where P. quinquefolius had been harvested grew more in culture media when ginseng root extract was included, indicating the use of compounds in the extract as nutrients. Treatment with cell-free extracts from media containing ginseng root extracts where P. plecoglossicida had been cultured resulted in root lesions caused by I. mors-panacis being significantly larger than roots treated with fresh media containing root extract or with cell-free media inoculated with the same bacterial isolate without root extract. Levels of ginsenosides in the media decreased over time with incubation. Genome sequencing revealed that the bacterium had genes homologous to those reported for ginsenoside metabolism, which can release sugars for microbial growth. Thus, a ginseng soil bacterium, P. plecoglossicida, can create compound(s) suppressive to root rot resistance, similar to that found in soils previously planted with ginseng, indicating that the activity suppressing root rot resistance in soil previously planted with ginseng may be of microbial origin, utilizing compounds from ginseng roots. [ABSTRACT FROM AUTHOR]

Simple Summary: Metabolic changes in adult honey bee brains associated with the seasons and aging in honey bees (Apis mellifera) were assessed using nuclear magnetic resonance (NMR) spectroscopy. Brains were dissected from newly emerged, 14-day– old, and 28-day– old bees that were collected over the summer, as well as brood nest bees collected in the fall, winter, and spring. Changes in the brain metabolome indicated that worker bees undergo adaptations throughout their lives, with notable shifts occurring between newly emerged and older individuals. Furthermore, the seasons affected the honey bee brain metabolome, highlighting differences in metabolic responses to changes in the environment and resource availability. While previous studies have reported differences in the metabolome of whole bodies between summer and winter bees, or in the brains of forager bees infected with a virus, the present study has revealed the metabolome of the honey bee brain as it ages. Several potential markers were identified for assessing aging of the bee brain, such as the potential neurotransmitter β-alanine and neurotransmitter-precursors/intermediates, phenylalanine, tyrosine, tryptophan, and O-phosphocholine. Honey bees (Apis mellifera) provide a useful model for studying aging because of the differences in longevity between the relatively short-lived summer and long-lived winter bees, as well as bees lacking signs of cognitive senescence as they age. Bee brains were dissected from newly emerged, 14-day–, and 28-day– old bees in mid- and late summer, as well as brood nest bees in fall, winter, and spring, before, during, and after overwintering, respectively. Brains were examined with nuclear magnetic resonance (NMR) spectroscopy to analyze their metabolome. Nine variable importance in projection (VIP) variables were identified, primarily amino acids and choline derivatives. Differences in metabolite concentrations were found with different ages of summer bees, mostly between newly emerged and 14-day– old bees, such as a decrease in phenylalanine and an increase in β-alanine, but there were also changes in older adults, such as o-phosphocholine that declined in 28-day– old bees. Differences in brood nest bees were observed, including a decline in tryptophan and an increase in β-alanine. These may provide distinct metabolomic signatures with age and season. Such research holds promise for a better understanding of the complex interplays between bee physiology, development, and aging, which has implications for improving bee health and management. [ABSTRACT FROM AUTHOR]

Turcicum leaf blight (TLB) of maize is caused by Exserohilum turcicum. The TLB resistance is mainly associated with qualitative race‐specific resistance that is linked to several Ht genes namely Ht1, Ht2, Ht3, HtM, HtN, HtNB and HtP. However, quantitative TLB resistance also occurs, but its mechanisms are poorly understood. In this study, tolerance or insensitivity to chlorosis and necrosis of E. turcicum culture filtrate was associated with quantitative TLB resistance. A novel detached maize seedling assay was developed for E. turcicum culture filtrate using methanol‐treated modified Fries medium. Screening of E. turcicum isolates of races 2, 3, 23, 3 N, 23 N and 123 N against 61 maize inbred lines with diverse levels of resistance to TLB was conducted in the greenhouse by fungal inoculation and the detached seedling culture filtrate assay. Using an isolate of race 123 N, which can overcome all the qualitative resistance genes, a simple linear regression model (R2 = 0.68, p =.90) for the 61 inbred lines was established between disease severity from foliar inoculations and culture filtrate symptom rating of the detached seedling assay. Two maize lines CML474 and CML483 had relatively high culture filtrate symptom ratings but very low disease severity with foliar inoculation indicating that these sources of quantitative TLB resistance may be unrelated to tolerance to E. turcicum culture filtrates, whose effect on seedlings could be due to the toxin known as HT‐toxin or monocerin. [ABSTRACT FROM AUTHOR]

Commercial harvesting of American ginseng (Panax quinquefolius) results in root debris in the soil, but the rate of decay is unknown. In this study, post-harvest root debris decayed mostly over the fall and winter, with almost no ginseng debris remaining in the soil by late spring of the following year. However, a small number of intact pencil-shaped roots were able to survive after harvest and sprout the following spring without any evidence of root decay. Root rot lesions were observed, which included many associated with the root rot pathogen Ilyonectria mors-panacis, with disappearing root rot symptoms observed in the following spring. Ginsenosides in soil were highest just prior to harvest, declining until an increase the following spring. Soil bacterial and fungal populations changed over time after harvest with several peaks in bacterial populations mostly in the fall, but this was less clear for fungal populations, which were dominated by only a few taxa. Harvesting ginseng can leave considerable debris in the soil, impacting its chemistry and microbiota. Ginseng replant disease, where the second crop shows high levels of root rot due to I. mors-panacis infection compared to low levels in the first crop, could be related to the decay of post-harvest crop debris, but additional research is needed to demonstrate this. [ABSTRACT FROM AUTHOR]

A comparison of the virulence, saprophytic growth, and genomes of 12 isolates of Ilyonectria mors-panacis and 4 isolates of I. robusta from Canada pathogenic to Panax quinquefolius was made. There were no significant differences in the average lesion size on detached roots between isolates of the two Ilyonectria species or isolates that originated from infected roots in first- or second-crop ginseng soils. This did not support the hypotheses that I. mors-panacis is always more virulent than I. robusta or that there is selection for higher virulence during the first crop. However, the average growth rate on potato dextrose agar for I. robusta was significantly greater than that of I. mors-panacis, and the average total genome size of I. robusta isolates was significantly smaller with a significantly higher GC content. On dendrograms based on nucleotide sequences of all predicted exons of the genomes, I. robusta isolates were distinguishable from I. mors-panacis isolates, which were similar but could be separated into types 1 and 2. The difference between type 1 and type 2 I. mors-panacis was not related to geographical origin, virulence, growth rate, or mating type. However, the division was also observed for the total predicted secretome, most notably small secreted cysteine-rich proteins and secreted proteases, indicating that type 1 and 2 isolates of I. mors-panacis may interact differently with their environment. [ABSTRACT FROM AUTHOR]

Introduction: Natural weed cover and a legume cover crop were examined to determine if they could impact soil fungal diversity as an indicator of soil quality in banana production. Methods: Banana in Yunnan Province, China, was grown under three treatments: conventional tillage (bare soil), natural weed cover (primarily goosegrass (Eleusine indica (L.) Gaerth)), or a cover crop (Siratro (Macroptilium atropurpureum (DC.) Urb.)). Analysis of the soil fungal communities between 2017 and 2020 was done by Illumina Miseq high-throughput sequencing. Results: Most significant effects were in the intercropping area for the treatments, whereas it was rarely observed in the furrow planted with banana. Based on the Shannon and Simpson diversity indices, soil fungal diversity in the intercropping area significantly decreased following planting banana in 2017 with all three treatments. However, both the Shannon and Simpson diversity indices showed that there were significant increases in fungal soil diversity in 2019 and 2020 with natural weed cover or Siratro compared to bare soil. At the end of the experiment, significant increases in fungal genera with Siratro compared to bare soil were observed with Mortierella, Acremonium, Plectophaerella, Metarhizium and Acrocalymma, and significant decreases were observed with Fusicolla, Myrothecium, Exserohilum, Micropsalliota and Nigrospora. Siratro resulted in higher stability of the soil fungal microbiome by increasing the modularity and the proportion of negative co-occurrences compared to bare soil. For fungal guilds, Siratro significantly increased saprotrophs_symbiotrophs in 2019 and 2020 and significantly decreased pathogens_saprotrophs in 2020 compared to bare soil. Discussion: Using Siratro as a cover crop in the intercropping area of banana helped maintain soil fungal diversity, which would be beneficial for soil health with more symbiotrophs and less pathogens in the soil. However, further research is needed to determine the long-term impact of weed or Siratro cover crop on the fungal soil ecosystem and growth of banana. [ABSTRACT FROM AUTHOR]

Azoxystrobin, a quinone outside inhibitor fungicide, reduced tobacco target spot caused by Rhizoctonia solani by 62%, but also affected the composition and diversity of other microbes on the surface and interior of treated tobacco leaves. High-throughput sequencing showed that the dominant bacteria prior to azoxystrobin treatment were Methylobacterium on healthy leaves and Pseudomonas on diseased leaves, and the dominant fungi were Thanatephorous (teleomorph of Rhizoctonia) and Symmetrospora on healthy leaves and Thanatephorous on diseased leaves. Both bacterial and fungal diversity significantly increased 1 to 18 days post treatment (dpt) with azoxystrobin for healthy and diseased leaves. For bacteria on healthy leaves, the relative abundance of Pseudomonas, Sphingomonas, Unidentified-Rhizobiaceae and Massilia declined, while Methylobacterium and Aureimonas increased. On diseased leaves, the relative abundance of Sphingomonas and Unidentified-Rhizobiaceae declined, while Methylobacterium, Pseudomonas and Pantoea increased. For fungi on healthy leaves, the relative abundance of Thanatephorous declined, while Symmetrospora, Sampaiozyma, Plectosphaerella, Cladosporium and Cercospora increased. On diseased leaves, the relative abundance of Thanatephorous declined, while Symmetrospora, Sampaiozyma, Plectosphaerella, Cladosporium, Phoma, Pantospora and Fusarium, increased. Compared to healthy leaves, azoxystrobin treatment of diseased leaves resulted in greater reductions in Thanatephorous, Sphingomonas and Unidentified-Rhizobiaceae, a greater increase in Methylobacterium, and similar changes in Phoma, Fusarium, Plectosphaerella and Cladosporium. Azoxystrobin had a semi-selective effect altering the microbial diversity of the tobacco leaf microbiome, which could be due to factors, such as differences among bacterial and fungal species in sensitivity to quinone outside inhibitors, ability to use nutrients and niches as certain microbes are affected, and metabolic responses to azoxystrobin. [ABSTRACT FROM AUTHOR]