PhytoFrontiers™
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61
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1
(FIVE YEARS 1)

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2690-5442

Author(s):  
Shyam L. Kandel ◽  
Rubaiya Jesmin ◽  
Brian M. Mack ◽  
Rajtilak Majumdar ◽  
Matthew K. Gilbert ◽  
...  

Aspergillus flavus is an opportunistic pathogen of oilseed crops such as maize, peanut, cottonseed, and tree nuts and produces carcinogenic secondary metabolites known as aflatoxins during seed colonization. Aflatoxin contamination not only reduces the value of the produce but also is a health hazard to humans and animals. Previously, we observed inhibition of A. flavus aflatoxin biosynthesis upon exposure to the marine bacterium, Vibrio gazogenes (Vg). In this study, we used RNA sequencing to examine the transcriptional profiles of A. flavus treated with both live and heat-inactivated dead Vg and control samples. Fungal biomass, total accumulated aflatoxins, and expression profiles of genes constituting secondary metabolite biosynthetic gene clusters were determined at 24, 30, and 40 h after treatment. Statistically significant reductions in total aflatoxins were detected in Vg-treated samples as compared to control samples at 40 h. But no statistical difference in fungal biomass was observed upon these treatments. The Vg treatments were most effective on aflatoxin biosynthesis as was reflected in significant downregulation of majority of the genes in the aflatoxin gene cluster including the aflatoxin pathway regulator gene, aflR. Along with aflatoxin genes, we also observed significant downregulation in some other secondary metabolite gene clusters including cyclopiazonic acid and aflavarin, suggesting that the treatment may inhibit other secondary metabolites as well. Finally, a weighted gene correlation network analysis identified an upregulation of ten genes that were most strongly associated with Vg-dependent aflatoxin inhibition and provide a novel start-point in understanding the mechanisms that result in this phenomenon.


Author(s):  
Abubakar Sadik Mustafa ◽  
Benison Tugume ◽  
Jamilu Ssenku ◽  
Paul Ssemanda ◽  
Shahasi Athman ◽  
...  

Xanthomonas campestris pv. musacearum (Xcm) bacteria cause banana Xanthomonas wilt (BXW), the most destructive disease of bananas in East and Central Africa. During early stages of infection in susceptible banana cultivars, incomplete systemic movement of Xcm limits bacterial colonization in the upper organs. Mechanistic basis of this delayed movement is unknown. We hypothesized that Xcm infection triggers basal pattern triggered immune (PTI) responses whose spatial and temporal variability along banana’s anatomical structure accounts for initially limiting Xcm in upper organs. Hence, we examined PTI responses such as callose deposition and hydrogen peroxide (H2O2) production in different organs in response to Xcm infection in BXW susceptible Kayinja and Mbwazirume banana cultivars and wild resistant progenitor Musa balbisiana. Xcm-induced callose increased and peaked at 14 days post inoculation (dpi) and 28dpi as assessed by fluorescence microscopy and enzyme-linked immunosorbent assays, respectively. The levels of Xcm-induced H2O2 and callose were highest in the pseudostems and corms, respectively, and were independent of host susceptibility or resistance to BXW. H2O2 production showed a biphasic transient pattern with an initial increase at 1-hour post Xcm-inoculation (hpi), followed by a decline 3-6hpi and then a second increase by 12hpi. Our findings point to organ-specific responses to Xcm infection in bananas. The corm which doubles as a subterranean parenating organ and interface between mother plants and lateral shoots, was the most responsive organ in callose production while the pseudostem was the most responsive organ in H2O2 production, suggesting the significance of these organs in banana response to BXW.


Author(s):  
Grazieli Araldi Da Silva ◽  
Gang Han ◽  
Yuba Raj Kandel ◽  
Daren S. Mueller ◽  
Matthew Helmers ◽  
...  

Cover crops improve soil and water quality in annual cropping systems, but knowledge of their impact on soybean (Glycine max L.) seedling and root diseases is limited. The effects of winter rye cover crops (Secale cereale L.) on soybean population, biomass, root morphology, seedling and root diseases, pathogen incidence, canopy reflectance, and yield were assessed over two years in Iowa and Missouri, USA. Plots without a rye cover crop were compared to plots with early-kill rye and late-kill rye cover crops, which were terminated 34 to 49 days or 5 to 17 days before soybean planting, respectively. Soybean shoot dry weight, root rot severity, and incidence of Fusarium spp. and Pythium spp. on roots were not influenced by the treatments. Soybean grain yield and plant population were reduced in the presence of rye in two site-years, increased in one site-year, and not changed in the remaining site-years. Soybean canopy reflectance was measured at 810 nm and measurements were first made at 70 to 80 days after planting (DAP). At least five measurements were obtained at 7- to 15- day intervals, ending at 120 to 125 DAP. Measurements at approximately 120 to 125 DAP differed by treatments but were not consistently associated with the presence or absence of a rye cover crop. Our field studies suggest that Iowa and Missouri soybean farmers can use winter rye as a cover crop in soybean fields with low seedling disease pressure without increasing the risk of seedling and root diseases or suppressing yield.


2021 ◽  
Vol 1 (4) ◽  
pp. 250-367

PhytoFrontiers™ Vol. 1 No. 4


Author(s):  
MALCOLM HOBBS ◽  
Selena Vengco ◽  
Michelle Moyer ◽  
Stephanie Bolton ◽  
Larry Bettiga ◽  
...  

Grapevine leafroll (GLD) and red blotch (RBD) diseases threaten the sustainability of the USA wine grape industry. To understand factors influencing the adoption of disease management practices, we surveyed wine grape industry professionals in California, Oregon, and Washington (n=154). Economic factors were the fundamental cost of implementing management practices and the ability to sell product from diseased vines (salability). Respondents with reduced salability were more likely to adopt virus testing, replace infected vines, and view these practices as economically favorable. Salability was a strong driver for adoption among Californian respondents, but lesser so in Washington where wineries appeared more willing to accept infected product. Respondents who had acquired technical knowledge of disease ecology were more likely to adopt management practices and to perceive them as economical. Conversely, when there was a lack of knowledge of GLD ecology, notably that mealybugs transmit the pathogen, , adoption was reduced and practices were considered less economical,. Factors affecting adoption were broadly generalizable across diseases. However, knowledge of GLD ecology was more strongly associated with adoption, likely reflecting the remaining knowledge gaps in RBD related to vector ecology and field spread. An emphasis on grower knowledge acquisition and the development of economical disease management practices can improve adoption of best management practices for viral diseases of grapevine.


Author(s):  
Joan Miquel Bernabé-Orts ◽  
Yolanda Hernando ◽  
Miguel A. Aranda

Implementing effective monitoring strategies is fundamental to protect crops from pathogens and to ensure the food supply as the world population continues to grow. This is especially important for emergent plant pathogens such as tomato brown rugose fruit virus (ToBRFV), which overcomes the genetic resistance resources used in tomato breeding against tobamoviruses and has become pandemic in less than a decade. Here we report the development of a CRISPR/Cas12a-based test to detect ToBRFV in the laboratory and potentially in a field setting. Using different tobamoviruses to assess specificity, our test showed a clear positive signal for ToBRFV-infected samples, while no cross-reactivity was observed for closely related viruses. Next, we compared the limit of detection of our CRISPR-based test with a reference real-time quantitative PCR test widely used, revealing similar sensitivities for both tests. Finally, to reduce complexity and achieve field-applicability, we used a fast nucleic acid purification step and compared its results side-to-side with those of a commonly used column-mediated protocol. The rapid protocol saved time and resources but at the expense of sensitivity. However, it still may be useful to confirm ToBRFV detection in samples with incipient symptoms of infection. Although there is room for improvement, to our knowledge this is the first field-compatible CRISPR-based test to detect ToBRFV which combines isothermal amplification with a simplified nucleic acid extraction protocol.


Author(s):  
Christopher Wallis ◽  
Jianchi Chen ◽  
Adalberto A. Perez de Leon

Trichoderma spp. are commonly used as bioremediation agents, biological controls, and for making biofuels. Herein, a Trichoderma harzianum strain PAR3 was isolated from grapevine roots in central California, USA. As part of a larger whole genome sequencing effort, the mitochondrial genome (mitogenome) sequence was obtained for the PAR3 strain. The mitogenome is 27,631 bp containing genes of 14 core mitochondrial proteins, 25 tRNA, and two rRNAs and a GC% content of 27.55%. BLAST search using the PAR3 mitogenome as query against GenBank sequence database showed mitogenome MUT3171 (29,791 bp) of Trichoderma lixii was the most similar (Query Coverage = 99%; Percentage Identity=100.00%) with two major deletions, 1,339 bp and 821 bp. The PAR3 mitogenome sequence will provide a useful reference for comparing different Trichoderma strains from US and around the world.


Author(s):  
Brendan Riely ◽  
Mohamed Taieb Nouri ◽  
Kashif Riaz ◽  
Muhammad Rizwan Tufail ◽  
Yunpeng Gai ◽  
...  

Pistachio Bushy Top Syndrome (PBTS) is a serious problem for pistachio growers in the western U.S. but the cause of this disorder remains controversial. Recently, it was proposed that the Rhodococcus species, R. fascians and R. corynebacterioides caused PBTS outbreaks in 2011 and 2015. To investigate the association of Rhodococcus spp with PBTS in California’s pistachio growing region, Rhodococcus-like isolates were collected from diverse hosts and environments, including pistachio nurseries and orchards. Whole genome sequence analysis of 231 isolates revealed their evolutionary relationships and identified six Rhodococcus species. Combined with data on geography and host of origin, the data reveal that Rhodococcus generally, and R. fascians specifically, is ubiquitous in nature, frequently occurring in both symptomatic and asymptomatic pistachio trees and on other woody and native species. Core gene and SNP-based phylogenies, and pan-genome analyses differentiate R. fascians into distinct genotypes. Although we found examples of common genotypes shared between nurseries and orchards, the observed patterns are most consistent with an environmental source of strains and do not support a scenario where individual nurseries are point sources of Rhodococcus. Moreover, none of the collected strains harbored known virulence genes, calling into question the role of these common, environmental bacteria in causing PBTS.


Author(s):  
Hongmiao Shen ◽  
Xiaomeng Shi ◽  
Longxian Ran

A previously unknown association between Plasmopara viticola, the causal pathogen of grape downy mildew, and the mycoparasite strain F2 was described in this paper. F2 could be consistently isolated from the mildew of diseased spots on grape leaves of Kyoho (Vitis labrusca × V. vinifera cv. Kyoho) infected with P. viticola, but neither from the surfaces of healthy grape leaves nor within lesions of other diseases. It could be observed that strain F2 was capable of coiling around sporangiophores and sporangia of P. viticola under microscope, causing hyphae deformation, decreasing the pathogen growth, and reducing the number of sporangia. This fungal strain was identified as Simplicillium lanosoniveum on the basis of morphological characterizations and 28S rDNA sequencing. To our knowledge, this is the first report of S. lanosoniveum with hyperparasitic characteristics on P. viticola, and the hyperparasite has potential application in the control of grape downy mildew.


Author(s):  
Juanita Gil ◽  
Laura Ortega ◽  
J Alejandro Rojas ◽  
Clemencia M Rojas

Burkholderia glumae causes Bacterial Panicle Blight of rice. Here, we report the genomic sequence of B. glumae strain UAPB13 isolated from fields in Arkansas. The assembled genome consists of 123 scaffolds totaling 6,504,483 bp representing two chromosomes and two plasmids. The genomic complexity of B. glumae warrants the sequencing of additional strains. This additional genomic sequence will enable us to further understand this pathogen and the disease it causes.


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