Biology subjects

Bandara, A. Y.

Publications and source records attributed to Bandara, A. Y..

5 recordsLinked to original sources

bioRxiv2019

The necrotrophic fungus Macrophomina phaseolina induces oxidative stress-associated genes and related biochemical responses in charcoal rot susceptible sorghum genotypes

Macrophomina phaseolina (MP) is a necrotrophic fungus that causes charcoal rot disease in sorghum [Sorghum bicolor (L.) Moench]. The host resistance and susceptibility mechanisms for this disease are poorly understood. Here, the transcriptional and biochemical aspects of the oxidative stress and antioxidant system of charcoal rot resistant and susceptible sorghum genotypes in response to MP inoculation were investigated. RNA sequencing revealed 96 differentially expressed genes between resistant (SC599) and susceptible (Tx7000) genotypes that are related to the host oxidative stress and antioxidant system. Follow-up functional experiments demonstrated MPs ability to significantly increase reactive oxygen (ROS) and nitrogen species (RNS) content in the susceptible genotypes. This was confirmed by increased malondialdehyde content, an indicator of ROS/RNS-mediated lipid peroxidation. The presence of nitric oxide (NO) in stalk tissues of susceptible genotypes was confirmed using a NO-specific fluorescent probe (DAF-FM DA) and visualized by confocal microscopy. Inoculation significantly increased peroxidase activity in susceptible genotypes while catalase activity was significantly higher in MP-inoculated resistant genotypes. MP inoculation significantly reduced superoxide dismutase activity in all genotypes. These findings suggested MPs ability to promote a host-derived oxidative stress response in susceptible sorghum genotypes, which contributes to induced cell death-associated disease susceptibility to this necrotrophic phytopathogen.

biochemistry↗

bioRxiv2019

Dynamics of host glutathione and glutathione related enzymes in Macrophomina phaseolina-sorghum bicolor interaction

Glutathione and its related enzymes play an integral role in cellular detoxification processes and redox buffering. A genome wide transcriptome profiling was conducted through RNA sequencing to investigate the dynamics of glutathione and related enzymes in sorghum bicolor (L.) Moench in response to Macrophomina phaseolina (MP) infection. Compared to mock inoculated control treatment, MP significantly upregulated the glutathione synthetase, glutamate cysteine ligase (involved in glutathione biosynthesis), glutathione s-transferase (GST), glutathione peroxidase (GPX), and glutathione reductase (GR) genes in a charcoal rot susceptible sorghum genotype (Tx7000), but not in a resistant genotype (SC599) at 7 days post- inoculation. The net log2 fold up-regulation of the aforesaid genes in MP-inoculated Tx7000 was 1.9, 0.9, 120.0, 9.0, and 4.5, respectively. To confirm the gene expression data, cell extracts were acquired from MP- and mock-inoculated resistant (SC599, SC35) and susceptible (Tx7000, BTx3042) sorghum genotypes and their reduced (GSH), oxidized (GSSG) glutathione, GST, GPX, and GR activities were measured using standard protocols. A significantly reduced GSH/GSSG ratio was observed in Tx7000 and BTx3042 indicating the strong oxidative stress experienced by charcoal rot susceptible genotypes under MP infection. MP significantly increased the GST, GPX, and GR activities of Tx7000 and BTx3042. Although augmented GR activity contributes to cellular GSH restoration, the enhanced GST activity leads to diminishing GSH pools through vacuolar sequestration of GSH-S-conjugates. This eases the oxidative stress confronted by susceptible genotypes under MP infection and in turn contributes to reduced charcoal rot susceptibility. The importance of GSH in controlling the MP infection associated oxidative stress was further supported by the significantly reduced disease severity observed in Tx7000 and BTx3042 upon exogenous GSH application.

biochemistry↗

bioRxiv2019

Host lipid alterations after Macrophomina phaseolina infection contribute to charcoal rot disease susceptibility in grain sorghum: Evidence from transcriptomic and lipidomic data.

O_LILipids are involved in central metabolic processes and confer basic configuration to cellular and subcellular membranes. Lipids also play a role in determining the outcome of plant-pathogen interactions. Lipid based links that delineate either host resistance or susceptibility against necrotrophic microorganisms are poorly investigated and described. Macrophomina phaseolina (MP) is an important necrotrophic fungus which causes diseases in over 500 plant species including charcoal rot in sorghum. C_LIO_LIWe used RNA sequencing and automated direct infusion electrospray ionization-triple quadrupole mass spectrometry (ESI-MS/MS) to quantitatively profile the transcriptomes and lipidomes of a known charcoal rot resistant (SC599) and susceptible (Tx7000) sorghum genotype in response to MP inoculation. C_LIO_LIWe found that MP is capable of significantly decreasing the phosphatidylserine, phytosterol, and ox-lipid contents in the susceptible genotype while significantly increasing its stigmasterol:sitosterol and monogalactosyldiacylglycerol: digalactosyldiacylglycerol ratios. None of the above was significantly affected in the resistant genotype, except for the significantly increased ox-lipid content. C_LIO_LIOur transcriptome and functional lipidome findings suggested the lethal impacts of MP inoculation on plastid- and cell- membrane integrity and the lipid based signaling capacity of the charcoal rot susceptible sorghum genotype, Tx7000. Findings also suggested the strong oxidative stress experienced by Tx7000 under MP inoculation and shed light on the potential lipid classes involved in induced charcoal rot disease susceptibility. C_LI

biochemistry↗

bioRxiv2019

Modeling the relationship between estimated foliar fungicide use and soybean yield losses due to foliar fungal diseases in the United States

Fungicide use in the United States to manage soybean diseases has increased in recent years. The ability of fungicides to reduce disease-associated yield losses varies greatly depending on multiple factors. Nonetheless, historical data are useful to understand the broad sense and long-term trends related to fungicide use practices. In the current study, the relationship between estimated soybean yield losses due to selected foliar diseases and foliar fungicide use was investigated using annual data from 28 soybean growing states over the period of 2005 to 2015. At a national scale, a significant quadratic relationship was observed between total estimated yield losses and total fungicide use (R2 = 0.123, P < 0.0001) where yield losses initially increased, reached a plateau, and subsequently decreased with increasing fungicide use. The positive phase of the quadratic curve could be associated with insufficient amount of fungicides being used to manage targeted diseases, application of more-than-recommended prophylactic fungicides under no/low disease pressure, application of curative fungicides after economic injury level, and reduced fungicide efficacy due to a variety of factors such as unfavorable environmental conditions and resistance of targeted pathogen populations to the specific active ingredient applied. Interestingly, a significant quadratic relationship was also observed between total soybean production and total foliar fungicide use (R2= 0.36, P < 0.0001). The positive phase of the quadratic curve may suggest that factors like plant physiological changes, including increased chlorophyll content, photosynthetic rates, water use efficiency, and delayed senescence that have been widely reported to occur after application of certain foliar fungicides could have potentially contributed to enhanced yield. Therefore, the current study provides evidence of the potential usefulness of foliar fungicide applications to mitigate soybean yield losses associated with foliar diseases and their potential to positively impact soybean production/yield at national and regional scales although discrepancies to the general trends observed at national and regional scales do prevail at the local (state) level.

pathology↗

bioRxiv2019

Dissecting the economic impact of soybean diseases in the United States over two decades

Soybean (Glycine max L. Merrill) is a key commodity for United States agriculture. Here we analyze the economic impacts of 23 common soybean diseases in 28 soybean-producing states in the U.S., from 1996 to 2016. From 1996 to 2016, the total estimated economic loss due to soybean diseases in the U.S. was $81.39 billion, with $68.98 billion and $12.41 billion accounting for the northern and southern U.S. losses, respectively. Across states and years, soybean cyst nematode, charcoal rot, and seedling diseases were the most economically damaging pathogens/diseases while soybean rust, bacterial blight, and southern blight were the least economically damaging. Significantly positive linear correlation of mean soybean yield loss with the mean state-wide soybean production (MT) and mean soybean yield (kg ha-1) indicated that high production zones are more vulnerable to soybean diseases-associated yield losses. Our findings provide useful insights into how research, policy, and educational efforts should be prioritized in soybean disease management.

epidemiology↗