The Detection and Characterization of QoI-Resistant Didymella rabiei Causing Ascochyta Blight of Chickpea in Montana

Abstract

Ascochyta blight (AB) of pulse crops (chickpea, field pea, and lentils) causes yield loss in Montana, where 1.2 million acres was planted to pulses in 2016. Pyraclostrobin and azoxystrobin, quinone outside inhibitor (QoI) fungicides, have been the choice of farmers for the management of AB in pulses. However, a G143A mutation in the cytochrome b gene has been reported to confer resistance to QoI fungicides. A total of 990 isolates of AB-causing fungi were isolated and screened for QoI resistance. Out of these, 10% were isolated from chickpea, 81% were isolated from field peas, and 9% isolated from lentil. These were from a survey of grower’s fields and seed lots (chickpea = 17, field pea = 131, and lentil = 21) from 23 counties in Montana sent to the Regional Pulse Crop Diagnostic Laboratory, Bozeman, MT, United States for testing. Fungicide-resistant Didymella rabiei isolates were found in one chickpea seed lot each sent from Daniels, McCone and Valley Counties, MT, from seed produced in 2015 and 2016. Multiple alignment analysis of amino acid sequences showed a missense mutation that replaced the codon for amino acid 143 from GGT to GCT, introducing an amino acid change from glycine to alanine (G143A), which is reported to be associated with QoI resistance. Under greenhouse conditions, disease severity was significantly higher on pyraclostrobin-treated chickpea plants inoculated with QoI-resistant isolates of D. rabiei than sensitive isolates (p-value = 0.001). This indicates that where resistant isolates are located, fungicide failures may be observed in the field. D. rabiei-specific polymerase chain reaction primer sets and hydrolysis probes were developed to efficiently discriminate QoI- sensitive and - resistant isolates.

Detection and Characterization of QoI-Resistant Phytophthora capsici Causing Pepper Phytophthora Blight in China

“…A previous study revealed that the G143A and F129L substitutions do not affect the function of the bc1 complex, though G137R seriously impacts the enzymatic activity of the complex and, thus, inhibits cellular respiration (Gisi et al 2002). Additionally, fungi containing G137R can, to some extent, be controlled by QoI fungicides, although at lower levels than wild-type sensitive isolates (Owati et al 2017). These problems require further study.…”

“…applied, resistance will likely be preserved in the population after establishment (Owati et al 2017).…”

“…In the current study, we found that all the P. capsici strains also exhibited decreased sensitivity to pyraclostrobin and famoxadone (Table 2). To avoid the rapid development of field resistance, QoI should be applied in combination with fungicides with different modes of action (Owati et al 2017) and sprayed preventatively according to the recommended labeled rate rather than after disease has developed (Kitchen et al 2016). In addition, we recommend that producers withdraw the use of QoI in regions where resistant strains have already occurred.…”

Combining transcriptome analysis and GWAS for identification and validation of marker genes in the Physalis peruviana-Fusarium oxysporum pathosystem

“…Approaches such as RNA sequencing (RNA-Seq) and genome wide association studies (GWAS) have allowed the profiling of global gene expression patterns and the mapping of simple or complex traits, respectively, in both model and non-model plants. These approaches have been useful resources for the understanding of how plants respond to biotic or abiotic stimuli through the discovery of candidate genes involved in different biological processes ( Iquebal et al, 2019 ; Sicilia et al, 2019 ; Safavi-Rizi, Herde & Stöhr, 2020 ), including those involved in plant-microbe interactions ( Bartoli & Roux, 2017 ).…”

Biocontrol of Ascochyta blight by Azospirillum sp. depending on the degree of resistance of chickpea genotypes

“…Several applications of foliar fungicides are often required in order to control the seed‐borne A. rabiei . The polycyclic nature of the disease, the pathogen airborne spores and sexual reproduction option for most species, allowing rapid mutation and inheritance by offspring that were resulted in a rapid and widespread insensitivity to fungicides (Owati, Agindotan, Pasche, & Burrows, ; Wise, Bradley, Pasche, & Gudmestad, ).…”