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Author(s):  
Tejpal Bajaya ◽  
R.P. Ghasolia ◽  
Mamta Bajya ◽  
Manisha Shivran

Background: Collar rot of groundnut (Arachis hypogaea L.) caused by Aspergillus niger is a significant constraint in groundnut cultivation and responsible for huge economic losses in India including Rajasthan. Methods: By surveying of eight major groundnut growing districts of Rajasthan, India, one representative Aspergillus niger isolate from each district was established (ANBK-01= Bikaner, ANCH-02= Churu, ANDA-03= Dausa, ANJP-04= Jaipur, ANJL-05= Jalore, ANJD-06= Jodhpur, ANNG-07= Nagaur and ANSK-08= Sikar) for studying variability in the pathogen as well as to know the response of groundnut varieties to the highly virulent isolate. The colony and spore characteristics were observed for cultural and morphological variability. For resistance response to the disease, ten varieties (M-13, RG-633-9, RG-382, Girnar-2, RG-604, RG-578, Gajraj 10, RG-510, RG-632-1 and RG-644) were evaluated in the field for two consecutive years against a highly virulent Aspergillus niger (ANJP-04) isolate. Result: Our investigations cleared that all the isolates were showed cultural and morphological variability such as shape, colour and size of colony and size of conidia, conidiophores and columella. Isolate (ANJP-04) collected from Khejroli village of Chomu tehsil in Jaipur district showed maximum mycelial growth, conidia diameter, length and diameter of conidiophores and length and diameter of columella, early sporulation and found most virulent as it produced higher disease incidence (54.43%). Ten released varieties of groundnut in the field conditions, revealed that none of the variety was found completely free from the disease whereas RG-644, M-13 and RG-510 were found resistant while RG-604, Girnar-2, Gajraj-10 and RG-632-1 were found moderately resistant and rest were found susceptible to highly susceptible to the disease. Conclusively, it can be finalized that famers may cultivate these resistant varieties in areas where collar rot is a severe constraint. The conclusion of this study can also be utilized to screen varieties/genotypes of groundnut against highly virulent isolate for sustainability of breeding material to the disease effectively.


Plants ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2123
Author(s):  
Wen Ze Go ◽  
Kit Ling Chin ◽  
Paik San H’ng ◽  
Mui Yun Wong ◽  
Chuah Abdullah Luqman ◽  
...  

Latex production from Hevea brasiliensis rubber tree is the second most important commodity in Malaysia, but this industry is threatened by the white root rot disease (WRD) caused by Rigidoporus microporus that leads to considerable latex yield loss and tree death. This study aimed to characterize and compare the virulence of five R. microporus isolates obtained from infected rubber trees located at different states in Malaysia. These isolates were subjected to morphological and molecular characterization for species confirmation and pathogenicity test for the determination of virulence level. BLAST search showed that the ITS sequences of all the pathogen isolates were 99% identical to R. microporus isolate SEG (accession number: MG199553) from Malaysia. The pathogenicity test of R. microporus isolates conducted in a nursery with 24 seedlings per isolate showed that isolate RL21 from Sarawak has developed the most severe above- and below-ground symptoms of WRD on the rubber clone RRIM600 as host. Six months after being infected with R. microporus, RL21 was evaluated with the highest average of disease severity index of 80.52% for above- and below-ground symptoms, followed by RL22 (68.65%), RL20 (66.04%), RL26 (54.38%), and RL25 (43.13%). The in vitro growth condition tests showed that isolate RL21 of R. microporus has optimum growth at 25–30 °C, with the preference of weakly acidic to neutral environments (pH 6–7). This study revealed that different virulence levels are possessed among different R. microporus isolates even though they were isolated from the same host species under the same climate region. Taken together, field evaluation through visual observation and laboratory assays have led to screening of the most virulent isolate. Determination of the most virulent isolate in the present study is vital and shall be taken into consideration for the selection of suitable pathogen isolate in the development of more effective control measures in combating tenacious R. microporus.


Author(s):  
K Bramareswara Rao ◽  
SR Krishna Motukuri ◽  
K Arun Kumar ◽  
CHVN Praveen Babu ◽  
Vaibhav Pathak

Pearl Millet leaf Blast caused by Pyricularia grisea [teleomorph: Magnaporthe grisea], is spreading at an alarming rate in the major Pearl millet growing geographies of India effecting grain yield and green fodder yield. Blast isolates collected from Jaipur, Alwar and Toopran regions of India and virulence study conducted to identify the most virulent isolate among the three isolates. Artificial screening for Blast conducted on a raised bed method utilising uniform Blast Nursery (UBN) method. Eleven Pearl Millet genotypes (ICMB01333, ICMB03444, ICMB03555, ICMB06111, ICMB95444, ICMB11666, ICMB14333, ICMB14666, ICMB97111, ICMR12888 and ICMR06444) were screened with three blast isolates utilising artificial screening method. Among the eleven genotypes, ten genotypes were showing susceptible to Jaipur isolate indicating that the Jaipur isolate having highest virulence among the three isolates. To identify Blast resistant donors for Jaipur isolate, a set of 93 genotypes containing of 45 maintainer lines and 48 restorer lines were screened under both UBN and field conditions (Jaipur, Rajasthan). Among all the lines evaluated, five lines are showing resistant reaction for Jaipur isolate with disease score less than 1.9. ICMR06444 from restorer background and IC414K14B5, IC594K16B5, RBB037 and IC6912K18B from maintainer background are identified as resistant lines. Identified lines can be utilised in pearl millet hybrid breeding programme.


Author(s):  
Yohan Ricci Zonta ◽  
Ana Laura Ortega Dezen ◽  
Amanda Manoel Della Coletta ◽  
Kaio Shu Tsyr Yu ◽  
Larissa Carvalho ◽  
...  

Paracoccidioidomycosis is a systemic fungal disease, considered endemic in Latin America. Its etiological agents, fungi of the Paracoccidioides complex, have restricted geographic habitat, conidia as infecting form, and thermo-dimorphic characteristics. Polymorphonuclear neutrophils (PMNs) are responsible for an important defense response against fungus, releasing Neutrophil Extracellular Traps (NETs), which can wrap and destroy the yeasts. However, it has been described that some pathogens are able to evade from these DNA structures by releasing DNase as an escape mechanism. As different NETs patterns have been identified in PMNs cultures challenged with different isolates of Paracoccidioides brasiliensis, the general objective of this study was to identify if different patterns of NETs released by human PMNs challenged with Pb18 (virulent) and Pb265 (avirulent) isolates would be correlated with fungal ability to produce a DNase-like protein. To this end, PMNs from healthy subjects were isolated and challenged in vitro with both fungal isolates. The production, release, and conformation of NETs in response to the fungi were evaluated by Confocal Microscopy, Scanning Microscopy, and NETs Quantification. The identification of fungal DNase production was assessed by DNase TEST Agar, and the relative gene expression for hypothetical proteins was investigated by RT-qPCR, whose genes had been identified in the fungal genome in the GenBank (PADG_11161 and PADG_08285). It was possible to verify the NETs release by PMNs, showing different NETs formation when in contact with different isolates of the fungus. The Pb18 isolate induced the release of looser, larger, and more looking like degraded NETs compared to the Pb265 isolate, which induced the release of denser and more compact NETs. DNase TEST Agar identified the production of a DNase-like protein, showing that only Pb18 showed the capacity to degrade DNA in these plates. Besides that, we were able to identify that both PADG_08528 and PADG_11161 genes were more expressed during interaction with neutrophil by the virulent isolate, being PADG_08528 highly expressed in these cultures, demonstrating that this gene could have a greater contribution to the production of the protein. Thus, we identified that the virulent isolate is inducing more scattered and loose NETs, probably by releasing a DNase-like protein. This factor could be an important escape mechanism used by the fungus to escape the NETs action.


2020 ◽  
Author(s):  
Gazala Ameen ◽  
Shyam Solanki ◽  
Thomas Drader ◽  
Lauren Sager-Bittara ◽  
Brian Steffenson ◽  
...  

ABSTRACTPlant biotrophic pathogen disease resistances rely on immunity receptor-mediated programmed cell death (PCD) responses, but specialized necrotrophic/hemi-biotrophic pathogens hijack these mechanisms to colonize the resulting dead tissue in their necrotrophic phase. Thus, immunity receptors can become necrotrophic pathogen dominant susceptibility targets but resistance mechanisms that resist necrotroph manipulation are recessive resistance genes. The barley rcs5 QTL imparts recessive resistance against the disease spot blotch caused by the hemi-biotrophic fungal pathogen Bipolaris sorokiniana. The rcs5 genetic interval was delimited to ~0.23 cM, representing an ~234 kb genomic region containing four wall-associated kinase (WAK) genes, designated HvWak2, Sbs1, Sbs2 (susceptibility to Bipolaris sorokiniana1&2), and HvWak5. Post-transcriptional gene silencing of Sbs1&2 in susceptible barley cultivars resulted in resistance showing dominant susceptibility function. Allele analysis of Sbs1&2 from resistant and susceptible barley cultivars identified sequence polymorphisms associated with phenotypes in their primary coding sequence and promoter regions, suggesting differential transcriptional regulation may contribute to susceptibility. Transcript analysis of Sbs1&2 showed nearly undetectable expression in resistant and susceptible cultivars prior to pathogen challenge; however, upregulation of both genes occurred specifically in susceptible cultivars post-inoculation with a virulent isolate. Apoplastic wash fluids collected from barley infected with a virulent isolate induced Sbs1, suggesting regulation by an apoplastic-secreted effector. Thus, Sbs1&2 function as B. sorokiniana susceptibility targets and non-functional alleles or alleles that resist induction by the pathogen mediate rcs5-recessive resistance. The sbs1&2 alleles underlying the rcs5 QTL that the pathogen is unable to manipulate are the first resistance genes identified against spot blotch.SIGNIFICANCE STATEMENTThe rcs5 locus in barley confers a high level of seedling resistance and a moderate level of adult plant resistance to spot blotch. It is part of a complex that has provided durable spot blotch resistance in many North American barley cultivars (cv) for more than 50 years. Genetic characterization and positional cloning of rcs5 identified the dominant susceptibility genes, Sbs1 and Sbs2 (susceptibility to Bipolaris sorokiniana 1 and 2) as wall-associated kinases. These genes are hijacked by the hemibiotrophic pathogen in its necrotrophic phase to induce programmed cell death, facilitating disease development. We report the first spot blotch resistance/susceptibility genes cloned that function via alleles that cannot be specifically induced and hijacked by virulent isolates of the pathogen.


PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8840 ◽  
Author(s):  
Fu-Hsiang Hou ◽  
Wei-Cheng Lee ◽  
Jiunn-Wang Liao ◽  
Maw-Sheng Chien ◽  
Chih-Jung Kuo ◽  
...  

Porcine reproductive and respiratory syndrome (PRRS) is one of the most common diseases in the global swine industry. PRRSV is characterized by rapid mutation rates and extensive genetic divergences. It is divided into two genotypes, which are composed of several distinct sub-lineages. The purpose of the present study was to evaluate the cross-protective efficacy of Fostera PRRS MLV, an attenuated lineage 8 strain, against the heterologous challenge of a lineage 3 isolate. Eighteen pigs were randomly divided into mock, MLV and unvaccinated (UnV) groups. The pigs in the MLV group were administered Fostera PRRS vaccine at 3 weeks of age and both the MLV and UnV groups were inoculated with a virulent PRRSV isolate at 7 weeks. Clinically, the MLV group showed a shorter duration and a lower magnitude of respiratory distress than the UnV group. The average days of fever in the MLV group was 3.0 ± 0.5, which was significantly lower than the 6.2 ± 0.5 days of the UnV group (P < 0.001). The average daily weight gains of the mock, MLV and UnV groups were 781 ± 31, 550 ± 44 and 405 ± 26 g/day, respectively, during the post-challenge phase. The pathological examinations revealed that the severity of interstitial pneumonia in the MLV group was milder compared to the UnV group. Furthermore, PRRSV viremia titers in the MLV pigs were consistently lower (101−101.5 genomic copies) than those of the UnV pigs from 4 to 14 DPC. In conclusion, vaccination with Fostera PRRS MLV confers partial cross-protection against heterologous challenge of a virulent lineage 3 PRRSV isolate.


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