Resistant Cultivars Research Articles

An Evaluation of Bacterial Wilt (Ralstonia solanacearum) Resistance in a Set of Tomato Germplasm from the United States Department of Agriculture

Bacterial wilt (BW), caused by Ralstonia solanacearum, is one of the devastating diseases in tomatoes (Solanum lycopersicum L.). The use of resistant cultivars and breeding for genetic resistance is the most effective, economical, and environmentally friendly management strategy for this disease. It is necessary to screen diverse germplasm and cultivated genotypes to identify resistant resources and to develop resistant cultivars in tomatoes to combat the changing pathogen isolates. This study evaluated 40 United States Department of Agriculture (USDA) tomato accessions for their BW resistance to the R. solanacearum isolate P822 under greenhouse conditions. The tomato plants were inoculated and visually assessed to observe their symptoms, and the disease severity was scored on a scale of 0 to 4 (0 = no leaf wilted, 1 = 25% of leaves wilted, 2 = 50% leaves wilted, 3 = 75% of leaves wilted, and 4 = 100% leaves wilted). Five accessions (PI 645370, PI 647306, PI 600993, PI 355110, and PI 270210) were observed as BW resistance, with PI 645370 showing the greatest resistance. The broad-sense heritability for BW resistance was estimated as 59.9% and 42.8% based on a 0–4 scale of disease incidence and the disease severity index, respectively. Two distinct clusters (sub-populations) were detected among 39 of the 40 accessions. The five identified BW-resistant accessions were distributed in both clusters, suggesting a likely difference in the genetic base among the five resistance accessions. The resistant accessions will contribute significantly to the tomato breeding program to develop new cultivars with BW resistance.

A haplotype-resolved chromosome-level assembly and annotation of European hazelnut (C. avellana cv. Jefferson) provides insight into mechanisms of eastern filbert blight resistance.

European hazelnut (Corylus avellana L.) is an important tree nut crop. Hazelnut production in North America is currently limited in scalability due to Anisogramma anomala, a fungal pathogen that causes Eastern Filbert Blight (EFB) disease in hazelnut. Successful deployment of EFB resistant cultivars has been limited to the state of Oregon, where the breeding program at Oregon State University (OSU) has released cultivars with a dominant allele at a single resistance locus identified by classical breeding, linkage mapping, and molecular markers. C. avellana cultivar "Jefferson" is resistant to the predominant EFB biotype in Oregon and has been selected by the OSU breeding program as a model for hazelnut genetic and genomic research. Here, we present a near complete, haplotype-resolved chromosome-level hazelnut genome assembly for "Jefferson". This new assembly is a significant improvement over a previously published genome draft. Analysis of genomic regions linked to EFB resistance and self-incompatibility confirmed haplotype splitting and identified new gene candidates that are essential for downstream molecular marker development, thereby facilitating breeding efforts.

Insecticide resistance triggers a reduction of virulence to host‐plant defenses in the brown planthopper

AbstractPlants produce various phytochemicals against herbivory, but phytophagous insects have encountered phytochemicals in the co‐evolutionary history between plants and insects. Selection pressure exerted by phytochemicals triggers a preadaptation to insecticide resistance in insect pests that is due to detoxification systems that are common to phytochemicals and insecticides in the insect's body. We investigated the interaction between the host plant resistance of rice cultivars and the brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae). Forty brown planthopper resistance gene loci (BPHs) that are related to phytochemicals in various cultivars of rice inhibit feeding by N. lugens, but this planthopper has developed virulence to resistant rice cultivars possessing some genes. Nilaparvata lugens has also developed resistance to some insecticides as a rapid adaptation to human‐driven selection. We tested the hypothesis that the evolution of insects' resistance to an insecticide is promoted by their encounters with phytochemicals. We compared the virulence of imidacloprid‐resistant and control N. lugens strains toward seven rice cultivars that possess different genes, and we observed that the imidacloprid‐resistant N. lugens had reduced virulence to three rice cultivars, Rathu Heenati (BPH3, BPH17), Babawee (BPH4), and Balamawee (BPH27, three quantitative trait loci), meaning that the development of imidacloprid resistance has a negative impact on the virulence of N. lugens to three cultivars. Our results indicate trade‐offs rather than a co‐relationship between the evolution of insecticide resistance and encounters with host plant defense.

Evaluation of Sweet Potato (Ipomoea batatas) for Early Blast Disease (Alternaria solani)

Aims: Early blight disease (Alternaria solani) is one of the main biotic factors limiting sweet potato production in the tropics. A multi-locational research was carried out to screen and identified sweet potato accessions that are resistant to the disease.
 Methodology: 21 sweet potato accessions were collected from different agro-ecological zones of Nigeria and screen against Alternaria solani by artificial inoculation of the pathogen in three diverse agro-ecological conditions. The accessions were named against their place of condition. The research were laid out in a Randomized Complete Block Design (RCBD) with three replications. Data were collected on days to 50% flowering, fresh root weight per plant, number of root per plant, number of main branches per plant, and above ground fresh biomass yield per plant at 15 weeks after planting (WAP). Disease scoring was done using rating scale 0f 0-9 and analyzed with IRRI STAR software.
 Results: The result revealed that there are variations in the 21 accessions studied. Offa performed best across the three environments followed by Umudike while Ado-Ekiti had the least performance in term of root yield. The screening shows that none of the 21 accessions is highly resistant. Four of the accessions were resistant, six accessions were moderately resistant, four accessions were susceptible, and three accessions were moderately susceptible while 4 accessions were highly susceptible to the pathogen.
 Conclusion: The findings concluded that the resistant accessions that gave high number roots could be used as a gene pool for Alternaria solani resistance breeding for cultivar improvement. The use of the identified resistant accessions with high root yield by farmers is encouraged pending the time commercial Alternaria solani resistant cultivars will be readily available and accessible.

Plant–pathogen interaction with root rot of Panax notoginseng as a model: Insight into pathogen pathogenesis, plant defence response and biological control

AbstractPlant diseases are a major threat affecting the sustainability of global agriculture. Although the breeding of new resistant cultivars is considered to be the primary approach to prevent and control plant diseases, it is dependent on an in‐depth understanding of plant–pathogen interactions. At present, we have an in‐depth understanding of the interactions between model plants and pathogens, such as Arabidopsis thaliana and rice, but we are still in the beginning stage for more non‐model plants (e.g., medicinal plants). Panax notoginseng is the primary source of the high‐value active ingredient triterpenoid saponins. Root rot disease in P. notoginseng has attracted research attention because of its high destructiveness. Understanding the infection stages and strategies of pathogens, plant resistance mechanisms and induced plant defence against pathogens is essential to support agricultural sustainable development of P. notoginseng. Here, we review and summarize, with root rot of P. notoginseng as a model, the current knowledge of plant–pathogen interaction, and feasability of use of microorganisms and secondary metabolites as sources of biological control agents at a low cost. Finally, we also discuss the importance of plant–pathogen interactions in resistance breeding, thereby providing a new strategy to develop green agriculture for non‐model plants.

Differential response of proline metabolism defense, Na+ absorption and deposition to salt stress in salt-tolerant and salt-sensitive rapeseed (Brassica napus L.) genotypes.

Soil salinization is a major abiotic factor threatening rapeseed yields and quality worldwide, yet the adaptive mechanisms underlying salt resistance in rapeseed are not clear. Therefore, this study aimed to explore the differences in growth potential, sodium (Na+) retention in different plant tissues, and transport patterns between salt-tolerant (HY9) and salt-sensitive (XY15) rapeseed genotypes, which cultivated in Hoagland's nutrient solution in either the with or without of 150 mM NaCl stress. The results showed that the inhibition of growth-related parameters of the XY15 genotype was higher than those of the HY9 in response to salt stress. The XY15 had lower photosynthesis, chloroplast disintegration, and pigment content but higher oxidative damage than the HY9. Under NaCl treatment, the proline content in the root of HY9 variety increased by 8.47-fold, surpassing XY15 (5.41-fold). Under salt stress, the HY9 maintained lower Na+ content, while higher K+ content and exhibited a relatively abundant K+/Na+ ratio in root and leaf. HY9 also had lower Na+ absorption, Na+ concentration in xylem sap, and Na+ transfer factor than XY15. Moreover, more Na+ contents were accumulated in the root cell wall of HY9 with higher pectin content and pectin methylesterase (PME) activity than XY15. Collectively, our results showed that salt-tolerant varieties absorbed lower Na+ and retained more Na+ in the root cell wall (carboxyl group in pectin) to avoid leaf salt toxicity and induced higher proline accumulation as a defense and antioxidant system, resulting in higher resistance to salt stress, which provides the theoretical basis for screening salt resistant cultivars.

Screening and Resistance Locus Identification of the Mutant fcrZ22 Resistant to Crown Rot Caused by Fusarium pseudograminearum.

Crown rot caused by Fusarium pseudograminearum is a devastating wheat disease worldwide. In addition to yield losses, the fungi causing Fusarium crown rot (FCR) also deteriorate the quality and safety of food because of the production of mycotoxins. Planting resistant cultivars is an effective way to control FCR. However, most wheat cultivars are susceptible to FCR. Therefore, development of new sources and detection of loci for FCR resistance are necessary. In the present study, a resistant mutant, fcrZ22, was identified from an ethyl methane sulfonate (EMS)-mutagenized population of the cultivar Zhoumai 22, and then fcrZ22 was crossed with the wild type to produce an F2 population. Genetic analysis of the F2 population was carried out by the mixed inheritance model of major genes plus polygenes, and 20 resistant and 20 susceptible plants were selected to assemble mixed pools. Combining 660K SNP arrays, the resistance loci were detected by bulked segregant analysis. The resistance to FCR caused by F. pseudograminearum in the F2 population was in accordance with the "mixed model with two major genes of additive-epistasis effect + additive-dominant polygenes," and the heritability of the major gene was 0.92. Twenty-one loci were detected, which were located on 10 chromosomes, namely, 1B (1), 1D (1), 2A (3), 1B (1), 3A (3), 3B (3), 4A (2), 5A (2), 7A (3), and 7B (2). Among the 21 loci, eight were new loci for FCR resistance. This is the first report of detecting loci for FCR resistance from a mutant. The results of the present study provided excellent germplasm resources for breeding wheat cultivars with FCR resistance and laid the foundation for fine mapping of FCR resistance loci.

Evaluation of new disease resistant cultivars in a cool climate region in Australia

Evaluation of new disease resistant cultivars in a cool climate region in Australia

GhWRKY55 as a negative regulator of cotton resistance to Verticillium dahliae via lignin biosynthetic and jasmonic acid signaling pathways

Verticillium wilt, caused by Verticillium dahliae, is a major threat to cotton yield and quality. While the WRKY gene family has been shown to be involved in plant defense against V. dahliae, the underlying mechanisms remain unclear. In this study, we found that Gossypium hirsutum WRKY DNA binding protein 55 (GhWRKY55) negatively regulates cotton defense against V. dahliae. GhWRKY55 expression was suppressed in resistant cotton cultivars following V. dahliae inoculation, and the overexpression of GhWRKY55 in Arabidopsis decreased the resistance to V. dahliae. Silencing of GhWRKY55 enhanced the resistance of susceptible cotton to V. dahliae by increasing salicylic acid (SA) accumulation, decreasing jasmonic acid (JA) levels, and altering lignin content and monomer G/S ratio. Yeast one-hybrid and dual-luciferase assays revealed that GhWRKY55 protein interacts with the promoters of lignin biosynthesis-related gene GhHCT_D10 and JA signaling pathway gene GhPR3_D01–1. Our findings suggest that GhWRKY55 negatively regulates cotton resistance to V. dahliae by affecting lignin biosynthesis and JA signaling pathway. These results provide new insights into the relationship between GhWRKY55, SA/JA, and lignin in defense against V. dahliae.

Induced responses to the wheat pathogen: Tan Spot—(Pyrenophora tritici-repentis) in wheat (Triticum aestivum) focus on changes in defence associated and sugar metabolism

IntroductionTan Spot (TS) disease of wheat is caused by Pyrenophora tritici-repentis (Ptr), where most of the yield loss is linked to diseased flag leaves. As there are no fully resistant cultivars available, elucidating the responses of wheat to Ptr could inform the derivation of new resistant genotypes.ObjectivesThe study aimed to characterise the flag-leaf metabolomes of two spring wheat cultivars (Triticum aestivum L. cv. PF 080719 [PF] and cv. Fundacep Horizonte [FH]) following challenge with Ptr to gain insights into TS disease development.MethodsPF and FH plants were inoculated with a Ptr strain that produces the necrotrophic toxin ToxA. The metabolic changes in flag leaves following challenge (24, 48, 72, and 96 h post-inoculation [hpi]) with Ptr were investigated using untargeted flow infusion ionisation-high resolution mass spectroscopy (FIE-HRMS).ResultsBoth cultivars were susceptible to Ptr at the flag-leaf stage. Comparisons of Ptr- and mock-inoculated plants indicated that a major metabolic shift occurred at 24 hpi in FH, and at 48 hpi in PF. Although most altered metabolites were genotype specific, they were linked to common pathways; phenylpropanoid and flavonoid metabolism. Alterations in sugar metabolism as well as in glycolysis and glucogenesis pathways were also observed. Pathway enrichment analysis suggested that Ptr-triggered alterations in chloroplast and photosynthetic machinery in both cultivars, especially in FH at 96 hpi. In a wheat-Ptr interactome in integrative network analysis, “flavone and flavonol biosynthesis” and “starch and sucrose metabolism” were targeted as the key metabolic processes underlying PF–FH–Ptr interactions.ConclusionThese observations suggest the potential importance of flavone and flavonol biosynthesis as well as bioenergetic shifts in susceptibility to Ptr. This work highlights the value of metabolomic approaches to provide novel insights into wheat pathosystems.

Molecular identification of the causal agent of bacterial wilt in tomato plants in southwestern Paraná

Bacterial wilt, caused by phytopathogenic species of the genus Ralstonia, is one of the main diseases affecting the tomato crop. The Ralstonia solanacearum species complex occurs as a result of variants being widely diverse in terms of adaptation to different climatic conditions, host variations, and aggressiveness, which complicate disease control recommendations. In this study, we employed molecular methods to analyze 26 R. solanacearum isolates collected from tomato plants cultivated in the southwest region of Paraná, Brazil. Isolates were obtained from plants exhibiting wilt symptoms in a protected cultivation system and in an open field. The specific primers 759/760 confirmed the isolates as part of the Ralstonia solanacearum complex, and Nmult primers were used to identify the phylotype. Variability analysis using BOX-PCR with the BOX-A1R primer on 19 isolates revealed molecular diversity. All 26 isolates were confirmed as Ralstonia solanacearum, belonging to phylotype II. Comparison of genomic DNA band patterns amplified by BOX-PCR indicated molecular variability, forming eight groups at a similarity level of 0.63. These results confirm the prevalence of R. solanacearum phylotype II in southwestern Paraná. This information aids decision-making in disease management and contributes to breeding efforts aiming at the development of resistant cultivars.

Distribution and Intensity of Coffee Berry Diseases (Colletotrichum Kahawae Waller and Bridge) in Gurage Zone

In worldwide more than 125 million people and in Ethiopia around 15-16 million peoples were derive their income from Coffee. Coffee berry disease (CBD), coffee wilt disease (CLD) and coffee leaf rust (CLR) are most important coffee diseases in Ethiopia. Previous research works have little information on CBD distribution, status and associated factors in Gurage zone southern parts of Ethiopia. This study was designed to carry out the CBD disease intensity. The assessment was done in Enemorina Ener, Ezha and Cheha districts of Gurage zone during July to August 2017. The study result indicated that CBD was prevalent in all inspected farmers’ field with a disease incidence range of 100% and 86.66%. Percent Severity Index was recorded from 38.89 to 59.44% in all assessed areas. Pearson correlation analysis showed that disease incidence (DI) and percent severity index (PSI) have positive and strong relationship with altitude (r=0.46) and (r=0.73), respectively. It is good when the study was repeated in one more production year and with including other coffee producing districts of Gurage zone. The present study gives clues to generate CBD disease management strategies as short term and develop resistant cultivars for the study area as long term strategy to increase county foreign currency.

Defense Regulatory Network Associated with circRNA in Rice in Response to Brown Planthopper Infestation

The brown planthopper (BPH), Nilaparvata lugens (Stål), a rice-specific pest, has risen to the top of the list of significant pathogens and insects in recent years. Host plant-mediated resistance is an efficient strategy for BPH control. Nonetheless, BPH resistance in rice cultivars has succumbed to the emergence of distinct virulent BPH populations. Circular RNAs (circRNAs) play a pivotal role in regulating plant–environment interactions; however, the mechanisms underlying their insect-resistant functions remain largely unexplored. In this study, we conducted an extensive genome-wide analysis using high-throughput sequencing to explore the response of rice circRNAs to BPH infestations. We identified a total of 186 circRNAs in IR56 rice across two distinct virulence groups: IR-IR56-BPH (referring to IR rice infested by IR56-BPH) and IR-TN1-BPH, along with a control group (IR-CK) without BPH infestation. Among them, 39 circRNAs were upregulated, and 43 circRNAs were downregulated in the comparison between IR-IR56-BPH and IR-CK. Furthermore, in comparison with IR-CK, 42 circRNAs exhibited upregulation in IR-TN1-BPH, while 42 circRNAs showed downregulation. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that the targets of differentially expressed circRNAs were considerably enriched in a multitude of biological processes closely linked to the response to BPH infestations. Furthermore, we assessed a total of 20 randomly selected circRNAs along with their corresponding expression levels. Moreover, we validated the regulatory impact of circRNAs on miRNAs and mRNAs. These findings have led us to construct a conceptual model that circRNA is associated with the defense regulatory network in rice, which is likely facilitated by the mediation of their parental genes and competing endogenous RNA (ceRNA) networks. This model contributes to the understanding of several extensively studied processes in rice-BPH interactions.

Biology, Ecology, and Management of Flea Beetles in Brassica Crops.

Brassica vegetable and oilseed crops are attacked by several different flea beetle species (Chrysomelidae: Alticini). Over the past decades, most research has focused on two Phyllotreta species, Phyllotreta striolata and Phyllotreta cruciferae, which are major pests of oilseed rape in North America. More recently, and especially after the ban of neonicotinoids in the European Union, the cabbage stem flea beetle, Psylliodes chrysocephala, has become greatly important and is now considered to be the major pest of winter oilseed rape in Europe. The major challenges to flea beetle control are the prediction of population dynamics in the field, differential susceptibility to insecticides, and the lack of resistant plant cultivars and other economically viable alternative management strategies. At the same time, many fundamental aspects of flea beetle biology and ecology, which may be relevant for the development of sustainable control strategies, are not well understood. This review focuses on the interactions between flea beetles and plants and summarizes the literature on current management strategies with an emphasis on the potential for biological control in flea beetle management.

Disease Progress and Detection of a California Resistance-Breaking Strain of Tomato Spotted Wilt Virus in Tomato with LAMP and CRISPR-Cas12a Assays

Use of tomato cultivars with the Sw-5 resistance gene cluster has led to the occurrence of resistance-breaking (RB) tomato spotted wilt virus (TSWV) strains globally, including California and, recently, North Carolina and Texas. We documented disease on tomato infected with either an RB strain from California (CA-RB) or a wild type (CA-WT) strain of TSWV on tomato with (cultivar Mountain Merit) or without (cultivar Mountain Fresh Plus) the Sw-5b resistance gene and detected virus incidence over time using microneedle RNA extractions and LAMP. We developed a LAMP/Cas12a assay for detection of the CA-C118Y mutation in a CA-RB strain and tested the assay with field samples. Disease in the susceptible cultivar was less severe with CA-RB than with the CA-WT strain. In contrast, the resistant cultivar had little disease when inoculated with the CA-WT strain but exhibited stunting of greater than 50% when inoculated with the CA-RB strain. In the susceptible tomatoes, the detection rates over time by LAMP reaction were higher in CA-WT than in CA-RB-inoculated plants. In resistant tomato, CA-RB remained detectable by TSWV LAMP over 14 days, whereas the WT strain was undetectable. A two-step LAMP/Cas12a assay differentiated the two strains in 1 h. Our methods were validated with samples from TSWV-infected North Carolina fields. A phylogeny of NSm gene sequences that included North Carolina field samples revealed two independent origins of the North Carolina RB isolates. The LAMP/Cas12 assay showed excellent detection of the CA-C118Y mutation. The TSWV LAMP/Cas12a assay is adaptable for in-field applications on either a smart phone platform or heat block. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Fine mapping and identification of two NtTOM2A homeologs responsible for tobacco mosaic virus replication in tobacco (Nicotiana tabacum L.)

BackgroundTobacco mosaic virus (TMV) is a widely distributed viral disease that threatens many vegetables and horticultural species. Using the resistance gene N which induces a hypersensitivity reaction, is a common strategy for controlling this disease in tobacco (Nicotiana tabacum L.). However, N gene-mediated resistance has its limitations, consequently, identifying resistance genes from resistant germplasms and developing resistant cultivars is an ideal strategy for controlling the damage caused by TMV.ResultsHere, we identified highly TMV-resistant tobacco germplasm, JT88, with markedly reduced viral accumulation following TMV infection. We mapped and cloned two tobamovirus multiplication protein 2A (TOM2A) homeologs responsible for TMV replication using an F2 population derived from a cross between the TMV-susceptible cultivar K326 and the TMV-resistant cultivar JT88. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9)-mediated loss-of-function mutations of two NtTOM2A homeologs almost completely suppressed TMV replication; however, the single gene mutants showed symptoms similar to those of the wild type. Moreover, NtTOM2A natural mutations were rarely detected in 577 tobacco germplasms, and CRISPR/Cas9-mediated variation of NtTOM2A led to shortened plant height, these results indicating that the natural variations in NtTOM2A were rarely applied in tobacco breeding and the NtTOM2A maybe has an impact on growth and development.ConclusionsThe two NtTOM2A homeologs are functionally redundant and negatively regulate TMV resistance. These results deepen our understanding of the molecular mechanisms underlying TMV resistance in tobacco and provide important information for the potential application of NtTOM2A in TMV resistance breeding.

The Autophagy-Related Musa acuminata Protein MaATG8F Interacts with MaATG4B, Regulating Banana Disease Resistance to Fusarium oxysporum f. sp. cubense Tropical Race 4.

Banana is one of the most important fruits in the world due to its status as a major food source for more than 400 million people. Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) causes substantial losses of banana crops every year, and molecular host resistance mechanisms are currently unknown. We here performed a genomewide analysis of the autophagy-related protein 8 (ATG8) family in a wild banana species. The banana genome was found to contain 10 MaATG8 genes. Four MaATG8s formed a gene cluster in the distal part of chromosome 4. Phylogenetic analysis of ATG8 families in banana, Arabidopsis thaliana, citrus, rice, and ginger revealed five major phylogenetic clades shared by all of these plant species, demonstrating evolutionary conservation of the MaATG8 families. The transcriptomic analysis of plants infected with Foc TR4 showed that nine of the MaATG8 genes were more highly induced in resistant cultivars than in susceptible cultivars. Finally, MaATG8F was found to interact with MaATG4B in vitro (with yeast two-hybrid assays), and MaATG8F and MaATG4B all positively regulated banana resistance to Foc TR4. Our study provides novel insights into the structure, distribution, evolution, and expression of the MaATG8 family in bananas. Furthermore, the discovery of interactions between MaATG8F and MaATG4B could facilitate future research of disease resistance genes for the genetic improvement of bananas.

Genetic Analysis of Partially Resistant and Susceptible Chickpea Cultivars in Response to Ascochyta rabiei Infection.

The molecular mechanism involved in chickpea (Cicer arietinum L.) resistance to the necrotrophic fungal pathogen Ascochyta rabiei is not well documented. A. rabiei infection can cause severe damage in chickpea, resulting in significant economic losses. Understanding the resistance mechanism against ascochyta blight can help to define strategies to develop resistant cultivars. In this study, differentially expressed genes from two partially resistant cultivars (CDC Corinne and CDC Luna) and a susceptible cultivar (ICCV 96029) to ascochyta blight were identified in the early stages (24, 48 and 72 h) of A. rabiei infection using RNA-seq. Altogether, 3073 genes were differentially expressed in response to A. rabiei infection across different time points and cultivars. A larger number of differentially expressed genes (DEGs) were found in CDC Corinne and CDC Luna than in ICCV 96029. Various transcription factors including ERF, WRKY, bHLH and MYB were differentially expressed in response to A. rabiei infection. Genes involved in pathogen detection and immune signalings such as receptor-like kinases (RLKs), Leucine-Rich Repeat (LRR)-RLKs, and genes associated with the post-infection defence response were differentially expressed among the cultivars. GO functional enrichment and pathway analysis of the DEGs suggested that the biological processes such as metabolic process, response to stimulus and catalytic activity were overrepresented in both resistant and susceptible chickpea cultivars. The expression patterns of eight randomly selected genes revealed by RNA-seq were confirmed by quantitative PCR (qPCR) analysis. The results provide insights into the complex molecular mechanism of the chickpea defence in response to the A. rabiei infection.

Diagnostics of Fusarium wilt in banana: Current status and challenges

AbstractGlobal banana production is under threat from the rapidly spreading pathogen Fusarium oxysporum f. sp. cubense (Foc) tropical race 4 (TR4), which is pathogenic to Cavendish and many other varieties. Due to the absence of effective control methods and the lack of other market‐acceptable resistant cultivars, early diagnostics, containment and quarantine measures are important to limit further spread and impact of this pathogen. Early detection and identification of the pathogen require reliable diagnostic assays. The reliability of a molecular diagnostic assay is directly linked to the rigour applied at validating the assay according to predetermined standards. For specific detection of a target pathogen using molecular diagnostics, a well‐resolved taxonomy of the target and related species based on their evolutionary relationships is also required. The advent of sequence‐based phylogenetic analysis has given rise to new insights regarding the taxonomic classification of Foc and provided proof for the polyphyletic origin of Foc races, complicating early and reliable detection of the pathogen. Although numerous diagnostic methods for Foc have been developed, choosing a rigorously validated and fit‐for‐purpose method for adoption is currently challenging as advantages and drawbacks for each assay are not always obvious or put into context with prior methodologies. This review compiles and critically dissects published methods that are reported to detect Foc to date and highlights their benefits and constraints to provide a valuable reference for diagnosticians, researchers and policy makers worldwide.

Genetic similarity of four strawberry cultivars in respect to Verticillium wilt susceptibility under in vitro selection

Verticillium wilt caused by pathogenic soil fungus – Vertcillium dahliae Kleb. is one of the most serious strawberry diseases not treated chemically. The strawberry is a species more or less susceptible to Verticillium sp., hence the need to select new genetically resistant cultivars. In this study, susceptibility of four strawberry cultivars to Verticillium wilt was examined under in vitro selection conditions as regards the genetic similarity of selected resistant plants. Microplants of 4 strawberry subclones obtained by in vitro cloning of each cultivar were inoculated in vitro with liquid mycelial homogenate of the pathogen. Development of disease symptoms was observed after 15, 30, 45, 60 and 75 days post inoculation. Results revealed differences of susceptibility to V. dahliae which depended on the subclone. The least susceptible to Verticillium wilt turned out to be ‘Plena’ subclone, followed by the ‘Elsanta’, ‘Feltar’ and ‘Teresa’ subclones. The highest genetic similarity of 59% was found between ‘Elsanta’ and ‘Teresa’ subclones, which after 75 days from inoculation were also characterized by a very similar percentage of resistant plants.