Search

Bacterial leaf blight (BLB) is one of the major rice diseases in Malaysia. This disease causes substantial yield loss as high as 70%. Development of rice varieties which inherited BLB resistant traits is a crucial approach to promote and sustain rice industry in Malaysia. Hence, this study aims were to enhance BLB disease resistant characters of high yielding commercial variety MR219 through backcross breeding approach with supporting tool of marker-assisted selection (MAS). Broad spectrum BLB resistance gene, Xa7 from donor parent IRBB7 were introgressed into the susceptible MR219 (recurrent parent) using two flanking markers ID7 and ID15. At BC3F4, we managed to generate 19 introgressed lines with homozygous Xa7 gene and showed resistant characteristics as donor parent when it was challenged with Xanthomonas oryzae pv. oryzae through artificial inoculation. Recurrent parent MR219 and control variety, MR263 were found to be severely infected by the disease. The improved lines exhibited similar morphological and yield performance characters as to the elite variety, MR219. Two lines, PB-2-107 and PB-2-34 were chosen to be potential lines because of their outstanding performances compared to parent, MR219. This study demonstrates a success story of MAS application in development of improved disease resistance lines of rice against BLB disease. Resumo A mancha bacteriana das folhas (BLB) é uma das principais doenças do arroz na Malásia. Essa doença causa perdas substanciais de rendimento de até 70%. O desenvolvimento de variedades de arroz que herdaram características de resistência ao BLB é uma abordagem crucial para promover e sustentar a indústria do arroz na Malásia. Portanto, o objetivo deste estudo foi aumentar os caracteres BLB resistentes a doenças da variedade comercial MR219 de alto rendimento por meio de uma abordagem de cruzamento retrocruzamento com ferramenta de apoio de seleção assistida por marcador (MAS). O gene de resistência a BLB de amplo espectro, Xa7 do pai doador IRBB7, foi introgressado no MR219 suscetível (pai recorrente) usando dois marcadores flanqueadores ID7 e ID15. No BC3F4, conseguimos gerar 19 linhagens introgressadas com o gene Xa7 homozigoto e apresentamos características de resistência como genitor doador quando desafiado com Xanthomonas oryzae pv. oryzae por inoculação artificial. O pai recorrente MR219 e a variedade controle, MR263, estavam gravemente infectados pela doença. As linhas melhoradas exibiram características morfológicas e de desempenho de rendimento semelhantes às da variedade elite, MR219. Duas linhas, PB-2-107 e PB-2-34, foram escolhidas como linhas potenciais por causa de seus desempenhos excelentes em comparação com a mãe, MR219. Este estudo demonstra uma história de sucesso de aplicação de MAS no desenvolvimento de linhas de arroz melhoradas com resistência a doenças contra a doença BLB.

Plants are considered to have three major forms of resistance against pathogen infection. The first is ‘non host resistance’, which operates broadly at the species level, meaning all members of a plant species generally resist all members of the would-be pathogen species. The other two systems operate at the ‘host’ level. ‘Qualitative host resistance’ is seen when an individual plant cultivar (or genotype)completely resists attempted attack by an individual pathogen strain, whilst ‘partial resistance’ is when a plant cannot completely defend itself. Each of these systems have some underlying molecular principles which will be outlined later. In this issue of New Phytologist, Meile et al.(2023; pp. 1562–1577) describe a novel mechanism by which both partial and non host resistance can be achieved in wheat facing the fungal pathogen Zymoseptoria tritici and its closely related species.

Bacterial spot (BS) is a severe bacterial disease induced by Xanthomonas campestris pv. vesicatoria (Xcv), a pathogen that causes serious damage to pepper growth and yield. It is therefore important to study the mechanisms of pepper resistance to Xcv and to breed and promote Xcv-resistant pepper varieties. However, studies of the responses to Xcv infection in peppers at the protein level are limited. Here, we examined Xcv-induced proteomic changes in leaves of the BS susceptible bell pepper ECW and the resistant bell pepper VI037601 using the isobaric tags for relative and absolute quantitation (iTRAQ)-based protein labeling technology. A total of 6 120 distinct proteins were identified, and there were 1 289 significantly differentially accumulated proteins (DAPs) in ECW and VI037601 leaves after Xcv inoculation. Among these, 339 (250 up- and 89 down-regulated) and 479 (300 up- and 179 down-regulated) DAPs were specifically identified in ECW and VI037601, respectively, with 459 (364 up- and 95 down-regulated) similarly expressed DAPs being shared by ECW and VI037601. Based on bioinformatics analysis, many defense-associated proteins were identified as up-regulated in ECW and VI037601, especially the proteins involved in plant-pathogen interaction, phenylpropanoid biosynthesis, protein processing in the endoplasmic reticulum, and MAPK signaling pathway - plant. Moreover, we evaluated transcript levels of six differentially expressed genes from the iTRAQ results by qRT-PCR. The analysis revealed transcriptional changes that were consistent with the changes at the protein level. This study will provide a valuable resource for understanding the molecular basis of pepper resistance to Xcv infection and for improving the disease resistance of pepper cultivars.

Dietary manipulation to maintain fish health and reduce bacterial infection through the use of immunostimulants has been widely used worldwide. A broad range of bioactive substances capable of optimising animal health has been found in several insect species, including antimicrobial/antiviral peptides, polysaccharides such as chitin, lauric acid, and insect products such as honey. Recently, we identified a novel bioactive polysaccharide from Bombyx mori, termed silkrose-BM, that can activate innate immunity in mammalian RAW264.7 macrophages and provide effective protection against vibriosis in penaeid prawns. However, the efficacy of dietary silkrose-BM in teleosts remains unclear. Here, we investigated the effects of dietary inclusion of silkrose-BM in Japanese medaka (Oryzias latipes) after they were artificially challenged with Edwardsiella tarda. The survival of medaka after infection with E. tarda was significantly improved by dietary silkrose-BM at a concentration of 10, 100, and 1000 ng/g. RNA-seq analysis was performed in the intestine and liver of the medaka to identify changes in the transcriptional profiling evoked by silkrose-BM. The dietary silkrose-BM group showed 1,194 and 2,259 differentially expressed genes (DEGs) in the intestine and liver, respectively, when compared with the control group prior to E. tarda infection. Functional enrichment analysis of DEGs showed several putative genes involved in the Toll-like receptor/nuclear factor κB pathway, cytokine-cytokine receptor interactions, complement cascade, antimicrobial peptides, and junctional modification. Taken together, these results suggest that silkrose-BM used as an immunostimulant can improve the immune system and resistance to edwardsiellosis in teleosts.

Root rot of Panax notoginseng, a precious Chinese medicinal plant, seriously impacts its sustainable production. However, the molecular regulatory mechanisms employed by P. notoginseng against root rot pathogens, including Fusarium solani, are still unclear. In this study, the PnMYB2 gene was isolated, and its expression was affected by independent treatments with four signaling molecules (methyl jasmonate, ethephon, salicylic acid, and hydrogen peroxide) as assessed by quantitative real-time PCR. Moreover, the PnMYB2 expression level was induced by F. solani infection. The PnMYB2 protein localized to the nucleus and may function as a transcription factor. When overexpressed in transgenic tobacco, the PnMYB2 gene conferred resistance to F. solani. Jasmonic acid (JA) metabolism and disease resistance-related genes were induced in the transgenic tobacco, and the JA content significantly increased compared with in the wild type. Additionally, transcriptome sequencing, Kyoto Encyclopedia of Genes and Genomes annotation enrichment, and metabolic pathway analyses of the differentially expressed genes in the transgenic tobacco revealed that JA metabolic, photosynthetic, and defense response-related pathways were activated. In summary, PnMYB2 is an important transcription factor in the defense responses of P. notoginseng against root rot pathogens that acts by regulating JA signaling, photosynthesis, and disease-resistance genes.

Sheath blight is a serious rice disease worldwide, and genes involved in resistance remain unclear. In the present study, a virulent field isolate of Rhizoctonia solani was used to inoculate detached leaves of a sheath blight-resistant rice cultivar, Jasmine 85; a suppression subtractive cDNA library was constructed using RNA isolated 16 h postinoculation (hpi); and differentially expressed genes were identified from the cDNA library. A total of 159 uniquely expressed sequence tags were identified, including 105 from rice with enrichment in categories related to cellular response, molecular signaling, and host defense. Coupled with gene expression studies by DNA microarray, 27 highly induced genes involved in signal transduction and defense responses were identified within 16 hpi. Three members of the ATP-binding cassette (ABC) transporter gene family ( OsABC1, OsABC9, and OsABC12) encoding pleiotropic drug resistance-like ABC transporters were mapped to different sheath blight resistance quantitative trait loci (QTLs), and their differential expressions were validated. Three high-resolution melting (HRM) markers were developed from these ABC gene family members to distinguish alleles between sheath blight-susceptible cultivar Lemont and resistant cultivar Jasmine 85. Association of sheath blight resistance to these HRM markers was examined in 77 recombinant inbred lines derived from the cross between Jasmine 85 and Lemont. The OsABC9 gene located in a major sheath blight resistance QTL qShB9-2 showed a major contribution to sheath blight resistance. These results are useful for marker-assisted selection and functional validation of the ABC genes in sheath blight disease resistance. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2022.

Ash dieback, caused by Hymenoscyphus fraxineus, is a serious disease of common and narrow-leaved ash in Europe. The resistance of individual trees seems to be important for the maintenance of ash in European forests. In this in situ wound inoculation study, the susceptibility and differences in resistance to H. fraxineus between Fraxinus excelsior and F. angustifolia clones were assessed. Neither of the tested clones revealed total resistance to ash dieback; variety between the tested clones was observed. Differences in necroses lengths were significant between clones and between two ash species. Longer necroses were formed in F. angustifolia than in F. excelsior. Some clones exhibiting some resistance to the pathogen were identified.

The response of the Mi-1 gene to different densities of Meloidogyne incognita race 2 was investigated under controlled conditions. Susceptible and resistant tomato seedlings were inoculated with 25, 50, 100, 200, 400, 1000, 2000, 5000 and 10 000 second-stage juveniles of M. incognita. Plants were uprooted 8 weeks after inoculation and the numbers of egg masses and galls on the roots, and second-stage juveniles in 100 g soil per pot were counted. In susceptible plants, there was a correlation between the number of egg masses on roots until 2000 J2 inoculum densities. In resistant plants, when inoculum densities increased, the number of egg masses and galls also increased. The reproduction factor ratio was >1 in the susceptible plant and

Eyespot is one of the most important fungal diseases of the stem base of wheat (Triticum aestivum L.). The presented study clearly demonstrated that the Pch1 gene was the main effective source for reducing the eyespot disease score in the analyzed winter wheat lines. Nevertheless, Pch1 was present only in 8−9% of the investigated lines. Using an isoenzymatic marker and molecular markers, the presence of the Pch1 gene and lack of the Pch2 gene was identified in six lines. Two lines, SMH 9409 and DL 358/13/4, were polymorphic in an isoenzymatic marker study. In the remaining three lines, C 3373/11-1, KBH 15.15 and KBP 1416, the Pch1 gene was identified only with the use of an isoenzymatic marker. Both genes Pch1 and Pch2, as well as the resistant variety Rendezvous, were found in three lines: DD 248/12, KBP 15.2 and STH 4431. In line DD 708/13, the presence of the Pch1 and Pch2 genes was identified, where the association between the Pch1 and the locus of the Xorw5 marker was broken. It was shown that the presence or absence of Pch1 and Pch2 genes did not significantly affect the grain yield (from the plot), although the yield was highest in the presence of both genes. A significant effect of the presence of the Pch1 gene on thousand kernel weight (TKW) was observed. Lines with the Pch1 gene showed significantly higher TKW values than lines without both genes or with the Pch2 gene only.

All native North American white pines are highly susceptible to white pine blister rust (WPBR) caused by Cronartium ribicola. Understanding genomic diversity and molecular mechanisms underlying genetic resistance to WPBR remains one of the great challenges in improvement of white pines. To compare major gene resistance (MGR) present in two species, southwestern white pine (Pinus strobiformis) Cr3 and limber pine (P. flexilis) Cr4, we performed association analyses of Cr3-controlled resistant traits using single nucleotide polymorphism (SNP) assays designed with Cr4-linked polymorphic genes. We found that ∼70% of P. flexilis SNPs were transferable to P. strobiformis. Furthermore, several Cr4-linked SNPs were significantly associated with the Cr3-controlled traits in P. strobiformis families. The most significantly associated SNP (M326511_1126R) almost colocalized with Cr4 on the Pinus consensus linkage group 8, suggesting that Cr3 and Cr4 might be the same R locus, or have localizations very close to each other in the syntenic region of the P. strobiformis and P. flexilis genomes. M326511_1126R was identified as a nonsynonymous SNP, causing amino acid change (Val376Ile) in a putative pectin acetylesterase, with coding sequences identical between the two species. Moreover, top Cr3-associated SNPs were further developed as TaqMan genotyping assays, suggesting their usefulness as marker-assisted selection (MAS) tools to distinguish genotypes between quantitative resistance and MGR. This work demonstrates the successful transferability of SNP markers between two closely related white pine species in the hybrid zone, and the possibility for deployment of MAS tools to facilitate long-term WPBR management in P. strobiformis breeding and conservation.

Apple Valsa canker is considered one of the most serious apple diseases. Dopamine is a catecholamine with key physiological functions in plants. Tyrosine decarboxylase (TYDC) is not only involved in the synthesis of dopamine in plants but may also play an important role in the resistance of plants to pathogen infection. In this study, we show that 100-μM exogenous dopamine application and Malus domestica TYDC (MdTYDC) overexpression (or overexpressing, OE) enhances the resistance of apple to Valsa mali infection, likely because the increased dopamine content reduces the accumulation of H2O2 and increases the accumulation of phenolic compounds and salicylic acid (SA) in dopamine-treated and OE apple plants. The activity of chitinase and β-1, 3-glucanase and the expression of SA-related genes were induced more strongly by V. mali in dopamine-treated and OE apples. The dopamine content was significantly higher in dopamine-treated and OE apples than in their respective controls under both normal and inoculated conditions (P < 0.05). Overall, these findings indicate that the application of exogenous dopamine and the OE of MdTYDC may enhance the resistance of apples to V. mali infection by altering the dopamine content, which improves antioxidant capacity, promotes the accumulation of phenolic compounds and SA, and enhances the activity of disease resistance-related proteins.

Broomcorn millet smut caused by the fungus Anthracocystis destruens is one of the most destructive diseases in broomcorn millet production. The life cycle of A. destruens and host defense responses against A. destruens remain elusive. Here we investigated the disease symptom development and the parasitic process of A. destruens as well as the ultrastructure of the host–pathogen interface. The results showed that there are four typical symptoms of broomcorn millet smut, which are blackfly, cluster leaves, hedgehog head, and incomplete fruiting. A. destruens colonizes all tissues of broomcorn millet but produces teliospores only in the inflorescence. After infection, A. destruens proliferates in the host, likely in a systemic manner. Ultrastructural study of the infected inflorescence showed that the pathogen grows intercellularly and intracellularly within the host. The host activates defense response to prevent pathogen infection, accumulation of callose analogs and highly electron-dense deposits to resist A. destruens infection.

AAC Redberry hard red spring wheat (Triticum aestivum L.) has a grain yield significantly higher than the check cultivars Katepwa, and Lillian and is similar to Carberry. AAC Redberry matures in a similar number of days as Katewpa and Lillian, and is significantly earlier maturing than Carberry. AAC Redberry has an awned spike, and a low lodging score indicative of strong straw that is significantly lower than Katepwa and Lillian but significantly higher than Carberry. Plant stature is taller than Carberry, but shorter than Lillian and Katepwa. AAC Redberry expressed resistance to prevalent races of leaf rust, stem rust, yellow rust, loose smut, moderate resistance to common bunt and intermediate resistance to Fusarium head blight. AAC Redberry has quality attributes within the range of the check cultivars and is eligible for grades of Canada Western Red Spring wheat.

Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4) causes an early season cotton disease including seedling deaths. This study compared two Pima cottons (Gossypium barbadense) in the infection process of FOV4 using a confocal and a scanning electron microscope. Seedlings were grown in a hydroponic system and inoculated with a virulent local FOV4 isolate. As compared with the susceptible Pima S-7, the resistant Pima PHY 841 RF had significantly fewer conidia attached and germinated on the root surface. FOV4 penetration into the root epidermis of PHY 841 RF was delayed until 24 h postinoculation (hpi) as compared with 8 hpi in Pima S-7. In Pima S-7, hyphae progressed to the xylem through the cortex between 5 and 7 days postinoculation. However, hyphae grew much slower in the cortex with no apparent hyphae observed in the xylem of PHY 841 RF. At plant maturity, no FOV4 was detected through fungal isolation and PCR in the stem of PHY 841 RF and its resistance donor parents PHY 800 and Pima S-6, as compared with Pima S-7 and DP 744 with positive results. The results demonstrate that PHY 841 RF is resistant to FOV4, due to delayed infection, reduced fungal growth and reproduction, and prevention of the fungus from invading the xylem.

Biocontrol agents can control pathogens by reenforcing systemic plant resistance through systemic acquired resistance (SAR) or induced systemic resistance (ISR). Trichoderma spp. can activate the plant immune system through ISR, priming molecular mechanisms of defense against pathogens. Entomopathogenic fungi (EPF) can infect a wide range of arthropod pests and play an important role in reducing pests’ population. Here, we investigated the mechanisms by which EPF control plant diseases. We tested two well studied EPF, Metarhizium brunneum isolate Mb7 and Beauveria bassiana as the commercial product Velifer, for their ability to induce systemic immunity and disease resistance against several fungal and bacterial phytopathogens, and their ability to promote plant growth. We compared the activity of these EPF to an established biocontrol agent, Trichoderma harzianum T39, a known inducer of systemic plant immunity and broad disease resistance. The three fungal agents were effective against several fungal and bacterial plant pathogens and arthropod pests. Our results indicate that EPF induce systemic plant immunity and disease resistance by activating the plant host defense machinery, as evidenced by increases in reactive oxygen species production and defense gene expression, and that EPF promote plant growth. EPF should be considered as control means for Tuta absoluta. We demonstrate that, with some exceptions, biocontrol in tomato can be equally potent by the tested EPF and T. harzianum T39, against both insect pests and plant pathogens. Taken together, our findings suggest that EPF may find use in broad-spectrum pest and disease management and as plant growth promoting agents.

Southern corn rust (SCR) is a destructive maize disease caused by Puccinia polysora Underw. To investigate the mechanism of SCR resistance in maize, a highly resistant inbred line, L119A, and a highly susceptible line, Lx9801, were subjected to gene mapping and transcriptome analysis. Bulked-segregant analysis coupled with whole-genome sequencing revealed several quantitative trait loci (QTL) on chromosomes 1, 6, 8, and 10. A set of 25 genes, including two coiled-coil nucleotide-binding site leucine-rich repeat (CC-NBS-LRR) genes, were identified as candidate genes for a major-effect QTL on chromosome 10. To investigate the mechanism of SCR resistance in L119A, RNA-seq of P. polysora-inoculated and non-inoculated plants of L119A and Lx9801 was performed. Unexpectedly, the number of differentially expressed genes in inoculated versus non-inoculated L119A plants was about 10 times that of Lx9801, with only 29 common genes identified in both lines, suggesting extensive gene expression changes in the highly resistant but not in the susceptible line. Based on the transcriptome analysis, one of the CC-NBS-LRR candidate genes was confirmed to be upregulated in L119A relative to Lx9801 independently of P. polysora inoculation. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated that transcription factors, as well as genes involved in defense responses and metabolic processes, were dominantly enriched, with the phenylpropanoid biosynthesis pathway most specifically activated. Consistently, accumulation of phenylpropanoid-derived lignin, especially S lignin, was drastically increased in L119A after P. polysora inoculation, but remained unchanged in Lx9801, suggesting a critical role of lignin in SCR resistance. A regulatory network of defense activation and metabolic change in SCR-resistant maize upon P. polysora infection is described.

AAC Vortex is a hard red winter wheat (Triticum aestivum L.) cultivar well-adapted to all areas of western Canada and classified for grades of Canada Western Red Winter (CWRW) wheat. It was developed using doubled-haploid methodology. AAC Vortex was evaluated for registration relative to CDC Buteo, Emerson, Moats, and AAC Elevate across Alberta, Saskatchewan and Manitoba. Based on 44 replicated trials over 4 y (2016/17–2019/20), AAC Vortex had significantly higher grain yield than CDC Buteo and Emerson, and higher grain protein concentration than all of the checks except Emerson. AAC Vortex expressed winter survival and lodging resistance equal to the best checks, medium maturity and height, and acceptable test weight. AAC Vortex was resistant to stem, leaf and stripe rust, moderately resistant to Fusarium head blight, and susceptible to common bunt. AAC Vortex produced flour of higher protein concentration than all of the checks except Emerson, had higher clean wheat flour yield and loaf volume than all of the checks, and was similar in gluten strength to Emerson.

AAC Hodge (BW1069) is a hollow-stemmed, awned and high yielding Canada Western Red Spring (CWRS) wheat cultivar suited to the growing conditions in Western Canada. AAC Hodge was 6% higher yielding than AAC Viewfield, the highest yielding check in the Central Bread Wheat Cooperative (CBWC) registration trials (2017–2019). Within the same test, AAC Hodge was 16% higher yielding than Carberry. AAC Hodge matured 1 d earlier than Carberry and 2 d later than Unity; Unity is the earliest maturing check in the eastern prairie growing conditions. AAC Hodge was 7 cm shorter with better lodging resistance than Unity. The lodging score for AAC Hodge was lower than the mean of the checks. The test weight of AAC Hodge was similar to the mean of the checks. Over the 3 yr of testing (2017–2019), the 1000-kernel weight of AAC Hodge was equal to, or higher than all the checks. The grain protein content of AAC Hodge was equal to that of AAC Viewfield. AAC Hodge was rated moderately resistant to Fusarium head blight (FHB; Fusarium graminearum Schwabe) and resistant to leaf rust (Puccinia triticina Erikss.), stripe rust (Puccinia striiformis Westend), stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn), and common bunt [Tilletia caries (DC) Tul. & C. Tul.]. AAC Hodge ranged from resistant to moderately susceptible for its reaction to the Ug99 family of stem rusts. AAC Hodge was resistant to orange wheat blossom midge (OBWM) (Sitodiplosis mosellana Géhin). AAC Hodge was registered under the CWRS class.

Xanthomonas citri subsp. citri (Xcc) is the causal agent of citrus bacterial canker (CBC), one of the most devastating citrus diseases. Most commercial citrus varieties are susceptible to CBC. However, some citrus varieties and wild citrus germplasms are CBC resistant and are promising in genetic increases in citrus resistance against CBC. We aimed to evaluate citrus germplasms for resistance against CBC. First, we developed a rapid evaluation method based on enhanced yellow fluorescent protein (eYFP)-labeled Xcc. The results demonstrated that eYFP does not affect the growth and virulence of Xcc. Xcc-eYFP allows measurement of bacterial titers but is more efficient and rapid than the plate colony counting method. Next, we evaluated citrus germplasms collected in China. Based on symptoms and bacterial titers, we identified that two citrus germplasms (‘Ichang’ papeda and ‘Huapi’ kumquat) are resistant, whereas eight citrus germplasms (‘Chongyi’ wild mandarin, ‘Mangshan’ wild mandarin, ‘Ledong’ kumquat, ‘Dali’ citron, ‘Yiliang’ citron, ‘Longyan’ kumquat, ‘Bawang’ kumquat, and ‘Daoxian’ wild mandarin) are tolerant. In summary, we have developed a rapid evaluation method to test the resistance of citrus plants against CBC. This method was successfully used to identify two highly canker-resistant citrus germplasms and eight citrus germplasms with canker tolerance. These results could be leveraged in traditional breeding contexts or be used to identify canker resistance genes to increase the disease resistance of commercial citrus varieties via biotechnological approaches.

Common bean (Phaseolus vulgaris) is an annual legume crop that is grown worldwide for its edible dry seeds and tender pods. Marsh spot (MS) of the seeds is a physio-genic stress disease affecting seed quality in beans. Studies have suggested that this disease involves a nutritional disorder caused by manganese deficiency, but the inheritance of resistance to this disease has not been reported. A biparental genetic population composed of 138 recombinant inbred lines (RILs) was developed from a cross between an MS resistant cultivar ‘Cran09’ and an MS susceptible cultivar ‘Messina’. The 138 RILs and their two parents were evaluated for MS resistance during five consecutive years from 2015 to 2019 in sandy and heavy clay soils in Morden, Manitoba, Canada. The MS incidence (MSI) and the MS resistance index (MSRI) representing disease severity were shown to be both highly correlated heritable traits that had high broad-sense heritability values (H2) of 86.5% and 83.2%, respectively. No significant differences for MSI and MSRI were observed between the two soil types in all five- (MSI) or four-year (MSRI) data collection, but significant correlations among years were observed despite MS resistance was moderately affected by year. The MSIs and MSRIs displayed a right-skewed distribution, indicating a mixed genetic model involving a few major genes and polygenes. Using the joint segregation analysis method, the same four major genes with additive-epistasis effects showed the best fit for both traits, explaining 84.4% and 85.3% of the phenotypic variance for MSI and MSRI, respectively. For both traits, the M1, M2, M3 and m4 acted as the favorable (resistant) alleles for the four genes where M and m represent two alleles of each gene. However, due to epistatic effects, only the individuals of the M1M2M3M4 haplotype appeared to be highly resistant, whereas those of the m1m2m3M4 haplotype were the most susceptible. The m4 allele significantly suppressed the additive effects of M1M2M3 on resistance, but decreased susceptibility due to the additive effects of m1m2m3. Further quantitative trait locus (QTL) mapping is warranted to identify and validate individual genes and develop molecular markers for marker-assisted selection of resistant cultivars.

Partial resistance to the biotrophic fungal pathogen Claviceps purpurea, causal agent of ergot, has been found that colocates with mutant alleles of the wheat Reduced height (Rht) loci on chromosomes 4B and 4D. These Rht loci represent the wheat orthologs of the Arabidopsis Della genes. To investigate the role of the Rht mutant DELLA proteins in ergot resistance, we assessed C. purpurea infection in wheat near-isogenic lines (NILs) carrying the gibberellic acid (GA)-insensitive semidwarf alleles Rht-B1b and Rht-D1b and the severe dwarf alleles Rht-B1c and Rht-D1c. NILs of the GA-sensitive alleles Rht8 (chromosome 2D) and Rht12 (chromosome 5A) were also included. A general trend toward increased resistance to C. purpurea, with smaller and lighter sclerotia, was observed on the NILs Rht-B1b, Rht-D1b, Rht-B1c, and Rht-D1c, and also on Rht8. Levels of the bioactive GA4 and the auxin indole-3-acetic acid increased after inoculation with C. purpurea, following similar patterns and implicating a potential auxin-mediated induction of GA biosynthesis. In contrast, jasmonic acid (JA) levels fell in the parental lines ‘Mercia’ and ‘Maris Huntsman’ after inoculation with C. purpurea, but increased in all the Rht-mutant NILs. Inoculation with C. purpurea did not show any informative changes in the levels of salicylic acid. Our results suggest that GA-mediated degradation of the DELLA proteins and down-regulation of JA-signaling pathways supports infection of wheat by C. purpurea. As these responses are generally associated with necrotrophic fungal pathogens, we propose that the biotroph C. purpurea may have a necrotrophic growth stage.

Fusarium crown rot (FCR), caused by Fusarium spp., is a chronic and severe plant disease worldwide. In the last years, the incidence and severity of FCR in China has increased to the point that it is now considered a threat to local wheat crops. In this study, for the first time, the metabolites and transcripts responsive to FCR infection in the partial resistant wheat cultivar 04 Zhong 36 (04z36) and susceptible cultivar Xinmai 26 (XM) were investigated and compared at 20 and 25 days post inoculation (dpi). A total of 443 metabolites were detected, of which 102 were significantly changed because of pathogen colonization. Most of these 102 metabolites belonged to the flavonoid, phenolic acid, amino acid and derivative classes. Some metabolites, such as proline betaine, lauric acid, ribitol, and arabitol, were stably induced by Fusarium pseudograminearum (Fp) infection at two time points and may have important roles in FCR resistance. In line with the reduced seedling height of 04z36 and XM plants, RNA-seq analysis revealed that FCR infection significantly affected the photosynthesis activities in two cultivars. Furthermore, 15 jasmonate ZIM-domain genes (JAZ) in the significantly enriched ‘regulation of jasmonic acid mediated signaling pathway’ in 04z36 were down-regulated. The down-regulation of these JAZ genes in 04z36 may cause a strong activation of the jasmonate signaling pathway. Based on combined data from gene expression and metabolite profiles, two metabolites, benzoxazolin-2-one (BOA) and 6-methoxy-benzoxazolin-2-one (MBOA), involved in the benzoxazinoid-biosynthesis pathway, were tested for their effects on FCR resistance. Both BOA and MBOA significantly reduced fungal growth in vitro and in vivo, and, thus, a higher content of BOA and MBOA in 04z36 may contribute to FCR resistance. Above all, the current analysis extends our understanding of the molecular mechanisms of FCR resistance/susceptibility in wheat and will benefit further efforts for the genetic improvement of disease resistance.

The market success of perennial ryegrass (Lolium perenne L.) cultivars depends on sufficient seed production, as they are propagated by seed. However, breeding for high quality forage production reduces seed yield, and breaking the negative correlation would help to overcome the problem. The foliar disease crown rust is another factor affecting reproductive capacity and thereby seed yield. We evaluated seed yield-related traits and resistance to crown rust in a collection of commercial cultivars and ecotypes of perennial ryegrass and identified genome-wide markers associated with the traits. The study revealed high variation between the ecotype and cultivar groups as well as between years. A genome-wide association study identified 17 DNA single-nucleotide polymorphisms (SNPs) of which eight were associated with crown rust and nine with flag-leaf length. The SNP markers were located within or near predicted genes functioning in defense against pathogens. The identified genes are strong candidates for a further in-depth functional study to continue unravel determination of leaf architecture and crown rust resistance in perennial ryegrass.

Sweet basil (Ocimum basilicum, 2n = 4x = 48) is susceptible to downy mildew caused by Peronospora belbahrii. The Pb1 gene exhibits complete resistance to the disease. However, Pb1 became prone to disease because of occurrence of new virulent races. Here, we show that Zambian accession PI 500950 (Ocimum americanum var. pilosum) is highly resistant to the new races. From an interspecies backcross between PI 500950 and the susceptible ‘Sweet basil’ we obtained, by embryo rescue, a population of 131 BC1F1 plants. This population segregated 73 resistant (58) and susceptible (1:1; P = 0.22) plants, suggesting that resistance is controlled by one incompletely dominant gene called Pb2. To determine whether allelic relationship exists between Pb1 and Pb2, we used two differential races: race 0, which is avirulent to both PI 500945 (Pb1) and PI 500950 (Pb2), and race 1, which is virulent to PI 500945 but avirulent to PI 500950. F1 plants obtained from ‘12-4-6’ (BC6F3 derived from PI 500945) and ‘56’ (BC3F3 derived from PI 500950) showed resistant superiority to both races through dominant complementary interaction. F2 plants segregated to race 0 as follows: 12:3:1 (immune/incomplete resistant/susceptible) as opposed to 9:3:4 to race 1, indicating that Pb1 and Pb2 are not alleles. Because joint action is contributed in F1 plants and in advanced [BC3F3(56) × BC6F3(12-4-6) F4] populations that carry both genes, it can be assumed that both accessions carry two unlinked genes but share a common signal transduction pathway, which leads to dominant complementation superiority of the resistance against different races of basil downy mildew.

Circular RNAs (circRNAs) are a group of covalently closed RNAs, and their biological function is largely unknown. In this study, we focused on circRNAs that are generated from exon back-splicing (exonic circRNAs). The linear RNA counterparts encode functional proteins so that we can compare and investigate the relationship between circular and linear RNAs. We compared circRNA expression profiles between untreated and Pseudomonas syringae-infected Arabidopsis and identified and experimentally validated differentially expressed exonic circRNAs by multiple approaches. We found that exonic circRNAs are preferentially enriched in biological processes that associate with biotic and abiotic stress responses. We discovered that circR194 and circR4022 are involved in plant response against P. syringae infection, whereas circR11208 is involved in response against Botrytis cinerea infection. Intriguingly, our results indicate that these exonic circRNAs function synergistically with their corresponding linear RNAs. Furthermore, circR4022 and circR11208 also play substantial roles in Arabidopsis tolerance to salt stress. This study extends our understanding of the molecular functions of plant circRNAs.

Root rot caused by Fusarium solani is one of the most common fungal diseases in cucumber (Cucumis sativus). Proanthocyanidins (PAs) are known to play important roles in inhibiting the growth of phytopathogens. In addition, CsMYB60 is a known positive regulator of flavonol and PA biosynthesis in cucumber. However, it remains unclear that whether PAs can inhibit the growth of F. solani and whether CsMYB60 serves as a target gene for increasing resistance to phytopathogens in cucumber. In this study, we demonstrated that PAs (or their building block, catechin) could increase the resistance of cucumber seedlings to F. solani both in vitro and in vivo. The addition of catechins, or crude leaf extracts treated with different concentrations of catechins in culture medium, could significantly inhibit the hyphal growth of F. solani. On the other hand, cucumber seedlings treated with catechins showed higher resistance to F. solani than the seedlings of control group. Moreover, transgenic cucumber seedlings overexpressing CsMYB60, with the observed accumulation of PAs, were more resistant to F. solani than the nontransgenic siblings. Therefore, our results suggest that PAs (or catechin) can serve as a biological control agent to protect cucumber plants from the infection of F. solani. More importantly, CsMYB60 holds great promise as a target gene to confer disease resistance during the molecular breeding in cucumber.

Stripe rust caused by Puccinia striiformis f. sp. tritici and powdery mildew caused by Blumeria graminis f. sp. tritici are devastating diseases of wheat worldwide. Exploration of new disease-resistant genes from cultivated wheat and wild relatives are the most effective means of reducing the amounts of fungicides applied to combat these diseases. Thinopyrum scirpeum (2n = 4x = 28, EEEE) is an important promising reservoir of useful genes, including stripe rust and powdery mildew resistance, and may be useful for enhancing wheat disease resistance. Here, we characterize a novel wheat-Th. scirpeum disomic substitution line, K16-730-3, and chromosome-specific markers were developed that can be used to trace the Th. scirpeum chromosome or chromosome segments transferred into wheat. Genomic in situ hybridization and fluorescence in situ hybridization analyses indicated that K16-730-3 is a new 4E (4D) chromosomal substitution line. Evaluation of seedling and adult disease responses revealed that K16-730-3 is resistant to stripe rust and powdery mildew. In addition, no obvious difference in grain yield was observed between K16-730-3 and its wheat parents. Genotyping-by-sequencing analyses indicated that 74 polymerase chain reaction -based markers can accurately trace chromosome 4E which were linked to the disease resistance genes in the wheat background. Further marker validation analyses revealed that 13 specific markers can distinguish between the E-genome chromosomes of Th. scirpeum and the chromosomes of other wheat-related species. The new substitution line K16-730-3 carrying the stripe rust and powdery mildew resistance genes will be useful as novel germplasm in breeding for disease resistance. The markers developed in this study can be used in marker-assisted selection for improvement of disease resistance in wheat.

Viral nervous necrosis (VNN) disease, caused by the nervous necrosis virus (NNV), is a devastating disease, leading to high mortality rate and huge economical loss in aquaculture. In the past 30 years, many studies on the virus, host responses to the virus infection and diagnostics have yielded a lot of knowledge on developing measures to prevent the VNN disease. Although genetic improvement of disease resistance through breeding is inheritable and has long-lasting positive effect on aquaculture, it is a very challenging task in conventional selective breeding for improving disease resistance. With the advances in mapping quantitative trait loci (QTL) and genome wide association studies (GWAS) for NNV resistance in aquaculture species, DNA markers and genes associated with NNV resistance have been identified, making the application of marker-assisted selection (MAS) and genomic selection (GS) for NNV resistance possible. A few genes for NNV resistance are identified and are being used for genome editing to rapidly improve NNV resistance. In this review, we present the current knowledge on the NNV, host responses to NNV infection, diagnostic methods and vaccines available for NNV disease. In addition, we summarize the current status of conventional and molecular breeding for NNV resistance and highlight future directions, including genome editing for improving NNV resistance in aquaculture.

The GDSL esterase/lipase family contains many functional genes that perform important biological functions in growth and development, morphogenesis, seed oil synthesis, and defense responses in plants. The expression of GDSL esterase/lipase genes can respond to biotic and abiotic stresses. Although GDSL esterase/lipase family genes have been identified and studied in other plants, they have not been identified and their functions remain unclear in tomato. This study is the first to identify 80 GDSL esterase/lipase family genes in tomato, which were named SlGELP1–80. These genes were mapped to their positions on the chromosomes and their physical and chemical properties, gene structure, phylogenetic relationships, collinear relationships, and cis-acting elements were analyzed. The spatiotemporal expression characteristics of the SlGELP genes in tomato were diverse. In addition, RNA-seq analysis indicated that the expression patterns of the SlGELP genes in tomato differed before and after inoculation with Stemphylium lycopersici. qRT-PCR was used to analyze the expression of five SlGELP genes after treatments with S. lycopersici, salicylic acid and jasmonic acid. Finally, this study was the first to identify and analyze GDSL esterase/lipase family genes in tomato via bioinformatics approaches, and these findings provide new insights for improving the study of plant disease resistance.

Quinoa is a potential new crop for New England; however, its susceptibility to downy mildew, caused by Peronospora variabilis, is a key obstacle for cultivation. The objectives of this study were to evaluate differential resistance within the Chenopodium genus, identify novel sources of resistance for use in future genetic studies or breeding programs, and investigate phylogenetic relationships of P. variabilis isolates from different Chenopodium hosts. The long-term goal of this research is to develop a resistant variety of quinoa to be grown in New England. Field trials conducted at the University of New Hampshire evaluated downy mildew disease severity on 10 Chenopodium accessions representing four species. Disease severity for each treatment was compared and significant differences in disease severity were observed between accessions. C. berlandieri var. macrocalycium ecotypes collected from Rye Beach, New Hampshire and Appledore Island, Maine exhibited the lowest disease severity over the growing season. P. variabilis was isolated from each accession, and COX2 sequences were compared. Phylogenetic analyses suggest no effect of host species on P. variabilis sequence similarity; however, isolates are shown to cluster by geographic location. This research provides the first step in identifying potential New England native sources of resistance to downy mildew within the genus Chenopodium and provides preliminary information needed to further investigate resistance at the genomic level in Chenopodium spp.

The necrotrophic fungus Botrytis cinerea is a major threat to grapevine cultivation worldwide. Here, a highly resistant Chinese wild grapevine, Vitis amurensis ‘Shuangyou’ (SY), and the susceptible V. vinifera ‘Red Globe’ (RG) were selected for study, and their pathogenic infection and biochemical responses to B. cinerea were evaluated. The results revealed more trichomes on and a thicker cuticle for leaves of SY than RG under scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Both SEM and TEM also showed that conidial germination, appressorium formation, and hyphal development of B. cinerea were delayed on the leaves of resistant SY. Fewer infected hyphae were also observed in leaves of resistant SY when compared with susceptible RG. The infected leaves of resistant SY harbored higher levels of cellulase and pectinase activity during the early infection stages of B. cinerea at 4 h postinoculation (hpi), and higher glucanase and chitinase activity were maintained in the inoculated leaves of SY from 4 through 18 hpi. Lignin was deposited in the infected leaves of susceptible RG but not in resistant SY. Taken together, these results provide insights into the ultrastructural characterizations and physical changes in resistant and susceptible grapevines.

A rich past of generating and configuring genetic structures in wheat (Triticum aestivum) combined with advances in DNA sequencing, bioinformatics and genome engineering has transformed the field of wheat functional genomics. Cloning a gene from the large and complex wheat genome is no longer unattainable; in the past 5 years alone, the molecular identity of 33 wheat disease resistance genes has been elucidated. The next 15 years will see the cloning of most of the ∼460 known wheat resistance genes and their corresponding effectors. Coupled with mechanistic insights into how resistance genes, effectors and pathogenicity targets interact and are affected by different genetic backgrounds, this will drive systems biology and synthetic engineering studies towards the alluring goal of generating durable disease resistance in wheat.

The number of reports associated with wood dieback caused by fungi in the Botryosphaeriaceae in numerous perennial crops worldwide has significantly increased in the past years. In this study, we investigated the interactions between the canker pathogen Neofusicoccum parvum and the almond tree host (Prunus dulcis), with an emphasis on varietal resistance and host response at the cell wall biochemical and histological levels. Plant bioassays in a shaded house showed that among the four commonly planted commercial almond cultivars (‘Butte’, ‘Carmel’, ‘Monterey’, and ‘Nonpareil’), there was no significant varietal difference with respect to resistance to the pathogen. Gummosis was triggered only by fungal infection, not by wounding. A two-dimensional nuclear magnetic resonance and liquid chromatography determination of cell wall polymers showed that infected almond trees differed significantly in their glycosyl and lignin composition compared with healthy, noninfected trees. Response to fungal infection involved a significant increase in lignin, a decrease in glucans, and an overall enrichment in other carbohydrates with a profile similar to those observed in gums. Histological observations revealed the presence of guaiacyl-rich cell wall reinforcements. Confocal microscopy suggested that N. parvum colonized mainly the lumina of xylem vessels and parenchyma cells, and to a lesser extent the gum ducts. We discuss the relevance of these findings in the context of the compartmentalization of decay in trees model in almond and its potential involvement in the vulnerability of the host toward fungal wood canker diseases.

Didymella segeticola (Q. Chen) Q. Chen, Crous & L. Cai (syn. Phoma segeticola) is an important phytopathogen that causes leaf spot on tea, Camellia sinensis [L.] O. Kuntze, which results in huge te...

A field study was conducted at the National Ornamental Research Site at Dominican University California (NORS-DUC). The study goal was to evaluate three chemical inducers applied as foliar treatments for controlling Phytophthora ramorum, on Rhododendron x ‘Cunningham’s White’ nursery plants. The inducers were chlorine dioxide (ElectroBiocide), hydrogen peroxide (OxiDate 2.0), and acibenzolar-s methyl (Actigard). Water samples from the electrostatic sprayer were measured for three physicochemical water properties. Visual assessment of plant foliage, based on the Horsfall- Barratt scale, was conducted at three and five months after chemical treatments. Foliar fluorescence (Fv/Fm) was measured over three dates. The success of P. ramorum inoculations were determined using qPCR methods. Visual assessment across both months showed no signs of P. ramorum infection or chemical injury symptoms. However, P. ramorum infection vis-à-vis qPCR analysis was confirmed. The September Fv/Fm results revealed that all the chemical inducer treatments were equivalent to the water treatment, except for Actigard. The qPCR results were in general agreement with the Fv/Fm results indicating that the rhododendrons were successfully inoculated with P. ramorum but were non-symptomatic. The electrostatic sprayer ionized the water droplets, resulting in increased Fv/Fm values for the water treatments 90 days after application. There was a three-month delay in fluorescence responses to the most effective chemical applications, indicating that woody plants may need to be monitored over the long term to determine accurate responses to foliar treatments.

Boxwood (Buxus spp. L.) is one of the most common and widely planted perennial ornamentals in both home gardens and commercial landscapes. Although considered robust, boxwood is susceptible to several plant pathogens. Boxwood dieback, a recently reported fungal disease caused by Colletotrichum theobromicola, has been spreading rapidly within the United States. Symptoms of boxwood dieback are difficult to distinguish visually in affected plants due to the symptom resemblance to other known biotic and abiotic diseases of boxwood. Previous studies have shown that it may take 2 to 3 months for the symptoms to appear under greenhouse conditions. Although a molecular method has been designed for early, rapid, and accurate pathogen detection, boxwood breeders, nursery growers, and landscape professionals are concerned about the lack of effective management practices. Therefore, the primary objectives of this study were to devise effective disease management strategies by screening cultivars to determine their susceptibility to boxwood dieback and screening various fungicides to determine their effectiveness in managing the disease. Host range studies were conducted by screening a wide variety of boxwood cultivars under greenhouse conditions. The boxwood cultivar ‘Little Missy’ showed much-delayed symptom expression compared with the rest of the cultivars. None of the 11 cultivars were found to be resistant to boxwood dieback. In vitro screening of nine fungicide treatments was conducted to determine inhibition of mycelial growth and spore germination for eight isolates of C. theobromicola collected from eight states in the United States. Of the nine fungicide treatments, difenoconazole + pydiflumetofen showed maximum inhibition of mycelial growth and spore germination at 1 ppm active ingredient, followed by fluxapyroxad + pyraclostrobin, and pyraclostrobin + boscalid at 5 ppm active ingredient. Azoxystrobin + benzovindiflupyr significantly inhibited mycelial growth at 1 ppm but reduced spore germination only at 10 ppm active ingredient. This study provides boxwood industry professionals with critical information pertaining to host susceptibility and fungicide efficacy that may be applied to effectively mitigate boxwood dieback and reduce its further spread.

This study aimed to evaluate the potential role of Bi2O3/TiO2@reduced graphene oxide (rGO) on the antibacterial activity of the typical plant pathogenic bacteria Pst.DC3000 and the enhancement of tomato resistance to pathogenic bacteria. The in vitro antibacterial test showed that 4%rGO-(Bi2O3-TiO2) with a minimum inhibitory concentration of 1280 μg·mL-1 had an inactivation efficiency of 6 log (>99.9999%) for Pst.DC3000 within 150 min under visible light conditions, which far exceeded the other types of nanomaterials under study. Good peroxidase-like and superoxide dismutase-like characteristics and the ability to tightly bind to lipopolysaccharide of the bacterial outer membrane made it adhere to the bacterial surface and produce a large amount of reactive oxygen species [·O2-, hydroxyl (·OH) and H2O2] for in-situ sterilization. This feature changed the permeability of the cell membrane and significantly down-regulated the virulence genes (hrpS, corS, iaaL and flgG), destroying the pathogenicity of the bacteria. Incredibly, 1280 μg·mL-1 (100μL per 1g leaf) 4%rGO-(Bi2O3-TiO2) foliar spray substantially alleviated the pathogenicity of Pst.DC3000, and both growth and photosynthetic function were improved. Simultaneously, the increase in thiols and defense-related enzyme activities (PPO, PAL and POD increased 4.5, 30 and 10 U·g-1·FW) indicated that 4%rGO-(Bi2O3-TiO2) significantly enhanced tomato resistance to Pst.DC3000, and PR-2 and PR-13 genes up-regulated 2.39- and 3.35-fold verified the enhancement of disease resistance. In conclusion, in vitro and in vivo experiments showed that 4%rGO-(Bi2O3-TiO2) stood out in plant resistance and disease resistance and had potential application value in agricultural nanotechnology.

Kiwifruit is an extremely perishable fruit; postharvest disease and senescence during storage can reduce the fruit quality, resulting in economic loss. Considerable research effort has focused on identifying safe and cost-effective ways to preserve fresh kiwifruit. To this end, the present study investigated the effects of alginate oligosaccharide (AOS) soaking treatment on postharvest quality and disease in the ‘Bruno’ variety of kiwifruit. The involved physiological mechanisms were further explored. The results showed that AOS did not inhibit the growth of Botrytis cinerea in vitro, the causal agent of gray mold in kiwifruit, but reduced the incidence of gray mold and diameter of lesions of kiwifruit during storage. Kiwifruit treated with 50 mg • L−1 AOS showed a higher degree of firmness and lower soluble solid content than control fruit treated with distilled water. Moreover, AOS treatment inhibited the activity of polygalacturonase and pectinesterase, while enhancing the activity of polyphenoloxidase, l-phenylalanine ammonia lyase and β-1,3-glucanase related to pathogen defense, and also improved total antioxidant capacity determined by the DPPH, FRAP, and ABTS methods in kiwifruit. These results indicate that 50 mg • L −1 AOS can confer disease resistance in kiwifruit during storage.

The study was executed to find out the potential effects spent coffee ground (SCG) on Nile tilapia's skin mucosal and serum immunities, disease prevention, and growth rate reared in a biofloc system. Nile tilapia fingerlings (average weight 15.25 ± 0.07 g) were disseminated into 15 aquaria (150 L tank−1) at a density of 20 fish per aquarium and treated five diets: SCG1 (control), SCG2 (10 g kg−1), SCG3 (20 g kg−1), SCG4 (40 g kg−1), and SCG5 (80 g kg−1) for eight weeks. A Completely Randomized Design (CRD) with three replications was applied. Growth rate, skin mucus, and serum immunities were quantified every 4 weeks; whereas the challenge study was conducted at the termination of the feeding trial. The outputs indicated that dietary incorporation of SCG give rise to the enhancement of SGR and FCR in comparison with the control, with best levels noted in fish fed SCG2 diet. Similarly, significant enhancements in skin mucosal and serum immunities were revealed in fish treated SCG2 over the control and other SCG diets. Likewise, higher survival rates against Streptococcus agalactiae were displayed in fish fed SCG, with the maximum level displayed in the fish treated SCG2. In conclusion, dietary supplementation of SCG2 (10 g kg−1) can be potential used as immunostimulants in tilapia aquaculture.

Sclerotinia sclerotiorum is a necrotrophic fungus causing devastating stem rot and associated yield losses of canola/rapeseed (Brassica napus) worldwide, including in Australia. Developing host resistance against Sclerotinia stem rot is critical if this disease in canola/rapeseed is to be successfully managed, as cultural or chemical control options provide only partial or sporadic control. Three B. napus breeding populations, C2, C5 and C6, including the parents, F1, F2, BC1P1, and BC2P2, were used in a field study with an objective of exploring the inheritance pattern of disease resistance (based on stem lesion length [SLL]) and the genetic relationships of disease with stem diameter (SD) or days to first flowering (DTF), and to compare these new adult plant stem resistances against S. sclerotiorum with those of seedling (cotyledon and leaf) resistances in earlier studies. Heritability (broad sense) of SLL was 0.57 and 0.73 for population C2 at 3 and 5 weeks postinoculation and 0.21 for population C5 at 5 weeks postinoculation. Additive genetic variance was evident within all 3 populations for DTF but not for SD. Narrow-sense heritability for DTF was 0.48 (C2), 0.42 (C5), and 0.32 (C6). SD, DTF, and SLL were all inherited independently, with no significant genetic covariance between traits in bivariate analysis. Genetic variance for SLL in populations C2 and C5 was entirely nonadditive, and there was significant nonadditive genetic covariance of SLL at 3 and 5 weeks postinoculation. Generation means analysis in population C2 supported the conclusion that complex epistatic interactions controlled SLL. Several C2 and C5 progeny showed high adult plant stem resistance, which may be critical in developing enhanced stem resistance in canola/rapeseed. Although population C6 showed no genetic variation for SLL resistance in this study, it showed significant nonadditive genetic variance at the cotyledon and leaf stages in earlier studies. We conclude that host resistance varies across different plant growth stages, and breeding must be targeted for resistance at each growth stage. In populations C2, C5, and C6, resistance to S. sclerotiorum in stem, leaf, and cotyledon was always controlled by nonadditive effects such as complex epistasis or dominance. Overall, our findings in relation to the quantitative inheritance of Sclerotinia stem rot resistance, together with the new high-level resistances identified, will enable breeders to select/develop genotypes with enhanced resistances to S. sclerotiorum.

Maize stalk rot caused by Fusarium graminearum can lead to severe losses and accumulation of mycotoxins with detrimental effects on livestock health. Because few management strategies are available, the development of resistant varieties is considered the most cost-effective way to control the disease. However, the stalk-tissue-specific mechanisms underlying resistance to F. graminearum remain poorly understood, although it is believed to be strongly influenced by environmental factors. In this study, we performed a temporal transcriptome analysis of two maize inbred lines with contrasting responses to stalk rot using gene expression profiling. We observed differential downregulation of gene expression during the first 2 weeks in a resistant inbred line inoculated with F. graminearum. Time-course gene ontology enrichment analysis suggests that resistance may be caused by a modulation of gene expression associated with redox homeostasis, hormone biosynthesis, cytoskeleton activity, and cell wall remodeling. We validated our gene expression profiling data by measuring the expression of 10 differentially expressed genes using quantitative reverse-transcription PCR. Our analyses also revealed the effect of two environmental conditions with contrasting temperatures and relative humidity on the resistant phenotype and gene expression. This research expands our knowledge of molecular events underlying resistance to stalk rot and the effect of environmental conditions on the disease interaction. Our findings can be exploited for the development of resistant varieties. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

An eight-week feeding trial was performed to assess the effect of different dietary levels (0, 0.5, 1.0, and 1.5%) of β-glucan (sourced from Saccharomyces cerevisiae) on growth, survival, immunological parameters (immune gene expression, lysozyme, and antiprotease), total antioxidant status, thermal tolerance, and disease resistance of Tor putitora fry. Feeding of moderate doses (0.5 and 1.0%) of β-glucan significantly improved survival but not weight gain percentage as compared to that received unsupplemented control and highest dose (1.5%) of glucan. Supplementation of β-glucan in diets differentially influenced the mRNA expression of cytokine and other immune genes. For instance, transcripts of cytokines such as tnf-α and il-1β were significantly upregulated, while ifn-γ and il-10 were unaffected by β-glucan intake. Also, the relative mRNA expression of tlr-5 and hepcidin1 along with lysozyme and antiprotease activities were remained largely unchanged by dietary glucan administration. In contrast, β-glucan induced mRNA expression of defensin1 and c3 while decreased the transcript level of mhc-1. On the other hand, dietary inclusion of β-glucan markedly improved total antioxidant levels and extended the thermal tolerance limits at both the ends, as shown by increased CTmax and lower CTmin than the control group. After feeding β-glucan for eight weeks, the fish were bath challenged with a bacterial pathogen, Aeromonas salmonicida. The challenge study results revealed that β-glucan intake improved most of the studied immune parameters, resulting in lower mortality. Overall, dietary inclusion of β-glucan (0.5-1.0%) was efficient in improving the immune responses, thermal tolerance, and disease resistance of T. putitora fry.

Faba bean (Vicia faba L.) is a high value crop in Ethiopia and has versatile uses. The national faba bean breeding program concentrates on the three major traits (grain yield, disease resistance and seed size) of the crop for varietal release for commercial production. Hence, ten faba bean genotypes were evaluated at Adet, Areka, Bekoji, Haramaya, Holetta and Jimma during the main cropping seasons of 2018 and 2019 using a randomized complete block design with four replications with the objectives to select the genotype with best performance in terms of important agronomic traits like grain yield, disease resistance, large seed size and other desirable agronomic traits for high potential production areas in Ethiopia. The combined analysis of variance across locations revealed that there is highly significant (P < 0.01) variation among the tested genotypes for grain yield, 1000-seeds weight, number of pods per plant, and days to 90% physiological maturity. The genotype EH011089-3 showed better performance than the tested genotypes having comparable grain yield performance (3803 kgha-1) with the two standard checks, Numan and Gora (3790 and 3897 kgha-1, respectively) while it had the highest 1000-seeds weight (1065 g) compared to the two standard checks, Numan and Gora (937 g and 786 g, respectively), i.e., 13.7% and 35.5% advantage, over the two standard checks, respectively. Additionally, EH011089-3 had better resistance for chocolate spot and rust diseases. Therefore, EH011089-3 was the best over the tested varieties and breeding lines. Genotype EH011089-3 is recommended for varietal release for commercial production all over in Ethiopia.

American chestnut (Castanea dentata) is a susceptible host of the invasive necrotrophic fungus Cryphonectria parasitica, which causes chestnut blight disease. The fungal pathogen attacks chestnut stems by invading wounded tissue and secreting oxalate. This process leads to the death of infected host cells and the formation of cankers, eventually girdling stems and killing the tree above the infections. To reduce damage caused by fungal oxalate, American chestnut has been genetically engineered to express a wheat oxalate oxidase (OxO). This enzyme degrades the oxalate produced by the pathogen and confers elevated tolerance to Cryphonectria parasitica infection. We report new lines of transgenic American chestnut that have been developed with the win3.12 inducible promoter from poplar (Populus deltoides) driving OxO expression. This promoter is responsive to both wounding and pathogen infection, with a low level of baseline expression. Targeted expression of OxO to wounded and infected tissue is sought as an alternative to constitutive expression for potential metabolic resource conservation and transgene stability over the long lifetime of a tree and over successive generations of breeding. Transgenic Castanea dentata lines harbouring the win3.12-OxO construct were evaluated for transgene expression patterns and tolerance to chestnut blight infection. OxO transcript levels were low in uninfected plants, but robust infection-induced expression levels were observed, with one transgenic line reaching levels comparable to those of previously characterized CaMV35S-OxO lines. In chestnut blight infection bioassays, win3.12-OxO lines showed elevated disease tolerance similar to blight-resistant Chinese chestnut (Castanea mollissima) controls.

Brinjal little leaf (BLL) is one of the most important and widespread disease of eggplant associated with a phytoplasma in India. It severely infects eggplant cultivation in India and causes serious economic losses. Severe incidence (8 to 30%) of the disease was recorded in three districts of Uttar Pradesh (Varanasi, Mirzapur and Jaunpur) state of India during 2015 and 2016. A total of 58 symptomatic BLL leaf samples were collected from the surveyed fields and processed for nested PCR assays using phytoplasma-specific primer pairs (P1/P7, R16F2n/R16R2). Pair wise sequence identity and phylogeny analysis of 16S rRNA gene sequences of BLL isolates in the study confirmed association of Ca. P. trifoli (16SrVI group) with the BLL symptomatic samples. Association of similar strain of phytoplasma was identified in Hishimonus phycitis collected in brinjal fields at all the locations, utilizing a similar set of primers pairs as described above. The population of H. phycitis was positively correlated with the incidence of BLL disease in the fields. The phytoplasma indexing of 55 eggplants varieties and 17 wild Solanum species through PCR assays revealed that one eggplant cultivated variety (Uttara) and 17 wild Solanum species were found immune, one resistant (Pusa Ankur) and 12 eggplant varieties/lines were found moderately resistant to BLL. However, all the 17 wild Solanum species were recorded free from phytoplasmas in PCR assays. Further, biochemical analysis of the resistant eggplant varieties showed higher peroxidase and polyphenol oxidase enzymatic activities along with the increased total phenols content. These resistant varieties identified in the present study can be utilized as pre-breeding materials to breed and develop eggplant resistance to BLL phytoplasma disease.

The Plant Resistance Genes database (PRGdb; http://prgdb.org/prgdb4/) has been greatly expanded, keeping pace with the increasing amount of available knowledge and data (sequenced proteomes, cloned genes, public analysis data, etc.). The easy-to-use style of the database website has been maintained, while an updated prediction tool, more data and a new section have been added. This new section will contain plant resistance transcriptomic experiments, providing additional easy-to-access experimental information. DRAGO3, the tool for automatic annotation and prediction of plant resistance genes behind PRGdb, has been improved in both accuracy and sensitivity, leading to more reliable predictions. PRGdb offers 199 reference resistance genes and 586.652 putative resistance genes from 182 sequenced proteomes. Compared to the previous release, PRGdb 4.0 has increased the number of reference resistance genes from 153 to 199, the number of putative resistance genes from 177K from 76 proteomes to 586K from 182 sequenced proteomes. A new section has been created that collects plant-pathogen transcriptomic data for five species of agricultural interest. Thereby, with these improvements and data expansions, PRGdb 4.0 aims to serve as a reference to the plant scientific community and breeders worldwide, helping to further study plant resistance mechanisms that contribute to fighting pathogens.

Populus davidiana × Populus bolleana (PdPap) root rot caused by Fusarium oxysporum is a major disease in China. Controlling this disease requires extensive use of chemicals. The use of plant endophytes, such as Bacillus, may be a suitable alternative to chemical agents. In this study, we isolated a strain of Bacillus amyloliquefaciens (AW3) by thermal stimulation and confrontation method from fleshy tap roots of Brassica rapa L. We then determined its inhibitory effect on the growth of F. oxysporum (Fox68) and how it induces the disease resistance of PdPap. The confrontation area and roots were visualized using an optical microscope and a scanning electron microscope, respectively, and mycelial cell malformation, swelling, and distortion observed. AW3 and F. oxysporum were inoculated in a variety of combinations that reduced the disease level. PdPap defense-related enzymes, such as PAL, PPO, SOD, and CAT, increased significantly. Besides, several genes associated with plant defense and hormonal signal transduction were highly expressed. Under the biological stress of Fox68, AW3 directly acted on the hyphae of Fox68, reducing the infection of PdPap by Fox68 and promoting PdPap growth. AW3 also induced the accumulation of defense-related enzymes/genes that conferred resistance. Therefore, AW3 could serve as a bio-control agent of wilt disease caused by F. oxysporum in PdPap.