Necrotic Symptoms Research Articles

Tomato mottle mosaic virus: Characterization, resistance gene effectiveness, and quintuplex RT-PCR detection system

Tomato mottle mosaic virus (ToMMV), an economically important species of the genus Tobamovirus, causes significant loss in yield and quality of tomato fruits. Here, we identified the Shandong isolate of ToMMV (ToMMV-SD) collected from symptomatic tomato fruits in Weifang, Shandong Province of China. ToMMV-SD caused symptoms such as severe mosaic, mottling, and necrosis of tomato leaves, yellow spot and necrotic lesions on tomato fruits. The obtained full genome of ToMMV-SD was 6 399 nucleotides (accession number MW373515) and had the highest identity of 99.5% with that of isolate SC13-051 from the United States of America at the genomic level. The infectious clone of ToMMV-SD was constructed and induced clear mosaic and necrotic symptoms onto Nicotiana benthamiana leaves. Several commercial tomato cultivars, harboring Tm-22 resistance gene, and pepper cultivars, containing L resistance gene, were susceptible to ToMMV-SD. Plants of Solanum melongena (eggplant) and Brassica pekinensis (napa cabbage) showed mottling symptoms, while N. tabacum cv. Zhongyan 100 displayed latent infection. ToMMV-SD did not infect plants of N. tabacum cv. Xanthi NN, Brassica rapa ssp. chinensis (bok choy), Raphanus sativus (radish), Vigna unguiculata cv. Yuanzhong 28-2 (cowpea), or Tm-22 transgenic N. benthamiana. A quintuplex RT-PCR system differentiated ToMMV from tomato mosaic virus, tomato brown rugose fruit virus, tobacco mosaic virus, and tomato spotted wilt virus, with the threshold amount of 0.02 pg. These results highlight the threat posed by ToMMV to tomato and pepper cultivation and offer an efficient detection system for the simultaneous detection of four tobamoviruses and tomato spotted wilt virus infecting tomato plants in the field.

Diverse Effect of Two Cytokinins, Kinetin and Benzyladenine, on Plant Development, Biotic Stress Tolerance, and Gene Expression.

The plant hormones cytokinins affect a various array of plant growth and development processes as well as responses to biotic and abiotic stresses. In this study, the opposite effect of two different cytokinins kinetin (N6-furfuryladenine) and benzyladenine (BA) on development and on the tolerance of Arabidopsis and tobacco plants to virus, bacteria, and fungi infection was reported. Treatments of Arabidopsis and tobacco seedlings with saturated solutions of BA inhibited plant progress, while treatments with saturated water solution of kinetin promoted plant development. Furthermore, BA pre-treatments strongly reduced the number of TMV (Tobacco mosaic virus) lesions on tobacco and the tissue damage caused by the incompatible Pseudomonas bacteria on Arabidopsis and tobacco leaves. Similarly, BA pre-treatment significantly reduced the necrotic disease symptoms of Botrytis cinerea infection. Kinetin pre-treatments had a much weaker or no protective effect on the damage caused by the above pathogens. Accordingly, Arabidopsis gene expression profiles after treatments also showed that the two cytokinins have different effects on several plant processes. The gene expression results supported the more robust effect of BA, which up and downregulated more than 2000 genes, while only 436 genes were influenced by kinetin treatment. It is noteworthy that BA and kinetin treatment changed gene expressions in the same direction only in a relatively few cases (73 upregulated and 70 downregulated genes), and even 28 genes were regulated into the opposite directions by BA and kinetin. Both treatments had a strong effect on auxin and gibberellin-related genes, but only BA had a significant effect on cytokinin-induced processes. While kinetin exclusively activated the flavonoid synthesis genes, BA affected more significantly protein synthesis, photosynthesis, and plant defence-related genes. In conclusion, BA solution had sometimes the opposite and generally a much stronger effect than kinetin solution not only on the development and on biotic stress tolerance of tobacco and Arabidopsis plants but also on the gene expressions. The stronger protective effect of BA to necrotic stresses is probably due to its stronger senescence inhibitory effect on plant tissues, as supported by the stronger chlorophyll retardation of the BA-treated leaves.

First Report of Passion Fruit Anthracnose Caused by Colletotrichum constrictum.

Passion fruit (Passiflora edulis) is widely cultivated in tropic and subtropic regions. Because of its unique and intense flavour and high acidity, passion fruit juice concentrate is used in making delectable sauces, desserts, candy, ice cream, sherbet, or blending with other fruit juices. Anthracnose of passion fruit is favored by frequent rainfall and average temperatures above 27°C. In August 2018, anthracnose on passion fruit was observed in commercial plantings in Lincang, Yunnan, China (23.88 N, 100.08 E). Symptoms included lesions of oval to irregular shapes with brown to dark brown borders. Infection covered most of the fruit surface with pink-to-dark sporulation as reported by Tarnowski and Ploetz (2010). A conidial mass from an individual sorus observed on an infected fruit was isolated and cultured on potato dextrose agar (PDA) supplemented with 50 μg ml-1 of streptomycin. From a single microscopic field, two monospore isolates were dissected using a sterile needle, subcultured, and referred to as BXG-1 and BXG-2. Morphological characters including conidia colour, size, and shape were similar between the two isolates. Conidia were aseptate and cylindrical with apex and rounded base. Conidial length ranged from 12.3 to 16.1 µm (avg. 13.5) and width ranged from 5.5 to 6.2 µm (avg. 5.7). Morphologic data were consistent with Colletotrichum constrictum (Damm et al., 2012). To further confirm the fungal species, the ribosomal internal transcribed spacer (ITS), partial sequences of actin (ACT), chitin synthase (CHS-1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and β-tubulin 2 (TUB2) were amplified and sequenced. Primers and PCR amplification were described by Damm et al. (2012). The sequences were compared to type sequences in GenBank. The results showed the ITS (GenBank accession MW828148 and MW828149), ACT (MW855882 and MW855883), CHS-1 (MW855884 and MW855885), GAPDH (MW855886 and MW855887), and TUB2 (MW855888 and MW855889) sequences of the isolates BXG-1 and BXG-2 were 98% identical with sequence data from strain CBS:128504 of C. constrictum. A maximum likelihood tree was constructed using MEGA-X version 10.1.6 (Kumar et al., 2018) based on a combined dataset of the ITS, ACT, CHS-1, GAPDH, and TUB2 sequences of BXG-1 and BXG-2, and those of 18 Colletotrichum spp. previously deposited in GenBank (Damm et al., 2012). The phylogenetic analysis showed that BXG-1 and BXG-2 belong to the C. constrictum clade. Based on morphology and DNA sequencing, BXG-1 and BXG-2 were identified as C. constrictum. To verify pathogenicity, passion fruit were sprayed with a suspension of 1 × 105 conidia ml-1. Control fruit were sprayed with sterilized water. After inoculation, fruit were incubated in an Artificial Climate Box at 27°C and 80% RH. Necrotic symptoms appeared 8 days after inoculation and were similar to those observed on fruit form the field. The pathogen was reisolated from lesions thus fulfilling Koch's postulates. C. constrictum has been reported to cause anthracnose of citrus from Australia (Wang et al., 2021) and mango from Italy (Ismail et al., 2015). To our knowledge, this is the first report of C. constrictum causing anthracnose on passion fruit worldwide, and these data will provide useful information for developing effective control strategies.

Evaluation of tolerance to Fusarium oxysporum and Fusarium solani in Virginia-type tobacco (Nicotiana tabacum L.) varieties under controlled conditions in Northwestern Argentina

The production of tobacco (Nicotiana tabacum L.) in Argentina is centered in the northwestern region (NWA), where the incidence of root rots and stem diseases caused by Fusarium spp. has increased considerably in recent years. This study aimed to evaluate the pathogenicity levels of isolates of the F. oxysporum and F. solani complexes in different varieties of Virginia Type tobacco. The commercial varieties MB47, PVH229, NC71, K346, K326, and K394 were inoculated with six isolates of both complexes. The variables evaluated were the incidence and severity of the symptoms. The area under the disease progress curves (AUDPC) was calculated and subjected to analysis of variance (ANOVA). Also, disease epidemiological models were fitted to the experimental data. The MB47 variety was significantly less infected and the varieties K346, K326, and K394 had the highest AUDPC means, showing susceptibility to the isolates. The disease intensity curves were adequately described by the monomolecular and logistic models. The results provide, for the first time, information about the levels of tolerance to vascular wilt and root rot under controlled conditions for the main varieties of Virginia-type tobacco grown in NWA. Highlights: FOSC isolates produced mainly wilting, chlorosis, and growth reduction in tobacco plants; in contrast, FSSC isolates caused root rot, with characteristic necrotic lesions and root rot symptoms. The highest DSI scores were registered for Fo27 and Fo15, while the lowest DSI score was found for Fs98. The results obtained from the DSI scores were related to the mean AUDPC values of the isolates. MB47 and NC71 were significantly less infected than the other varieties, which registered low AUDPC values.

First report of Xanthomonas campestris pv. campestris as the causal agent of necrotic leaf spot in Phaseolus vulgaris at Puebla, Mexico.

Beans are the most cultivated legume in the world. In Mexico, it is the second most important crop after corn (FAO 2020; SIAP 2020). Bean plants "Flor de Mayo M38" variety were affected by a foliar disease during the agricultural cycle 2019 in Puebla-Mexico (19°02'46.6" LN and 98°05'15.6" LO). Necrotic V- shaped lesions were observed on the margins of the leaves surrounded by yellow halos followed by foliar necrosis, affecting 40% of the crop. In Mexico this variety of cultivars is in great demand for local consumption and generates income in foreign currency (Castellanos et al. 1997). Sampling was carried out on 50 plants "Flor de Mayo M38" variety, with necrotic leaf symptoms from ten plots of one hectare. Samples were cut into pieces (5 mm), disinfested with 1% hypochlorite 3 min, and washed with sterile distilled water. Subsequently, samples were dried on sterile paper and placed on Petri plates containing yeast extract calcium carbonate dextrose agar (YDC) medium and kept at 36°C for 3 days. Colonies of ten typical bacteria isolated from all symptomatic plants were Gram (-), small and uniform in size with rounded edges, yellow, convex with entire borders and mucoid appearance on YDC. Bacteria did not grow on 0.1% triphenyl tetrazolium chloride amended casamino acid, peptone, and glucose medium (CPG). Biochemical tests showed that isolates did not reduce nitrate to nitrites, had positive catalase and starch hydrolysis, while the Kovac oxidase test was negative (Schaad and White 1974). Genus identity of the representative isolate Xcf1-APJR, was confirmed by 16S rRNA encoding gene partial sequencing, using universal primers 518F (5'-CCAGCAGCCGCGGTAATACG-3') and 800R (5'-TACCAGGGTATCTAATCC-3') (Halim et al. 2020). BLASTn alignments against the nucleotide collection were 100% identical to Xanthomonas sequences including Xanthomonas campestris pv. campestris strains NZ_AP019684.1, CP025750.1, and MN108237.1. The 1,418 bp sequence was deposited in the GenBank database under accession number MT645246. The identification of species/pathovar was accomplished by serological methods using a polyclonal antiserum specific for X. campestris pv. campestris (Popovic ́ et al. 2013) with the DAS-ELISA commercial kit (catalog number 07122C/096, LOEWE Biochemica GmbH, Germany). The pathogenicity test was carried out on 50 healthy bean plants from the "Flor de Mayo M38" variety. Bacterial culture incubated at 28°C for 48 h in YDC medium was used to prepare the bacterial suspension (108 CFU mL-1). The first two lower leaves of 30-day-old plants were inoculated by sprinkling. Ten plants sprayed with sterile distilled water were used as negative control. All plants were kept for 20 days in greenhouse at 18-26°C and relative humidity of 60%. After seven days, chlorotic lesions developed on all inoculated plants that became necrotic from 14 days after inoculation (dai). Necrotic leaf spots merged at 14 dai to form necrotic areas of more than 20 mm in diameter, reaching total necrosis of the leaf tissue at 20 dai and were similar to the symptoms observed in the field. Koch's postulates were confirmed by the reisolation of Xcf1-APJR strain, which presented the same colony morphology, partial sequence, and polyclonal specific detection. This is the first report of this pathogen causing necrotic leaf spot in beans from the "Flor de Mayo M38" variety in Puebla-Mexico. The author(s) declare no conflict of interest.

Detecting Phytophthora cinnamomi associated with dieback disease on Carya cathayensis using loop-mediated isothermal amplification.

Chinese hickory (Carya cathayensis Sarg.) is an economically and ecologically important nut plant in China. Dieback and basal stem necrosis have been observed in the plants since 2016, and its recent spread has significantly affected plant growth and nut production. Therefore, a survey was conducted to evaluate the disease incidence at five sites in Linan County, China. The highest incidence was recorded at the Tuankou site at up to 11.39% in 2019. The oomycete, Phytophthora cinnamomi, was isolated from symptomatic plant tissue and plantation soil using baiting and selective media-based detection methods and identified. Artificial infection with the representative P. cinnamomi ST402 isolate produced vertically elongated discolorations in the outer xylem and necrotic symptoms in C. cathayensis seedlings in a greenhouse trial. Molecular detections based on loop-mediated isothermal amplification (LAMP) specific to P. cinnamomi ST402 were conducted. Result indicated that LAMP detection showed a high coherence level with the baiting assays for P. cinnamomi detection in the field. This study provides the evidence of existence of high-pathogenic P. cinnamomi in the C. cathayensis plantation soil in China and the insights into a convenient tool developed for conducting field monitoring of this aggressive pathogen.

Concurrent evolution of resistance and tolerance to potato virus Y in Capsicum annuum revealed by genome-wide association.

We performed a genome‐wide association study of pepper (Capsicum annuum) tolerance to potato virus Y (PVY). For 254 pepper accessions, we estimated the tolerance to PVY as the coefficient of regression of the fresh weight (or height) of PVY‐infected and mock‐inoculated plants against within‐plant virus load. Small (strongly negative) coefficients of regression indicate low tolerance because plant biomass or growth decreases sharply as virus load increases. The tolerance level varied largely, with some pepper accessions showing no symptoms or fairly mild mosaics, whereas about half (48%) of the accessions showed necrotic symptoms. We found two adjacent single‐nucleotide polymorphisms (SNPs) at one extremity of chromosome 9 that were significantly associated with tolerance to PVY. Similarly, in three biparental pepper progenies, we showed that the induction of necrosis on PVY systemic infection segregated as a monogenic trait determined by a locus on chromosome 9. Our results also demonstrate the existence of a negative correlation between resistance and tolerance among the cultivated pepper accessions at both the phenotypic and genetic levels. By comparing the distributions of the tolerance‐associated SNP alleles and previously identified PVY resistance‐associated SNP alleles, we showed that cultivated pepper accessions possess favourable alleles for both resistance and tolerance less frequently than expected under random associations, while the minority of wild pepper accessions frequently combined resistance and tolerance alleles. This divergent evolution of PVY resistance and tolerance could be related to pepper domestication or farmer's selection.

First Report of Leaf Blight of Adenophora triphylla var. japonica caused by Pseudomonas viridiflava in Korea.

Severe disease with leaf spots and necrotic symptoms were observed in Adenophora triphylla var. japonica (Regel) Hara (A. triphylla) during the survey in July 2020 on a field in Andong, Gyeongbuk province, Korea. It is a highly valued medicinal plant used to treat various diseases, including cough, cancer, and obesity. The infected plants initially showed spots with halo lesions, at later stages, enlarged and spread to the leaves, which the lesions becoming yellowing and chlorotic (Fig. 1). In some areas, disease incidence was up to 15% of the plants. The symptomatic samples were collected from A. triphylla and cut into 4 to 5 mm squares, surface-sterilized in 1% sodium hypochlorite for 1 min, rinsed three times, and macerated in sterile distilled water (SDW). They were spread onto nutrient agar (NA) plates and incubated at 28°C for 3 days. The representative bacterial strains selected for identification showed fluorescent colonies on King's medium B (KB). Fifteen isolates from independent samples were subjected to biochemical and pathogenicity tests. The isolates induced a hypersensitive reaction in tobacco leaves, gave a reaction in the anaerobe respiratory test, and were negative for levan, oxidase, arginine dihydrolase, gelatin hydrolysis, aesculin hydrolysis, and starch hydrolysis. The isolated strains presented the following LOPAT profile: - - + - +. The Biolog GN2 microplate and the Release 4.20 system putatively found the isolate to exhibit 93% similarity with the bacterium, Pseudomonas viridiflava. Likewise, analysis of FAME profiles using the Microbial identification system (Sherlock version 3.1) also characterized the representative bacterial strain as P. viridiflava with 87% similarity. The genomic DNA of the isolate was extracted, and the 16S rDNA sequence was amplified with a universal bacterial primer set (27F and 1492R). The sequence was submitted to GenBank under the accession number MT975233. BLASTn analysis yielded 99.79% identity with P. viridiflava strain RT228.1b (accession no. AY604846.1) and 99.72% similarity with P. viridiflava KNOX249.1b strain (accession no. AY604848.1). Phylogenetic dendrogram constructed from the comparative analysis of 16S rDNA gene sequences showing the relationship between P. viridiflava GYUN274 and related Pseudomonas species (Fig. 2). Pathogenicity tests were conducted three times on seedling of A. triphylla by spraying 50 ml of bacterial suspensions of a 24-h culture in KB medium (108 CFU/ml). The leaves inoculated with SDW alone did not develop symptoms; however, the plants treated with isolated bacterial suspensions developed halo and blight symptoms similar to those observed in the field 7 days post-inoculation. Finally, Koch's postulates were verified by re-isolating P. viridiflava from all symptomatic tissues and determined to be morphologically identical to the original isolates. To our knowledge, this is the first report of leaf blight disease of A. triphylla caused by P. viridiflava in Korea. Based on the observed symptoms, and identification by morphological characteristics, molecular data, and pathogenicity against the host plant, the proper control measures can be identified in future studies.

Identification of a bio-signature for barley resistance against Pyrenophora teres infection based on physiological, molecular and sensor-based phenotyping

Necrotic and chlorotic symptoms induced during Pyrenophora teres infection in barley leaves indicate a compatible interaction that allows the hemi-biotrophic fungus Pyrenophora teres to colonise the host. However, it is unexplored how this fungus affects the physiological responses of resistant and susceptible cultivars during infection. To assess the degree of resistance in four different cultivars, we quantified visible symptoms and fungal DNA and performed expression analyses of genes involved in plant defence and ROS scavenging. To obtain insight into the interaction between fungus and host, we determined the activity of 19 key enzymes of carbohydrate and antioxidant metabolism. The pathogen impact was also phenotyped non-invasively by sensor-based multireflectance and –fluorescence imaging.Symptoms, regulation of stress-related genes and pathogen DNA content distinguished the cultivar Guld as being resistant. Severity of net blotch symptoms was also strongly correlated with the dynamics of enzyme activities already within the first day of infection. In contrast to the resistant cultivar, the three susceptible cultivars showed a higher reflectance over seven spectral bands and higher fluorescence intensities at specific excitation wavelengths. The combination of semi high-throughput physiological and molecular analyses with non-invasive phenotyping enabled the identification of bio-signatures that discriminates the resistant from susceptible cultivars.

Indigenous fungi from corn as a potential plant growth promoter and its role in Fusarium verticillioides suppression on corn

Indigenous fungi can suppress infection by pathogens and produce secondary metabolites that directly or indirectly affect plant growth. This study aimed to test indigenous fungi collected from corn plants as biological control agents and their effects on the viability and vigor of corn seeds. Purposive sampling method was used for sampling where soil samples taken from the rhizosphere zone, corn stem and leaf tissue from three locations namely Maros-South Sulawesi, Bone-South Sulawesi, Sigi-Central Sulawesi, Indonesia. Rhizospheric fungi were isolated from soil collected at the rhizosphere and rhizoplane using a serial dilution technique, while the endophytic fungi isolated from the leaves and stem tissues using surface sterilization method. The isolated fungi were cultured on a potato dextrose agar (PDA) medium. An antagonism test was performed using the dual culture method on PDA media with F. verticillioides as target pathogen. Pathogenicity test and the effect of fungi on corn seed germination was carried out using the blotter test method. Parameters observed were; necrotic symptoms on seedlings, growth potential, germination, growth rate, growth simultaneity, vigor index, germination rate, and time needed for 50% of the total germination. The effect of the isolated indigenous fungi on corn growth was carried out in-planta using seedling trays. The results of the blotter test and in-planta test were further confirmed by a physiological characteristic test. And assessing the fungi's ability to dissolve potassium, phosphate, and produce protease enzymes. A total of 89 fungal isolates were isolated and collected from various parts of the corn plant. Nineteen of the 89 fungal isolates showed inhibitory activity against F. verticillioides by ≥ 50% inhibition. The fungal isolates JRP 5 MRS, JRP 9 MRS, JRP 10 MRS, JRP 7 MRS, and JEDF 1B BN were selected based on the tests and showed a consistently positive effect on seed viability and vigor with a value of ≥90%. The isolates did not cause necrosis in corn, and had the ability to suppress the growth of pathogenic F. verticillioides by ≥ 50%.

Molecular and Biological Characterization of Recombinant Isolates of Potato virus Y Circulating in Potato Fields in Mexico.

Potato virus Y (PVY) is a significant threat to potato (Solanum tuberosum) production in Mexico. The presence of recombinant strains of PVY circulating in potato has been reported in the country, but no systematic study on the genetic diversity of PVY in potato and prevalence of PVY strains has been conducted yet. We report on a series of surveys in seed potato production areas in two states in Mexico, namely, Chihuahua and Jalisco, between 2011 and 2019. PVY was detected through the period of nine years in multiple potato cultivars in both states, often remaining asymptomatic in the most popular cultivars, such as 'Fianna' and 'Agata'. When typed to strain, all PVY samples studied were found to have N-serotype, and were all identified molecularly as isolates of the same recombinant strain, PVYNTN. Five of these PVY isolates were tested on tobacco (Nicotiana tabacum), where they induced vein necrosis supporting the molecular typing. This identification was also confirmed biologically on differential potato cultivars, where one PVYNTN isolate from the 2013 survey triggered the hypersensitive resistance conferred by the Nztbr gene in the cv. Maris Bard. Seven of these Mexican PVYNTN isolates, collected between 2013 and 2019, including two PVY isolates from potato tubers exhibiting potato tuber necrotic ringspot disease, were subjected to whole genome sequencing and found to show a typical PVYNTNa recombinant structure. When subjected to phylogenetic analysis, Mexican PVYNTN sequences clustered in more than three separate clades, suggesting multiple introductions of PVYNTN in the country. The wide circulation of the PVYNTN strain in Mexican potato should be considered by potato producers, to develop mitigation strategies for this PVY strain associated with tuber necrotic symptoms.

New evidence of arsenic translocation and accumulation in Pteris vittata from real-time imaging using positron-emitting 74As tracer

Pteris vittata is an arsenic (As) hyperaccumulator plant that accumulates a large amount of As into fronds and rhizomes (around 16,000 mg/kg in both after 16 weeks hydroponic cultivation with 30 mg/L arsenate). However, the sequence of long-distance transport of As in this hyperaccumulator plant is unclear. In this study, we used a positron-emitting tracer imaging system (PETIS) for the first time to obtain noninvasive serial images of As behavior in living plants with positron-emitting 74As-labeled tracer. We found that As kept accumulating in rhizomes as in fronds of P. vittata, whereas As was retained in roots of a non-accumulator plant Arabidopsis thaliana. Autoradiograph results of As distribution in P. vittata showed that with low As exposure, As was predominantly accumulated in young fronds and the midrib and rachis of mature fronds. Under high As exposure, As accumulation shifted from young fronds to mature fronds, especially in the margin of pinna, which resulted in necrotic symptoms, turning the marginal color to gray and then brown. Our results indicated that the function of rhizomes in P. vittata was As accumulation and the regulation of As translocation to the mature fronds to protect the young fronds under high As exposure.

Potential biocontrol of endophytic fungi against Lasiodiplodia pseudotheobromae causal agent of cocoa dieback on cocoa seedling

Endophytic fungi associated with cocoa are one of the effective agents to control plant pathogens on cocoa, including the fungus Lasiodiplodia pseudotheobromae. L. pseudotheobromae cause a significant disease on cocoa, cocoa dieback. The disease is considered an emerged disease on cocoa in Sulawesi, Indonesia. The research aimed to determine the effect of the endophytic fungi on L. pseudotheobromae on cocoa seedlings. This study used a randomized block design consisting of 6 treatments and 3 replications. Five different fungi isolates were used that belong to Aspergillus genera. The treatment is three isolates of endophytes fungi (isolate T2S2LT, T245LT, T645LT), Aspergillus isolates combination, and control (with and without pathogen). The results showed that the combination of isolates and T645LT isolate was the best treatment for suppressing necrotic symptoms (leaf spot) incidence and severity. Also, T645LT isolate performed well to inhibit leaf blight symptoms incidence severity. Meanwhile, the chlorotic symptom was reduced by isolates combination, followed by T2S2LT, T645LT, and T245LT. Endophytic fungi can potentially be an important option to control cocoa dieback disease.

Physiological and mineralogical properties of arsenic stressed oat seedlings grown hydroponically

To determine arsenic (As) phytotoxicity in gramineae, a hydroponic experiment with oat was conducted. Twenty-four days old oat seedlings were treated with sodium meta-arsenite (NaAsO2) for 14 days at different rates of As in the greenhouse. Shoot growth decreased by 28.17, 38.34, 68.34, and 75.85%, while the root growth decreased by 33.51, 42.61, 64.79, and 72.15% for 6.7, 13.4, 26.8, and 53.6 µM As treatments, respectively, indicating that the roots were more sensitive to As-toxicity than that of shoots. Arsenic at the rate of 13.4 µM level produced chlorotic symptom in the 4th leaf. Necrotic symptom was found in the old leaves at 26.8 and 53.6 µM As levels. Arsenic concentration increased both in shoots and roots with the increasing As concentration in the solution. Mostly, the concentrations of P, Fe, and Zn decreased in shoots. On the contrary, As and Fe concentrations increased in roots with the increasing As concentration in the solution. The research suggested that As hindered Fe translocation from roots to the shoots, resulting in whitish chlorotic symptom in the leaves.

In Vitro Antimicrobial Activity of Cinnabarin on Xanthomonas campestris Isolated from Bean Crops of Puebla, Mexico

Phaseolus vulgaris is the most legume cultivated in the world; in Mexico, it is considered the second most important crop after corn. The aim of this research was to determine the characteristics of Xanthomonas campestris strain “Xcf1-APJR” isolated from the leaves of bean crops, and determine the antimicrobial activity of cinnabarin on this strain. Bacterial cultures were obtained from leaves with necrotic leaf spot symptoms of bean plant variety “Flor de Mayo M38” in Puebla, Mexico. The antimicrobial activity of cinnabarin was tested at 7, 14 and 21 days on X. campestris pv. campestris. The Xcf1-APJR strain showed 100% identity with X. campestris pv. campestris as a causal agent of necrotic leaf spot. Treatment with a potato dextrose medium with a dehydrated sugar cane (PDA+C) showed a higher orange pigmentation than the other treatments after 7, 14 and 21 days of incubation and a higher concentration of cinnabarin (54.33 InU/g) with in vitro antimicrobial activity against X. campestris pv. campestris.

TaWRKY10 transcription factor is a novel jasmonic acid signalling regulator involved in immunity against Septoria tritici blotch disease in wheat

Septoria tritici blotch (STB), caused by the fungus Zymoseptoria tritici, is currently the main threat to worldwide wheat production in temperate climates. Understanding the genetic mechanisms that underpin the Z. tritici–wheat interaction will be crucial for generating new control strategies against STB. Plant hormones are essential regulators of growth and immunity. In particular, jasmonic acid (JA) plays a central role in defence against necrotrophic plant pathogens, but its role in mediating immunity against Z. tritici is largely unknown. Here we identify the transcription factor TaWRKY10 that is taxonomically restricted to the grass subfamily Pooideae as a novel regulator of JA responses in wheat. We demonstrate by using virus‐induced gene silencing that silencing TaWRKY10 leads to increased resistance against Z. tritici with an earlier onset of necrotic symptoms, but with reduced pathogen sporulation. Wheat plants silenced for TaWRKY10 show an up‐regulated JA response. Transcriptional profiling of TaWRKY10 knock‐down plants indicates that it is a negative regulator of the JA receptor TaCOI1 gene expression. Our data indicate that TaWRKY10 down‐regulates JA responses, contributing to the susceptibility of wheat to Z. tritici. We postulate that manipulating TaWRKY10 may provide a strategy to boost STB resistance in wheat.

Identification and characterization of Klebsiella oxytoca strains associated with wetwood disease of Morus trees

The Morus plants with a wide range of features and properties are widely used for their edible fruits, medicinal and other ornamental purposes worldwide. In summer and spring of 2016, a wetwood disease was observed on Morus trees (Black mulberry, White mulberry and Red mulberry), in municipal lands and parks of Rafsanjan city (Kerman Province), Iran. Typical symptoms were wetwood symptoms characterized by canker, stem weeping and liquid exudates on trunk of infected trees. The causative agent of wetwood disease from the infected samples was identified as Klebsiella oxytoca based on its biochemical and phenotypic feature and confirmed using sequence analysis of atpD gene. Artificial inoculation of the isolated bacterial strain (predominant) on 1-year-old mulberry seedlings produced the necrotic symptoms on the inner bark of seedlings. To fulfill Koch’s postulates, the same bacteria were re-isolated from the diseased tissues and identified as Klebsiella based on colony morphology, phenotypic, and biochemical tests. Here, we described the characteristics of K. oxytoca strains as the causal agent of wetwood disease of Red mulberry (Morus rubra), White mulberry (Morus alba), and Black mulberry (Morus nigra) for the first time.

In Vitro Conservation of Medicinal Plant St. John’s Wort (Hypericum perforatum L.) Through Dilution of Basic Medium

In vitro techniques could be applied for plant conservation through minimal growth. Growth reduction is generally attained by modifying the culture medium and/or the environmental condition. Conservation of St. John’s wort (Hypericum perforatum L.) in vitro through dilution of basic medium was conducted at the Tissue Culture Laboratory of Indonesian Spice and Medicinal Crops Research Institute (ISMCRI) in 2018. Sterile shoots were cultured into Murashige and Skoog (MS) medium by reducing macronutrients. The treatments used were full-MS + 0.1 mg L-1 N6 - benzyladenine (BA) as control; ¾ MS + 0.1 mg L-1 BA; ½ MS + 0.1 mgL-1 BA and ¼ MS + 0.1 mg L-1 BA. Observation of the culture growth was conducted three months after the treatments. The experiment was arranged in Completely Randomized Design with ten replications. The result showed that the use of a dilution of basic medium affected the growth of St. John’s wort. The use of ¼ MS + 0.1 mg L-1 BA composition could suppress culture growth (number of shoots, shoots length and number of leaves), without showing necrotic symptom until three months of conservation. This treatment could be used as an alternative to minimize the culture of St. John’s wort for in vitro conservation.

Ultrastructure of cytopathological responses in Solanum tuberosum cv. Spounta infected with necrotic strain of potato virus Y

Ultrastructural responses of plant cell organelles in leaf tissues of potato cv. Spounta towards potato virus Y (PVY-necrotic and ordinary strains) infection were investigated using an electron microscope. Numerous cytopathological alterations in cell wall, middle lamella, nucleus, chloroplast, mitochondria, endoplasmic reticulum and peroxisomes have been observed compared to healthy tissues. Splitting, destroying, joining to neighboring protoplasts and necrosis in cell wall were observed. Cell nucleus was changed to lobe-like shape; damage in envelope and enlargement of pore complexes were observed. Mitochondria were increased in number, elongated and destroyed. Many changes in chloroplasts such as deformation, reduction in size and number, damage of envelope and grana thylakoids were observed. Virus particles and cytoplasmic inclusions were observed in ultra-thin sections. To our knowledge, obtained results showed that only peroxisomes could be responsible organelles for induction of necrotic symptoms, because they were increased in number and frequently existed only in plant cells infected with PVY-necrotic strain.

MaMAPK3-MaICE1-MaPOD P7 pathway, a positive regulator of cold tolerance in banana

BackgroundBanana is a tropical fruit with a high economic impact worldwide. Cold stress greatly affects the development and production of banana.ResultsIn the present study, we investigated the functions of MaMAPK3 and MaICE1 involved in cold tolerance of banana. The effect of RNAi of MaMAPK3 on Dajiao (Musa spp. ‘Dajiao’; ABB Group) cold tolerance was evaluated. The leaves of the MaMAPK3 RNAi transgenic plants showed wilting and severe necrotic symptoms, while the wide-type (WT) plants remained normal after cold exposure. RNAi of MaMAPK3 significantly changed the expressions of the cold-responsive genes, and the oxidoreductase activity was significantly changed in WT plants, while no changes in transgenic plants were observed. MaICE1 interacted with MaMAPK3, and the expression level of MaICE1 was significantly decreased in MaMAPK3 RNAi transgenic plants. Over-expression of MaICE1 in Cavendish banana (Musa spp. AAA group) indicated that the cold resistance of transgenic plants was superior to that of the WT plants. The POD P7 gene was significantly up-regulated in MaICE1-overexpressing transgenic plants compared with WT plants, and the POD P7 was proved to interact with MaICE1.ConclusionsTaken together, our work provided new and solid evidence that MaMAPK3-MaICE1-MaPOD P7 pathway positively improved the cold tolerance in monocotyledon banana, shedding light on molecular breeding for the cold-tolerant banana or other agricultural species.