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16 pages, 10041 KiB

Open AccessEditor’s ChoiceArticle

Pseudomonas fluorescens RB5 as a Biocontrol Strain for Controlling Wheat Sheath Blight Caused by Rhizoctonia cerealis

by Yanjie Yi, Zhipeng Hou, Yu Shi, Changfu Zhang, Lijuan Zhu, Xinge Sun, Rumeng Zhang and Zichao Wang

Agronomy 2023, 13(8), 1986; https://doi.org/10.3390/agronomy13081986 - 27 Jul 2023

Cited by 6 | Viewed by 1404

Abstract

Wheat sheath blight is a soil-borne fungal disease caused by Rhizoctonia cerealis and is a serious threat to wheat worldwide. A microbial fungicide is a promising alternative to a chemical fungicide for wheat disease control. In this study, strain RB5 against R. cerealis [...] Read more.

Wheat sheath blight is a soil-borne fungal disease caused by Rhizoctonia cerealis and is a serious threat to wheat worldwide. A microbial fungicide is a promising alternative to a chemical fungicide for wheat disease control. In this study, strain RB5 against R. cerealis was isolated from wheat rhizosphere soil, which was identified as Pseudomonas fluorescens according to physiological, biochemical, and 16S rRNA gene sequence analyses. For improving the antifungal activity of RB5, the response surface methodology (RSM) was used to optimize the culture conditions for strain RB5, and the optimal culture conditions are 8.7 g/L of cassava, 5.2 g/L of soybean meal, pH 6.8, a 218 r/min speed, a 31.5 °C temperature, and 54 h of culture time. The inhibition rate of the culture filtrate obtained under this culture condition was up to 79.06%. The investigation of action mechanism showed strain RB5 could produce protease, chitinase, and siderophore, and its culture filtrate disrupted the mycelial morphology and inhibited the activities of three cell-wall-degrading enzymes of R. cerealis. Furthermore, the pot experiment exhibited that RB5 significantly controlled the wheat sheath blight with an efficacy of 71.22%. The evaluation of toxicological safety on an animal indicated that the culture filtrate was safe on mice. Overall, the culture filtrate of RB5 is a very promising microbial fungicide for the control of wheat sheath blight. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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20 pages, 632 KiB

Open AccessArticle

Effect of Different Foliar Fertilizer Applications on Esca Disease of Grapevine: Symptom Expression and Nutrient Content in the Leaf and Composition of the Berry

by Francesco Calzarano, Carmine Amalfitano, Leonardo Seghetti and Stefano Di Marco

Agronomy 2023, 13(5), 1355; https://doi.org/10.3390/agronomy13051355 - 12 May 2023

Cited by 1 | Viewed by 1693

Abstract

Esca disease, the most common grapevine wood disease in Europe, causes yield losses correlated with the foliar symptoms’ expression. In two vineyards located in the Abruzzo Region of Italy, each of which were investigated for esca symptoms after 1994, different applications of macro- [...] Read more.

Esca disease, the most common grapevine wood disease in Europe, causes yield losses correlated with the foliar symptoms’ expression. In two vineyards located in the Abruzzo Region of Italy, each of which were investigated for esca symptoms after 1994, different applications of macro- and microelements were performed in two consecutive growing seasons. The main aim of the work consisted of verifying the effects of the fertilizer applications on the foliar symptoms’ expression, in order to deepen knowledge of the nature of the symptom, which is still unclear. For each treatment, in each year, the leaf content of macro- and microelements and the composition of berries and musts were assessed. The effects of these applications on vegetative growth and yield quantity were also verified. The trials were carried out on symptomatic, asymptomatic and apparently healthy vines. All applications, in particular those with microelements, increased the foliar symptoms’ expression, and a greater vegetative growth was detected only in vines treated with NPK fertilizers. The symptoms’ increase was always associated in the leaf with a decrease of calcium, and to a lesser extent, magnesium, reinforcing the hypothesis of the plant’s hypersensitive reaction in the development of foliar symptoms, given the role of calcium in the defense response. The vineyards were in nutritional balance regardless of the fertilizer applications. The general increase in foliar symptoms and the decrease in sugars in the musts of asymptomatic treated vines underlined the importance of the vegetative-productive balance, in Esca infected vineyards especially, in order to limit the symptoms’ expression and the decrease in yield. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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13 pages, 3049 KiB

Open AccessArticle

Thymol Induces Cell Death of Fusarium oxysporum f. sp. niveum via Triggering Superoxide Radical Accumulation and Oxidative Injury In Vitro

by Yini Hao, Jiao Zhang, Changwei Sun, Xuenai Chen, Yuxiao Wang, Haiyan Lu, Jian Chen, Zhiqi Shi, Li Zhang, Lifei Yang and Sijie Huang

Agronomy 2023, 13(1), 189; https://doi.org/10.3390/agronomy13010189 - 6 Jan 2023

Cited by 6 | Viewed by 2512

Abstract

Fusarium oxysporum f. sp. niveum (FON) causes watermelon wilt that is one of the major disease-causing yield losses of watermelon. Sustainable development of agriculture requires controlling watermelon wilt disease with good environmental performance. One important approach is to identify environmental-friendly compounds [...] Read more.

Fusarium oxysporum f. sp. niveum (FON) causes watermelon wilt that is one of the major disease-causing yield losses of watermelon. Sustainable development of agriculture requires controlling watermelon wilt disease with good environmental performance. One important approach is to identify environmental-friendly compounds with inhibitory activity against FON. Thymol is a plant-derived compound that is safe for ecology. Little is known about the application of thymol in agriculture. In this study, we studied the inhibitory activity of thymol against FON by using morphological, physiological, and histochemical approaches. Thymol significantly inhibited colony diameter of FON in a dose-dependent manner, with EC₅₀ at 21 µg/mL. Thymol at 10, 21, and 35 µg/mL decreased the fresh weight of FON mycelia by 29.0%, 50.6%, and 69.5%, respectively. Microscopic observation revealed irregular damage and loss of shape of mycelia upon thymol exposure. Thymol induced the accumulation of superoxide radical in mycelial cells and accompanied increased activity of antioxidative enzymes (SOD, superoxide dismutase; CAT, catalase). Thymol induced membrane permeability was indicated by lipid peroxidation and electrolyte leakage (increased by 29–58%) in mycelial cells. These results suggested that thymol induced oxidative damage in mycelia, which may be one of the possible reasons for thymol-induced mycelial cell death observed with fluorescent detection. Thymol decreased the production of conidia and inhibited the germination of conidia. Thymol induced superoxide radical accumulation, lipid peroxidation, and cell death in conidia as well. All of these results revealed the inhibitory activity of thymol against FON, which may have resulted from the superoxide radical-induced oxidative injury in both conidia and mycelia of FON. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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13 pages, 2227 KiB

Open AccessArticle

Molecular Detection and Analysis of Blast Resistance Genes in Rice Main Varieties in Jiangsu Province, China

by Zhongqiang Qi, Yan Du, Junjie Yu, Rongsheng Zhang, Mina Yu, Huijuan Cao, Tianqiao Song, Xiayan Pan, Dong Liang and Yongfeng Liu

Agronomy 2023, 13(1), 157; https://doi.org/10.3390/agronomy13010157 - 3 Jan 2023

Cited by 7 | Viewed by 2534

Abstract

Rice blast, caused by Pyricularia oryzae, is one of the most destructive rice diseases worldwide. Using resistant rice varieties is the most cost-effective way to control the disease, and it is crucial to analyze the resistance level and the resistance genes distribution [...] Read more.

Rice blast, caused by Pyricularia oryzae, is one of the most destructive rice diseases worldwide. Using resistant rice varieties is the most cost-effective way to control the disease, and it is crucial to analyze the resistance level and the resistance genes distribution of the main varieties. In this study, we collected 119 rice main varieties in Jiangsu province and evaluated the resistance to leaf and panicle blast and found that indica rice was more resistant to rice blast than japonica rice. Moreover, we detected the distribution of 14 resistance genes (R genes) in the 119 varieties. The distribution frequencies of three R genes, Pish, Pit, and Pia, were higher than 80%, and the Pigm had the lowest distribution frequency (1.68%), followed by Pi2 (15.18%) and Pi5, Piz-t (24.37%). Combined with the multiple stepwise regression and the resistance contribution rate, eight major R genes Pita, Pi5, Pi9, Pib, Pb1, Pikm, Piz-t, and Pi2 significantly affected the resistance of rice, and we also found that six gene combinations with 100% resistance contribution rate could effectively increase the resistance of rice varieties. In summary, monitoring the resistance level of rice varieties and analyzing their resistance genes were beneficial for rice resistance breeding. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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12 pages, 21927 KiB

Open AccessArticle

Nano-Thymol Emulsion Inhibits Botrytis cinerea to Control Postharvest Gray Mold on Tomato Fruit

by Jiao Zhang, Yini Hao, Haiyan Lu, Pan Li, Jian Chen, Zhiqi Shi, Yuhua Xie, Haizhen Mo and Liangbin Hu

Agronomy 2022, 12(12), 2973; https://doi.org/10.3390/agronomy12122973 - 26 Nov 2022

Cited by 14 | Viewed by 2287

Abstract

Thymol is a plant-derived natural compound with antimicrobial activity. However, we have little knowledge about the application of thymol in agriculture. One of the limitations is the high volatility and low aqueous solubility of thymol. Tomato gray mold caused by Botrytis cinerea is [...] Read more.

Thymol is a plant-derived natural compound with antimicrobial activity. However, we have little knowledge about the application of thymol in agriculture. One of the limitations is the high volatility and low aqueous solubility of thymol. Tomato gray mold caused by Botrytis cinerea is one of the most devastating postharvest diseases. In this study, we prepared a nano-emulsion of thymol (named as Nano-Thy) to form a stable O/W (oil in water) microemulsion. In vitro experiments showed that Nano-Thy had antifungal activity against B. cinerea by inhibiting mycelial growth and spore germination. Nano-Thy induced ROS accumulation in mycelia, further leading to lipid peroxidation, cell membrane damage, and subsequent cell death. Nano-Thy significantly prevented the infection of B. cinerea on fresh tomato fruits. Finally, we discussed the mechanisms and their significance in controlling postharvest disease of fruit crops. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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15 pages, 3670 KiB

Open AccessArticle

Pyrroloquinoline Quinone Treatment Induces Rice Resistance to Sheath Blight through Jasmonic Acid Pathway

by Sifu Li, Tao Tang, Guolan Ma, Ducai Liu, Yajun Peng and Yuzhu Zhang

Agronomy 2022, 12(11), 2660; https://doi.org/10.3390/agronomy12112660 - 27 Oct 2022

Cited by 3 | Viewed by 2037

Abstract

Using bioactive inducers to enhance rice resistance is an effective means of green prevention and control of diseases during rice production. In a previous study, we found that foliar sprays of pyrroloquinoline quinone (PQQ) as the bioactive inducer could remarkably reduce the occurrence [...] Read more.

Using bioactive inducers to enhance rice resistance is an effective means of green prevention and control of diseases during rice production. In a previous study, we found that foliar sprays of pyrroloquinoline quinone (PQQ) as the bioactive inducer could remarkably reduce the occurrence index of rice sheath blight (ShB) Rhizoctonia solani and increase the grain yield of rice under field conditions. However, little information is available on the mechanism of PQQ-induced rice resistance to ShB. In this study, the phenotype and mechanism of foliar sprayed PQQ-induced rice resistance to ShB were investigated by artificial inoculation method, RNA-seq technology, and quantitative real-time PCR (qRT-PCR) assay in the laboratory. The results showed that at 144 h after inoculation (hai) with the ShB C30 strain, many disease spots occurred obviously in a susceptible variety, Lemont (L), treated by 1.0 μmol/L PQQ (P+) with the disease score (DS) of 4.36, and almost all plants were withered and died under the ddH₂O (P−) treatment alone, with the DS of 8.39. By comparison, the DS of a resistant variety, Gaopin 6 (G), was only 0.88 in the P+ treatment and 3.82 in the P− treatment. The results of hormone determination showed that jasmonic acid (JA) contents in the G and L varieties treated by P+ were increased significantly, by 78% and 197% respectively, at 48 hai. There was no significant difference in salicylic acid (SA) contents in these varieties between P+ and ddH₂O (P−) treatments during the period of 48 hai. These results suggest that JA may play a key role in PQQ-induced rice resistance to ShB. The transcriptome analysis of the leaf sheath of the G and L varieties indicated that 165 and 250 differentially expressed genes (DEGs) were found in the intersection of LP− vs. LP+ and GP− vs. GP+ at 24 and 48 hai, respectively. Kyoto encyclopedia of genes and genomes analysis showed that these DEGs were related to plant–pathogen interaction, ribosome, plant hormone signaling transduction, mitogen-activated protein kinas signaling pathway, and phenylpropanoid biosynthesis. For ten highly expressed genes related to disease resistance, the results of qRT-PCR assay showed that eight genes, especially OsAOS2 and OsOSM1, were regulated positively, and two genes, OsGF14e and OsWRKY72, were regulated negatively. Among these, four up-regulated genes, OsOSM1, OsAOS2, OsHI-LOX, and OsLOX1, and one down-regulated gene, OsWRKY72, belonging to the JA signaling pathway, may be involved in PQQ-induced rice resistance to ShB. These results provide valuable information for green prevention and control of ShB by PQQ foliar spraying in the field. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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15 pages, 2374 KiB

Open AccessArticle

A Genome-Wide Alternative Splicing Landscape Specifically Associated with Durable Rice Blast Resistance

by Dong Liang, Junjie Yu, Tianqiao Song, Rongsheng Zhang, Yan Du, Mina Yu, Huijuan Cao, Xiayan Pan, Junqing Qiao, Youzhou Liu, Zhongqiang Qi and Yongfeng Liu

Agronomy 2022, 12(10), 2414; https://doi.org/10.3390/agronomy12102414 - 5 Oct 2022

Cited by 3 | Viewed by 1724

Abstract

The rice blast, caused by the hemibiotrophic plant pathogen Magnaporthe oryzae, is a devastating disease that threatens rice crop production worldwide. The molecular interactions that underlie the rice-M. oryzae interaction have received much attention. However, genome-wide research focusing on alternative splicing [...] Read more.

The rice blast, caused by the hemibiotrophic plant pathogen Magnaporthe oryzae, is a devastating disease that threatens rice crop production worldwide. The molecular interactions that underlie the rice-M. oryzae interaction have received much attention. However, genome-wide research focusing on alternative splicing (AS) has not been well-studied in rice—M. oryzae interactions. AS in plants leads to diverse proteomes without an expansion in gene numbers to regulate cellular processes during abiotic or biotic stress. The Pi21 gene negatively regulates rice resistance to M. oryzae infection, and thus the Pi21-RNAi silenced transgenic line (#241) exhibits partial but durable resistance. We compared the AS landscape in #241 and “Nipponbare” (Nip) during interacting with M. oryzae Guy11, and the alternative 3′ splice-site (A3SS) is the most common AS type. GO enrichment analysis of #241-specific differentially alternatively spliced genes (DASGs) revealed that WRKY transcription factors (TFs), bHLH TFs, F-box protein with leucine rich repeats, AAA-type ATPase, and protein kinase were enriched in the GO terms “response to jasmonate acid (JA)” and “ethylene (ET)” at 24 h post-inoculation (hpi). At 48 hpi, one #241-specific DASG, ubiquitin gene (Os08g0295000), was predicted to be involved in endoplasmic reticulum (ER) stress. In silico analysis combined with PCR amplification confirmed that multiple isoforms are produced by Os08g0295000 and a skipped exon (SE) event results in isoform switching during interaction with M. oryzae. Protein–protein interaction (PPI) network analysis predicted that Os08g0295000-encoding proteins may interact with SNARE protein Q9LGF8 (Uniprot ID) to cooperatively regulate rice’s response to M. oryzae. This study uncovered the AS profile of rice in response to M. oryzae, which will help to explore the linkage between AS and durable rice resistance. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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9 pages, 254 KiB

Open AccessArticle

The Effect of Selenium Foliar Application on the Physiological Responses of Edamame under Different Water Treatments

by Makoena Joyce Moloi and Bongiwe Minah Khoza

Agronomy 2022, 12(10), 2400; https://doi.org/10.3390/agronomy12102400 - 4 Oct 2022

Cited by 7 | Viewed by 1857

Abstract

Drought has devastating effects on crops, posing enormous risks to food security. This study investigated the impact of foliar applied selenium [at four concentrations (25, 50 and 75 mg/L)] on the photosynthesis capacity, antioxidative enzyme activities [ascorbate peroxidase (APX) and guaiacol peroxidase (GPX)] [...] Read more.

Drought has devastating effects on crops, posing enormous risks to food security. This study investigated the impact of foliar applied selenium [at four concentrations (25, 50 and 75 mg/L)] on the photosynthesis capacity, antioxidative enzyme activities [ascorbate peroxidase (APX) and guaiacol peroxidase (GPX)] and yield parameters of a drought susceptible edamame under optimal watering and drought-stressed conditions. The study was conducted in the greenhouse under controlled conditions with leaf sampling done at vegetative, flowering and pod filling stages. Treatment of drought-stressed plants with selenium selectively induced PIabs and chlorophyll content at the vegetative stage. Ascorbate peroxidase was the only parameter induced at the flowering stage by selenium under drought stress. Selenium had no effect on all parameters under drought stress at pod filling, suggesting that the efficacy of selenium declines with time. In addition, yield parameters were not substantially affected by selenium under drought stress. Although selenium was effective for selected parameters, the application should only be limited to edamame growing under drought stress because, under well-watered conditions, it had negative impacts. Future studies should explore the responses drought stressed edamame after secondary application of selenium (i.e., at vegetative, flowering and pod filling). Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

16 pages, 6898 KiB

Open AccessArticle

Bioactivity of Ethanolic Extracts of Dipteryx punctata on Colletotrichum musae

by Bruna Cristine Martins de Sousa, Daniel do Amaral Gomes, Thiago Almeida Vieira and Denise Castro Lustosa

Agronomy 2022, 12(9), 2215; https://doi.org/10.3390/agronomy12092215 - 17 Sep 2022

Cited by 2 | Viewed by 2406

Abstract

Bioactivity with antifungal properties has already been reported for some species of the genus Dipteryx. However, little is known about Dipteryx punctata. We evaluated the antifungal activity, in vitro and in vivo, of extracts of leaves, branches and fruits of D. [...] Read more.

Bioactivity with antifungal properties has already been reported for some species of the genus Dipteryx. However, little is known about Dipteryx punctata. We evaluated the antifungal activity, in vitro and in vivo, of extracts of leaves, branches and fruits of D. punctata on Colletotrichum musae, the causal agent of anthracnose in bananas. The extracts and the coumarin standard were tested in vitro, at concentrations of 10%, 20%, 30%, 40%, and 50% (w/v), added in potato-dextrose-agar (PDA) medium. The experimental design was completely randomized, factorial design, with four replications. The average diameter of the fungal colonies was evaluated daily for eight days, and at the end, the percentage of inhibition and growth rates were calculated. For in vivo tests, the products were tested at concentrations of 40% and 50%, in preventive and curative applications. In these tests, three medium disks (5 mm) containing phytopathogen structures were deposited at opposite points of the fruits, and remained in a humid chamber for 48 h. Anthracnose lesions were measured at an interval of two days, up to eight days after fungus inoculation. In the in vitro essay, the extracts of the branches and residues of the fruits of D. punctata and the coumarin pattern caused the biggest reductions in the average diameter of the colonies of the phytopathogen. D. punctata and coumarin extracts were promising in terms of in vivo antifungal activity, especially in preventive applications, being an important source of investigation for the formulation of natural products as sustainable phytosanitary measures. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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13 pages, 3438 KiB

Open AccessArticle

The Sodium/Calcium Exchanger PcNCX1-Mediated Ca²⁺ Efflux Is Involved in Cinnamaldehyde-Induced Cell-Wall Defects of Phytophthora capsici

by Zhongqiang Qi, Lina Li, Cunfa Xu, Muxing Liu, Yousheng Wang, Li Zhang, Jian Chen, Haiyan Lu and Zhiqi Shi

Agronomy 2022, 12(8), 1763; https://doi.org/10.3390/agronomy12081763 - 27 Jul 2022

Cited by 2 | Viewed by 1876

Abstract

Phytophthora capsici is one of the devastating pathogens, causing foliar blight, root rot, and fruit rot in peppers. Cinnamaldehyde (CA) is a natural compound coming from Cinnamomum cassia. The medicinal properties of CA have been widely identified. Limited knowledge is known about [...] Read more.

Phytophthora capsici is one of the devastating pathogens, causing foliar blight, root rot, and fruit rot in peppers. Cinnamaldehyde (CA) is a natural compound coming from Cinnamomum cassia. The medicinal properties of CA have been widely identified. Limited knowledge is known about the application of CA in agriculture. In this study, CA significantly inhibited P. capsici, which further suppressed Phytophthora blights in both pepper seedlings and pepper fruits. Treatment with CA resulted in collapsed and fragmented hyphae, accompanying the increase in MDA (malondialdehyde) content and the decrease in intercellular glycerol content in hyphae. CA also inhibited the growth of wild type yeast. The yeast mutant ΔYvc1 with a deletion of Yvc1 (a Ca²⁺ transporter) showed decreased sensitivity to CA. The transformation of PcNCX1, a sodium/calcium exchanger from P. capsici, into ΔYvc1 restored its sensitivity to CA. The transformant carrying PcNCX1 also showed restored Ca²⁺ efflux upon CA treatment. RNA-seq analysis showed that CA treatments resulted in the down-regulation of a set of genes encoding for calcium-related proteins. Collectively, our study demonstrates that the antifungal activity of CA against P. capsici may be associated with PcNCX1-mediated Ca²⁺ efflux. Our results provide crucial insights into the antimicrobial action of CA. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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17 pages, 797 KiB

Open AccessArticle

Control of Grapevine Downy Mildew by an Italian Copper Chabasite-Rich Zeolitite

by Francesco Calzarano, Leonardo Seghetti, Giancarlo Pagnani, Elisa Giorgia Metruccio and Stefano Di Marco

Agronomy 2022, 12(7), 1528; https://doi.org/10.3390/agronomy12071528 - 25 Jun 2022

Cited by 2 | Viewed by 2028

Abstract

The progressive reduction in the quantities of copper regulated by the European Union is focusing the research on new formulations with a reduced copper content but equally effective. In this regard, the activity of an Italian copper chabasite-rich zeolitite, which proved to be [...] Read more.

The progressive reduction in the quantities of copper regulated by the European Union is focusing the research on new formulations with a reduced copper content but equally effective. In this regard, the activity of an Italian copper chabasite-rich zeolitite, which proved to be effective against grapevine grey mold and sour rot, was assessed against downy mildew. A two-year study was carried out in the Abruzzo region, Italy, in a cv. Montepulciano vineyard. The applications of the copper zeolitite showed the same good results obtained by a standard integrated/conventional strategy based on contact and systemic fungicides. At harvest, in both trial years, the plants with infected bunches in the untreated control ranged from 86.25% to 100%, compared to 15–30% of the treated plants. Furthermore, infected bunches and berries of the untreated control vines were 70–100% while treated ones never exceeded 2.32%. Furthermore, an increase in the polyphenol content and color intensity in wines made from vines treated with copper zeolitite was confirmed and appeared to be particularly evident in hot and dry seasons. The activity of copper zeolitite towards downy mildew, the potential use against grey mold and sour rot and the protection of grapes from high temperatures indicate that this product is a promising tool for a viticulture environmentally friendly control strategy. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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12 pages, 1293 KiB

Open AccessArticle

Effect of Feeding Stage and Density of Whiteflies on Subsequent Aphid Performance on Tobacco Plants

by Yang Li, Cheng Qu, Xueyan Yan, Xia Sun, Ziyi Yin and Haipeng Zhao

Agronomy 2022, 12(5), 1025; https://doi.org/10.3390/agronomy12051025 - 24 Apr 2022

Cited by 3 | Viewed by 2088

Abstract

Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) is a cosmopolitan, highly polyphagous agricultural pest, which has the capacity to displace other native insect herbivores. Here, equipped with an integrated approach, the effect of developmental stages and feeding density of whiteflies on Myzus persicae [...] Read more.

Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) is a cosmopolitan, highly polyphagous agricultural pest, which has the capacity to displace other native insect herbivores. Here, equipped with an integrated approach, the effect of developmental stages and feeding density of whiteflies on Myzus persicae performance in tobacco plants are investigated. Bioassay results showed that B. tabaci nymphs, but not adult, pre-infestation significantly reduced survival and fecundity of M. persicae, and the strongest resistance to M. persicae was detected at the medium density (9–10 nymphs/cm²). Neither low nor high feeding density of B. tabaci nymphs triggered visible resistance to aphids. However, no significant results were detected in salicylate-deficient NahG plants after B. tabaci nymph infestation. In addition to performance distinctions, hormone quantification and qPCR results revealed very different effects for nymph and adult whitefly stages on the defense responses in tobacco. B. tabaci nymph infestation significantly increased SA accumulation and SA-responsive genes (PR-1a, PR-2a) expression but suppressed JA-regulated responses. In contrast, tobacco plants responded to adult infestation by slightly increasing in both SA- and JA-regulated defenses. Furthermore, higher transcription level of Bt56, coding gene of a secretory salivary effector, was recorded in nymphs vs. adults, while silencing of Bt56 by virus-induced gene silencing (VIGS) partly impaired the aphid resistance induced by B. tabaci nymphs. These results proved that the induction of tobacco defense responses varied with the feeding stages of whiteflies: nymphs of B. tabaci, but not adults, induced a defense response against aphids, with a density threshold for this induced resistance. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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10 pages, 1038 KiB

Open AccessArticle

Dynamics of Pyricularia oryzae Population Race Structures from 2003 to 2017 in Jiangsu Province, China

by Zhongqiang Qi, Yan Du, Muxing Liu, Junjie Yu, Rongsheng Zhang, Mingna Yu, Huijuan Cao, Tianqiao Song, Xiayan Pan, Dong Liang and Yongfeng Liu

Agronomy 2022, 12(4), 956; https://doi.org/10.3390/agronomy12040956 - 15 Apr 2022

Cited by 1 | Viewed by 1887

Abstract

Rice blast, caused by Pyricularia oryzae, is one of the most destructive rice diseases worldwide. It is essential to understand the population structure and race distribution of P. oryzae for the prevention and control of rice blast. This study collected 1584 isolates [...] Read more.

Rice blast, caused by Pyricularia oryzae, is one of the most destructive rice diseases worldwide. It is essential to understand the population structure and race distribution of P. oryzae for the prevention and control of rice blast. This study collected 1584 isolates across Jiangsu province from 2003 to 2017 to determine race diversity, common and dominant race structures, and resistance profiles using eight parameters from the Chinese differential cultivars (CDC) entries. Race diversity analysis indicated that the race diversity of 1584 isolates in Jiangsu province increased from 2003 to 2006 and fluctuated steadily from 2007 to 2017. Common race structure analysis showed that the common race structure of the isolates fluctuated wildly on an annual basis. Moreover, the race ZG1 was the dominant race, suggesting that the most commonly grown rice varieties in Jiangsu are highly adaptive to race ZG1. In addition, due to a higher level (>85%) of resistance to the population of isolates from 2003 to 2017, Tetep may be conformed as the most promising donor of blast resistance for resistance breeding in Jiangsu province. In summary, it is beneficial to control rice blast by continuous monitoring of the population structure and distribution of P. oryzae with the monogenic germplasm entries and by maintaining a diversity of rice varieties. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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15 pages, 2184 KiB

Open AccessArticle

Boron and Zinc Diminish Grey Necrosis Incidence by the Promotion of Desirable Microorganisms on Hazelnut Orchards

by Paola Duran, Patricio Javier Barra, María de la Luz Mora, Adriano Nunes-Nesi and Cristian Merino-Gergichevich

Agronomy 2022, 12(4), 868; https://doi.org/10.3390/agronomy12040868 - 31 Mar 2022

Cited by 3 | Viewed by 2827

Abstract

In the southern hemisphere, the commercial production of hazelnut has increased in recent years, with a concomitant detection of new pathogens associated with plant production, so-called emerging infectious diseases (EIDs). Gray necrosis (GN) is a hazelnut disease that causes 30% of economic losses [...] Read more.

In the southern hemisphere, the commercial production of hazelnut has increased in recent years, with a concomitant detection of new pathogens associated with plant production, so-called emerging infectious diseases (EIDs). Gray necrosis (GN) is a hazelnut disease that causes 30% of economic losses in Europe. In this sense, we recently reported GN as an EID in Chile, the main hazelnut producer in the southern hemisphere. Therefore, control strategies are urgently required to avoid disease dissemination. In this study, the effect of boron (B) and zinc (Zn) fertilization on the incidence of GN was determined. Additionally, the community composition of microorganisms via Dendrogram Gradient Gel Electrophoresis (DGGE) was evaluated, and bacteria from internal tissue (endophytic) were isolated to study their bio-control traits under greenhouse conditions. The microbial occurrence and biocontrol ability was evaluated using MALDI-TOF/TOF. According to the results, B and Zn promote beneficial bacteria which may be able to diminish symptoms associated with GN. Thus, beneficial microorganisms, applied in combination with micronutrients, could be synergistically applied in sustainable agriculture. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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15 pages, 2254 KiB

Open AccessArticle

Efficient Biocontrol of Gaeumannomyces graminis var. Tritici in Wheat: Using Bacteria Isolated from Suppressive Soils

by Isabel Méndez, Ana Fallard, Isabel Soto, Gonzalo Tortella, María de la Luz Mora, Alex J. Valentine, Patricio Javier Barra and Paola Duran

Agronomy 2021, 11(10), 2008; https://doi.org/10.3390/agronomy11102008 - 4 Oct 2021

Cited by 3 | Viewed by 3182

Abstract

“Take-all” disease is the most important biotic factor affecting cereal productivity, causing 30–50% of crop losses. The causal agent is the ascomycete soil-borne pathogen Gaeumannomyces graminis var. tritici (Ggt). Current control measures are ineffective, because Ggt can remain saprophytic in soils for long [...] Read more.

“Take-all” disease is the most important biotic factor affecting cereal productivity, causing 30–50% of crop losses. The causal agent is the ascomycete soil-borne pathogen Gaeumannomyces graminis var. tritici (Ggt). Current control measures are ineffective, because Ggt can remain saprophytic in soils for long periods. Therefore, the study of the microbiome residing in suppressive soils (SS) is a promising niche of Ggt biocontrol. Here, we evaluated the efficiency of Serratia sp., Bacillus sp., and Acinetobacter sp. isolated from SS against the incidence of Ggt on wheat. Our results demonstrated that plants inoculated with the bacterial consortium in both greenhouse and field conditions were highly efficient in Ggt biocontrol, more so than individual strains. The disease reduction was evidenced by higher biomass production, fewer copies of the Ggt genome with a concomitant curtailment of blackening of roots, a decrease of lipid peroxidation, and an increase of superoxide dismutase activity. The ability of the microbial consortium over that of single strains could be attributable to interspecies communication as a strategy to biocontrol; i.e., higher chitinase activity. In conclusion, bacterial consortia from SS are an important niche of Ggt biocontrol, serving as a model for other soil-borne pathogens. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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25 pages, 867 KiB

Open AccessReview

Use of Elicitors and Beneficial Bacteria to Induce and Prime the Stilbene Phytoalexin Response: Applications to Grapevine Disease Resistance

by Philippe Jeandet, Patricia Trotel-Aziz, Cédric Jacquard, Christophe Clément, Chandra Mohan, Iwona Morkunas, Haroon Khan and Aziz Aziz

Agronomy 2023, 13(9), 2225; https://doi.org/10.3390/agronomy13092225 - 25 Aug 2023

Cited by 4 | Viewed by 2403

Abstract

Phytoalexins are naturally occurring molecules with antimicrobial activity deriving from the secondary metabolism of plants; they are synthesized in response to physical agents or stresses and phytopathogenic agents (fungi, bacteria and viruses), as well as numerous chemical compounds and biological control agents. Among [...] Read more.

Phytoalexins are naturally occurring molecules with antimicrobial activity deriving from the secondary metabolism of plants; they are synthesized in response to physical agents or stresses and phytopathogenic agents (fungi, bacteria and viruses), as well as numerous chemical compounds and biological control agents. Among these, grapevine phytoalexins, which belong to the chemical group of stilbenes, exhibit biocidal activity against a large number and variety of plant pathogens. It is important to investigate whether induction of stilbene phytoalexin production can serve to protect this plant against its pathogens. Quite a few chemical compounds, derivatives of phytohormones bio-elicitors as well as biocontrol agents, have been used to induce the synthesis of stilbene phytoalexins with the aim of conferring protection to grapevine against its main diseases (gray mold, downy mildew, powdery mildew and esca). This article reviews the experiments that have been carried out in this direction during the last 30 years and shows that the observed protective effects towards pathogens are generally linked to induction and priming of the grapevine phytoalexin response, confirming the interest in using, in a more general way, stimulation of the production of phytoalexins in plants as a basis for crop protection. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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24 pages, 1203 KiB

Open AccessFeature PaperReview

Prospects for Increasing the Efficacy of Plant Resistance Inducers Stimulating Salicylic Acid

by Laurent Urban, Félicie Lauri, Douae Ben Hdech and Jawad Aarrouf

Agronomy 2022, 12(12), 3151; https://doi.org/10.3390/agronomy12123151 - 12 Dec 2022

Cited by 13 | Viewed by 3428

Abstract

Systemic acquired resistance is a powerful mechanism, based on the salicylic acid (SA) signaling pathway, which allows plants to resist to a wide range of pathogens. High SA, moreover, plays a key role in plant tolerance to abiotic stress. It seems, therefore, desirable [...] Read more.

Systemic acquired resistance is a powerful mechanism, based on the salicylic acid (SA) signaling pathway, which allows plants to resist to a wide range of pathogens. High SA, moreover, plays a key role in plant tolerance to abiotic stress. It seems, therefore, desirable to supply analogs of SA or stimulate the production of endogenous SA. Unfortunately, the chemical substances or physical means used for this effect often display a variable efficacy. After providing a review of them, we defend three major ideas: (i) plant resistance inducers (PRIs) must be combined for higher efficacy, notably for exploiting synergic effects between the SA and other signaling pathways, (ii) disease pressure can be reduced by exploiting the fungicidal properties displayed by some PRIs, (iii) biostimulants and crop management techniques should be used to ensure that plants have the resources they need to synthesize the compounds and structures required for efficient and lasting resistance. Some PRIs could also be used for their biostimulant effects in stress conditions. It could be concluded that holistic approaches which jointly address the issues of defense and tolerance stimulation, disease pressure and resource availability in plants are the ones that will allow for substantial reduction in fungicide use without sacrificing crop performance. Full article

(This article belongs to the Special Issue Phytoalexins, Resistance Inducers, and Sustainable Control Measures in Crop Protection Strategies)

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