Phytopathology最新文献

{"title":"Dispersive Epidemic Waves: I. Focus Expansion within a Linear Planting.","authors":"Francis J Ferrandino","doi":"10.1094/Phyto-83-795","DOIUrl":"10.1094/Phyto-83-795","url":null,"abstract":"<p><p>The three-dimensional, turbulent dispersal of airborne spores yielded epidemiological contact distributions characterized by a length scale that continually increased with increasing downwind distance. This behavior was due to the escape of spores from the plant canopy into the faster moving air above. Such contact distributions approached an inverse power law of distance at large distances. Simulated epidemics based on this type of spore dispersal exhibited spatial disease gradients that became more shallow as the epidemic progressed. Isopathic velocities were related linearly to distance from the focus of disease, irrespective of disease severity. Thus, the leading edge of this dispersive epidemic wave propagated more quickly than did the trailing edge; as a result, the wave spread out in space with increasing time. This behavior contrasted the constant isopathic velocities characteristic of the traveling wave description predicted by spatial contact distributions of an exponential order that had a bounded length scale. A traveling wave description is appropriate if the spatial coordinate is log-transformed first.</p>","PeriodicalId":20410,"journal":{"name":"Phytopathology","volume":"83 1","pages":"795-802"},"PeriodicalIF":3.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61212278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of a Minireplicon for Grapevine Leafroll-Associated Virus 1 and Genetic Analyses of Sequences in the 5' Non-Translated Region Required for Replication.","authors":"Arunabha Mitra, Sridhar Jarugula, Rayapati A Naidu","doi":"10.1094/PHYTO-12-24-0380-R","DOIUrl":"10.1094/PHYTO-12-24-0380-R","url":null,"abstract":"<p><p>Grapevine leafroll-associated virus 1 (GLRaV-1, genus <i>Ampelovirus</i>, family <i>Closteroviridae</i>) has a monopartite RNA genome with the size varying among genetic variants between 18,731 and 18,946 nucleotides (nt) and a 5' non-translated region (5'-NTR), varying in length between 857 and 922 nt. This study was undertaken to examine the role of the 5'-NTR in GLRaV-1 replication. For this purpose, a minireplicon cDNA clone, consisting of the 5'-NTR, the replicase gene module, the green fluorescent protein (GFP) reporter gene, and the 3'-NTR, was constructed. The functionality of the minireplicon was validated by GFP fluorescence and the presence of GFP-specific mRNA transcripts by Northern blot hybridization and reverse transcription quantitative PCR assays in <i>Nicotiana benthamiana</i> leaves agro-coinfiltrated with silencing suppressors. The minireplicon retained functionality when its 5'-NTR was exchanged with corresponding sequences from distinct genetic variants of GLRaV-1. In contrast, the minireplicon of GLRaV-1 was nonfunctional when its 5'-NTR sequence was swapped with corresponding sequences from other GLRaV species. Deletion mutations in the 5'-NTR indicated that the first 32 nt at the 5'-terminus of the genome are essential for replication of the minireplicon. The in silico-predicted secondary structure of the 5'-terminal 32-nt sequence showed two stem-loop structures and mutations that altered these secondary structures or compensatory mutations preserving the secondary structures that failed to retain functionality of the minireplicon, suggesting that the nucleotide sequence, rather than any higher order secondary structures in this genomic region, is important for replication.</p>","PeriodicalId":20410,"journal":{"name":"Phytopathology","volume":" ","pages":"1065-1075"},"PeriodicalIF":3.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144102491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inheritance of Pathogenicity in <i>Melampsora lini</i>.","authors":"H H Flor","doi":"10.1094/Phyto-32-653","DOIUrl":"10.1094/Phyto-32-653","url":null,"abstract":"&lt;p&gt;&lt;p&gt;The flax-rust fungus, &lt;i&gt;Melampsora lini&lt;/i&gt; (Pers.) Lév., is autoecious and long-cycle; that is, it produces its pycnial, aecial, uredial, and telial stages solely on species of flax. Allen (1) demonstrated the heterothallic nature of &lt;i&gt;M. lini&lt;/i&gt;, and Flor (3, 4) found that rust of cultivated flax, &lt;i&gt;Linum usitatissimum&lt;/i&gt; L., comprised numerous physiologic races. Every flax variety tested has been susceptible to 1 or more of 24 physiologic races identified from North and South American collections of flax rust. However, no single race known is capable of attacking all of the 11 differential varieties used in these tests. In the northern United States, flax rust overwinters by means of telia (6) and, consequently, natural hybridization is probably coincident with the initiation of infection each year. A sound program for the production of desirable rust-resistant varieties of flax requires knowledge not only of the interaction of the factors governing rust reaction possessed by the varieties of flax but also of the interaction of the factors for pathogenicity in various races of the flax-rust fungus. The data reported in the present paper deals with the latter subject. Knowledge of the inheritance of pathogenicity in the rusts is limited. It was not until 1927 that Craigie (2) demonstrated the heterothallic nature of rusts and thus made possible the genetic study of these organisms. Physiologic races of rust are differentiated by the type of infection produced on a series of differential varieties, a laborious process restricting the number of progeny cultures that can be studied. Additional impediments to the genetic study of pathogenicity in the rusts are the capricious germination of the telia and the difficulty of obtaining races of known homozygosity. It also is probable that the differential varieties used to identify the physiologic races are not capable of resolving the rust into all its genotypic strains. New physiologic races of cereal rusts have been obtained by selfing or crossing known races of &lt;i&gt;Puccinia graminis tritici&lt;/i&gt; Eriks. and Henn. (8, 12, 13, 16), &lt;i&gt;P. graminis avenae&lt;/i&gt; Eriks. and Henn. (10), and &lt;i&gt;P. rubigo-vera tritici&lt;/i&gt; (Eriks. and Henn.) Carl. (17), as well as by crossing the different varieties of stem rust (14). The data of Johnson, Newton, and Brown (8), obtained in a study of the inheritance of pathogenicity in a cross between two races (9a x 36) of &lt;i&gt;P. graminis tritici&lt;/i&gt;, point toward Mendelian inheritance. In this cross the pathogenicity of F&lt;sub&gt;2&lt;/sub&gt; rust cultures to Arnautka Mindum, and Spelmar appeared to be inherited as a unit and was conditioned by a single pair of factors with virulence dominant. Pathogenicity to Kanred was conditioned by a single pair of factors with avirulence dominant, and pathogenicity to Vernal by 2 pairs of duplicate factors with avirulence dominant. Wach of these 3 characters appeared to be inherited independently. In a cross between races of &lt;i&gt;P. graminis","PeriodicalId":20410,"journal":{"name":"Phytopathology","volume":"115 8V","pages":"653-669"},"PeriodicalIF":3.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145041069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Improved Grading System for Measuring Plant Diseases.","authors":"J G Horsfall, R W Barratt","doi":"10.1094/Phyto-35-655","DOIUrl":"10.1094/Phyto-35-655","url":null,"abstract":"<p><p>Heretofore, in recording severity of plant diseases by grading, the grades have been assigned equal values in percentage. According to the Weber-Fechner law, the human eye distinguishes according to the logarithm of the light intensity. Hence, the grades should be based on equal ability to distinguish, not on equal disease. Below 50 percent, the eye sees the amount of diseased tissue. Above 50 percent, it sees the amount of disease-free tissue. A new scoring system is based on 50 percent as a midpoint. The grades differ by a factor of two in either direction as follows: 1 = 0, 2 = 0 to 3, 3 = 3 to 6, to 12, 5 = 12 to 25, 6 = 25 to 50, 7 = 50 to 75, 8 = 75 to 87, 9 = 87 to 94, 10 = 94 to 97, 11 = 97 to 100, 12 = 100. Several plants (20 or more) at random are graded. Mean grade = grade readings + number of readings. A calibration curve is set up with grade numbers on the X-axis and percentage disease on a special semi-log. Y-axis with one and one-half phases from either end up to 50 percent. The grid has the aspect of arithmetic-probability paper. This scheme has been very useful in fungicide research, varietal resistance, etc. It should be useful in plant disease surveying.</p>","PeriodicalId":20410,"journal":{"name":"Phytopathology","volume":"115 8V","pages":"655"},"PeriodicalIF":3.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145041051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ontogeny-Dependent Development of Diffuse Abaxial Scab Symptoms on Apple Leaves.","authors":"Anže Švara, Luk De Maeyer, Willem Abts, Kathy Steppe, Sarah Verbeke, Wendy van Hemelrijck, Maja Mikulic-Petkovsek, Robert Veberic, Ernestina Lavrih, Nico De Storme","doi":"10.1094/PHYTO-09-23-0350-R","DOIUrl":"10.1094/PHYTO-09-23-0350-R","url":null,"abstract":"<p><p>Diffuse apple scab symptoms on the abaxial leaf surface are caused by the fungal pathogen <i>Venturia inaequalis</i> and occur even in well-managed orchards. The disease is challenging to manage, as the symptoms emerge on aging leaves later in the season and only develop on some leaves, suggesting the involvement of intrinsic defense mechanisms. We studied the development of diffuse abaxial scab symptoms on 'Jonagold' leaves in an orchard at three different shoot positions and at four different time points during the growing season to identify leaf-specific defense mechanisms. We identified infection moments by tracking the ascospore load and formation of new shoot leaves and determined the period required for proliferation of diffuse abaxial scab symptoms. Then, we correlated gene expression and phenolics profiles with the <i>V. inaequalis</i> DNA content to identify those inhibiting scab proliferation in asymptomatic leaves. Leaves in the middle of shoots showed higher symptom expression compared with shoot base and tip leaves. Disease inhibition in asymptomatic leaves was negatively correlated with several defense-related genes and phenolics. Altogether, our observations highlight that diffuse abaxial scab is one of the key challenges in apple growing and that the leaf ontogenic status during the infection process affects the development of these symptoms, with putative regulation by phenolic metabolism and ontogeny-related defense genes.</p>","PeriodicalId":20410,"journal":{"name":"Phytopathology","volume":" ","pages":"1018-1027"},"PeriodicalIF":3.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144664042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Suppression of Take-All of Wheat by Seed Treatments with Fluorescent Pseudomonads.","authors":"D M Weller, R J Cook","doi":"10.1094/Phyto-73-463","DOIUrl":"10.1094/Phyto-73-463","url":null,"abstract":"<p><p>Strains of fluorescent <i>Pseudomonas</i> spp. applied to wheat seeds suppressed take-all in both greenhouse- and field-grown winter and spring wheat. The effective strains were originally isolated from roots of wheat grown in soil naturally suppressive to take-all and were selected on the basis of in vitro antibiosis to <i>Gaeumannomyces graminis</i> var. <i>tritici</i>. Isolate 2-79, alone or combined with isolate 13-79, suppressed take-all in five of six field tests conducted in nonfumigated soil infested with inoculum of <i>G. graminis</i> var. <i>tritici</i>. The combination treatment was more suppressive than 13-79 alone in all field tests, and was slightly more suppressive than 2-79 alone in three of six field tests. Suppression of take-all by the bacteria was expressed in the field as fewer plants with foliage symptoms of take-all and taller plants, more heads, greater yield, and less root disease than those grown from nontreated seed. Tests in field plots fumigated with methyl bromide, with and without the reintroduction of <i>G. graminis</i> var. <i>tritici</i>, established that the bacteria do not promote plant growth other than by controlling of take-all. The seed treatment resulted in increased yields of up to 147% in fumigated soil and up to 27% in natural soil. An antibiotic-resistant strain of 2-79 was isolated from the roots of wheat in the field following germination of bacteria-treated seed. The population of the introduced bacterium exceeded 10⁶ colony-forming units per 0.1 g of root tissue 3 wk after planting. The populations of strains 2-79 and 13-79 applied on wheat seeds with methylcellulose were stable for 21 days at 5 or 15 C, but declined rapidly at 25 C.</p>","PeriodicalId":20410,"journal":{"name":"Phytopathology","volume":"73 1","pages":"463-469"},"PeriodicalIF":3.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61170543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of Rhizosphere Colonization by Plant Growth-Promoting Rhizobacteria on Potato Plant Development and Yield.","authors":"J W Kloepper, M N Schroth, T D Miller","doi":"10.1094/Phyto-70-1078","DOIUrl":"10.1094/Phyto-70-1078","url":null,"abstract":"<p><p>Two strains of fluorescent <i>Pseudomonas</i> spp. isolated from potato periderms and from celery roots significantly increased growth of potato plants up to 500% greater than controls in greenhouse assays. Mutants of these plant growth-promoting rhizobacteria (PGPR) resistant to rifampicin and nalidixic acid rapidly colonized rhizospheres of roots emerging from treated seed pieces in field tests. The bacteria colonized the entire rhizosphere of treated plants including developing daughter tubers and the apical roots of adjacent nontreated plants. PGPR rhizosphere populations were as great as 9.6 × 10⁵ colony-forming units per centimeter (cfu/cm) of root 2 wk after plant emergence and averaged 10³ cfu/cm throughout the season, but declined to approximately 10² cfu/cm at harvest time. PGPR populations were relatively constant throughout the root system. Field tests were done in various soil types with pH ranges from 6.8 to 7.8. PGPR rhizosphere colonization resulted in significant increases in stolon length 2 wk after plant emergence in all six sampled fields. The early season plant growth promotion caused by PGPR was followed by significant yield increases up to 17% compared to untreated controls in four of five harvested fields.</p>","PeriodicalId":20410,"journal":{"name":"Phytopathology","volume":"70 1","pages":"1078-1082"},"PeriodicalIF":3.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61154216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Increased Potato Yields by Treatment of Seedpieces with Specific Strains of <i>Pseudomonas fluorescens</i> and <i>P. putida</i>.","authors":"T J Burr, M N Schroth, T Suslow","doi":"10.1094/Phyto-68-1377","DOIUrl":"10.1094/Phyto-68-1377","url":null,"abstract":"<p><p>Significant increases in growth and yield of potato plants were achieved by treating seedpieces with suspensions of two <i>Pseudomonas</i> spp. at ∼10⁹ colony-forming units (cfu)/ml prior to planting. The pseudomonads were selected from over 100 strains that were isolated from the surface of potato tubers and also exhibited antibiosis against <i>Erwinia carotovora</i> var. <i>carotovora</i> in vitro. The isolates were identified as strains of <i>Pseudomonas fluorescens</i> and <i>P. putida.</i> These strains survived for at least 1 mo on treated seedpieces planted in loamy sand field soil at populations of ∼10⁹ cfu/0.785 cm². Also, they colonized developing potato roots and were the predominant bacteria in the rhizospheres up to 2 mo after planting. Bacterization of seedpieces planted in field soils in the greenhouse resulted in up to 100% increase in fresh weight of shoot and root systems in a 4-wk period. Statistically significant increases in yield ranged from 14 to 33% in five of nine field plots in California and Idaho. The pseudomonads had no effect on plant growth or tuber yield when seedpieces were planted in peat soil, or in soil that was relatively dry. Both <i>Pseudomonas</i> spp. were compatible with fungicides that were commonly used to treat seedpieces, except for manganese ethylenebisdithio-carbamate zinc salt (mancozeb). The mechanism by which these bacteria enhance plant growth and tuber yield may be associated with changes in the composition of rhizosphere bacterial flora.</p>","PeriodicalId":20410,"journal":{"name":"Phytopathology","volume":"68 1","pages":"1377-1383"},"PeriodicalIF":3.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61145063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Control of <i>Rhizoctonia solani</i> on Cotton Seedlings with <i>Pseudomonas fluorescens</i> and With an Antibiotic Produced by the Bacterium.","authors":"C R Howell, R D Stipanovic","doi":"10.1094/Phyto-69-480","DOIUrl":"10.1094/Phyto-69-480","url":null,"abstract":"<p><p>A strain of <i>Pseudomonas fluorescens</i> antagonistic to <i>Rhizoctonia solani</i> was isolated from the rhizosphere of cotton seedlings. An antibiotic strongly inhibitory to <i>R. solani</i> was isolated from <i>P. fluorescens</i> cultures and identified as pyrrolnitrin (3-chloro-4-[2'-nitro-3'-chlorophenyl]-pyrrole). The antibiotic also inhibited growth of other fungi associated with the cotton seedling disease complex including: <i>Thielaviopsis basicola, Alternaria</i> sp., and <i>Verticillium dahliae.</i> A <i>Fusarium</i> sp. was only partially inhibited and <i>Pythium ultimum</i> was unaffected. Treating cottonseed with <i>P. fluorescens</i> or pyrrolnitrin at time of planting in <i>R. solani</i>-infested soil increased seedling survival from 30 to 79% and from 13 to 70%, respectively. Pyrrolnitrin persisted for up to 30 days in moist nonsterile soil with no measurable loss in activity.</p>","PeriodicalId":20410,"journal":{"name":"Phytopathology","volume":"102 1","pages":"480-482"},"PeriodicalIF":3.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61152454","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Solar Heating by Polyethylene Mulching for the Control of Diseases Caused by Soil-Borne Pathogens.","authors":"J Katan, A Greenberger, H Alon, A Grinstein","doi":"10.1094/Phyto-66-683","DOIUrl":"10.1094/Phyto-66-683","url":null,"abstract":"<p><p>Irrigated soils in the hot Bet-Shean and Jordan Valley regions were mulched with transparent 0.03-mm polyethylene sheets during the months of July or August, and soil temperatures were thereby increased. Different types of inocula of <i>Verticillium dahliae</i> and <i>Fusarium oxysporum</i> f. sp. <i>lycopersici</i> were buried in mulched and nonmulched soils at various depths, recovered after certain time intervals, and their populations were estimated. After two weeks under polyethylene sheets, <i>V. dahliae</i> was eliminated at depths of 0 to 25 cm. The population of <i>F. oxysporum</i> f. sp. <i>lycopersici</i> at the depth of 5 cm was reduced by 94 to 100%; at 15 cm, 68 to 100%; and at 25 cm, 54 to 63%. Maximal temperatures in the mulched soils were 49 to 52 C and 42 C at depths of 5 and 15 cm, respectively. At 50 C, soil fungistasis to <i>Fusarium</i> was partially nullified. Two field experiments with eggplant and one with tomato showed, that mulching with polyethylene sheets prior to planting reduced Verticillium wilt by 25 to 95%, controlled weeds, improved plant growth and stand, and increased yield. This method of control using plastic material is less costly than fumigation, is nonhazardous, and leaves no residues. It is suggested that biological as well as thermal control may take place during soil mulching.</p>","PeriodicalId":20410,"journal":{"name":"Phytopathology","volume":"66 1","pages":"683-688"},"PeriodicalIF":3.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61138254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}