Journal of Phytopathology最新文献

This research addresses the presence of Elsinoë phaseoli in Kenya, where information on the biology of this pathogen remains scarce. Employing a multifaceted approach, the study demonstrates the steps taken to isolate, identify, and characterize E. phaseoli as the pathogen responsible for scab on common bean. Field observations confirmed scab symptoms, particularly the prominent pod lesions. Elsinoë phaseoli was isolated from common bean using a targeted streaking method on older acervulus-bearing lesions. Morphological examinations revealed a notable diversity within E. phaseoli colonies, consistent with the characteristics of the genus. Molecular identification through ITS-rDNA sequencing confirmed isolate AscoSK1 obtained in this study as belonging to E. phaseoli, offering a robust species differentiation method. Assessing conidium production required the implementation of five different culture methods. An adaptation of the Scheper et al. (2013) method yielded the highest quantity of conidia from 25 colonies spaced at 1 cm apart, with a conidial yield of 5.0 × 10⁶ conidia per 9-cm-diameter Petri dish. A higher conidial yield was attained after the colonies were pre-incubated on potato dextrose agar in the dark at room temperature for 28 days, followed by a transfer to corn meal agar for an additional 2 days at 20°C. This emphasizes the pivotal influence of incubation duration and pre-culture conditions on the process. This research provides insights into the biology of E. phaseoli and introduces an improved method for enhancing in vitro sporulation of the pathogen, setting groundwork for future research and handling.

Castor bean (Ricinus communis) is a crop of great economic importance in Brazil. It is used for producing oil used in the manufacture of cosmetics and biodiesel. The genus Phytophthora contains pathogens with a wide range of host plants, including ornamentals, fruit and vegetable crops. Among the symptoms induced by Phytophthora species are collar and root rot. This study aimed to identify Phytophthora species causing collar and root rot in castor bean seedlings in the Federal District and test their pathogenicity. Samples of symptomatic plants were collected in four satellite cities in Distrito Federal, Brazil. Fourteen isolates were obtained, and they were initially identified through the morphology of reproductive structures. The isolates were subjected to molecular characterization using phylogeny of the sequences from the ITS region and the Cytochrome Oxidase II gene. Ten isolates of the pathogen were tested for pathogenicity on seedlings of two castor bean accessions and species known to be hosts of P. nicotianae. The isolates were identified as P. nicotianae (12 isolates) and P. palmivora (two isolates). In the pathogenicity test, all isolates were capable of causing disease in castor beans. The isolates of P. nicotianae and P. palmivora varied in pathogenicity to other plant species. This is the first report of P. nicotianae causing collar and root rot in castor bean in the Central-West Region of Brazil. It is also the first report of P. palmivora causing diseases in castor beans in South America.

Postharvest diseases in fruits result in significant losses in the agricultural sector. Among these, green mould, caused by Penicillium digitatum, poses a considerable threat to citrus fruits. This study evaluated the potential of Bacillus amyloliquefaciens strain TV-17C as a biological control agent for managing green mould in oranges. Various concentrations of TV-17C in aqueous suspension were applied to naturally infected orange fruits in the packinghouse at two locations (Hatay and Mersin provinces), while the chemical fungicide fludioxonil 230 SC served as a positive control. The application of B. amyloliquefaciens TV-17C at the dosage of 250 mL 100 L⁻¹ reduced green mould incidence by 90.3% and 89.8% in Hatay and Mersin provinces, respectively. Similarly, fludioxonil 230 SC displayed an efficacy of 91.4% in reducing disease incidence. In summary, this study underscores the potential of B. amyloliquefaciens TV-17C as an efficient biocontrol agent against green mould in oranges. Moreover, a positive correlation between higher concentrations and enhanced efficacy was evident. These findings hold promise for the adoption of sustainable disease management practices in the postharvest citrus industry.

The impact of eight pesticides on the transmission of Tomato leaf curl virus (ToLCV) by the whitefly, Bemisia tabaci Gennadius to tomato, Lycopersicon esculentum (Miller), was studied in the field using a randomized block design. Differences in performance were anticipated because these eight insecticides comprise distinct mechanism of action including both contact and systemic. Increased insecticide efficacy is necessary, particularly in regions with conducive weather conditions that support a healthy whitefly population, to effectively manage the population. There is a need to vary the insecticides used in order to reduce the emergence of resistance in the whitefly population due to the extensive usage of a single mechanism of action for whitefly control. The foliar spray of insecticides was done when first incidence of whitefly was noticed in the field with 15 days of interval. The studies on effect of different insecticides in the management of ToLCV disease through the controlling whitefly population, we evaluated that Chlorantraniliprole 8.8% + Thiomethaxam 17.5% SC was effective in sustaining the yield by reducing the incidence of disease and whitefly population during both the years followed by Spirotetramat 11.01% + Imidacloprid 11.01% SC, Thiamethoxam 12.6% + Lambda cyhalothrin 9.5% ZC and Cyantraniliprole 10.26% OD, respectively.

In a previous study, common bean (Phaseolus vulgaris L.) genotypes were selected in the field for reactions to white mould (WM), caused by Sclerotinia sclerotiorum. These genotypes, along with the resistant control A195, were then evaluated in both field and greenhouse (straw test) conditions. The results showed that field trials effectively identified high-yielding WM-resistant genotypes for dry-irrigated conditions. Here we challenge the results of this study with new data and methodology by conducting six sprinkler-irrigated trials from 2015 to 2017 with five genotype groups (G). Three groups comprised genotypes previously studied: G1, seven partially resistant; G4, two intermediately resistant; and G5, three susceptible. G2 consisted of four lines selected for partial resistance in the current study. The resistant control group, G3, comprised the genotypes A195, G122, Cornell605, and Ouro Branco. WM was absent (one trial), or pressure was either low/moderate (two trials) or moderate/high (three trials). The average seed yield ranged from 2207 (G3) to 3178 kg/ha (G1). The contrast G1, G2 versus G3 was nonsignificant for incidence and severity index, indicating that genotypes selected for resistance in the field were as resistant as the resistant control genotypes. Additionally, the groups selected for resistance yielded 43% more and produced 33% less sclerotia weight compared with the control group. Our results reinforce the effectiveness of selecting WM-resistant genotypes using beans originally bred for purposes other than WM-resistance, specifically targeting dry-irrigated areas. Furthermore, our results suggest that the use of genotypes selected for partial resistance reduces inoculum levels in the soil.

Bacterial halo blight (BHB), caused by Pseudomonas coronafaciens pv. garcae (Pcg), is one of the most significant diseases affecting coffee trees worldwide, resulting in considerable damage and notable losses within coffee production systems. Further research into the epidemiology and aetiology of BHB in coffee plants is essential for developing effective management strategies. Understanding the efficiency of each inoculation methodology in inducing symptoms is crucial for advancing this research. Therefore, this study aimed to assess the efficiency of seven Pcg inoculation methods using five concentrations to enhance the highest BHB intensity. The experimental design was a complete randomized block design in a factorial (7 × 5) variance analysis with four replications. The first three pairs of leaves of coffee seedlings of the cultivar Catuaí Vermelho IAC-99 were inoculated and evaluated for the incidence and severity of BHB. The inoculation methods of Pcg by injury provided higher BHB AUDPCI and AUDPCS values. Among these, the inoculum injection and multi-needle wounding at inoculum concentrations of 1.6 × 10⁹ CFU mL⁻¹ demonstrated higher disease intensity.

Pythium tracheiphilum is a narrow host range oomycete first described infecting lettuce in Italy. Subsequently, the pathogen was reported in many other countries. From 2015 to 2019, Pythium isolates were recovered from lettuce plants with symptoms of leaf rot, wilting and vascular necrosis, collected from commercial fields in different rural localities of Brasilia-DF, Brazil. The isolates were identified as P. tracheiphilum based on morphological and molecular genetic analysis. Pathogenicity tests conducted with four P. tracheiphilum isolates confirmed that the isolates were pathogenic to detached leaves of a loose-hearted lettuce cultivar. This is the first report of P. tracheiphilum infecting lettuces in Brazil.

Fusarium oxysporum f.sp. conglutinans (FOC) causes yellow wilt, a serious cabbage disease. This fungal species is composed of many strains within two pathotypes. In this study, the inhibitory effect of essential oils of six aromatic and medicinal plants (oregano, thyme, clove, cinnamon, lemongrass, litsea) at multiple concentrations on eight FOC isolates of different origins was investigated. Our results showed that oregano essential oil had the greatest inhibitory effect. The tested essential oils could be divided into three clusters according to the similar content of their main components (oregano and thyme, clove and cinnamon, lemongrass, and litsea), which correlated to some extent with their inhibitory effects on FOC. The tested isolates also differed in their response to the studied essential oils. The differences within FOC races were more important than between races, and the sensitivity of isolates against essential oils seemed to be more related to the geographical origin of the isolates, rather than to their race affiliation.

Yellow mosaic and leaf curl diseases caused by whitefly-transmitted begomo virus genera are important problems in tomato (Solanum lycopersicon L.) production in Indonesia, particularly on Java Island. The aims of this survey are to assess the percentages of disease incidence (DI) and disease severity index (DSI), evaluate the spread and complexity of begomovirus and crinivirus infections responsible for yellow mosaic and leaf curl diseases in tomato plants, and identify the species of whitefly insect vectors and their cryptic biotypes in tomato production centers located on Java Island, Indonesia. A total of 43 locations in East, Central, and West Java were surveyed during the dry season from July 2022 to September 2022. Disease incidence and severity were determined by observing 200 samples of tomato plants from five points at each location, with 40 plants per point of land. A total of 116 whitefly samples in microtubes and 215 symptomatic leaf samples were collected. The genus begomovirus and crinivirus infecting tomato were identified by PCR and RT-PCR using genus-specific primers. Similarly, whitefly species and their cryptic biotypes were identified by PCR using MCoI gene-specific primers. Results showed that DI and DSI remarkably differed between the lowlands (66%–89%) and highlands (33%–62%) in the provinces of Central Java and West Java. Furthermore, PCR analysis of 215 infected tomato showing the symptoms of yellow mosaic and curly leaf revealed that three begomoviruses, one crinivirus and their mixed combination both begomoviruses, one crinivirus has been detected in all the samples. Similarly, the whitefly insect vector Bemisia tabaci biotype Q was identified in all areas, whereas Trialeurodes vaporariorum was found only in the East Java and Java highlands, respectively.

Desmodium triflorum is an important gramineous forage grown in tropical regions of China. In August 2022, a new leaf spot disease was observed on D. triflorum during a field survey at the base of the Chinese Academy of Tropical Agricultural Sciences, Hainan, China. The pathogen was isolated and identified using morphological examination and phylogeny based on multi-gene sequences analysis of the nuclear ribosomal internal transcribed spacer, the second largest RNA polymerase subunit (RPB2), and beta-tubulin genes. The isolates were identified as Epicoccum sorghinum. The pathogenicity of E. sorghinum on D. triflorum was validated fulfilling Koch's postulates, causing leaf spot disease. To the best of our knowledge, this is the first report of leaf spot disease on D. triflorum caused by E. sorghinum in China.