Journal of Phytopathology最新文献

The oomycete Phytophthora infestans (Mont.) de Bary is a causative agent of the most harmful potato disease, late blight. The pathogenicity of P. infestans is associated with (a)virulence genes (Avr genes). Changes in the composition and nucleotide sequence of these genes lead to the emergence of new races of the pathogen, which affect potato varieties previously considered resistant. Therefore, to successfully combat late blight, it is important to study polymorphisms in Avr genes in populations of this pathogen. We conducted a large-scale molecular and phytopathological study of P. infestans strains collected in European Russia. In this study, polymorphisms of 11 Avr genes were analysed using SSCP analysis and sequencing. The genes included Avr1, Avr2, Avr2-like, Avr3a, Avr3b, Avr4, Avr8, Avr-Smira1, Avr-blb1, Avr-blb2 and Avr-vnt1. As a result, the allelic composition of Avr genes was studied and new alleles unique to Russia were identified in Russian populations of P. infestans for all studied Avr genes, with the exception of Avr4 and Avr8. The vast majority of the Avr1, Avr2-like, Avr3a, Avr4, Avr-vnt1 and Avr-Smira1 gene sequences correspond to known virulence variants of these genes that avoid recognition by the corresponding potato resistance genes. The Avr-blb2 gene was represented by approximately equal amounts of virulent and avirulent variants. Predominantly avirulent variants were found for the Avr-blb1 gene. The Avr2, Avr3b and Avr8 genes were represented only by avirulent variants. Summarising the results of our study, we can conclude that the populations of the European territory of Russia differ from the populations of Europe and the USA in the allelic composition of virulence genes. We failed to detect a dominant clonal lineage in the territory of Russia, and the Russian population of P. infestans is highly diverse.

Urdbean leaf crinkle disease (ULCD) is a major factor causing severe yield loss in black gram production. The identification of quantitative trait loci (QTL) linked to ULCD resistance is highly useful in breeding programmes. A mapping population was developed from a cross between the resistant parent CO 5 and the susceptible parent TU 68. ULCD screening was carried out through the artificial sap inoculation method. In the F_2:3 population, the ULCD score was assessed 60 days after infection. Composite interval mapping was carried out with a 1000-run permutation. Another mapping population, VBN(Bg) 4 × CO 5 in F_2:3 generation was used to validate the identified QTL. A single locus, qULCD3.1 was identified in linkage group 3. It explains 17.98% of the variation in ULCD resistance. Markers VR086 and CEDG 305 flanked the QTL region. The marker CEDG 305 explains 20.5% of the phenotypic variation for ULCD resistance in the validation population VBN(Bg) 4 × CO 5. This is the first report to identify a QTL for ULCD disease resistance. The identified markers can be used to incorporate ULCD resistance in black gram through marker-assisted selection.

In August 2023, severe symptoms of crown and root rot were detected on blueberry plants in two commercial fields located in Guasave, Sinaloa, Mexico. Colonies with oomycete morphology were obtained and two isolates were purified. The causal agent was identified as Phytopythium helicoides by a combination of morphological studies, pathogenicity tests, and phylogenetic analysis including data from internal transcribed spacer and large subunit sequences. This is the first report of P. helicoides causing crown and root rot of blueberry worldwide.

Astragalus membranaceus var. mongholicus (Mongolian milkvetch) is one of the most important traditional Chinese medicinal plants. In July 2021, root rot of A. membranaceus var. mongholicus was found in a field in Tongren City, Huangnan Tibetan Autonomous Prefecture, Qinghai Province, China. The aboveground part of the plants exhibited yellowing, wilting and defoliation in severe cases. Seven fungal isolates were obtained, and their pathogenicity, morphology and phylogeny were analysed. A pathogenicity test was performed using the scratch and root irrigation methods, and the results showed that all seven isolates caused root rot on inoculated plants. Based on morphological characteristics and phylogenetic analysis of multi-locus sequences (ITS, translation elongation factor [TEF-1α], and RNA polymerase II beta subunit [RPB2] genes), two isolates were identified as Fusarium avenaceum, and five isolates were identified as F. flocciferum. To the best of our knowledge, this is the first report of F. avenaceum and F. flocciferum causing root rot of A. membranaceus var. mongholicus in China.

Carrot (Daucus carota L. subsp. sativus) cultivation is important in Argentina, with the Garay department in Santa Fe province being a key production area. In recent years, dry rot symptoms have afflicted various carrot cultivars, resulting in substantial field losses and postharvest discards. Several soilborne pathogens, including Fusarium species, have been implicated in similar carrot diseases globally. This study aimed to identify the specific causal agent responsible for dry rot in carrots in central Argentina to enable targeted disease management strategies. Samples of symptomatic carrots were collected from fields in the Garay department. Fungal isolates were obtained from the infected tissue and subjected to morphological and molecular analyses. Pathogenicity tests were conducted to confirm the ability of the isolates to cause disease symptoms in carrots. Based on morphological and molecular identification, isolates were identified as Fusarium nirenbergiae, Fusarium triseptatum and Fusarium solani. Pathogenicity tests demonstrated that the three Fusarium species were capable of causing dry rot symptoms in carrots. This study represents the first report of Fusarium nirenbergiae, Fusarium triseptatum and Fusarium solani causing dry rot in carrots in Argentina.

Lentil (Lens culinaris) is an important pulse crop in India. Fusarium wilt caused by Fusarium oxysporum f. sp. lentis (Fol), is a major biotic constraint in lentil production. The present investigation was undertaken to evaluate the efficacy of combination products of fungicides and bio-agents against Fol under in vitro and in vivo conditions. Fungicides were evaluated using the poisoned food technique, while the antagonistic activity of bio-agents was studied using dual culture technique. Among seven combination products of fungicides, carbendazim 12% + mancozeb 63% was the most effective fungicide in restricting the colony diameter of the pathogen. In field conditions, the seed treatment with carbendazim 12% + mancozeb 63% at 2.5 g/kg seed performed best in both yield and seed quality parameters. Among the bio-agents tested, Trichoderma asperullum gave the best results in suppressing pathogen growth under in vitro conditions. The seed treatment with the combination of T. asperullum + Pseudomonas fluorescens at 5 g/kg seed showed improvement in seed yield and seed quality parameters in the field. The present study has provided chemical and biological measures for the integrated management of lentil wilt.

It is critical to use a population of the pathogen that contains different strains to determine the resistance of grapevine varieties to the downy mildew pathogen Plasmopara viticola in a specific region. This study tested six local grape varieties (Çavuş, Kalecik Karası, Müşküle, Papaz Karası, Sultana and Yapıncak), eight Turkish registered varieties (Barış, Bozbey, Güzgülü, Özer Karası, Reçel Üzümü, Tekirdağ Çekirdeksizi, Trakya İlkeren and Yalova İncisi) and seven varieties of foreign origin (Cabernet Sauvignon, Cardinal, Chardonnay, Cinsault, Isabella, Semillon and Gamay) using detached leaf and leaf disc assays with pathogen populations collected from vineyards. There was a significant correlation for disease severity between the two assay methods. No sporulation was observed on the varieties Çavuş and Isabella in both assay methods. The variety Yapıncak had very low disease severity (2.00%) in the leaf disc assay, and the pathogen did not sporulate on this variety in the detached leaf assay. Cluster analysis was performed to determine the resistance level of the varieties against the pathogen, as different disease severities were observed in some varieties depending on the test method used, and the 21 varieties were classified into four clusters. Barış, Bozbey, Cardinal, Çavuş, Isabella, Semillon and Yapıncak in Cluster I exhibited the lowest disease severity mean (2.88%), while those in Cluster 3, including Cabernet Sauvignon, Güzgülü, Papaz Karası and Yalova Incisi, had the highest disease severity mean (56.75%). These varieties in Clusters 1 and 3 were considered highly resistant and highly susceptible, respectively. Leaf hair density, as reported in official variety descriptions, did not associate with reduced disease severity in the two assays. This study assessed the response of grapevine varieties to the P. viticola population in the region for the first time. The highly resistant and resistant varieties identified will provide new material for breeders and contribute to the improvement of organic viticulture in the area.