Journal of Phytopathology最新文献

Leaf blight was detected on potted blood lily (Scadoxus multiflorus) plants in a garden located in Andhra Pradesh, India. Pycnidia resembling a Lasiodiplodia species were consistently detected on the foliage of symptomatic plants. Based on morphology, cultural features and molecular analysis, the species was identified as Lasiodiplodia theobromae. Koch's postulates were fulfilled by pathogenicity tests carried out on potted blood lily plants. To the best of our knowledge, this is the first report of the occurrence of a disease caused by L. theobromae on S. multiflorus.

Banana (Musa acuminata Cavendish Subgroup) cultivation plays a pivotal role in Vietnam's economy. However, the presence of postharvest diseases poses significant challenges as they adversely affect the quality and market value of the crop. The objective of this study was to identify the microbial strains responsible for these diseases through phylogenetic analysis and morphological characterisation. Four fungal isolates including Colletotrichum musae, C. gloeosporioides, Fusarium musae and Lasiodiplodia theobromae were identified as the primary causal agents of fruit rot in postharvest bananas. Re-infection tests, which were conducted following Koch's postulates on banana samples, confirmed the isolates' significant pathogenicity, leading to weight loss, colour alteration, firmness reduction and acidity changes in the fungal-infected bananas. These findings hold profound implications for enhancing our understanding of banana diseases in the postharvest stage, which can contribute to the development of effective control measures and mitigation strategies in the future.

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.