Morphological, Molecular, and Pathogenic Characterization of Alternaria alternata Isolates from Apple

Morphological and molecular diversity of Alternaria porri isolates causing purple blotch disease in small onion across Tamil Nadu

The study highlights the substantial spatial, morphological and molecular variability present in A. porri populations associated with onion purple blotch in Tamil Nadu and provides valuable baseline information for disease surveillance, resistance screening and the development of effective management strategies.

Isolation, Molecular Characterization, and Biological Control of Fusarium solani Causing Stem Rot of Durian Tree in China

Findings establish F. solani as a causal agent of durian stem rot in Hainan and highlight the potential of Bacillus-based biological control as a sustainable strategy for disease management in durian production systems.

Isolation, Identification, and Pathogenicity of Alternaria alternata Associated with Apple Branch Canker in Al-Jabal Al-Akhdar Region, Libya

Apple (Malus domestica Borkh.) represents a major fruit crop of global economic importance. Despite its widespread cultivation, fungal diseases infecting branches and vegetative tissues continue to be a major concern, adversely affecting orchard productivity and compromising fruit quality. The present study investigated the fungal pathogen associated with branch canker symptoms observed in apple orchards located in the Al-Jabal Al-Akhdar region, Libya. Symptomatic branch samples exhibiting bark cracking, canker formation, and progressive dieback were collected and subjected to fungal isolation under laboratory conditions. Isolates were purified on potato dextrose agar (PDA) medium and identified according to morphological and microscopic characteristics using standard taxonomic keys. Pathogenicity assays were conducted on healthy apple seedlings to verify the causal relationship between the isolated fungus and disease development. Morphological observations demonstrated that the recovered isolate belonged to Alternaria alternata (Fr.) Keissl., characterized by dark olivaceous to brown colonies and multicellular conidia arranged singly or in short chains. Conidial dimensions ranged from 14.05–14.38 µm in length and 8.07–9.81 µm in width, with 2–8 transverse septa. Artificial inoculation induced typical symptoms, including bark necrosis, branch canker formation, chlorotic lesions, and progressive tissue collapse. Re-isolation from infected tissues successfully fulfilled Koch’s postulates. The findings confirm the pathogenic role of A. alternata in apple branch canker development under local environmental conditions. This study represents one of the first detailed reports concerning the occurrence and pathogenicity of A. alternata associated with apple branch canker in eastern Libya and provides baseline information for future epidemiological and disease management studies

Morphological, molecular, and pathogenic characterization of Quambalaria cyanescens associated with grapevine trunk decline in Tunisia

Characterization of Alternaria species associated with Alternaria leaf blight of mustard reveals the genetic toxigenic potential of Alternaria alternata

Alternaria leaf blight (ALB), caused by the Alternaria species complex, is an economic threat to mustard cultivation all over the world. In this study, 700 infected leaf samples were collected from 28 blocks across six districts of the Bundelkhand region, Uttar Pradesh, India. To assess the prevalence and distribution of Alternaria species, 28 representative isolates were selected for further study. Morphological traits separated the majority of the Alternaria isolates into three morphotypes corresponding to A. brassicae , A . brassicicola , and A . alternata , which cause leaf blight. The pathogenicity test revealed that 18 isolates were highly virulent, 6 isolates were moderately virulent, and 4 were less virulent. Molecular analyses of the 18 highly virulent isolates, based on the internal transcribed spacer (ITS) region and the Alternaria-specific Alt a1 marker , confirmed the presence of A. brassicae (6 isolates), A. brassicicola (3 isolates), and A. alternata (9 isolates) in the region. Haplotype network analysis of concatenated ITS and Alt a1 sequences revealed two haplotypes among the A. alternata isolates and one haplotype each among the A . brassicae and A. brassicicola isolates. Additionally, all virulent A . alternata isolates carried the polyketide synthase genes ( pksH and pksJ ), indicating their genetic potential for Alternaria toxin biosynthesis. The predominance of A . alternata in mustard crops and the presence of toxin-biosynthesis-associated genes may pose a threat to edible oil production and safety, thereby raising serious concerns and warranting further investigation of toxin production. These findings highlighted the need for targeted resistance strategies against the prevalent Alternaria species in the region.

Molecular Characterization of Botrytis cinerea Isolates from Different Host Plants

The presence of abnormally shaped colonies through a multi-faceted approach that included pathogenesis tests and ITS-rDNA sequencing to provide accurate identification of gray mold in strawberries (Botrytis cinerea) supports the feasibility of integrated management approaches that combine biological, phytochemical, and conventional fungicides for controlling gray mold in strawberries.