Importance of the early blight disease: Tomato is a globally important vegetable crop that faces numerous pathogenic threats throughout its growth period. Among these, early blight caused by Alternaria solani is a destructive disease that leads to significant losses for tomato growers across different seasons.Aim of the study: This study aims to understand the variation within the A. solani infecting tomato plants.Method: The fungus was characterized through phenomorphology and PCR identification utilizing markers such as ITS, SSU, LSU, and β-tubulin and genetic variation identified through Restriction Fragment Length Polymorphism (RFLP).Results: Roving survey indicated that during the vegetative stage, early blight severity ranged from 1.03 to 16.22%, while during the fruiting stage, it ranged from 16.11 to 52.89%. Furthermore, 23 isolates of A. solani were collected and identified from five districts in Karnataka, India. These isolates were identified based on micro-morphological evaluations, cultural characteristic assessments, and a multilocus gene analysis comprising four segments (ITS, SSU, LSU, and β-tubulin). The genetic variation among the isolates was investigated using RFLP analysis revealed polymorphism within the four segments (ITS, SSU, LSU, and β-tubulin) of the 23 Alternaria isolates.Conclusion: This study aims to investigate the genetic and pathogenic variability of Alternaria solani, the causal agent of early blight in tomatoes. By analyzing isolates collected from different regions and seasons and seeks to identify variations in virulence, genetic makeup, and fungicide resistance. These insights are crucial for developing effective disease management strategies and breeding resistant tomato varieties, thereby contributing to the sustainable control of this important pathogen.

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Resting cysts of dinoflagellates can persist in sediments, seeding harmful algal blooms (HABs). A DNA metabarcoding approach was employed, targeting the large subunit ribosomal (LSU D1–D2) and the internal transcribed spacer (ITS1) to investigate the diversity and biogeography of dinoflagellate cysts from the South China Sea to the Chukchi Sea. The LSU and ITS1 datasets identified 196 and 118 species, respectively, with only 59 dinoflagellate cyst species revealed by both approaches. Eleven cyst species of potentially toxic dinoflagellates and 82 species previously unknown as cyst producers were detected. Cysts of Heterocapsa cf. horiguchii, Heterocapsa minima, Heterocapsa iwatakii, Heterocapsa rotundata, and Heterocapsa steinii were documented through germination for the first time, with the latter three species also detected via metabarcoding. This study provides critical insights into the diversity and biogeography of dinoflagellate cysts by highlighting the complementary detection capabilities of LSU and ITS1 molecular markers and their trans-latitudinal distribution patterns. The identification of potentially toxic cysts and their ecological distributions offers crucial information on the ecology of harmful dinoflagellates. These findings underscore the importance of molecular techniques in monitoring dinoflagellate cysts.