Alternaria is a widespread genus and a diverse taxonomic group of fungi, whose members exhibit a wide range of ecological roles, from endophytes and saprophytes to potent plant pathogens, and in some cases, to opportunistic pathogens or allergens affecting humans. Their high adaptability to various environmental conditions determines their widespread distribution and resilience. A key feature of the genus Alternaria is its substantial species diversity. According to the Species Fungorum database, it currently comprises 792 registered species, which are grouped into 29 sections. It should be noted that this number reflects the current state of taxonomic classification and is subject to ongoing revision. The ecological role of representatives of this genus is particularly relevant in the context of agriculture, as many species are pathogens and causative agents of Alternaria leaf spot in important agricultural plants such as tomatoes, potatoes, apples, wheat, and others. This disease causes significant economic losses. At the same time, some strains demonstrate potential for use in biotechnology due to their ability to produce biologically active metabolites. This review examines the taxonomy, morphological characteristics, ecological role, pathogenicity, and control methods of fungi of the genus Alternaria, as well as their biotechnological potential.

Alternaria blight, caused by fungi of the genus Alternaria, is one of the most common and damaging diseases affecting tomatoes, leading to significant yield losses. The intensive use of chemical fungicides faces the problems of pathogen resistance development and negative environmental impacts. This study investigated the possibility of using RNA interference technology based on exogenous double-stranded RNAs (dsRNAs) to protect tomatoes against the causal agent of early blight (EB), Alternaria alternata. Key genes of the pathogen A. alternata were selected as targets: Alt-a1 (a major allergen and virulence factor), TEF1a (translation elongation factor 1-alpha) and β-Tub (β-tubulin). Specific dsRNAs were synthesized in vitro and applied to tomato plants (Solanum lycopersicum L. cv. Micro-Tom) simultaneously with inoculation of A. alternata strain C7.24-T2-L-F1 spores. Visual assessment, measurement of chlorophyll A and B, and real-time quantitative PCR analysis showed that treatment with dsRNAs targeting the Alt-a1, TEF1a and β-Tub genes significantly suppressed infection development, reducing the amount of pathogen DNA in plant tissues by 7 to 27 times depending on the dsRNA type. The most effective was dsRNA to the Alt-a1 gene. Thus, the obtained results demonstrate the promise of spray-induced gene silencing (SIGS) as a strategy for protecting tomato plants against the pathogen A. alternata.

Exogenously induced RNA interference (exoRNAi) is a powerful biotechnology tool for precise gene regulation. The plant chalcone synthase (CHS) gene serves as a valuable model for molecular biology due to its central role in flavonoid biosynthesis. However, there are currently very few studies addressing the advantages and disadvantages of in vitro (enzymatic) or in vivo (bacterial) methods for producing double-stranded RNA (dsRNA) for exogenous application. This study aims to optimize and compare the two methods for producing dsRNAs targeting the Arabidopsis thaliana CHS gene: enzymatic synthesis in vitro using a commercial kit and bacterial synthesis in vivo using an engineered E. coli HT115 (DE3) system. Bacterial synthesis conditions were optimized with respect to IPTG concentration and cultivation time, and the resulting dsRNA preparations were purified and quality-controlled. Their biological activities were assessed by treating A. thaliana plants and analyzing the effects on AtCHS gene expression and flavonoid production using qRT-PCR and HPLC-MS. The results demonstrated that purified AtCHS-dsRNA from both methods effectively suppressed AtCHS expression and downstream flavonoid biosynthetic gene expression, leading to significant reductions in anthocyanins and flavanols. This study confirmed the efficacy of exogenous dsRNAs in regulating plant metabolic pathways and provided a comparative analysis of dsRNA synthesis methods, highlighting their benefits and limitations for practical applications in plant biology and protection.