Diversidade molecular de fungos em lesões de ferrugem alaranjada da cana-de-açúcar

Abstract

Sugarcane (Saccharum spp.) is a crop of great importance both globally and nationally. However, one of the limiting factors for this crop has been the presence of phytopathogens in producing areas, affecting plant health and causing low productivity. Among the main diseases affecting sugarcane, orange rust stands out due to the high destructive capacity of its pathogen. Orange rust is caused by the basidiomycete Puccinia kuehnii, which was first reported in Brazil in 2009. The use of resistant cultivars has been the most widely used control method for orange rust in sugarcane fields. This strategy has been adopted in Brazil, but the breakdown of resistance in previously classified resistant cultivars shows that the efficacy of this method is limited and requires a better understanding of the molecular evolution of this pathogen. The objective of this study was to conduct a phylogenetic analysis of the fungus Puccinia kuehnii and other associated fungi, aiming to understand the molecular diversity of these organisms. Leaves with symptoms of orange rust were collected, and the spores present in the lesions were subjected to DNA extraction and ITS region amplification via PCR, followed by sequencing using the Sanger method. Phylogenetic analyses were conducted using probabilistic approaches, generating consensus trees with 10 million generations in the MrBayes program, visualized and edited in FigTree. The results revealed the presence of three fungal species in the orange rust lesions: Puccinia kuehnii, Sphaerellopsis paraphysata, and Hyweljonesia queenslandica. The phylogenetic analysis indicated significant molecular diversity among the P. kuehnii isolates, highlighting the need to collect samples from at least three distinct points, as sampled in this study, to represent the fungus's variability. Additionally, the identification of Sphaerellopsis paraphysata in the lesions reinforces its potential use in the biological control of orange rust, while the presence of Hyweljonesia queenslandica, still poorly documented in the literature, highlights the need for further studies to elucidate its ecological role and potential impact on sugarcane cultivation.