Genomic analyses of Calonectria pteridis and standard area diagram sets for severity assessment of calonectria leaf blight

• Ano de defesa: 2022
• Autor(a) principal: Queiroz, Marcia Ferreira
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa; Fitopatologia
• Palavras-chave em Português: Fungos fitopatogênicos; Cylindrocladium pteridis; Mancha-de-calonectria; Eucalipto - Doenças e pragas; Genoma; Fitopatologia
• Link de acesso: https://locus.ufv.br//handle/123456789/31137; https://doi.org/10.47328/ufvbbt.2023.343

Calonectria leaf blight (CLB) caused by several Calonectria species represents a serious threat to the sustainability of commercial plantations and nurseries of Eucalyptus in worldwide. In Brazil, C. pteridis is the main causal agent of CLB in eucalyptus plantations. The selection and planting of resistant eucalyptus genotypes are the main strategies of control of this disease. A comprehensive understanding of biology, genetics and pathogenicity of Calonectria species, as well as assessing of disease severity accurately and reliably for screening of resistant eucalyptus clones are critical knowledge to an efficient management of CLB. Therefore, in chapter 1of this Thesis, we present de novo assembly of the nuclear genome of C. pteridis LPF059, which represents a baseline for further investigations. In chapter 2, we performed a comprehensive genomic analysis study that allowed us to maximize our understanding of genetics, lifestyle, reproduction, and pathogenicity of C. pteridis compared to other Calonectria species. The assembly of C. pteridis LPF059 genome shows a high completeness with a large set of coding sequences related to CAZymes and secondary metabolites. The size and gene content of the mitochondrial genome of Calonectria of C. pteridis LPF059 is comparable to the mitochondrial genome of other Calonectria species. Based on mating type genes C. pteridis is a heterothallic species. Calonectria henricotiae and C. pseudonaviculata are classified as mesotrophs and the other species in this study as vasculartrophs due to their differences in CAZymes content and therefore nutrient acquisition. In addition, Calonectria species considered as saprophytic - “apathogenic”- or broad host-range showed a higher content of pathogenicity/virulence-related genes than species that are narrow host-range, which indicates that the loss of certain genes may affected their ability to infect multiple plant host species. In chapter 3, we evaluated the effect of rater instruction and two standard area diagram sets (SADs), that varied on scale structure, on the accuracy and reliability of visual estimates of CLB severity. It was found that the instruction is critical for inherently less accurate raters and given the importance of visual assessment of disease symptoms, we recommend the use of amended-linear set for CLB severity assessment. This study maximizes our knowledge on the biology, genetics, lifestyle, evolution, and pathogenicity of C. pteridis compared to other Calonectria species, providing valuable genomics data for future investigations. Moreover, it improves our understanding of fundamental issues on development and usage of SADs, besides valuables SADs to be used on CLB severity assessment for screening of resistant eucalyptus clones. Keywords: Cylindrocladium pteridis. Genome sequencing. CAZymes. Lifestyle. Fungal pathogenicity. Diagrammatic scale rating. Disease resistance.