Monocyclic Components and Photosynthetic Damage Caused by Myrtle Rust in Guava Leaves

Autor(es)

Goncalves, Manoel Penachio ; Nogueira Junior, Antonio Fernandes ; Ribeiro, Rafael Vasconcelos ; Amorim, Lilian

• Tipo de documento: Artigo Científico
• Fonte: PHYTOPATHOLOGY; v. 112, n. 7, p. 9-pg., 2022-05-26.

Resumo

Austropuccinia psidii, the causal agent of myrtle rust, was, for many years, restricted to the Americas, but since reaching Hawaii in 2005, the pathogen has expanded its global range exponentially. In Brazil, myrtle rust is the main fungal disease in guava plants. Despite this, there are few studies on guava rust epidemiology. The objectives of this study were to quantify the monocyclic components of rust and to evaluate the photosynthetic damage caused by A. psidii in young and old leaves of 'Paluma' guava. The monocyclic components of guava rust and gas exchange in healthy or inoculated (10(5) ml(-1) urediniospores of A. psidii) leaves were quantified over time. Additionally, young leaves were inoculated with varying concentrations of A. psidii inoculum, and leaf gas exchange and chlorophyll fluorescence were measured at 25 days postinoculation. The relationship between the relative CO2 assimilation of a diseased leaf (P-x) and a healthy leaf (P-o) is related to disease severity (x) by P-x/P-o = (1 - x)(beta). The density of lesions, disease severity, and urediniospore production were high in young leaves, averaging 58 lesions cm(-2), 50% leaf area diseased, and 2.5 x 10(4) urediniospores per lesion, respectively. Rust symptoms were not observed in old leaves, and resistance to infection did not cause any photosynthetic cost to these leaves. On young leaves, beta was 2.13, indicating a reduction on CO2 assimilation at green tissues from symptomatic leaves. Our data revealed that photosynthesis reduction in diseased guava leaves was caused by biochemical and photochemical damage rather than by stomatal limitation. (AU)

• Processo FAPESP: 19/13191-5 - Componentes epidemiológicos, caracterização de danos e controle de ferrugens tropicais e temperadas em cenário de mudança climática global
• Beneficiário: Marcel Bellato Spósito
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 19/20409-7 - Impacto da limitação hídrica na ferrugem da goiabeira: componentes monocíclicos e fotossíntese da planta
• Beneficiário: Manoel Penachio Gonçalves
• Modalidade de apoio: Bolsas no Brasil - Mestrado