A comparative study of raspberry structural and biochemical responses to late leaf rust

Author(s)

Marcia Gonçalves Dias

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2023-03-07

Examining board members

Beatriz Appezzato da Gloria; João Paulo Rodrigues Marques; Douglas Rodríguez Martínez; Paulo Jose Pereira Lima Teixeira

• Advisor: Beatriz Appezzato da Gloria; Marcel Bellato Sposito

Abstract

Rosaceae is a family composed of important crops such as apple, peach, strawberry, and raspberry. Among these species, red and black raspberries belong to the genus Rubus and are high-value crops with increasing worldwide demand. However, these plants are affected by several diseases that impact their quality and productivity. Late leaf rust is a fungal disease in raspberries caused by Aculeastrum americanum (Farl.) M. Scholler & U. Braun (syn. Thekopsora americana (Farl.) Aime & McTaggart). While red raspberries (Rubus idaeus L.) are susceptible, black raspberries were previously reported as more resistant (R. occidentalis L.) and immune (R. niveus Thunb.) to this pathogen. Since genetic resistance is a promising way to manage this disease, hybridizing red and black raspberries can provide new cultivars with interesting traits. However, it is important to understand how plants respond to pathogens before developing expensive and long breeding programs. The aim of this thesis was to investigate the histopathological and biochemical responses of red and black raspberries and a hybrid between them to A. americanum colonization. It was observed that the pathogen germinated and colonized all studied raspberries, however, black raspberries and the hybrid had distinctive responses compared to R. idaeus. The compact mesophyll, the pre- and post-formed phenolic compounds, post-formed pectic compounds, and cell collapse in the lesioned area were the main defense mechanisms against A. americanum. Additionally, to structural and biochemical studies of raspberries defense responses, it was performed a comparative genomics analysis to identify the calcium-dependent protein kinases (CDPKs), focusing on the CPK28 orthologs in black raspberry (R. occidentalis) and strawberry (Fragaria vesca L.) as representative of Rosaceae. Both have 26 CDPKs together. The orthologs FvCPK28 and RoCPK28 were cloned and expressed in Nicotiana benthamiana and Arabidopsis cpk28 mutants. It was found that both Rosaceae CPK28 orthologs are plasma-membrane localized, and their overexpression dampened the oxidative burst upon elicitation. These results provided a proof-of-concept to investigate the functional similarities between these proteins and Arabidopsis CPK28. (AU)

• FAPESP's process: 18/17428-7 - Anatomical and biochemical comparison among raspberry species (Rubus spp.) with different resistance levels to late leaf rust (Pucciniastrum americanum)
• Grantee: Márcia Gonçalves Dias
• Support Opportunities: Scholarships in Brazil - Doctorate