Research Article Infection and colonization of common bean by EGFP transformants of <i>Fusarium</i> <i>oxysporum</i> f. sp. <i>phaseoli</i>

Abstract

Fusarium wilt caused by the fungus Fusarium oxysporum f. sp. phaseoli (Fop) is one of the most important diseases of common bean and occurs in many regions of the world. However, there is little available information that could elucidate when and where the fungus attacks common bean plants. To study the colonization of common bean by this fungus, we transformed Fop Brazilian race 2 for egfp gene expression and used these fungal transformants to analyze the colonization process in common bean roots and stems. The combined use of driselase and lysing enzyme was sufficient for Fop mycelium protoplastization. The PEG-CaCl 2 transformation protocol allowed us to obtain stable transformed fungi, with colonies expressing the egfp gene. Regarding colonization by Fop transformants, the fungus grew intercellularly on the root hair epidermis at six days post-inoculation (DPI) and on parenchymal ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 18 (4): gmr18370 R.O. Batista et al. 2 cells at 11 DPI on plants of the susceptible line. At 19 DPI, the fungus reached xylem vessels, blocking water and mineral passage in shoots, resulting in wilt and plant death at 25 DPI. Using fluorescence to mark the fungus revealed details of Fop colonization of common bean tissues.

Assessment of resistance in common bean to Fusarium oxysporum f. sp. phaseoli using different inoculation and evaluation methods

“…Because of these, the evaluation of the resistant bean lines to the fungus in field is difficult and time consuming. The previous selection of resistant bean to the fungus through artificial inoculation and subsequent validation of only the most resistant in the field is the most appropriate and quick way (Cavalcanti et al 2002, Batista et al 2019. Some methods for Fusarium inoculation are used to evaluate resistance in controlled environments (Cruciol and Costa 2017).…”

Fusarium wilt–common bean pathosystem: Pathogen variability and genetic control

“…Key phases include host root recognition and adsorption, penetration of hyphae through different root tissues, penetration and progression in the xylem, and adaptation to the plant's internal environment (Ma et al., 2013). In common bean, the Fop infection process begins at the tip of the roots, wounds, or natural openings or also presence of nematodes in the area, followed by colonization and obstruction of xylem vessels, consequently causing leaf wilting, vascular discoloration, progressive yellowing from lower to upper leaves, dwarfism, and premature plant death (Batista et al., 2019; Bianchini et al., 2005). In the field, wilting on diseased plants is not always visible (Bianchini et al., 2005).…”