Molecular, Histological and Histochemical Responses of Banana Cultivars Challenged with Fusarium oxysporum f. sp. cubense with Different Levels of Virulence

Abstract

Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) is the most limiting factor in the banana agribusiness worldwide. Therefore, studies regarding pathogen attack mechanisms, and especially host defense responses, in this pathosystem are of utmost importance for genetic breeding programs in the development of Foc-resistant banana cultivars. In this study, analysis at the molecular, histological and histochemical levels of the Musa spp. x Foc interaction was performed. Three Foc isolates representative of race 1 (R1), subtropical race 4 (ST4) and isolate 229A, which is a putative ST4, were inoculated in two Prata-type cultivars (Prata-Anã and BRS Platina) and one cultivar of the Cavendish type (Grand Naine). Of seven genes related to plant–pathogen interactions, five were overexpressed in ‘BRS Platina’ 12 h after inoculation (HAI) with Foc R1 and ST4 but had reduced or negative expression after inoculation with Foc 229A, according to RT–qPCR analyses. While hyphae, mycelia and spores of the Foc 229A isolate grow towards the central cylinder of the Grand Naine and Prata-Anã cultivars, culminating in the occlusion of the xylem vessels, the BRS Platina cultivar responds with increased presence of cellulose, phenolic compounds and calcium oxalate crystals, reducing colonization within 30 days after inoculation (DAI). In general, these data indicate that the cultivar BRS Platina has potential for use in banana-breeding programs focused on resistance to Foc tropical race 4 (TR4) and in aggregating information on the virulence relationships of the Foc pathogen and the defense responses of banana plants after infection.

Expression of SIX1b and SIX1c effector genes and banana resistance genes during Foc TR4 infection on banana cultivars

“…The higher expression of PR-protein 1 in this experiment was parallel to previous research (Subramaniam et al 2006;Li et al 2015), proving it as one prominent feature of plant defense responding to biotic stress. It was one of the cell wall degrading enzymes in addition to PR3 and PR10, digesting the major components of chitin or glucan in fungi cell walls for inhibiting fungal growth.…”

“…These could be potential genes for developing resistant banana cultivars against Foc TR4. Rocha et al (2022) showed that the chitinase gene was more highly expressed in the BRS Platina cultivar than in the Prata-Anã and Grand Naine cultivars at 12 hours after inoculation, which may be closely related to the resistance of this cultivar in the early stage of infection of Foc. It showed that the prevalence of chitinase was a potential gene for resistance genes.…”

The Advance of Fusarium Wilt Tropical Race 4 in Musaceae of Latin America and the Caribbean: Current Situation

“…Additionally, research to develop resistant varieties [ 21 ] and improve soil management practices is also ongoing [ 22 ]. Undoubtedly, this disease constitutes a real and particular threat to the livelihoods of small- and medium-sized banana producers in LAC, who mostly lack the economic means to develop measures against yield loss along with the increase in yield production costs [ 23 , 24 , 25 ].…”