Physiological effects of the hydrophilic phytotoxins produced by Mycosphaerella fijiensis, the causal agent of black sigatoka in banana plants

Abstract

Although Mycosphaerella fijiensis, the causal agent of black sigatoka disease of banana, has been known to produce numerous lipophilic host-selective (HSTs) and nonhost selective phytotoxins (non-HSTs), only recently we have reported that the pathogen also produces hydrophilic phytotoxins. Here we examined the effect of light on the toxicity of the hydrophilic phytotoxins and estimated the electrolyte leakage and H 2 O 2 and superoxide generation in detached banana leaves to study their mode of action at the cellular level. Nonhost plant species were also tested to determine whether the toxins are HSTs or nonHSTs. Our results suggest that the hydrophilic phytotoxins are non-HSTs, that their phytotoxicity is not light dependent, and that they may act at the plasma membrane by altering permeability through oxidative damage, by inducing ROS production as part of their mechanism of action.

The hemibiotrophic lifestyle of the fungal pine pathogen Dothistroma septosporum

“…; Cruz‐Cruz et al. ), and Z. tritici is also predicted to produce phytotoxic metabolites (Orton et al. ).…”

“…In other fungi with hemi-biotrophic life styles such as Z. tritici (Keon et al 2007) and M. fijiensis (Kantun-Moreno et al 2013) fungal biomass also increased significantly in the necrotrophic phase, and this was associated with loss of host cell membrane integrity and electrolyte leakage. Mycosphaerella fijiensis produces phytotoxins and secreted proteins that result in damage to host tissue (Chuc-Uc et al 2011;Cruz-Cruz et al 2011), and Z. tritici is also predicted to produce phytotoxic metabolites (Orton et al 2011).…”

Ketahanan Kultivar Pisang Lokal Kalimantan Selatan terhadap Penyakit Bercak Sigatoka (Mycosphaerella sp.)

“…Pada kultivar agak tahan seperti Kepok, Mauli, Mas Bantan dan Talas, toksin ini berkontribusi terhadap perluasan lesio (nekrosis) (Harelimana et al 1997). Toksin (5-hydroxy-1,4-naphthoquinone) dari M. fijiensis berperan penting dalam perkembangan gejala bercak daun karena menghambat fungsi kloroplas dalam transfer elektron (Busogoro et al 2004); fitotoksin bersifat tidak spesifik inang (Cruz-Cruz et al 2011). Lepoivre et al (2003) menjelaskan pada interaksi tanaman pisang dengan M. fijiensis yang tidak kompatibel (reaksi tahan) karena kematian sel penjaga stomata terjadi diawal, dan terjadi penumpukan senyawa dengan elektron yang padat mengelilingi tempat infeksi.…”

Prospecção de obstáculos à bananicultura sustentável

“…Condições de sombra são popularmente conhecidas como causadoras de menores severidades de sigatoka. Estudos recentes comprovaram que a fitotoxina produzida pelos agentes causadores das sigatokas são ativadas pela luz (CRUZ-CRUZ et al, 2010).…”