In vitro antimicrobial activity and alternative control of anthracnose in papaya

Abstract

We evaluated the efficacy of natural products in the control of papaya anthracnose, in vitro and in vivo. The in vitro experiments for evaluation of mycelial growth used a completely randomized 10 × 4 factorial design (treatments × evaluation periods) with eight replicates, with sporulation evaluated at the end of the experiment. The treatments involved the use of aqueous extract at concentrations of 5 and 15% for Syzygium aromaticum (L.) Merr. & Perry (clove), Cinnamomum zeylanicum Breym (cinnamon), and Zingiber officinalis Rox. (ginger); 1 and 3% chitosan; the fungicide Prochloraz at 100 µg.mL-1; and a control (no treatment). For evaluating conidia germination, we used six treatments with five replicates. The treatments included 7.5% of each extract (clove, cinnamon, and ginger), 1.5% chitosan, and 50 µg.mL-1 of Prochloraz. For the in vivo experiment, “Formosa” papaya “Tainung 1” was used in a completely randomized design, with six treatments and four replicates to evaluate the severity of anthracnose caused by Colletotrichum gloeosporioides. The fruits were treated by immersion for 5 min with 15% clove, cinnamon, and ginger extracts, 8% chitosan, and control with distilled water, and immersion for 2 min in Prochloraz (33.75 g a.i./100 L). The treatments with 15% clove extract and 8% chitosan were effective in all evaluations, resulting in a viable alternative to the fungicide Prochloraz. The treatments with ginger extract were less effective and those with cinnamon offered intermediate control.

Postharvest conservation of Formosa ‘Tainung 1’ papaya under refrigeration, modified atmosphere, and chitosan

“…1a). The highest fungicidal action of chitosan 4%, according to KUMAR et al (2020), and of the second prochloraz (REIS et al, 2018) consists of inhibiting the action of microorganisms in tissues, resulting in delayed senescence, reduced respiratory activity and gas diffusion, and consequently in lower ML. For fruits with film, there were no significant differences between treatments due to the ability of the plastic film to reduce ML (Fig.…”

“…For chitosan, this result is attributed both to its ability to reduce water loss through transpiration (PETRICCIONE et al, 2015), and to its antifungal and antibacterial ability (KUMAR et al, 2020). For the prochloraz treatment, the result is also due to the antimicrobial action since REIS et al (2018) verified, in vitro, that the fungicide prochloraz 100 μg•mL -1 provided 100% inhibition of mycelial growth of Colletotrichum gloeosporioides.…”

“…To preserve the quality of such fruits and avoid postharvest losses, phytosanitary treatments control postharvest diseases through hydrothermal treatment concomitantly with the application of fungicides, waxes and plastic films that delay fruit senescence. This makes it possible to prolong postharvest shelf life, especially when associated with refrigerated storage at 10 ± 2 °C and 90% relative humidity (RH) (REIS et al, 2018).…”

“…Although the use of fungicides is an important control strategy, residues of these products in fruits have been a matter of concern due to the damage they may cause to human health and to the environment. As an example, despite the proven efficacy in the literature of the fungicide prochloraz (TAVARES; SOUZA, 2005;REIS et al, 2018), the Brazilian National Health Surveillance Agency (ANVISA), in 2016, prohibited the use of this active ingredient in pesticide products as a result of ANVISA's toxicological reassessments according to guidelines and toxicological assessment requirements adopted (ANVISA, 2016;REIS et al, 2018). European fruit importers have also expressed concern about chemical residues in fruits.…”