Abstract
Anthracnose, caused by Colletotrichum gloeosporioides, is one of the most important diseases in papaya fruit. Its control has been achieved with synthetic fungicides, but the application of marine bacteria and the sulphated polysaccharide ulvan (structural description: β[1,4]-D-GlcA-α[1,4]-L-Rha 3 sulfate, β[1,4]-L-IdoA-α[1,4]-L-Rha 3 sulfate, β[1,4]-D-Xyl-α[1,4]-L-Rha 3 sulfate, and β[1,4]-D-Xyl 2-sulfate-α[1,4]-L-Rha 3 sulfate) from Ulva sp. can be an alternative in the use of agrochemicals. Thus, the objective of this study was to assess the effect in vitro and in vivo of two marine bacteria, Stenotrophomonas rhizophila and Bacillus amyloliquefaciens, and ulvan in papaya fruit’s bio-protection against C. gloeosporioides. The capacity of marine bacteria to inhibit mycelial growth and phytopathogen spore germination in vitro through volatile organic compounds (VOCs) and carbohydrate competition was evaluated. Fruit was inoculated with bacteria, ulvan, and C. gloeosporioides and incubated at 25 °C and 90% of relative humidity (RH) for seven days. Disease incidence (%), lesion diameter (mm), and antioxidant defense enzyme activity (such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were quantified. In vitro, C. gloeosporioides was inhibited by S. rhizophila and B. amyloliquefaciens. In vivo, disease incidence and the lesion diameter of anthracnose on papaya fruit were significantly reduced by marine bacteria and ulvan. Antioxidant defense enzyme activity played an important role in fruit bio-protection against C. gloeosporioides. The application of marine bacteria and ulvan can be an alternative in the sustainable postharvest management of papaya.
Highlights
Worldwide, the loss of fruit at postharvest caused by phytopathogens is estimated to reach 50%of total production [1]
Synthetic fungicides constitute the main method of controlling anthracnose; the use of these agrochemicals generates resistance to phytopathogens, besides the adverse effects on the environment and human and animal health [5]
Data were processed by a Spore one-way analysisbyofUlvan variance (ANOVA) and Tukey’s test with a
Summary
The loss of fruit at postharvest caused by phytopathogens is estimated to reach 50%of total production [1]. Synthetic fungicides constitute the main method of controlling anthracnose; the use of these agrochemicals generates resistance to phytopathogens, besides the adverse effects on the environment and human and animal health [5]. Antioxidants 2019, 8, 580 biocontrol agents and the application of algae as resistance inductors in plants is an important option to reduce or replace agrochemicals [6,7]. The use of bacteria as biocontrol agents has been increasing because of their capacity to decrease diseases caused in fruit by fungi [8]. Antagonist bacteria are generally isolated from plants, fruit, or soil [9], but the isolation of antagonistic microorganisms in extreme environments has been studied little
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