Strawberry Anthracnose control by Plant Essential Oils as Bio-fungicides, and their effects on Quality of Strawberry Fruit -

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Strawberry Anthracnose control by Plant Essential Oils as Bio-fungicides, and their effects on Quality of Strawberry Fruit

 

Colletotrichum nymphaeae is the causal agent of strawberry anthracnose. The application of the selected plant essential oil (EO) such as Mentha longifolia to the management of strawberry anthracnose disease under in vitro, in vivo, and greenhouse conditions. In vitro tests indicated that EO and fungicide were able to inhibit mycelial growth and conidial germination of the pathogen.  The severity of strawberry anthracnose disease was reduced by EO of Mentha longifolia under in vivo and greenhouse conditions and it also reduced weight loss and preserved firmness, ascorbic acid, total phenol, antioxidant activity (DPPH), and enzyme peroxidase activity in treated fruit. At the same time, it also preserved the sensory quality of strawberry fruit during the storage period so that there were no significant differences between treatments (EO) in their appearance, flavor, odor attributes, and overall evaluation compared to the control. Based on this it can be considered as excellent bio-fungicides for the management of strawberry anthracnose. It concluded that EOs effective on reduction of fruit decay during the storage period along with maintaining the physicochemical and sensory qualities of strawberry fruit.

Essential oil extraction

The Mentha longifolia was shade dried. Extraction of EO was carried out through Clevenger-type apparatus and hydrodistilled for 5 h using 300g of dried plant material. The extracted essentials oil was dried in anhydrous sodium sulfate and preserved in a sealed amber bottle at cool temperature. The The Bicyclo [3.1.1] hept-3-en-2-one, 4,6,6-trimethyl (43.412 %), cyclohexanone, 5-methyl-2-(1-methylethylidene)(– 35.391 %)  and eucalyptol (14.569 %) were identified as the major components of the M. longifolia EO by GC-MS analysis.

Effect of EOs on Hyphal growth and conidial germination

Mentha longifolia EO reduced the mycelial growth and conidial germination of C. nymphaeae in vitro to compare the fungicide of Captan and control in contact and vapor phases. The inhibition effect of mycelial growth was positively correlated with the concentration of EO. The results showed that EOs of M. longifolia (EC50=26.08 μL/L) appear to be more toxic than Captan fungicide (EC50=62.97 μL/L).  The results of the in vitro experiment indicated that all EOs strongly inhibited the conidial germination of C. nymphaeae after 48 h in both methods. In contact and vapour methods, the reduction of germinated conidial of C. nymphaeae was 79.2 % to 84.6 % and 67.2 % to 90 %, respectively, compared to the control. In the control treatment, spores of C. nymphaeae germinated and produced the germ tube that gradually developed to long hyphae. In the contact method, there was no significant difference in the treatment of M. longifolia and Captan. The EOs of A. millefolium had the most effect on reduction of conidial germination of the pathogen after 48 h in contact and vapor methods.

The disease index in control treatment after 10 days reached 4.75. The postharvest decay was significantly decreased when strawberry fruit was treated with M. longifolia EO was most effective with over 98.7% reduction in disease severity. Anthracnose, caused by C. nymphaeae, is the most aggressive disease of strawberry and limits good fruit quality.  The EO increased the phenolic compounds in plants and prevents the growth of pathogens as well as declining the severity of fruit decay. In greenhouse conditions, symptoms of anthracnose on petioles appeared 40 days after inoculation in control pathogen. EO and fungicides decreased the disease severity and increased control efficacy compared with the untreated control. Fungicide of Captan reduced the disease severity of 88.4 %. EO of M. longifolia was the most effective with over 92.4% reduction in disease severity. The weight loss of strawberry fruit in the treatments was not affected by EOs and increased gradually throughout the storage period. Fruit firmness is one of the most important quality deterioration characters during storage time, which is caused by the degradation of pectin in the fruit cell wall and hydrolysis of starch to sugar associated with fruit ripening. This study showed that EOs caused maintains vitamin C content in fruit during storage probably due to the antioxidant effects of EO. The total phenol was found in fruit treated with M. longifolia  209.30 mg/100 g, after 8 days of cold storage. The DPPH value of strawberry fruits in control treatment at end of storage period was 71.04 %.  M. longifolia EO (76.77 %) and Captan (76.04 %) gave the higher antioxidant values, respectively. During the whole storage period, a more rapid increase in POD activity was observed in all treatments.  POD is an important resistance-related enzyme in fruit as a plant defense mechanism and plays an important role during postharvest storage in the protection of fruits against postharvest disease.                                

 

Citation

Hosseni, S., Amini, J., Rafei, J.N. and Khorshidi, J., 2020. Management of strawberry anthracnose using plant essential oils as bio-fungicides, and evaluation of their effects on quality of strawberry fruit. Journal of Oleo Science, 69(4), pp.377-390.