Journal of Phytopathology and Pest Management 10(1): 26-36, 2023

pISSN: 2356-8577 eISSN: 2356-6507

Journal homepage: http://ppmj.net/

∗Corresponding author: Yeşim ER,

E-mail: y_err@hotmail.com

26

In vitro and in vivo antifungal activity of microalgal treatments

against Alternaria brassicicola

Yeşim ER

Istanbul Directorate of Agricultural Quarantine, Department of Plant Pathology, Istanbul, 34149, Turkey

Abstract

Keywords: Alternaria brassiciola, cabbage, mustard, microalgae, antifungal activity.

Commercial preparations of three algal species (Arthrospira platensis, Chlorella

vulgaris, and C. pyrenoidosa) were evaluated according to in vitro (paper disc

method), and in vivo (seed, foliar, seed+foliar treatments) assays to determine the

antifungal activity against Alternia brassicicola. For in vitro assays, the extracts of

A. platensis, C. pyrenoidosa, and C. vulgaris showed the highest antifungal activity,

inhibiting the growth of A. brassicicola at a concentration of 50 mg/ml with

inhibition zones of 4.9, 4.2, and 3.9 cm, respectively. For in vivo assays, the

microalgal suspensions were observed to have remarkable antifungal activity at

increasing concentrations against A. brassicicola compared with control

treatments. Particularly, the seed+foliar treatment of a mixture of the microalgal

suspension (A. platensis+ C.vulgaris+ C. pyrenoidosa) at a concentration of 15 g/l

demonstrated the highest antifungal activity with an inhibition rate above 98% in

cabbage (Brassica oleracea) and mustard (Brassica juncea). The present study

confirmed that the microalgae treatments had a significant potential, as an

applicable and eco-friendly tool against A. brassicicola, to reduce exposure and

risks of chemical pesticides.

ER Yeşim, 2023

27

1. Introduction

The diseases caused by plant pathogenic

bacteria and fungi give rise to remarkable

losses in crop yield and unavoidable product

damages worldwide (Avelino et al., 2015).

Brassica spp. are broadly cultivated major

vegetable crops, which include many cultivars

distributed throughout the world. The

production of Brassica vegetables is affected

by the presence of various plant pathogens

which cause especially foliar diseases and huge

economic losses. Alternaria black leaf spot

caused by Alternaria brassicicola is the most

destructive disease of Brassica spp. worldwide

and widespread in many countries (Meena et

al., 2016; Kumar et al., 2014; Reis and

Boiteux, 2010). Typical disease symptoms

include black necrotic lesions encircled by

chlorotic areas on leaves, seedlings, stems, and

siliquae causing a serious decrease in yield

quantity and the production of high-quality

seeds (Ahmad and Ashraf, 2016; Saharan et al.,

2016; Iacomi-Vasilescu et al. 2004). Brassica

vegetables could be affected at all developmental

stages. The pathogen could remain alive for

several years in crop residues and could be

disseminated from the sources of incoculum to

neighbor fields or long distances (Yadav et al.,

2014; Kohl et al., 2010). Recently, use of

chemical pesticides against plant diseases is

considered as the most effective method. The

control of A. brassicicola is suppressed using

several different families of fungicides including

benzimidazoles, carbamates, dicarboximides, and

triazoles as seed or foliar treatments in many

countries. However, chemical pesticides,

which are used to control A. brassicicola, can

be easily absorbed by soil, causing pollution of

food crops and a toxic effect on non-target

populations (Satapute et al., 2019; Fox et al.,

2007;). Besides, emergence of resistant strains

of the pathogen as a result of long-term use of

pesticides is a serious problem and another

disadvantage. So, there is a rising demand to

accelerate and improve new management

strategies to ensure better disease control.

Studies of the use of natural origin preparations

on pest control have carried a great importance

because of unconscious and overuse of

chemical pesticides. In this manner, the

microalgae-based products including Arthrospira

spp. and Chlorella spp. can be a feasible alternative

in plant disease management (Ronga et al., 2019).

The antimicrobial activity of microalgae has

been associated with bioactive compounds

belonging to different chemical groups such as

terpenes, phytohormones, phenols, fatty acids,

etc. (Singh et al., 2017). Previous studies

indicated that Chlorella pyrenoidosa (Abd Elhafiz

et al., 2015), Chlorella vulgaris (Dineshkumar et

al., 2019; Özdemir et al., 2016), and Arthrospira

platensis (Dineshkumar et al., 2019; Anitha et al.,

2016) include a broad range of bioactive

compounds, which could improve the growth

and yield potential of crop plants in

overcoming pathogenic attack and could

activate plant defense mechanism that is

characterized as induced resistance (IR) in a

wide range of cultivated plants (Calvo et al.

2014; Khan et al. 2009). Although many

commercial products obtained from

microalgae were reported against several

phytopathogenic fungi such as Aspergillus

niger, Aspergillus flavus, Cercospora beticola,

Sclerotinia sclerotiorum, S. minor, Sclerotium

rolfsii, Fusarium oxysporum, F. roseum, F. solani,

F. verticillioides, Penicillium expansum, Rhizoctonia

solani, Alternaria dauci, A. solani, Verticillium albo-

atrum, etc. (Vehapi et al., 2020; Al-ghanayem,

2017; Abdel-Kader and El-Mougy, 2013), they

have received little attention as potential

agents for plant diseases. The present study

aimed to evaluate the antifungal activity of

Arthrospira platensis, Chlorella vulgaris, and

Chlorella pyrenoidosa, applied at certain

concentrations, against Alternaria brassicicola

in cabbage and mustard plants.

2. Materials and methods

2.1 Material

In the present study, three algal species in the

form of a dry powder (Arthrospira platensis,

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Chlorella vulgaris, and Chlorella

pyrenoidosa) were purchased as 100% pure

and assured commercial preparations. A.

brassicicola was isolated from the infected

samples showing black spot symptoms on

leaves in commercial fields. Potato dextrose

agar (PDA) medium was used for isolation and

cultivation of the pathogen. The seeds of the

cabbage (Brassica oleracea) and mustard

(Brassica juncea) were purchased and used to

determine antifungal activity of the microalgae

treatments against A. brassicicola. The study

was maintained in vitro and in vivo assays

(foliar, seed, seed + foliar treatments) at 5

different concentrations. In vivo experiments

were performed using 30 samples of the

susceptible cabbage and mustard seeds per

polyethylene pot (25 × 20 cm diameter)

containing 150 g sterile peat.

2.2 Isolation, identification and pathogenicity

of the fungal isolates

The seed samples were disinfected by 1%

sodium hypochlorite solution (SHS) for 5 min

and rinsed 3 times with sterile distilled water

(SDW). After drying process on sterile filter

paper, the seeds were placed in PDA plates and

incubated at 25°C for 7 days. After incubation

period, the fungal isolates were purified by a

single spore technique and kept at -10°C

throughout the study. The purified isolates

were identified according to colony appearance,

conidial morphology, microscopic and

pathological properties (Aneja et al., 2014;

Bessadat et al., 2014). The pathogenicity of 3

isolates of A. brassicicola was pre-assessed on

the basis of diseased leaf area on cabbage and

mustard cotyledons. The fungal isolates were

applied to cotyledons 1 week after sowing; the

plants were kept moist for 48 h and grown

under plant growth room conditions (at 25 ºC,

16 hrs of photoperiod) for 4-5 days and then

disease symptoms were observed to detect the

most pathogenic fungal isolate for in vitro and

in vivo experiments (Kubota et al., 2006).

2.3 Determination of the antifungal activity

of the microalgae extracts in vitro

After the dried microalgae powders were

extracted overnight in methanol (Starr et al.,

1962), they were tested using standard paper

disc method. Six mm diameter discs were

prepared using sterile Whatman No.1 filter

paper. The discs were saturated with 20 μl of

microalgae extracts (Arthrospira platensis,

Chlorella vulgaris, and Chlorella pyrenoidosa) at

different concentrations (10 mg/ml, 20 mg/ml,

30 mg/ml, 40 mg/ml, and 50 mg/ml) to

evaluate their antifungal activity against A.

brassicicola. The disks were placed in the

center of the agar surface containing a

pathogen inoculum at a concentration of 1×105

conidia/ml. After an incubation period at 25°C

for 7 days, the diameter of inhibition zones

formed around the paper disc was measured to

determine the antifungal activity as a result of

the average of 5 independent replicates. The

microalgae-free PDA medium, containing

only SDW and a culture disk of the pathogen,

was used as a control.

2.4 Determination of in vivo antifungal activity

of the microalgae extracts on Alternaria black

leaf spot

To determine the antifungal activity of

microalgae treatments against A. brassicicola,

the suspensions of A. platensis, C. vulgaris, C.

pyrenoidosa, and a mixture suspension of the

microalgae (A. platensis + C. vulgaris + C.

pyrenoidosa) were examined as the foliar,

seed, and seed + foliar treatments at

concentrations of 3 g/l, 6 g/l, 9 g/l, 12 g/l, and

15 g/l. The plant seeds were disinfected with a

1% SHS for 5 min and rinsed three times with

SDW before the microalgae treatments. After

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disinfection process, inoculated seeds of

susceptible cabbage and mustard plants at a

concentration of 1×105 conidia/ml were sown

in experimental pots (22 × 15 cm diameter)

containing a sterile peat and were grown in the

plant growth room conditions. When plants

reached 7-day-old after sowing, the microalgal

suspensions were sprayed as a foliar treatment

separately to upper and lower surfaces of

cabbage and mustard cotyledons with a dose-

adjusted spray. After microalgae treatments

were allowed to dry on cotyledons

(approximately 1-2 h), the treated plants were

kept under polyethylene bags for 48 h and then

moved to a plant growth room (Sabry et al.,

2015). To determine the antifungal activity of

the seed treatments against Alternaria black

leaf spot in cabbage and mustard plants, the

seeds were immersed for 10 min in microalgal

suspensions at different concentrations and

allowed to dry overnight. The following day,

the pathogen inoculum at a concentration of

1×105 conidia/ml was applied to the seeds

before sowing in pots. The pots were watered

and placed in a growth room (Amein et al.,

2011). In addition to that, seed + foliar

treatment of microalgae suspensions was

examined to evaluate the antifungal activity

according to the same procedure as seed and

foliar treatments. The cabbage and mustard

seeds were immersed for 10 min in microalgal

suspensions at different concentrations and

allowed to dry overnight. Afterwards, the

pathogen inoculum was applied to the seeds

before sowing in pots. When the seedlings

reached 7-day-old after sowing, the microalgal

suspensions were sprayed onto cotyledons as a

foliar treatment. After allowing to dry on

cotyledons for 1-2 h, the treated plants were

incubated under growth room conditions. The

experiment was conducted in a plant growth

room under a 16 h photoperiod cycle at 25 ºC

with an average of 5 independent replicates.

The microalgae-free pots, containing only

SDW and a spore suspension of the pathogen

(1×105 conidia/ml), were used as a control.

The disease severity on cabbage and mustard

plants was determined after 3 weeks following

inoculation process. The disease severity on

seedlings was rated and assessed according to

percentage of diseased cotyledons using 0 to 5

scale (0 = no disease, 1 = 1-10%; 2 = 11-25%;

3 = 26-50%; 4 = 51-75%; 5 = > 76%) (Verma

and Saharan, 1994). The disease severity (DS)

was calculated by using the formula given by

El-Morsi et al. (2009):

D.S (%) = (Σ (n × v)/ N × V) × 100

Where: DS=Disease severity, n = Number of

diseased cotyledons in each category, v =

Numerical value of each category, N = Total

number of assessed cotyledons, V = Maximum

numerical value.

The effect of the microalgae treatments on

Alternaria brassicicola was evaluated on the

basis of disease severity using the following

formula (Topps and Wain, 1957):

I %= [(C-T/C)] × 100

Where: I % = Inhibition rate, C = Disease

severity in control treatment, T = Disease

severity after microalgae treatments.

2.5 Statistical analysis

The obtained data were statistically analyzed

by ANOVA (one-way analysis of variance).

Significant differences (p<0.05) between the

means were evaluated by using the Duncan's

Multiple Range Test (DMRT) for the diameter

of inhibition zone of the microalgae extracts

and for disease severity of the pathogenic

isolate after in vivo assays.

ER Yeşim, 2023

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3. Results

The extracts of Arthrospira platensis,

Chlorella pyrenoidosa, and Chlorella vulgaris

demonstrated the highest antifungal activity,

inhibiting the growth of A. brassicicola at a

concentration of 50 mg/ml with inhibition

zones of 4.9, 4.2 and 3.9 cm, respectively. The

lowest antifungal activity was observed at a

concentration of 10 mg/ml against pathogen

with inhibition zones of 1.1, 1.6 and 2.2 cm for

C. vulgaris, C. pyrenoidosa, and A. platensis,

respectively under in vitro conditions (Figure

1). Namely, the increment of the inhibition

zones was observed at increasing concentrations

compared to lower concentrations (Table1).

Figure 1: Effect of different concentrations of the microalgae extracts against A. brassicicola

after in vitro treatments.

Table 1: Effect of different concentrations of the microalgae extracts (diameter of the inhibition

zone) against A. brassicicola.

Concentrations (mg/ml)

Inhibition zone in diameter (cm)

A. platensis

C. vulgaris

C. pyrenoidosa

10

2.2±1.21b*

1.1±1.10a*

1.6±0.93ab*

20

2.7±1.03bc

1.8±0.82ab

2.1±0.58abc

30

3.6±0.71c

2.6±0.63b

2.9±0.77b

40

4.0±0.50cd

3.1±0.56bc

3.4±0.41bc

50

4.9±0.36d

3.9±0.49c

4.2±0.28c

Control

0.8±1.60a

*The concentration results are averaged on five replicates. Values given separately for in vitro assays within

each column followed by different letters are significantly different at p<0.05.

Taking into account in vivo assays (seed,

foliar, and seed + foliar treatments), the

microalgal suspensions were generally found

to have considerable antifungal activity at

increasing concentrations against A.

brassicicola compared with control treatments.

For both cabbage and mustard, the seed + foliar

treatment of Arthrospira platensis, Chlorella

pyrenoidosa, and Chlorella vulgaris suspensions

at a concentration of 15 g/l was found to have

a strong antifungal activity with an inhibition

rate above 89% (Table 2, 3 and 4). In particular,

the seed + foliar treatment of a mixture of the

microalgal suspension (A. platensis + C. vulgaris

+ C. pyrenoidosa) at a concentration of 15 g/l

exhibited the highest antifungal activity,

ER Yeşim, 2023

31

suppressing growth of the pathogen with an

inhibition rate above 98%, while foliar

treatment of C. vulgaris at a concentration of 3

g/l was determined to have the lowest antifungal

activity with an inhibition rate under 40.4% in

cabbage and mustard plants (Table 3 and 5).

Table 2: Effect of different concentrations of A. platensis on Alternaria black leaf spot disease caused

by Alternaria brassicicola in cabbage and mustard seedlings.

Treatment

Concentrations

(g/l)

Cabbage Seedlings

Mustard Seedlings

Disease severity

(%)

Inhibition rate

(%)

Disease severity

(%)

Inhibition rate

(%)

Foliar treatment

3

47.4±2.31cd*

50.8

53.2±1.99bc*

46.4

6

42.6±1.81c-f

55.8

48.2±2.05b-e

51.4

9

29.6±0.71d

69.2

46.8±1.52c

52.8

12

24.8±1.11d-f

74.2

43.7±1.03c-f

55.9

15

22.5±0.63d-g

76.6

41.8±1.44c-h

57.9

Seed treatment

3

27.9±1.53de

71.0

38.0±0.70d

61.7

6

24.2±0.66d-f

74.8

34.6±0.53de

65.1

9

22.4±1.92d-g

76.7

23.0±0.82d-g

76.8

12

19.9±0.80d-g

79.3

20.4±1.67d-h

79.4

15

17.7±1.34e

81.6

18.6±0.49e

81.2

Seed + foliar treatment

3

26.0±2.51de

73.0

20.1±0.81d-h

79.7

6

23.9±2.33d-f

75.2

17.6±0.59ef

82.2

9

19.6±0.92d-g

79.6

15.6±0.94e-g

84.2

12

16.0±1.20ef

83.4

9.3±0.31f

90.6

15

9.3±0.45e-g

90.3

7.2±0.23fg

92.7

Control

-

96.4±3.22a

-

99.3±3.90a

-

*The concentration results are averaged on five replicates. Values given separately for in vivo assays within each

column followed by different letters are significantly different at p<0.05.

Table 3: Effect of different concentrations of C. vulgaris on Alternaria black leaf spot disease caused

by Alternaria brassicicola in cabbage and mustard seedlings.

Treatment

Concentrations

(g/l)

Cabbage Seedlings

Mustard Seedlings

Disease severity

(%)

Inhibition rate

(%)

Disease severity

(%)

Inhibition rate

(%)

Foliar treatment

3

58.1±2.98b*

39.7

59.2±3.12b*

40.3

6

53.5±2.01b-d

44.5

57.2±2.35b

42.3

9

50.7±1.61b-e

47.4

53.3±2.78bc

46.3

12

47.4±1.05cd

50.8

51.9±1.98b-d

47.7

15

42.7±0.82c-f

55.7

45.9±1.22cd

53.7

Seed treatment

3

47.8±1.25cd

50.4

52.1±2.05b-d

47.5

6

43.4±0.97c-f

54.9

46.1±1.62c

53.5

9

41.0±2.25c-g

57.4

44.2±1.20c-e

55.4

12

29.0±0.51d

69.9

42.5±0.81c-g

57.2

15

27.2±0.64de

71.7

29.6±0.76d-f

70.1

Seed + foliar treatment

3

24.2±1.72d-f

74.8

26.2±1.04d-f

73.6

6

21.3±0.91d-g

77.9

23.6±1.57d-g

76.2

9

18.8±0.44e

80.4

20.0±0.85d-h

79.8

12

10.1±0.68e-g

89.5

16.3±0.99e-g

83.5

15

8.2±0.38e-g

91.4

9.3±0.24f

90.6

Control

-

96.4±3.22a

-

99.3±3.90a

-

*The concentration results are averaged on five replicates. Values given separately for in vivo assays within each

column followed by different letters are significantly different at p<0.05.

ER Yeşim, 2023

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Table 4: Effect of different concentrations of C. pyrenoidosa on Alternaria black leaf spot disease

caused by Alternaria brassicicola in cabbage and mustard seedlings.

Treatment

Concentrations

(g/l)

Cabbage Seedlings

Mustard Seedlings

Disease severity

(%)

Inhibition rate

(%)

Disease severity

(%)

Inhibition rate

(%)

Foliar treatment

3

56.0±2.25bc*

41.9

45.8±3.01cd*

53.8

6

53.2±3.01b-d

44.8

40.5±2.56c-h

59.2

9

48.2±2.19c

50.0

29.8±0.74d-f

69.9

12

45.8±1.34c-e

52.4

26.8±1.80d-f

73.0

15

42.7±1.77c-f

55.7

24.1±0.45d-g

75.7

Seed treatment

3

43.4±1.26c-f

54.9

30.0±2.17d-f

69.7

6

40.6±0.94c-g

57.8

27.2±2.02d-f

72.6

9

28.4±0.72d

70.5

24.4±0.85d-g

75.4

12

26.1±0.55de

72.9

21.8±1.43d-h

78.0

15

24.6±1.10d-f

74.4

19.5±0.24d-h

80.3

Seed + foliar treatment

3

23.2±0.97d-f

75.9

28.0±1.03d-f

71.8

6

19.9±0.65d-g

79.3

24.3±0.93d-g

75.5

9

16.4±0.99ef

82.9

20.0±0.51d-h

79.8

12

9.4±0.26e-g

90.2

17.2±1.19ef

82.6

15

7.7±0.18e-g

92.0

10.0±0.73f

89.9

Control

-

96.4±3.22a

-

99.3±3.90a

-

*The concentration results are averaged on five replicates. Values given separately for in vivo assays within each

column followed by different letters are significantly different at p<0.05.

Table 5: Effect of different concentrations of Arthrospira platensis + Chlorella vulgaris+ Chlorella

pyrenoidosa on Alternaria black leaf spot disease caused by Alternaria brassicicola in cabbage and

mustard seedlings.

Treatment

Concentrations

(g/l)

Cabbage Seedlings

Mustard Seedlings

Disease severity

(%)

Inhibition rate

(%)

Disease severity

(%)

Inhibition rate

(%)

Foliar treatment

3

29.6±1.69d*

69.2

30.0±2.28d-f*

69.7

6

26.9±1.26de

72.0

28.8±1.02d-f

70.9

9

24.4±0.97d-f

74.6

26.4±1.21d-f

73.4

12

22.6±0.38d-g

76.5

23.1±0.77d-g

76.7

15

19.6±0.24d-g

79.6

26.6±0.94d-f

73.2

Seed treatment

3

23.9±0.70d-f

75.2

20.2±0.43d-h

79.6

6

20.8±1.88d-g

78.4

23.9±0.52d-g

75.9

9

18.2±0.84e

81.1

19.3±1.05d-h

80.5

12

10.1±1.06e-g

89.5

16.0±0.90e-g

83.8

15

8.1±0.31e-g

91.5

8.5±0.63fg

91.4

Seed + foliar treatment

3

8.2±0.42e-g

91.4

9.1±0.35f

90.8

6

6.6±0.79f

93.1

7.9±0.44fg

92.0

9

4.5±0.56fg

95.3

5.6±0.21g

94.3

12

1.7±0.11g

98.2

1.9±0.10h

98.0

15

1.3±0.19g

98.6

1.4±0.17h

98.5

Control

-

96.4±3.22a

-

99.3±3.90a

-

*The concentration results are averaged on five replicates. Values given separately for in vivo assays within each

column followed by different letters are significantly different at p<0.05.

4. Discussion

Although the microalgae such as Arthrospira

spp. and Chlorella spp. are important providers

of a wide array of various bioactive

compounds, they have received little attention

as potential antifungal agents against plant

diseases. When taking into account microalgae

treatments considerably reduced disease

severity of A. brassicicola at elevated

concentrations, the findings were in agreement

with data obtained by a previous study, which

indicated that blue-green algal commercial

compounds had the potential for suppression

of soil-borne fungi (Fusarium solani, F.

oxysporum, Rhizoctonia solani, Alternaria

ER Yeşim, 2023

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solani, Sclerotium rolfsii, Sclerotinia

sclerotiorum, and S. minor) and expanded the

antagonistic ability of fungal, bacterial, and

yeast bio-agents with increasing

concentrations (Abdel-Kader and El-Mougy,

2013). Moreover, various species of Chlorella

were reported to demonstrate a high antifungal

activity against Aspergillus niger, Alternaria

alternata, and Penicillium expansum.

Particularly, C. vulgaris showed a strong

antifungal activity against A. alternata and P.

expansum with a decrease in mycelial growth

rate at increasing concentrations (Vehapi et al.,

2020). In another study, a pre-treatment with

Chlorella fusca suspension reduced

anthracnose disease severity caused by

Colletotrichum orbiculare and it was supposed

that it could induce systemic acquired

resistance (SAR) by activating defense

responses of host cells in cucumber plants

(Kim et al., 2018). Lee et al. (2016) revealed

that the conidia of C. orbiculare were banded

by C. fusca cells, suppressing appressorium

formation on cucumber plants. In addition to

that, the disease severity of gray mold disease

caused by Botrytis squamosa was reduced in

Chinese chives by more than 24.2% with a

treatment of C. fusca. Hence, it was suggested

that Chlorella species might take a significant

role in reducing disease severity of A.

brassicicola by inhibiting appressorium

formation or activating induced resistance

mechanism as an elicitor on cabbage and

mustard plants. Nevertheless, little information

is available in literature about antifungal

activity of Spirulina (Arthrospira) platensis

against phytopathogenic fungi. In the present

study, the results regarding to the antifungal

activity of Arthrospira platensis are consistent

with previous reports, informing that it

suppressed mycelium growth or spore

production of Cercospora beticola, Fusarium

oxysporum, Fusarium roseum, Botrytis cinerea,

Aspergillus niger, A. flavus, Alternaria dauci, A.

alternata, and Penicillium expansum at

increasing concentrations (Al-ghanayem, 2017;

Cosoveanu et al., 2010; Hussien et al., 2009).

It was considered that Arthrospira platensis

might have an antifungal effect to disrupt the

living structures of A. brassicicola or have an

elicitor acvitiy to trigger plant defense

responses, due to the presence of some

bioactive compounds in its composition.

Furthermore, the present study is the first

report, remarking on that the seed+foliar

treatment of a mixture of the microalgal

suspension (A. platensis + C. vulgaris + C.

pyrenoidosa) has maximum antifungal activity

at a concentration of 15 g/l against A.

brassicicola. In this regard, synergistic effect

of the mixture suspension could lead to

degrade the fungal cell wall and penetrate into

the pathogen cell. Hence, it might cause the

metabolic breakdown by preventing the

synthesis of glucan, ergosterol, chitin,

glucosamine, and proteins in pathogenic

organism (Marino et al., 2001). Besides, the

mixture suspension could act as a plant growth

stimulator by producing phytohormones like

gibberellin, jasmonic acid, ethylene, auxin,

cytokinin, and abscisic acid to promote plant

defense, in addition to activating induced

resistance mechanism as an elicitor. As a result

of this study, it was concluded that the

inhibitory activity of A. platensis and

Chlorella spp. could be related to the amount

and presence of bioactive compounds (e.g.,

phenolic compounds, phytohormones, fatty

acids, terpenoids, saponins, alkoloids, sterols,

sulfur-containing heterocyclic compounds,

and carbohydrates etc.) in their chemical

composition. We hope that microalgae-

derived preparations will be applicable and

environmentally friendly means that can be

used instead of synthetic chemicals to control

the black leaf spot caused by A. brassicicola.

ER Yeşim, 2023

34

5. Conclusion

Microalgal suspensions were found to be

effective and applicable at high concentrations

against A. brassicicola for in vitro and in vivo

assays. It was considered that the microalgal

suspensions suppressed the pathogen growth

due to bioactive compounds in their

composition. In spite of the fact that the

obtained results are sufficient and promising,

algal compounds having antifungal properties

should be investigated to expand antifungal

spectrum and optimize antifungal activity for

efficient and satisfactory formulations. In this

respect, the present study will encourage the

use of algal preparations compared to other

low-efficiency, toxic or destructive methods

for the control of black leaf spot disease caused

by Alternaria brassicicola.

Acknowledgments

The author is grateful to Julia SAHRAN and

Burcu AKAL for giving language support and

useful comments.

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