Pre- and postharvest treatment with alternatives to synthetic fungicides to control postharvest decay of sweet cherry

7/29/2019 Pre- and postharvest treatment with alternatives to synthetic fungicides to control postharvest decay of sweet ch

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Postharvest Biology and Technology 78 (2013) 133138

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Postharvest Biology and Technologyjournal homepage: www.elsevier .com/ locate /postharvbio

Pre- and postharvest treatment with alternatives to synthetic fungicides to

control postharvest decay ofsweet cherry

Erica Feliziani, Marilla Santini, Lucia Landi, Gianfranco Romanazzi

Department of Agricultural, Foodand Environmental Sciences,Marche Polytechnic University, Via Brecce Bianche, 60131Ancona, Italy

a r t i c l e i n f o

Article history:

Received 22 September 2012

Accepted 16 December 2012

Keywords:

Botrytis cinerea

Chitosan

Monilinia spp.

Prunus avium

Resistance inducers

a b s t r a c t

The effectiveness ofalternatives to synthetic fungicides for the control ofpathogens causing postharvest

diseases ofsweet cherry was tested in vitro and invivo. When amended to potato dextrose-agar, oligosac-

charides, benzothiadiazole,chitosan, calcium plus organic acids, and nettle macerate reduced the growth

ofMonilinia laxa, Botrytis cinerea and Rhizopus stolonifer. Treatment ofsweet cherries three days before

harvest or soon after harvest with oligosaccharides, benzothiadiazole, chitosan, calcium plus organic

acids, nettle extract, fir extract, laminarin, or potassium bicarbonate reduced brown rot, gray mold, Rhi-

zopus rot, Alternaria rot, blue mold and green rot ofcherries kept 10 d at 201 C, or 14 d at 0.51 C

and then exposed to 7 d ofshelf-life at 201 C. Among these resistance inducers, when applied either

preharvest or postharvest, chitosan was one of the most effective in reducing storage decay of sweet

cherry, and its antimicrobial activity in vitro and in field trials was comparable to that of the fungicide

fenhexamid. Benzothiadiazolewas more effective when applied postharvest than with preharvest spray-

ing. These resistance inducers could represent good options for organic growers and food companies, or

they can complement the use ofsynthetic fungicides in an integrated disease management strategy. 2012 Elsevier B.V. All rights reserved.

1. Introduction

Sweet cherry (Prunus avium) is a perishable fruit, and during

storage it can undergo postharvest decay. This is mainly caused

by Monilinia spp. and Botrytis cinerea, and occasionally by Rhi-

zopus stolonifer, Alternaria alternata, Penicillium expansum, and

Cladosporium spp. (Romanazzi et al., 2001). At present, prehar-

vest treatments with synthetic fungicides are the main means

for postharvest disease control in stone fruit in general. How-

ever, alternatives to the use of synthetic fungicides are needed forthe sweet cherry market, where no fungicides are registered for

postharvest applications and none are allowed in organic agricul-

ture. Compared to synthetic fungicides, alternative methods might

also have the benefits of lower risk of the development of fungal

resistance, lower cost, and application close to the harvest. More-

over, they have the potential to reduce the impact of agriculture on

the environment and on human health (Elmer and Reglinski, 2006;

Mari et al., 2010).

Natural compounds with antimicrobial activity and eliciting

properties might represent alternatives to synthetic fungicides in

the control of postharvest disease of fruit (Bautista-Banos et al.,

2006). Resistance inducers arecompounds that have a composition

Corresponding author. Fax: +39 071 2204336.

E-mail addresses: [email protected] , [email protected] (G. Romanazzi).

based on pathogen or plant constituents, or their analogs, such that

they can react with plant receptorsand canactivateplantdefenses;

this can then prevent pathogen infection (Terry and Joyce, 2004;

Elmer and Reglinski, 2006). Benzothiadiazole is a synthetic ana-

log of salicylic acid, and it has been reported to induce systemic

acquired resistance in plants. Furthermore, it has been shown to be

effectivein thecontrol of gray mold on strawberry (Terryand Joyce,

2000; Romanazzi et al., 2013). In the same way, some oligosaccha-

rides that are derived from the degradation of fungal and plant cell

wall polysaccharides represent a class of well-characterized elici-tors that in some cases can induce plant defense responses at very

low concentrations (Shibuya and Minami, 2001). Also, the natural

polysaccharide chitosan has been reported to have antimicrobial

activity against a long list of postharvest fungi and to be effective

in inducing an array of responses in plant tissue (Bautista-Banos

et al., 2006; Romanazzi et al., 2009; Reglinski et al., 2010; Feliziani

et al., in press). Chitosan treatmentcan elicitplant defenses through

the stimulation of enzymes related to pathogenesis and prolonged

fruit and vegetable storage (Li and Yu, 2000; Meng et al., 2010;

Romanazzi et al., 2012; Wang and Gao, in press). Additionally, chi-

tosan treatment can form a coating on the surface of the fruit that

slows down the respiration and ripening processes (Romanazzi

et al., 2009; Dang et al., 2010).

Recently, interest in the use of plant extracts and essential oilsfor theirantimicrobial activity has increased,becausethese are con-

sidered to be safe for both the environment and human health.

0925-5214/$ seefrontmatter 2012 Elsevier B.V. All rightsreserved.

http://dx.doi.org/10.1016/j.postharvbio.2012.12.004


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134 E. Felizianiet al./ Postharvest Biology and Technology 78 (2013) 133138

Indeed, some such preparations have shown a broad spectrum of

activity against plant pathogens, and particularly those responsi-

ble for postharvest diseases of fruit and vegetables (Tripathi and

Dubey, 2004; Gatto et al., 2011). Furthermore, inhibitory effects

of inorganic salts against postharvest diseases have been reportedon different commodities (Sanzani et al., 2009; Mari et al., 2010);

among these, thecontrolof postharvest rots on thesweetcherryby

sodium bicarbonate andpotassiumsorbatehasbeendemonstrated

(Ippolito et al., 2005; Karabulut et al., 2001, 2005).

The aims of the present study were to: (i) evaluate the in vitro

abilityofoligosaccharides, benzothiadiazole,chitosan,calciumplus

organic acids,nettleextract, as alternatives to fungicides, to inhibit

thegrowthofMonilinia laxa, B. cinerea, R. stoloniferandA. alternata,

and (ii) evaluate the effectiveness of preharvest and postharvest

applications of these and other resistance inducers, such as lami-

narin, potassium bicarbonate, fir extract for the control of brown

rot, gray mold, Rhizopus rot, Alternaria rot, blue mold and green

rot during the storage of sweet cherries at room temperature

(201

C) and at cold temperature (0.51

C).

2. Materials andmethods

2.1. Antimicrobial activities of the resistance inducers in vitro

The antimicrobial activities of a range of resistance inducers

were tested for their ability to reduce mycelial growth of fun-

gal colonies. Agar plugs, with a diameter of 6mm, from M. laxa,

B. cinerea, A. alternata or R. stolonifer colonies in active growth

were placed in the centers of Petri dishes containing 10mLpotato

dextroseagar in water without (control) or with additions, after

autoclaving, of oligosaccharides (10g/L, Algition, Socoa Trading,

Bologna, Italy), benzothiadiazole (2g/L, Bion, Syngenta, Basilea,

Switzerland), chitosan (10g/L, Chito Plant, ChiPro GmbH, Bremen,Germany), calcium plus organic acids (COA) (10 g/L, Fitocalcio,

Agrisystem Srl, Lamezia Terme, Italy), extract from Urtica dioica

(10g/L), or fenhexamid (0.5g/L, Teldor, Bayer CropScience, Mon-

heim am Rhein, Germany). The U. dioica extract was prepared by

macerating 10kg of green leaves and stems of the nettle in 100L

water and leaving this for 1 month. The suspension thus obtained

was filtered through a double layer of cheesecloth, anddiluted 10-

fold. To determine the antimicrobial activities of the formulations

used, the radial growth of the fungal colonies was measured daily,

until one of the treatments reached the edge of the Petri dish.

Seven replicates were used for each fungus and each treatment.

Thisperiodcorrespondedapproximatelyto 34days forR. stolonifer

colonies and to 1 week for B. cinerea, M. laxa andA. alternata.

2.2. Postharvest treatments

Commercial sweet cherry Sweet Heart and Burlat were har-

vestedfromanorganicorchard inAncona, central-easternItaly.The

fruit were selected for uniformity in size and color, and absence of

deformity or disease. The Sweet Heart cherries were treated with

nettle extract (10 g/L), benzothiadiazole (2g/L), chitosan (10 g/L),

oligosaccharides (10 g/L), or COA (10g/L). The Burlat cherries

were treated with benzothiadiazole (2g/L), chitosan (10g/L), fir

extract from Abies sibirica (10 g/L, Abies, Agritalia, Villa Saviola di

Motteggiana, Italy), laminarin (10g/L, K&A Frontiere, BioAtlantis,

Tralee, Ireland) or potassium bicarbonate at different concentra-

tions (4, 9, 17, 26, 34 or 43g/L) (Karma, Certis Europe, Saronno,

Italy). Distilled water was used as the control. The cherries were

randomized and immersed for 1min in the tested solutions. Three

replicates of thirty cherries per treatment were placed into small

plastic boxes that were then placed into large boxes. To create

humid condition of storage, a layer of wet paper was placed in the

bottomof thelargeboxes. TheSweet Heartcherrieswerekept 10d

at 201 C, 95% to 98% relative humidity (RH), while the Burlat

cherries were stored for 14 d at 0.51 C, and then exposed to 7d

of shelf-life at 201 C,95% to 98% RH.

2.3. Preharvest treatments

The trials were carried out in an experimental orchard located

in a hilly area of the Ancona Province (433160N, 132260E;

203m a.s.l.) in central-eastern Italy in 2009 and 2011. The trees

were selected for uniformity of production and ripening. In 2009,

the canopy of Sweet Heart trees was sprayed with a solution of

chitosan (10g/L), nettle extract (10g/L), or fenhexamid (0.5g/L), 3

days before the harvest. In 2011, Blaze Star trees were sprayed

with a solution of chitosan (10g/L), fir extract (10 g/L), benzothia-

diazole (2g/L), or fenhexamid (0.5g/L), 3 days before the harvest.

The spraying used a back pump (model WJR2525, Honda, Tokyo,

Japan) to deliver the equivalent volume of 1000L/ha. Untreated

trees were used as controls for both years. On the day of the har-

vest, the cherries were selected for uniformity in size and color,

andabsenceofdeformityor disease. Tenreplicatesof750g cherries

pertreatment were collectedin plastic boxes that were then placed

into largeboxes.To createhumidconditionof storage,a layerofwet

paperwas placedin thebottomof thelargeboxes.The SweetHeart

and Blaze Star cherries were stored for 14d at 0.51 C, and then

exposed to7 d ofshelf-lifeat 201 C,95%to 98%RH. Inthepresent

trials, we simulated real agricultural practices using preharvest

applications of a commercial chitosan formulation. Commercial

formulationsfor chitosanhave theadvantage ofmore practicaluse,

as viscosity is lower than that of the biopolymer dissolved in acid

solution, and it has the same effectiveness as chitosan dissolved in

acetic acid (Romanazzi et al., 2009, 2013).

2.4. Data recording for the in vivo trials

In the in vivo trials, at the end of the storage, the levels of decay

due to each of the pathogens were assessed separately accord-

ing to the symptoms. In any cases of doubt, isolations from rotted

tissues were carried out on potato dextrose-agar, and the causal

agent was identified according to the morphological properties.

Thediseases incidencewasexpressedas thepercentageof infected

fruit. The severity was assigned to five classes according to the

percentage of cherry surface covered by fungal mycelia: 0, unin-

fected cherry; 1, surface mycelia just visible to 25% of the cherry

surface; 2, 26% to 50% of the cherry surface covered with mycelia;

3, 51% to 75% of the cherry surface covered with mycelia; and 4,>75% of the cherry surface covered with mycelia (Romanazzi et al.,

2001). The infection index (or McKinney index), which incorpo-

rates both the incidenceandseverity of thedisease, wasexpressed

as the weighted means of the disease as a percentage of the maxi-

mumpossiblelevel(McKinney,1923).Specifically, itwascalculated

by the formula: I= [(df)/(ND)]100, where d is the category

of rot intensity scored on the sweet cherry and f its frequency; N

the total number of sweet cherries examined (healthy and rotted)

and D is the highest category of disease intensity occurring on the

empirical scale (Romanazzi et al., 2001).

2.5. Statistical analysis

The data were analyzed statistically by one-way ANOVA, fol-lowed by Tukeys HSD test, at P= 0.05 (Statsoft, USA). Percentage

data were arcsine transformed before analysis to improve homo-

geneity ofvariancewhenthe rangeofpercentages wasgreater than

40. Actual values are shown.


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E. Felizianiet al./ Postharvest Biology and Technology 78 (2013) 133138 135

Table 1

Radialmycelial growth(mm) offungalcolonies(Monilinialaxa ,Botrytiscinerea ,Alternariaalternata,Rhizopusstolonifer) onPDA amended withwater(control),oligosaccharides,

benzothiadiazole, chitosan, calcium plus organic acids, nettle extract, and fenhexamid.

Treatment (g/L) Radial growth (mm)

Monilinia laxa Botrytis cinerea Alternaria alternata Rhizopus stolonifer

Control 29 aa 70 a 80 a 25 a

Oligosaccharides (10) 23 b 55 b 70 b 21 ab

Benzothiadiazole (2) 10 d 32 d 37 d 12 c

Chitosan (10) 0 e 9 e 31 e 0 d

Calcium plus organic acids (10) 11 d 49 c 71 b 22 ab

Nettle extract (10) 18 c 32 d 57 c 18 b

Fenhexamid (0.5) 0 e 0 f 18 f 0 d

a Valuesfollowedby differentletters aresignificantly differentwithin columns, according to Tukeys HSD(P= 0.05).

Table 2

Effects of postharvest treatment with water (control), oligosaccharides, benzothiadiazole, chitosan, calcium plus organic acids, and nettle extract on McKinney infection

index of postharvest diseases (brown rot, gray mold, Rhizopus rot, Alternaria rot, andtotal rot) of sweet cherries cv. Sweet Heart kept 10d at 201 C,95%to 98% RH.

Treatment (g/L) McKinney infection index (%)

Brown rot Gray mold Rhizopus rot Alternaria rot Total rota

Control 24.6 ab 21.3 a 32.8 a 49.2 a 67.2 a

Oligosaccharides (10) 11.5 b 12.2 b 6.6 b 26.2 b 36.1 b

Benzothiadiazole (2) 9.8 b 13.9 b 12.3 b 24.6 b 44.2 b

Chitosan (10) 6.6 b 11.5 b 7.4 b 22.9 b 29.5 b

Calcium plus organic acids (10) 9.8 b 16.4 b 20.5 b 27.7 b 49.3 b

Nettle extract (10) 4.9 b 6.5 b 4.9 b 16.4 b 23.0 b

a Total rotincludes brown rot, gray mold, Rhizopus rot, Alternaria rot, blue mold and green rot.b Valuesfollowedby differentletters aresignificantly differentwithin columns, according to Tukeys HSD(P= 0.05).

3. Results

3.1. Antimicrobial activities of resistance inducers in vitro

When added to potatodextroseagar, allof thetested resistance

inducers reduced the radial growth ofM. laxa, B. cinerea and R.

stolonifer, as compared to the controls.A. alternata growth was also

inhibited exceptfor the oligosaccharidesand COA. Fenhexamidand

chitosan had the highest ability of reducing the mycelial growth of

all of the tested fungi. In particular, growth ofM. laxa and A. alter-

nata was completely inhibited with fenhexamid and chitosan, and

B. cinerea did not grow with fenhexamid. R. stolonifergrowth was

inhibited by all of the resistance inducers, although none of them

completely stopped its growth (Table 1).

3.2. Postharvest treatments

The postharvest treatmentswith oligosaccharides, benzothiadi-

azole, chitosan, COA, and nettle extract all reduced the postharvest

decay of the Sweet Heart cherries kept 10 d at 201 C, 95%

to 98% RH (Table 2). There were no statistical differences among

these treatments. Compared to the control, the application of net-

tle extract, chitosan, oligosaccharides, benzothiadiazole, and COA

reduced the sweet cherry total rots of 66%, 56%, 46%, 34% and 27%,

respectively. The infection index of the total rot, that included gray

mold, brown rot, Rhizopus rot, Alternaria rot, blue mold and green

rot, was lower than the sum of the single infection indices as mul-

tiple infections can occur on the same cherry.

The postharvest treatment with benzothiadiazole, chitosan, fir

extract, the algal oligosaccharide laminarin, and potassium bicar-

bonate at different concentrations decreased the total rot of the

Burlat cherries cold-stored for 14d (0.51 C) and then exposed

to 7d of shelf-life (201 C, 9598% RH; Table 3). The most effec-

tive treatments in controlling postharvest total rots of sweet cherry

were chitosan and potassium bicarbonate at concentrations ran-

ging from 4 to 26 g /L. For brown rot, gray mold and total rot,

chitosan reduced theinfectionindices by 67%, 88%and 75%, respec-

tively, and 26g/L potassium bicarbonate by 75%, 92% and 76%,

respectively. Gray mold infections were reduced by all the tested

resistance inducers. While infection indices for brown rot were not

decreased by potassium bicarbonate at 34g/L and 43g/L, but when

it was used at lower concentrations. The treatment with potas-

sium bicarbonate induced phytotoxic effects that were visible from

concentrations >9g/L, and that increased further with concentra-

tion (data not shown). These phytotoxic symptoms consisted of

pedicel browning and the formation of dark spots on the cherry

surface. Moreover, the pedicels of the sweet cherries treated with

potassium bicarbonate dried earlier.

3.3. Preharvest treatments

Preharvest treatments with chitosan, nettle macerate, and fen-

hexamid significantly reduced brown rot, gray mold, and Rhizopus

rot of the Sweet Heart cold-stored for 14d (0.51 C) and then

Table 3

Effectsof postharvest treatmentwith water (control), benzothiadiazole, chitosan,fir

extract,laminarin, andpotassiumbicarbonateat differentconcentrations onMcKin-ney infection index of postharvest diseases (brown rot, gray mold, and total rots)

of sweet cherries cv. Burlat stored 14d at 0.51 C and then exposed to 7 d of

shelf-life at 201 C,95%to 98% RH.

Treatment ( g/L) McKinney i nfection i ndex (%)

Brown rot Gray mold Total rota

Control 44.9 ab 61.3 a 70.4 a

Benzothiadiazole (2) 8.7 b 33.8 b 37.6 bc

Chitosan (10) 14.9 b 7.6 c 17.3 de

Fir extract (10) 14.4 b 30.7 b 35.6 bc

Laminarin (10) 13.1 b 25.6 bc 34.2 bcd

Potassium bicarbonate (4) 12.7 b 18.9 bc 27.8 bcde

Potassium bicarbonate (9) 15.8 b 14.4 bc 25.1 cde

Potassium bicarbonate (17) 12.4 b 13.6 bc 22.7 cde

Potassium bicarbonate (26) 11.1 b 5.1 c 16.7 e

Potassium bicarbonate (34) 23.6 ab 14.9 bc 36.9 bcPotassium bicarbonate (43) 28.4 ab 18.0 bc 44.2 b

a Total rot includes brown rot, gray mold, Rhizopus rot, Alternaria rot, blue mold

and green rot.b Values followed by different letters are significantly different within columns,

according to Tukeys HSD(P=0.05).


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Table 4

Effect of treatments applied 3 days before the harvest with water (control), chitosan, nettle extract, and fenhexamid on McKinney infection index of postharvest diseases

(brownrot, gray mold, Rhizopus rot, Alternaria rot, andtotalrots)of sweet cherries cv.Sweet Heart stored14 d at 0.51 C and thenexposedto 7d ofshelf-life at201 C,

95% to98% RH.


Brown rot Gray mold Rhizopus rot Alternaria rot Total rota

Control 13.6 ab 19.3 a 18.6 a 33.6 a 74.3 a

Chitosan (10) 5.0 b 13.9 b 12.9 b 17.9 b 42.9 b

Nettle extract (10) 5.0 b 13.4 b 13.6 b 28.6 ab 48.6 b

Fenhexamid (0.5) 2.9 b 7.9 b 10.7 b 14.3 b 31.4 c

a Total rotincludes brown rot, gray mold, Rhizopus rot, Alternaria rot, blue mold and green rot.b Valuesfollowed by differentletters are significantly differentwithincolumns,according to Tukeys HSD(P= 0.05).

exposed to 7d of shelf-life (201 C, 9598% RH, Table 4), and

among these treatments, there wereno statistical differences. Com-

pared to the control, for brown rot, gray mold, Rhizopus rot and

Alternaria rot,chitosantreatment reduced infectionindices by 63%,

28%,31% and 47%,respectively, while fenhexamid reduced themby

79%, 59%, 42%and 57%, respectively. Alternaria rotwas not affectedby the nettle extract, however it reduced the infection indices for

brownrot,gray mold andRhizopus rotby 63%, 31%and27%,respec-

tively. Fenhexamid provided the greatest reduction of the total rot,

at 58%, a level significantly greater than all of the other treatments.

The preharvest treatments with chitosan, fir extract, and fen-

hexamid reduced brown rot on theBlaze Star cherries cold-stored

for 14 d (0.51 C) and then exposed to 7 d of shelf-life (201 C,

95% to 98% RH; Table 5). Compared to the control, the infection

indices for brown rot (themost predominant decay thatoccurred in

these trials) wasreducedby 91%, 62%and57% after treatments with

fenhexamid, chitosan and fir extract, respectively, and the effects

of these treatments were not statistically different from eachother.

4. Discussion

The in vitro ability of chitosan to reduce mycelial growth of

M. laxa, B. cinerea, R. stoloniferand A. alternata were comparable

to those obtained with the synthetic fungicide fenhexamid. These

data support previous studies that have reported that chitosan

formulations reduced germination and radial growth of a list of

decay-causing fungi, such as B. cinerea (El Ghaouth et al., 1992;

Badawy and Rabea, 2009), A. alternata (Snchez-Domnguez et al.,

2011), Rhizopus spp. (El Ghaouth et al., 1992; Garca-Rincn et al.,

2010), and M.fructicola (Casals et al., 2012; Yang et al., 2012). Simi-

larly, in the present study, benzothiadiazole and nettle extract had

in vitroability of reducing themycelial growth of thetested fungi.A

concentration of 2 g/L benzothiadiazole was sufficient to inhibit B.

cinerea radial growth on potato dextroseagar media, and the fun-gus was progressively inhibited with increasing benzothiadiazole

Table 5

Effect of treatments applied 3 days before the harvest with water (control), chi-

tosan, fir extract, benzothiadiazole, and fenhexamidon McKinney infectionindex of

postharvest diseases (brown rot, Alternaria rot, and total rots) of sweet cherries cv.

BlazeStar stored14 d at0.51 C and thenexposed to7 d ofshelf-life at201 C,

95% to98%RH.


Brown rot Total rota

Control 25.0 ab 25.2 a

Chitosan (10) 9.4 bc 9.5 bc

Fir extract (10) 10.8 bc 11.0 bc

Benzothiadiazole (2) 17.0 ab 17.3 abFenhexamid (0.5) 2.2 c 2.2 c

a Total rotincludes brown rot, gray mold, Rhizopus rot, Alternaria rot, blue mold

and green rot.b Values followed by different letters are significantly different within columns,

according to Tukeys HSD(P= 0.05).

doses (Terry and Joyce,2000; Munozand Moret,2010).For the net-

tle extracts, there are no data in the literature on its effectiveness

in the control of postharvest pathogens, although phenolic com-

pounds derived fromherb extractsare known to be effectiveagainst

decay causing fungi of fruit and vegetables, such as B. cinerea, M.

laxa, Penicillium spp. andAspergillus spp. (Gatto et al., 2011).In the in vivo trials, the present study showed that preharvest

and postharvest treatments with some of these tested resistance

inducerscan reduce the development of postharvest decay of sweet

cherries. As previously reported, on sweet cherry, postharvest

application of chitosan delayed their loss of water, maintained the

quality attributes during storage, and induced peroxidase and cata-

lase activityin the fruit (Dang et al., 2010). Indeed, the combination

of hypobaric treatments and the practical grade chitosan coating

applied either preharvest or postharvest had synergistic effects on

the control of postharvest decay of sweet cherries cold-stored for

14 d (01 C) and then exposed to 7d of shelf-life (Romanazzi

etal.,2003). However, little information is available on theeffects of

preharvest or postharvest applications of the commercial chitosan

formulation, which is easy for the growers to dissolve in water, onsweet cherry postharvest decay and the growth ofM. laxa, which is

one of the main cherry postharvest pathogens.

Benzothiadiazole reduced the postharvest decay of sweetcherry

when applied postharvest, although preharvest treatment with

benzothiadiazole was not sufficient to control brown rot. In pre-

vious studies, benzothiadiazole treatments induced plant defense

systems and protectedstrawberry fromgray mold(Terryand Joyce,

2000; Romanazzi et al., 2013). Benzothiadiazole mimics the effects

of salicylic acid, which is involved in plant signal transduction sys-

temsand is needed to activatethe formationof defense compounds,

such as polyphenols and pathogenesis-related proteins (Durang

and Dong, 2004). On sweet cherry, preharvest treatments with

salicylic acid significantly reduced lesion diameters caused by M.

fructicola, and induced phenylalanine ammonia-lyase, glucanase,

and peroxidase activities during early storage of the fruit (Yao

and Tian, 2005). In the present study, benzothiadiazole reduced

the disease incidence when applied postharvest, and showed in

vitro ability of reducing the mycelial growth of the tested fungi.

This suggests that beside the well-known induced resistance of

benzothiadiazole, it can also have a direct antimicrobial effect on

several postharvest pathogens. These protective effects against

plant pathogens can thus be ascribed to the combination of its

defense-inducing activity on plants and its adverse effects on the

growth and vigor of these pathogens.

Postharvest application of potassium bicarbonate was effec-

tive in reducing postharvest brown rot and gray mold of these

Burlat sweet cherries. Potassium bicarbonate has been shown to

control Geotrichum candidum and P. expansum postharvest infec-

tions on peaches, nectarines and plums (Palou et al., 2009). In thepresent study, symptoms of potassium bicarbonate phytotoxicity

wererecordedonly afterapplications at concentrations >9 g/L.Sim-

ilarly, in a prior work, slight injury was seen to the stems of sweet

cherries treated with 0.24mol/L sodium bicarbonate (Karabulut


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Pre- and postharvest treatment with alternatives to synthetic fungicides to control postharvest decay of sweet cherry