2003 seasonal evaluation of the postharvest fungicidal activity of

UNCORRECTED PROOF

Seasonal evaluation of the postharvest fungicidal activity ofpowders and extracts of huamuchil (Pithecellobium dulce):action against Botrytris cinerea, Penicillium digitatum and

Rhizopus stolonifer of strawberry fruit

S. Bautista-Banos a,c,*, E. Garcıa-Domınguez a, L.L. Barrera-Necha a,R. Reyes-Chilpa b, C.L. Wilson c

a Centro de Desarrollo de Productos Bioticos, Instituto Politecnico Nacional, Carr. Yautepec-Jojutla km. 8.5, San Isidro Yautepec,

Morelos 62731, Mexicob Instituto de Quımica, Universidad Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan 04510, Mexico

c USDA, ARS Appalachian Fruit Research Station, 45 Wiltshire Road, Kearneysville, WV 25430, USA

Received 15 April 2002; accepted 30 November 2002

/17 /Abstract

/18 /

/19 / The fungistatic or fungicidal effect of powders, and aqueous and ethanolic extracts of seeds, and monthly harvested

/20 /leaves of huamuchil (Pithecellobium dulce ) were evaluated for fungicidal activity, against Botrytis cinerea , Penicillium

/21 /digitatum , and Rhizopus stolonifer . Fungicidal activity of huamuchil powders and aqueous extracts were also evaluated

/22 /on strawberry fruit during storage. Preliminary characterization of the active compound responsible for the fungicidal

/23 /effect was carried out using thin layer chromatography and spectrophotometry. Results indicated that powders had the

/24 /best fungicidal effect, in both in vitro and in situ studies. Fungistatic or fungicidal properties were associated with the

/25 /plant organ and harvest month. A correlation between high absorbance values of extracts with the fungicidal or

/26 /fungistatic effect was not observed. The highest fungistatic or fungicidal effect for both in vitro and in situ studies was

/27 /recorded from extracts of leaves harvested in months having more stressful environmental conditions; the cold season

/28 /(October�/February) and, the dry, hot season (April and June). Attempts to characterize the active compound suggest

/29 /that kaempferol may be responsible for the fungicidal effect.

/30 /# 2003 Published by Elsevier Science B.V.

/31 /Keywords: Fragaria �/ananassa Duch.; Guaymochil; Tamarind; Kaempferol

/ 32/1. Introduction

/ 33/ Fungal diseases are one of the major limitations

/ 34/on the storage life of strawberry fruit (Fragaria �/

y:/Elsevier Science/Shannon/Postec/articles/POSTEC2022/POSTEC2022.3d[x] 3 January 2003 9:48:0

3 * Corresponding author.

4 E-mail address: [email protected] (S. Bautista-

5 Banos).

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Postharvest Biology and Technology 00 (2003) 1�/12

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1 0925-5214/02/$ - see front matter # 2003 Published by Elsevier Science B.V.

2 doi:10.1016/S0925-5214(02)00244-2

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mailto:[email protected]

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/35 /ananassa Duch.). Botrytis cinerea , Penicillium

/36 /digitatum , and Rhizopus stolonifer are the main

/37 /pathogenic fungi to decay strawberry fruit (Snow-

/38 /don, 1991; Sommer et al., 1992). Control of these

/39 /fungi is most commonly achieved by field applica-

/40 /tions of protective fungicides. However, some of

/41 /the more effective fungicides have not been

/42 /registered for use in strawberry, and others have

/43 /developed resistance problems (Paulus, 1990)./44 /Alternatives to control postharvest fungi of fruits

/45 /such as the use of plant extracts have been

/46 /explored and less infection was reported for

/47 /ciruela, mango, and papaya after dipping fruit in

/48 /plant extracts (Bautista-Banos et al., 2000a, 2002).

/49 / Huamuchil (Pithecellobium dulce (Roxb.)

/50 /Benth), native to Mexico, is an evergreen tree

/51 /about 20 m high. This species typically occurs in/52 /lowlands where it has high tolerance to heat and

/53 /salt and grows well in most soil types, character-

/54 /istics that account for wide distribution along the

/55 /coast of Mexico. Huamuchil tree bark is com-

/56 /monly used for fencing and tanning and the pods

/57 /are prepared for food, while seeds are used for

/58 /medicinal purposes (Aguilar et al., 1996). Bautista-

/59 /Banos et al. (2000b) reported that among 20 plant/60 /species tested in vitro, aqueous extract and powder

/61 /from leaves of P. dulce had significant fungistatic

/62 /activity against Alternaria sp., Fusarium oxy-

/63 /sporum , and Pestalotiopsis sp. In other studies,

/64 /postharvest rots of yellow and red mombin

/65 /(Spondias purpurea) caused by R. stolonifer was

/66 /reduced significantly by dipping fruit in P. dulce

/67 /leaf extracts (Bautista-Banos et al., 2000a). Simi-/68 /larly, field studies carried out by Montes et al.

/69 /(1990) demonstrated the fungicidal effects of

/70 /ethanolic extracts from leaves of this species

/71 /against Uromyces appendiculatus of beans. Arzuffi

/72 /et al. (1999), Llanos et al. (1993) reported toxic

/73 /effects of powders of P. dulce seeds and leaves on

/74 /larvae of fall armyworm (Spodoptera frugiperda ).

/75 / The present paper describes the in vitro fungi-/76 /cidal or fungistatic effects of powders and aqueous

/77 /and ethanolic extracts from seeds and leaves of P.

/78 /dulce harvested monthly over a period of 1 year

/79 /against three important postharvest microorgan-

/80 /isms of strawberry. In addition, we determined the

/81 /absorbance values of aqueous and ethanolic ex-

/82 /tracts of seeds and leaves and evaluated the control

/ 83/of postharvest rots of strawberry following appli-/ 84/cation of powders or aqueous extracts.

/ 85/2. Materials and methods

/ 86/2.1. Plant material

/ 87/ Leaves and seeds were harvested from trees/ 88/grown at the Biotic Products Development Center

/ 89/in Yautepec, state of Morelos, Mexico. Leaves

/ 90/were harvested monthly over 1 year (January�/

/ 91/December) while seeds were harvested in April,

/ 92/(fruit production time). Once harvested, leaves and

/ 93/seed were sorted, discarding damaged or diseased

/ 94/material. Plant material was dipped in a 1%

/ 95/sodium hypochlorite solution, rinsed with distilled/ 96/water and dried in ambient. Leaves and seeds were

/ 97/macerated with the aid of a blender and a grinder,

/ 98/respectively, and stored in amber bottles until

/ 99/further use.

/ 100/2.2. Isolation of microorganisms

/ 101/ B. cinerea , P. digitatum and R. stolonifer were

/ 102/isolated from diseased strawberries. Pure cultures/ 103/were maintained on potato dextrose agar (PDA).

/ 104/In vitro experiments were carried out using

/ 105/cultures of 14-day-old for B. cinerea , 7-day-old

/ 106/for P. digitatum , and 4-day-old for R. stolonifer .

/ 107/2.3. Preparation of powders and extracts for in

/ 108/vitro and in situ studies

/ 109/ To evaluate plant powders for in vitro studies,

/ 110/0.5 g of the macerated material was added to 25 ml

/ 111/of PDA and then autoclaved, to obtain a final

/ 112/concentration of 20 g l�1 (w/v) of plant powder in

/ 113/the growth medium (Hernandez, 1997). For in situ

/ 114/studies, powders were applied proportionally (w/

/ 115/w) to that applied for in vitro. The final powder

/ 116/concentration applied to each fruit was then 16.6 g/ 117/kg�1 per fruit. For powder applications, fruit were

/ 118/carefully rolled over the powder to ensure that the

/ 119/entire fruit was covered.

/ 120/ Aqueous extracts (2:10 w/v) were left at room

/ 121/temperature (25�/28 8C) for 24 h, vacuum filtered,

/ 122/and sterilized. For in vitro studies, extracts were


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/123 /incorporated (10:40 v/v) and mixed with PDA and/124 /then autoclaved (Ahmad and Prasad, 1995; Bau-

/125 /tista-Banos et al., 2000b). Ethanolic extracts were

/126 /prepared according to Reyes-Chilpa et al. (1998):

/127 /plant material was extracted at room temperature

/128 /with ethanol (1:5 w/v). The extracts were concen-

/129 /trated in a rotary evaporator and 80 mg of the

/130 /concentrate was added to 1 ml of ethanol. One

/131 /milliliter of this solution was poured into PDA (16/132 /ml), after autoclaving 5 ml was added to each Petri

/133 /plate (60�/15 mm) to obtain a final concentration

/134 /of 5 g l�1 of ethanolic extract in the growth

/135 /medium.

/136 / Powders and aqueous and ethanolic extracts

/137 /were tested in vitro while only aqueous extracts

/138 /and powders were assayed in situ.

/139 /2.4. Preparation of fruit

/140 / Strawberry fruit were harvested from commer-

/141 /cial orchards located in Oacalco, Morelos. Two

/142 /experiments were carried out: the first was to

/143 /evaluate aqueous extracts and the second to

/144 /evaluate powders on the incidence of postharvest

/145 /rots. For both experiments fruit were at the half/146 /colored stage (skin was 50% red colored). Fruit

/147 /were sorted discarding damaged or diseased fruit.

/148 /For the first experiment, strawberry fruit were

/149 /individually cleaned with a soft tissue. For the

/150 /second experiment, fruit were rapidly washed as

/151 /previously indicated for plant material.

/152 / For the first experiment, fruit were dipped in

/153 /aqueous extracts of leaves or seeds for 15 min and/154 /dried at ambient temperature. For powder treat-

/155 /ments, fruit skin was uniformly covered with

/156 /powder. For both experiments fruit were placed

/157 /in plastic trays, wrapped in plastic bags but not

/158 /sealed, and stored for 5 days at 4 8C and 1 day at

/159 /ambient temperature (25 8C).

/160 /2.5. Parameters evaluated for in vitro and in situ

/161 /studies

/162 / For in vitro studies sporulation was measured as

/163 /previously described (Bautista-Banos et al.,

/164 /2000b). Mycelial growth was also evaluated and

/165 /expressed as the percent of inhibition of radial

/166 /growth relative to the control. Five-mm diameter

/ 167/agar disks of each fungus were placed in the center/ 168/of Petri plates containing powders or plant ex-

/ 169/tracts. The experiment was terminated when

/ 170/mycelium of control plates reached the edges of

/ 171/the plate. Incubation times were 14 days for B.

/ 172/cinerea , at 15 8C, 7 day for P. digitatum and 4

/ 173/days for R. stolonifer both incubated at 20 8C.

/ 174/Three replicate dishes were used for each treat-

/ 175/ment./ 176/ For in situ experiments percentage infection and

/ 177/the number of decayed fruit were evaluated. To

/ 178/identify fungi, mycelia were examined once spores

/ 179/were observed, under the microscope. Portions of

/ 180/mycelia were fixed in one drop of lactophenol acid.

/ 181/Identification was according to Barnett and Hun-

/ 182/ter (1972).

/ 183/ For both experiments, each treatment was/ 184/applied to two replicates, 40 fruit each for the first

/ 185/experiment and 25 fruit each for the second

/ 186/experiment.

/ 187/2.6. Characterization of flavonols by

/ 188/spectrophotometry and thin layer chromatography

/ 189/(TLC)

/ 190/ To determine the presence of flavonols absorb-/ 191/ing at 346 nm, the ethanolic extracts of the seeds

/ 192/and the monthly harvested leaves of this plant

/ 193/species were analyzed by ultraviolet spectroscopy

/ 194/(UV) (Shimadzu UV-160) and by TLC. Ethanolic

/ 195/extract (1 g l�1) of leaves and seeds was analyzed

/ 196/by UV to determine the absorption at 346 nm.

/ 197/ To screen flavonol compounds of seeds and

/ 198/monthly harvested leaves of P. dulce , the aqueous/ 199/and ethanolic extract of seeds, the monthly har-

/ 200/vested leaves and the reference compound kaemp-

/ 201/ferol (important component of P. dulce seeds and

/ 202/leaves, maximum absorbance at 346 nm, Southon,

/ 203/1994; Merck, 1996) were analyzed by TLC over

/ 204/Silica gel 60F254 plates (Merck 0.25 mm) with the

/ 205/following elution systems: ethyl acetate:formic

/ 206/acid:glacial acetic acid:water (100:11:11:27). De-/ 207/veloped TLC plates were sprayed by 1% metha-

/ 208/nolic diphenylboric acid�/b-ethylamino ester (NP),

/ 209/followed by 5% ethanolic polyethyleneglycol 4000

/ 210/(PEG) and observed under UV-365 nm light and

/ 211/Rf values were then determined (Wagner et al.,

/ 212/1984).


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/213 /2.7. Statistical analyses

/214 / Treatments were arranged in a completely

/215 /randomized design. ANOVA, standard deviations

/216 /(S.D.) and means were calculated for mycelial

/217 /inhibition and sporulation of the three fungi.

/218 /Percentage disease was analyzed using the x2

/219 /procedure. Square root transformation was car-

/220 /ried out when data were not normally distributed.

/221 /3. Results

/222 / The effect of powders and aqueous and etha-

/223 /nolic extracts on mycelial growth and sporulation

/224 /varied according to the treatment and fungus.

/225 /Botrytis was the most affected by powders and

/226 /plant extracts./227 / Except for mycelial inhibition of R. stolonifer ,

/228 /the effect of P. dulce powders on both mycelial

/229 /growth and sporulation was significantly different

/230 /(P�/0.001) among treatments (Table 1). For B.

/231 /cinerea , the highest mycelial inhibition was ob-

/232 /tained with seed powders (78%), while sporulation

/233 /of this fungus was most affected by leaf powders

/234 /harvested in January, November and December./235 /For P. digitatum powder prepared from leaves

/236 /harvested in July had the highest fungistatic effect

/237 /(58%) compared with the control treatment where

/238 /no inhibition was observed. Similarly, no effect on

/239 /mycelial growth was observed for R. stolonifer .

/240 /The least sporulation for Rhizopus occurred with

/241 /leaf powders from April and May.

/242 / Aqueous or ethanolic extracts did not have any/243 /effect on the mycelial inhibition of R. stolonifer

/244 /while significant differences (P�/0.001) were ob-

/245 /served for B. cinerea and P. digitatum. Botrytis

/246 /grown on aqueous extracts of leaves harvested in

/247 /February and November showed the least mycelial

/248 /growth (mycelial inhibition�/60 and 57%, respec-

/249 /tively) compared with the control treatment, coin-

/250 /ciding with inhibition were aqueous extracts/251 /exhibited high values of absorbance (2.25 and

/252 /2.50 Abs). Other treatments that inhibited the

/253 /mycelial growth of this fungus more than 50%

/254 /were ethanolic extracts from seeds and leaves

/255 /harvested from October to December. There was

/256 /not a close correlation with high absorbance

/ 257/values. For P. digitatum , treatments of aqueous

/ 258/extracts of leaves also harvested in October and

/ 259/November inhibited 60% of the mycelial growth

/ 260/while treatments prepared from aqueous extracts

/ 261/of leaves harvested in March and June reduced

/ 262/growth of P. digitatum 52 and 53%, respectively.

/ 263/For all these treatments the absorbance values of

/ 264/the aqueous extracts were among the highest:

/ 265/2.23�/2.50 (Figs. 1 and 2).

/ 266/ For the three fungi, there were also significant

/ 267/differences (P�/0.001) with sporulation. Aqueous

/ 268/and ethanolic extracts prepared from leaves and

/ 269/seeds harvested in February affected sporulation

/ 270/of the three test fungi. For Botrytis , complete

/ 271/inhibition was also observed from aqueous ex-

/ 272/tracts of leaves harvested in January, November,

/ 273/and December, coinciding with the highest absor-

/ 274/bance values (2.3�/2.5 Abs). The highest absor-

/ 275/bance values of the ethanolic extract, in most cases

/ 276/do not coincide with less sporulation as it is shown

/ 277/with the low or zero sporulation recorded for the

/ 278/three fungi and the low or zero absorbance values

/ 279/from seeds (Figs. 3 and 4).

/ 280/ Results of flavonol determination by TLC of the

/ 281/aqueous and ethanolic extracts of each treatment

/ 282/showed that except for the ethanolic extracts of

/ 283/seed and leaves harvested in July, kaempferol

/ 284/was present in the remainder treatments (Table

/ 285/2). By contrast this compound was identified only

/ 286/in five of the 13 treatments for the aqueous

/ 287/extracts.

/ 288/ In this study, the main fungi isolated from both

/ 289/experiments with strawberry were B. cinerea and

/ 290/R. stolonifer . For both experiments B. cinerea was

/ 291/more frequent as shown by the high number of

/ 292/infected fruit in the first experiment and the

/ 293/absences of R. stolonifer from the second experi-

/ 294/ment (Table 3). Percentage infection was signifi-

/ 295/cantly different (P�/0.05 and 0.01) among

/ 296/treatments for fruit treated with powders and

/ 297/extracts, respectively. Of the 13 extracts tested,

/ 298/eight promoted fruit infection of fruit dipped in

/ 299/aqueous extracts. The lowest percentage infection

/ 300/was 27% in fruit dipped in aqueous extracts from

/ 301/leaves harvested in August while in fruit powdered

/ 302/the lowest percentage infection (16%) was for

/ 303/those treated with seeds and leaves from October.



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Table 1

Effect of P. dulce powders of seeds and monthly harvested leaves on B. cinerea , P. digitatum and R. stolonifer on mycelial inhibition and sporulation after an incubation

period

Plant or-

gan

B. cinerea P. digitatum R. stolonifer

Mycelial inhibition (%)

P�/0.001a

Sporulation (104) P�/

0.001a

Mycelial inhibition (%)

P�/0.001a


0.001a

Mycelial inhibition

(%)


0.001a

Seeds 78 (0.1) 1.3 (0.01) 25 (0.1) 21.9 (1.9) 0 10.4 (0.4)

Leaves

January 40 (0.1) 0 0 17.9 (2.3) 0 6.9 (0.1)

February 60 (0.8) 1.0 (0.1) 45 (0.07) 14.0 (1.0) 0 7.2 (0.1)

March 55 (0.1) 0.9 (0.07) 25 (0.04) 24.4 (1.0) 0 11.3 (0.5)

April 40 (0.8) 1.3 (0.03) 33 (0.06) 24.9 (1.9) 0 3.4 (0.07)

May 33 (0.8) 1.0 (0.01) 20 (0.03) 28.7 (3.8) 0 3.2 (0.1)

June 60 (0.1) 2.4 (0.03) 50 (0.06) 21.4 (1.8) 0 4.2 (0.4)

July 40 (0.5) 1.0 (0.01) 58 (0.05) 18.4 (0.5) 0 7.0 (0.2)

August 53 (0.2) 1.5 (0.01) 43 (0.1) 18.0 (1.0) 0 12.3 (0.2)

September 50 (0.3) 4.5 (0.07) 0 14.7 (0.6) 0 10.7 (0.1)

October 30 (0.1) 2.6 (0.02) 45 (0.03) 10.5 (0.6) 0 13.6 (0.01)

November 53 (0.3) 0 45 (0.05) 11.3 (0.6) 0 8.3 (0.1)

December 50 (0.6) 0 33 (0.07) 15.8 (0.7) 0 7.4 (0.2)

Control 20 (0.1) 5.6 (0.02) 0 38.7 (1.5) 0 15.7 (0.08)

Values in parenthesis indicate S.D. of the mean.a P values after square root transformation.

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Fig. 1. Relationship of the absorbance of aqueous extracts of P. dulce (seeds and monthly harvested leaves) with the mycelial

inhibition of B. cinerea , P. digitatum and R. stolonifer. Vertical bars indicate S.D. of the mean.


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Fig. 2. Relationship of the absorbance of ethanolic extracts of P. dulce (seeds and monthly harvested leaves) with the mycelial

inhibition of B. cinerea , P. digitatum and R. stolonifer. Vertical bars indicate S.D. of the mean.


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Fig. 3. Relationship of the absorbance of aqueous extracts of P. dulce (seeds and monthly harvested leaves) with sporulation of B.

cinerea , P. digitatum and R. stolonifer . Vertical bars indicate S.D. of the mean.


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Fig. 4. Relationship of the absorbance of ethanolic extracts of P. dulce (seeds and monthly harvested leaves) with sporulation of B.

cinerea , P. digitatum and R. stolonifer . Vertical bars indicate S.D. of the mean.


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/ 304/4. Discussion

/ 305/ Overall, we observed that the degree of fungici-

/ 306/dal or fungistatic activity was not constant during

/ 307/the sampling season. In general, Botrytis develop-

/ 308/ment during in vitro and in situ experiments was

/ 309/more affected by extracts from leaves harvested in

/ 310/cold, dry and also hot months. Aqueous extracts

/ 311/and powders from leaves harvested from October

/ 312/to February inhibited the mycelial growth and

/ 313/sporulation of this fungus in in vitro studies while

/ 314/powders from October harvested leaves also

/ 315/reduced fungal development of strawberry (coolest

/ 316/season). Similarly, leaves harvested in April and

/ 317/June (driest and hottest season) inhibited mycelial

/ 318/development and fruit infection of strawberry.

/ 319/Others have reported the fungicidal effect accord-

/ 320/ing to a specific geographical area or active

/ 321/compound. Lira-Saldıvar et al. (2001) found

/ 322/differences in the fungicidal effect of leaf extracts

/ 323/of Larrea tridentata against F. oxysporum , har-

/ 324/vested in two different areas of the dessert of

/ 325/Chihuahua and Sonora, Mexico. In that study the


Table 2

Rf and fluorescence of flavonols (kaempferol) in aqueous and

ethanolic extracts of P. dulce seeds and leaves harvested

monthly by thin layer chromatography

Plant organ Extract

Aqueous Ethanolic

Rf UV (365 nm) Rf UV (365 nm)

Seed �/ �/ �/ �/

Leaves

January 0.95 Yellow 0.91 Yellow

February 0.95 Yellow 0.91 Yellow

March �/ �/ 0.93 Yellow

April 0.95 Yellow 0.93 Yellow

May �/ �/ 0.93 Yellow

June �/ �/ 0.91 Yellow

July �/ �/ �/ �/

August �/ �/ 0.90 Yellow

September 0.75 Yellow 0.90 Yellow

October 0.75 Yellow 0.90 Yellow

November �/ �/ 0.90 Yellow

December �/ �/ 0.90 Yellow

Kaempferol 0.91 Yellow�/green 0.90 Yellow�/green

�/, Zero values.

Table 3

Effect of aqueous extracts and powders of seeds and monthly harvested leaves of P. dulce on percentage infection and number of

decayed fruit by B. cinerea and R. stolonifer on strawberry fruit

Plant organ Aqueous extracts Powders

Percentage infection P�/0.05a Number of decayed fruit Percentage infection P�/0.01b Number of decayed fruit

B. cinerea R. stolonifer B. cinerea

Seeds 85 32 5 16 4

Leaves

January 50 18 3 26 7

February 55 12 10 36 9

March 84 31 3 24 6

April 31 13.0 5 18 5

May 48 12 8 24 6

June 47 19 0 18 5

July 43 17 0 18 5

August 27 11 0 24 6

September 58 21 4 30 8

October 57 15 13 16 4

November 63 9 16 32 8

December 54 15 4 18 5

Control 48 15 14 34 9

a Percentage infection based on two replications of 40 fruit each.b Percentage infection based on two replications of 25 fruit each.


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/326 /highest concentration of resins with antifungal/327 /properties was found in those leaves harvested

/328 /from the Sonoran dessert. The authors stated that

/329 /these differences might be due to the different

/330 /latitude and altitude between the Sonoran and the

/331 /Chihuahuan dessert. Espinosa-Garcıa and Lan-

/332 /genheim (1991a,b) reported that the fungus Pes-

/333 /talotia subcutilaris was differentially affected

/334 /according to the presence or absence of a parti-/335 /cular active compound present in the tree named

/336 /Hymenea spp. Espinosa-Garcıa (2001), highlights

/337 /the significance of identifying the chemical profile

/338 /of the secondary metabolites of those plants with

/339 /pesticidal and fungicidal effects. The fungicidal or

/340 /fungistatic effects of the monthly samples tested in

/341 /this present research, might be related to changes

/342 /in environmental conditions i.e. temperature and/343 /relative humidity, hence differences with the pre-

/344 /sence and quantity of specific active compounds

/345 /with fungicidal activity.

/346 / In this study, we did not observe a defined

/347 /relationship between the high absorbance values of

/348 /seeds and the monthly harvested leaves with

/349 /fungicidal or fungistatic effects. However, we did

/350 /observe a relationship between the inhibition of/351 /mycelial growth and less sporulation with high

/352 /values of absorbance. According to the literature,

/353 /the yellow�/green fluoresces zone at UV 365 nm is

/354 /likely to be the kaempferol compound (Wagner et

/355 /al., 1984). The obtained Rf values in this study

/356 /suggest the presence of this compound. However,

/357 /an Rf at 0.75 may indicate that the kaempferol is

/358 /bonded to other compounds such as glycosides./359 /Secondary metabolites are a mixture of different

/360 /active compounds, each of them acting according

/361 /to concentration and structure. In this present

/362 /study, powder application on strawberry fruit

/363 /compared with aqueous extracts had a better

/364 /fungicidal effect, since powders were not subjected

/365 /to an extraction process, they had various and

/366 /different active compounds that might be acting all/367 /together. However, other evaluations carried out

/368 /in our laboratory have demonstrated the fungici-

/369 /dal effects of the isolated compound kaempferol

/370 /against various postharvest fungi (data not

/371 /shown). This compound has been also reported

/372 /with fungicidal activity against F. oxysporum on

/373 /carnation (Curir et al., 2001).

/ 374/ To date, chemical analyses of leaves and seeds of/ 375/P. dulce have led to the identification of other

/ 376/saponines and flavonols such as quercitin (Nigam

/ 377/and Mitra, 1970; Sahu and Mahato, 1994; Nigam

/ 378/and Gopal, 1997). Therefore, the elucidation of

/ 379/other chemical structures with bioactive potential

/ 380/in seeds and leaves of this plant species against

/ 381/postharvest decay microorganisms of fruit need to

/ 382/be investigated.

/ 383/Acknowledgements

/ 384/ To the National Polytechnic Institute (Grant:

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/480 /



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2003 seasonal evaluation of the postharvest fungicidal activity of

Science

fungicidal effect of

fungicidal properties

aqueous extracts

extracts of leaves

fungicidal23 effect

strawberry fruit snow

botrytis cinerea

highest fungistatic