Assessing Agronomic Characteristics and Physicochemical Properties of Selected Watermelon Varieties Grown in Tunisia

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1 The Afrin Journl of Plnt Siene nd Biotehnology 29 Globl Siene Books Assessing Agronomi Chrteristis nd Physiohemil Properties of Seleted Wtermelon Vrieties Grown in Tunisi Imen Tlili 1,2 Chfik Hdider 1* Ridh Ilhy 1,2 Hger Jebri 1 1 Lbortory of Biotehnology nd Plnt Physiology, Ntionl Agriulturl Reserh Institute of Tunisi. Hedi Krry street, 249 Arin, Tunis, Tunisi 2 Deprtment of Biology, Fulty of Sienes, Bizerte, Tunisi Corresponding uthor: * hdider.hfik@ires.grinet.tn ABSTRACT Wtermelon (Citrullus lntus (Thunb.) Mnsfeld) is populr vegetble. Interest in ssessing gronomi nd biotive ompounds with ntioxidnt pity nd potentil helth benefits in wtermelon is inresing. Besides some gronomi hrteristis, the vribility of lyopene nd totl phenoli ontents of six wtermelon vrieties (four ommeril ultivrs Armis, Crimson Sweet, Dumr, Giz, nd two new seletions P53 nd P43 developed by the Ntionl Agriulturl Reserh Institute of Tunisi) s influened by smpling ws determined. Giz nd P53 were hrterized by smll fruits with thin rind nd reltively high mount nd lrge seeds. Signifint differenes were found in lyopene nd phenoli ontents between wtermelon vrieties. Lyopene ontent in P53 nd Giz ws more thn 2-fold higher thn tht in Dumr nd P43. The highest phenoli vlue (9.28 mg GAE kg -1 FW) ws shown by Dumr. The lyopene nd totl phenoli ontents vried signifintly between studied smpling s but not in ll vrieties. Generlly, highest vlues for lyopene nd totl phenolis were obtined for hert nd stem end s. For ll studied wtermelon vrieties, lyopene ws best orrelted with rind thikness nd 1-seeds weight. This study demonstrtes tht the mount of lyopene nd totl phenolis were both influened by genotype nd smpling, emphsizing the need to dopt stndrdized nd doumented smpling methods when ssessing qulity ttributes, nd to evlute wtermelon biodiversity in order to improve its nutritionl vlue. Keywords: Citrullus lntus (Thunb.) Mnsfeld, lyopene, phenolis, qulity, smpling INTRODUCTION Wtermelon is one of the min vegetble rops grown nd onsumed in Tunisi, nd is muh ppreited s n exellent refreshing summer fruit. In ft, it rnks fourth in surfe mong vegetble rops (Jebri 23). In 26, pproximtely 12,4 h were dedited to this rop, produing up to 34, t of wtermelon (DGPA 26). Wtermelon ontins, in ddition to vitmin A, C, E, potssium, itrulline nd rginine, vriety of nturl ntioxidnts suh s rotenoids nd phenolis (Perkins-Vezie 22; Perkins-Vezie et l. 27). In reent yers, nturl ompounds, prtiulrly lyopene nd phenolis, hve reeived gret interest beuse of their ntioxidnt tivity ginst free rdils, suggesting protetive roles in reduing risk of hroni diseses, suh s ner nd rdiovsulr disese (Rie-Evns et l. 1996; Giovnui 1999; Agrwl nd Ro 2). Wtermelon umultes lyopene s mjor mesorp rotenoids (7-9%) giving the fruit its typil red olour (Tomes et l. 1963; Tdmor et l. 25). This red pigment hs the highest ntioxidnt tivity mong ll dietry ntioxidnts (Di Msio et l. 1989; George et l. 24). It hs been reported tht wtermelon serves s biovilble soure of lyopene in the diet nd tht this biovilbility to humns from fresh wtermelon juie is similr to tht of het-proessed tomtoes (Edwrds et l. 23). In ddition, it hs been reported tht wtermelon ontins moderte mount of phenolis (Perkins-Vezie 22; Brt et l. 26; Mélo et l. 26). These ompounds re importnt seondry metbolites in plnts nd beuse of their struture, phenoli ompounds re very effiient svengers of peroxyl rdils (Hlliwell 1996; Aruom 1999). In ddition, mny phenoli ompounds n exhibit phrmologil effets (Lrson 1988; Mnh et l. 1998). Despite their gret helth benefit, few studies hve reported on lyopene nd totl phenoli ontents of wtermelon vrieties. In Tunisi, ttention is now pid to ntioxidnt omponent studies. In ft, their estimte is beoming n importnt evlution prmeter for the nutritionl qulity of food (Lenui et l. 26). Tlili et l. (27) reently highlighted tht wtermelon n be onsidered n importnt soure of lyopene. However, further studies on ntioxidnt omponents of wtermelon vrieties grown under Tunisin environmentl onditions re needed. In tomto fruit, Hdider et l. (27) showed lrge vrition in lyopene ontent between ultivrs. Also, Ilhy nd Hdider (27) showed tht lyopene ontent in tomto vry with the stge of mturity. It is known tht the mount of eh ntioxidnt in vegetbles is strongly influened by vrietl differenes nd lrge number of externl ftors suh s grotehnil proess, limti onditions nd ripeness during hrvest nd post hrvest mnipultion (Wtermn nd Mole 1994; Abushit et l. 2; Dums et l. 23). Reently, Perkins- Vezie et l. (26) nd Perkins-Vezie nd Dvis (27) emphsized the importne of ultivrs nd smpling s when ssessing the lyopene nd soluble solids ontent in wtermelons. In ft, in lrge fruited wtermelon where only portion of the fruit is fesibly tested for qulity, n urte nd reproduible smpling method must be used. Therefore, nd bsed on these fts the im of this study ws to investigte some gronomi nd physiohemil properties of seleted wtermelon vrieties grown in Tunisi s influened by smpling. MATERIALS AND METHODS Field experiment Field experiments were onduted in 27 t the Reserh nd Experimentl Sttion of Teboulb, Monstir, Tunisi. A totl of six Reeived: 17 November, 29. Aepted: 28 November, 29. Originl Reserh Pper

2 The Afrin Journl of Plnt Siene nd Biotehnology 3 (Speil Issue 1), Globl Siene Books wtermelon vrieties inluding four ommeril ultivrs onsidered importnt in Tunisi nd two new seletions P53 nd P43, seleted by the Ntionl Agriulturl Reserh Institute of Tunisi, were used in this experiment. The ommeril ultivrs were Crimson Sweet (Cluse), Dumr (Nunhems), Armis (Nunhems) nd Giz (Egyptin vriety seleted nd improved by the Ntionl Agriulturl Reserh Institute of Tunisi). Sowing ws rried out on the 5 th Mrh 27 in plug-seedling trys. Wtermelons were trnsplnted on the 24 th April 27 into sndy soil on blk plsti mulh, with n intr-row sping of 125 m nd n inter-row sping of 15 m. Four bloks were used with 1 plnts per vriety. After trnsplnting, drip irrigtion ws pplied with 4 L h 1 drippers pled t.4 m intervls long the irrigtion line. Drip irrigtion rn for 1-3 h, t 1-2 dy intervls, depending on potentil evpotrnspirtion for reserh sttion, limte dt nd rop oeffiient. The prodution methods were in ordne with the proedures utilized by the reserh nd experimentl sttion of Teboulb, Monstir, Tunisi nd reommended by INRAT. They inluded fertiliztion with syntheti hemil fertilizers (145 kg N h 1, 14 kg P 2 O 5 h 1, 21 kg K 2 O h 1 ). Chemil fertilizer solution ws dded to wter irrigtion by pump injetion twie week. The prodution methods lso inluded hnd weeding ontrol nd plnt pthogen ontrol with syntheti hemil pestiides. Imidlopride (Promohimie, Tunis, Tunisi) (2 g L 1 ) ws used to redue phids. Aetmipride (SEPCM, tunis, Tunisi) (2 g L 1 ) ws pplied to redue thrips. Abmetine (Bioprotetion, tunis, Tunisi) (18 g L 1 ) ws used to redue mites. All these pestiides were pplied one yle. All vrieties were simultneously grown in n open field nd subjeted to identil ulturl prties in order to minimise the effets of environmentl onditions nd mximize those relted to genotype. Ripe wtermelons were hrvested in July. Field ripeness ws judged by vrious methods inluding tendril browning, yellowing of the ground spot, nd loss of surfe gloss nd by thumping sound whih hnges from metlli ringing when immture to soft hollow sound t mturity. Wtermelons were seleted rndomly from the different bloks. Four ripe fruits were hrvested per blok per vriety. All the fruits were trnsported refully to the lbortory for nlysis to void internl bruising. Fruit smpling Fruit were ut longitudinlly from stem end to blossom end through the ground spot, nd tissue smples were tken from four different s: blossom end, hert, stem end nd peripherl (between loulr nd rind ). Soluble solids ontent ( Brix) nd ph ws rried out immeditely on the juie obtined from mixed tissue fruit. For further nlysis, bout 25 g of flesh without seeds per smpling per fruit ws olleted, wrpped with luminium, pled into plsti bgs nd pled quikly t -8 C. Chemils Glli id ws obtined from Sigm-Aldrih, Chemil Co., Miln. Other regents were of nlytil grde. Determintion of gronomi hrteristis Wtermelon yield ws expressed by fruit weight per plnt (kg). Rind thikness (from peel to strt of pink olour) ws mesured to.1 mm using llipers t the ground spot nd diretly bove the ground spot. After seprting them mnully, the individul number nd 1-seeds weight of fruit were determined. Determintion of physiohemil properties Soluble solids ontent in wtermelon ( Brix) ws mesured by utting wedge of flesh from ll smpling s nd squeezing the juie into digitl refrtometer (Atgo PR-1, NSG Preision Cells, In., Frmingdle, NY, USA) librted with 1% surose solution. Only melons with men soluble solids ontent 8% were smpled for lyopene to ensure tht ll fruits were fully ripe. ph ws ssessed on the juie obtined from mixed tissue fruit from ll smpling s using n eletroni ph meter (WTW, Miroproessor ph Meter, PH 539, Weilheim, Germny). Frozen smples of different smpling s from every fruit were ground in mortr nd pestle nd gin with lbortory blender. Lyopene extrtion nd determintion were onduted s desribed by Fish et l. (22). The method uses mixture of hexne/ethnol/etone (2: 1: 1, v/v/v) ontining.5% butylted hydroxytoluene (BHT). The bsorbne of the hexne extrt ws mesured t 53 nm with Ceil BioQuest CE 251 spetrophotometer (Ceil Instruments Ltd., Cmbridge, UK). Zeroing ws done with hexne. During nlysis, some preutions like working in redued luminosity room nd wrpping glss mteril with luminium were dopted to minimise lyopene loss by photo-oxidtion (Fish et l. 22). A molr extintion oeffiient = L mol -1 m -1 ws used for lyopene ontent determintion (Beerh nd Sidpp 1959) nd results were expressed in mg kg 1 FW. Totl phenoli ontent ws determined ording to the Folin Ciolteu olorimetri method s modified by Singleton et l. (1999) nd Eberhrdt et l. (2). Eh smple (4 g) ws extrted with 1 ml of methnol for 24 h, fter whih 125 L of this extrt ws diluted 1: 5 (v/v) with distilled wter. Then 125 L of the diluted extrt ws mixed with 5 L of distilled wter in test tube, 125 L of Folin Ciolteu regent ws dded nd the mixture ws llowed to stnd for 3 min. Therefter, 1.25 ml of 7 g L 1 sodium rbonte solution ws dded nd the finl volume ws mde up to 3 ml with distilled wter. Eh smple ws llowed to stnd for 9 min t room temperture before mesurement t 76 nm ginst blnk in spetrophotometer (Ceil BioQuest CE 251). The liner reding of the stndrd urve ws from to 3 g glli id ml 1. Results were expressed in mg glli id equivlent (GAE) kg 1 FW. Sttistil nlysis The bsi plots of the experiment were spred out in rndomised experimentl design in four omplete bloks. The nlysis of vrine ws performed ording to the Generl Liner Models (GLM) proedure developed by the Sttistil Anlysis Systems Institute (SAS Inst., V.6.1, Cry, NC, US). Mens nd stndrd errors were lulted. Correltions were done using Person s orreltion oeffiient t P<.5. LSD test ws pplied to estblish signifint differenes between mens with 95% onfidene level. RESULTS AND DISCUSSION Agronomi hrteristis The most importnt gronomi hrteristis of the different studied wtermelon vrieties re presented in Tble 1. The yield of mrketble fruit of the studied wtermelon vrieties vried from 5.2 to 7.8 kg plnt -1 but no sttistil differenes were found between vrieties. Regrding verge fruit weight, the vrieties produed fruit with n verge weight rnging between 3 nd 6.3 kg. Giz nd P53 produed smll-sized fruit. Signifint differenes in rind thikness were found between studied wtermelon vrieties (P<.1), vrying from 8.5 to 14.5 mm for Giz nd Crimson Sweet vrieties, respetively. Similrly, differenes in verge seed number per fruit were signifint between studied wtermelon vrieties (P<.1), vrying from to 867 seeds per fruit for seedless Armis nd P53 vrieties, respetively. Conerning the 1-seeds weight, differenes were lso signifint between studied wtermelon vrieties (P<.1) with vlues rnging between nd 1.4 g for seedless Armis nd P53, respetively. Giz nd P53 were hrterized by smll fruits with thin rind. These vrieties lso hd reltively high mount of lrge seeds. Physiohemil properties The soluble solids ontent, ph, lyopene nd totl phenoli ontents vlues of the different studied wtermelon vrieties within different smpling s re listed in Tble 2. When verged ross smpling s, the soluble solids vried 8

3 Agronomi nd physiohemil hrteristis of seleted wtermelon vrieties. Tlili et l. Tble 1 Some gronomi hrteristis of the different studied wtermelon vrieties. Cultivrs Yield fruit weight per plnt (kg) Averge fruit weight (kg) Rind thikness (mm) Averge seed number per fruit 1-seeds weight (g) Crimson Sweet d 4.1 Giz b 8.3 b b Dumr b 789 b 4.8 P P b 9. b Armis e. e Signifine ns ** ** ** ** Signifine: ** Probbility level of 1%; ns: not signifint. Vlues in the sme olumn followed by the sme letters do not differ signifintly (LSD test, P<.5). Tble 2 Physiohemil properties of the different studied wtermelon vrieties within different smpling s Cultivrs Soluble solids ( Brix) ph Lyopene (mg kg 1 FW) Totl phenoli (mg GAE kg 1 FW) Crimson Sweet blossom end 8.9 ±.4 b 5.72 ± ± ± 3 b stem end 9.3 ±.5 b 5.71 ± ± ± 3 hert 1.1 ± ± ± ± 6 b peripherl 7.8 ± ± ± ± 3 men 9. A 5.74 C 51.5 C B Giz blossom end 8.4 ±.6 b 5.93 ± ± ± 7 b stem end 8.2 ±.6 b 6.4 ± ± 5.3 b ± 5 hert 9. ± ± ± ± 3 peripherl 7.6 ±.4 b 5.97 ± ± 1.8b 71.5 ± 3 men 8.3 A 5.96 A 92.4 A C Dumr blossom end 8.4 ± ± ± 1.1 b ± 3 stem end 9.3 ±.5 b 5.89 ± ± 1.7 b ± 3 hert 1.1 ± ± ± ± 5 peripherl 7.8 ± ± ± 1. b ± 2 b men 8.9 A 5.81 BC 42.1 D 9.28 A P43 blossom end 8.9 ±.4 b 5.95 ± ± ± 4 stem end 9. ±.6 b 5.85 ± ± ± 5 hert 9.9 ± ± ± ± 5 b peripherl 7.3 ± ± ± ± 1 men 8.8 A 5.95 A 44.1 CD 74.9 B P53 blossom end 7.8 ±.5 b 5.78 ± ± 3.9 b ± 1 stem end 8.6 ± ± ± ± 3 hert 8.8 ± ± ± ± 3 peripherl 7.4 ±.4 b 5.94 ± ± ± 6 men 8.2 A 5.91AB A D Armis blossom end 8.9 ±.6 b 6.1 ± ± 3. b 58.3 ± 5 stem end 9.6 ±.6 b 5.95 ± ± ± 2 b hert 1.1 ± ± ± ± 1 peripherl 8.1 ± ± ± 1.5 b 6.64 ± 3 b men 9.2 A 6.2 A B BC Lower se letters indite men seprtion within olumn nd smpling by LSD test, P <.5. Cpitl letters indite men seprtion mong mens within olumn by LSD test, P <.5. between 8.2 nd 9.2 Brix nd ws not different mong vrieties (P>.5). These vlues revel tht ll fruits were fully ripe. In ontrst, differenes in soluble solids ontent were signifint between studied smpling s within ll vrieties (P<.1). For ll vrieties, the highest men vlue ws obtined for the hert with 9.7 Brix nd the lowest ws obtined for the peripherl with 7.7 Brix (Fig. 1A). These results re onsistent with those reported by Perkins-Vezie nd Dvis (27), who found tht soluble solids differ mong smpling s in wtermelon ultivrs nd tht the loule nd hert s hve the highest vlues. Regrding ph, men vlues were signifintly different between studied wtermelon vrieties (P<.5). Signifintly higher vlues were reorded in Armis, Giz nd P43 nd lower vlues were reorded in Crimson Sweet nd Dumr. Our results gree with those of Perkins-Vezie nd Collins (26) who reported signifint differene in ph between wtermelon ultivrs. In ontrst, differenes in ph were not signifint between studied smpling s in ll vrieties (P>.5). This result is in disgreement with those of Perkins-Vezie nd Dvis (27) who reported signifint differenes between mesured ph in different smpling s. For lyopene ontent, the obtined dt showed tht vlues vried signifintly between studied wtermelon vrieties (P<.1). When verged ross smpling s, lyopene ontent rehed very high levels (>9 mg kg 1 FW) nd vried from 42.1 to mg kg 1 FW. The highest vlues were obtined for P53 nd Giz with nd 92.4 mg kg 1 FW, respetively. The lowest vlues were obtined for Dumr nd P43. P53 nd Giz hve more thn 2-fold lyopene thn Dumr nd P43. The results re in greement with those reported by Perkins- Vezie et l. (26) who found tht lyopene ontent vries mong wtermelon ultivrs nd n reh very high vlues ttining 99.8 mg kg 1 FW in v. Xite, while studying the rotenoid omposition of 5 wtermelon ultivrs. The dt lso proved tht wtermelon n onstitute predominnt soure of lyopene in the Tunisin diet beuse of its vilbility nd high onsumption, s ws reported for the 9

4 The Afrin Journl of Plnt Siene nd Biotehnology 3 (Speil Issue 1), Globl Siene Books Brix ph Lyopene (mg kg -1 FW) Totl phenolis (mg GAE kg -1 FW) b (A) b b Stem end Hert Peripherl (B) Stem end Hert Peripherl (C) b Stem end (D) A B C D Stem end Amerin diet (Vinson et l. 1998). In ddition, the results showed tht lyopene ontent ws signifintly different between studied smpling s, exept for Crimson Sweet nd P43 (P<.1). Nevertheless, when verged ross vrieties, the highest vlues were obtined for hert nd stem end s with nd mg kg 1 FW, respetively (Fig. 1C). The lowest vlue ws obtined for the peripherl (57.46 mg kg 1 FW). Our results onfirm those of Perkins-Vezie nd Dvis (27) who reported tht lyopene ontent differs signifintly mong smpling s in wtermelon ultivrs nd Hert b Hert Peripherl Peripherl Fig. 1 Averge soluble solids ( Brix) (A), ph (B), lyopene (mg kg -1 FW) (C) nd totl phenolis (mg GAE kg -1 FW) (D) for ll wtermelon ultivrs within the different smpling s. Vlues for eh smpling with the sme letters re not signifintly different (LSD test, P<.5). highlights the importne of smpling in determining lyopene ontent in wtermelon fruit. Totl phenoli ontent vried signifintly between studied wtermelon vrieties (P<.1). When verged ross smpling s, vlues obtined rnged from to 9.28 mg GAE kg 1 FW. The highest totl phenoli ontent vlue ws shown by Dumr nd the lowest vlue by P53. Our results re onsistent with those of Brt et l. (26) who reported tht wtermelon fruit ontins moderte mount of phenoli ompounds rehing 116 mg GAE kg 1 FW. Mélo et l. (26) lso reported tht totl phenoli ontent in wtermelon n reh 98.1 mg tehin equivlent kg 1 FW. Higher vlues rnging between mg GAE kg 1 FW were obtined in red fleshed wtermelon ultivrs by Perkins-Vezie (22) but without differenes between them. These divergent results were probbly due to vriety or environmentl differenes. Although phenoli ontent in wtermelons ws only moderte ompred to other potentil vegetbles, suh s onion rehing 761 GAE kg 1 FW (Brt et l. 26), its high onsumption in Tunisi diet mkes them good soure of phenols s ws reported for Amerin nd Spnish diet. In ft, Vinson et l. (21) reported tht wtermelon is the forth mong eight fruits tht provide 8% of the dily phenols in the Amerin diet nd 5% of the Spnish diet. The results lso showed tht the totl phenoli ontent vried signifintly between studied smpling within ll vrieties, exept for P53 (P<.1). Nevertheless, for ll vrieties, the men vlues of totl phenoli ontent ws highest in stem end with mg GAE kg 1 FW followed by the hert with mg GAE kg 1 FW. The lowest vlues were obtined in blossom end nd peripherl s with 67.2 mg GAE kg 1 FW nd mg GAE kg 1 FW, respetively (Fig. 1D). To our knowledge, these re the first results desribing distribution of totl phenolis in wtermelon fruit. Correltion study Mny uthors studied the orreltion between lyopene nd phenolis nd other hrteristis in mny fruits, prtiulrly tomto (Giovnelli et l. 1999; Aris et l. 2; Brndt et l. 26). However, little of informtion is known bout these types of orreltions in wtermelon fruit. Correltion oeffiients mong fruit vribles mesured from different evluted wtermelon vrieties re listed in Tble 3. For ll studied wtermelon vrieties, lyopene ws best orrelted with rind thikness nd seed weight. Rind thikness ws negtively nd signifintly orrelted with lyopene (R 2 = -.54) inditing tht vrieties with thin rind thikness orresponded to higher lyopene ontent. Perkins- Vezie nd Collins (26) reported wek orreltion between rind thikness nd lyopene (R 2 = -.36). The 1- seeds weight ws positively nd signifintly orrelted with lyopene (R 2 =.56). A signifint but wek negtive orreltion ws found between phenoli nd lyopene ontents (R 2 = -.35). This is unlike tht found in tomto (R 2 =.42) by Mrtinez-Vlverde et l. (22). Soluble solids ontent, ph nd seed number were not signifintly orrelted with lyopene. Soluble solids ontent ws the only ttribute positively orrelted with totl phenoli ontent (R 2 =.36). CONCLUSIONS This study onfirmed the importnt role plyed by genetis in determining ntioxidnt omponents of fresh wtermelon Tble 3 Correltion oeffiients mong vribles mesured of fruit from the different studied wtermelon vrieties. Vribles Lyopene Phenolis Brix ph Rind thikness Seed number 1-seeds weight Lyopene -.35** **.11.56** Phenolis -.35**.36** Brix ** ph **: signifint orreltions t p <.1 level, using Person s orreltion oeffiient. Lyopene, totl phenolis, Brix nd ph vlues were verged ross smpling s. 1

5 Agronomi nd physiohemil hrteristis of seleted wtermelon vrieties. Tlili et l. nd highlights the importne of stndrdized nd doumented smpling methods when determining soluble solids ontent, lyopene nd phenols in wtermelon vrieties. In ddition, the present study emphsizes the promising use of vrieties P53 nd Giz for their very high lyopene ontent s helthy qulity fruit nd for future breeding progrms. The vribility deteted mong the four ommeril wtermelon ultivrs nd mong the two new dvned seletions emphsized n existing unexploited vribility in wtermelon germplsm nd stresses the need to evlute more wtermelon genotypes nd to support onventionl breeding progrms to improve wtermelon nutritionl vlue. REFERENCES Abushit AA, Dood HG, Bis PA (2) Chnge in rotenoids nd ntioxidnt vitmins in tomto s funtion of vrietl nd tehnologil ftors. Journl of Agriulturl Food nd Chemistry 48, Agrwl S, Ro AV (2) Tomto lyopene nd its role in humn helth nd hroni diseses. 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