Heterotic effects in triploid watermelon hybrids

Transcription

1 FF Souz et l. Crop Breeding nd Applied Biotehnology 5: , 2005 Brzilin Soiety of Plnt Breeding. Printed in Brzil Heteroti effets in triploid wtermelon hyrids Flávio de Frnç Souz 1*, Mnoel Ailio de Queiroz 2, nd Rit de Cássi Souz Dis 3 Reeived 4 Ferury 2005 Aepted 8 August 2005 ABSTRACT - Twelve experimentl triploid hyrids were evluted to estimte heteroti effets for some plnt nd fruit trits in triploid wtermelon (Citrullus lntus). Tiffny, triploid hyrid ws used s stndrd ultivr. The experiment in rndomized lok design ws rried out in three replitions t the Experimentl Sttion of Emrp Semi-Árido in Petrolin, stte of Pernmuo. The following trits were evluted: erliness, prolifiy, min stem length, fruit weight, solule solid ontent, rind thikness, flesh olor, nd hollow hert disorder. All evluted trits presented signifint vriility mong the hyrids. Mid-prent heterosis effets were found s well s the stndrd ultivr rnging from negtive to positive vlues ttining up to 300% prolifiy in some ses. The tetrploid lines should e improved for severl trits in order to produe erlier triploid hyrids with more ompt plnts nd fruits without the hollow hert disorder. Key words: Citrullus lntus, seedless wtermelon, polyploidy. INTRODUCTION Triploid wtermelon plnts, whih produe seedless fruits, re hyrids nd therefore prone to show heteroti effets. These effets n e of vlue to hieve superior genotypes tht inlude more desirle fetures, e. g. phenotypi stility under stress onditions, higher fruit yield, mong others. When the first seedless wtermelon hyrids ppered, the need of estlishing more heteroti omintions eme evident, espeilly suh tht with lower numer of white immture seeds per fruit (Kihr 1951). Heterosis is mnifesttion of the hyrid vigor expressed y the differene etween genertion F 1 nd the men vlue of the prents. It n lso e mesured in reltion to the etter prent (heteroeltiosis) or to stndrd ultivr (Pternini 1973). Therefore, heterosis is essentilly phenotypi effet nd is defined s the performne of the desendents (Myo 1980). Heteroti effets hve een studied in some polyploidy speies suh s lflf nd potto, minly for yield-relted trits. Positive heterosis ws oserved in most of these ses (Cuillos nd Plisted 1976, Ry et l. 1998). 1 Emrp Rondôni, BR 364, km 5,5, C. P. 406, , Porto Velho, RO, Brsil. E-mil: flviofs@pfro.emrp.r 2 DTCS-UNEB, C. P. 171, , Juzeiro, BA, Brsil 3 Emrp Semi-Árido, BR 428, km 152, Zon Rurl, C. P. 23, , Petrolin, PE, Brsil 280 Crop Breeding nd Applied Biotehnology 5: , 2005

2 Heteroti effets in triploid wtermelon hyrids Regrding the triploid wtermelons hyrids, prtilly no reserh work on heteroti effets hs een done even with diploid genotypes, despite the importne nd usefulness of heterosis in wtermelon plnt reeding. Nth nd Dutt (1970) mentioned tht some hyrid omintions showed over 50% heterosis for yield nd fruit qulity. Kle nd Seshdri (1988) deteted heterosis for yield nd fruit qulity-relted trits in some rosses of Indin with exoti ultivrs. Ferreir et l. (2002) evluted 21 experimentl wtermelon hyrids nd deteted positive heteroti effets in reltion to the prent s men for the numer of fruits per plnt, fruit weight, width of the flesh, trnsversl dimeter of the fruit, numer of seeds per fruit, nd the weight of hundred seeds. This study hd the ojetive to determine the heteroti effets relted to the fruit yield nd qulity in 12 hyrids nd their prents (three tetrploid nd four diploid lines of ommeril ultivrs). MATERIAL AND METHODS The experimentl triploid hyrids were otined y rosses mong three tetrploid lines (LT7-48.1, LT nd LTCC-24) nd four diploid lines from selfing ommeril ultivrs (Crimson Sweet, Perol, New Hmpshire Midget, nd Chrleston Gry). The triploid seeds were produed through hnd pollintion. The mle nd femle flowers were proteted efore nthesis using devie mde of plsti up stpled to stik whih kept the devie in the ground nd prevented pollen ontmintion y ees. Normlly, two mle flowers re proteted to pollinte femle flower. After nthesis the mle flowers were removed from the plnt nd rued onto the tetrploid stigms. The femle flower ws tgged nd proteted gin for t lest one dy (Figure 1). Mture fruits of ll tretments were hrvested nd the seeds were extrted nd left in the shde to dry. Seeds were sown in try filled with humus vermiulite mixture nd the seedlings trnsplnted to the field fter 15 dys. The hyrids nd prents were grown t the Experimentl Sttion of Emrp Semi-Árido in Petrolin- PE, from April to August 1999, on Ltossol. The experiment ws rried out in rndomized lok design with three replitions. The plots hd seven plnts in rows sped 3.0 m prt nd 1.0 m etween plnts. The triploid hyrid Tiffny ws used s stndrd ultivr. To gurntee fruit prodution in the triploid plnts, n experimentl diploid hyrid ws used s pollintor. One suh plnt ws plnted t one nd nother t the other end of eh plot. The plnts were wtered y furrow irrigtion nd the rop mngement ws done ording to the speifi tehnil reommendtions for wtermelon rop. Fruits were hrvested 82 dys fter plnting. The tretments were evluted for the following trits: numer of dys to the emergene of the first femle flower (NDF); length of the min stem (LMS); numer of fruits per plnt (NFP); fruit weight (FW) in kilogrms; totl solule solid ontent (TSS), rind thikness (RT), flesh olor (FC) nd ourrene of hollow hert (OHH). The lst two trits were evluted using sle of grdes. The flesh olor ws grded from one to four (1 = deep red; 2 = light red; 3 = pink; 4 = white). The following sle ws estlished for the ourrene of hollow hert: 1 = sene of hollow hert; 2 = up to 10% hollow hert of the flesh; 3 = over 10% hollow hert of the flesh. The plnt trits of the five middle plnts in the row were evluted nd the fruit trits were determined y rndom smple of five fruits per plot. The vrine nlyses were performed ording to the rmdomized omplete lok model. The mens were ompred y the test of Sott nd Knott (1974) t 5% proility (Cruz 1997). Heterosis in reltion to the prent s men (Rmlho et l. 1990) nd the stndrd ultivr ws estimted ording to the following formule: H mp = F 1 (P i + P j )/2 nd H p = F 1 CP where H mp : is the heterosis in reltion to the prent s men; F 1 : hyrid men; P i nd P j : men performnes of eh prent; H p : heterosis in reltion to the stndrd ultivr; nd CP : men performne of the stndrd ultivr. The vlues were trnsformed to perentge for the prent men nd the stndrd ultivr. RESULTS AND DISCUSSION Signifint differenes were oserved mong the tretments for plnt nd fruit trits (Tles 1 nd 2). The Crop Breeding nd Applied Biotehnology 5: ,

3 FF Souz et l. Figure 1. Hnd pollintion of wtermelon showing: () proteted mle flower, () femle flower on the dy of nthesis, () two mle flowers nd one femle flower proteted in wtermelon plnt, (d) mle flower removed from the plnt nd rued onto the stigm, (e) fter the pollintion the femle flower is tgged nd proteted for one more dy. Arrow indites fruit set two dys fter pollintion prents showed gret vriility for ll trits. The tetrploid nd diploid lines presented rnge of vrition for severl trits, minly for erliness, prolifiy, fruit size, nd flesh olor. For erliness, hyrid 3 x 5 ws the ltest to flower nd ws omprle to the erliness of the tetrploid lines, ut muh lter thn the stndrd ultivr. There were no signifint differenes mong the other hyrid omintions nd lmost ll these hyrids showed negtive heterosis in reltion to the prent men or smll positive heterosis in reltion to the stndrd ultivr, i.e., they were erlier thn the tetrploid lines ut were lter thn the stndrd ultivr inditing tht the tetrploid lines should e improved for erliness. This trit presented non-dditive effets (Souz et l. 2002) inditing tht there is need to selet pir of lines whih n hieve the desirle erliness in the triploid rosses. 282 Crop Breeding nd Applied Biotehnology 5: , 2005

4 Heteroti effets in triploid wtermelon hyrids Hyrid 3 x 4 ws the most vigorous while the hyrids 1 x 4, 1 x 5, 2 x 5 nd 2 x 7 produed more ompt plnts, ut ll hyrids showed positive heterosis for this trit in reltion to the prent men nd the stndrd ultivr (Tle 1). Sine ompt plnts re interesting for frmers nd no hyrid performed etter thn the stndrd ultivr, this trit should lso e improved in the tetrploid lines. One of the lterntives ould e rossing with tetrploid lines of popultion Chrleston Tetr Numer 3 whih hs shorter stem. However, it introdues suseptiility to powdery mildew nd therefore requires the seletion of reominnts whih re resistnt to the disese ut mintin the shorter stem (Queiróz et l. 2001). The triploid hyrids 3 x 6 nd 3 x 7 showed high prolifiy, whih differentited them from the others, rehing heterosis over 130% (3 x 6) in reltion to the mid-prents nd 300% (3 x 7) in reltion to the stndrd ultivr. The remining hyrids hd positive heterosis in reltion to the prent men, most of them ove 50%. The sme tendeny ws however not oserved regrding the stndrd ultivr, whih hd negtive heterosis in some ses. If prolifi plnts with smll fruits re to e seleted the diploid prent New Hmpshire Midget nd the tetrploid line LTCC-24 should e onsidered due to their high speifi s well s generl omining ility for prolifiy, nd sine the numer of fruits per plnt inresed in their rosses (Souz et l. 2002) lthough they will hve to e seleted for other plnt nd fruit trits in order to produe ommeril hyrids. Positive heteroti effets for fruit weight were verified in reltion to the mid-prents nd the stndrd ultivr for hyrids 1 x 4 nd 1 x 7, whih shows tht the tetrploid line LT hd signifint positive heteroti effet on fruit weight. On the other hnd, the lines New Hmpshire Midget nd LTCC-24 hd prolifi hyrids of smller fruit size (Tle 1). Prolifiy is negtively orrelted with the fruit size, inditing tht the higher the numer of fruits per plnt, the smller they re (Ferreir et l. 2003). The fruit size defines the type of mrket for ultivr. In this se, hyrids with smll fruits nd high perentge of negtive heterosis in reltion to the stndrd ultivr ould e sold s ie ox type: 8 to 12 pounds per melon, while the hyrids from the LT line ould e delivered to mrkets whih prefer lrge fruits. However, the hyrids with smll fruits (3 x 4 nd 3 x 7) (Tles 1 nd 2) presented poor flesh olor nd sugr ontent The tetrploid lines from LTCC-24 therefore need to e improved for these trits, lthough the triploid hyrid 2 x 6 of good flesh olor nd sugr ontent, if ultivted in smll plnt sping, ould produe eptle fruits for smll-fruit mrkets. As the wtermelon fruit yield depends strongly on the numer of fruits nd men weight of fruit per plnt (Kle nd Seshdri 1988), more prolifi hyrids ould provide yield inreses, whih is desirle for most reeding progrms. Prolifi plnts lso offer greter flexiility to tilor different fruit sizes ording to mrket preferenes sine they n e djusted to different plnt spings. All hyrids, exept the ones derived from line LTCC- 24, hd stisftory sweet tste of flesh (over 10.0 Brix) prtiulrly 1 x 5 nd 1 x 7. The positive heteroti effets for sugr ontent exeeded the prent men y 3.0 to 24 % ut were very low when the stndrd ultivr ws onsidered. The lines LT nd LTCC-24, however, presented negtive heterosis over the stndrd ultivr for sugr ontent in most hyrids (Tle 2). New Hmpshire Midget hd low vlues for the solule solid ontent per se, ut ould e of help when improving the sugr ontent of hyrids. Ferreir et l. (2002) lso pointed out positive heteroti effets for solid solule ontents regrding this line. At tht time the uthors worked with diploid hyrids of this prentl. Aording to the sle of grdes to evlute the olor of the fruit flesh, negtive heterosis is the desirle result. The hyrids of LT nd LT , with the exeption of omintion 2 x 7, hd deep red flesh olor. The hyrids from LTCC-24 with Perol nd New Hmpshire Midget hd light red nd pink flesh olor (Tle 2). Hyrids from the New Hmpshire Midget line presented negtive heterosis in reltion to the mid-prents. This showed superiority regrding the prents, whih hd low performne per se. Hyrids 1 x 6, 2 x 7 nd ll hyrid omintions with LTCC-24 hd positive heterosis in reltion to the stndrd ultivr, whih shows tht their fruits do not meet the mrket stndrds. Some wtermelon fruits presented superfiil to deep rks in the flesh. This disorder is designted s hollow hert (Mohr 1986) nd disqulifies these fruits for the mrket. All triploid hyrids hd fruits with hollow hert inidene t different degrees (Tle 2). Tetrploid line LT is prone to hollow hert, trit tht hs ppered in its rosses with ll diploid lines (Tle 2). Although LTCC-24 did not present hollow hert per se, its hyrids hd deeply rked flesh, even when the diploid lines did not hve this prolem. Regrding the fruit qulity of triploid Crop Breeding nd Applied Biotehnology 5: ,

5 FF Souz et l. hyrids, the hollow hert of fruits is defet tht should e prior onern in wtermelon reeding progrms. Aording to Queiróz et l. (2001) there re different sets of tetrploid lines in the wtermelon reeding progrm t Emrp Semi-Árido, s well s diploid lines with different fruit struture from ommeril ultivrs. Therefore, rnge of triploid omintions n e rised y rossing different tetrploid lines with diploid lines from ommeril ultivrs in order to selet desirle triploid omintions. However, when seleting for triploid rosses without rks in the flesh the reeder hs to tke into onsidertion tht this trit hs presented non-dditive gene tion (Souz et l. 2002) nd the speifi omining ility of eh pir of lines should therefore e mjor onern. The thikness of the rind is relevnt trit in view of trnsporttion nd post-hrvest fruit onservtion. Very thik rinds (over 2.0 m) re however not ppreited y ustomers, who prefer thinner ones. The hyrids 1 x 4 nd 1 x 7 hd the thikest rind (Tle 2). Among the prentl lines, only LT7-48.1, Crimson Sweet nd Chrleston Gry presented thik rind nd trnsferred this trit to their hyrids (Tle 2). All LTCC-24 hyrids presented thin rind showing good omining ility for this trit (Souz et l. 2002). However, tough rind is not determined only y the rind thikness, sine the rind of some fruits tends to rek esily euse they hve the reessive llele e (explosive) (Mohr 1986). Therefore, in the triploid rosses there is need to selet ontrsting pirs of lines for this trit in order to hieve hyrid omintions with tough rinds. Aording to Mohr (1986), tough rind n e seleted y utting thin strip of rind (0.3 m thik nd 7.5 m long) nd end it into irle. If it forms omplete irle it is onsidered very tough, ut if it reks esily in the ttempt to shpe irle it is tender due to the explosive llele. Tle 1. Men vlues for the numer of dys to the first femle flower shooting (NDF), length of the min stem (LMS), numer of fruits per plnt (NF) nd fruit weight (FW). Heterosis in reltion to the mid-prents (H mp ) nd the stndrd ultivr (H p ) in three tetrploid lines, four diploid lines nd twelve wtermelon hyrids Tiffny (p) 1 NDF (dys) 41.7 d Men Reltive heterosis (%) LMS NF/P FW NDF LMS NF/P (m) (unit) kg Hmp Hp Hmp Hp Hmp Hp 2.7 d 2.6 e 6.29 d LT (1) LT (2) LTCC-24 (3) Crimson Sweet (4) Pérol (5) New H. Midget (6) Chrleston Gry (7) 1x4 1x5 1x6 1x7 2x4 2x5 2x6 2x7 3x4 3x5 3x6 3x d d d 3.6 d 4.1 d d 4.2 d 3.9 d e 1.7 e e 1.3 e 4.4 d 1.5 e 2.0 e 1.9 e 4.2 d 1.4 e 2.7 e 2.3 e e d 2.92 e e d e e 3.27 e 2.17 e 3.06 e p = stndrd ultivr (ommeril triploid ultivr) 2 Mens followed y the sme letter in the olumn did not differ y the Sott & Knott test t 5% proility FW Hmp Hp Crop Breeding nd Applied Biotehnology 5: , 2005

6 Heteroti effets in triploid wtermelon hyrids Tle 2. Men vlues for the solule solid ontent (TSS), flesh olor (FC), ourrene of hollow hert (OHH), nd rind thikness (RT). Heterosis in reltion to the mid-prents (H mp ) nd to the stndrd ultivr (H p ) in three tetrploid lines, four diploid lines nd twelve wtermelon hyrids Tiffny (p) 3 TSS ( o Brix) Men Reltive heterosis (%) FC OHH RT TSS FC OHH (Sle 1 ) (Sle 2 ) (m) Hmp Hp Hmp Hp Hmp Hp Hmp LT (1) LT (2) LTCC-24 (3) Crimson Sweet (4) Pérol (5) New H. Midget (6) Chrleston Gry (7) 1x4 1x5 1x6 1x7 2x4 2x5 2x6 2x7 3x4 3x5 3x6 3x g d 7.3 g 10.7 d d d f 9.5 e 8.1 f 8.3 f d Sle of reords: 1 deep red; 2 light red; 3 pink; 4 white; 2 Sle of grdes: 1 no hollow hert disorder; 2 slight hollow hert (less thn 10% of the flesh); 3 - expressive hollow hert (over 10% of the flesh); 3 p = Stndrd ultivr (ommeril triploid ultivr) 4 Mens followed y the sme letter in the olumn did not differ y the Sott & Knott test t 5% proility RT Hp ACKNOWLEDGMENTS The Ntionl Counil for Sientifi nd Tehnologil Development (CNPq) supported the first uthor with grnt. We thnk the Emrp Semi-Árido nd the Bno do Nordeste for the support with funds nd filities. Efeitos heterótios em híridos triplóides de melni RESUMO - Este trlho estimou efeitos heterótios em rteres de plnt e fruto em melnis triplóides (Citrullus lntus). Doze híridos experimentis form vlidos e o hírido triplóide Tiffny foi utilizdo omo ultivr pdrão. O experimento, em loos sulizdos om três repetições, foi onduzido n Estção Experimentl d Emrp Semi-Árido, em Petrolin-PE. Avlirm-se os seguintes rteres: preoidde, prolifiidde, omprimento de rm prinipl, peso de fruto, teor de sólidos solúveis, espessur de s, or d polp e oorrêni de omento n polp. Verifirm-se diferençs signifitivs pr tods s rterístis vlids. Form enontrdos efeitos heterótios em relção à médi dos pis e em relção à ultivr pdrão, vrindo desde vlores negtivos té positivos em vários híridos, hegndo té 300% pr prolifiidde. As linhs tetrplóides devem ser melhords pr vários rteres fim de produzir híridos triplóides que sejm mis preoes, de plnts mis ompts e de frutos sem prolems de omento d polp. Plvrs-hve: Citrullus lntus, melni sem sementes, poliploidi. Crop Breeding nd Applied Biotehnology 5: ,

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