Leaf pruning intensities at flowering of banana did not influence fruit quality

ReviewLeaf pruning intensities at flowering of banana (Musa AAA,cv.Grande Naine)did not influencefruit green and yellow life and qualityMaricruz Ramı´rez a ,*,Marco Vinicio Sa ´enz a ,Alfonso Vargas b ,Mario Araya baLaboratorio de Tecnologı´a Poscosecha,Centro de Investigaciones Agrono ´micas,UCR,Apdo.2060,San Pedro de Montes de Oca,San Jose´,Costa Rica bDireccio ´n de Investigaciones,CORBANA S.A.,Apdo.390-7210,Gua ´piles,Costa Rica Received 16March 2007;received in revised form 13September 2007;accepted 15October 2007AbstractThis study examined the effects of leaf pruning intensities at flowering on the green and yellow life and fruit quality of bananas (Musa AAA,cv.Grande Naine).The fruit from banana plants that retained 7,9,11and 13leaves after pruning were packed in carton boxes of 13.7kg and stored in a cold room at 148C for 21days to simulate transportation conditions.During this period,eight visual evaluations of fruit peel colour were made.Next,fruits were induced to commercial ripening using ethylene at 100m l/ml.Four evaluations (every 2days)on fruit firmness,soluble solids,titratable acidity,fruit weight and peel colour were made to assess fruit yellow life.No interaction between evaluations and number of leaves retained was found for pulp firmness,soluble solid percentage,fruit acidity,fruit weight and maturation grade.The fruit green life and peel colour was similar for plants retaining different number of leaves.After the application of ethylene,there were no differences in fruit firmness (P >0.62),percentage of soluble solids (P >0.24)nor in the percentage of acidity (P >0.32).No difference in fruit weight (P >0.07)and ripening grade (P >0.17)were observed among plants retaining different number of leaves.The results suggest that in tropical commercial banana plantations,producing for international markets,it is possible to defoliate the banana plants to seven leaves at flowering without causing a reduction on the green and yellow life and quality of fruit.#2007Elsevier B.V .All rights reserved.Keywords:Defoliation;Leaf pruning;Post harvestContents 1.Introduction .................................................................................3192.Materials and methods ..........................................................................3203.Results .....................................................................................3214.Discussion ..................................................................................321References ..................................................................................3221.IntroductionThe fungus Mycosphaerella fijiensis attacks the banana leaves reducing rapidly the photosynthetically active area(Stover,1980).This reduces the vegetative growth and yield(Marı´n and Romero,1992),as well as fruit length (Hidalgo,2000)and quality,which results in premature ripening of fruit (Romero and Sutton,1997).However,Robinson et al.(1992)suggested that the physiological impact of foliage reduction on fruit ripening depends of how the defoliation is done,mechanically or by pathogens.It is known that the presence of the fungus in the banana leaves increases their senescence/locate/scihortiAvailable online at Scientia Horticulturae 115(2008)319–322*Corresponding author.Tel.:+5062073134;fax:+5062073038.E-mail address:maryrs16@cia.ucr.ac.cr (M.Ramı´rez).0304-4238/$–see front matter #2007Elsevier B.V .All rights reserved.doi:10.1016/j.scienta.2007.10.014and fruit ripening(Stover,1970,1974),a situation that does do not occurs when leaves are pruned(Robinson,1996).In tropical conditions with banana black Sigatoka(Myco-sphaerellafijiensis)infection,Bayona(1984)did notfind an effect of the number of functional leaves at harvest(3–10 leaves)on fruit green life during transport simulation(20days at148C).Similarly,Calvo and Bolan˜os(2001)in the Caribbean of Costa Rica did notfind a correlation between the number of leaves at harvest and fruit green life.In the subtropics with banana yellow Sigatoka infection,Robinson et al.(1992)also obtained no effect of the number of functional leaves at flowering(5–12leaves)on the fruit green life(measured until 50%of the fruits were soft at20–258C).According to Marı´n and Romero(1992),black Sigatoka is more severe and aggressive than yellow Sigatoka(Mycosphaerella musicola).Robinson and Anderson(1990)observed that there was no obvious reduction of fruit green life on fruit originating from severely pruned plants,retaining four orfive leaves.They also indicated that bunch mass increased to a maximum when eight or nine leaves were present without further increase with more leaves.Thus,the excess number of leaves normally present on a vigorous plant would appear to be surplus for normal bunch development.Fruit ripening in thefield was found on banana bunches from plants with less than four leaves at harvest (Ramsey et al.,1990).Fruit green life decreased with less than five leaves at harvest(Robinson et al.,1992;Bayona,1984)or when plants retained less than10leaves atflowering(Daniells et al.,1994).The difference in the number of leaves that affect fruit green life could be associated with the severity of the type of Sigatoka infection(M.fijiensis or M.musicola)and thefinal destination marked of the end product.Banana bunch development is slower in the subtropics compared to the tropics,where fruit is harvested prematurely.Fruit green and yellow life and quality after harvest of pruned plants have not been widely measured on tropical conditions.Therefore,the objective of this study was to determine the effect of leaf pruning intensities at flowering on the fruit green and yellow life and post harvest variables.2.Materials and methodsThe study was carried out during February to March2005in the Post Harvest Laboratory of the Agronomic Research Center of the University of Costa Rica.Bunches came from plots within a farm of163ha that is new to bananas,planted in year 2000.Plant density was of1550plants haÀ1cv.Grande Naine originated from in vitro propagated plants.Fertilization was done with455kg of N,56kg of P,510kg of K,60kg of Mg, 94kg of Ca,128kg of S,17kg of Zn and6kg of B haÀ1yearÀ1,split between26applications.Black Sigatoka caused by Mycosphaerellafijiensis was controlled by aerial spraying of systemic and protective fungicides.Fungicides were applied alternately in mixture with miscible oil or water according to the black Sigatoka infection level of the farm and weather conditions.Weekly removal of Sigatoka damaged leaf parts was performed as part of the normal control strategy.Four leaf pruning intensities were evaluated in randomly selected plants in the experimental area.Leaf removal was performed on plants within1–3days fromflowering. Treatments consisted of leaving the plants with7,9,11or all the leaves atflowering;the latter usually resulted in plants retaining13–14leaves.Each experimental plot consisted of 40–50plants with four treatments and six replications.Bunch bagging and trimming were carried out1–2weeks after flowering,respectively.Plastic bags of12.7m m thick,3.28% of perforated area with pinhole of4mm-d,impregnated with 1%of chlorpyriphos were used to cover the bunches.The covers were tied at the top of the bunch.In each bunch,three true hands plus the false hand and the male bud were eliminated.Fruit deflowering was conducted when fruits had begun to curl upwards.Harvesting took place90days after bunch bagging.From each experimental plot one bunch was selected.In each plant the number of leaves was registered.In each bunch,the diameter of the central fruit of the outer line at the second hand was measured.From each bunch two clusters formed byfive to seven fruits each,were taken from the middle of the2nd to6th hands.Clusters from each bunch were kept in a cleanflowing water tank for20min for delatexing.Thereafter,the10clusters of each bunch were placed in plastic traits and treated with the fungicide Lotos140SL(thiabendazole200g lÀ1+imazalil 200g lÀ1)at the doses of400mg lÀ1plus1%astringent Alum (99%aluminum and ammonium sulphate)sprayed over the crown to protect it.Finally,clusters from each bunch were packed in plastic Banavac bags within telescopic cardboard boxes of13.7kg using two lines offive clusters each.The same day,the six boxes for each treatment were transported to the Post Harvest Laboratory of the Agronomic Research Center of the University of Costa Rica.Boxes were distributed in a completely randomized design with six repetitions and stored in a cold room at148C for21 days,simulating the storage interval used for shipment of bananas to Europe.During this period,eight peel colour visual evaluations of the fruit were conducted.Then,boxes were moved to a chamber(208C)where ethylene at100m l mlÀ1was applied for24h through ARCO1ethylene generator,Model #100,Serial#5972(American Ripener Company Inc., Charlotte,North Carolina).Fruit evaluations(four)started3 days after the application of ethylene and continued every2 days until the peel colour of the fruits reached grade7of the V on Loesecke(1950)scale.In one fruit from each offive randomly selected clusters per box,pulp fruitfirmness(kg)was recorded in two positions of the fruit using a McCormick1 penetrometer with a convex compress of5/1600.The same fruit was used as a composite sample for determining the percentage of soluble solids(Atago1ATC-1,refractometer,AOAC method)and titratable pulp acidity(Orion940expandable ion analizer,S/N4045,Orion Research Incorporated, Laboratory Products Group,Boston,MA).The remainingfive clusters were weighed individually during the evaluations and ripening grades estimated following the V on Loesecke(1950) peel colour scale.Data were subjected to analysis of variance in PC-SAS(2002–2003).M.Ramı´rez et al./Scientia Horticulturae115(2008)319–322 3203.ResultsThe number of leaves at harvest of the plants from where bunches were taken differed(P=0.0373)with the different leaf pruning intensities(Table1).The fruit diameter(P=0.3580) did not differ among leaf pruning intensities.No interaction between evaluations and number of leaves retained was found for pulpfirmness(P>0.9786),solublesolid percentage(P>0.2740),fruit acidity(P>0.7674),fruit weight(P>0.9565)and maturation grade(P>0.0946).The fruit peel colour remained green(grade1,V on Loesecke scale) during the transport simulation period,independently of the leaf pruning intensities.After the ethylene application no differences in fruit pulpfirmness(P>0.62),soluble solid percentage(P>0.24)or fruit acidity(P>0.32)were observed (Table2).Also,no differences were observed between defoliation intensities in fruit weight(P>0.07)and maturation grade(P>0.17)during the evaluation time(Table3).4.DiscussionThe banana fruit used in this experiment came from a plantation with a severe black Sigatoka infection history for most of the year,due to the favorable climatic conditions for the growth of the fungus.Despite the leaf pruning intensities,all the plants reached harvest with six to seven leaves.This indicates that during theflowering-harvest interval there was a gradual loss of older leaves in those plants that retained the higher number of leaves atflowering.This resulted in greater loss of leaves in those treatments with low or no leaf removal. The lowest number of leaves at harvest found in this experiment (six to seven leaves)was higher than the number of leaves(five to four leaves)cited by Bayona(1984),Robinson et al.(1992) and Ramsey et al.(1990)as the minimum required to prevent fruit ripening during shipment.This could explain the lack of differences in green and yellow life found in this experiment among the different leaf removal intensities.However,because the experiment was not repeated over time,the effect of season on green and yellow fruit life and quality is an aspect requiring further investigation.The leaves pruned in the required treatments were the older leaves,which have lower leaf photosynthesis compared to young(apical)leaves(Eckstein and Robinson,1995;Segura et al.,2005b).In commercial banana plantations infected with black Sigatoka,no reduction on bunch weight was observed in plants retaining seven(Vargas et al.,2005)and nine(Vargas et al.,2006)leaves atflowering through leaf pruning.The same authors suggested a reduction in black Sigatoka inoculum with a significant increase in the ratooning(number of bunches per production unit per year).Table1Diameter of middle fruit of the outer whorl of the second basal hand and number of leaves at harvest of bananas(Musa AAA cv.Grande Naine)with different levels of leaf pruning atfloweringLeaves retained atflowering Fruit diameter(mm)Leaves atharvest732.8Æ0.4 6.0Æ0.0 931.8Æ1.17.3Æ0.6 1133.1Æ0.5 6.3Æ1.1 1332.5Æ0.97.2Æ0.8 Probability0.35800.0373Each value is the mean of six repetitionsÆstandard error.Table2Fruit pulpfirmness,percentage of soluble solids and titratable acidity during time from bunches of banana(Musa AAA cv.Grande Naine)with different levels of leaf pruning atfloweringLeaves retained atflowering Days after ethylene application3579Fruit pulpfirmness(kg)7 2.2 1.0 1.1 1.09 2.2 1.1 1.2 1.011 2.5 1.1 1.0 1.013 2.3 1.1 1.1 1.0 Standard errorÆ0.3Æ0.04Æ0.05Æ0.02 Probability0.89630.62590.64170.8243Percentage of soluble solids(%brix)78.017.121.220.2 97.618.421.220.2 117.017.422.020.4 137.517.620.620.4 Standard errorÆ0.5Æ0.6Æ0.5Æ0.3 Probability0.52040.54630.23900.9375Percentage of titratable acidity(%malic acid)70.3250.4600.3580.285 90.3120.4120.3560.317 110.3260.4210.3960.287 130.3390.3930.3740.292 Standard errorÆ0.025Æ0.025Æ0.030Æ0.016 Probability0.89680.32030.96740.5084Each value is the mean of six repetitions.Table3Cluster weight and fruit ripening during time from bunches of banana(Musa AAA cv.Grande Naine)with different levels of leaf pruning atflowering Leaves retained atflowering Days after ethylene application3579Cluster weight(g)71060104910411035 9978969963957 111007998991985 131055104510381032 Standard errorÆ25Æ25Æ25Æ25 Probability0.07460.07740.08070.0822Fruit ripening(V on Loesecke scale)7 2.2 3.8 4.6 6.79 2.2 3.6 4.47.011 2.3 3.5 4.77.013 2.6 3.7 4.37.0 Standard errorÆ0.14Æ0.17Æ0.18Æ0.15 Probability0.17560.60690.39960.4262 Each value is the mean of six repetitions.M.Ramı´rez et al./Scientia Horticulturae115(2008)319–322321Studies on dry matter production and distribution in subtropical(Robinson,1996;Eckstein et al.,1995)and tropical (Segura et al.,2005b)climatic conditions indicated that afterflowering dry matter allocation to leaves declined,while in the pseudostem and corm it peaked atflower initiation and de-creased subsequently until harvest.Therefore,bunch develop-ment is an expense of dry matter allocation,not only to the leaves but also from all other parts of the plant(Eckstein et al., 1995).Similarly,Segura et al.(2005a)found in tropical conditions that afterflowering,the pseudostem acts as an important reservoir for bunch and follower sucker develop-ment.The similar number of leaves at harvest among treatments,plus the nutrition supplied from the corm and pseudostem may also have contributed to bunch development, resulting in similar fruit pulpfirmness,soluble solids and acidity among the different leaf removal treatments.Similarly, Rodrı´guez et al.(2006)found that different leaf pruning intensities atflowering of bananas(Musa AAA)did not result in differences in total sugars and starch of bananas.Robinson et al. (1992)did not recommended the defoliation of bananas in subtropical conditions in the absence of black Sigatoka,mainly because it caused yield reduction.However,Daniells et al. (1994)also in subtropical conditions,in absence of black Sigatoka,supported the practice of leaf pruning,indicating a greater control of pests that attack the foliage.The experiment described here was performed with fruit from plants exposed to high black Sigatoka infection,in humid tropical conditions and supports the defoliation practice at flowering,which resulted in no changes in the green and yellow life and fruit quality of bananas.Vargas et al.(2005,2006), Saborı´o and Granados(2005)and Segura and Valle(2005) reported that leaf pruning atflowering did not reduce bunch weight and fruit dimensions.From these results it is suggested that leaf pruning might be worthwhile under tropical conditions.ReferencesBayona,R.,1984.Vida verde de fruta cosechada en focos de Sigatoka Negra.Augura10(2),49–52.Calvo,C.,Bolan˜os,E.,paracio´n de tres me´todos de deshoja en banano(Musa AAA):Su efecto sobre el combate de la Sigatoca Negra (Mycosphaerellafijiensis,Morelet)y sobre la calidad de la fruta.COR-BANA27(54),01–12.Daniells,J.,Liste,A.,Bryde,N.,1994.Effect of bunch trimming and leaf removal atflowering on maturity bronzing,yield,and other aspects of fruit quality of bananas in North Queensland.Australian Journal of Experimental Agriculture34(2),259–265.Eckstein,K.,Robinson,J.C.,1995.Physiological responses of banana(Musa AAA;Cavendish sub-group)in the subtropics.I.Influence of internal plant factors on gas exchange of banana leaves.Journal of Horticultural Science 70(1),147–156.Eckstein,K.,Robinson,J.C.,Davie,S.J.,1995.Physiological responses of banana(Musa AAA;Cavendish sub-group)in the subtropics.III.Gas exchange,growth analysis and source-sink interaction over a complete crop cycle.Journal of Horticultural Science70(1),169–180.Hidalgo,M.,2000.In:Efecto de la reduccio´n del a´rea foliar por medios bio´ticos o abio´ticos sobre la fotosı´ntesis foliar del banano(Musa AAA cv.Valery) Tesis Ing.Agr,Universidad de Costa Rica,San Jose´,Costa Rica,p.58. 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