HAND POLLINATION TESTS AND FIELD EVALUATION OF POLLINATORS FOR CITRUS

Transcription

1 BROWN AND KREZDORN: LLINATOR EVALUATION TET teel, R. G. D., and J. H. Torrie Principle and procedure of tatitic. McGrawHill Book Co., Inc., New York. 481 p. 1. Winton, J. R., H. R. ulton, and J. J. Bowman Commercial control of citru temend rot. U.. Dep. Agr Circ p. HAND LLINATION TET AND IELD EVALUATION O LLINATOR OR CITR H. D. Brown1 and A. H. Krezdorn Department of ruit Crop Univerity of lorida Gaineville Abtract tandard hand pollination technique were not alway adequate for determining the effec tivene of pollinator for commercial planting. A modified hand pollination technique coniting of applying counted number of pollen grain of variou varietie wa found ueful for comparing the potential capacity of the pollen variety to induce eed and fruit development. Currently, the only completely atifactory mean of eval uating pollinator i with actual field planting. rom a comprehenive urvey of commercial grove, everal varietie were found uitable a pollinator for '' tangelo and '' tangerine. Le data were obtained for '', '', 'Page' and '' varietie. Introduction In recent year there have been large in creae in planting of interpecific hybrid of grapefruit and tangerine. ome of thee varie tie are commercially claified a tangelo and ome a tangerine. Many of thee hybrid are exually elfincompatible and only weakly parthenocarpic. Therefore, they fruit erratically unle uitable pollinator are ued to induce fruiting through the timulu of eed production (2,, 12) or unle their parthenocarpy i trengthened through girdling (7) or pray application of gibberellic acid (4, 5). The ue of pollinator reult in the mot conitent fruit ing and the reulting eedy fruit are larger than lorida Agricultural Experiment tation Journal erie No t\ partial fulfillment of the requirement for the Mater of cience in Agriculture degree. the eedle parthenocarpically produced one (). Unfortunately, the elfincompatible varietie were releaed before their pollinator require ment were known (9, 10, 11). Thu, the grower ha been faced with the dilemma of electing pollinator with inufficient information. Extenive reearch with both hand pollina tion and field evaluation of pollinator for 'Or lando' tangelo ha been reported (4, ); however, much le information i available for electing pollinator for uch varietie a '', '', '', 'Page' and '; moreover, mot of the information on thee varietie i baed on tandard hand pollination technique or caging pollinator with bee (2). Krezdorn and Robin on () in lorida and Oppenheimer (8) in Irael reported tandard hand pollination tech nique to at time be inconitent with perform ance of pollinator in the field. Thu, ome of the current information i quetionable. The purpoe of thi work wa to more fully invetigate the reliability of hand pollination technique a the ole bai for electing pollina tor, to evaluate the effectivene of currently ued pollinator in commercial planting and to develop an in vivo method of comparing the effec tivene of variou pollen ource in cauing eed development and fruiting in elfincompatible varietie. Material and Method tandard hand pollination tet a a bai for electing pollinator. Pollen of everal varietie (Table 2) wa tranferred to the tigmatic ur face of pitil of '' and '' by bruhing them with frehly dehiced anther of the pollen variety. Thi procedure reult in the tranfer of hundred of grain of pollen to the elfincompatible flower. The hoot were carefully elected for good vigor and flower were the leafy bloom type,

2 44 LORIDA TATE HORTICULTURAL OCIETY, 199 thinned to 1 flower per hoot. lower were emaculated and depetaled jut prior to opening of the flower and anthei. Each pollen treatment wa applied to a total of 100 flower. A localized area on 1 ide of a tree contituted a tatitical block, with blocking deigned to eliminate variability of poition on the tree. Within thi block, each treatment wa applied to 5 flower. Thu, a randomized block experiment with 5 flower plot and 20 replica tion wa developed and tatitically analyzed. Effectivene of pollinator in commercial planting. Commercial grove of fruiting age tree of elfincompatible varietie were located throughout the citru area and the pollinating variety, if any, noted. Grower were quetioned a to whether any advere pet or environmental condition dratically influenced the bloom or early fruit development. Any grove with uch problem were eliminated. Emphai wa placed on the 2 mot important elfincompatible varie tie, * ' tangelo and '' tangerine, but everal other were alo invetigated. ruiting wa etimated by counting the fruit within a 2 x 2 foot frame placed at a height of feet and againt the foliage of the tree to be evaluated. ortyfive frame count were made per grove and the mean count per frame cal culated. rame were placed againt tree e lected at random, throughout the grove in which pollinator were abent. In grove with pollina tor, tree elected at random in row adjacent to pollinator were ued and the arithmetic mean or average number of fruit per frame wa calculated. Thirty fruit were randomly harveted from the tree ued and the eed counted. In ome planting there were o few fruit no ample were taken for eed count. Comparion of known quantitie and kind of pollen. Known quantitie of different varietie of pollen were placed on '' and '' flower repectively that had been thinned to 1 per hoot, depetaled and emaculated. Known quantitie of pollen were obtained from frehly opened anther of the deired variety with harpened diecting needle, a method ug geted by Alkamine and Giorlomi (1). Thi wa done with the aid of diecting microcope lo cated in the field adjacent to the experimental tree. Aitant tranported the pollen on the needle tip to the flower and carefully wiped it off onto the tigmatic urface of the pitil. Examination of the needle point indicated all the pollen wa tranferred. Two experiment were conducted with 'Or lando'. In one, 10, 25, 50, and 100 grain of '' pollen were tranferred to the tigmatic urface of '' flower and compared with flower to which the tandard maive amount of pollen had been tranferred by bruhing frehly opened anther of '' over the tigmatic urface of '' until the latter turned yellow. The experimental deign conited of 5 flower per plot replicated 10 time. Thu, each quantity of pollen wa applied to 50 flower. Analyi of variance and difference between mean were cal culated. A econd experiment with '', com pared 25 grain of '', '', '', 'Dancy' and '' varietie, with '' being conidered the tandard. Otherwie, the procedure were imilar. With '', experimental procedure were imilar except 10, 20, 40, and 80 grain and maive amount of '' and '' pollen repectively were compared and each treatment contained 5 flower. In all experiment the fruit were harveted and counted about 1 month prior to maturity. Reult and Dicuion tandard hand pollination tet a a bai for electing pollinator. It i clearly evident that '' and '' are elfincompatible and unfruitful in the abence of cropollination and that a wide range of pollen ource are equally effective in inducing eed formation and fruitfulne, Table 2. Thi i in agreement with previou work (2, 4,, 8, 12). There were no tatitical difference due to pollen ource, other than elfing. In aeing thi data, it i per tinent that the hoot were carefully elected and every effort made to develop preciion. The % fruit et wa high becaue of the careful elec tion of hoot and the removal of flower from the area adjacent to thoe pollinated. On the other hand, ome pollinator varietie were le effective in commercial planting where the honey bee wa the pollinating agent, Table. or example, '' wa almot completely ineffective a a polinator for both '' and '' even though hand pollination tet had indicated the revere. 'Pineapple' wa lightly better but certainly le than adequate. 'Paron

3 BROWN AND KREZDORN: LLINATOR EVALUATION TET 45 Table I. Plant material ued. Table. Evaluation of pollinator In commercial citru planting. Cultivar pecie or hybrid name Pollinator variety Variety pollinated weet orange Citru ineni nouinon rruii eed (14) i (9) 11 (D Paron Brown Pineapple C. ineni C. ineni C. ineni (11) 4 (25) 20 (2) 14 (1) () Grapefruit C^ paradii Macf. <1 (1) Tangerine and hybrid Dancy C^ reticulata Blanco Page () C. reticulata x (C. paradii x reticulata) (Clementine x OrTando) 4 Minneola C. paradii x C. reticulata ( x DTncyT ^ 1 2 (25) 24 Murcott C. reticulata x C. ineni (?) C. reticulata x (C. paradii x reticulata) (Clementine x OrTanao) C. paradii x C. reticulata ( x Bancy) Dane p 15,(2> 4 () 1 2 C^ reticulata x (C. paradii x reticulata) (Clementine x OrTando) Paron Brown 1 12 (1) 5 Page (C^ paradii x reticulata) x C. reticulata (Minneola x dementine) Pineapple 7 (2) 1 (10) 7 C. reticulata x (C. paradii x reticulata) (Clementine x OrTando) 14 (10) 2 Brown* and '' were likewie unatifac tory for ''. One planting of '1 with '' and one with 'Paron Brown' were fruiting well but the erratic reult with thee varietie a pollinator for '' () ugget the ame may be true with ''. Comparion of known quantitie and kind of pollen. It wa concluded from data in Table 5 that 50 grain of pollen wa approximately the Table 2.The influence of handapplied pollen1 on the yield and eed content of '' and '' fruit. Pollinator variety Pineapple Yield (% 0 b 81 a 77 a 80 a 81 a 82 a 79 a fruit matured)2 91 a 1 b 94 a 90 a 91 a 90 a 91 a 92 a No. 19 a 17 a 20 a 18 a 21 a 18 a eed per fruit 27 a 0 b 28 a 28 a 0 a 29 a 0 a 29 a In each column, mean followed by unlike letter are ignificantly different at the 0.01 level. Maive amount of pollen were applied by bruhing frehly dehiced anther over the tigmatic urface of pitil. 2Mean % of fruit reulting from 100 pollinated flower. Mean or average number of eed per fruit. 'The average number of fruit per 2 x 2 feet of fruiting area. ^Average eed content wa obtained from 0 fru.1t at each location. 1gure In bracket indicate the number of location evaluated. minimum needed to develop maximum fruiting under the condition of thi experiment; how ever, 25 grain wa alo fairly effective. The number of eed per fruit increaed with each increae in quantity of pollen and the dif ference in eed content between the 50 and 100 grain and aturation treatment were ignifi cantly different even though the number of fruit produced wa not. Thu, a "luxury" number of eed were produced. The data i inufficient to conclude 19 eed i the abolute number needed. Thi would probably vary with the phyiological condition of the hoot involved. Table contain the reult of application of 25 grain of pollen of each of 5 varietie to '' flower. '' wa much more effec tive on a per grain bai than the other in et ting fruit; however, the eed content did not differ a widely a had been expected. or ex ample, '' pollination reulted in only 4 le eed per fruit than thoe of '' but a large difference in number of fruit wa pro duced. However, from the data in Table 5 it i evident that mall difference in eed content are more influential at the lower end of the cale. The difference between the 10 and 25 grain treat

4 . 4 LORIDA TATE HORTICULTURAL OCIETY, 199 ment wa eed per fruit but a 1% increae in yield reulted. A difference of 4 eed per fruit between the 50 and 100 grain treatment exited with only a 4% increae in number of fruit. The poor howing of 'Dancy' and, to ome extent, '' wa urpriing ince 'Dancy' and '* have been effective in the field when their bloom period overlap the ''. The 'Dancy' and '' pollen came from 4 yearold tree and the other pollen from mature one but there i no evidence thi make a differ ence. However, thi experiment wa deigned only to etablih a principle and precie compari on of varietie will require more data. It wa concluded that the ame principle etablihed for '* hold for '', Table 7. '' wa much le effective than '' pollen on a per grain bai but the dif ference wa maked when maive amount of both were ued. The number of grain of '' needed for maximum yield wa about 40, which agreed cloely with the '' data. A in the cae of tandard pollination tet involving maive application of pollen, thee tet alone are not ufficient to delineate thoe varietie which are good pollinator. They do not take into account pecie or variety preference by the bee, the amount of pollen carried by bee, the number of viit bee make to citru flower and the amount of pollen produced by flower of given varietie, none of which have received ig nificant tudy in citru. However, thee tet are more accurate than tandard tet in determining the comparative ability of variou pollen varie tie to induce fruiting and eed formation. urther reearch with thi method can lead to a more thorough undertanding of the pollination problem in citru and ait in overcoming them. Evaluation of pollinator in commercial plant ing. Evaluation of pollinator in commercial planting i the only ure way of determining their effectivene. Moreover, a 1year evaluation of a grove or 2 will not uffice. The peculiaritie of the honey bee, the time of bloom of variou varietie, erratic or alternate blooming charac teritic and age of tree are all involved. Ober vation have been made of everal pollinator in '' planting for 11 year; however, little ha been reported on the reciprocal performance of the relatively new varietie ('', '', '', 'Page' and '') a commercial pol linator. Table contain the data obtained in a 1year urvey of pollinator in commercial grove. The data for ome of the varietie are very limited and recommendation are therefore tentative. The number of pollinator and their pacing varied tremendouly and thi greatly influenced the frame count value obtained. Thu, the quantative data were tempered with obervation made in careful inpection of the planting. The eed content i particularly coare and nearly alway kewed becaue highly parthenocarpic varietie produce ome eedle fruit even with pollinator, thereby reducing the average eed content. Thu, the eed number wa ued only to determine whether the pollinator wa cauing eedine. Tentative pollinator recommendation are given in Table 4 and dicued below. or 'Robino7i', '', '', '', and 'Page' atifactorily induced fruiting. '' caued uch heavy fruiting that evere limb breakage wa common. Thi may alo become a problem with '', for which only limited data were obtained. pacing the '' at wider in terval might prevent thi but no background of experience i available on which to modify the currently recommended plan. 'Page' appeared to atifactorily induce fruiting in '' but '' wa virtually valuele in thi repect, which agree with hand pollination tet (12). Table 4. Tentative pollinator recommendation1'2 for elfincompatible tangerine hybrid. Pollinator variety Page* Dancy Murcott KamiIn Pineapple A A(L) A A (L) A Variety A pollinated Page* ~ A Thee recommendation are judgment baed on hand pollination tet, frame count, repone of grower, and general evaluation of the tree and exit ing condition. No recommendation wa made unle at leat 1 field location wa evaluated. Hand pollination tet are available for ome varietie not included here; for thee, the reader i referred to reference (2, 12). 2The key to ymbol i:, completely unatifactory a a pollinator; A, atifactory a a pollinator; A, fair (would probably be A in a 5050 ratio); P0, poor (give ome help but probably not enough except in unuual itua tion);, erratic (A a a pollinator when bloom i ufficient and overlap the variety to be pollinated, but bloom i erratic); (L), the data 1 very limited and more will be needed before final concluion can be drawn;, no field planting were evaluated.

5 BROWN AND KREZDORN: LLINATOR EVALUATION TET 47 No '''' planting of fruiting age were located. '' in olid block were very unfruitful. The '' wa nearly alway ued a the pollinator in '''' planting o mot of the tree were ''. Thi wa very atifactory, but it eem unlikely the full fruit ing potential of '' would be reached with le than a 5050 mix of '' and 'Robin on'. In the 2 block located, '' wa effective a a pollinator for '' and limited data with 'Page' indicated it too would be atifactory. '' appeared to be ineffective a a pollinator for '', even where 2 row of each were alternated. In all cae, tree were fruiting for the firt time; however, ince the ame '' wa cauing fruiting of the '', tree age wa not limiting. '' continued to caue heavy fruiting of '', a previouly reported (). olid '' planting are well etablihed a unfruitful (, 4, ) and were o found in thi urvey. However, they do produce large, eedle crop on occaion, particularly on better oil, on ome roottock, and in certain year. The '' i not widely planted and in everal block there wa uch a mixture of varietie, the effectivene of each could not be orted out. In the 2 block located, '' erved well a a pollinator. 'Page' alo appeared atifactory. Neither olid planting of '' nor planting of thi variety with '' or '' were located. '' planting are few in number. Limited data indicate '' i not atifactory a a pollinator for '' and thi i ubtantiated by reported hand pollination tet (12). At 1 location, a mall planting of '', '' and Table 5. The influence of the number of grain of '' pollen on the yield and average eed content of '' tangeloj Table. The Influence of 25 grain of each of 5 pollen varietie on the yield and average eed content of ''. % fruit1'2 eed/fruit1, 42 a 10 rom 50 flower per variety. 2 b 2 Pollen ource Dancy 4 b 5 b 18 c Mean in thi line not followed by like letter are ignificantly different on the 0.05 level. No tatitical analyi wa made due to the very mall number of fruit in ome treatment. '' were mixed. No frame count were made but all varietie were fruiting well. ince '' i not atifactory, it follow that '' wa furnihing the proper pollen. In another cae, '', '' and '' were mixed and all fruited well. Thu, '' mut have induced the fruiting in ''. 'Page' reportedly i elfincompatible and highly parthenocarpic (2). Thi wa found true at 8 location. In fact, fruiting in olid block wa almot a heavy a where pollinator were preent. An exception wa 2 planting in which '' and 'Page' were alternated. The roottock of 'Page' were alo alternated, every other one being 'Carrizo' citrange or 'Cleopatra' man darin. The 'Page' on 'Cleopatra' were virtually fruitle and thoe on 'Carrizo' fruited heavily but had very few eed, le than per fruit. Thu, the fruiting wa due to roottock rather than to the pollinator. The data in Table are from the tree on 'Carrizo'. At a ingle location, '' appeared effective a a pollinator. '' planting with pollinator were in their firt year of fruiting. At location the '' appeared very effective in increaing fruiting. No other combination were available. Nine planting of '' without pollinator were No. pollen grain % fruit developed o. eed/fruit Table 7.The influence of the number of grain of '' and 'Hmlin' pollen on the yield and eed content of '' tangerine a 7.4 a No. pollen grain b 10.4 a Haoili n Tenple c 19.1 b at at 100 aturation 0.0 c 0.0 c 25.2 c 1.9 d, % fruit2 eed/fr (av.) uit2 0 a 0 a 11 b 4.8 a 29 c 5. a 8 e 1 c 49 d 21.2 e.8 a. a 74 e 9. b 77 e 12.5 c 8 e 2. d In each column, mean followed by unlike letter are ignifi cantly different at the 0.01 level. Each treatment applied to 50 flower. aturated conit of applying maive amount of pollen by bruhing frehly opened anther over the tigmatic urface. 2rom a total of 5 flower per treatment. Hean in thi line not followed by like letter are ignificantly different at the e,vel.

6 48 LORIDA TATE HORTICULTURAL OCIETY, 199 unfruitful, even though they were the oldet and larget tree found of thi variety. Multiple pollinator may be needed for '' and '' if it develop they will not ucce fully induce fruiting in the variety pollinating them. or example, a '''''' planting would reult in fruiting of all varie tie while '* with '' would reult in only '' fruiting. A of thi date, the limited data reported (2) indicate '' may be a poor pollinator for other elfincompatible varietie. '', which i elffruitful, might prove uc ceful for pollinating '' but it tenderne to cold i objectionable. Other varietie may be atifactory in certain combination but have fault that make their ue quetionable. 'Dancy' wa effective with 'Robin on' and '' but in many year it bloom little or none at all and it bloom period i often hort and late. 'Murcott' i often an effective pollinator for ome varietie but it bloom period i frequently later than varietie requiring cropollination. '' and other eedy grapefruit produce little bloom in certain year and the general ue of arenic on grapefruit alo poe a problem ince pray drift to the variety being pollinated would render it unmarketable. ome weet orange might be atifactory pollinator, a indicated from data in Table, but their per formance i erratic and their cultural require ment are ufficiently different to make manage ment a problem. LITATURE CITED 1. Alkamine, E. K. and G. Giorlomi Pollination and fruit et in the yellow paion fruit. Hawaii Agr. Expt. ta. Tech. Bull. 59: Hearn, C. J., J. C. Reece and R. enton elfincompatibility and the effect of different pollen ource upon fruit characteritic of four Citru hybrid. Proc. irt Int. Citru ymp., Univ. of Calif., Riveride. 1: Krezdorn, A. H The influence of eed and pollen ource on the ize of fruit. Proc. la. tate Hort. oc. 80: The ue of growth regulator to im prove fruit et in citru. Proc. irt Int. Citru ymp., Univ. of Calif., Riveride. Vol.. ubmitted for publication March and M. Cohen The influence of chemical fruit et pray on yield and quality of citru. Proc. la. tate Hort. oc. 75:0.. and. A Unfruitfulne in '' tangelo. Proc. la. tate Hort. oc. 74: and W. J. Wiltbank Annual girdling of '* tangelo over an eightyear period. Proc. la. tate Hort. oc. 81: Oppenheimer, H. R Experiment with unfruit ful 'Clementine' mandarin in Paletine. Agr. Re. ta., Rehovot, Irael. Bull. 48:1. 9. Reece, P. C. and. E. Gardner '', ', and '* new early maturing tangerine hybrid. Proc. la. tate Hort. oc. 72: ,. E. Gardner and C. J. Hearn. 19. 'Page' orange promiing variety. Proc. la. tate Hort. oc. 7: , C. J. Hearn and. E. Gardner '' tangelo an early ripening hybrid. Proc. la. tate Hort. oc. 77: and R. O. Regiter Influence of pollinator on fruit et in '' and '' tan gerine. Proc. la. tate Hort. oc. 74: RMANCE O CLOELY PACED TREE R. L. Phillip lorida Citru Experiment tation Lake Alfred Abtract Highdenity planting offer a way for citru grower to meet the challenge of riing cot of land, production, and harveting. Reult of an experiment initiated in 190 clearly indicate that earlier economic return may be realized from cloely paced tree. In the 1989 eaon, tree in a 10'xl5' pacing produced 19 boxe of 'Pineapple' orange per acre. Thi wa nearly twice the per acre yield of tree at a 15' x 20' lorida Agricultural Experiment tation Journal erie No. 89. pacing and almot time that of a 2O'x25' pacing. requent pruning wa required to maintain the vigorou tree in the cloet pacing within their allotted pace. Thi further timulated ex ceive vegetative growth at the expene of fruit producing wood. Water requirement have alo been higher for the cloer pacing. Introduction Citru grower are approaching an economic ituation where dratic change may be needed if grove are to be profitable in the future. In creaing land value and taxe, a decreaing availability of deirable citru land, riing cot of material and equipment, higher harveting cot, and an uncertain labor upply are cauing