Biasi, Bill

Chinchiolo, Steve : S. Chinchiolo is Production Manager, Philip Chinchiolo & Sons, Escalon, California

Grant, Joe : J. Grant is UC Farm Advisor, San Joaquin County

Mitcham, Beth : B. Mitcham is Extension Postharvest Pomologist, Department of Pomology, UC Davis

A Occasionallyair cavities develop within brown tissues of apples with internal browning . 4 Internal browning symptoms vary within lots . Cut surfaces of mildly affected fruit show patchy areas of tissue in or near the core . Moderatelyand severely affected fruit have large areas of browning . greatest in large fruit from late - harvested lots . Because IB has been Late harvest , high CO , linked to advanced fruit maturity and elevated carbon dioxide ( CO , ) levels storage increase internal during storage in pears and other apple varieties , handlers questioned whether fruit maturity and / or a fail - browning of Fuji apples ure to adequately monitor or control storage C02levels may have contrib - Joe Grant 0 Beth Mitcham P Bill Biasi u Steve Chinchiolo uted to the IB problem for Fuji apples . Here we report results of studies con - ducted from 1992through 1994 , which evaluate the roles of harvest timing cally conduct several sequential har - In a 3 - year study , internal browning and CO , levels during CA storage in vests over a 4 - to - 6 - week period to op - development of this disorder . of Fuji apples duringpostharvest timize eating quality and external red The extent and intensity of patchy storage varied from year to year , color development . Firm , sweet and areas of brown flesh discoloration as - but was stronglyaffectedeach year low in acid , Fuji apples may be suc - sociated with IB vary among apples by harvest timingand carbon diox - cessfully stored under controlled at - within a given lot . Fruit with low IB ide concentrationin storage atmo - mospheres ( CA ) at 32 ° F and 90 % to intensity typically have one to several spheres . Internal browning inci - 95 % relative humidity as long as 9 small , tan to light - brown areas of af - denceand severity werelow in fruit months after harvest . Many preharvest fected tissue , often first appearing near 180 days after harvested within and postharvest problems have been or in the core . These brown areas in - bloom . Timelyharvest and storage successfullyresolved as Fuji apple crease in size , may merge and often CO , levels below 0.5 % are rec - at acreage and production have in - become chocolatebrown in color as ommended to reduce losses from creased , while some remain as chal - symptoms become more severe . The this disorder . lenges . Internal browning ( IB ) , first ob - margin between affected and normal served in California during the winter tissue is smooth and distinct . In the In the 15years that Fuji apples have marketing of Fuji apples from the 1991 most severely affected apples , the en - been grown commerciallyin Califor - harvest , remains a challenge . tire flesh may turn brown , with the ex - nia , apple growers and packers have In January 1992 , packers observed ception of a thin layer of normal tissue quickly learned how to grow and mar - that some lots of Fuji apples showed just beneath the skin . ket this premium quality dessert moderate to severe IB upon removal Externally , IB - affected fruit appear apple . California Fuji growers typi - normal , making this defect virtually from CA storage . The disorder was CALIFORNIA AGRICULTURE , VOLUME 50 , NUMBER 3 26 Fruit with IB were rated as having impossible to eliminate during slight packing - housesorting operations . ( 1to lo % ) , moderate ( 11to 41 % ) The presence of even small amounts or severe ( 41 to 100 % ) symptoms ac - of cordingto the percentage of cut surfaces IB may result in the downgrading or rejection of entire lots of fruit by having brown discoloration . produce buyers . In 1993 , we harvested fruit on Sep - tember 13and 27 and October 11and Storage tests 25 ( 169,183,197 and 211 DAB ) from six preselected trees in the orchard . In For all 3 years of the test , we used contrast to 1992 , trees were left apples from a well - managed commer - unpicked for the duration of our har - cial Fuji apple orchard near Modesto vests , except for our own samples and with a history of IB . The orchard , a very light commercial color - picking planted in 1987 , was standard Fuji on on September 15 . At each harvest , we Mlll rootstock , planted lO - feet - by - 16 - picked 28 to 30 of the most visibly ma - feet . Soil was a deep , well - drained ture fruit , using ground color and red loamy sand with neutral to slightly al - skin color as criteria , from each of the kaline pH . The orchard was sprinkle - six trees . irrigated with well water . Gross yields When apples are harvested mul - were 18.4,35.4 and 15.3tons per acre tiple times to optimize color , size and in 1992,1993and 1994 , respectively . flavor , interior fruit In 1992 , we collected 160to 180fruit - generally the at random from bins during commer - least mature on the tree - is the last to On the surface , internal browning - affected cial harvests on September 21 , and Oc - be picked . Because packers had ob - fruit appear normal , makingthis defect virtually impossibleto eliminate during tober 1,12and 27 . These dates corre - served that late - harvested lots showed packing - housesorting . more IB , and these tend to consist of a sponded to 174,184,195and 210 days after bloom ( DAB ) . To determine har - large percentage of interior canopy vest maturity , we measured individual fruit , we hypothesized that fruit from row , we randomly collected 160 to 180 interior canopy locationsmight be fruit from bins containing apples from fruit firmness and tested for composite more prone to approximately 20 preselected trees IB than outer canopy soluble solids and titratable acidity us - during each fruit . Thus , we collected two samples of four commercial har - ing 25 fruit harvested on each date . vests in the orchard . Fruit on 20 trees Flesh firmness was measured using a of fruit on the last harvest date in 1993 : in the other row were not harvested one consisting of highly colored fruit UC FirmnessTester fitted with a except for 160to 180 fruit sampled from upper and outer canopy positions ? % inch apple tip . Two readings ( on randomly on each harvest date for and one from interior portions of trees . opposing cheeks with skin removed ) storage tests . Except for the first har - Individual fruit firmness and com - were made on each fruit . Solublesol - vest ( September 21 for the sample - posite soluble solids and acidity deter - ids and acidity measurements were harvested row and September 26 for minations were made on 25 fruit har - made on juice pressed from small lon - the commerciallyharvested row ) , we vested on each date , as in 1992 . We gitudinal wedges cut from each of sampled on the same dates for both also measured starch - to - sugar conver - 25 fruit . rows : October 6 and 21 , and Novem - sion of 25 apples using an iodine - Fruit from each harvest were stored ber 1 . These dates corresponded to 175 potassium iodide solution . This solu - in a 36 ° F cold room until October 30 , or 180 DAB for the first harvest , and tion turns starchy portions of the three days following the last harvest . 190,205and 216 DAB for subsequent apple cortex blue , allowing the disap - After sorting to remove blemished and harvests . Fruit harvest evaluations , pearance of starch to be monitored as defective fruit , fruit from each harvest storage conditions and poststorage apples mature . Ratings progress from were divided into four 30 - fruit sub - evaluations were the same in 1994 samples . These were stored at 32 ° F 0 ( immature , all of cortex and core as 1993 . and 95 % relative humidity in air starchy ) to 6 ( over - mature , starch gone from cortex and core ) . ( 0.03 % CO , ) or one of three controlled Harvest evaluations On each harvest date , blemished atmospheres with 2 % O2and 0.4 % None of the fruit evaluated at har - and defectivefruit were discarded , ( f0.1 ) , 1.5 % ( kO . 1 ) or 3.0 % ( f0.2 ) C02 vest in 1992 or 1993had internal and 30 - fruit subsamples were placed provided by a flow - through system . browning ( data not shown ) . In 1994 , into 32 ° F air or CA storage ( same 0 2 Fruit were evaluated for internal however , we observed slight symp - browning after four months storage and CO , concentrations as 1992 ) for toms of IB in a small percentage of four months , held for five days in air at and five days in ambient air at 68 ° F . fruit during evaluations at harvest . In 68 " F , then evaluated for IE3 as in 1992 . To evaluate IB , we sliced fruit in half , general , fruit firmness and acidity de - In 1994 , we repeated the sampling perpendicular to the stem end , and vi - clined as the harvest season pro - procedures of 1992 and 1993in adja - sually inspected the two cut surfaces gressed each year , while starch disap - for signs of browning in the fruit flesh . cent rows of the test orchard . In one CALIFORNIA AGRICULTURE , MAY - JUNE 1996 27 pearance scores and soluble solids we believe these data support a rela - The year - to - year variations in inter - concentrations increased ( table tionship between advanced fruit matu - 1 ) . nal browning at our test site were con - rity and greater susceptibility to IB in sistent with commercial packers â?? ob - Storage test results storage . servations of IB incidence during the In 1992 , after storage in the various In 1994 , IB incidence and severity 3 years of this study . In 1994 , many were greater than in the two previous atmospheres , there was little or no IB packers reported significant levels of years ( fig . lc ) . As in 1992 , IB incidence in fruit from all but the latest harvest IB in apples from orchards previously was low in early - harvested fruit stored ( fig . la ) . Air - stored fruit from this har - free of this disorder . Apparently , un - in air or low CO , CA , but increased vest had essentially no internal brown - known preharvest factors cause fruit markedly with harvest date ing , and IB increased with CO , con - ( P < 0.001 ) to be more prone to IB in some years centration in CA ( linear effect of CO , , and orchards than others . Orchard and CO , level in CA ( P < 0.001 for and / or environmental factors that each harvest individually and aver - P < 0.001 ) . Internal browning incidence was might predispose fruit to IB develop - aged over all harvests ) . Harvest method lower in 1993than 1992 ( figs . la and - sampled versus commercial ment are currently under study . lb ) . Internal browning was low to nil - did not significantly affect IB inci - Managing internal browning in fruit stored in air , 0.4 % , or dence , whether analyzed by indi - 1.5 % vidual storage atmosphere or over all CO , , but high in late - harvested fruit While small amounts of IB devel - atmospheres . These findings were held in 3 % CO , . There was a signifi - oped in early harvested Fuji apples surprising since we expected sample - cant linear increase in IB with increas - stored at high CO , levels , severe IB harvested trees to yield fruit of pro - ing CO , for each of the last two har - only developed in late - harvested vests ( P < 0.001 ) . IB was not signifi - gressively greater maturity and IB apples of high maturity . In the 3 years susceptibility than commercially of the study , fruit harvested earlier cantly different between fruit from harvested trees . than interior and exterior canopy positions . 180 DAB developed very little IB in We often observed small dry cavi - Apparently , interior canopy origin did storage , even at very high C02levels . ties , up to not contribute to the greater IB ob - Fuji apples must develop a mini - 0.5 inch in size , within served in late - harvested 1992 fruit , un - mum amount of external red color to brown areas of IB fruit in 1993and less the prior removal of exterior fruit be accepted in increasingly competi - 1994 , but not in 1992 . Air cavities form - typical in commercial harvests but tive domestic and export markets . Un - when dead tissue shrinks , and are der the warm temperature conditions symptomatic of C02injury in pears - somehow not our 1993sampling and other apple varieties . predisposed interior fruit to IB . Rather , that prevail prior to harvest in most 1992 1001 A 0 0.4 % CO , + 2.0 % 0 , 0 3.0 % CO , + 2.0 % 0 , 160 180 200 220 1993 Solid symbols = inner fruit Open symbols = outer fruit 60 420 1 160 180 200 220 1001 c 1994 Commercially haNeSted J : 20 0 160 175180 200 220 DAB Harvest date , Fig . 1 Internal browning varied greatly among years , storage atmospheres and harvest dates . 28 CALIFORNIA AGRICULTURE , VOLUME 50 , NUMBER 3 Fuji apple - producing districts of Cali - fornia , fruit usually reach ideal inter - nal maturity before developing suffi - cient red color for market acceptance . Growers waiting for the best possible red color risk delaying harvest beyond the time considered optimal for eating quality and storage life . Our findings show that this delay may also affect fruit susceptibilityto storage disorders . Internal browning is thought to be caused by the accumulation of injuri - ous levels of respiratory COzin fruit tissues . Factors that may contribute to high internal C02concentrations in - clude high fruit - respiration rates in - duced by high temperatures ; reduced rates of COzdiffusion through the cor - tex , skin , or wax coatings applied to apples ; and high COzin the atmosphere surrounding fruit during storage . A greater resistance to gas movement within more mature fruit may account for the increased incidence of injury to late - harvested fruit observed in our studies and in commercial practice . We currently do not know when IB appears during storage or if controlled atmosphere oxygen level or storage temperature affects IB development . Further research is needed in these ar - eas , and to identify indicators of fruit maturity that could be used to reliably Ceratocystiscankers enlarge slowly over several years , with the margins of active can - predict IB susceptibility . From results kers outlined by amber - colored gum balls . Infected limbsfrequentlydie , but the disease seldom destroys the tree . of our studies to date , we suggest the following guidelines for minimizing IB in Fuji apples : Almond pruning wounds , 1 . Begin and end harvest as early as possible . IB incidence and severity are low in fruit harvested before 180 days bark abrasions susceptible after bloom . 2 . Sample , cut and inspect fruit for to Ceratocystis IB during harvest , especially in or - chards with a history of this disorder . 3 . Use CA storage only for early - Beth L . Teviotdale 12 Dennis M . Harper harvested fruit free of IB at harvest . 4 . Keep C02levels in CA as far be - Ceratocystis canker , also known as In the past , pruning wounds were 0.5 % as possible . low a fungus mallet wound canker , is not regarded as potential infection 5 . Expedite handling and marketing disease of stone fruit trees most com - sites . However , in a 2 - year study , of late - harvested lots . monly found on almond and , occa - pruning cuts inoculated immedi - sionally , prune trees . Highly sus - 14 days ately or at intervals up to 1 . Grarzt is UC Farm Aduisor , Sail Jonqiriiz ceptible almond cultivars include to were found to be susceptible Couizty ; B . Mitchaiiz is Extetzsiotz ' Nonpareil ' and ' Ne Plus ' Mission , ' Ceratocystiscanker from Septem - B . Binsi is Postharvest Poinologist , and Ultra . ' The cankers are sunken , dark ber through February . Broken , Staff Research Associate , Departinetzt of and perennial . They enlarge slowly dead or living twigs became in - Pomology , UC Davis ; aiid S . Chinchiolo , over several years , with the margins of fected throughoutthe year when is Production Maizager , Philip Chiiichiolo active cankers outlined by amber - col - & Soizs , Escaloiz , California . inoculated with the fungus . ored gum balls . Infected limbs fre - CALIFORNIA AGRICULTURE , MAY - JUNE 1996 29