Commercial utilization of pollinizing varieties of pears is important both for pear growers and processors in Oregon. A study was made to determine the suitability of Comice, Packam's Triumph and Anjou, the three pollinizing varieties of pears, for dehydration, as compared to the Bartlett variety which is commercially used for dehydration. These four varieties were dehydrated using conventional and dry-blanch-dry methods and were subsequently stored at 70°F. The storage period of Bartlett, Comice, Anjou, and Packam's Triumph was 275, 212, 186 and 175 days, respectively. Both fresh and dehydrated pears were analyzed for moisture, total acid, and total sugar. The over-all drying ratio and rehydration percentage of each dehydrated lot was determined. After storage, the dehydrated pears were evaluated for flavor, texture, color, over-all appearance, and over-all desirability by a panel of eight judges. The results indicated the following conclusions. (1) There was no significant difference in the over-all drying ratio of the unpeeled dried pears of all four varieties and treatments. (2) Peeled dried Packam's Triumph had the highest over-all drying ratio followed by Anjou, Comice, and Bartlett, respectively. (3) Bartlett had the highest rehydration percentage followed by Anjou, Comice, and Packam's Triumph, respectively. (4) There was no significant difference in the rehydration percentage of conventionally dried unpeeled and dry-blanch-dry unpeeled pears. But dry-blanch-dry peeled pears had a significantly higher rehydration percentage than the conventionally dried peeled pears. (5) The dehydrated Anjou pears had the lowest total sugar content of all four varieties. Packam's Triumph had a higher total sugar content than Anjou but lower than Comice and Bartlett. The total sugar content of the latter two varieties did not vary significantly. (6) The dehydrated Anjou pears had the highest total acid content of all the four varieties. Packam's Triumph had lower total acid content than Comice and Bartlett. The total acid content of the latter two varieties did not vary significantly. (7) The flavor, texture, and over-all appearance of all dehydrated lots did not vary significantly. The flavor and texture of all lots were liked by the panel, but the over-all appearance of these lots was disliked by the panel. (8) The color of peeled dried pears was rated higher than unpeeled dried pears by the panel regardless of variety and method of dehydration. The panel liked the color of dry-blanch-dry unpeeled and peeled pears more than corresponding conventionally dried unpeeled and peeled pears. The color of Comice and Anjou was rated higher than Bartlett and Packam's Triumph by the panel. The color of the latter two varieties was disliked by the panel. (9) The over-all desirability of all four varieties was rated higher than average by the panel. / Graduation date: 1965

Graduation date: 1964

Graduation date: 1980

Thesis (M.S.)--Washington State University, August 2008. / Includes bibliographical references (p. 66-74).

Thesis (Ph. D.)--Washington State University, May 2009. / Title from PDF title page (viewed on Apr. 20, 2010). "School of Economic Sciences." Includes bibliographical references.

Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Shrivelling and friction discolouration (FD), as postharvest disorders, negatively influence the marketability and potential shelf life of pears. By investigating the contributing factors in each of the disorders, the potential involvement of handling and storage variables were determined. This allowed for a better understanding of the responsible factors that create susceptible environments for these disorders to occur. From the moment that pears are harvested they lose weight by means of transpiration and, to a lesser extent, respiration. When excessive losses are experienced, the fruit will appear shrivelled and the marketability and shelf life are negatively influenced. By minimizing the rates of weight loss, the occurrence of shrivelling among pears during the postharvest handling can be lessened. The periods that proved to be most conducive to shrivelling (during a simulated postharvest handling duration) were where temperatures above 0 °C were experienced. These short periods proved more perilous for shrivelling than lengthy storage durations at low temperatures. This influenced the transpiration rate in such a way that the driving force accelerated the rate of weight loss in all the cultivars that were studied. Removing field heat from fresh produce and maintaining the cold chain reduces the driving force behind the transpiration of the pears. In all the cultivars studied, ‘Packham’s Triumph’, ‘Beurrè Bosc’ and ‘Forelle’, smaller and less mature fruit were more inclined to appear shrivelled. The surface area to volume ratio is fundamental in determining the rate of weight loss. This was most evident in ‘Beurrè Bosc’. Although no reproducible results could be obtained from the morphological studies, literature has attributed this phenomenon to the composition and quantity of the cuticle layer. Reduction of weight loss was obtained by sealing of the fruit stem. This obstructed water movement from the fruit through the xylem conducting tissue to the surrounding atmosphere. Not only did the stem appear greener and fresher, but less weight loss and subsequent shrivel was noticeable in the treated fruit. This effect was most evident in ‘Packham’s Triumph’ and ‘Beurrè Bosc’, but not in ‘Forelle’. ‘Forelle’ typically has a very short, thin stem in comparison to the other two cultivars.All the cultivars showed visual shrivel symptoms after 11 days at 18 °C. Rate of weight loss was the lowest in ‘Packham’s Triumph’, but due to its prominent dimensions, it appeared shrivelled before any of the other cultivars. ‘Beurrè Bosc’ lost weight at the highest rate (0.42%.day-1). As fruit injury, in the presence of oxygen, is inevitable, the oxidative enzymatic browning of pears will always be troublesome. This defensive mechanism partially prevents the infection of the fruit where epidermal cells are injured. To minimize FD, impact and frictional forces need to be lower during both harvesting and handling practices. A laboratory scale method was developed through which reproduceable treatments could be performed, thereby subjecting the fruit to industry related friction, rather than impact, injury. By assessing the discolouration in terms of both extent and intensity, the influence of variables could be determined on both ‘Packham’s Triumph’ and ‘Doyenne du Comice’ pears. As also found in practice, ‘Doyenne du Comice’ proved to be far more susceptible to FD than ‘Packham’s Triumph’, although the activity of the enzyme, polyphenol oxidase (PPO) was found to be higher in the latter. Although no significant difference was found between the FD encountered at fruit temperature of 3 °C and 15 °C, discolouration was greater at the higher temperature. This might be attributed to a greater degree of water loss, lower cell turgidity or higher enzyme activity. Thus, fruit taken from storage and sorted directly thereafter will exhibit less FD. The contribution of condensation forming on the fruit, acting as lubrication, cannot be ignored. Such fruit, with high turgor pressure, might again be more susceptible to bruising which will only be revealed well after the injury. Since enzymes, which include PPO, catalyse biochemical reactions, the availability of sufficient substrate most probably regulates the extent of this biochemical discolouration. Harvesting at optimum maturity and preventing any unnecessary friction will most definitely reduce the occurrence of FD. The ultimate challenge remains to optimize sorting and packing conditions without compromising on fruit quality. / AFRIKAANSE OPSOMMING: Verrimpeling en friksie verbruining (FV), as na-oes defekte, het ’n negatiewe invloed op die bemarkbaarheid en potensiële raklewe van pere. Hierdie studie het die bydraende faktore vir elkeen van die defekte ondersoek. Daar is gepoog om die effek van verskillende hanteringsen opbergingsmetodes op bogenoemde defekte te bepaal. ‘n Beter begrip is verkry van die oorsaaklike faktore wat bydra tot die ontstaan van die betrokke defekte. Direk na die oes van pere, begin die vrug gewig verloor as gevolg van veral transpirasie. Oormatige verliese sal lei tot ’n vrug wat verrimpeld voorkom, met ‘n negatiewe invloed op die bemarkbaarheid en raklewe daarvan. Die voorkoms van die verrimpeling van pere tydens die na-oes hantering van die vrugte, kan verminder word deur vermindering van die tempo van gewigsverlies. Die periodes waartydens die verrimpeling veral voorgekom het, (soos gevind in ’n gesimuleerde na-oes hanteringsmodel) was wanneer temperature bo 0 °C ondervind is. Sulke kort periodes was meer geneig om aanleiding te gee tot verrimpeling as die verlengde periodes van opberging by lae temperature. Sulke periodes van hoër temperature het gelei tot versnelde transpirasie en ’n versnelde tempo van gewigsverlies in al die kultivars wat ondersoek is. Die transpirasietempo van pere kan verlaag word deur die verwydering van veld-hitte en deur die streng behoud van die koue-ketting. In al die kultivars wat ondersoek is, ‘Packham’s Triumph’, ‘Beurrè Bosc’ en ‘Forelle’, is gevind dat die kleiner en minder volwasse vrugte meer geneig was tot verrimpeling. Die oppervlak area tot volume verhouding is krities in die bepaling van die tempo van gewigsverlies. Hierdie bevinding was die prominentste in ‘Beurrè Bosc’. Alhoewel geen beduidende resultate verkry kon word van die morfologiese studies nie, is daar verskeie verwysings in die literatuur wat hierdie verskynsel toeskryf aan die samestelling en hoeveelheid van die kutikula laag. Vermindering van gewigsverlies is verkry deur verseëling van die vrugtestingel. Hierdie tegniek het gelei tot ’n blokkering van die watervloei van die vrug na die omgewing deur die xileem weefsel. Verseëling van die stingel het dit groener en varser laat voorkom, en het ook ’n merkbare vermindering in gewigsverlies en die daaropvolgende verrimpeling tot gevolg gehad. Die effek van stingel-verseëling was die prominentste in ‘Packham’s Triumph’ en‘Beurrè Bosc’. Dit was minder duidelik in ‘Forelle’ wat tipies gekenmerk word deur ‘n baie korter, dun stingel in vergelyking met die ander twee kultivars. Al die kultivars het makroskopiese verrimpeling getoon na ‘n opbergingperiode van 11 dae by 18 °C. Die tempo van gewigsverlies was die laagste in ‘Packham’s Triumph’ alhoewel dit eerste verrimpeld voorgekom het. Dit kan toegeskryf word aan die spesifieke afmetings van hierdie betrokke kultivar. ‘Beurrè Bosc’ het vinnigste gewig verloor (0.42%.dag-1). Aangesien die besering van vrugte, in die aanwesigheid van suurstof, onvermydelik is, sal oksidatiewe, ensiematiese verbruining van pere altyd problematies wees. Hierdie verdedigingsmeganisme voorkom tot ’n mate die infeksie van die vrug wanneer epidermale selle beskadig word. FV kan beperk word deur die vrugte tydens oes en hanteringsprosedures so min as moontlik bloot te stel aan impak en friksie kragte. ’n Laboratorium-model is ontwikkel ter nabootsing van die omstandighede in die industrie. Die vrugte is aan friksie, eerder as impak, onderwerp, soos ondervind in die industrie. Die omvang asook die intensiteit van die verbruining is gemeet in beide ‘Packham’s Triumph’ en ‘Doyenne du Comice’ pere. Op hierdie wyse kon die invloed van die onderskeie veranderlikes in elke kultivar bepaal word. Alhoewel die ensiematiese aktiwiteit van die polifenol oksidase ensiem (PFO) die hoogste in ‘Packham’s Triumph’ was, is gevind dat ‘Doyenne du Comice’ veel meer geneig was tot FV as ‘Packham’s Triumph’. Hierdie bevinding bevestig die verskynsel soos in die praktyk gevind. Alhoewel geen betekenisvolle verskil gevind is tussen FV by vrug temperatuur van 3 °C en 15 °C nie, was daar meer verbruining by die hoër temperatuur. Hierdie verskynsel kan toegeskryf word aan ’n groter mate van waterverlies, laer sel turgiditeit en hoër ensiem aktiwiteit. Dus sal vrugte wat direk na opberging gesorteer word, minder FV toon. Die bydrae van die kondensasie wat op die vrug vorm, en as ’n smeermiddel dien, kan nie geïgnoreer word nie. Sulke vrugte met hoër turgiditeit, mag egter meer vatbaar wees vir kneusing, wat egter eers ’n geruime tyd na die kneusing tevoorverskyn mag kom. Aangesien ensieme, wat PFO insluit, as katalis dien in biochemiese reaksies, sal die beskikbaarheid van voldoende substraat, na alle waarskynlikheid die omvang van die biochemiese verkleuring reguleer.Die oes van pere tydens optimum volwassenheid, en die voorkoming van onnodige friksie sal definitief die voorkoms van FV verminder. Die uitdaging is steeds om sortering- en verpakkingstegnieke verder te verfyn sonder om ’n negatiewe invloed op vrugtekwaliteit te hê.

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Reproductive bud development is the first step of sexual reproduction of plants and is a major factor determining yield. For consistent yields in pears, knowledge of the development of the reproductive bud is required. The development of the reproductive bud with emphasis on the primordial bourse shoot was studied. The bourse shoot is important because of the ability of a bourse shoot to become reproductive, which can lead to bourse-overbourse bearing. The progression of reproductive bud development in 'Forelle' and 'Rosemarie' was studied from primordial bourse shoot initiation until dormancy the following season. The primordial bourse shoot was initiated in January 2003. The primordial bourse shoot progressed during dormancy with a plastochron length of 60 days in June. The rate of preformed leaf formation increased rapidly until August when the plastochron was 5 days. 'Rosemarie's' primordial bourse shoot development was more advanced at full bloom, which is a possible reason for the higher bourse-aver-bourse bearing habit of the cultivar. The number of leaves of the bourse shoot was more than with the 'Forelle', which has a low tendency for bourseover- bourse bearing. Flower initiation of the terminal bourse shoot bud was 56 and 77 d.a.f.b. for the 'Forelle' and 'Rosemarie', respectively. Initiation was well correlated with bourse shoot growth cessation. An increase in mitotic activity occurred during flower differentiation of the terminal bourse bud with a peak of floral appendage formation during December and January. From February until dormancy enlargement of the floral parts took place. The influence of severe dormant pruning and the quality of 2- year-old wood, on reproductive bud sink strength of 'Packham's Triumph' trees were investigated. The sink strength of primary growth increased by 40 % for short bearing units (SBU's) and 140 % for thick bearing units (BU's) as compared to long bearing units (LBU's) and thin BU's respectively. The increase in primary growth was due to better fruit set and larger fruit in the SBU's and the thick BU's. Since the increase in primary growth is less for SBU's compared to thick BU's the conclusion, which can be made, is that branch diameter influenced sink strength more than branch length. With increase in branch diameter the size of the xylem transport system increases more than that of the phloem. The increase in xylem transported metabolites, in particular root derived cytokinin seems to predominantly influence the magnitude of the sink strength. The influence of scoring and 6-benzyladenine (BA) application, during the flower induction phase on 'Doyenne du Cornice' and 'Rosemarie', were studied. Scoring caused a 50 % increase in fruit number of 'Doyenne du Cornice', which resulted in a 38 % increase in yield compared to the control. The increase in fruit number was due to higher percentage reproductive buds and improved bud quality. For the 'Rosemarie' scoring at the correct time resulted in a 40 % increase in reproductive buds. Scoring disrupts basipetal transport in the phloem, which results in the removal of apical dominance and an increase in root derived cytokinin's. More meristems can respond to inductive conditions and high quality reproductive buds develop. The combination of BA and scoring, lead to more flowers per inflorescence in 'Doyenne du Cornice'. / AFRIKAANSE OPSOMMING: Reproduktiewe knopontwikkeling by die peer Reproduktiewe knopontwikkeling is die eerste fase van reproduktiewe voortplanting in plante en is belangrik, want dit bepaal die oesgrootte. Vir konstante oeste in peerproduksie moet reproduktiewe knopontwikkeling verstaan word. Die ontwikkeling van die reproduktiewe knop, meer spesifiek die primordiale beursloot is bestudeer. Die beursloot is belangrik a.g.v. die beurs-oorbeurs drawyse. Die ontwikkeling van die reproduktiewe knop van 'Forelle' en 'Rosemarie' is gevolg. Die primordiale beursloot is Januarie 2003 geinisieër en ontwikkel tydens die boom se dormante fase met 'n plastochron van 60 dae gedurende Junie. Preformeerde blaarvormingstempo neem toe tot Augustus waar die plastochron 5 dae is. 'Rosemarie' se primordiale beursloot ontwikkeling was meer gevorderd teen volblom, met meer beurslootblare reeds teenwoordig. Dit is dalk die rede vir die hoër tendens van beurs-oor-beurs drag van die kultivar in vergelyking met 'Forelle'. Die terminale beurslootknop is 56 en 77 dae na volblom geïniseer vir 'Forelle' en 'Rosemarie' respektiewelik. Inisiasie was goed gekorreleerd met beeïndiging van beurslootgroei. Blomdifferensiasie het inisiasie gevolg met 'n toename in mitotiese aktiwiteit, blomaanhangsel vorming het 'n piek bereik III Desember en Januarie. Vanaf Februarie tot dormansie het ontwikkeling hoofsaaklik in vergroting van blomorgane plaasgevind. Die invloed van strawwe dormante snoei en die kwaliteit van 2-jaar-oue dra-eenhede op sinksterkte van reproduktiewe knoppe van 'Packham's Triumph' pere is ondersoek tydens die 2002/03 seisoen. Die sinksterkte van primêre groei het 40 % toegeneem vir kort dra-eenhede en 140 % vir dik dra-eenhede in vergelyking met lang dra-eenhede en dun dra-eenhede respektiewelik. Die toename in primêre groei vir kort en dik dra-eenhede kon toegeskryf word aan beter vrugset en groter vrugte. Omdat die toename in sinksterkte minder is vir kort dra-eenhede in vergelyking met dik dra-eenhede kan die afleiding gemaak word dat dra-eenheiddikte sinksterkte meer beïnvloed as dra-eenheidlengte. Met 'n toename in dra-eenheiddikte, neem xileemvaatweefsel meer toe as floeëmvaatweefsel. 'n Toename in xileem getranslokeerde metaboliete, meer spesifiek wortel vervaardigde sitokiniene beïnvloed die sinksterkte van die reproduktiewe knoppe. Die invloed van ringelering (ringsnit deur floeëm sonder bas verwydering) en 6-bensielaldenien (BA) toediening tydens reproduktiewe knopinduksie van 'Doyenne du Cornice' en 'Rosemarie' is ondersoek. Ringelering het 'n 50 % toename in vrugaantal veroorsaak wat die oes met 38 % laat toeneem het in vergelyking met die kontrole, vir 'Doyenne du Cornice'. Die toename in vrugte was a.g.v. 'n hoër persentasie reproduktiewe knoppe en toename in blomkwaliteit. By 'Rosemarie' het ringelering 'n 40 % toename in reproduktiewe knoppe bewerkstellig. Ringelering onderbreek die basipetale vervoer in die floeëm, verwyder dus apikale dominansie, met die gevolg dat daar 'n toename in wortel geproduseerde sitokiniene is. Meer meristeme reageer op induktiewe toestande en reproduktiewe knoppe van hoë kwaliteit vorm. Die kombinasie van ringelering en BA -toediening het meer blomme per reproduktiewe knop veroorsaak.

A survey of inspection records of Anjou and Bosc pears shipped to market between November 1, 1956 and March 30, 1957 show storage rots to be an important problem of the Rogue River valley pear industry. Considerably more rot occurred in the Bosc than in the Anjou pears. Tissue isolations from the common blue mold and gray mold rots consistently yielded Penicillium sp. and Botrytis sp. respectively. Isolations showed Cladosporium sp. to be almost always associated with a brown, superficial rot of Anjou and with a brown-black rot of Bosc pears. Packing-house tests of three concentrations of Stop-Mold B showed it to be an effective rot-preventative. An apparent improvement in the control of rots with increased concentration of Stop-Mold B solution occurred in one lot of pears. Another lot showed an apparent decrease in control of rots with increased concentration of this fungicide. Packing-house tests of fungicides for prevention of rots were conducted in 1958 and 1959. Of the nine fungicides tested, Busan 50 was the most effective for rot control but resulted in a severe, brown skin discoloration. The commonly used post-harvest-dip chemical, Stop-Mold B, ranked high in all of the tests and is considered to be the best of the fungicides tested. The high percentage of storage rot spots with a broken surface indicates the importance of handling fruit carefully to avoid injury. Penicillium was the most prevalent rot of the pears examined during these investigations. Next was Cladosporium rot, then Botrytis rot. Cladosporium rot is shown to be a major storage rot of winter pears in the Medford area and is not necessarily associated with skin breaks. / Land and Food Systems, Faculty of / Graduate

Polyphenolases (O-diphenol: O₂ oxidoreductase E.C. 1.10.3.1) have been isolated from a wide variety of plant and animal sources. This work deals with the isolation and characterization of polyphenolase from a previously unreported source, Pyrus communis, the common pear, horticultural variety D'Anjou. The chronometric method of assay was used, in which the enzymic oxidation of the substrate, usually catechol, is coupled to the oxidation of ascorbic acid and the time required to oxidize a specific amount of substrate is noted as the time required to colorize an external startch-iodide indicator. Various methods of isolation and purification were attempted. After a suitable isolation procedure was established, the enzyme was characterized by its substrate specificity, and its sensitivity to temperature, pH and inhibitors. Pear polyphenolase was characterized in particulate and soluble forms. The enzyme differs from other reported catechol oxidases in that it does not oxidize monophenols. A new spectrophotometric assay is described.

>Magister Scientiae - MSc / European pear (Pyrus communis L.) is the third most important fruit in South Africa after citrus and apple. The Agricultural Research Council (ARC) breeding programme seeks to obtain a fully red coloured pear. Sports (mutants) with red skin and reddish leaves of various cultivars occur and some have been used in breeding programmes, where they transmit red colour as a single gene. The red trait in ‘Max Red Bartlett’, a mutant of ‘Bartlett’ (Synonym – ‘Williams Bon Chretien’), was mapped in Italy to linkage group 4 (LG4). At ARC Infruitec-Nietvoorbij, Stellenbosch, South Africa, ‘Bon Rouge’ pear, another red mutant of ‘Williams Bon Chretien’, was crossed with ‘Packham’s Triumph’ generating an F1 population with a segregation of (54:71) red:green, approximating to a 1:1 ratio; indicating a simple Mendelian inheritance of the red trait. The aim of the study was to determine if the ‘Bon Rouge’ red colour trait maps to approximately the same position as the ‘Max Red Bartlett’ red colour trait on LG4, and if so, to identify SSR markers that are mapped closer to the red colour trait than were previously reported. The seven published pear and apple SSR markers mapped in the appropriate region of LG4 in pear and in apple maps were identified and screened in the parents and, where informative, were scored in 125 seedlings for co-segregation analysis. Single locus segregations were checked with JoinMap 4.1 and this program was also used to generate a genetic map for LG4 of the ‘Bon Rouge’ x ‘Packham’s Triumph’ progeny using the SSR markers and the red locus. Two linkage maps were constructed at a LOD threshold of 3 using the Kosambi mapping function, one each with the maximum likelihood and regression mapping algorithms. The genetic linkage map of LG4 of ‘Bon Rouge’ x ‘Packham’s Triumph’ consisted of seven SSR markers (2 from apple and 5 from pear). Markers CH01d03 and CH02c02b were mapped on the same position as the red trait in ‘Max Red Bartlett’ reported by Dondini et al. (2008) and four more markers were added. One of the newly mapped markers, NH011a has been found to be closely linked to the red trait, with an approximate distance of 4 cM. This marker can be used to indirectly select for the red gene in pear, for example to distinguish heterozygotes from homozygotes. This work sets the scene for further genetic studies on the red trait in pear breeding programmes.