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dc.contributor.advisorLabuschagne, M. T.
dc.contributor.authorBijzet, Zelda
dc.date.accessioned2015-09-04T07:06:52Z
dc.date.available2015-09-04T07:06:52Z
dc.date.issued2014-06
dc.identifier.urihttp://hdl.handle.net/11660/1155
dc.description.abstractEnglish: Cultivars with high and stable genetic potential for production and quality is the main goal of a fruit-breeding programme and are assessed in multi-environment trials due to the influence of rootstocks as well as climate on yield and quality in citrus. In a crop where grafting is essential, the manifestation of the scion’s genotype is dependent on the rootstock on which it is grafted as well as the environment in which the scion-rootstock combination (stion) is grown. The problem with grafted trees is that part of what is measured in these trials is the rootstock’s reaction to the environment as well as the rootstock’s interaction with the scion and vice versa, which constitutes complex genotype x environment interactions (GEI). The aim of this study was to successfully separate the Genotype (G) and GEI of the stion into a scion and a rootstock G and GEI. Data used in this investigation emanated from Phase II trials within the South African citrus breeding programme and comprised of five citrus scion types namely grapefruit (Citrus paradise), midseason oranges (C. sinensis), Valencia oranges (C. sinensis) early mandarins (C. reticulate) and late mandarins (Citrus paradise). Rootstock selections that were included were: Van Stadens Rough lemon (C. jambhiri, Tenaka), Volckamer lemon (C. volkameriana V. Ten. & Pasq.), Empress Rosehaugh (C. reticulate Swingle) and Carrizo citrange (Poncirus trifoliate x C. sinensis). Three localities were included namely Messina, Malalane and Friedenheim for the univariate study. Data from Malalane over five years was used to test two multivariate models namely AMMI and GGE. The multivariate analysis confirmed citrus scion types as mega environments in relation to rootstocks. No single mega environment for rootstock selection, that was both discriminative and stable with regard to all the traits in this trial, could be found. Mega environments were trait specific with, for instance grapefruit, representing the ideal test environment for peel thickness and Valencia the most stable environment with regard to TSS:TA ratio. It was also found that the AMMI model was able to separate and quantify the contribution of the scion and rootstock to the stion in a single physical environment (i.e. same climate, same soil, same production practices). As was expected, the scion contribution was found to be more prominent than the rootstock contribution for most of the traits. There were exceptions such as in grapefruit, where the rootstocks were responsible for 53.21% of the yield effect as opposed to the 27.50% contribution of the scion and 54.96% with regard to peel thickness opposed to the 38.23% of the scion. GEI regarding scion (G) x rootstock (E) was significant but not for rootstock (G) x scion (E). This implies that the rootstocks in some or another way influenced the scions whereas the scions had no significant influence on the rootstocks. With a good insight into the biplot theory, the interpretation of the visual aspects of both the AMMI and GGE were found to be easy and beneficial. A dataset can generate a multitude of graphs which can render information at a quick glance but still with scientific context. The main consequence of applying multivariate models is the simplified and thus cost effective trial layout that it facilitates. There is no need any more for separate rootstock and scion trials. These trials can now be combined, incorporating selections from both the scions and rootstock programmes, saving orchard space and time but generating more information. The envisaged outcome of the study is a statistical method that in future trials would enable breeders to recommend the best rootstock-scion combination from time and cost effective evaluation of promising selections from the South African citrus breeding programme.en_ZA
dc.description.abstractAfrikaans: Sitrus cultivars met 'n hoë en stabiele genetiese potensiaal vir produksie en kwaliteit is die hoof doelwit van 'n vrugte teelprogram en moet op verskillende onderstamme asook verskillende klimaatsomgewing geëvalueer word en word multi-omgewings (MO) proewe genoem. In 'n gewas waar klonale voortplanting nodig is vir tipe-egtheid en siekte beskerming en voortplanting dus afhanklik is van ’n onderstam, moet die interaksie van die bostam met die onderstam in ag geneem word. Die probleem met geënte bome in MO proewe, is dat 'n deel van wat gemeet word, die onderstam se reaksie op die omgewing sowel as die onderstam se interaksie met die bostam - en omgekeerd met ander woorde ’n komplekse genotipe x omgewing interaksies (GEI) . Die doel van hierdie studie was om die genotipe (G) en GEI van die geënte plant (“stion”) suksesvol te skei in 'n bo-en 'n onderstam G en GEI . Data vir hierdie ondersoek is verkry uit Fase II proewe in die Suid- Afrikaanse sitrus teelprogram en bestaan uit vyf bostam groepe naamlik pomelo, midseisoen en Valencia lemoene asook vroeë en laat mandaryne. Onderstamme het ingesluit Van Stadens growweskil suurlemoen (C. jambhiri, Tenaka), Volckamer suurlemoen (C. volkameriana V. Ten. & Pasq.), Empress Rosehaugh (C. reticulate Swingle) en Carrizo citrange (Poncirus trifoliate x C. sinensis). Drie lokaliteite naamlik Messina, Malalane en Friedenheim het deel uitgemaak van die studie. Data van Malalane oor vyf jaar is gebruik om twee meerveranderlik variansieanalise modelle naamlik AMMI en GGE te toets. Die meerveranderlik variansieanalise bevestig sitrus groepe as mega-omgewings met betrekking tot onderstamme. ’n Enkel geskikte mega-omgewing vir onderstam seleksie, wat diskriminerend maar terselfdertyd stabiel was ten opsigte van al die eienskappe, kon nie gevind word nie. Mega-omgewings was spesifiek ten opsigte van eienskappe soos byvoorbeeld pomelo, wat as die ideale bostam groep geïdentifiseer is om skildikte te toets en Valencia as die mees stabiele omgewing met betrekking tot die verhouding van totale oplosbare stowwe tot titreerbare suurinhoud. Daar is ook bevind dat die AMMI model in staat was om in ‘n enkel lokaliteit onderskeid te tref ten opsigte van die bo- en onderstam bydrae tot die fenotipe van die geënte plant. Soos verwag het die bostam ’n meer prominente bydrae gelewer vir meeste van die eienskappe, as die onderstam. Daar was egter interessante uitsonderings soos byvoorbeeld vir pomelo, waar die onderstamme verantwoordelik was vir 53.21% van die produksie teenoor die 27.50% bostam en 54.96% met betrekking tot skildikte teenoor die 38.23% van die bostam. GEI was betekenisvol waar die onderstam as ’n omgewing vir die bostam beskou was maar was nie betekenisvol in die omgekeerde situasie nie. Dit beteken dat die onderstam in die geval die bostam beïnvloed het terwyl die bostam geen wesenlike invloed op die onderstam gehad het nie. Met 'n goeie insig in die teorie van biplots, was die interpretasie van die visuele aspekte van beide die AMMI en GGE modelle maklik en voordelig gewees. ’n Enkele datastel het 'n magdom grafieke gegenereer. Elkeen van die grafieke kon met slegs ’n oogopslag inligting beskikbaar stel, sonder om die wetenskaplike konteks te verloor. Die belangrikste gevolg van die toepassing van meerveranderlik variansieanalise modelle is die vereenvoudigde en dus koste-effektiewe proef uitleg wat dit fasiliteer. Afsonderlike bo- en onderproewe is nou onnodig. Hierdie proewe kan nou gekombineer word en instede van om onderstamseleksies net met ‘n enkele standaard bostam te ent, kan kombinasies van bo en onderstam seleksies saam met kontroles in een proef ingesluit word wat dus vinnig baie meer inligting beskikbaar stel. Die beoogde uitkoms van die studie is 'n statistiese metode wat in die toekoms sitrustelers in staat sal stel om op grond van tyd en koste-effektiewe proewe, aanbevelings rondom nuwe belowende seleksies uit die Suid-Afrikaanse sitrus bo- en onderstam teelprogram te maak. Die aanbevelings sal gebaseer wees op stabiliteit sowel as die beste bostam-onderstam kombinasies.af
dc.description.sponsorshipAgricultural Research Council’s Institute for Tropical and Sub Tropical Crops (ARCITSC)en_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectThesis (Ph.D. (Plant Sciences (Plant Breeding))--University of the Free State, 2014en_ZA
dc.subjectCitrus -- Breedingen_ZA
dc.subjectRootstocksen_ZA
dc.titleRootstock-scion genotype and environment interaction in a South African citrus breeding programmeen_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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