Factors influencing the success or failure of graft unions in grapevine.
| dc.contributor.advisor | Schmeisser, M. | en_ZA |
| dc.contributor.advisor | Deloire, Alan | en_ZA |
| dc.contributor.author | Bester, Andries Johannes | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture. | en_ZA |
| dc.date.accessioned | 2020-02-25T06:00:18Z | |
| dc.date.accessioned | 2020-04-28T15:11:07Z | |
| dc.date.available | 2020-02-25T06:00:18Z | |
| dc.date.available | 2020-04-28T15:11:07Z | |
| dc.date.issued | 2020-04 | |
| dc.description | Thesis (MScAgric)--Stellenbosch University, 2020. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: This study aimed to compare graft quality evaluation methods for their accuracy and efficiency to detect early incompatibility in grapevines in South African nurseries. The study also looked at the effect of current nursery practices on graft success, considering the noted increase in mortality rates of field planted vines in the South African viticulture industry. Paper 1: Two methods for the objective assessment of graft union quality, namely micro- computed tomography (microCT) and stereo microscopy with longitudinal sectioning, were compared, in terms of their accuracy, rapidity and ease of implementation. Longitudinal graft sections were also compared to hydraulic conductivity measurements. A close match of graft union quality ratings obtained from 2D microCT and stereo microscopy images was observed. MicroCT imaging of consecutive segments, taken at 1µm intervals through the entire graft union, rendered a more accurate 3D depiction of the total xylem connections, thereby providing a true representation of graft quality. Graft quality evaluations from a single plane longitudinal section are subject to over- or underestimations of vascular connectivity in comparison to a 3D model. This is confirmed by the lack of correlation between 2D graft quality measurements and hydraulic conductance. MicroCT is too expensive for large-scale screening of graft incompatibility, therefore 2D stereo microscopy is recommended. Should potential incompatibility symptoms be noted during 2D screening; a detailed 3D microCT study may be used to obtain conclusive evidence. Hydraulic conductivity is a relatively affordable method for detection of potential incompatibility, therefore the correlation between hydraulic conductivity and graft incompatibility should be investigated further. Paper 2 and 3: The effect of standard grapevine nursery practices on graft quality were studied two separate trials. The first trial (Paper 2) investigated the effect of different scion/rootstock combinations; different wax types; and the addition of 2,5-DCBA on the graft quality for the first 33 days after grafting by means of histology and stereo microscopy. Only the rootstock choice showed a clear impact on the development of graft unions. Grafting wax, irrespective of the types used, was shown to infuse the graft union, significantly disrupting graft formation. All treatments displayed a good bonding strength and histologically showed similar tissue development, except for Pinot Gris / Pinot Gris homografts, which demonstrated poor callusing and vascular tissue differentiation across the graft unions. Thus, inherent genetic propensity to form successful graft unions appears to be the most important factor for determining graft success in this study. The second trial (Paper 3) also investigated the effect of nursery practices (different wax types; the addition of 2,5-DCBA to wax, and callusing duration) on the graft quality for Pinot Gris grafted onto commercially important rootstocks. Grafts with the US 8-7 rootstock displayed greater success than Ruggeri 140, after one year of growth, suggesting rootstock choice to be the biggest consideration when grafting with Pinot Gris. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Hierdie studie het beoog om evalueringmetodes van entlasgehalte te vergelyk vir die akkuraatheid en doeltreffendheid daarvan om vroeë onverenigbaarheid in wingerde in Suid- Afrikaanse kwekerye op te spoor. Die studie het ook die invloed van bestaande kwekerypraktyke op die sukses van entlas ontwikkeling ondersoek, met die waargenome toename in wingerdstok-sterftes in die Suid-Afrikaanse wingerdbedryf inaggenome. Hoofstuk 1: Twee metodes vir die objektiewe assessering van entlasgehalte, naamlik mikro- rekenaar tomografie (microCT) en stereomikroskopie van ‘n lengtesnit, is vergelyk met betrekking tot hul akkuraatheid, snelheid en gemaklikheid van implementering. Stereomikroskopie is ook vergelyk met hidrouliese geleidingsvermoë metings. Daar is 'n noue ooreenstemming met entlas- kwaliteitsbeoordelings verkry vanaf 2D-mikroCT- en stereomikroskopieprente. MikroCT-prente van opeenvolgende segmente, geneem met tussenposes van 1 µm deur die hele entlas, het 'n meer akkurate 3D-voorstelling van die totale xileemvaatbindings gelewer en sodoende 'n egte voorstelling van die entlasgehalte gegee. Evaluering van entlasgehalte vanaf 'n lengtesnit deur ‘n enkele vlak is onderhewig aan oor- of onderskatting van totale bo- / onderstok vaatweefsel verbindings in vergelyking met 'n 3D-model. Dit word bevestig deur die gebrek aan korrelasie tussen metings van 2D-entlasgehalte en hidrouliese geleiding. MicroCT is te duur vir grootskaalse sifting vir ent- onverenigbaarheid; daarom word 2D stereo-mikroskopie aanbeveel. Sou potensiële onverenigbaarheidsimptome opgemerk word tydens 2D-sifting, kan 'n gedetailleerde 3D-mikroCT- studie geloods word om beslissende bewyse te verkry. Hidrouliese geleidingsvermoë is 'n betreklik bekostigbare metode om potensiële onverenigbaarheid op te spoor, daarom moet die verband tussen hidrouliese geleiding en entverenigbaarheid verder ondersoek word. Hoofstuk 2 en 3: Die invloed van standaard wingerdkwekery-praktyke op entlasgehalte is in twee afsonderlike proewe bestudeer. Die eerste proef (Hoostuk 2) het die effek van verskillende bo- / onderstok kombinasies; entwas-tipes; en die toevoeging van 2,5-DCBA tot entwas op enlasgehalte ondersoek. Entlas ontwikkeling was histologies en deur stereomikroskopie bestudeer vir die eerste 33 dae van af enting. Slegs die onderstok-keuse het 'n beduidende effek op die ontwikkeling van entlaste gehad. Die was, soos gebruik tydens enting (ongeag van entwas-tipe en byvoegmiddels) is bewys om gereeld die entlas binne te dring waar dit die entlas-ontwikkingsproses ontwrig. Al die behandelings het 'n goeie bo- / onderstok aanhegtingsterkte gehad en soortgelyke histologiese weefselontwikkeling getoon, met uitsondering van Pinot Gris / Pinot Gris self-ente, wat swak kallus- ontwikkeling en vaskulêre-weefsel differensiasie oor die entlas getoon het. Die inherente genetiese vermoë vir entsteggies om ‘n suksesvolle entlas te vorm, blyk om die belangrikste faktor te wees vir entlas ontwikkeling in hierdie studie. Die tweede proef (Hoofstuk 3) het ook die effek van wingerdkwekery-praktyke (verskillende soorte entwas; die toevoeging van 2,5-DCBA tot entwas en kalluskamer-tydsduur) ondersoek op die entlasgehalte van Pinot Gris / kommersieel-belangrike onderstokke. Entsteggies met die US 8-7-onderstok het ná 'n jaar van groei beter sukses behaal as Ruggeri 140, wat daarop dui dat die onderstokkeuse die grootste oorweging moet wees by die enting met Pinot Gris. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.format.extent | viii, 95 pages : illustrations (some color) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/108369 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Graft unions -- Quality | en_ZA |
| dc.subject | Grapevines -- South Africa | en_ZA |
| dc.subject | Nurseries (Horticulture) -- South Africa | en_ZA |
| dc.subject | Grapes -- Grafting | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Factors influencing the success or failure of graft unions in grapevine. | en_ZA |
| dc.type | Thesis | en_ZA |