Analyses of drought tolerance in durum wheat (Triticum turgidum var. durum) genotypes
| dc.contributor.advisor | Labuschagne, M. T. | |
| dc.contributor.advisor | Viljoen, C. D. | |
| dc.contributor.author | Fekybelu, Solomon Kebede | |
| dc.date.accessioned | 2017-10-24T05:58:06Z | |
| dc.date.available | 2017-10-24T05:58:06Z | |
| dc.date.issued | 2003-03 | |
| dc.description.abstract | English: In order to identify yield components associated with drought tolerance in durum wheat and evaluate the performace of Ethiopian durum wheat genotypes, 26 durum wheat genotypes, from different agro-ecologies of Ethiopia were evaluated under simulated moisture stress conditions. Stress caused dramatic reductions in grain yield and harvest index. Yield was significantly correlated primarily with number of kernels per spike and 100 kernel weight. Further decomposition of simple correlation coefficients into direct and indirect effects showed that number of kernels per spike and 100 kernel weight had the largest direct effects on grain yield, under both stressed and non-stressed conditions' The expression of drought tolerance in the F1generation obtained from all possible combinations among genotypes differing in their responses to moisture deficit stress was studied. Analysis of variance revealed significantly high variability among genotypes for yield, yield components and drought tolerance measurements due to the effects of treatments. Drought tolerance was expressed in the crosses involving tolerant parents. The diallel analysis showed that mean squares for both GCA and SCA were significantly high at both moisture regimes. GCA:SCA ratios indicated predominance of additive gene action for all characteristics positively correlated with grain yield under stress or negatively correlated with drought susceptibility index. Differences in water use and transpiration efficiencies and interrelationships among water use and transpiration efficiencies and associated traits were investigated among durum wheat genotypes with differing responses to moisture stress. Significantly high genotypic variability in the amount of cumulative water used before (ETba) and after (ETpa) anthesis was observed. Susceptible genotypes used higher amounts of water before anthesis and lower amounts after anthesis. In contrast, tolerant genotypes used a higher proportion of water during the post-anthesis period. Significantly high variability among the genotypes was observed for various measures of water use and transpiration efficiencies, total dry matter and harvest index. Ranking of cultivars for water use efficiency based on grain yield (WUEG) and transpiration efficiency based on grain yield, was consistent with ranking of cultivars for drought susceptibility indices. Drought susceptibility index was significantly but negatively correlated with harvest index, WUEG and grain yield. However, it was positively and significantly correlated with the ETba:ETpa ratio. A high positive correlation of WUEG with harvest index and grain yield with harvest index was found. Differences in flag leaf water potential were significant only for genotypes under stress treatments. Water potential declined with age under both treatment conditions, however, the fall was faster in stress sensitive types than in tolerant types in more advanced growth stages. Inheritance of water use and transpiration efficiencies was studied in a hybrid population obtained from six parents, selected for their different responses to moisture stress. GCA and SCA effects were significant at both the moisture levels. The interactions of GCA and SCA with moisture levels were also highly significant. Analysis of the genetic components of variation demonstrated that WU E and T were under the control of additive and dominance type of genes. Narrow sense heritability estimates for water use and transpiration efficiencies based on grain yield (WUEG) were higher at the moisture stress level. Measures of water use and transpiration efficiencies showed significantly high and positive genotypic and phenotypic correlations among them as well as with grain yield and harvest index. The impact of the effect of moisture stress on growth and phenological development was examined among durum wheat genotypes differing in their tolerance to moisture stress. Drought stress was found to delay major growth stages and shorten the grain filling period. Drought tolerant genotypes had fast early growth, whereas susceptible ones had slow RGR initially. Variation in RGR was associated with NAR and LAR. Differences in hybrid performance were due to significant GCA and SCA effects. Interactions of GCA and SCA with moisture level were also highly significant. Moderate to high levels of broad sense heritability estimates were found for most of the traits. Significantly high genetic and phenotypic correlations between NAR and RGR, and LAR and RGR were found. The genetic and phenotypic correlations of grain yield with total dry matter, harvest index, RGR and LAR were significant. The effect of moisture stress on the content of water soluble carbohydrate (sucrose and D-glucose) was investigated in durum wheat (Triticum turgidum L. var. durum) above ground organs to assess and characterise the responses of genotypes with differing responses to drought stress. In all organs examined, drought tolerant genotypes accumulated more glucose and sucrose, particularly, at an early age. Stress caused an overall increase in the level of these carbohydrates, but the levels were highest in the stems compared to other organs. Level of drought (drought susceptibility index, 'S') was strongly related with the level of carbohydrates in the various plant organs Genetic differences among genotypes with differing responses to drought stress and their progenies obtained from all possible cross combinations were assessed using AFLP markers. Moderate to high level polymorph isms were obtained with the primer combinations evaluated. Euclidean genetic distance estimates showed that there was considerable genetic diversity among the materials studied. The correlation coefficient for pair wise genetic distance estimates based on AFLP data and yield, yield components, and morphophysiological traits was significant and positive. Cluster analysis showed that grouping of genotypes on the basis of AFLP data and agro-morphological data fairly agreed. A number of AFLP fragments were significantly correlated with the various traits evaluated under stress conditions. AFLP fragments were observed to affect a number of traits that were strongly correlated with drought susceptibility index. | en_ZA |
| dc.description.abstract | Afrikaans: Om opbrengs komponente te bepaal wat geassosieër word met droogte toleransie in durum koring en om die prestasie van Etiopiese durum koring genotipes te bepaal, is 26 durum koring genotipes van verskillende agroekologiese gebiede van Etiopië geëvalueer onder gesimuleerde vog stremmings toestande. Stremming het dramatiese afnames in graan opbrengs en oes indeks veroorsaak. Opbrengs was betekenisvol gekorreleer hoofsaaklik met aantal korrels per aar en 100 korrel massa. Verdere ontleding van eenvoudige korrelasie koefissiënte in direkte en indirekte effekte het getoon dat korrels per aar en 100 korrel massa die grootste direkte effekte het op graan opbrengs onder beide stremmings en nie-stremmings toestande. Die uitdrukking van droogte toleransie in die F1 generasie verkry van alle moontlike kombinasies tussen genotipes wat verskil in hulle respons op vog stremming is bestudeer. Variansie analise het betekenisvolle variasie tussen genotipes vir opbrengs, opbrengs komponente en droogte toleransiemetings getoon a.g.v. die effek van die behandelings. Droogte toleransie is uitgedruk in die kruisings met tolerante ouers. Die dialleel analise het aangetoon dat gemiddelde kwadrate vir beide GCA en SCA betekenisvol hoog was by beide vog vlakke. GCA:SCA verhoudings het predominansie van additiewe geenaksie aangetoon vir alle eienskape positief gekorreleer met graan opbrengs onder stremming of negatief gekorreleer met droogte vatbaarheids indeks. Verskille in water verbruik en transpirasie effektiwiteit en inter verwantskappe tussen water verbruik en transpirasie effektiwiteit en geassosieerde eienskappe is ondersoek in durum genotypes met verskillende reaksies op vog stremming. Betekenisvolle genotipiese variasie in die hoeveelheid kumulatiewe water gebruik voor (Etba) en na (Etpa) antese is gesien. Vatbare genotipes het groter hoeveelhede water gebruik voor antese en kleiner hoeveelhede na antese. In kontras, het tolerante genotipes 'n hoër proporsie water gebruik in die post-antese tyd. Betekenisvolle hoë variasie tussen genotipes is gesien vir verskillende metings van water gebruik en transpirasie effektiwiteit, totale droë material en oes indeks. Rangordes van cultivars vir water verbruik effektiwiteit gebasseer op graan opbrengs (WUEG) en transpirasie effektiwiteit gebasseer op graan opbrengs was in orreenstemming met rangordes van cultivars vir droogte vatbaarheidsindekse. Droogte vatbaarheids indeks was betekenisvol maar negatief gekorreleer met oes indeks, WUEG en graan opbrengs. Dit was egter positief en betekenisvol gekorreleer met die Etba:Etpa verhouding. 'n Hoë positiewe korrelasie van WUEG met oes indeks en graan opbrengs met oes indeksis is gevind. Verskille in vlagblaar water potensiaal was betekenisvol slegs vir genotipes onder vog stremming. Water potensiaal het afgeneem met ouderdom by beide behandelings vlakke, maar die afname was vinniger in stremmings sensitiewe tipes as in tolerante genotipes in meer gevorderde groei stadia. Oorerflikheid van water verbruik en transpirasie effektiwiteit is bestudeer in 'n baster populasie verkry vanaf ses ouers, geselekteer vir verkskillende reaksies op vog stremming. GCA en SCA effekte was betekenisvol by beide vog vlakke. Die interaksie van GCA en SCA met vog vlakke was ook hoogs betekenisvol. Analise van genetiese komponente van variasie het getoon dat WUE en T onder beheer van additiewe en dominante gene was. Nou-sin oorerflikheids bepalings vir water verbruik en transpirasie effektiwiteit gebasseer op graan opbrengs (WUEG) was hoër by die vog stremmings vlak. Metings van water verbruik en transpirasie effektiwiteit het betekenisvolle hoë en positiewe genotipiese en fenotipiese korrelasies getoon tussen hulle en met graan opbrengs en oes indeks. Die impak van die effek van vog stremming op groei en fenologiese ontwikkeling is ondersoek in durum genotipes wat verskil t.o.v. toleransie vir vog stremming. Droogte stremming het die hoof groei fases vertraag en het die graanvul periode verkort. Droogte tolerante genotipes het vinnige vroeë groei, en vatbares het lae RGR getoon aanvanklik. Variasie in RGR is geassosieer met NAR en LAR. Verskille in baster prestasie was a.g.v. betekenisvolle GCA en SCA effekte. Interaksies van GCA en SCA met vog vlak was ook hoogs betekenisvol. Gemiddeld tot hoë vlakke van breë sin oorerflikheid is bereken vir meeste eienskappe. Betekenisvolle hoë genetiese en fenotipiese korrelasies tussen NAR en RGR, en LAR en RGR is gevind. Die genetiese en fenotipiese korrelasies van graan opbrengs met totale droë material, oes indeks, RGR en LAR was betekenisvol. Die effek van vogstremming op die inhoud van water oplosbare koolhidrate (sukrose en D-glukose) is ondersoek in durum koring (Triticum turgidum var durum L) bogrondse organe om die reaksie van genotipes te bepaal en te karakteriseer wat verskil t.o.v. hulle reaksie op vog stremming. In alle organe wat ondersoek is, het droogte tolerante genotipes meer glukose en sukrose geakkumuleer, veralop 'n vroeë groeistadium. Stremming het In algehele toename in die vlak van hierdie koolhidrate veroorsaak, maar die vlakke was die hoogste in die stamme in vergelyking met ander organe. Die vlakke van droogte (droogte vatbaarheids indeksiS') was sterk gekorreleer met die vlak van koolhidrate in die verskillende plant organe. Genetiese verskille tussen genotipes wat verskil t.o.v. hulle reaksie op vog stremming en die nageslagte wat verkry is van alle moontlike kruisings kombinasies is geëvalueer met AFLP merkers. Gemiddeld tot hoë vlakke van polimorfismes is gekry met die priemstuk kombinasies wat gebruik is. Euklidiese genetiese afstands bepalings het getoon dat daar groot hoeveelhede genetiese diversiteit is binne die getoetsde materiaal. Die korrelasie koeffisiënt vir paarsgewyse genetiese afstand bepalings gebasseer op AFLP data en opbrengs, opbrengs komponente en morfofisiologiese eienskappe was betekenisvol en positief. Tros analise het getoon dat groepering van genotipes op die basis van AFLP data en agro-morfologiese data redelik ooreenstem. 'n Aantal AFLP fragmente is gevind wat betekenisvol gekorreleer is met verskillende eienskappe wat geëvalueer is onder stremmings toestande. AFLP fragmente het In aantal eienskappe geaffekteer wat sterk gekorreleer is met droogte vatbaarheids indeks. | af |
| dc.identifier.uri | http://hdl.handle.net/11660/7335 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Durum wheat -- Drought tolerance | en_ZA |
| dc.subject | Durum wheat -- Genetics | en_ZA |
| dc.subject | Durum wheat -- Water requirements | en_ZA |
| dc.subject | Thesis (Ph.D. (Plant Sciences (Plant Breeding))--University of the Free State, 2003 | en_ZA |
| dc.title | Analyses of drought tolerance in durum wheat (Triticum turgidum var. durum) genotypes | en_ZA |
| dc.type | Thesis | en_ZA |