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dc.contributor.advisorLabuschagne, Maryke T.
dc.contributor.advisorTarekegne, Amsal
dc.contributor.advisorVan Biljon, Angeline
dc.contributor.authorKaonga, Kesbell Kaswela Eston
dc.date.accessioned2018-09-19T08:29:43Z
dc.date.available2018-09-19T08:29:43Z
dc.date.issued2015
dc.identifier.urihttp://hdl.handle.net/11660/9322
dc.description.abstractEnglish: In Malawi maize is grown even in marginal lands, on steep slopes, wet lands, rocky areas and low pH soils due to the high human population which excert pressure on the land. The objectives of this study were to investigate genetically diverse maize genotypes for tolerance to low pH soil conditions. In the hydroponic experiment genotypes IWDC3SYNF2-B, VPO52, and LPHpop 4 had relatively higher nett seminal root length and were considered tolerant, and DT-YSTR SYNTHETIC-B, TZE-WPOPDTC2STR-B, TZE-YDTSTRC4-B, LPHpop3, LPHpop13, and LPHpop14 were sensitive or susceptible to Al toxicity. Under field conditions, genotypes LPHpop16, LPHpop3, VPO739, VPO5173 and LOW N POOL C3-B were identified to be relatively tolerant to low pH soil conditions. SYNDTE–STY-W-B ranked first in terms of root tolerant index (RTi) with a good NSRL in the glasshouse hydroponic experiment and this was followed by VPO717 which also had a relatively a better root tolerance index and nett seminal root length. Phenotypic traits associated with grain yield, such as plant vigour, seed size (100 seed weight), shelling percentage, number of ears per plant, ear height and plant height can be used alongside grain yield when selecting germplasm for tolerance to low pH stress. In general, the effects of low pH soil conditions contributed to reduction in grain yields and yield components. The combined mean yield reduction due to low pH soil in this study was 69.9%. From AMMI and GGE analysis, genotypes LPHpop21, VPO52, VPO72, VPO744 and VPO96 were identified as the most stable. VPO097 was identified as an unstable genotype. Chitala low-land optimal site was identified as the most discriminating environment in terms of genotypes while Chitedze mid-altitude optimal environment was identified as a stable environment. The diallel study revealed that additive and non-additive gene actions were at play in the expression of some of the traits like grain yield, number ears per plant, shelling percentage, 100 seed weight and plant vigour, while non-additive gene action was predominant in the inheritance of characteristics such as anthesis-silking interval, plant and ear height, grain texture, stem and root lodging and gray leaf spot disease. Positive and highly significant GCA effects for grain yield were observed for inbred line CZL999601 across low pH and optimal conditions. While negative and significant GCA effects for grain yield were observed for inbred line CML161 across low pH and optimal conditions. SCA results indicated that single-cross hybrids CML999601/CML144, CML144/CML202, CML481/CML288 and CML161/CM172 were best for grain yield across low pH and optimal conditions. At a cut-off point of 1.0 with a cophenetic correlation of rcop = 0.87, the UPGMA clustered the inbred lines based on GCA for grain yield into two main clusters through use of Euclidean distance and standard deviation as type of scale. The pattern mostly followed the origin of the maize inbred lines such that six out of seven inbred lines from CIMMYT-Colombia (tropical) were grouped in the second cluster. The open pollinated inbred line varieties and specific combinations (single-crosses generated) identified in this study will be used in the National Maize Breeding Programme for development of genotypes tolerant to low pH and diseases for yield improvement and subsequent food security in the country.en_ZA
dc.description.abstractAfrikaans: In Malawi word mielies selfs in marginale grond, op steil hellings, vleilande, klipperige gebiede en in lae pH grond verbou, weens die hoë bevolking wat druk op die land plaas. Die doelwitte van hierdie studie was om geneties diverse mielie genotipes vir verdraagsaamheid vir lae pH grondtoestande te ondersoek. In die hidroponiese eksperiment het genotipes IWDC3SYNF2-B, VPO52 en LPHpop4 relatiewe hoër netto seminale wortel lengtes gehad en word as verdraagsaam beskou en DT-YSTR SYNTHETIC-B, TZEWPOPDTC2STR-B, TZE-YDTSTRC4-B, LPHpop 3, LPHpop13, en LPHpop14 was sensitief of vatbaar vir Al toksisiteit. Onder veldtoestande, is genotipes LPHpop16, LPHpop3, VPO739, VPO5173 en LOW N POOL C3-B as relatief verdraagsaam vir lae pH grondtoestande geïdentifiseer. In die glashuis hidroponiese eksperiment was SYNDTESTY-W-B eerste in terme van wortel tolerante indeks met 'n netto seminale wortel lengte van 2.5 cm en is gevolg deur VPO717 met ʼn wortel tolerante indeks van 1.0 en netto seminale wortel lengte van 1.7 cm. Fenotipiese eienskappe wat geassosieer word met graanopbrengs, soos groeikrag, saadgrootte (100 saad gewig), saad persentasie, die aantal koppe per plant, kop hoogte en plant hoogte kan gebruik word saam met graanopbrengs wanneer kiemplasma geselekteer word vir verdraagsaamheid vir lae pH stres. In die algemeen dra die effek van lae pH grondtoestande by tot die verlaging in graanopbrengste en opbrengs komponente. Die gekombineerde gemiddelde opbrengs verlaging as gevolg van lae pH grond in hierdie studie was 69.9%. Deur die AMMI en GGE analise is LPHpop21, VPO52, VPO72 is VPO744 en VPO96 geïdentifiseer as die mees stabiele genotipes. VPO097 is geïdentifiseer as 'n onstabiele genotipe. Chitala lae-ligging optimale omgewing is geïdentifiseer as die mees onstabiele omgewing in terme van genotipes terwyl Chitedze middel-ligging optimale omgewing geïdentifiseer is as 'n stabiele omgewing. Die dialleel studie het getoon dat beide additiewe en nie-additiewe geenaksie ʼn rol gespeel het by die uitdrukking van die eienskappe soos graanopbrengs, aantal koppe per plant, saad persentasie, 100 saad gewig en groeikrag, terwyl nie-additiewe geenaksie oorheersend was in die oorerwing van eienskappe soos antese-baard interval, plant en kop hoogte, graantekstuur, stam en wortel omval en blaarvlek siekte. Positiewe en hoogs betekenisvolle algemene kombineervermoë (GCA) vir graanopbrengs is in die lae pH en optimale omgewings, vir ingeteelde lyn CZL999601 waargeneem, terwyl negatief en betekenisvolle GCA effekte vir graanopbrengs waargeneem is vir ingeteelde lyn CML161 vir lae pH en optimale toestande. Resultate vir spesifieke kombineervermoë (SCA) het aangedui dat enkelkruisbasters CML99601/CML144, CML144/CML202, CML481/ CML288 en CML161/CM172 die beste graanopbrengs oor lae pH en optimale toestande gelewer het. By 'n afsny punt van 1.0 met 'n ko-fenetiese korrelasie van rcop = 0.87, het die UPGMA kluster, deur die gebruik van Euklidiese afstand en standaardafwyking as skaal tipe, die ingeteelde lyne gebaseer op GCA vir graanopbrengs in twee hoof groepe verdeel. Die groepering het die oorsprong van die ingeteeldelyne gevolg, sodanig dat ses uit sewe ingeteelde lyne van CIMMYT-Kolombië (tropiese) in die tweede kluster groepeer. Die OPVs, ingeteelde lyne en spesifieke kombinasie enkelkruisings wat geïdentifiseer is in hierdie studie sal gebruik word in die Nasionale Mielie Teelprogram vir die ontwikkeling van genotipes tolerant vir lae pH en siektes en om opbrengs te verbeter sodat voedselsekuriteit in die land verseker kan word.en_ZA
dc.description.sponsorshipMinistry of Agricultureen_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectLow pHen_ZA
dc.subjectHydroponicen_ZA
dc.subjectCophenetic correlationen_ZA
dc.subjectDiallel crossesen_ZA
dc.subjectPhenotypic traitsen_ZA
dc.subjectGCAen_ZA
dc.subjectSCAen_ZA
dc.subjectThesis (Ph.D. (Plant Sciences (Plant Breeding))--University of the Free State, 2015en_ZA
dc.titleGenetic variability and inheritance studies for low pH tolerance in tropical and sub-tropical maize germplasmen_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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