Genetic variability and inheritance studies for low pH tolerance in tropical and sub-tropical maize germplasm

English: 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 s
Afrikaans: 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 geenak
Ministry of Agriculture