- Title
- Investigations into tolerance of quality protein maize germplasm to low soil pH.
- Creator
- Mathiso, Ncebakazi
- Subject
- Proteins in human nutrition
- Subject
- Crops--Drought tolerance
- Date Issued
- 2020-06
- Date
- 2020-06
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10353/20804
- Identifier
- vital:46580
- Description
- Quality protein maize (QPM) has double the amount of two crucial amino acids (tryptophan and lysine) compared to normal maize. These amino acids make QPM very nutritious and strategically important to overcoming malnutrition in communities that use maize as a staple food. However, QPM production is affected by many abiotic stress factors such as drought, salinity and low soil pH. Screening for tolerance to low soil pH was conducted in this study due to limited focus on this stress in previous QPM breeding efforts. The main objective of this study was to determine the response of QPM germplasm to low soil pH. The specific objectives were to: (i) screen QPM germplasm for tolerance to low soil pH at seedling stage; (ii) determine the combining ability and type of gene action controlling various traits of QPM inbred lines under low soil pH at seedling stage (iii) select QPM hybrids that are high yielding under limed and unlimed conditions, as well as across environments. This study was conducted in South Africa, at the University of Fort Hare and at Dohne Agricultural Development Institute. Screening of 21 QPM inbred lines and two testers under glasshouse conditions was conducted using a randomised complete block design (RCBD) with three replicates. In this experiment, maize germplasm were screened for tolerance to low soil pH at the early seedling stage. The soil had a pH of 4, and it was sourced from Hogsback, in the Eastern Cape. The control was obtained by liming this soil so as to increase the pH to 5.5. Seedling traits such as chlorophyll content, stem diameter, plant height, root to shoot ratio, total biomass as well number of leaves were recorded in both experiments. JMP statistical software, version 14, was used for analysis of variance (ANOVA) and generating descriptive statistics on the traits that were measured. All measured traits showed highly significant variation (p<0,0001) except for number of leaves in the glasshouse experiment. Two indices, namely Dickson quality index and acidic soil adaptation index, revealed that tolerant inbred lines were QSW 20, IBL 7, IBL 1, IBL 14 and NC. The same 21 inbred lines were evaluated in the laboratory using the haematoxylin assay. A RCBD with three replicates was used to screen the inbred lines for tolerance to Al toxicity. The genotypes were exposed to a nutrient solution that had 440 uM of Al3+ at a pH of 4 while the control used a nutrient solution without Al toxicity at a pH of 5.8. Net root growth, relative root growth, total biomass and haematoxylin scoring were measured. All these parameters showed significant differences (p< 0,0001). The haematoxylin scoring and other measured traits were used to effectively assess the tolerance of inbred lines to Al toxicity. Inbred lines QSW 32, QSW 20, QSW 1, QSW 6 and IBL 1 were tolerant to Al toxicity. Combining ability of parental inbred lines and testers was evaluated for various traits under limed, unlimed as well as across (both limed and unlimed) environments in a glasshouse experiment. Line x tester hybrids and parental lines were evaluated in a RCBD with three replicates. The results showed that both additive and non-additive gene action influenced the expression of measured traits in all the environments. However, total dry weight was controlled by additive gene action in all the environments. There were no parents that showed good GCA for total dry weight under limed environments whereas inbred lines 17,15, 14, 1 and 20 had high GCA values for TDW under unlimed conditions. Moreover, across the environments, lines 21 and 14 showed good GCA for total dry weight. On the other hand, among the tescross hybrids evaluated under limed environment, seven hybrids had very high SCA values, while hybrids 10 x 20 and 6 x 20 showed best SCA for TDW under unlimed conditions. Under both limed and unlimed environments, hybrids with good SCA for TDW were 11 x 21 and 12 x 21. Forty testcross hybrids were assessed for yield potential under limed and unlimed conditions in the field using a RCBD with three replicates. The SAS version 9.2 was used for analysis of variance. Standard morphological traits measured showed significant differences under unlimed and limed conditions. Genotype OBT x IBL 2 had high grain yields, low yield reduction, a short anthesis-siking interval under low soil pH, and it was tolerant. On the other hand, genotypes NC, NC x IBL 6 and OBT x QSW 6 exhibited the best yield stability across across environments. These genotypes are recommended for further evaluation to ascertain their yield potential and stability of performance in multi-locational soil acidity hot spots.
- Description
- Thesis (MSc) (Crop Science) -- University of Fort Hare, 2021
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (156 pages)
- Format
- Publisher
- University
- Publisher
- Faculty of Science and Agriculture
- Language
- English
- Rights
- University of Fort Hare
- Rights
- All Rights Reserved
- Rights
- Open Access
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UFH Department of Agronomy
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | MATHISO revised Dissertation April 2021.pdf | 1 MB | Adobe Acrobat PDF | View Details Download |