Browsing by Author "Mthembu, Jabulani Bhekisisa"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Initiation of a pre-breeding effort for water stress resistance traits and yield improvement in wheat
    (Stellenbosch : Stellenbosch University, 2018-12) Mthembu, Jabulani Bhekisisa; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
    ENGLISH ABSTRACT: Wheat (Triticum aestivum L.) is an important crop produced in South Africa and across the world. Water stress and rust diseases (Puccinia spp.) are common factors hindering wheat growth and development. Leaf lifespan is reduced under water stress conditions from the leaf being infected by rust diseases. High-heritable Mendelianinherited and quantitative traits as well as male sterility mediated marker assisted selection (MS-MARS) technique was utilised for water stress and rust disease resistant wheat characterisation. The aim of the study was initiation of a pre-breeding effort for water stress resistance traits and yield improvement in wheat Sixty high-yielding genotypes and a female F1 1:1 male sterile and male fertile segregating population postulated to carry the leaf and stem rust resistance genes were screened for the presence of Lr34, Sr2, Sr31, Sr24, Lr37, Sr26 and Lr19 markers using a routinely standardised panel of markers used in the Stellenbosch University Plant Breeding Laboratory. Molecular characterisation of wheat lines was followed by cross-pollinations of a selected male sterile female and donor lines in the growth chamber using a reticulated hydroponic system (RHS) for the MS-MARS cycle scheme. Male fertile tillers were allowed to self-pollinate and were used for singleseed dehiscence. Sixty genotypes were phenotypically screened using identified and selected target traits associated with water stress resistance. Five genotypes were selected and further screened for water stress resistance using added traits of interest. An RHS was utilised for screening of the target traits including excised-leaf water loss, leaf relative water content, specific leaf area, number of tillers (NT), number of leaves and lengthrelated parameters such as root length (RL) and shoot length (SL). Fresh weight parameters included roots fresh weight (RFW), shoots fresh weight (SFW), leaves fresh weight (LFW) and total plant fresh weight (TPFW). Dry weight parameters included roots dry weight, shoots dry weight, leaves dry weight (LDW), above-ground dry weight and total plant dry weight (TPDW). Additional traits included chlorophyll content index (CCI), stomatal conductance, photosynthetic active radiation, leaf area index, radiation use efficiency, relative growth rate (RGR) and root-to-shoot ratio. Rust disease resistant genotypes were identified from the studied population. Molecular characterisation of the wheat genotypes for rust resistance genes showed increased allele frequencies in MS-MARS cycles 1 to 2 for both female and male lines, more specifically Lr34 and Sr2. However, the male lines showed lower allele frequencies and absence of the Lr19 marker in the population. Analysis of variance showed that water stress significantly influenced the growth and development of wheat genotypes for all the studied traits except RL and NT. The selected five genotypes showed better water stress resistance for all the traits studied. Genotypes were ranked as follows based on their performance under water stress conditions: 15HYLD-30, 15HYLD-22, 15HYLD-29, 15HYLD-18 and 15HYLD-26. A strong positive association observed under water stress conditions from fresh weight components included LFW and RFW (r = 0,884), followed by TPFW with FW components such as RFW (r = 0,848), SFW (r = 0,922) and LFW (r = 0,920). A strong positive association was also recorded for SFW and SL (r = 0,832), CCI with SL (r = 0,835) and SFW (0,890) and lastly, TPDW with RGR (r = 0,879) and LDW (r = 0,872). A strong positive association was recorded under well-watered conditions namely TPFW showed a strong positive association with SFW (r = 0,872), LFW (r = 0,920), TPDW with SL (r = 0,877) and LDW (r = 0,841).