Initiation of a pre-breeding effort for water stress resistance traits and yield improvement in wheat

[摘要] ENGLISH ABSTRACT: Wheat (Triticum aestivum L.) is an important crop produced in South Africa and acrossthe world. Water stress and rust diseases (Puccinia spp.) are common factorshindering wheat growth and development. Leaf lifespan is reduced under water stressconditions from the leaf being infected by rust diseases. High-heritable Mendelianinheritedand quantitative traits as well as male sterility mediated marker assistedselection (MS-MARS) technique was utilised for water stress and rust diseaseresistant wheat characterisation. The aim of the study was initiation of a pre-breedingeffort for water stress resistance traits and yield improvement in wheatSixty high-yielding genotypes and a female F1 1:1 male sterile and male fertilesegregating population postulated to carry the leaf and stem rust resistance geneswere screened for the presence of Lr34, Sr2, Sr31, Sr24, Lr37, Sr26 and Lr19 markersusing a routinely standardised panel of markers used in the Stellenbosch UniversityPlant Breeding Laboratory. Molecular characterisation of wheat lines was followed bycross-pollinations of a selected male sterile female and donor lines in the growthchamber using a reticulated hydroponic system (RHS) for the MS-MARS cyclescheme. Male fertile tillers were allowed to self-pollinate and were used for singleseeddehiscence.Sixty genotypes were phenotypically screened using identified and selected targettraits associated with water stress resistance. Five genotypes were selected andfurther screened for water stress resistance using added traits of interest. An RHS wasutilised for screening of the target traits including excised-leaf water loss, leaf relativewater content, specific leaf area, number of tillers (NT), number of leaves and lengthrelatedparameters such as root length (RL) and shoot length (SL). Fresh weightparameters included roots fresh weight (RFW), shoots fresh weight (SFW), leavesfresh weight (LFW) and total plant fresh weight (TPFW). Dry weight parametersincluded roots dry weight, shoots dry weight, leaves dry weight (LDW), above-grounddry weight and total plant dry weight (TPDW). Additional traits included chlorophyllcontent index (CCI), stomatal conductance, photosynthetic active radiation, leaf areaindex, 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 showedincreased 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 allelefrequencies and absence of the Lr19 marker in the population. Analysis of varianceshowed that water stress significantly influenced the growth and development of wheatgenotypes for all the studied traits except RL and NT. The selected five genotypesshowed better water stress resistance for all the traits studied. Genotypes were rankedas 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 weightcomponents included LFW and RFW (r = 0,884), followed by TPFW with FWcomponents such as RFW (r = 0,848), SFW (r = 0,922) and LFW (r = 0,920). A strongpositive 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 conditionsnamely 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).

[发布机构] Stellenbosch University