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University of KwaZulu-Natal (2018)

Pre-breeding of wheat (Triticum aestivum L.) for Biomass allocation and drought tolerance.

Mathew, Isack.

Titre : Pre-breeding of wheat (Triticum aestivum L.) for Biomass allocation and drought tolerance.

Auteur : Mathew, Isack.

Université de soutenance : University of KwaZulu-Natal

Grade : Doctor of Philosophy (PhD) in Plant Breeding 2018

Résumé partiel
Bread wheat (Triticum aestivum L., 2n=6x=42) is the third most important cereal crop globally after maize and rice. However, its production and productivity is affected by recurrent drought and declining soil fertility. Wheat cultivars with a well-balanced biomass allocation and improved root systems have better water- and nutrient-use efficiency and, hence, increased productivity under dry-land farming systems. The overall objective of this study was to develop breeding populations of wheat with enhanced drought tolerance and biomass allocation under water-limited conditions. The specific objectives of the study were : (i) to evaluate agronomic performance and quantify biomass production and allocation between roots and shoots in selected wheat genotypes in response to different soil water levels to select promising genotypes for breeding for drought tolerance and carbon (C) sequestration, (ii) to determine variance components and heritability of biomass allocation and grain yield related traits among 99 genotypes of bread wheat and triticale (Triticosecale Wittmack) to optimize biomass partitioning for drought tolerance, (iii) to deduce the population structure and genome-wide marker-trait association of yield and biomass allocation traits in wheat to facilitate marker-assisted selection for drought tolerance and C sequestration, and (iv) to estimate the combining ability of selected wheat genotypes and their progenies for agronomic traits, biomass allocation and yield under drought-stressed and non-stressed conditions for future breeding and genetic advancement for drought tolerance and C sequestration. To achieve these objectives, different experiments were conducted. In the first study, 99 wheat genotypes and one triticale accession were evaluated under drought-stressed and non-stressed conditions in the field and greenhouse using a 10×10 alpha lattice design with two replications. Data on the following phenotypic traits were collected : days to heading (DTH), number of productive tillers per plant (NPT), plant height (PH), days to maturity (DTM), spike length (SL), thousand kernel weight (TKW), root and shoot biomass (RB and SB), root to shoot ratio (RS) and grain yield (GY). There was significant (p<0.05) genotypic variation for grain yield and biomass production. The highest grain yield of 247.3 g m-2 was recorded in the genotype LM52 and the least was in genotype Sossognon with 30 g m-2. Shoot biomass ranged from 830g m-2 (genotype Arenza) to 437 g m-2 (LM57), whilst root biomass ranged between 140 g m-2 for LM15 and 603 g m-2 for triticale. Triticale also recorded the highest RS of 1.2, while the least was 0.30 for LM18. Water stress reduced total biomass production by 35% and RS by 14%. Genotypic variation existed for all measured traits useful for improving drought tolerance, while the calculated RS values can improve accuracy in estimating C sequestration potential of wheat.


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