With the unpredictable environmental change, negative phenotypic plasticity in agriculture is one of the significant challenges to overcome by enhancing food security and productivity globally. Nutrient limitation is one of the significant abiotic stresses faced by plants which causes numerous alterations in plant morphology, physiology and reproductive growth and is poorly understood for crop improvement. This study aims to provide information on how nutrient limitation affects the growth and development of the model grass Brachypodium distachyon. In particular, the first part of the research focuses on the screening and selecting nutrients (NPKB) and their dose-response (20%, 4%, and 0%) in above and below-ground measurements showing a significant decrease under nitrate and phosphate limitation. More detailed analysis, including total monosaccharide and enzymatic sugar release, showed significant reduction after the nutrient limitation stress in both the accessions of Brachypodium. Furthermore, I explored 17 Brachypodium genotypes to assess the tolerant and susceptible parental combination in response to nutrient limitations. Iraqi and Turkish genotypes suggest potential parents with the available RIL populations for studying detailed analysis in future. Seven significant QTLs were found where the two major QTLs were located on chromosomes 3 and 1 under nutrient limitation colocalising with the VERNALIZATION1 and VERNALIZATION2 loci identified as flowering regulators in the domesticated cereal crops. The results further suggest that the potential genes identified in the study will decipher the molecular basis of nutrient tolerance in Brachypodium. The overexpression of pectin methylesterase inhibitor (PMEI-OE) showed a significant increase in gene expression compared to wild-type. PMEI_1 and PMEI_3 lines reduced significant pectin methylesterase activity suggesting the inhibitory effect of PMEI-OE. However, PMEI-OE lines significantly increased the saccharification efficiency in PMEI_1, PMEI_2, and PMEI_3 under Hoagland (control) whereas showing recalcitrance under nutrient treatment.
|Date of Award||2022|
|Supervisor||Maurice Bosch (Supervisor) & John Doonan (Supervisor)|
Understanding and exploring the phenotypic and genetic variation in a model system Brachypodium distachyon under abiotic stress
Bhardwaj, K. (Author). 2022
Student thesis: Doctoral Thesis › Doctor of Philosophy