Hung Ta

PhD (2018)

Growth and development of lucerne with different fall dormancy ratings (PDF 9.8 MB)

Research Overview

The main aim of this research was to understand the physiological basis of differences in the growth and development of three lucerne (alfalfa; Medicago sativa) genotypes with different fall dormancy (FD) ratings; FD2 (dormant), FD5 (semi-dormant) and FD10 (winter-active). By the end of the seedling phase, the FD10 genotype had produced 20% more shoot and 16% more root biomass than the other two genotypes. After the seedling phase, a second treatment of defoliation frequency regime (DF) at 28 (DF28), 42 (DF42) and 84 (DF84) days was used to create different levels of root reserves, to examine whether treatments affected the yield and quality potential of crops. Annual shoot yields ranged from 4.4 t DM/ha in DF28 crops to 17.5 t DM/ha in DF84 crops. The root reserves of FD10 declined over time to 1.5 t DM/ha by the end of the experiment. It is likely that this progressive reduction in root reserves is the cause of reported decreases in persistence of FD10 genotypes over time. Phenological development (phyllochron, branching, canopy structure and leaf senescence) and reproductive development were conservative among FD ratings. In contrast, vegetative growth (leaf area expansion and stem elongation) was most closely correlated with fall dormancy ratings during autumn period. Hung was a NZ Aid Scholar supervised by Prof. Derrick Moot at Lincoln University. Dr Edmar Teixeira and Dr Hamish Brown of Plant & Food Research Ltd were associate supervisors.