| The objective of this research was to develop a 2,4-D ((2,4-dichlorophenoxy) acetic acid) tolerant red clover (Trifolium pratense L.) population, using two contrasting techniques. Recurrent half-sib family selection was used to develop increasingly more tolerant plant populations. At the cellular level, variant cell types were selected for growth in the presence of high levels of 2,4-D with the intention of regenerating 2,4-D tolerant individual plants.;Four cycles of recurrent selection increased levels of 2,4-D tolerance in red clover by approximately 35%. Family selections were based on means obtained through the use of a 1-5 visual rating scale. The narrow-sense heritability of the 2,4-D tolerance trait was high, averaging nearly 50% and inbreeding depression was kept to a minimum. These variables indicated that significant progress had been made and that future progress should be possible. Several more cycles of selection must be conducted to obtain 2,4-D tolerance levels high enough for use in a pasture situation. The agronomic potential of 2,4-D populations must also be investigated.;In vivo and in vitro responses to 2,4-D of eight red clover genotypes were shown to be correlated (r = 0.77). This provided justification for using in vitro systems to select for 2,4-D tolerance. Suspension cultures of a regenerative genotype were plated onto agar-based nutrient media supplemented with 40 mg L... |
