In vitro induction of polyploidy in Tacca leontopetaloides

B.Sc. Samuel Agyei

Master's thesis

Abstract:

Tacca leontopetaloides is a tropical tuberous food crop which contains starch of a raw material source potential for industries. The aim of this study was to induce in vitro polyploidization in T. leontopetaloides using oryzalin as an antimicrotubule agent, to detect polyploids using flow cytometry and to assess polyploids in vitro and in field conditions of Ghana. Shoots were treated in vitro with oryzalin (25 μM and 30 μM) for 24 or 48 hours. The highest polyploidization efficiency of 10% was achieved with 25 μM oryzalin regardless of time duration and with 30 μM for 24 hours exposure time. In total, seven of 80 (8.75%) tetraploids were obtained from all treatments. The highest survival rate of shoots (90%) was achieved with 25 μM for 24 hours exposure time. Morphology of the tetraploid plants was evaluated on MS medium without plant growth regulators (PGRs). Tetraploid plants showed altered morphological characters such as increased leaf width/length ratio, rounder leaf shape and dark green colouration as well as significantly higher number of roots (4.85 ± 0.66 roots/explant) and root length (0.91 ± 0.10 cm) compared to diploids with lower number of roots (2.95 ± 0.52 roots/explant) and root length (0.62 ± 0.10 cm) respectively. No significant difference in plant height was found between tetraploid and the diploid plants. Cultivation of tetraploid and diploid plants on multiplication MS salts medium fortified with 0.05 mg l-1 NAA and 0.1 mg l-1 zeatin showed increased in the number of shoots (5.06 ± 0.19 shoots/explants) in diploids compared to tetraploid plants (4.43 ± 0.16 shoots/plant). Tetraploid and diploid plants were evaluated ex vitro under tropical conditions of Ghana. The survival rate after six weeks of acclimatization in the greenhouse was 100% and 91.6% for diploid and tetraploid respectively. After twelve weeks under field conditions, however, the survival rate was 60% and 80% for diploid and tetraploid respectively showing better adaptation of tetraploid plants to field conditions. Tetraploid plants produced a higher number of tubers per plants as well as increased in tuber size. The tetraploid plants showed slower growth compared to diploids. These results proved that in vitro treatment of T. leontopetaloides shoots with oryzalin solution is an effective procedure for chromosome doubling and tetraploid plants may be used as a material with modified morphology, growth and yield characteristics for further breeding and the generation of novel varieties of T. leontopetaloides.

Keywords

Flow cytometry, in vitro culture, oryzalin, ploidy level, Tacca leontopetaloides, morphological characteristics

Language used: English

Date on which the thesis was submitted / produced: 26. 4. 2018

Thesis defence

• Supervisor: Ing. Iva Viehmannová, Ph.D.

Czech University of Life Sciences Prague

Faculty of Tropical AgriSciences

Master programme / field:
Tropical Agriculture / Tropical Crop Management and Ecology