Abstract:
The primary objective of this research was to increase genetic diversity in mangosteen through mutation breeding. In 8 trials, 724 mangosteen seeds were treated with 8 concentrations of ethyl methane sulfonate (EMS) and 272 seeds were treated with 4 different concentrations of colchicine. The LD50 for 16 hours exposure time in aqueous solution of EMS was 0.42%. Treated seeds were incubated in vitro and surviving seedlings that sprouted were acclimatized and grown in pots filled with planting mixture under shade. Data were recorded on plant height and length and width of the largest leaf every 3 months for up to 33 months. Morphological abnormalities observed included irregularly shaped leaves, asymmetrical leaves, new branches arising from the base of stem or near the top, multiple branches from one part of the stem rather than pairs, asymmetrical branching, curved stem, and recumbent growth habit. Some of the abnormalities were transient and did not persist as the plants grew new sets of leaves or branches. The maximum percentage of leaf abnormalities recorded was 50% in the EMS 0.75% group, followed by 31% in the EMS 0.5% group, 21% in the EMS 0.1% group, and 12% in the EMS 0.25% group, compared to 20% in the control. The maximum percentage of unusual branching patterns recorded was 50% in the EMS 0.5% group, followed by 24% in the EMS 0.1% group, and 19% in the EMS 0.25% group, compared to 20% in the control. The occurrence of recumbent habit was 9% in both the EMS 0.1% and 0.25% groups, compared to 8% in the control. In many cases these abnormalities may not have been mutations but may have been caused by environmental conditions such as insect damage, sunburn, and crowding. For the colchicine treatment groups, 10.9% of the 0.1% colchicine group, 13.1% of the 0.25% colchicine group, 25% of the 0.5% colchicine group, and 17.4% of the colchicine 75% group exhibited a stunted phenotype with short internodes, compared to 6.7% of the control; while 1.8% of the 0.1% colchicine group, 4.9% of the 0.25% colchicine group, 22.9% of the 0.5% colchicine group, and 15.2% of the colchicine 75% group had thick, misshapen leaves with prominent midribs, compared to 0% of the control. Ten of the latter thick-leaved plants had stomata guard cells that were larger than the control. Six were shown by flow cytometry to have a greater amount of DNA per cell than the control.
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