Citation
Baharun Azahar, Mohd Abdul Halim
(2014)
Turfgrass varietal improvement for shade and drought tolerance using gamma ray irradiation.
Masters thesis, Universiti Putra Malaysia.
Abstract
Turfgrass breeding aims to improve the characteristics of plants so that they become
more desirable agronomically and economically. Alternative methods’ using
mutagenic treatment is a relatively quick method for improvement of turfgrass.
Gamma ray irradiation can be used to improve turfgrass phenotype and enhance
tolerance to environmental stress. A series of experiments were conducted to
examine the response of turfgrass species to gamma ray irradiation, either in their
phenotypic and genotypic characteristics, and to study turfgrass mutant lines under
different shade and drought stress conditions. The mutant lines selected for
evaluation in these studies were based on desirable characteristics for performance
under stress.
Eight gamma ray dosages (0, 20, 40, 60, 80, 100, 150 and 200 Gy) were applied to
Axonopus compressus, Zoysia japonica and Cynodon dactylon at the Gamma Cell
Laboratory, Malaysian Institute of Nuclear Technology Research (MINT), Bangi,
Selangor to identify the optimum dosage for turfgrass mutation. Optimum dosage
was needed induce maximum mutation and to increase mutation rate. The optimum
dosage was calculated based on 50% radiosensitivity tests on survival rate and plant
height. The values 50% of radiosensitivity tests (LD50) were determined to be 52, 76
and 90 Gy for A.compressus, Z.japonica and C. dactylon, respectively. The
turfgrasses were radiated using the optimum dosage of gamma ray to produce
numerous mutants. A total of 1500 stolons of each species were radiated and planted
in biodegradable seed tray. In order to ensure the inheritance of these characteristics,
all mutants were isolated using the cutting back technique.
Most of the mutants had dwarf and semi-dwarf characters. Gamma ray irradiation
significantly altered the morphological parameters of turfgrass. The results showed
that 2.4%, 2.6% and 1.5% rate of mutation occurred for A. compressus, Z. japonica
and C. dactylon, respectively after exposing to the LD50 dosages. Thirty six lines
from A. compressus were recorded as mutants with five (A26-4-1, A61-1-1, A46-2-
1, A91-3-5, A13-2-5) showing high potential for further study. Thirty nine lines from
Z. japonica were recorded as mutant with five (Z131-3-1, Z36-3-1, Z13-1-2, Z12-2-1, Z2-2-1) of them showing high potential for further study. Twenty two lines from
C. dactylon were recorded as mutants with five (C43-4-1, C85-1-2, C59-2-2, C41-4-
1, C5-3-1) showing high potential for further study, while six (C43-4-1, C42-4-1,
C37-5-1, C83-3-2, C95-2-2, C13-3-3) of them were reselected for the shade
tolerance study.
In the drought tolerance study, six most tolerant mutant lines (A48-3-5, A64-2-2, A62-
3-1, A84-1-1, A26-4-1, A46-2-1) and A0 were subjected to five field capacity
treatments of -20, -30, -33 (control), -40 and -50 J/kg and were assessed for visual
quality and growth parameters. Shoot and root dry weights were also determined. A.
compressus showed low quality performance under extreme drought conditions and
many had died. A84-1-1 performed the best under drought conditions as it could
withstand up to -50 J/kg field capacity, and this was followed by A26-4-1 and A64-2-
2. In the shade tolerance study treatments were applied by exposing the grass to
three, six, nine or twelve hour’s of full sunlight per day. Generally, turfgrass showed
slow growth and low quality when exposed to less than 3 hours of sunlight. The quality
of C. dactylon was much better under long duration of full sunlight. Mutant line C43-4-
1 performed the best under shade with its outstanding quality in terms of colour,
density and uniformity. Durations with a minimum of at least 6 hours sunlight showed
good responses.
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