BUKU ABSTRAK - Universiti Putra Malaysia

Agriculture
Antioxidative Enzymes as Biochemical Markers in Malaysian Rice (Oryza sativa
L.) Cultivars under Submergence Condition
Prof. Dr. Maziah Mahmood
Revandy Iskandar Damanik, Mohd. Razi Ismail, Syahida Ahmad and Abd. Mohd. Zain
Faculty of Biotechnology and Biomolecular Sciences,
University Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
+603-8946 6703; maziahm@biotech.upm.edu.my
Submergence is the major risk factor limiting yield in several lowland rice-growing areas in South and
South-East Asia, especially in Malaysia. Although, the rice plant is one of the few crop species that can live
permanently waterlogged soils, it is unable to survive if it is completely submerged in water for an extended period.
Physiological comparisons between contrasting abiotic stress tolerant cultivars will improve the understanding
of stress-tolerant mechanisms. The potential involvement of activated oxygen species by submergence stress
was studied in two Malaysian rice cultivars, MR219-4 and MR219-9, and cultivar FR13A which is known to be
tolerant to submergence. Seedlings of these three rice cultivars were subjected to different submergence periods
(4, 8 and 12 days). Under 8 days of complete submergence, FR13A cultivar showed higher lipid peroxidation in
terms of malondialdehyde (MDA) level and activities of antioxidative enzymes, superoxide dismutase (SOD),
catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) when compared to the MR219-4
and MR219-9 cultivars. MR219-9 cultivar showed higher SOD (1.3 fold), APX (1.8 fold) and GR (3.6 fold)
activities after 12 days of submergence when compared to FR13A. The levels of SOD activity indicated that
detoxification of O2.- to H2O2 was maintained at a stable level throughout the submergence stress until up to 8
days and increased rapidly at 12 days of submergence. The results indicated that tolerance to submergence in rice
is associated until 8 days submergence for MR219-4 and FR13A cultivars, but mechanism in MR219-9 cultivar is
associated until 12 days submergence. These findings suggested that tolerance to submergence stress in rice may
be proved by increasing the capacity of antioxidative system.
Keywords: Antioxidant enzymes, Lipid peroxidase, cultivars, periods of stress, rice, submergence stress
Improved Plantlet Production by Scalp Formation in Tissue Cultured Bananas
Prof. Dr. Maziah Mahmood
Siamak Shirani, Sariah Moen and Zakaria Wahab
Institute of Tropical Agriculture, University Putra Malaysia,
43400 UPM Serdang, Selangor, Malaysia.
+603-8946 6703; maziahm@biotech.upm.edu.my
Shoot tip cultures produce only maximum 3.44, 7.07 and 4.22 shoots per explants in Berangan Intan, Rastali
and Berangan, respectively, with the optimum concentration of BAP (22.2 ?M), but SCALPs which consist
of several fleshy bulbous structures possessing highly proliferating meristems, are able to produce at least the
average number of 11.67, 14.33 and 9 shoots per explants in Berangan Intan, Rastali and Berangan, respectively,
with similar level of BAP treatment (22.2 ?M). Therefore, they can be a good replacing source compared to shoot
tips for rapidly mass propagation of bananas. The effect of cytokinins on scalp induction from in vitro propagating
shoot tips of different banana (Musa spp. AAA and AAB) cultivars was investigated. Lower level of BAP (11.1
?M) increased scalp induction. Kinetin caused an increase in scalp induction rate at higher concentration (22.2
?M). The highest ratio of scalp formation (8.89) was recorded for Rastali at the highest concentration of TDZ
(7.5 ?M), but for Berangan Intan and Berangan (AAA), TDZ increased scalp induction rate from 0.00 and 0.43
at 0.5 ?M to 4.22 and 2.67 at 5 ?M respectively before falling to 2.11 for both at 7.5 ?M. BAP at 22.2 ?M was
considered optimal for shoot proliferation as well as shoot elongation from excised scalps of banana cultivars.
These scalps with high proliferating capacity can be used for mass clonal propagation which consequently can
also be the preferred target material, for induced mutations and genetic engineering studies.
Keywords: Scalp induction, banana, micropropagation, cytokinins
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