BUKU ABSTRAK - Universiti Putra Malaysia

Agriculture
Keywords: Seabass immunity, freshwater seabass
Management of Citrus Huanglongbing Disease in Malaysia
Assoc. Prof. Dr. Kamaruzaman Sijam
Khairulmazmi Ahmad
Faculty of Agriculture, University Putra Malaysia,
43400 UPM Serdang, Selangor, Malaysia.
+603-8946 7234; kama@agri.upm.edu.my
In Malaysia, citrus is grown in commercial orchards, backyard and small holdings in various parts of the
country. Known citrus growing areas in Malaysia include Sarawak, Kelantan, Terengganu, Kedah, Perak, Johor,
Selangor and Pahang. Citrus trees are subjected to various diseases. Citrus huanglongbing (HLB) disease is
the most destructive disease to citriculture in Africa, Asia and America. The causal agent of HLB disease was
identified as a Candidatus liberibacter Asiticus. It is phloem-restricted bacterium belonging to a new genus
in the alpha-subdivision of the?-Proteobacteria. This disease is transmitted by citrus psyllid, Diaphorina citri,
usually found in poorly managed orchards and on new flushes. This disease is also considered to be one of the
major limiting factors in citrus production in the country. Recent studies showed that all the major citrus growing
localities in Peninsular Malaysia were shown to have incidence of HLB infection. Estimated percentage of HLB
disease incidence varied between localities, ranged from 28.3 to 53.8%. Generally, leaves of infected trees showed
mottling with green vein symptom. Population of D. citri is more abundant in the lowland areas such as Selangor
and Terengganu but was not detected at highland areas such as Cameron Highland, Pahang. However, moderate
level of vector infestation was observed in Lojing Highlands, Kelantan. Among the nine citrus species assessed
in the field, pummelo and Troyer citrange were recorded the highest number of trees with HLB infection which
highly correlated with the number of vector population on those species, followed by honey mandarin, Cleopatra,
mandarin and citrimelo. HLB incidence was not detected on kaffier lime. Management strategies of this pathogen
can be done through the use of healthy planting materials, quarantine, eradication of the source of inoculums,
chemical control of insect vector, proper fertilisation dates and other integrated pest management practices.
Keywords: Huanglongbing, citrus greening, diaphorina citri
Freshwater Sea Bass Module with Immune-enhancing Capability
Assoc. Prof. Dr. Mariana Nor Shamsudin
C Girish Palaniyappan, Mohd. Shater Zakaria and Nurul Hidayah Idris
Institute of Bioscience, University Putra Malaysia,
43400 UPM Serdang, Selangor, Malaysia.
+603-8947 2138; mariana@medic.upm.edu.my
Adaptation of seabass from brackish water to freshwater is an attractive alternative for fish enthusiasts.
Freshwater seabass offers added advantage to their brackish water counterpart in that the flesh is fresh, tasty,
odourless, soft and organoleptic acceptable by most fish eating individuals. In this project, an adaptation module
was designed with particular focused on the ability of sea-bass to maintain their immune balance in freshwater.
The effects of short-term freshwater acclimatization were investigated in juvenile sea-bass Lates calcarifer to
determine whether all sea-bass juveniles are able to live in freshwater and to investigate immunological basis
of a successful adaptation to freshwater. This laboratory trial was conducted to determine the use of fish feed
incorporated with formulated diet and the effect of salinity on growth and survival. The adaptation system
comprised salinity reduction of brackish water to freshwater in four steps, resulting in about two folds reduction.
In addition, the adaptation module is designed complete with feed in the form of pellets with immune-enhancing
capability. Throughout the experiment, the effects of abrupt transfer to lower salinity on their behaviour, daily
rates of growth and feeding, maintenance requirement and food conversion efficiency were studied. The system
was carried indoor, in a confined space and feasible to be practiced by any fish enthusiasts. The experimental
trial showed that reducing salinity was not found to be stressful and comparable survival to the control group
was evidenced through immunological response. On the differences in the dynamics (growth and mortality),
energetic properties and proximate analysis between marine and freshwater seabass, important implications
for determining the relationship between immuno-stimulation and immuno-suppression under environmental
factors, can be determined.
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