Characterization of microbial functional diversity and bacterial community structure affected by fertiliser, soil and plant growth stages in aerobic rice
Aerobic rice was introduced to increase water use efficiency. The rhizosphere of aerobic rice differs from that of conventional flooded rice due to their habitat differences. Recognizing the importance of microorganism to ecosystem function, bacterial community in aerobic rice rhizosphere was...
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Format: | Thesis |
Language: | English |
Published: |
2020
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Online Access: | http://psasir.upm.edu.my/id/eprint/98818/1/IPTSM%202021%2019%20UPMIR.pdf |
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Summary: | Aerobic rice was introduced to increase water use efficiency. The rhizosphere of
aerobic rice differs from that of conventional flooded rice due to their habitat
differences. Recognizing the importance of microorganism to ecosystem
function, bacterial community in aerobic rice rhizosphere was studied as a
fundamental step towards the improvement of aerobic rice. Inorganic fertiliser
could affect the microbial functional diversity and bacterial community structure
of rhizosphere microorganism, which play a vital role in plant growth and soil
fertility. Hence, the aim of this study was to determine the effect of fertiliser and
soil type on microbial functional diversity bacterial community in aerobic rice
rhizosphere. To achieve this, a total of 3 specific objectives was conducted. The
first objective is to assess the effect of fertiliser rate and soil type on microbial
functional diversity and bacterial community structure. The second objective is
to determine the influence of fertiliser and soil type on the bacterial community
composition and nitrogen cycling functional potential in the rhizosphere of
aerobic rice. The third objective for this study is to evaluate the effect of plant
growth stages on the microbial community in the rhizosphere of aerobic rice.
Aerobic rice variety MRIA 1 was chosen for this study. A total of 4 different
fertiliser rate was selected and tested with 2 different soil types. Non-fertilised,
100 kg/ha, 200 kg/ha, and 400 kg/ha of NPK compound fertiliser were applied
to peat and sandy clay loam soil. The soil properties tested for this study were
pH, soil moisture, cation exchange capacity, soluble phosphorus, total carbon,
total nitrogen, and mechanical analysis. Plant growth characteristic recorded
were plant length, numbers of tillers per hill, panicle length and straw nitrogen
concentration. Microbial functional diversity was characterized by assessing the
microbial activity and community level physiological profile using Biolog
plicon sequencing was used to determined bacterial
community structure, bacterial community composition, and nitrogen cycling
functional potential. RDP FunGene was used to predict the functional potential
of bacterial communities. Aerobic culturable microbial abundance was agar, and starch casein agar was used to quantify the abundance of bacteria,
nitrogen-fixing microbes, fungi, phosphate-solubilizing microbes and
actinomycetes, respectively. For the plant growth stages, samples were taken
during the tillering, booting, grain filling, and mature stage. Microbial community
were estimated using physiological fingerprints and microbial culturable
abundance. Although peat and sandy clay loam were impacted differently when
applied with different fertiliser rate, microbial functional diversity responded
positively for both soils. The distinct microbial evenness between peat and sandy
clay loam suggested that microbial functional diversity is dependent on soil
properties. Carboxylic acid and acetic acid as well as carbohydrates were
sensitive carbon sources that create dissimilar metabolic function of rhizosphere
bacterial community in aerobic rice. L-arginine, L-asparagine, L- -
cyclodextrin, N- -d-lactose were good indicators for
distinguishing rhizosphere that added with fertiliser. 16s amplicon sequencing
analysis demonstrated that Alphaproteobacteria, Nitrospirae and Bacteroidetes
were identified as critical phyla when fertiliser added in peat while
Gammaproteobacteria was the crucial phylum in sandy clay loam.
Acidobacteria-6 and Chloracidobacteria were positive indicator showing that
excessive fertiliser was applied in both soils. The addition of all fertiliser rate
tested influenced the bacterial community composition by shifting the
communities. This was shown through the increase of abundance by Candidatus
Nitrososphaera and the decrease of abundance by Dok59, Olivibacter,
Thermomonas and Dactylosporangium in peat. The bacterial communities in the
sandy clay loam were shifted and shown by the increase of Clostridia and
Solirubrobacter. The changes in bacterial communities such as increase and
decrease of type of genera were dependent on soil chemical and physical
properties. Although, rhizosphere bacterial communities were different in peat
and sandy clay loam, the function of the genera in the communities was the
same after fertiliser was introduced. The selection of genera during the bacterial
commun
type particularly soil properties. Desulfovibrio was identified as a genus that
presence only in nonfertilised rhizosphere and can be used as an indicator in
natural rhizosphere. Chitinophaga, Desulfosporosinus, Geobacillus,
Nannocystis, Nitrosovibrio, and Perlucidibaca were the genus that solely
presence in fertilised rhizosphere and can be used as an indicator in fertilised
rhizosphere. Genera that solely presence in the fertilised rhizosphere were
mainly contributed to nitrogen cycling. The growth stage of aerobic rice has an
effect on determining the response and composition of microbial community in
soil. Microbial community in rhizosphere responded according to plant effect
produced during plant development which is primarily determined by soil type.
Soil type particularly the soil physical and chemical properties are important
factors in shaping the microbial community by directly influencing the
environment of rhizosphere. This study concluded that microbial functional
diversity and bacterial community in aerobic rice rhizosphere were influenced by
fertiliser, soil type and growth stage. The use of fertiliser in the recommended
rate (200 kg/ha of NPK compound fertiliser) is suitable in maintaining the function
of bacterial community and thus positively influence the growth of aerobic rice. |
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