Microbiome characterization of rhizobacteria under different agricultural practices of Thung Kula Rong Hai, and their abilities in promoting growth, salt tolerance and aromatic compound of KDML105 aromatic rice

Thèse soutenue le 20 octobre 2021 - Chiang Mai University

Chinachanta’s research focused on the metagenome of rhizobacteria and the influences of farming practices in the paddy farmers’ field of Thung Kula Rong Hai on soil properties and major aroma compound, 2-acetyl-1-pyrroline (2AP), and evaluation of rhizobacteria in promoting growth, salt tolerance and 2AP level in KDML105 aromatic rice study sites in 2018, experiments for this research was carried out in 2019-2021.

The determination of 18 farmers’ rainfed paddy fields in the TKR area indicated that organic rice farming (ORF) markedly increased soil microbial population and major soil properties particularly soil organic matter (SOM) than conventional rice farming (CRF). The higher microbial population and SOM in the ORF appeared to play a key role in promoting the population of rhizosphere microorganisms as well as the 2AP content in Khao Daw Mali 105 (KDML105) aromatic rice grains. Metagenomic analysis of rhizobacteria obtained from the rice rhizosphere indicated significantly higher species richness of the ORF than the CRF system. Furthermore, the rhizobacterial community composition was significantly correlated with soil properties particularly SOM. Interestingly, the 2AP content in the rice grains was also showing significant positive correlations with the richness of the rhizobacterial community. Nine selected rhizobacterial strains exhibited various plant growth promoting activities (IAA production, P, K solubilization and siderophore production). The ORF system also provided much higher IAA positive isolates with higher IAA producing ability than the CRF system. The highest IAA producing isolates, ORF15-23 (176.2 μg IAA mL-1) belonging to Sinomonas sp. appeared to produce IAA via L-Trp-independent pathway. Under salt stress, ORF15-23 exhibited the best in 2AP and IAA production including P and K solubilization. Biopriming of KDML 105 rice seeds by rhizobacterial strains, particularly ORF15-23, significantly enhance the seed germination when compared with IAA standard solution and negative control.

Overall Chinachanta’s dissertation results showed that ST-PGPR strains obtained from these investigations could be useful in developing bioinoculants to increase stress tolerance and promote both the yield and 2AP level of KDML105 rice in TKR salt-affected areas. In addition, environmentally friendly technologies especially ST-PGPR bioinoculants could support sustainability of KDML105 world-renowned geographical indication (GI) products. However, the promising isolates obtained in this study should be evaluated under TKR field conditions for their effects on rice nutrients uptake and growth including the 2AP level before developing them as biofertilizer.


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