Influences of farming practices on soil properties and the 2-Acetyl-1-pyrroline content of Khao Dawk Mali 105 rice grains

Khao Dawk Mali 105 (KDML105) is a premium fragrant rice variety and is widely grown in )ung Kula Rong Hai (TKR), northeast )ailand. In the present study, the influence of organic and conventional rice farming (ORF and CRF, respectively) in TKR farmers’ paddy fields on soil properties and their relationship with 2-acetyl-1-pyrroline (2AP) in KDML105 rice grains were investigated. )e results indicated that the ORF system had a strong positive effect on major soil quality indicators and the 2AP content in the rice grains. )e soil organic matter (SOM) was approximately twice as much in the ORF than in the CRF system, thus leading to much higher total nitrogen (TN), humic acid (HA), and microbial populations in the ORF system.)ehigher SOM in the ORF system not only enhanced the soil quality indicators but also contributed to approximately 3.5 times higher 2AP than in the CRF system. Principle component analysis indicated a close correlation among SOM, TN, HA, and microbial population under the ORF system; these variables exhibited strong correlations with the 2AP contents in KDML105 rice grains

Enhancement of the Aroma Compound 2-Acetyl-1-pyrroline in Thai Jasmine Rice (Oryza sativa) by Rhizobacteria under Salt Stress

Thai jasmine rice (Oryza sativa L. KDML105), particularly from inland salt-affected areas in Thailand, is both domestically and globally valued for its unique aroma and high grain quality. The key aroma compound, 2-acetyl-1-pyrroline (2AP), has undergone a gradual degradation due to anthropogenic soil salinization driven by excessive chemical input and climate change. Here, we propose a cheaper and an ecofriendly solution to improve the 2AP levels, based on the application of plant growth-promoting rhizobacteria (PGPR). In the present study, nine PGPR isolates from rice rhizosphere were investigated for the 2AP production in liquid culture and the promotion potential for 2AP content in KDML105 rice seedlings under four NaCl concentrations (0, 50, 100, and 150 mM NaCl). The inoculation of 2AP-producing rhizobacteria resulted in an increase in 2AP content in rice seedling leaves with the maximum enhancement from Sinomonas sp. ORF15-23 at 50 mM NaCl (19.6 µg·kg−1), corresponding to a 90.2% increase as compared to the control. Scanning electron microscopy confirmed the colonization of Sinomonas sp. ORF15-23 in the roots of salinity-stressed KDML105 seedlings. Our results provide evidence that Sinomonas sp. ORF15-23 could be a promising PGPR isolate in promoting aroma level of Thai jasmine rice KDML105 under salt stress

Isolation and characterization of KDML105 aromatic rice rhizobacteria producing indole-3-acetic acid: impact of organic and conventional paddy rice practices

International audienceIndole-3-acetic acid (IAA) synthesis is a major property of rhizosphere bacteria. The IAA-producing ability of rhizobacteria may be influenced by agricultural management. We therefore evaluated the IAA-producing potential of rhizobacteria isolated during organic rice farming (ORF) and conventional rice farming (CRF) in Thung Kula Rong Hai areas of Thailand. The results indicated that ORF gave a significantly higher percentage of IAA producers (95 center dot 8%) than CRF (69 center dot 9%). The average IAA values of the ORF isolates were around two times higher than those of the CRF isolates both in the absence (12 center dot 8 and 5 center dot 8 mu g IAA ml(-1), respectively) and presence of L-tryptophan (L-Trp) (35 center dot 2 and 17 center dot 2 mu g IAA ml(-1), respectively). The 16S rRNA gene sequence analysis indicated that the 23 selected isolates belonged to 8 different genera-Sinomonas sp., Micrococcus sp., Microbacterium sp., Fictibacillus sp., Bacillus sp., Burkholderia sp., Leclercia sp. and Enterobacter sp. Interestingly, only three ORF isolates, i.e. ORF15-20 (Micrococcus sp.), ORF15-21 (Sinomonas sp.) and ORF15-23 (Sinomonas sp.), exhibited high IAA production ability without L-Trp (128 center dot 5, 160 center dot 8 and 174 center dot 7 mu g IAA ml(-1), respectively). Meanwhile, a slight decrease in IAA production with L-Trp was noticed, suggesting that the L-Trp was not used for the IAA synthesis of these isolates. Biopriming with rhizobacterial isolates significantly enhanced the rate of germination of KDML 105 rice seeds compared to the control

Enhancement of the Aroma Compound 2-Acetyl-1-pyrroline in Thai Jasmine Rice (Oryza sativa) by Rhizobacteria under Salt Stress

International audienceThai jasmine rice (Oryza sativa L. KDML105), particularly from inland salt-affected areas in Thailand, is both domestically and globally valued for its unique aroma and high grain quality. The key aroma compound, 2-acetyl-1-pyrroline (2AP), has undergone a gradual degradation due to anthropogenic soil salinization driven by excessive chemical input and climate change. Here, we propose a cheaper and an ecofriendly solution to improve the 2AP levels, based on the application of plant growth-promoting rhizobacteria (PGPR). In the present study, nine PGPR isolates from rice rhizosphere were investigated for the 2AP production in liquid culture and the promotion potential for 2AP content in KDML105 rice seedlings under four NaCl concentrations (0, 50, 100, and 150 mM NaCl). The inoculation of 2AP-producing rhizobacteria resulted in an increase in 2AP content in rice seedling leaves with the maximum enhancement from Sinomonas sp. ORF15-23 at 50 mM NaCl (19.6 µg·kg−1), corresponding to a 90.2% increase as compared to the control. Scanning electron microscopy confirmed the colonization of Sinomonas sp. ORF15-23 in the roots of salinity-stressed KDML105 seedlings. Our results provide evidence that Sinomonas sp. ORF15-23 could be a promising PGPR isolate in promoting aroma level of Thai jasmine rice KDML105 under salt stress

Rhizoactinobacteria enhance growth and antioxidant activity in Thai jasmine rice (Oryza sativa) KDML105 seedlings under salt stress

Salinity is one of the most devastating abiotic stresses which hamper the growth and production of rice. Nine indole-3-acetic acid (IAA) producing salt-tolerant-plant growth-promoting rhizobacteria (ST-PGPR) were inoculated into Thai jasmine rice (Oryza sativa L.) variety Khao Dawk Mali 105 (KDML105) seedlings grown under different concentrations of NaCl (0, 50, 100, and 150 mM). ST-PGPR strains significantly promote growth parameters, chlorophyll content, nutrient uptake (N, P, K, Ca, and Mg), antioxidant activity, and proline accumulation in the seedlings under both normal and saline conditions compared to the respective controls. The K + /Na + ratio of the inoculated seedlings was much higher than that of the controls, indicating greater salt tolerance. The highest salt-tolerant and IAA producing strain Sinomonas sp. ORF 15-23, yielded the highest values of all the parameters, particularly at 50 mM NaCl. The percentage increases in these parameters relative to the controls were ranged from > 90% to 306%. Therefore, Sinomonas sp. ORF15-23 was considered a promising ST-PGPR to be developed as bioinoculants for enhancing the growth, salt tolerance, and aroma of the KDML105 rice in salt-affected areas. The environmentally friendly technologies such as ST-PGPR bioinoculants could also support the sustainability of KDML105 geographical indication (GI) products. However, the efficiency of Sinomonas sp. ORF15-23 should be evaluated under field conditions for their effect on rice nutrient uptake and growth, including the 2AP level

Arbuscular mycorrhizal fungus Rhizophagus irregularis expresses an outwardly Shaker-like channel involved in potassium nutrition of rice ( Oryza sativa L.)

Abstract Potassium (K + ) plays crucial roles in many physiological, molecular and cellular processes in plants. Direct uptake of this nutrient by root cells has been extensively investigated, however, indirect uptake of K + mediated by the interactions of the roots with fungi in the frame of a mutualistic symbiosis, also called mycorrhizal nutrient uptake pathway, is much less known. We identified an ion channel in the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis . This channel exhibits the canonical features of Shaker-like channel shared in other living kingdoms and is named RiSKC3. Transcriptionally expressed in hyphae and in arbuscules of colonized rice roots, RiSKC3 has been shown to be located in the plasma membrane. Voltage-clamp functional characterization in Xenopus oocytes revealed that RiSKC3 is endowed with outwardly-rectifying voltage-gated activity with a high selectivity for K + over sodium ions. RiSKC3 may have a role in the AM K + pathway for rice nutrition in normal and salt stress conditions. The current working model proposes that K + ions taken up by peripheral hyphae of R. irregularis are secreted towards the host root into periarbuscular space by RiSKC3. Significance Statement Mutualistic symbiosis with arbuscular mycorrhizal (AM) fungi are beneficial for about 80% of land plants thanks to an exchange of nutrients. The AM pathway responsible for potassium (K + ) nutrition of the plant is not known. Here we uncovered a key step of this phenomenon, by functionally characterizing the first transport system in the AM fungus Rhizophagus irregularis , and we univocally demonstrated that RiSKC3 is an K + outwardly-rectifying voltage-gated Shaker-like channel