Plant growth promoting rhizobacteria reduce aphid population and enhance the productivity of bread wheat

Abstract Plant growth promoting rhizobacteria increase plant growth and give protection against insect pests and pathogens. Due to the negative impact of chemical pesticides on environment, alternatives to these chemicals are needed. In this scenario, the biological methods of pest control offer an eco-friendly and an attractive option. In this study, the effect of two plant growth promoting rhizobacterial strains (Bacillus sp. strain 6 and Pseudomonas sp. strain 6K) on aphid population and wheat productivity was evaluated in an aphid susceptible (Pasban-90) and resistant (Inqlab-91) wheat cultivar. The seeds were inoculated with each PGPR strain, separately or the combination of both. The lowest aphid population (2.1 tiller−1), and highest plant height (85.8 cm), number of spikelets per spike (18), grains per spike (44), productive tillers (320 m−2), straw yield (8.6 Mg ha−1), and grain yield (4.8 Mg ha−1) were achieved when seeds were inoculated with Bacillus sp. strain 6 + Pseudomonas sp. strain 6K. The grain yield of both varieties was enhanced by 35.5-38.9% with seed inoculation with both bacterial strains. Thus, the combine use of both PGPR strains viz. Bacillus sp. strain 6 + Pseudomonas sp. strain 6K offers an attractive option to reduce aphid population tied with better wheat productivity.

Plant growth promoting rhizobacteria reduce aphid population and enhance the productivity of bread wheat

Abstract Plant growth promoting rhizobacteria increase plant growth and give protection against insect pests and pathogens. Due to the negative impact of chemical pesticides on environment, alternatives to these chemicals are needed. In this scenario, the biological methods of pest control offer an eco-friendly and an attractive option. In this study, the effect of two plant growth promoting rhizobacterial strains (Bacillus sp. strain 6 and Pseudomonas sp. strain 6K) on aphid population and wheat productivity was evaluated in an aphid susceptible (Pasban-90) and resistant (Inqlab-91) wheat cultivar. The seeds were inoculated with each PGPR strain, separately or the combination of both. The lowest aphid population (2.1 tiller1), and highest plant height (85.8 cm), number of spikelets per spike (18), grains per spike (44), productive tillers (320 m2), straw yield (8.6 Mg ha1), and grain yield (4.8 Mg ha1) were achieved when seeds were inoculated with Bacillus sp. strain 6 + Pseudomonas sp. strain 6K. The grain yield of both varieties was enhanced by 35.538.9% with seed inoculation with both bacterial strains. Thus, the combine use of both PGPR strains viz. Bacillus sp. strain 6 + Pseudomonas sp. strain 6K offers an attractive option to reduce aphid population tied with better wheat productivity.

Arachidicoccus ginsenosidivorans sp. nov., with ginsenoside-converting activity isolated from ginseng cultivating soil.

A Gram-reaction-negative, catalase- and oxidase-positive, aerobic, non-motile, light yellow and rod-shaped bacterium (designated Gsoil 809T) isolated from soil of ginseng field, was characterized by a polyphasic approach to clarify its taxonomic position. Strain Gsoil 809T was observed to grow optimally at 30 °C and at pH 7.0 on nutrient agar medium. Strain Gsoil 809T possessed ß-glucosidase activity, which was responsible for its ability to transform protopanaxatriol-type ginsenoside Rg1 to ginsenoside Rh1. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain Gsoil 809T belongs to the genus Arachidicoccus of the family Chitinophagaceae and was most closely related to Arachidicoccusrhizosphaerae Vu-144T (98.1 % 16S rRNA gene sequence similarity). The DNA G+C content was 39.4 mol%. The DNA-DNA hybridization value between strain Gsoil 809T and A.rhizosphaerae Vu-144T was 41.27±1.03 %. The major polar lipids were phosphatidylethanolamine and an unknown polar lipid. The predominant quinone was MK-7. The major fatty acids were iso-C15 : 0, iso-C15 : 1 G, iso-C17 : 0 3-OH and summed feature 3, which supported the affiliation of Gsoil 809T to the genus Arachidicoccus. Strain Gsoil 809T contained homospermidineas the major polyamine. Moreover, the physiological and biochemical test results and low DNA-DNA relatedness value allowed the phenotypic and genotypic differentiation of strain Gsoil 809T from recognized species of the genus Arachidicoccus. Therefore, strain Gsoil 809T represents a novel species of the genus Arachidicoccus, for which the name Arachidicoccus ginsenosidivorans sp. nov. is proposed. The type strain is Gsoil 809T (=KCTC 22820T=JCM 30984T).

Sphingobacterium jejuense sp. nov., with ginsenoside-converting activity, isolated from compost.

A Gram-stain-negative, strictly aerobic, non-motile, light yellow, short-rod bacterium (designated GJ30-7T) isolated from compost, was characterized using a polyphasic approach, in order to clarify its taxonomic position. Strain GJ30-7T was observed to grow optimally at 30 °C and at pH 7.0 on R2A agar medium. Strain Gsoil GJ30-7T possessed ß-glucosidase activity, which was responsible for its ability to transform ginsenosides Rb1 and Rc (the two main active components of ginseng) to ginsenoside F2. Phylogenetic analysis, based on 16S rRNA gene sequence similarities, indicated that GJ30-7T belongs to the genus Sphingobacterium of the family Sphingobacteriaceae and was most closely related to Sphingobacterium yanglingense JCM 30166T (92.6 %), Sphingobacterium psychroaquaticum KACC 18188T (92.6 %), and Sphingobacterium thermophilum KCTC 23708T (92.0 %). The DNA G+C content was 43 mol% and MK-7 was the major isoprenoid quinone. The main polar lipids were phosphatidylethanolamine, one unidentified phospolipid and one unknown polar lipid. In contrast to standard and reference strains, unidentified sphingolipid was also present. The predominant fatty acids of strain GJ30-7T were iso-C15 : 0, iso-C17 : 0 3-OH, C16 : 1ω7c and/or C16 : 1ω6c (summed feature 3) and iso-C17 : 1ω9c and/or C16 : 0 10-methyl (summed feature 9), supporting the affiliation of strain GJ30-7T to the genus Sphingobacterium. However, strain GJ30-7T could be distinguished genotypically and phenotypically from species of the genus Sphingobacterium with validly published names. The novel isolate therefore represents a novel species, for which the name Sphingobacterium jejuense sp. nov. is proposed, with the type strain GJ30-7T (=KACC 18625T=JCM 30948T).

Nitrospirillum irinus sp. nov., a diazotrophic bacterium isolated from the rhizosphere soil of Iris and emended description of the genus Nitrospirillum.

A polyphasic approach was used to characterize a novel nitrogen-fixing bacterial strain, designated YC6995(T), isolated from the rhizosphere soil of Iris ensata var. spontanea (Makino) Nakai inhabiting a wetland located at an altitude of 960 m on Jiri Mountain, Korea. Strain YC6995(T) cells were Gram-negative, and rod-shaped, with motility provided by a single polar flagellum. Optimal growth conditions were 30 °C and pH 7.0. The major fatty acids of strain YC6995(T) were C18:1 ω7c, C18:1 2-OH and C16:0 3-OH. The major respiratory quinone was ubiquinone-10 (Q-10). The polar lipids were phosphatidylethanolamine, phosphatidyldimethylethanolamine, phosphatidylcholine, phosphatidylglycerol and unidentified glycolipids. The genomic DNA G+C content was 64.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed strain YC6995(T) to form a phyletic lineage with Nitrospirillum amazonense DSM 2787(T) with a high sequence similarity (97.2 %), but it displayed low sequence similarity with other remotely related genera, including Azospirillum (<93 %), Rhodocista (93.1-93.4 %), and Skermanella (91.2-93.3 %) in the family Alphaproteobacteria. Based on the phenotypic, chemotaxonomic, and phylogenetic evidences, strain YC6995(T) represents a novel species within the genus Nitrospirillum, for which the name Nitrospirillum irinus sp. nov. is proposed. The type strain is YC6995(T) (= KACC 13777(T) = DSM 22198(T)). An emended description of the genus Nitrospirillum is also proposed.

Chitinophaga vermicomposti sp. nov., with antifungal activity, isolated from vermicompost.

A Gram-negative, rod-shaped bacterial strain, YC6729T, was isolated from the vermicompost (VC) collected at Masan, Korea and its taxonomic position was investigated by a polyphasic taxonomic approach. Strain YC6729T grew optimally at 30 degrees C and at pH 6.5-8.5. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain YC6729T belongs to the genus Chitinophaga in the family Chitinophagaceae. Most closely related species are Chitinophaga terra KP01T (96.4 %), Chitinophaga ginsengisegetis Gsoil 040T (96.1 %) and Chitinophaga arvensicola IAM 12650T (96.1 %). Strain YC6729T contained MK-7 as the major menaquinone and homospermidine as the major polyamine. The major fatty acids of strain YC6729T C15:0 iso, C16:1omega5c and C17:0 iso 3-OH. The total DNA G+C content was 48.9 mol%. The phenotypic, chemotaxonomic and phylogenetic data showed that strain YC6729T represents a novel species of the genus Chitinophaga, for which the name Chitinophaga vermicomposti sp. nov. is proposed. The type strain is YC6729T (= KACC 13774T = DSM 22224T).

Gynumella flava gen. nov., sp. nov., isolated from the rhizosphere of rice (Oryza sativa L.) managed under a no-tillage regime.

A bacterial strain designated YC6842T, isolated from the rhizosphere of rice (Oryza sativa L.) managed under no-tillage practice in Jinju, Korea, was characterized using polyphasic taxonomic approach. Cells of the strain were Gram-negatively stained, aerobic, rod-shaped and motile by multiple polar flagella. It grew at a temperature of 20 to 40 degrees C (optimum at 28 degrees C). Growth occurred between pH 6.0 and 10.0, with an optimum of pH 7.0-8.0. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain represented a separate clade within the family Xanthomonadaceae. It showed the highest 16S rRNA gene sequence similarity with Dyella yeojuensis R2A16-10T (93.6 %). The DNA G+C content was 62.6 mol%. Q-8 was the major quinone. Major polar lipids were diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and phosphatidylglycerol (PG). Phylogenetic analysis, biochemical and physiological characteristics strongly supported the genotypic and phenotypic differentiation of the strain YC6842T from the validly published genera of the family Xanthomonadaceae. Therefore, it is proposed that the strain YC6842T represents a novel species within a novel genus, with the name Gynumella flava gen. nov., sp. nov. The type strain is YC6842T (= KCTC 22443T = DSM 21636T).

Eiseniicola composti gen. nov., sp. nov., with antifungal activity against plant pathogenic fungi.

A Gram-negative, short rod-shaped bacterial strain, YC06271T, was isolated from the vermicompost (VC) collected at Masan, Korea and its taxonomic position was investigated by a polyphasic taxonomic approach. Strain YC06271T grew optimally at 28-30 degrees C and at pH 7.0-9.0. The 16S rRNA gene sequence of strain YC06271T was most closely related to members of the genera Bordetella (96.4-95.8 %), Achromobacter (96.0-95.7 %), Alcaligenes (96.0-94.2 %), Pusillimonas noertemannii (95.9 %), Pigmentiphaga (95.8-95.5 %) and less than 95.5 % similarity with the members of the other genera of the family Alcaligenaceae. Strain YC06271T contained ubiquinone-8 (Q-8) as the major respiratory quinone system and putrescine as the major polyamine. The major fatty acids of strain YC06271T were C16:1omega7c and/or C15:0 iso 2-OH and C16:0. The major polar lipids were phosphatidylglycerol and phosphatidylethanolamine. The G+C content of the genomic DNA was 55.4 mol%. Phylogenetic analysis, biochemical, chemotaxonomic and phenotypic characteristics strongly supported the differentiation of strain YC06271T from the validly published genera of the family Alcaligenaceae. Therefore, it is proposed that strain YC06271T represents a novel species within a novel genus, with the name Eiseniicola composti gen. nov., sp. nov. The type strain is YC06271T (= KCTC 22250T = DSM 21045T).

Sphingosinicella vermicomposti sp. nov., isolated from vermicompost, and emended description of the genus Sphingosinicella.

A Gram-stain-negative, rod-shaped bacterium, designated strain YC7378(T) was isolated from vermicompost (VC) collected at Masan, Korea, and its taxonomic position was investigated by using a polyphasic approach. Strain YC7378(T) grew optimally at 30 degrees C and at pH 6.5-8.5. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain YC7378(T) belongs to the genus Sphingosinicella in the family Sphingomonadaceae. The most closely related strains are Sphingosinicella soli KSL-125(T) (95.7 %), Sphingosinicella xenopeptidilytica 3-2W4(T) (95.6 %) and Sphingosinicella microcystinivorans Y2(T) (95.5 %). Strain YC7378(T) contained ubiquinone Q-10 as the major respiratory quinone system and sym-homospermidine as the major polyamine. The major fatty acids of strain YC7378(T) were C(18 : 1)omega7c, C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH, C(14 : 0) 2-OH and C(16 : 0). The major polar lipids were sphingoglycolipid, diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The total DNA G+C content was 59.4 mol%. The phenotypic, phylogenetic and chemotaxonomic data showed that strain YC7378(T) represents a novel species of the genus Sphingosinicella, for which the name Sphingosinicella vermicomposti sp. nov. is proposed. The type strain is YC7378(T) (=KCTC 22446(T) =DSM 21593(T)).

Arenimonas oryziterrae sp. nov., isolated from a field of rice (Oryza sativa L.) managed under a no-tillage regime, and reclassification of Aspromonas composti as Arenimonas composti comb. nov.

The taxonomic position of a novel bacterial strain, YC6267(T) isolated from a field of rice (Oryza sativa L.) managed under a no-tillage regime in Jinju, Korea, was studied using a polyphasic taxonomic approach. Cells of the strain were Gram-stain-negative, rod-shaped and aerobic. It grew at 15-37 degrees C (optimum at 28 degrees C). Growth of the strain occurred between pH 5.0 and 10.0, with an optimum of pH 7.0-8.0. The G+C content of the total DNA was 65.8 mol%. The 16S rRNA gene sequence of the strain was most closely related to species of the genera Arenimonas (95.6-94.4 %) and Aspromonas (95.1 %), with <95.0 % similarity to species of the genus Lysobacter and other genera of the family Xanthomonadaceae. Chemotaxonomic data (major quinone Q-8; major polar lipids phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol; and major fatty acids iso-C(15 : 0), iso-C(14 : 0), iso-C(16 : 0), and iso-C(17 : 1)omega9c) supported the affiliation of strain YC6267(T) to the genus Arenimonas. Phylogenetic analysis based on 16S rRNA gene sequences and biochemical and physiological characteristics strongly supported the genotypic and phenotypic differentiation of strain YC6267(T) from described species of the genus Arenimonas. Strain YC6267(T), therefore, represents a novel species, for which the name Arenimonas oryziterrae sp. nov. is proposed. The type strain is YC6267(T) (=KCTC 22247(T) =DSM 21050(T)). In addition, the reclassification of Aspromonas composti as Arenimonas composti comb. nov. is proposed (type strain TR7-09(T) =KCTC 12666(T) =DSM 18010(T)). A common line of descent and a number of shared phenotypic traits support this reclassification.

Lysobacter oryzae sp. nov., isolated from the rhizosphere of rice (Oryza sativa L.).

The taxonomic position of a novel bacterial strain, YC6269(T), isolated from the rhizosphere of rice (Oryza sativa L.) managed under no-tillage practice in Jinju, South Korea, was studied using polyphasic approach. Cells of the strain were Gram-negative, rod-shaped and facultatively anaerobic. The novel strain grew at a temperature of 15-42 degrees C (optimum at 28 degrees C). Growth of the strain occurred between pH 5.5 and 11.0, with an optimum at pH 7.0-8.0. The G+C content of the total DNA was 67.4 mol%. The 16S rRNA gene sequence of the strain was most closely related to species of the genus Lysobacter, Lysobacter yangpyeongensis DSM 17635(T) (98.6 %), Lysobacter niabensis GH34-4(T) (97.2 %), Lysobacter enzymogenes DSM 2043(T) (96.9 %), Lysobacter daejeonensis DSM 17634(T) (96.3 %) and Lysobacter niastensis GH41-7(T) (96.2 %). The novel strain showed <96.0 % similarity with other species of the genus Lysobacter. Chemotaxonomic data (major quinone, Q-8; major polar lipids, phosphatidylethanolamine, phosphatidylglycerol and phosphatidyl-N-methylethanolamine, and major fatty acids, C(15 : 0) iso, C(16 : 0) iso, C(17 : 0) iso and C(17 : 1) iso omega9c) supported the affiliation of strain YC6269(T) to the genus Lysobacter. Phylogenetic analysis based on the 16S rRNA gene sequences, DNA-DNA hybridization data and biochemical and physiological characteristics strongly supported the genotypic and phenotypic differentiation of strain YC6269(T) from recognized species of the genus Lysobacter. Strain YC6269(T), therefore, represents a novel member of the genus Lysobacter, for which the name Lysobacter oryzae sp. nov. is proposed. The type strain is YC6269(T) (=KCTC 22249(T)=DSM 21044(T)).

Lysobacter capsici sp. nov., with antimicrobial activity, isolated from the rhizosphere of pepper, and emended description of the genus Lysobacter.

The taxonomic position of a novel bacterial strain, YC5194(T), with antimicrobial activity, isolated from the rhizosphere of pepper in Jinju, South Korea, was studied using a polyphasic approach. Cells of the strain were Gram-negative, rod-shaped, facultative anaerobes. It grew at a temperature of 15-37 degrees C (optimum 28 degrees C). Growth of the strain occurred between pH 5.5 and 8.5, with an optimum of pH 7.0-7.5. The strain inhibited mycelial growth of Pythium ultimum, Colletotrichum gloeosporioides, Fusarium oxysporum, Botrytis cinerea, Rhizoctonia solani and Botryosphaeria dothidea and growth of Bacillus subtilis. The G+C content of the total DNA was 65.4 mol%. The 16S rRNA gene sequence of the strain was most closely related to species of the genus Lysobacter (<94.0 to >99.0 % sequence similarity). Chemotaxonomic data (major quinone, Q-8; major polar lipids, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidyl-N-methylethanolamine; major fatty acids, iso-C(15 : 0), summed feature 3, C(16 : 0), iso-C(17 : 1)omega9c and C(18 : 1)omega7c) supported the affiliation of strain YC5194(T) to the genus Lysobacter. Phylogenetic analysis based on 16S rRNA gene sequences, DNA-DNA hybridization data and biochemical and physiological characteristics strongly supported the genotypic and phenotypic differentiation of strain YC5194(T) from species of Lysobacter with validly published names. Strain YC5194(T) therefore represents a novel species, for which the name Lysobacter capsici sp. nov. is proposed. The type strain is YC5194(T) (=KCTC 22007(T) =DSM 19286(T)).

Paenibacillus ginsengisoli sp. nov., a novel bacterium isolated from soil of a ginseng field in Pocheon Province, South Korea.

A Gram-positive, aerobic or facultative anaerobic, motile, spore-forming bacterial strain, designated Gsoil 1638T, was isolated from a soil sample of a ginseng field in Pocheon province (South Korea), and was characterized taxonomically by using a polyphasic approach. It grew well on nutrient agar medium, utilized a fairly narrow spectrum of carbon sources and tolerated 10% NaCl. The isolate was positive for catalase and oxidase tests but negative for the degradation of macromolecules such as casein, collagen, starch, chitin, CM-cellulose, xylan and DNA. The G + C content of the genomic DNA was 50.7 mol%. The predominant isoprenoid quinone was menaquinone 7 (MK-7). The major fatty acids were anteiso-C15:0 (44%) and C16:0 (25%). Comparative 16S rRNA gene sequence analysis showed that strain Gsoil 1638T fell within the radiation of the cluster comprising Paenibacillus species and joined Paenibacillus anaericanus DSM 15890T with a bootstrap value of 100%. These two strains shared 99.5% 16S rRNA gene sequence similarity with each other. The phylogenetic distance from any other validly described species within the genus Paenibacillus was less than 96.2%. DNA-DNA relatedness value between strain Gsoil 1638T and its closest phylogenetic neighbor, Paenibacillus anaericanus, was 62%. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain Gsoil 1638T (= KCTC 13931T = LMG 23406T = CCUG 52472T) was classified in the genus Paenibacillus as the type strain of a novel species, for which the name Paenibacillus ginsengisoli sp. nov. is proposed.

Bacillus panaciterrae sp. nov., isolated from soil of a ginseng field.

A Gram-positive, non-motile, endospore-forming bacterium, designated Gsoil 1517(T), was isolated from soil of a ginseng field in Pocheon Province (South Korea) and was characterized in order to determine its taxonomic position, using a polyphasic approach. It was found to rod-shaped and aerobic or facultatively anaerobic. It grew optimally at 30 degrees C and at pH 6.5-7.0. Comparative 16S rRNA gene sequence analysis showed that strain Gsoil 1517(T) forms a distinct phylogenetic lineage within the genus Bacillus, being related to Bacillus funiculus JCM 11201(T) (96.8 %). The strain showed less than 94.3 % sequence similarity with other Bacillus species. The G+C content of the genomic DNA was found to be 47.8 mol% and the predominant respiratory quinone was MK-7. The major fatty acids were iso-C(15 : 0) (42.4 %), anteiso-C(15 : 0) (17.4 %), iso-C(14 : 0) (9.7 %) and C(16 : 0) (6.0 %). On the basis of its phenotypic properties and phylogenetic distinctiveness, strain Gsoil 1517(T) represents a novel species of the genus Bacillus, for which the name Bacillus panaciterrae sp. nov. is proposed. The type strain is Gsoil 1517(T) (=KCTC 13929(T)=CCUG 52470(T)=LMG 23408(T)).

Lactobacillus siliginis sp. nov., isolated from wheat sourdough in South Korea.

The taxonomic position of two lactic-acid-producing bacterial strains, isolated from wheat sourdough in South Korea, was studied using a polyphasic approach. Phylogenetic analysis on the basis of 16S rRNA gene sequences and biochemical and physiological characteristics indicated these two strains to be members of the genus Lactobacillus. They had high 16S rRNA gene sequence similarity (98.5 %) with Lactobacillus rossiae DSM 15814(T) and very low (<94.0 %) similarity with any other recognized species of the genus Lactobacillus. These two strains (designated M1-212(T) and M2-236) were heterofermentative, facultatively anaerobic, Gram-positive, non-spore-forming, non-motile, short rod-shaped bacteria. The optimum growth temperature for these strains was 30 degrees C (no growth at 15 or 45 degrees C) and they were able to tolerate 5 % (w/v) NaCl. The G+C content of the genomic DNA of the two strains was 45.5 mol%, within the range of values reported for the genus Lactobacillus (32-53 mol%). The peptidoglycan was of the A3alpha (l-lys-d-glu-l-Ala) type. Physiological, biochemical and genotypic data, as well as results of DNA-DNA hybridization of the genomic DNA with one of the closest phylogenetic relatives, L. rossiae DSM 15814(T), indicated that the strains represent a novel species of the genus Lactobacillus, for which the name Lactobacillus siliginis sp. nov. is proposed. The type strain is M1-212(T) (=KCTC 3985(T)=NBRC 101315(T)).