Karakterizacija i diverzitet populacije sojeva Erwinia amylovora poreklom iz jabučastih voćaka gajenih u Srbiji

The diversity of 30 Erwinia amylovora strains, isolated from quince, pear and apple trees on 14 localities in Serbia, was studied using bacteriological and molecular methods. In pathogenicity tests, all strains caused necrosis and oozing of bacterial exudate on inoculated immature pear, cherry and plum fruits, and induced hypersensitive reaction in tobacco leaves. The studied strains were Gram and oxidase negative, non-fluorescent, levan and catalase positive and facultatively anaerobic. The strains did not reduce nitrates, but utilized citrate and produced acid from sorbitol, hydrolyzed gelatine, produced reducing substances from sucrose and grew in the presence of 5% NaCl, but not at 36oC. Identity of the strains was confirmed by conventional and nested PCR methods. Rep-PCR with REP, ERIC and BOX primers resulted in amplification of several DNA fragments respectively, but showed no variation within the strains. However, different genetic profiles were obtained with RAPD-PCR by using six primers which enabled differentiation of the strains into four groups. Genetic differences between the studied strains did not correlate with the host plants, geographical origin or year of isolation.Primenom standardnih bakterioloških i molekularnih metoda proučen je diverzitet 30 sojeva Erwinia amylovora izolovanih iz dunje, kruške i jabuke, poreklom iz 14 lokaliteta u Srbiji. Svi proučavani sojevi izazvali su nekrozu i pojavu bakterijskog eksudata na nesazrelim plodovima kruške, trešnje i šljive, kao i hipersenzitivnu reakciju duvana. Proučavani sojevi bili su Gram i oksidaza negativni, fakultativno anaerobni, levan i katalaza pozitivni i nisu stvarali fluorescentni pigment na Kingovoj podlozi B. Svi sojevi hidrolizuju želatin, koriste citrate i stvaraju kiselinu iz sorbitola, proizvode redukujuće supstance iz saharoze, ne redukuju nitrate, razvijaju se u prisustvu 5% NaCl, ali ne i pri 36°C. Identitet sojeva potvrđen je konvencionalnim PCR i nested PCR metodama. Rep-PCR metodom korišćenjem REP, ERIC i BOX prajmera umnoženo je više fragmenata DNK čiji broj i veličina su se podudarali kod svih proučavanih sojeva. Za razliku od Rep-PCR, primenom RAPD-PCR metode uz korišćenje šest prajmera došlo je do izdvajanja različitih genetičkih profila i diferencijacije sojeva u četiri grupe. Genetičke razlike među proučavanim sojevima nisu bile u korelaciji sa domaćinima iz kojih su izolovani, niti sa njihovim geografskim poreklom i godinom izolacije

Growth and Nutrient Uptake of Orchardgrass (Dactylis glomerata L.) and Meadow Fescue (Festuca pratensis Huds.) as Affected by Rhizobacteria

A diverse group of soil bacteria found in the rhizosphere which can colonize plant roots and improve plant growth are designated as plant growth promoting rhizobacteria. The aim of this study was isolation and screening of different rhizobacterial strains for plant growth promoting characteristics and their ability to improve growth of two grass species, orchardgrass (Dactylis glomerata L.) and meadow fescue (Festuca pratensis Huds.). The strains investigated, belonging to the genera Azotobacter, Bacillus, Pseudomonas and rhizobial bacteria, showed various plant growth promoting traits, such as phosphate solubilisation, siderophore production, and indole-3-acetic acid (IAA) production. Co-inoculation of meadow fescue with Azotobacter chroococcum A2 and Sinorhizobium meliloti or Pseudomonas sp., and A. chroococcum A5 with S. meliloti, significantly increased shoot dry weight (SDW)(25-33%), as well as total N (26-33%), P (24-31%) and K (26-28%) contents in plants (mg pot-1), compared to uninoculated control. In addition, inoculation of orchardgrass with A. chroococcum strain A1, as well as co-inoculation with B. megaterium and A. chroococcum A1 or A31, significantly increased SDW (51-59%) and total N (54-59%), P (51-74%) and K (49-55%) contents, compared to uninoculated control. Nitrogen percentage in SDW was slightly higher than sufficiency ranges, while K percentage was optimal in all treatments in both species. Phosphorous percentage was lower than sufficiency ranges as a consequence of very low soil P content. The results emphasize the potential of particular rhizobacteria to improve the growth of forage grasses

Poboljšanje rasta lucerke, Medicago sativa L. - pomoću inokulacije preduseva rizosfernim bakterijama

In the greenhouse experiment, the possibility of alfalfa (Medicago sativa L.) growth promotion by inoculation of preceding barley (Hordeum vulgare L.), with plant growth promoting rhizobacteria (PGPR) was examined. The aim of experiment was to select the effective strains as biofertilizer applied in plant rotation. Effects of inoculation with two Azotobacter and two Pseudomonas strains as well as one Sinorhizobium, Enterobacter and Bacillus strain on shoot dry weight and total N content of alfalfa were determined. The results pointed out significant plant growth promotion abilities of strains A1, A2 and P1 which increased alfalfa shoot dry weight over untreated control Ø, by 41, 39 and 35 %, respectively. These three strains increased total N content of alfalfa plants by 34.92 - 40.45% in respect to control Ø. The presented study showed a significant positive influence of preceding barley inoculation with rhizobacteria alone and their mixture on shoot yield and total N content of alfalfa. Results indicated that strains of Azotobacter sp., Pseudomonas sp. and Enterobacter sp. alone can be investigated in further researches as potential agents of biofertilizer for plant growth promotion of alfalfa.U eksprimentu u sudovima ispitana je mogućnost poboljšanja rasta lucerke (Medicago sativa L.) pomoću inokulacije ječma (Hordeum vulgare L.) kao preduseva bakterijama koje poboljšavaju rast biljaka (PGPR). Cilj eksperimenta je bio odabiranje efikasnih sojeva koji bi se primenili u plodoredu u formi biološkog đubriva. U radu je korišćeno sedam sojeva koji pripadaju sledećim bakterijskim vrstama: Sinorhizobium meliloti, Bacillus megaterium, Enterobacter sp, Azotobacter sp, kao i vrsti Pseudomonas sp. Efekat inokulacije ječma primenjenim sojevima je određen na osnovu suve nadzemne mase (SDW) i sadržaja ukupnog azota (N) u biljnoj masi lucerke. Rezultati su ukazali na sposobnost nekih sojeva da poboljšaju rast biljaka. Značajno je povećan prinos lucerke u odnosu na kontrolu Ø (lucerka gajena posle neinokulisanog ječma kao preduseva) inokulacijom sojevima Azotobacter-a A1 (41%) i A2 (39%) i Pseudomonas-a P1 (35%). Sadržaj ukupnog N je bio u korelaciji sa vrednostima SDW. Rezultati su ukazali na uticaj inokulacije ječma kao preduseva na prinos lucerke i njen kvalitet kao i da sojevi Azotobacter sp., Pseudomonas sp. i Enterobacter sp. imaju PGPR potencijal što daje osnovu za dalja ispitivanja i mogućnost primene kao bio­đubriva

Influence of plant growth promoting rhizobacteria on alfalfa, medicago sativa l. yield by inoculation of a preceding italian ryegrass, lolium multiflorum lam

This study was conducted to test the hypothesis that plant growth promoting rhizobacteria (PGPR) can promote the growth of Italian ryegrass, Lolium multiflorum Lam. as well as the growth and nodulation of subsequent alfalfa, Medicago sativa L. In a pot experiment, the influence of PGPR on yield and nitrogen content of Italian ryegrass and alfalfa was studied with the aim to improve their growth and provide effective alfalfa nitrogen fixation under unfavourable soil conditions. Plants were inoculated with seven strains belonging to Sinorhizobium meliloti, Azotobacter spp. and Enterobacter sp.Abeneficial effect on yield and N-assimilation in Italian ryegrass was obtained due to the inoculation of the plants with Azotobacter vinelandii and some Sinorhizobium meliloti strains. In addition, Italian ryegrass seed inoculation with particular rhizobial strains the year before alfalfa growing provided abundant nodulation and better growth of alfalfa

Differences in symbiotic N-2 fixation of alfalfa, Medicago sativa L. cultivars and Sinorhizobium spp. strains in field conditions

In a two-year field trial, four alfalfa cultivars grown in all combinations with five strains of Sinorhizobium spp. were assessed for N-2-fixing potential and compatibility of symbionts with the aim to co-select plant and rhizobia as alternative approach to symbiotic N-2 fixation improvement. It was found that rhizobial strains, host cultivars and interactions between them had a highly significant effects on shoot dry weight (SDW), total and fixed N content of alfalfa. A significant variation in N-2 fixation effectiveness of rhizobial strains, from ineffective to significantly effective depending on cultivars and year of utilization was detected. Effective strains increased SDW by 49-114% (2010) and 35-86% (2011). In the first year the highest effectiveness had strain L5 with cultivars K-28 and BL-88 and strain L3Si with BL-88 while in the following year all applied strains were effective with different extent. Only one strain (L5) was effective with most of alfalfa cultivars over a two-year period. Percentage of N-2 fixed in plant mass for strain L5 was 33% in 2010, and 38% in 2011. In addition, one cultivar (BL-88) was identified to have superior symbiotic performances, exhibiting its high capacity for N-2 fixation. Results indicate that simultaneous selection of both symbionts should be applied for improvement of N-2 fixation in alfalfa

Differences in symbiotic N2 fixation of alfalfa, medicago sativa L. cultivars and Sinorhizobium spp. strains in field conditions

In a two-year field trial, four alfalfa cultivars grown in all combinations with five strains of Sinorhizobium spp. were assessed for N2-fixing potential and compatibility of symbionts with the aim to co-select plant and rhizobia as alternative approach to symbiotic N2 fixation improvement. It was found that rhizobial strains, host cultivars and interactions between them had a highly significant effects on shoot dry weight (SDW), total and fixed N content of alfalfa. A significant variation in N2 fixation effectiveness of rhizobial strains, from ineffective to significantly effective depending on cultivars and year of utilization was detected. Effective strains increased SDW by 49-114% (2010) and 35-86% (2011). In the first year the highest effectiveness had strain L5 with cultivars K-28 and BL-88 and strain L3Si with BL-88 while in the following year all applied strains were effective with different extent. Only one strain (L5) was effective with most of alfalfa cultivars over a two-year period. Percentage of N2 fixed in plant mass for strain L5 was 33% in 2010, and 38% in 2011. In addition, one cultivar (BL-88) was identified to have superior symbiotic performances, exhibiting its high capacity for N2 fixation. Results indicate that simultaneous selection of both symbionts should be applied for improvement of N2 fixation in alfalfa

Nodulation and N2 fixation effectiveness of Bradyrhizobium strains in symbiosis with Adzuki Bean, Vigna angularis

In pot experiment, one isolate Knj from a Serbian soil, four strains of Bradyrhizobium japonicum and three strains of Bradyrhizobium spp. were examined for the effect on adzuki bean nodulation and effectiveness in symbiotic N2 fixation. All the tested strains produced root nodules in adzuki bean. Strains of B. japonicum showed high potential of N2 fixation, particularly 525 and 542. B. japonicum strains resulted 65-71% shoot dry weight and 99-138% total N content of uninoculated control with full N content (100%). No significant difference was found between the plants inoculated with Bradyrhizobium spp. strains and uninoculated control plants without N (40-42 and 42% shoot dry weight, respectively), which indicated symbiotic N2 fixation inactivity of the Bradyrhizobium spp. strains. Knj strain had the middle position (56% shoot dry weight). These data showed that B. japonicum 525 and 542 strains could be used in further investigations in order to apply them as inoculants in microbiological N fertilizers